I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

farseer wrote:
I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

metal passes air with less restiction so it can lead to long term $
savings.....

flexible saves bg bucks on install

since yours is a new install what system did you have previously?

I did not have a system before. I am replacing hot water heating
pipes...

wrote:
farseer wrote:
I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

metal passes air with less restiction so it can lead to long term $
savings.....

flexible saves bg bucks on install

since yours is a new install what system did you have previously?

wrote:

farseer wrote:

I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you


metal passes air with less restiction so it can lead to long term $
savings.....

care to elaborate, perhaps with some cites?


flexible saves bg bucks on install

since yours is a new install what system did you have previously?



--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

In article . com, "farseer" wrote:
I did not have a system before. I am replacing hot water heating
pipes...

WHY???????


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On Fri, 19 Jan 2007 02:50:03 GMT, CJT wrote:

wrote:

farseer wrote:

I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you


metal passes air with less restiction so it can lead to long term $
savings.....

care to elaborate, perhaps with some cites?


flexible saves bg bucks on install

since yours is a new install what system did you have previously?


Blow me.


--
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/

On Fri, 19 Jan 2007 03:09:51 GMT, (Doug Miller)
wrote:

In article . com, "farseer" wrote:
I did not have a system before. I am replacing hot water heating
pipes...

WHY???????

Blow me.


--
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/

In article , wrote:
On Fri, 19 Jan 2007 03:09:51 GMT, (Doug Miller)
wrote:

In article . com, "farseer"
wrote:
I did not have a system before. I am replacing hot water heating
pipes...

WHY???????

Blow me.

HOW???????


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

"Doug Miller" wrote in message
t...
In article ,
wrote:
On Fri, 19 Jan 2007 03:09:51 GMT, (Doug Miller)
wrote:

In article . com,
"farseer"
wrote:
I did not have a system before. I am replacing hot water heating
pipes...

WHY???????

Blow me.

HOW???????

Uh, nevermind

solid lines are smooth inside with less air turblance so theres better
airflow, in addition regular lines are harder to damage

the flexible lines are easier to damage but less costly to install.

I would go solid wherever possible with flexible as needed. this will
likely cost a bit more but long term be money well spent/

if headroom is a issue solid is likely better too, since flat problably
takes less space.

wrote:

solid lines are smooth inside with less air turblance so theres better
airflow, in addition regular lines are harder to damage

the flexible lines are easier to damage but less costly to install.

I would go solid wherever possible with flexible as needed. this will
likely cost a bit more but long term be money well spent/

if headroom is a issue solid is likely better too, since flat problably
takes less space.

What's the Reynolds number in a typical HVAC application?

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

See the following:

http://www.homeenergy.org/archive/he...96/960307.html
http://www.energyfederation.org/cons...ath/86_744_998
http://www.toolbase.org/PDF/DesignGu...stallation.pdf

Typical/example excerpt:

"Sheet metal ducts have a smooth interior surface that offers the least
resistance to air flow. . . . flexible duct is easily torn, crushed,
pinched, or damaged during installation. It has the highest resistance
to air flow."

For more technical study (including Reynolds numbers of the test cases)
of flex ducts in residential HVAC, see:

"A Study of Pressure Losses in Residential Air Distribution Systems" at

http://eetd.lbl.gov/ie/pdf/LBNL-49700.pdf

From "Conclusions":

"The flexible duct elbows have much higher local loss coefficients (due
to increased roughness) than those reported for sheet metal elbows."

and

"The results from the tested air distribution system components were
used in the complete duct system analysis and compared with available
data from the literature. The comparison showed that our new data
provide an improved estimate of the pressure drop for individual
sections. Both the new data and existing ACCA procedures gave reasonable
(less then 20% error) results for the total pressure drop. The ASHRAE
calculation methods give large (20% to 40%) underpredictions."

-----------------------------------------------------------
CJT wrote:

wrote:

farseer wrote:

I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you


metal passes air with less restiction so it can lead to long term $
savings.....

care to elaborate, perhaps with some cites?


flexible saves bg bucks on install

since yours is a new install what system did you have previously?


