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Default Sheds and condensation avoidence thereof

Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.

--

All the best,

Chris
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Default Sheds and condensation avoidence thereof

I would have thought that you would not have a problem without a
source of humiIdity like steam from cooking, drying clothes, people
living in it or rising damp. If you do, maybe because of warm days and
cold nights (as boats do) then a dehumidifier should keep it at bay.
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On 20/01/2011 14:40, Chris Wilson wrote:
Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Insulate and use electric heating, which has a drying effect. My latest
shed has 100mm insulation in the roof, 50mm under the floor and 25mm on
the walls, which seems quite adequate in all weathers.

Colin Bignell
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On Jan 20, 2:40*pm, Chris Wilson wrote:
Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Basically dehumidifier or heat. Dehumidifier is far cheaper to run.


NT
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Default Sheds and condensation avoidence thereof


Chris Wilson wrote:

Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer.


snip

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


The problem is the faster temperature rises that cause items having a
large (undefined) thermal mass to lag far enough behind the rising
temperature to fall below the dew point.

If your shed gets down to say 2 degC overnight with 50 percent
humidity, then if the morning sunshine causes a rapid rise in
temperature to say 10 degC, it's a racing cert that large items will
only have reached the dew point of 4 degC when the shed thermometer
reads rather higher than this.

As moisture settles out from the air, every surface including internal
ones that have a pathway to air will suffer condensation, with all the
problems that can cause.

Heating such a shed to a temperature having a high probability of
avoiding the dew-point problem (10 degC might be such a figure) would
cost a fortune unless extremely well insulated. Dehumidifiers could be
a way to go, but you'd need one that works down close to 0 deg C and
they are expensive too.

Some combination of insulation, humidity control, and emergency
electric heating would, if you kept your eye on each day's overnight
weather forecast, avoid the most of the problems, but finding where
the balance should be struck between these three is going to be
interesting.

TF


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On Jan 20, 3:28*pm, Tabby wrote:
On Jan 20, 2:40*pm, Chris Wilson wrote:

Folks,


I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.


I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.


My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Basically dehumidifier or heat. Dehumidifier is far cheaper to run.

NT


Unfortunately dehumidifiers don't work at low temperatures.
Condensation is a well known problem in sheds. Basically as the
weather warms up, the air holds more water. This condenses on anything
that's colder, especially at night as the air temp drops anyway. Large
lumps of metal are particularly suseptible, smaller ones less so. My
lathe always suffers as it's nearly a ton of cast iron.
Stationary engine enthusiasts are always moaning about condensation.
They spray everything with various oils to protect the metal. That may
not be an option for you. I'm assuming your models are relatively
small.
The only answer is to heat, and possibly duhumidify the shed. The
trouble is that's expensive.

John
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On Jan 20, 2:40*pm, Chris Wilson wrote:
Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.

--

All the best,

Chris


My shed, 14"x 8", complete with model railway. Outer skin horizontal
timber shiplap boards, underneath is a layer of breather roofing
underlay all the way round and including the roof and floor. Roof &
floor is constructed of t&g boards. The roof is covered with top
quality mineral felt, under the roofing boards in between is 50mm
insulation boards fitted tight up to the underlay. The floor as a
layer of breather underlay covered with 12mm insulation covered with
clip fit boards. The inside walls have 50mm insulation fitted tight up
to the layer of breather underlay covered with 12mm sheet ply board.
In the winter I have and electric heater with a thermostat sitting,
this is set just to keep the chill off and try to keep any
condensation at bay. I’ve had no problems apart from the heat in the
summer, it gets a little to warm and a few spiders.
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On Jan 20, 2:40*pm, Chris Wilson wrote:
Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.

--

All the best,

Chris


Most moisture is likely to arise from the floor. Concrete is OK but
you need t have a damp proof membrane in it. I would consider putting
your locos & any portable electric bits in a cabinet with it's own
chemical dehumidfier.
With the shed as well as insulation, you need to consider one of two
options ventilation, or alternatively, seal it up tight and a
dehumidifier. Permenent heat would be an expensive option unless you
can tap in off your home central heating.
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On Jan 20, 2:40*pm, Chris Wilson wrote:
Folks,

I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.

I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.

My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.

