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Default Heat conduction from basement to earth/soil below

Hi

I have a basement in my house. The floor is about 1.5m below
earth/ground level and it is concrete about 30cm thick

The floor is not insolated, so in order to save some money on the
heating bill I am considering insolating it with sheets of polystyrene
foam (in principle foam filled with air) with some rafters in a mesh to

lay the wooden floor on. The lastly add 20mm of wooden plates/floor

An architect has told me to break up the floor and lay a new one with
30cm of extra insolation

But, I wonder if any of you guys can help me. I am an electrical
engineer and I don't like to do this without calculating the needed
insolation instead.

My theory is that since the floor is 1.5m below ground level, the
temperature of the soil will never be very cold. Searching the net I
find something about 14degree celcius.

So if I have 60square meters of floor heated to room temperature of
20degrees, how do I calculate the heattransfer when I have the data for

the insulation and the concrete floor?

Will the earth behave as an ideal giant block that has 6degrees of
tempeature. So the gradient from the room temperature to the earth can
never be higher than 10 degrees (20-14)?

Numbers:

Concrete, k = ~1W/mK
Polystyrene, k = 0.03W/mK
Wood, k = 0.14W/mK

Power needed to keep temperature stable: P=KAT/D

Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P =
1.2kW

Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W

The poystyrene is in parallel with the rafters. Assuming the rafters
take up 5% of the floor instead of the polystyrene

P= 0.14*60*0.05*6/0.05 = 50W

So from these calculations it seems I need 250W to keep the room heated

(not counting the walls)

Any wrong doings in the calculations - comments?

Thanks

Klaus Kragelund

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Default Heat conduction from basement to earth/soil below

Klaus Kragelund wrote:
Hi

I have a basement in my house. The floor is about 1.5m below
earth/ground level and it is concrete about 30cm thick

The floor is not insolated, so in order to save some money on the
heating bill I am considering insolating it with sheets of polystyrene
foam (in principle foam filled with air) with some rafters in a mesh
to

lay the wooden floor on. The lastly add 20mm of wooden plates/floor

An architect has told me to break up the floor and lay a new one with
30cm of extra insolation

But, I wonder if any of you guys can help me. I am an electrical
engineer and I don't like to do this without calculating the needed
insolation instead.

My theory is that since the floor is 1.5m below ground level, the
temperature of the soil will never be very cold. Searching the net I
find something about 14degree celcius.

So if I have 60square meters of floor heated to room temperature of
20degrees, how do I calculate the heattransfer when I have the data
for

the insulation and the concrete floor?

Will the earth behave as an ideal giant block that has 6degrees of
tempeature. So the gradient from the room temperature to the earth can
never be higher than 10 degrees (20-14)?

Numbers:

Concrete, k = ~1W/mK
Polystyrene, k = 0.03W/mK
Wood, k = 0.14W/mK

Power needed to keep temperature stable: P=KAT/D

Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P =
1.2kW

Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W

The poystyrene is in parallel with the rafters. Assuming the rafters
take up 5% of the floor instead of the polystyrene

P= 0.14*60*0.05*6/0.05 = 50W

So from these calculations it seems I need 250W to keep the room
heated

(not counting the walls)

Any wrong doings in the calculations - comments?

Thanks

Klaus Kragelund


Well, 1.5 meters is about the break even point for your question. So I
would suggest worrying about the wall, but not the floor. However if you
have long cold winters or long hot summers, then you might want to also work
on the floor.

--
Joseph Meehan

Dia duit


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Default Heat conduction from basement to earth/soil below

Where are you, 14c is fairly warm, I am zone 5 US where the freeze zone,
0c -32f is maybe 3.5ft, I put in 2" or R10 under a new basement floor.
With that small a difference foam pad and carpet might be as good.

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Default Heat conduction from basement to earth/soil below

Klaus Kragelund wrote:

I have a basement in my house. The floor is about 1.5m below
earth/ground level...


Covering the ceiling with foil would give it about US R10, ie 1.76 mK/W,
with E = 0.03 and a Tc = 20 C ceiling temp and a Tf = 14 C floor temp
and a large air gap. This would reduce the radiation from the ceiling
to the floor, es((Tc+273)^4-Tf+273)^4) W/m^2, with s = 5.6697x10^-8
W/m^2-K^4. If the upper foil surface is perfectly clean, with no dust
(you are German, right? :-), this may work even better. The linearized
radiation conductance is 4esTm^3 W/m^2-K, where Tm is the approximate
mean absolute temp.

The floor is not insolated, so in order to save some money on the
heating bill I am considering insolating it with sheets of polystyrene
foam... with some rafters in a mesh to lay the wooden floor on.


The English word is "insulating." InsOlation is sunlight.

My theory is that since the floor is 1.5m below ground level, the
temperature of the soil will never be very cold. Searching the net I
find something about 14degree celcius.


The temperature of the middle of the floor might be about the same as
the yearly average air temperature. The walls and the floor near the walls
might be closer to the average daily outdoor temperature.

So if I have 60square meters of floor heated to room temperature of
20degrees, how do I calculate the heattransfer when I have the data for
the insulation and the concrete floor?


With difficulty :-) The floor surface will probably be cooler than 20 C.
That's good.

Will the earth behave as an ideal giant block that has 6degrees of
tempeature. So the gradient from the room temperature to the earth can
never be higher than 10 degrees (20-14)?


The temperature difference between the room air and the middle of the floor
might be 6 C. Then again, the room air will warm the floor, which has thermal
capacity and resistance to downwards heatflow. Some people estimate soil's
resistance to downward heatflow as US R10, ie 1.76d mK/W. Upward is less,
with evaporation from lower soil layers and condensation above. And moving
water can change this.

Concrete, k = ~1W/mK
Polystyrene, k = 0.03W/mK
Wood, k = 0.14W/mK


Air, k = 0.025 W/mK

Power needed to keep temperature stable: P=KAT/D

Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P = 1.2kW

Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W


Not k = 0.03, as above?

The poystyrene is in parallel with the rafters. Assuming the rafters
take up 5% of the floor instead of the polystyrene

P= 0.14*60*0.05*6/0.05 = 50W

So from these calculations it seems I need 250W to keep the room heated


You might cover the ceiling with foil and cover the walls with thin
foil-faced foamboard over spacers and carpet the floor, with no polystyrene.
Each layer of wall foil adds about US R3, plus the bulk resistance of
the foamboard. If there's no vapor barrier under the concrete, you might
put a layer of plastic film under the carpet.

Nick

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Default US R-values of radiant barriers

Here's one way to estimate the R-value of a radiant barrier based on the air
gap and the emissivities and surface temps and the direction of heatflow from
http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf

10 SCREEN 9:KEY OFFIM HC(18,6)
20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
200 FOR I=1 TO 18'read data table
210 FOR J=1 TO 6
220 READ HC(I,J)
230 NEXT:NEXT
240 T1=105'temperature of surface 1 (F)
250 E1=.03'emissivity of surface 1
260 T2=75'temperature of surface 2 (F)
270 E2=.8'emissivity of surface 2
280 L=2'air gap (valid range: 0.5-3")
290 LI=INT(2*L+.5)'length table index
300 HF=0'heatflow 0-down,1-sideways,2-up
310 E=1/(1/E1+1/E2-1)'effective emittance
320 TM=(T1+T2)/2'mean temp (F)
330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
370 PRINT T1,E1,T2,E2
380 PRINT L,HF,R

T1 (F) E1 T2 (F) E2

105 .03 75 .8

gap heatflow US R-value

2" 0 (down) 7.146456

With more than one space in series (eg double-foil foamboard spaced away
from a basement wall), we can't just add R-values. We only know the overall
temp diff, so we have to iterate to find a solution. It's no surprise that
the FTC prohibits makers from advertising R-values for radiant barriers
to avoid confusing the public.

