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Spray foam shop staying hot

Talon2006

Talon2006

Yellow Skull
Joined
May 19, 2020
Member Number
282
Messages
426
So I have a 30x40 shop with 2” of spray foam. I have AC in there but don’t run it all the time.

The spray foam does great, almost too good in that my shop will heat up to 100 degrees during the day, and the spray foam will keep all the heat in all night.

I am thinking a secondary fan/ventilation setup would help cool the shop over night, and possibly keep it cooler during the day.

I also have a 12x14 roll up door that is not insulated facing the sun all day, and I know that is not helping either.

Suggestions?
 
This makes me really see how messy my shop is.


image.jpg

The door in the photo on the photo above is in sunlight. The door in the second photo goes into the other 30x40 half of the shop.


image.jpg
 
You have other issues, its not the door in the sun

Just looking at it, I'd be surprised if thats averages 2", stick the center of a couple panels and a few of the valleys with some stiff wire marked @ 2"

Also, looks like the transition from the top plate to the roof are not sprayed correctly but its hard to tell from those pics.

Your peak vent is sprayed closed, correct ? There should be zero openings to the outside

I'd be happy to send you a FLIR camera, it'll tell you for a fact where your issues are.
 
rockmup said:
You have other issues, its not the door in the sun

Just looking at it, I'd be surprised if thats averages 2", stick the center of a couple panels and a few of the valleys with some stiff wire marked @ 2"

Also, looks like the transition from the top plate to the roof are not sprayed correctly but its hard to tell from those pics.

Your peak vent is sprayed closed, correct ? There should be zero openings to the outside

I'd be happy to send you a FLIR camera, it'll tell you for a fact where your issues are.
Click to expand...
Some of the areas are thin. I wish I walked around the whole thing with a nail before they left.

The roof vent is shut, and the whole thing is very well sealed.

If I hit it with my temp gun, the door will be 110+ where everything else is ambient or close to ambient temp.
 
Thats normal for the door and theres nothing you can do about it. Still no way that shop should be 100* on any day.
Looks like its really thin @ the top plate. I'd bet its not sealed on top of any of the top plate transition, it should be 2" on everything. You'd need to get up there and look, take pics. Any bare metal just transfers heat. Your vent on the peak should have been sprayed shut.
Take some pics with the lights off, looks like all the purlins are thin to nothing inside the C. Hard to tell with the glare


The FLIR will tell you where the issue is.
 
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rockmup said:
Thats normal for the door and theres nothing you can do about it. Still no way that shop should be 100* on any day.
Looks like its really thin @ the top plate. I'd bet its not sealed on top of any of the top plate transition, it should be 2" on everything. You'd need to get up there and look, take pics. Any bare metal just transfers heat. Your vent on the peak should have been sprayed shut.
Take some pics with the lights off, looks like all the purlins are thin to nothing inside the C. Hard to tell with the glare


The FLIR will tell you where the issue is.
Click to expand...
You don’t think it should get to 100 degrees in south Texas with the AC off?
 
2" of spray foam (if it's that thick) is more of an air & vapor barrier, than insulation.

You might have R-8 - R-12 there... the last shop we built had R-49 in the lids and R-23 in the walls.
 
My bare metal roll up door is wild temperature radiator, easily 115* in the direct sun measured on the inside of the shop.

IMO try just leaving the AC on 24/7 at a really high number.

My 22k BTU window unit doesn't keep up in this heat but my shop is about as tight as a crab trap...

A buddy has a 50x75 spray foamed metal building in North Texas, when he did not run the air conditioner, it made zero difference vs the outside ambient temperature.

If it was 98 outside it was 98 inside, on and on.

Either deal with the slow cool down if you leave the HVAC off or leave the HVAC on at a high temp.
89* in my shop today was pretty nice feeling standing in front of a box fan.
 
FC4X4 said:
2" of spray foam (if it's that thick) is more of an air & vapor barrier, than insulation.

You might have R-8 - R-12 there... the last shop we built had R-49 in the lids and R-23 in the walls.
Click to expand...
This !!
 
I looked at those pix again and yes those doors are huge radiators.

My suggestion for short term relief is to put magnets on the foil side of some 3/4" EPS foam. You can stock those sheets to the door and block the radiant heat.

I did some tests with 1/2" EPS foil backed foam would drop the temp to ambient.
 
There's plenty of guys just using foam, bluetex etc. and gluing and taping it on but I am not really convinced that's worth the effort.
 
This looks good.

I don’t really have a hard time cooling off the shop with the AC, I’m just wondering if there is a way I can install some type of vent/fan I can run at night when I’m not running the AC.
 
I have a centrifugal blower (HVAC fan) mounted under the eave in the center of the back wall. It can exhaust hot air really quick and theoretically cool the inside to ambient temp.

In practice that doesn't work so great, I just run the AC.
A better move is to face the building so there are opposing doors north and south...
 
My ultimate plan is 4x 60" metal blade ceiling fans in each side of the 30x40 shop, 8 total.