--

All the best,

Chris


The biggest problem is likely to be the roof. The cheapest and easiest
is metal, but you must insulate it to prevent condensation. The
condensation occurs when cold weather is followed by warm when any
metal objects as well as the roof cool the air and cause condensation.
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Chris Wilson wrote in
:

Folks,


Thank you all very much for the tips, ideas and "heads up". If I haven't
replied personally it doesn't mean that I haven't read your post, let alone
valued the advice contained within for I have.

--

All the best,

Chris


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On Thu, 20 Jan 2011 14:40:21 GMT, Chris Wilson
wrote:


My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Fit an (Inverter) heat pump air conditioner. Cheaper to run than an
electric heater and has a built in dehumidifier function as well.
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On Jan 20, 4:19*pm, John wrote:
On Jan 20, 3:28*pm, Tabby wrote:



On Jan 20, 2:40*pm, Chris Wilson wrote:


Folks,


I plan on building reasonably large wooden shed (either with a concrete or
more likely a raised wooden floor) this summer, it's going to be a non
standard shape somewhat trapezoidal approx 26' by 16' at its widest
narrowing to around 12' at one end.


I'm more than happy with the basic design and I'm happy I have the skills
for the basic construction and so forth however I will wish to insulate the
shed so that the inside remains dry and at more or less constant (extremes
of winter excluded) temperature. If anyone's that interested I'll be
putting a model railway inside it.


My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Basically dehumidifier or heat. Dehumidifier is far cheaper to run.


NT


Unfortunately dehumidifiers don't work at low temperatures.


Incorrect, but I did forget to mention that some dont. For winter use
you'll need an absorption unit, not a compressor type.


NT


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On Jan 20, 5:41*pm, Chris Wilson wrote:
Kipper at sea wrote in news:77b2da60-93e5-400b-
:

timber shiplap boards, underneath is a layer of breather roofing
underlay all the way round and including the roof and floor.


Cool, so it's skin, underlay then insulation in that order. Have you put an
internal skin on the walls/roof or have you left the underlay exposed?

--

All the best,

Chris


I visited a few timber shed makers and one in partially had the idea
of covering the ends & sides of the timber frame with tar paper on the
out side then fixing the ship lap boards on to the timber frame. So I
decided to use this company but supplied them with a roll of roof
shield breather underlay. They covered all sides, ends and the roof.
after they had erected the shed I filled all the gaps between the
frame on the inside with insulation and ply boarded over.I was going
to use plaster board for the inside but decide it would make it more
secure to use 12mm ply. The surplus underlay I covered the floor with
and then covered with insulation and clip flooring. The roof on the
inside I cut sheets of insulation and tight fitted them in the frame
of the inside of the roof up to the underlay and held it in with nails
driven into the frame sides not through the insulation. One thing I
did do was to raise the concrete base above ground level and make the
base small enough to fit inside the ship lap board so the rain would
not run under the floor supports.
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On Jan 20, 8:34*pm, Kipper at sea wrote:
On Jan 20, 5:41*pm, Chris Wilson wrote:

Kipper at sea wrote in news:77b2da60-93e5-400b-
:


timber shiplap boards, underneath is a layer of breather roofing
underlay all the way round and including the roof and floor.


Cool, so it's skin, underlay then insulation in that order. Have you put an
internal skin on the walls/roof or have you left the underlay exposed?


--


All the best,


Chris


I visited a few timber shed makers and one in partially had the idea
of covering the ends & sides of the timber frame with tar paper on the
out side then fixing the ship lap boards on to the timber frame. So I
decided to use this company but supplied them with a roll of roof
shield breather underlay. They covered all sides, ends and the roof.
after they had erected the shed I filled all the gaps between the
frame on the inside with insulation and ply boarded over.I was going
to use plaster board for the inside but decide it would make it more
secure to use 12mm ply. The surplus underlay I covered the floor with
and then covered with insulation and clip flooring. The roof on the
inside I cut sheets of insulation and tight fitted them in the frame
of the inside of the roof up to the underlay and held it in with nails
driven into the frame sides not through the insulation. One thing I
did do was to raise the concrete base above ground level and make the
base small enough to fit inside the ship lap board so the rain would
not run under the floor supports.