Nick



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Default Heat conduction from basement to earth/soil below


wrote in message

Covering the ceiling with foil would give it about US R10, ie 1.76 mK/W,
with E = 0.03 and a Tc = 20 C ceiling temp and a Tf = 14 C floor temp
and a large air gap. This would reduce the radiation from the ceiling
to the floor, es((Tc+273)^4-Tf+273)^4) W/m^2, with s = 5.6697x10^-8
W/m^2-K^4. If the upper foil surface is perfectly clean, with no dust
(you are German, right? :-), this may work even better. The linearized
radiation conductance is 4esTm^3 W/m^2-K, where Tm is the approximate
mean absolute temp.


Su, what the **** does all that gibberish mean? Oh, I know, it means Nick
can show off he knows a couple of equations and has a calculator. So,
rather than impress us with all of your learning, why not take the time to
explain if this is good or bad and translates to dollars (or Euros) saved.

Yes, that closed cell EPS will be a good insulator.


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Default US R-values of radiant barriers

Yea nick well if you were correct foil faced foamboard both sides would
not have the R rating it has, which is verified, it would be R6 more.
Foil is a Radiant barrier only, it has no R value to speak of, or gee,
wouldn`t the big manufacturers like to be as smart like you and
capitalise on extra performance.

Nick you should go into business, mortage everything, buy 1"
Polyisocyanurate foilfaced foamoard and add R6 to the rating to tell
everyone its R13.2 and sell it, and see what Gov agencys come knocking
to make you prove it.

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Default Heat conduction from basement to earth/soil below

Gibberish is right, "Covering the ceiling with foil gives you R10"
Covering nick with foil and putting him in " Nicks Lightbulb Sauna"
[easybake oven] of previous fame, for a month would do it, or maybe he
just got out of his Easy Bake Oven [sauna].

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Default US R-values of radiant barriers

wrote:

Here's one way to estimate the R-value of a radiant barrier based on the air
gap and the emissivities and surface temps and the direction of heatflow from
http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf

Nick,

How does this work out for the double bubble?

URL: http://www.blueridgecompany.com/radi...ic/189#pricing

It seems to me there are two ways to go for the underfloor insulation
for staple up radiant.

One is foil backed fiberglass insulation with an airspace. That is hard
to find! The other would be double bubble stapled on the joists. It
seems to me that would minimize heat loss through the joists themselves
as they would be uninsulated elsewise. Any thoughts?

Jeff

10 SCREEN 9:KEY OFFIM HC(18,6)
20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
200 FOR I=1 TO 18'read data table
210 FOR J=1 TO 6
220 READ HC(I,J)
230 NEXT:NEXT
240 T1=105'temperature of surface 1 (F)
250 E1=.03'emissivity of surface 1
260 T2=75'temperature of surface 2 (F)
270 E2=.8'emissivity of surface 2
280 L=2'air gap (valid range: 0.5-3")
290 LI=INT(2*L+.5)'length table index
300 HF=0'heatflow 0-down,1-sideways,2-up
310 E=1/(1/E1+1/E2-1)'effective emittance
320 TM=(T1+T2)/2'mean temp (F)
330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
370 PRINT T1,E1,T2,E2
380 PRINT L,HF,R

T1 (F) E1 T2 (F) E2

105 .03 75 .8

gap heatflow US R-value

2" 0 (down) 7.146456

With more than one space in series (eg double-foil foamboard spaced away
from a basement wall), we can't just add R-values. We only know the overall
temp diff, so we have to iterate to find a solution. It's no surprise that
the FTC prohibits makers from advertising R-values for radiant barriers
to avoid confusing the public.

Nick

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Default Heat conduction from basement to earth/soil below


wrote:
Klaus Kragelund wrote:

I have a basement in my house. The floor is about 1.5m below
earth/ground level...


Covering the ceiling with foil would give it about US R10, ie 1.76 mK/W,
with E = 0.03 and a Tc = 20 C ceiling temp and a Tf = 14 C floor temp
and a large air gap. This would reduce the radiation from the ceiling
to the floor, es((Tc+273)^4-Tf+273)^4) W/m^2, with s = 5.6697x10^-8
W/m^2-K^4. If the upper foil surface is perfectly clean, with no dust
(you are German, right? :-), this may work even better. The linearized
radiation conductance is 4esTm^3 W/m^2-K, where Tm is the approximate
mean absolute temp.

The floor is not insolated, so in order to save some money on the
heating bill I am considering insolating it with sheets of polystyrene
foam... with some rafters in a mesh to lay the wooden floor on.


The English word is "insulating." InsOlation is sunlight.

My theory is that since the floor is 1.5m below ground level, the
temperature of the soil will never be very cold. Searching the net I
find something about 14degree celcius.


The temperature of the middle of the floor might be about the same as
the yearly average air temperature. The walls and the floor near the walls
might be closer to the average daily outdoor temperature.

So if I have 60square meters of floor heated to room temperature of
20degrees, how do I calculate the heattransfer when I have the data for
the insulation and the concrete floor?


With difficulty :-) The floor surface will probably be cooler than 20 C.
That's good.

Will the earth behave as an ideal giant block that has 6degrees of
tempeature. So the gradient from the room temperature to the earth can
never be higher than 10 degrees (20-14)?


The temperature difference between the room air and the middle of the floor
might be 6 C. Then again, the room air will warm the floor, which has thermal
capacity and resistance to downwards heatflow. Some people estimate soil's
resistance to downward heatflow as US R10, ie 1.76d mK/W. Upward is less,
with evaporation from lower soil layers and condensation above. And moving
water can change this.

Concrete, k = ~1W/mK
Polystyrene, k = 0.03W/mK
Wood, k = 0.14W/mK


Air, k = 0.025 W/mK

Power needed to keep temperature stable: P=KAT/D

Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P = 1.2kW

Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W


Not k = 0.03, as above?

The poystyrene is in parallel with the rafters. Assuming the rafters
take up 5% of the floor instead of the polystyrene

P= 0.14*60*0.05*6/0.05 = 50W

So from these calculations it seems I need 250W to keep the room heated


You might cover the ceiling with foil and cover the walls with thin
foil-faced foamboard over spacers and carpet the floor, with no polystyrene.
Each layer of wall foil adds about US R3, plus the bulk resistance of
the foamboard. If there's no vapor barrier under the concrete, you might
put a layer of plastic film under the carpet.

Thankyou for the very good points

The basement is going to be used for office, so it will be heated all
year round.

I should have said I'm situated in Denmark (just north of Germany :-)

Perhaps then my number of 6 degrees gradient is overly optimistic due
to fringe effects near the outer walls. I want as little insulation as
possible since adding too much to the floor will limit the height of
the doors.

Currently no mostiture film is used. I want to add a wooden floor with
a carpet on top of this. The basement is dry, but my intention was to
add ventilation holes in the wooden floor and use no platic film to
allow the construction to"breathe". But adding plastic film might be a
good idea since this also limits heat flow caused by travelling
moisture.

Thanks

Klaus



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Default US R-values of radiant barriers

Jeff wrote:

... one way to estimate the R-value of a radiant barrier based on the air
gap and the emissivities and surface temps and the direction of heatflow
from http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf


How does this work out for the double bubble?


Haven't tried that. You might work it out, if you know the gap width, etc.

http://www.blueridgecompany.com/radi...ic/189#pricing

It seems to me there are two ways to go for the underfloor insulation
for staple up radiant.