--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

writes:
On Fri, 19 Jan 2007 03:09:51 GMT, (Doug Miller)
wrote:

In article . com, "farseer" wrote:
I did not have a system before. I am replacing hot water heating
pipes...

WHY???????

Blow me.

I think you should be posting this to the homosexually-oriented groups
-- since you seem to be quite intent on having a guy blow you

" writes:
solid lines are smooth inside with less air turblance so theres better
airflow, in addition regular lines are harder to damage

the flexible lines are easier to damage but less costly to install.

I would go solid wherever possible with flexible as needed. this will
likely cost a bit more but long term be money well spent/

if headroom is a issue solid is likely better too, since flat problably
takes less space.

I know what you say is certainly true from physics -- turbulence is
wasted energy and disrupts smooth laminar flow etc.

But do you know how big a factor that is?
I'm actually interested because the incompetent "pro" who installed the
system for the previous owner ran flex duct all over the place and we
are trying to decide whether it pays to replace.

I have flex as a result of a major remodel done a few years ago. The
idiot contractor connected them using ordinary duct tape and did not
provide adequate support for each run. On at least 3 occasions the
flex seperated from junction boxes and I had to fix them. (the crawl
space was being heated better then the house).

If I had known then what I no now I wouldn't have allowed this crap to
ever be installed. If it's installed 100% correctly then I guess
it's a pretty good idea but that's a big "if". I'd say Flex is
totally unforgiving to poor installation procedures.
The other problem if that flex is round. Sometimes rectangular will
be less of an obstruction in areas where form factor is a
consideration.

I'd recommend 22 gauge galv. ducts in a heartbeat.





On 18 Jan 2007 16:34:35 -0800, "farseer"
wrote:

I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

Properly sized and installed flex is just as good as metal duct and is
far cheaper to install.

farseer wrote:
I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

blueman wrote:
" writes:

solid lines are smooth inside with less air turblance so theres better
airflow, in addition regular lines are harder to damage

I know what you say is certainly true from physics -- turbulence is
wasted energy and disrupts smooth laminar flow etc.

But do you know how big a factor that is?
I'm actually interested because the incompetent "pro" who installed the
system for the previous owner ran flex duct all over the place and we
are trying to decide whether it pays to replace.

Friction factors from Bill Pentz's site
(http://billpentz.com/woodworking/cyc...tingResistance)

Higher numbers are better:

1. Corrugated steel duct= 60
2. Spiral Duct = 90-100
3. Laser Welded Steel Duct = 110-125
4. PVC Duct = 146

In other places, flex hose is taken to have roughly 3X the resistance of
smooth ducting of the same size.

Chris

Well the way I see it Flex vs. Metal there is couple differences
cans: yes it does restrict some of air flow.
pros: is less loses of air temp. like metal it does not conduct
air temperature on outer wall,
there for not likely getting the condensation on outer wall
and it is cheaper installation.
Securing the flex duct to distribution duct
clamps are made for that.
Three pros. One cons. you pick?
from Dido

"farseer" wrote in message
oups.com...
I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

Thanks for all the replies. I am leaning towards "Metal and flex where
necessary". I've see cases where these flex get crushed, easily
damaged and the connections fall apart due to they taping they
use...don't want to be ripping up walls to fix these things in a few
years.

farseer wrote:
I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Please advise.

thank you

"farseer" wrote in news:1169166875.787921.117530
@l53g2000cwa.googlegroups.com:

I am having an HVAC system installed in my basement. I would like to
know what is the consensus/general opinion regarding the use of Flex
vs. Metal ducts? Which should i use?

I have had 3 companyies tell me i should use metal as much as possible
and use flex where necessary. Another two tell me everyone is using
flex these days and there is no disadvantage.

Flex ducting has a higher friction loss, and tends to sag, which
exaserbates the problem.
We have several condos in my area that used flex ducting and most have air
flow problems.

--
Respectfully, Bob

"Bob_Loblaw" wrote:

Flex ducting has a higher friction loss, and tends to sag, which
exaserbates the problem. We have several condos in my area
that used flex ducting and most have air flow problems.

I have a 12 year old house with flex ducting in the for the second floor system
and it seriously sucks. The resistance on the long runs makes it impossible to
get any kind of balanced airflow.