Don’t use tin roofing of fibre cement sheets they are known for
condensation. Stick to a top quality heavy duty bitumen granule felt
fix to t&g boards.
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I'm going to throw something ad hoc in he

My old man kept all his steel tools in a big wooden cheast of drawers in a
mouldy damp garage with a non DPC concrete floor.

Wind howled through both door frames and the window was dodey, though there
were no liquid water leaks.

The tools, including planes stayed in near mint condition.


The chest was heavy (2' x 4' x 3-4' high and 3/4" thick wood. The drawers
were close fitting and the inside bare.

It was his theory that the wood acted as a buffer taking in free water in
preference to it condensing out - also the wood did have some insulation
value.

So perhaps a wooden cupboard for tools - real wood or thick ply, painted or
varnished on the outside, bare inside and well sealed (close fitting or
draught strip)...

Also, if using a small instrincally safe heater[1], or dessicant, they will
go a lot further in a small sealed space...

I realise if the OP wants a trainset or large tools to be protected, this
won;t work, but for all the small and power tools it could - and an
excellent inscentive to put away

[1] RS have some small ceramic low temperature heaters that are supposed to
be instrisically safe (in the way that an oil radiator is).

--
Tim Watts
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On Jan 20, 6:08*pm, Peter Parry wrote:
On Thu, 20 Jan 2011 14:40:21 GMT, Chris Wilson

wrote:
My main concern is condensation or to be more precise how to avoid
condensation, if anyone could give any pointers I'd be most grateful.


Fit an (Inverter) heat pump air conditioner. *Cheaper to run than an
electric heater and has a built in dehumidifier function as well.


I have found this fascinating. I built myself a new workshop 3 years
ago which has both metal working and wood working lathes - both large
and CI. There is also a circular saw, band saw and large vertical
drill. I live near Edinburgh. So I live in a cool, dampish area and
have a lot of metalwork on which moisture could condense if it
wished.

I do not have any problems, and I haven't made any specific provision
against condensation either that I know of.

The shed is an extension to a garage and being on a sloping site its
concrete floor is raised above ground level on 2 sides. There's a dpm
in the concrete and rubber matting on the floor. Wooden frame, 2
windows, 2 doors, 3" timber framing with fibre glass insulation and
weatherboard facing, no breathing layer under the weatherboarding, but
a dpm under the inner lining of OSB board to prevent condensation in
the insulation. Roof is insulated, and covered with Onduline over
OSB, plasterboard ceilng. Basic electric fan heater with internal
thermostat that is turned to minimum every night.

I was interested in the story about storing the tools in a wooden
chest and wonder if the relative air tightness of my workshop and the
presence of quite a lot of wood and shavings act as an absorber of the
moisture and it doesn't get a chance to settle out on cold surfaces.

I did wonder about condensation when the shed was being built and a
humiditistat controlled extractor fan was installed, but found to be
unnecessary and has remained switched off.

I'm sorry if my story flies in the face of everyone else and creates
confusion. One possible factor in thinking about it, is that only in
error do I allow the workshop to get much above 10 or 12 C in winter,
usually finding that a padded boiler suit, etc. is adequate even for
fine work.

Rob


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On 20 Jan, 17:39, Chris Wilson wrote:
Chris Wilson wrote 3:

Folks,


Thank you all very much for the tips, ideas and "heads up". If I haven't
replied personally it doesn't mean that I haven't read your post, let alone
valued the advice contained within for I have.

--

All the best,

Chris


I have this problem in my workshop and heating it is a no go. The
best answer I found was to cover those machines prone to rusting.
Table saw, band saw, spindle moulder and planer thicknesser all have
their own 4mm ply cover. Little trouble to put on and remove. Smaller
machines have a canvas cover and all else goes into drawers. I uses
Renaissance wax on the hand tools and machine wax on the larger
machinery though it isn't really necessary as the ply does the job on
it's own.

Possible with a model railway you could provide some sort of a fabric
cover ?

Paul Mc Cann
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fred ) wibbled on Friday 21 January 2011 09:34:


Possible with a model railway you could provide some sort of a fabric
cover ?


and make sure it is natural fabric - cotton, linen or wool - all of which
can absorb moisture.