One is foil backed fiberglass insulation with an airspace. That is hard
to find! The other would be double bubble stapled on the joists. It
seems to me that would minimize heat loss through the joists themselves
as they would be uninsulated elsewise. Any thoughts?


I would staple on foil or thin double-foil foamboard.

Nick

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Default Heat conduction from basement to earth/soil below

Edwin Pawlowski wrote:

wrote:

Covering the ceiling with foil would give it about US R10, ie 1.76 mK/W,
with E = 0.03 and a Tc = 20 C ceiling temp and a Tf = 14 C floor temp
and a large air gap. This would reduce the radiation from the ceiling
to the floor, es((Tc+273)^4-Tf+273)^4) W/m^2, with s = 5.6697x10^-8
W/m^2-K^4. If the upper foil surface is perfectly clean, with no dust
(you are German, right? :-), this may work even better. The linearized
radiation conductance is 4esTm^3 W/m^2-K, where Tm is the approximate
mean absolute temp.


Su, what the **** does all that gibberish mean?


That's called "elementary engineering" :-) The OP Klaus is an engineer.

Nick

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Default US R-values of radiant barriers

m Ransley errs again:

... if you were correct foil faced foamboard both sides would
not have the R rating it has.


Nope. FTC rules mostly prohibit advertising installed R-values
to avoid confusing people smarter than you :-)

Nick

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Default Heat conduction from basement to earth/soil below

Klaus Kragelund wrote:

Thankyou for the very good points


You are welcome.

I should have said I'm situated in Denmark (just north of Germany :-)


Danish people might permit a tiny amount of dust on the upper foil.
Then again, they build airtight houses, so excess moisture could be
a problem in summertime.

Currently no mostiture film is used. I want to add a wooden floor with
a carpet on top of this.


You may not need the wood.

The basement is dry, but my intention was to add ventilation holes in
the wooden floor and use no platic film to allow the construction to
"breathe". But adding plastic film might be a good idea since this also
limits heat flow caused by travelling moisture.


Upwards heatflow could be nice in wintertime.

Nick

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Default US R-values of radiant barriers


wrote in message
...

Here's one way to estimate the R-value
of a radiant barrier based on the air
gap and the emissivities and surface
temps and the direction of heatflow from


It is?

The British Advertising Standards Authority got Actis, a French company,
claiming their reflective foil insulation is 'Equivalent to 200mm of
traditional Rockwoool insulation'. A complaint has been upheld after ASA
went to independent technical experts.

The judgement can be seen at:
http://tinyurl.com/s6c2p

Think hard before you buy.



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Default US R-values of radiant barriers

News wrote:

wrote in message
...

Here's one way to estimate the R-value of a radiant barrier based on
the air
gap and the emissivities and surface temps and the direction of
heatflow from
http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf

10 SCREEN 9:KEY OFFIM HC(18,6)
20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
200 FOR I=1 TO 18'read data table
210 FOR J=1 TO 6
220 READ HC(I,J)
230 NEXT:NEXT
240 T1=105'temperature of surface 1 (F)
250 E1=.03'emissivity of surface 1
260 T2=75'temperature of surface 2 (F)
270 E2=.8'emissivity of surface 2
280 L=2'air gap (valid range: 0.5-3")
290 LI=INT(2*L+.5)'length table index
300 HF=0'heatflow 0-down,1-sideways,2-up
310 E=1/(1/E1+1/E2-1)'effective emittance
320 TM=(T1+T2)/2'mean temp (F)
330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
370 PRINT T1,E1,T2,E2
380 PRINT L,HF,R

T1 (F) E1 T2 (F) E2

105 .03 75 .8

gap heatflow US R-value

2" 0 (down) 7.146456

With more than one space in series (eg double-foil foamboard spaced away
from a basement wall), we can't just add R-values. We only know the
overall
temp diff, so we have to iterate to find a solution. It's no surprise
that
the FTC prohibits makers from advertising R-values for radiant barriers
to avoid confusing the public.

Nick



Rockwool has a set value and can be compounded. Makers claim all sorts
of wild claim for radiant barriers. To bottom line, what is it the
equivalent to in rockwool in thickness?


I think that is exactly what Nick has done. But remember fiberglass
blankets are temperature independant (mostly). Radiant barriers are
dependant on the temperature (emisivity is T^3) and the air space can be
treated as a more conventional "R" value. Note that Nick has commented
the code.

Run that for a higher delta temp and you will get a higher R, just a
lower delta temp gives a lower.

Jeff


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"Jeff" wrote in message
ink.net...
News wrote:

wrote in message
...

Here's one way to estimate the R-value of a radiant barrier based on the
air
gap and the emissivities and surface temps and the direction of heatflow
from
http://www.reflectixinc.com/pdf/RIMA_Handbook.pdf

10 SCREEN 9:KEY OFFIM HC(18,6)
20 DATA 0.359,0.184,0.126,0.097,0.080,0.068
30 DATA 0.361,0.187,0.129,0.100,0.082,0.072
40 DATA 0.363,0.189,0.131,0.101,0.085,0.075
50 DATA 0.364,0.190,0.132,0.103,0.087,0.078
60 DATA 0.365,0.191,0.133,0.105,0.090,0.081
70 DATA 0.366,0.192,0.134,0.106,0.092,0.082
80 DATA 0.360,0.204,0.169,0.179,0.185,0.189
90 DATA 0.366,0.267,0.223,0.233,0.238,0.241
100 DATA 0.373,0.247,0.261,0.271,0.275,0.276
110 DATA 0.380,0.270,0.292,0.301,0.303,0.303
120 DATA 0.387,0.296,0.317,0.325,0.327,0.326
130 DATA 0.394,0.319,0.339,0.347,0.347,0.345
140 DATA 0.381,0.312,0.295,0.284,0.275,0.268
150 DATA 0.429,0.381,0.360,0.346,0.336,0.328
160 DATA 0.472,0.428,0.405,0.389,0.377,0.368
170 DATA 0.511,0.465,0.440,0.423,0.410,0.400
180 DATA 0.545,0.496,0.469,0.451,0.437,0.426
190 DATA 0.574,0.523,0.494,0.475,0.460,0.449
200 FOR I=1 TO 18'read data table
210 FOR J=1 TO 6
220 READ HC(I,J)
230 NEXT:NEXT
240 T1=105'temperature of surface 1 (F)
250 E1=.03'emissivity of surface 1
260 T2=75'temperature of surface 2 (F)
270 E2=.8'emissivity of surface 2
280 L=2'air gap (valid range: 0.5-3")
290 LI=INT(2*L+.5)'length table index
300 HF=0'heatflow 0-down,1-sideways,2-up
310 E=1/(1/E1+1/E2-1)'effective emittance
320 TM=(T1+T2)/2'mean temp (F)
330 DT=ABS(T1-T2)'temp diff (valid range: 5-30 F)
340 DTI=INT(DT/5+.5+6*HF)'temp diff table index
350 HR=.00686*((TM+459.7)/100)^3'radiant conductance
360 R=1/(E*HR+HC(DTI,LI))'US R-value (ft^2-F-h/Btu)
370 PRINT T1,E1,T2,E2
380 PRINT L,HF,R

T1 (F) E1 T2 (F) E2

105 .03 75 .8

gap heatflow US R-value

2" 0 (down) 7.146456

With more than one space in series (eg double-foil foamboard spaced away
from a basement wall), we can't just add R-values. We only know the
overall
temp diff, so we have to iterate to find a solution. It's no surprise
that
the FTC prohibits makers from advertising R-values for radiant barriers
to avoid confusing the public.