Keep the humidity low, and the air moving and it's like living in Arizona :flipoff2:
 
Talon2006 said:
This looks good.

I don’t really have a hard time cooling off the shop with the AC, I’m just wondering if there is a way I can install some type of vent/fan I can run at night when I’m not running the AC.
Click to expand...

The hot air you suck out with the vent fans at night will be replaced by the ambient temperature air. On cool nights they may help but on July/August Texas nights it's not going to help much if at all. Put the money you save on vent fan electricity towards keeping the A/C running longer at night.

Also, is your system on a smart thermostat? If so, just set a schedule that starts cooling it off before you get there and keep it on at a higher # at night so it doesn't have to work as hard in the morning to cool it off.

Maintaining a consistent temperature will always be cheaper bill wise in a building you use frequently vs turning it completely off when not in use.
 
CarterKraft said:
I have a centrifugal blower (HVAC fan) mounted under the eave in the center of the back wall. It can exhaust hot air really quick and theoretically cool the inside to ambient temp.

In practice that doesn't work so great, I just run the AC.
A better move is to face the building so there are opposing doors north and south...
Click to expand...

The doors on the attached garage at my house face directly west and in the summer it blows but in the winter its no so bad. :laughing:

The shop I build out back will definitely have the doors situated north/south and most likely a windowless wall on the west side to combat heat.
 
SLOWPOKE693 said:
The hot air you suck out with the vent fans at night will be replaced by the ambient temperature air. On cool nights they may help but on July/August Texas nights it's not going to help much if at all. Put the money you save on vent fan electricity towards keeping the A/C running longer at night.

Also, is your system on a smart thermostat? If so, just set a schedule that starts cooling it off before you get there and keep it on at a higher # at night so it doesn't have to work as hard in the morning to cool it off.

Maintaining a consistent temperature will always be cheaper bill wise in a building you use frequently vs turning it completely off when not in use.
Click to expand...

I actually only run the AC a few hours a month when I need to do work in there.
CarterKraft said:
I have a centrifugal blower (HVAC fan) mounted under the eave in the center of the back wall. It can exhaust hot air really quick and theoretically cool the inside to ambient temp.

In practice that doesn't work so great, I just run the AC.
A better move is to face the building so there are opposing doors north and south...
Click to expand...

The north door is enclosed inside another shop, so it’s not so bad.

The south door still gets hit as balls.
 
Talon2006 said:
This looks good.

I don’t really have a hard time cooling off the shop with the AC, I’m just wondering if there is a way I can install some type of vent/fan I can run at night when I’m not running the AC.
Click to expand...
Can you set your ac to run as dehumidification a few hours before you come into the shop?
 
SLOWPOKE693 said:
If it's only used a few hours a month I'd just live with it. Get a smart thermostat and turn the A/C on wirh your phone before you get there, that's what I'd do in that case.
Click to expand...
That's exactly what I do, coming home from work if I know I'm going out there I'll just kick it on.

It costs me around $2 a day to run mine.
 
Talon2006 said:
I actually only run the AC a few hours a month when I need to do work in there.


The north door is enclosed inside another shop, so it’s not so bad.

The south door still gets hit as balls.
Click to expand...
That South facing door would be a large solar radiator in the shop.

I tried to calculate the hate gain from the door on mine but gave up, might be a good chatgpt question.
 
Talon2006 said:
You don’t think it should get to 100 degrees in south Texas with the AC off?
Click to expand...

No and I've done 50-60 metal buildings of various sizes in the deep south.

CC foam @ 2" is only R7 but it doesn't need to be more than that, theres diminishing returns beyond 2" for most applications. Its a thermal and vapor barrier.
You're lucky to have 1.5" by the look of it and it doesn't look like it was applied correctly so you have lots of heat intrusion. Foam isn't a pretty end product if its installed correctly, anywhere you have a beam or transition it builds up because of the dwell time when spraying. Thats fine because its supposed to encapsulate everything. They should have used pool noodles on the top plate and anywhere else to fill the gaps before spraying and from the looks of it, they didn't.
Your foam looks like they were trying to make it look pretty which is why you have no build up in those places

Like I said, I'll send you a FLIR, it will show you where your issues are
 
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rockmup said:
No and I've done 50-60 metal buildings of various sizes in the deep south.

CC foam @ 2" is only R7 but it doesn't need to be more than that, theres diminishing returns beyond 2" for most applications. Its a thermal and vapor barrier.
You're lucky to have 1.5" by the look of it and it doesn't look like it was applied correctly so you have lots of heat intrusion. Foam isn't a pretty end product if its installed correctly, anywhere you have a beam or transition it builds up because of the dwell time when spraying. Thats fine because its supposed to encapsulate everything. They should have used pool noodles on the top plate and anywhere else to fill the gaps before spraying and from the looks of it, they didn't.
Your foam looks like they were trying to make it look pretty which is why you have no build up in those places

Like I said, I'll send you a FLIR, it will show you where your issues are
Click to expand...
So in this scenario how hot should a properly insulated building get inside on consecutive 100* days?
 
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