--
Tim Watts
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On 21/01/11 09:45, Tim Watts wrote:
fred ) wibbled on Friday 21 January 2011 09:34:


Possible with a model railway you could provide some sort of a fabric
cover ?


and make sure it is natural fabric - cotton, linen or wool - all of which
can absorb moisture.



But you may need to provide some ventilation and regular airing for
those covers to avoid mildew, mould etc.

--
djc

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On Fri, 21 Jan 2011 09:45:23 +0000, Tim Watts wrote:

fred ) wibbled on Friday 21 January 2011 09:34:

Possible with a model railway you could provide some sort of a fabric
cover ?


and make sure it is natural fabric - cotton, linen or wool - all of which
can absorb moisture.


Wool is the best for 'managing' moisture, IIRC.
--
Peter.
The gods will stay away
whilst religions hold sway
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PeterC ) wibbled on Friday 21 January 2011
14:39:

On Fri, 21 Jan 2011 09:45:23 +0000, Tim Watts wrote:

fred ) wibbled on Friday 21 January 2011 09:34:

Possible with a model railway you could provide some sort of a fabric
cover ?


and make sure it is natural fabric - cotton, linen or wool - all of which
can absorb moisture.


Wool is the best for 'managing' moisture, IIRC.


I saw it claimed on a website selling irish wool for roof insulation -
basically the claim was it lessened the risk of rot in timbers by buffering
some degree of moisture before it condensed out elsewhere. Could see a
reason to disbelieve it - though it wasn't stated exactly how much water a
given amount of wool could absorb whilst remaining dry to the touch at
various temperatures (if temperature has any bearing).

Mind you - my BCO still wanted the usual ventilation paths and spacings when
I was discussing the possibility of using wool...


--
Tim Watts


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robgraham wrote:

My workshop is relatively air tight so as insolation raises the
temperature there is not in ingress of moist air to match this rising
temperature, and hence cause condensation when it cools in the
evening. That's a possible theory anyway !!


Very approximately, the number of grams of water per cubic metre in
saturated air is the numerical equivalent of the temperatu at 15
degC the air can hold 15g of water per cubic metre.

Let's say your shed has small swings in temperature, from say 6 degC
overnight to 10 degC during the day. If the humidity remained constant
at 50 percent, then even if the machinery remained at 6 degC because
it warmed up slowly, there would be no condensation as then the dew
point at 10 degC and 50 percent (relative) humidity is 5 degC:

The air is 50 percent saturated (50 percent RH at 10 degC); and 50
percent of 10 grams (saturated air at 10 degC) is 5 grams. but 5 grams
is enough to saturate air at 5 degC, and so 5 degC is the dew-point.

If, however, the temperature swing was from 6 degC overnight to 13
degC all at 50 percent RH, then the dewpoint would be 6.5 degC and
condensation would take place.


TF
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Terry Fields wrote:

Very approximately, the number of grams of water per cubic metre in
saturated air is the numerical equivalent of the temperatu at 15
degC the air can hold 15g of water per cubic metre.

Let's say your shed has small swings in temperature, from say 6 degC
overnight to 10 degC during the day. If the humidity remained constant
at 50 percent, then even if the machinery remained at 6 degC because
it warmed up slowly, there would be no condensation as then the dew
point at 10 degC and 50 percent (relative) humidity is 5 degC:

The air is 50 percent saturated (50 percent RH at 10 degC); and 50
percent of 10 grams (saturated air at 10 degC) is 5 grams. but 5 grams
is enough to saturate air at 5 degC, and so 5 degC is the dew-point.

If, however, the temperature swing was from 6 degC overnight to 13
degC all at 50 percent RH, then the dewpoint would be 6.5 degC and
condensation would take place.


How do you justify your assumptions?

Suppose your shed begins its day at 6 degC and is full of 50% RH air
(and therefore contains about 3g of water per m3), and suppose further
that by the early afternoon it warms up to 13 degC. This warming
up is going to reduce the RH of the shed air (to about 23%), and then
by the time it cools down to 6 degC again, the RH will have gone back
up to 50% (and hence still be non-condensing).

The only way to increase the 13 degC RH to 50% would be to add water
to the shed air. Where is this going to come from?