Nick



Rockwool has a set value and can be compounded. Makers claim all sorts
of wild claim for radiant barriers. To bottom line, what is it the
equivalent to in rockwool in thickness?


I think that is exactly what Nick has done. But remember fiberglass
blankets are temperature independant (mostly). Radiant barriers are
dependant on the temperature (emisivity is T^3) and the air space can be
treated as a more conventional "R" value. Note that Nick has commented the
code.

Run that for a higher delta temp and you will get a higher R, just a lower
delta temp gives a lower.


I am very sceptical of these barriers. What they need to do is have two
identical houses in the same place, one with the barrier and one with
rockwool. Then do data monitoring for a year or more. The British ASA
ruled against Actis, a French maker, as the tests were not good enough.
There is no testing model to explain. After all this time you would have
thought they could have done tests on an Actis Triso9 house and an identical
house without Actis with 200mm of insulation in the walls. If there was a
clear difference I'm sure they would be crowing from the rooftops with all
data printed and freely given out at every bus stop.

This stuff is not cheap. As far as I can see it is expensive bubble wrap -
until proper meaningful realistic independent tests have been undertaken.

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Default US R-values of radiant barriers

News wrote:

The British Advertising Standards Authority... [objected to] a brochure
for roof insulation. The brochure stated "TRI-ISO SUPER 9 Insulation for
roofs was... Thermally equivalent to 200 mm of mineral wool when installed
in a roof situation, as certified by the European certifying body, BM TRADA
CERTIFICATION (following real building trials...


... Actis said they had commissioned BM TRADA Certification Ltd (BM TRADA)
to test, assess and report on the TRI-ISO Super 9 product. They provided us
with a copy of the BM TRADA Certification and Report dated August 1997 and
said that it substantiated their claims... They pointed out that BM TRADA
had used "in situ" testing involving a real external environment with
variations in temperature, humidity, etc. rather than the traditional
methods of laboratory testing...


... We understood that BM TRADA had tested TRI-ISO SUPER 9 and the mineral
wool in two separate roof installations. However, we noted that BM TRADA
had not used the standard industry methods of testing and that the report
provided by Actis did not include sufficient detail to support their own
methods of testing.

We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology...


.... ie they faulted the test documentation, vs the result.

We understood that RT was a symbol of total thermal resistance and typically
had the standard unit of measurement of mēK/W. We noted that the claim
"RT=5" was not qualified by any recognised units of measurement e.g. mēK/W
and a small footnote stated only "in situ measured values" without further
explanation. Because the value of 5 was not qualified by any recognised
units of measurement, we considered the claim "RT=5" was ambiguous and
should be qualified in future.


.... and they faulted the lack of explicit units in the advertised result.

However, we noted that the BM TRADA report did specify an overall resistance
(RT) of 5.0mēK/W derived from the in situ testing...


Picky, picky. Reflectix does advertise some system R-values:

http://www.reflectixinc.com/script/p...duct.asp?ID=64
http://www.reflectixinc.com/script/p...duct.asp?ID=77
http://www.majorgeothermal.com/PDFs/.../Solutions.pdf

The US R16.8 crawl space number is interesting.

Nick

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Default US R-values of radiant barriers


wrote in message
...
News wrote:

The British Advertising Standards Authority... [objected to] a brochure
for roof insulation. The brochure stated "TRI-ISO SUPER 9 Insulation for
roofs was... Thermally equivalent to 200 mm of mineral wool when installed
in a roof situation, as certified by the European certifying body, BM
TRADA
CERTIFICATION (following real building trials...


... Actis said they had commissioned BM TRADA Certification Ltd (BM TRADA)
to test, assess and report on the TRI-ISO Super 9 product. They provided
us
with a copy of the BM TRADA Certification and Report dated August 1997 and
said that it substantiated their claims... They pointed out that BM TRADA
had used "in situ" testing involving a real external environment with
variations in temperature, humidity, etc. rather than the traditional
methods of laboratory testing...


... We understood that BM TRADA had tested TRI-ISO SUPER 9 and the mineral
wool in two separate roof installations. However, we noted that BM TRADA
had not used the standard industry methods of testing and that the report
provided by Actis did not include sufficient detail to support their own
methods of testing.

We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology...


... ie they faulted the test documentation, vs the result.

We understood that RT was a symbol of total thermal resistance and
typically
had the standard unit of measurement of mēK/W. We noted that the claim
"RT=5" was not qualified by any recognised units of measurement e.g. mēK/W
and a small footnote stated only "in situ measured values" without further
explanation. Because the value of 5 was not qualified by any recognised
units of measurement, we considered the claim "RT=5" was ambiguous and
should be qualified in future.


... and they faulted the lack of explicit units in the advertised result.

However, we noted that the BM TRADA report did specify an overall
resistance
(RT) of 5.0mēK/W derived from the in situ testing...


Picky, picky. Reflectix does advertise some system R-values:

http://www.reflectixinc.com/script/p...duct.asp?ID=64
http://www.reflectixinc.com/script/p...duct.asp?ID=77
http://www.majorgeothermal.com/PDFs/.../Solutions.pdf

The US R16.8 crawl space number is interesting.


An important question here is how does other insulation perform 'in-situ' if
measured the same way as this product.

If this product can achieve an RT=5 'in situ', that means the overall
measured insulative performance is 5 m^2-K/W. That performance includes the
affects of convection and radiant heat transfer from the living space to the
product, and from the product to the environs on the other side.

But what is deceptive about this, is that if I were to put a simple piece of
conventional building insulation that has an RT=5 value in the same
circumstance, it would undoubtedly have an 'in situ' performance that is
*better* than 5. Because added to the material's own RT=5, would also be
the affects of the convective layers on each side (just like this product),
and the radiant transfer to/from the surfaces.

Unless this products RT value is calculated by taking the 'in-situ'
performance and *subtracting* the insulative performance of those items
common to *all* installations, the RT value is inflated by those other
factors. Thus when compared with other materials tested in the more
traditional manner, it overstates this product's performance.

daestrom

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Default US R-values of radiant barriers


wrote in message
...
News wrote:

The British Advertising Standards Authority... [objected to] a brochure
for roof insulation. The brochure stated "TRI-ISO SUPER 9 Insulation for
roofs was... Thermally equivalent to 200 mm of mineral wool when installed
in a roof situation, as certified by the European certifying body, BM
TRADA
CERTIFICATION (following real building trials...


... Actis said they had commissioned BM TRADA Certification Ltd (BM TRADA)
to test, assess and report on the TRI-ISO Super 9 product. They provided
us
with a copy of the BM TRADA Certification and Report dated August 1997 and
said that it substantiated their claims... They pointed out that BM TRADA
had used "in situ" testing involving a real external environment with
variations in temperature, humidity, etc. rather than the traditional
methods of laboratory testing...


... We understood that BM TRADA had tested TRI-ISO SUPER 9 and the mineral
wool in two separate roof installations. However, we noted that BM TRADA
had not used the standard industry methods of testing and that the report
provided by Actis did not include sufficient detail to support their own
methods of testing.

We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology...


... ie they faulted the test documentation, vs the result.

We understood that RT was a symbol of total thermal resistance and
typically
had the standard unit of measurement of mēK/W. We noted that the claim
"RT=5" was not qualified by any recognised units of measurement e.g. mēK/W
and a small footnote stated only "in situ measured values" without further
explanation. Because the value of 5 was not qualified by any recognised
units of measurement, we considered the claim "RT=5" was ambiguous and
should be qualified in future.


... and they faulted the lack of explicit units in the advertised result.

However, we noted that the BM TRADA report did specify an overall
resistance
(RT) of 5.0mēK/W derived from the in situ testing...


Picky, picky. Reflectix does advertise some system R-values:

http://www.reflectixinc.com/script/p...duct.asp?ID=64
http://www.reflectixinc.com/script/p...duct.asp?ID=77
http://www.majorgeothermal.com/PDFs/.../Solutions.pdf

The US R16.8 crawl space number is interesting.

Nick


They now have TRI-ISO SUPER 10, not 9, so this judgement againast them
doesn't stand anymore. They still state that it is equiv to 210mm of
mineral wool.
http://www.tri-isosuper10.co.uk/tri-iso_super_10_thermal_insulator_test_data.htm

I might put a complaint in.





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Default US R-values of radiant barriers

daestrom wrote:

However, we noted that the BM TRADA report did specify an overall
resistance RT) of 5.0mēK/W derived from the in situ testing...


Unless this products RT value is calculated by taking the 'in-situ'
performance and *subtracting* the insulative performance of those items
common to *all* installations, the RT value is inflated by those other factors.


In this case, one would hope they derived by subtracting. Nobody seems
to have disputed the result that it worked as well as the rock wool did.

... Reflectix does advertise some system R-values:

http://www.reflectixinc.com/script/p...duct.asp?ID=64
http://www.reflectixinc.com/script/p...duct.asp?ID=77
http://www.majorgeothermal.com/PDFs/.../Solutions.pdf

The US R16.8 crawl space number is interesting.


That number includes the other stuff, as the FTC-mandated "system R-value,"
with a substantial contribution from the foil surface. A non-radiant maker
could also legally advertise a system R-value in the US.

Nick

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Default US R-values of radiant barriers

daestrom wrote:

wrote in message
...

News wrote:

The British Advertising Standards Authority... [objected to] a brochure
for roof insulation. The brochure stated "TRI-ISO SUPER 9 Insulation for
roofs was... Thermally equivalent to 200 mm of mineral wool when
installed
in a roof situation, as certified by the European certifying body, BM
TRADA
CERTIFICATION (following real building trials...



... Actis said they had commissioned BM TRADA Certification Ltd (BM
TRADA)
to test, assess and report on the TRI-ISO Super 9 product. They
provided us
with a copy of the BM TRADA Certification and Report dated August
1997 and
said that it substantiated their claims... They pointed out that BM
TRADA
had used "in situ" testing involving a real external environment with
variations in temperature, humidity, etc. rather than the traditional
methods of laboratory testing...



... We understood that BM TRADA had tested TRI-ISO SUPER 9 and the
mineral
wool in two separate roof installations. However, we noted that BM TRADA
had not used the standard industry methods of testing and that the
report
provided by Actis did not include sufficient detail to support their own
methods of testing.

We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation
Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology...



... ie they faulted the test documentation, vs the result.

We understood that RT was a symbol of total thermal resistance and
typically
had the standard unit of measurement of mēK/W. We noted that the claim
"RT=5" was not qualified by any recognised units of measurement e.g.
mēK/W
and a small footnote stated only "in situ measured values" without
further
explanation. Because the value of 5 was not qualified by any recognised
units of measurement, we considered the claim "RT=5" was ambiguous and
should be qualified in future.



... and they faulted the lack of explicit units in the advertised result.

However, we noted that the BM TRADA report did specify an overall
resistance
(RT) of 5.0mēK/W derived from the in situ testing...



Picky, picky. Reflectix does advertise some system R-values:

http://www.reflectixinc.com/script/p...duct.asp?ID=64
http://www.reflectixinc.com/script/p...duct.asp?ID=77
http://www.majorgeothermal.com/PDFs/.../Solutions.pdf

The US R16.8 crawl space number is interesting.


An important question here is how does other insulation perform
'in-situ' if measured the same way as this product.

If this product can achieve an RT=5 'in situ', that means the overall
measured insulative performance is 5 m^2-K/W. That performance includes
the affects of convection and radiant heat transfer from the living
space to the product, and from the product to the environs on the other
side.

But what is deceptive about this, is that if I were to put a simple
piece of conventional building insulation that has an RT=5 value in the
same circumstance, it would undoubtedly have an 'in situ' performance
that is *better* than 5.


Conventional insulation would only be between the floor joists. For 2
bys at 16" centers that means that 12.5% of the area is the insulation
value of only the joist. I would think that would be around a US R6 for
a 2 * 6. There will be a point of diminishing returns for conventional
insulation, just because of that. Don't forget that under most floors
you have a maze of plumbing and wiring and that has to be worked around
with conventional insulation.

The more interesting question in my mind, is whether this would be a
good afterfit for an existing structure. It certainly would be easier
(crawl spaces are no fun!) to install and it would be a complete seal.
It seems to me that most energy lost is in existing structures rather
than new construction. The option of tearing down the old house and
building a new does not exist for most people.

I would be delighted to have a US R 16.8 floor in my '20s house. At
this point underfloor radiant with radiant bubble looks attractive, not
sure which way I will go and I'm open to other suggestions (like foil
backed iso).

Jeff


Because added to the material's own RT=5,
would also be the affects of the convective layers on each side (just
like this product), and the radiant transfer to/from the surfaces.

Unless this products RT value is calculated by taking the 'in-situ'
performance and *subtracting* the insulative performance of those items
common to *all* installations, the RT value is inflated by those other
factors. Thus when compared with other materials tested in the more
traditional manner, it overstates this product's performance.

daestrom

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Default US R-values of radiant barriers


....
I am very sceptical of these barriers. What they need to do is have two
identical houses in the same place, one with the barrier and one with
rockwool. Then do data monitoring for a year or more. The British ASA
ruled against Actis, a French maker, as the tests were not good enough.
There is no testing model to explain. After all this time you would have
thought they could have done tests on an Actis Triso9 house and an
identical house without Actis with 200mm of insulation in the walls. If
there was a clear difference I'm sure they would be crowing from the
rooftops with all data printed and freely given out at every bus stop.

This stuff is not cheap. As far as I can see it is expensive bubble
wrap - until proper meaningful realistic independent tests have been
undertaken.


Hi,

The FSEC has done radiant barrier work -- here is one report:
http://www.fsec.ucf.edu/bldg/pubs/rbs/

If you go to their site and search on Radiant Barrier, a lot of stuff comes up.

I think that www.SouthFace.org has also done work on radiant barrier.

These are good and independant outfits -- I would tend to belive what they
publish. It seems like the bottom line turns out to be about 10% saving on cooling.

Gary


--


Gary

www.BuildItSolar.com

"Build It Yourself" Solar Projects









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Default US R-values of radiant barriers


"Gary" wrote in message
...

...
I am very sceptical of these barriers. What they need to do is have two
identical houses in the same place, one with the barrier and one with
rockwool. Then do data monitoring for a year or more. The British ASA
ruled against Actis, a French maker, as the tests were not good enough.
There is no testing model to explain. After all this time you would have
thought they could have done tests on an Actis Triso9 house and an
identical house without Actis with 200mm of insulation in the walls. If
there was a clear difference I'm sure they would be crowing from the
rooftops with all data printed and freely given out at every bus stop.

This stuff is not cheap. As far as I can see it is expensive bubble
wrap - until proper meaningful realistic independent tests have been
undertaken.


Hi,

The FSEC has done radiant barrier work -- here is one report:
http://www.fsec.ucf.edu/bldg/pubs/rbs/


I am aware of that and have previously read it. It is quite old now, 1999.
At the time the performance in cold climates from other non-comprehensive
tests in the USA was not too encouraging.

If you go to their site and search on Radiant Barrier, a lot of stuff
comes up.