OK, so there could have been a change in the weather, increasing
the outside RH, and if the shed has been in use, with doors/windows
wide open, then the shed air would become well enough mixed with
outside air to be indistinguishable from it. But if the shed has
remained closed, and its structure and windows/doors are reasonably
well sealed, the absolute (not relative) humidity is going to remain
constant at 3g/m3.

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Ronald Raygun wrote:

Terry Fields wrote:

Very approximately, the number of grams of water per cubic metre in
saturated air is the numerical equivalent of the temperatu at 15
degC the air can hold 15g of water per cubic metre.

Let's say your shed has small swings in temperature, from say 6 degC
overnight to 10 degC during the day. If the humidity remained constant
at 50 percent, then even if the machinery remained at 6 degC because
it warmed up slowly, there would be no condensation as then the dew
point at 10 degC and 50 percent (relative) humidity is 5 degC:

The air is 50 percent saturated (50 percent RH at 10 degC); and 50
percent of 10 grams (saturated air at 10 degC) is 5 grams. but 5 grams
is enough to saturate air at 5 degC, and so 5 degC is the dew-point.

If, however, the temperature swing was from 6 degC overnight to 13
degC all at 50 percent RH, then the dewpoint would be 6.5 degC and
condensation would take place.


How do you justify your assumptions?

Suppose your shed begins its day at 6 degC and is full of 50% RH air
(and therefore contains about 3g of water per m3), and suppose further
that by the early afternoon it warms up to 13 degC. This warming
up is going to reduce the RH of the shed air (to about 23%), and then
by the time it cools down to 6 degC again, the RH will have gone back
up to 50% (and hence still be non-condensing).

The only way to increase the 13 degC RH to 50% would be to add water
to the shed air. Where is this going to come from?

OK, so there could have been a change in the weather, increasing
the outside RH, and if the shed has been in use, with doors/windows
wide open, then the shed air would become well enough mixed with
outside air to be indistinguishable from it. But if the shed has
remained closed, and its structure and windows/doors are reasonably
well sealed, the absolute (not relative) humidity is going to remain
constant at 3g/m3.


I thought humidity worked like this until I bought a weather station
having an external temperature and humidity sensor. I found that the
humidity stays remarkable constant.

There is reason to suppose this is the case, as other postings in this
thread have shown concerning placing tools in mighty wooden cases
acting effectively as a humidity sink. Wooden floors, benches, cloth
items, and other furniture will add to this. But this works two ways,
if the humidity starts to fall as the temperature rises, the items
acting as a humidity sink will start to lower their water content
towards the new equlibrium value and tend keep the shed atmosphere in
equilibrium.

And the presence of a human being in the shed is going to be a
disaster. Let's say it's the size of a garage, 2m x 2m x 6m or 24 cu
metres. At 50 percent RH and 12 degC (robgraham's figure) this
garage/shed will hold 6 x 24 = 144 grams of water. Two hour's work by
an occupant will add about another 100 grams (figures from a
scientific paper) from respiration and sweat, for a total of 244g or
just over 10 g per cubic metre. The temperature of the shed will only
need to fall to 10 degC, a mere 2 degrees, before reaching the dew
point, if the items acting as a humidity sink don't absorb the surplus
fast enough. Three hour's work and there's every chance of
condensation, unless all that wood can take up the increase.

The only type of shed that won't have items acting as a humidity sink
will be metal or glass ones, and they are notorious for condensation
problems.

TF
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Default Sheds and condensation avoidence thereof

Kipper at sea wrote in
:

,,
Don’t use tin roofing of fibre cement sheets they are known for
condensation. Stick to a top quality heavy duty bitumen granule felt
fix to t&g boards.


Sorry for teh slow reply ... been away, thanks very much for the tip, was
going for all wood in any event but nice to see teh confirmation

--
All the best,

Chris
  #30   Report Post  
Posted to uk.d-i-y
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Posts: 98
Default Sheds and condensation avoidence thereof

Kipper at sea wrote in
:

,,
Don’t use tin roofing of fibre cement sheets they are known for
condensation. Stick to a top quality heavy duty bitumen granule felt
fix to t&g boards.


Sorry for the slow reply ... been away, thanks very much for the tips, was
going for all wood in any event but nice to see teh confirmation

--
All the best,

Chris


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