I think that www.SouthFace.org has also done work on radiant barrier.

These are good and independant outfits -- I would tend to belive what they
publish. It seems like the bottom line turns out to be about 10% saving
on cooling.

Gary


Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
effect on cooling when pinned to the rafters of a roof. What is the overall
claim for rockwool equivalent thickness for heating by tests in the US?
There must be some ballpark. No one is going to type in Nicks program, they
read the makers blurb, or test results to confirm the blurb.

I have the impression much of any heat saving is because this stuff is
air-tight. More the draught prevention is making the difference rather than
the reflective qualities of the material itself. I hope I am wrong and it
does what they say. If so my attic gets done out in it. Until something
more concrete in realistic more real world testing the jury is still out and
it stays out of my attic. 35C here means I may have to act with the attic by
next summer - but using what has to be determined.

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News wrote:

Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
effect on cooling when pinned to the rafters of a roof. What is the overall
claim for rockwool equivalent thickness for heating by tests in the US?


The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
US R3.62 per inch, at a rock wool density of 10 lb/ft^3.

No one is going to type in Nicks program, they read the makers blurb,
or test results to confirm the blurb.


No need to type much. Just save it in a file, remove the headers, and run it.
Or look at the on-line RIMA Handbook and use a calculator, which takes about
5 minutes.

I have the impression much of any heat saving is because this stuff is
air-tight.


That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
110 F above and 80 below has E = 0.0298 for both airspaces and an overall
dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
iterate if needed, using these new dTs to find new Tms.

More the draught prevention is making the difference rather than
the reflective qualities of the material itself.


No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
IR-transparent polyethylene film, the difference is even greater, even though
there's still draught prevention. OTOH, if we add more foils or move the foil
up so there's only one airspace, that doesn't help much in this case, given
the same overall airspace dimension.

Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.

Until something more concrete in realistic more real world testing the jury
is still out...


Au contraire. This has been settled science for over 50 years :-) See

Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
National Bureau of Standards, Washington DC (1954), and

Yarbrough, "Assessments of Reflective Insulation for Residential and
Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
Oak Ridge, TN (1983), and

Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
Editor (1990) pp 214-231, and

Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
Insulation," Journal of Thermal Insulation 15 137-151, (1991).

Nick



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Nick, you make me want a brain-douche.



On 31 Jul 2006 00:37:34 -0400, wrote:

News wrote:

Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
effect on cooling when pinned to the rafters of a roof. What is the overall
claim for rockwool equivalent thickness for heating by tests in the US?


The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
US R3.62 per inch, at a rock wool density of 10 lb/ft^3.

No one is going to type in Nicks program, they read the makers blurb,
or test results to confirm the blurb.


No need to type much. Just save it in a file, remove the headers, and run it.
Or look at the on-line RIMA Handbook and use a calculator, which takes about
5 minutes.

I have the impression much of any heat saving is because this stuff is
air-tight.


That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
110 F above and 80 below has E = 0.0298 for both airspaces and an overall
dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
iterate if needed, using these new dTs to find new Tms.

More the draught prevention is making the difference rather than
the reflective qualities of the material itself.


No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
IR-transparent polyethylene film, the difference is even greater, even though
there's still draught prevention. OTOH, if we add more foils or move the foil
up so there's only one airspace, that doesn't help much in this case, given
the same overall airspace dimension.

Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.

Until something more concrete in realistic more real world testing the jury
is still out...


Au contraire. This has been settled science for over 50 years :-) See

Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
National Bureau of Standards, Washington DC (1954), and

Yarbrough, "Assessments of Reflective Insulation for Residential and
Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
Oak Ridge, TN (1983), and

Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
Editor (1990) pp 214-231, and

Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
Insulation," Journal of Thermal Insulation 15 137-151, (1991).

Nick


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Default US R-values of radiant barriers

wrote:
News wrote:


Actis claim the equivalent of 210mm of Rockwool. I believe they do have an
effect on cooling when pinned to the rafters of a roof. What is the overall
claim for rockwool equivalent thickness for heating by tests in the US?



The second edition (1998) of Pitts & Sissom's Schaum's Outline on Heat
Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2, ie
US R3.62 per inch, at a rock wool density of 10 lb/ft^3.


No one is going to type in Nicks program, they read the makers blurb,
or test results to confirm the blurb.



No need to type much. Just save it in a file, remove the headers, and run it.
Or look at the on-line RIMA Handbook and use a calculator, which takes about
5 minutes.


I have the impression much of any heat saving is because this stuff is
air-tight.



That's assumed to begin with, but foil helps. For instance, the RIMA Handbook
says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and 2 above
and below the foil with E1 and E4 = 0.8 boundaries and downward heatflow and
110 F above and 80 below has E = 0.0298 for both airspaces and an overall
dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean temp in
airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 = 87.5. From
Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces. Equation 3
on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219 and 1.124.
Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2 = 18.2,
and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We could
iterate if needed, using these new dTs to find new Tms.


More the draught prevention is making the difference rather than
the reflective qualities of the material itself.



No. If we replace the foil above with another E2 = E3 = 0.8 opaque surface,
then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 = 1.026 and
the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the foil with
IR-transparent polyethylene film, the difference is even greater, even though
there's still draught prevention. OTOH, if we add more foils or move the foil
up so there's only one airspace, that doesn't help much in this case, given
the same overall airspace dimension.

Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot more stuff.



From The Passive Solar Energy Handbook, Edward Mazria 1979 we have this
in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.

Jeff



Until something more concrete in realistic more real world testing the jury
is still out...



Au contraire. This has been settled science for over 50 years :-) See

Robinson and F.J. Powell, "The Thermal Insulating Value of Airspaces,"
Housing Research Paper No. 32, National Bureau of Standards Project NE-12,
National Bureau of Standards, Washington DC (1954), and

Yarbrough, "Assessments of Reflective Insulation for Residential and
Commercial Applications," Oak Ridge National Laboratory Report ORNL/TM 8819,
Oak Ridge, TN (1983), and

Yarbrough, "Estimation of the Thermal Resistance of a Series of Reflective
Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings of
the Conference on Fire Safety and Thermal Insulation, S.A. Siddiqui,
Editor (1990) pp 214-231, and

Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack Reflective
Insulation," Journal of Thermal Insulation 15 137-151, (1991).

Nick

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http://www.naturalspacesdomes.com/li...estresults.htm


"Jeff" wrote in message
k.net...
wrote:
News wrote:


Actis claim the equivalent of 210mm of Rockwool. I believe they do
have an effect on cooling when pinned to the rafters of a roof.
What is the overall claim for rockwool equivalent thickness for
heating by tests in the US?



The second edition (1998) of Pitts & Sissom's Schaum's Outline on
Heat
Transfer gives k = 0.023 Btu-ft/h-F-ft^2, ie 0.276 Btu-in-h/F-ft^2,
ie
US R3.62 per inch, at a rock wool density of 10 lb/ft^3.
No one is going to type in Nicks program, they read the makers
blurb,
or test results to confirm the blurb.



No need to type much. Just save it in a file, remove the headers,
and run it.
Or look at the on-line RIMA Handbook and use a calculator, which
takes about
5 minutes.
I have the impression much of any heat saving is because this stuff
is
air-tight.



That's assumed to begin with, but foil helps. For instance, the
RIMA Handbook
says a horizontal foil with E2 and E3 = 0.03 and 3" airspaces 1 and
2 above
and below the foil with E1 and E4 = 0.8 boundaries and downward
heatflow and 110 F above and 80 below has E = 0.0298 for both
airspaces and an overall
dT = 110-80 = 30 F. Assuming the foil is 80+dT/2 = 95 F, the mean
temp in
airspace 1 is Tm1 = (110+95)/2 = 102.5 F, and Tm2 = (95+80)/2 =
87.5. From
Table 4 on page 25 of the Handbook, hc = 0.075 for both airspaces.
Equation 3
on page 22 says hr1 and hr2 = 0.00686((Tm+459.7))/100)^3 = 1.219
and 1.124.
Equation 1 says R1 = 1/(Ehr1+hc) = 8.98 and R2 = 9.22, so R = R1+R2
= 18.2,
and dT1 = 30x8.98/18.2 = 14.8 F and dT2 = 15.2. Close enough. We
could
iterate if needed, using these new dTs to find new Tms.


More the draught prevention is making the difference rather than
the reflective qualities of the material itself.



No. If we replace the foil above with another E2 = E3 = 0.8 opaque
surface,
then E = 0.8 vs 0.0298 for both airspaces, so R1 = 0.952 and R2 =
1.026 and
the overall R = 1.98 vs 18.2, ie 9 TIMES less. If we replace the
foil with
IR-transparent polyethylene film, the difference is even greater,
even though
there's still draught prevention. OTOH, if we add more foils or
move the foil
up so there's only one airspace, that doesn't help much in this
case, given
the same overall airspace dimension.

Rock wool would only add 3.62x6" = US R13.13 vs 18.2, using a lot
more stuff.



From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple
up radiant, is that 8.94 for a single radiant barrier. It sure makes
foil double bubble look good.

Jeff



Until something more concrete in realistic more real world testing
the jury
is still out...



Au contraire. This has been settled science for over 50 years :-)
See

Robinson and F.J. Powell, "The Thermal Insulating Value of
Airspaces,"
Housing Research Paper No. 32, National Bureau of Standards Project
NE-12,
National Bureau of Standards, Washington DC (1954), and Yarbrough,
"Assessments of Reflective Insulation for Residential and
Commercial Applications," Oak Ridge National Laboratory Report
ORNL/TM 8819,
Oak Ridge, TN (1983), and Yarbrough, "Estimation of the Thermal
Resistance of a Series of Reflective
Air Spaces Bounded by Parallel Low Emittance Surfaces," Proceedings
of
the Conference on Fire Safety and Thermal Insulation, S.A.
Siddiqui,
Editor (1990) pp 214-231, and

Yarbrough, "Thermal Resistance of a Air Ducts with Bubblepack
Reflective
Insulation," Journal of Thermal Insulation 15 137-151, (1991).

Nick



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Isn't the reflective surface only effective if there is an air gap
next to it?

I have read some testing reports that show those 3/8" doubvle radiant
barriers under slabs to have a non-measureable difference to no
insultaion at all. ****ed off my concrete guy but I gave him a print
out of the report and now I can't find it again.



"daestrom" wrote in message
...

"Jeff" wrote in message
k.net...
wrote:

snip


From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple
up radiant, is that 8.94 for a single radiant barrier. It sure
makes foil double bubble look good.


One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every
year or so, it will accumulate and lose its effectiveness.

In attics, it's advised to put the radiant barrier on the rafters
overhead so the radiant surface is on the underside. For underfloor
installations, the same thing. The foil goes on the underside to
limit the accumulation of dust that will ruin its effectiveness.

daestrom





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"Solar Flare" wrote in message
...
Isn't the reflective surface only effective if there is an air gap next to
it?


That's my understanding. It reduces the amount of heat transferred across
the air-gap by radiant heat transfer.

Since convection is the larger heat transfer mechanism for heat flow upward
(such as in an attic in a cold climate), they are not as effective when
trying to stop heat loss. So you usually only see them touted in situations
to stop the heat flow downward. Such as a hot attic to an air-conditioned
space, or from a heated room downward to an unheated crawl-space/cellar.

I have read some testing reports that show those 3/8" doubvle radiant
barriers under slabs to have a non-measureable difference to no insultaion
at all. ****ed off my concrete guy but I gave him a print out of the
report and now I can't find it again.


Yeah, putting some other material in direct contact with the foil, such as a
layer of wallboard, or a concrete floor pretty much nullifies the affects of
the foil. Of course, if the foil is over one inch of foam board, you still
have the one inch of foam and its insulation value. But not worth paying
any extra to get the foil.

daestrom

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Do you know what the defined RSI rating means? I have heard so many
definitions that none of them make sense anymore. Many try to equate
it with the R factor unsuccessfully and I believe it has something to
do with "reflective..."

"daestrom" wrote in message
...

"Solar Flare" wrote in message
...
Isn't the reflective surface only effective if there is an air gap
next to it?


That's my understanding. It reduces the amount of heat transferred
across the air-gap by radiant heat transfer.

Since convection is the larger heat transfer mechanism for heat flow
upward (such as in an attic in a cold climate), they are not as
effective when trying to stop heat loss. So you usually only see
them touted in situations to stop the heat flow downward. Such as a
hot attic to an air-conditioned space, or from a heated room
downward to an unheated crawl-space/cellar.

I have read some testing reports that show those 3/8" doubvle
radiant barriers under slabs to have a non-measureable difference
to no insultaion at all. ****ed off my concrete guy but I gave him
a print out of the report and now I can't find it again.


Yeah, putting some other material in direct contact with the foil,
such as a layer of wallboard, or a concrete floor pretty much
nullifies the affects of the foil. Of course, if the foil is over
one inch of foam board, you still have the one inch of foam and its
insulation value. But not worth paying any extra to get the foil.

daestrom



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Nick , enough of the equasions, what R value is it.. Go to basic, the
accepted.route for us normals .

Then I can see if its another Easy Bake Sauna

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daestrom wrote:

"Jeff" wrote in message
k.net...

wrote:


snip



From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.


One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every year
or so, it will accumulate and lose its effectiveness.


Well that puts an interesting spin on my underfloor, staple up, unheated
basement app.

It looks to me that I have two ways to go:

1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
radiant barrier wired up with wire hangers or
something similar. An airspace of an 1 1/2" or so.
2) double bubble (triple radiant)

I think the radiant barrier is essential due to the higher temp of the
radiant to ambient.

Originally I had only thought of method 1.

But radiant barrier batts are hard to find. Adding a radiant barrier
to an existing is awkward.

So method two, which is what at least some staple up suppliers
provide, seems plausible. It would be easier to dust seal this and it
certainly would be easier to install.

Have I missed something, or is this really the best app for radiant
bubble? Perhaps the only time it should be used.

Jeff



In attics, it's advised to put the radiant barrier on the rafters
overhead so the radiant surface is on the underside. For underfloor
installations, the same thing. The foil goes on the underside to limit
the accumulation of dust that will ruin its effectiveness.

daestrom


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Jeff wrote:
daestrom wrote:

From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03

Obviously that's all from observations.


With how many foils and what temp? What's the significance of "W" and "S"
with downward heatflow? A winter floor and a summer ceiling?

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.


One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every year
or so, it will accumulate and lose its effectiveness.


So up-facing foils may not help much, unless they are well-sealed above.

It looks to me that I have two ways to go:

1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
radiant barrier wired up with wire hangers or
something similar. An airspace of an 1 1/2" or so.
2) double bubble (triple radiant)


It seems that Reflectix makes a product with no radiant effect for use
under concrete, and another with 2 foils (not "triple radiant") on the
outside. The inner layers have no foil. Other options are double-foil
polyiso board and double-sided "builders foil" in 4' rolls at 10-20
cents/ft^2 from companies like Innovative Insulation, and more costly
adhesive-backed foil, and OSB with one foil face, which might be found
on the underside of a roof.

... method two, which is what at least some staple up suppliers
provide, seems plausible. It would be easier to dust seal this and it
certainly would be easier to install.


Dust sealing the exposed upper foil would be difficult.

Have I missed something, or is this really the best app for radiant
bubble? Perhaps the only time it should be used.


Radiant barriers are good for downward heatflow (including a fridge roof),
OK for horizontal heatflow, and poorish for upward heatflow.

Nick



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"daestrom" wrote in message
...

"Jeff" wrote in message
k.net...
wrote:

snip


From The Passive Solar Energy Handbook, Edward Mazria 1979 we have this
in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.


One thing though about radiant barriers. It's well settled that the upper
surface of horizontal installations will not retain its low emissivity.
Unless you fancy wiping and cleaning off the dust every year or so, it
will accumulate and lose its effectiveness.

In attics, it's advised to put the radiant barrier on the rafters overhead
so the radiant surface is on the underside. For underfloor installations,
the same thing. The foil goes on the underside to limit the accumulation
of dust that will ruin its effectiveness.


I always thought the shiny side reflects, so needs to be facing where heat
needs to be reflected back and there needs to be a 1" gap between that and
any other surface. Having it under floors facing down should not be
effective. Yet I have read that some makers say it does not matter which way
it goes, I find that hard to believe.


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wrote in message
...
Jeff wrote:
daestrom wrote:

From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03

Obviously that's all from observations.


With how many foils and what temp? What's the significance of "W" and "S"
with downward heatflow? A winter floor and a summer ceiling?

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.

One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every year
or so, it will accumulate and lose its effectiveness.


So up-facing foils may not help much, unless they are well-sealed above.

It looks to me that I have two ways to go:

1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
radiant barrier wired up with wire hangers or
something similar. An airspace of an 1 1/2" or so.
2) double bubble (triple radiant)


It seems that Reflectix makes a product with no radiant effect for use
under concrete, and another with 2 foils (not "triple radiant") on the
outside. The inner layers have no foil. Other options are double-foil
polyiso board and double-sided "builders foil" in 4' rolls at 10-20
cents/ft^2 from companies like Innovative Insulation, and more costly
adhesive-backed foil, and OSB with one foil face, which might be found
on the underside of a roof.

... method two, which is what at least some staple up suppliers
provide, seems plausible. It would be easier to dust seal this and it
certainly would be easier to install.


Dust sealing the exposed upper foil would be difficult.

Have I missed something, or is this really the best app for radiant
bubble? Perhaps the only time it should be used.


Radiant barriers are good for downward heatflow (including a fridge roof),
OK for horizontal heatflow, and poorish for upward heatflow.


In keeping heat ina house, fine for the walls, no good in the attic.

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Default US R-values of radiant barriers

News wrote:

I always thought the shiny side reflects, so needs to be facing where heat
needs to be reflected back


When heat radiation strikes a surface, it's either transmitted, absorbed,
or reflected. Kirchoff said "It has to go somewhere," ie T + A + R = 1. If
T = 0 (an opaque surface with no transmission), A + R = 1. If the surface
emits as much power as it absorbs, E = A, integrated over the whole spectrum
(R is an energy conservation wash.) So a foil has reflectivity 1-E, which
is large if E is small, ie it's a good heat mirror. It can stay cool because
it doesn't absorb much heat, and it won't lose much heat because it's at
a low temp and it emits poorly.

and there needs to be a 1" gap between that and any other surface.


Big gaps with less still-air conductance are good for downwards heatflow.
A 1-1.5" gap is good for sideways heatflow. Smaller gaps have more still-air
conductance and larger gaps have slightly more "convection conductance."

Having it under floors facing down should not be effective.


It should be, if there's an air gap beneath the foil.

Nick

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Default US R-values of radiant barriers

News wrote:

"daestrom" wrote in message
...

"Jeff" wrote in message
k.net...
wrote:

snip


From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03


Obviously that's all from observations.

What strikes me for my application at hand, insulating under staple
up radiant, is that 8.94 for a single radiant barrier. It sure makes
foil double bubble look good.


One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every
year or so, it will accumulate and lose its effectiveness.

In attics, it's advised to put the radiant barrier on the rafters
overhead so the radiant surface is on the underside. For underfloor
installations, the same thing. The foil goes on the underside to
limit the accumulation of dust that will ruin its effectiveness.


I always thought the shiny side reflects, so needs to be facing where
heat needs to be reflected back and there needs to be a 1" gap between
that and any other surface. Having it under floors facing down should
not be effective. Yet I have read that some makers say it does not
matter which way it goes, I find that hard to believe.


We're talking about the FOIL side. Its going to be shiny regardless.

With a crawl space underneath, IT MAKES LOADS of sense. But the
direction it faces is CLIMATE dependent. Cold climates, foil side
faces towards the house to radiate heat back to the floors. Hot
climates, it faces down to reflect back heat from the crawl space.

Foil, insulation, paper, or foil insulation foil are available

In new construction, you can get foam boards for sheathing that have the
radiant barrier foil attached, in some cases to BOTH sides.
www.atlasroofing.com for an example of such. A 2" board will add about
$1.15 sq ft to materials cost of the house and adds R12 to the walls.
Similar boards are available for roofs, in areas that will see water
freeze on the roof.

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Default US R-values of radiant barriers

News wrote:


wrote in message
...

Jeff wrote:

daestrom wrote:


From The Passive Solar Energy Handbook, Edward Mazria 1979 we have
this in Appendix E.6 Resistance values of airspaces

Horizontal, Heatflow Down
NR=Non Reflective

Thickness | Season | NR/NR | NR/Aluminum Coated | NR/Foil
3/4 W 1.02 2.39 3.55
1 1/2 W 1.14 3.21 5.74
4 W 1.23 4.02 8.94
3/4 S 0.84 2.08 3.25
1 1/2 S 0.93 2.76 5.24
4 S 0.99 3.38 8.03

Obviously that's all from observations.



With how many foils and what temp? What's the significance of "W" and "S"
with downward heatflow? A winter floor and a summer ceiling?

What strikes me for my application at hand, insulating under staple up
radiant, is that 8.94 for a single radiant barrier. It sure makes foil
double bubble look good.


One thing though about radiant barriers. It's well settled that the
upper surface of horizontal installations will not retain its low
emissivity. Unless you fancy wiping and cleaning off the dust every
year
or so, it will accumulate and lose its effectiveness.



So up-facing foils may not help much, unless they are well-sealed above.

It looks to me that I have two ways to go:

1) 3 1/2" (R 11 + R 6 or so for the radiant) fiberglass batts with a
radiant barrier wired up with wire hangers or
something similar. An airspace of an 1 1/2" or so.
2) double bubble (triple radiant)



It seems that Reflectix makes a product with no radiant effect for use
under concrete, and another with 2 foils (not "triple radiant") on the
outside. The inner layers have no foil. Other options are double-foil
polyiso board and double-sided "builders foil" in 4' rolls at 10-20
cents/ft^2 from companies like Innovative Insulation, and more costly
adhesive-backed foil, and OSB with one foil face, which might be found
on the underside of a roof.

... method two, which is what at least some staple up suppliers
provide, seems plausible. It would be easier to dust seal this and it
certainly would be easier to install.



Dust sealing the exposed upper foil would be difficult.

Have I missed something, or is this really the best app for radiant
bubble? Perhaps the only time it should be used.



Radiant barriers are good for downward heatflow (including a fridge
roof),
OK for horizontal heatflow, and poorish for upward heatflow.



In keeping heat ina house, fine for the walls, no good in the attic.


I disagree, but I'm willing to listen to your reasoning if you care to
present it.

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