Help with cooling 24 by 40 garage

[redxiii75159]

Help needed, i have a 24ft by 40ft detached insulated (r10) steel garage with 12 foot ceilings and a 15ft peak. I also have 4 large skylights that let in a lot of sun. I live in dallas tx and it reaches up to 118 degrees in there and it is just unbearable. Bought a thru the wall 18k ac unit and it did absolutely nothing (wasted money).Please help with some suggestions i would be so grateful. Im thinking of adding a ceiling fan and a mr cool 24k mini split.suggestions are greatly appreciated. Thanks everyone.

Sent from my LGMS210 using Tapatalk

 

[930dreamer]

You need to remove the humidity in that Texas air, I'd go at the minimum a Mr Cool 34K. A ceiling fan will help after the Ac is installed.

 

[CombatNinja]

Metal garage in Texas is hot in the summer!? You don't say.... Your case I believe is going to be one of stopping heat gain rather then one of increasing your capacity to remove it.

When you say it is 'insulated to r10' what does that mean exactly? What type of insulation, how is it installed, etc.

 

[JimNC]

R10 is just enough to say that you have insulation. Chrome the roof and figure out how to get more insulation unless you get free power to run a large air conditioner.

 

[Shiftless]

I seems to me that your 4 big skylights are the big culprit. If you could somehow block those off from above or even from below, you’d have less of a problem. Sunlight pours in and heats up anything it touches.
Park outside on a sunny day and your car gets much hotter than the surrounding air, right?
A garage with big skylights is kinda like a greenhouse.

JimNC is right about adding more ceiling insulation and maximizing reflectivity of the roof. I think white would be just as good or maybe better than chrome. If your ceiling is currently a dark color, that would be one of my first changes.

 

[sleek98]

You pay for insulation once, you pay for cooling every time you turn it on.

I use a 24k mini split to cool (I keep it around 80) my 40x50x12 but I have R30 in the ceiling and R19 in the walls. Is there any way to get the insulation value up from 10 to 30-50 in the ceiling?

 

[Toomanytools?]

Red: Are your ceilings open? Or do you have attic space? You need more insulation up top R 30 minimum, you could try window tint for the skylight cut down some of the heat.
I have about the same space 24x48, 12' of the ceiling that runs the 48' length is 10'6", the other side is raised to peak about 15'. I had a bid for Daikin 24k mini the HVAC guy said it would be plenty. R20 walls, and plan R30 up top. My climate gets 100 degree plus for 2 weeks or so then in the 90's so not Texas hot.

 

[redxiii75159]

Yeah im not sure if i need to just get rid of the skylights or what. But im in a desperate state of mind because i dont know what to do.. Any ideas for the skylights because i also feel that is my problem.

Sent from my LGMS210 using Tapatalk

 

[redxiii75159]

Its a cool 85 degrees outside and this is what im dealing with in the garage.also showing my insulation thickness.

Sent from my LGMS210 using Tapatalk

 

[b-boy]

Can you get a reflective coating put on the glass? That, and a lot of insulation seem like your best bets.

I'm in Buffalo NY. We've had some 90F+weather this year. I can feel for you. It's unbearable to be in a metal building in that type of heat. My pole barn has R21 walls and R40 ceiling. It made a huge difference. It's not cool, but you can work at least in there.

 

[sleek98]

The biggest problem is the sky lights. They are giving you a greenhouse effect. cheap solution would be putting a dark sheet up on the inside just to see the difference.

 

[930dreamer]

Are your skylights clear fiberglass panels or real glass skylights?

 

[redxiii75159]

Clear fiberglass panels

Sent from my LGMS210 using Tapatalk

 

[930dreamer]

I have some on the side walls, could you cover over them with roofing metal or remove them completely?

 

[sms1974]

metal roof panels over the skylights is probably your cheapest fix

 

[redxiii75159]

In order to make it flush i would have to pull off the roof cap but its doable.

Sent from my LGMS210 using Tapatalk

 

[On-Wheel]

I'd get rid of sky lights and think about a drop ceiling if full height wasn't needed,with more insulation.Installing a 3 or 4 ton AC would be my guess if you keep the full height.
Does anyone else put sky lights like that in your area?

 

[redxiii75159]

I asked the company who put the building together about the skylights and they lied to me and said it would not effect much. At the time that is why i did it. Skylights were also a premium charge. Would spray insulation be an option here.? What would you guys suggest for insulation?

Sent from my LGMS210 using Tapatalk

 

[930dreamer]

Spray foam is an expensive option but doable. I'd see about removing the skylights first.

 

[CombatNinja]

Good news is that you have lots of room left for insulation. I would consider rigid foam board with a radiant barrier on that roof. Could you get someone to put heat-rejecting tint on those skylights?

 

[redxiii75159]

No i dont know anyone. but if heat rejecting tint is an option im definately going to explore it.

Sent from my LGMS210 using Tapatalk

 

[JimNC]

Chrome for the roof was a bit of a joke, either white or aluminum will help. Not sure, but painting the skylights would be easier than covering them with sheet metal. Then can you add rigid insulation under the roof or maybe the drop ceiling that someone suggested above.

In the short term just get some air flow going before you pass out in a pool of sweat.

 

[roadrunner255]

I have a 36 x 40 metal building (austin) with 4" insulation in the walls and 6" in the ceilings . 6" stone on 3 sides, 14'3" peak, 11' 8" walls.
I went with 2 18k (1.5 ton) pioneer low end units.
Should have gotten next seer up.
I can keep the building at 76 - 80 deg before the outside temps get above 90.

I also have 3/4" plywood on the interior walls.
An hvac guy suggested the size needed.

Good luck !

Sent from my SM-N950U using Tapatalk

 

[930dreamer]

Could you cover the skylights from the inside?

 

[Falcon67]

You can try coating the roof with this -

https://www.amazon.com/dp/B001B1ANEK/?tag=atomicindus08-20

It's what we use on our race trailers with aluminum roofs. Cut heat gain by quite a bit, 10~20F. To keep that space open you're going to need maybe 3~4 tons of forces air - not a mini, something to really blow. As you now figure, the skylights were a bad idea. Only metal buildings around here with those things are for parking farm equipment and cows.

 

[nomadskidoo]

Spray Foam Over Roof/Of The Sun Area @$2.00 sq ft,should Help close off Sun area.

 

[skippydoo]

https://ezsnapdirect.com/products/exterior-window-shades/
Blocks 90 percent of the heat from entering the building and you can easily remove in the fall for better light in the building.

 

[redxiii75159]

I checked out the ezsnap page... I have a corrugated roof so im not sure this would work. And ive already ordered a mr cool 36k along with two ceiling fans

Sent from my LGMS210 using Tapatalk

 

[redxiii75159]

If im doing my math correct i have a 24 by 40=960 sqft. multiply sqft by 30 because its a main floor = 28800. Then add 1000 to every ft of ceiling height over 8ft. I have a 12 ceiling ht with 15 foot peak so i would add 7000 because of 15 foot peak to be on the safe side. Thats 35,800 btu to adequately cool the building provided i rid my skylights correct? So wouldnt a 36k btu Be enough with two ceiling fans be enough? Please correct me if i have missec something. Ps loving all the suggestions.

Sent from my LGMS210 using Tapatalk

 

[redxiii75159]

Also to add i still have the old 18k btu thru the wall unit as well to help what you guys think?

Sent from my LGMS210 using Tapatalk

 

[jjtrou2072]

I'm following this closely as I have a 30X40 garage space inside my metal building I need to condition as well. While I don't have skylights in my space, I do have tall ceilings (16' Eave with 20'+Peak). I'm in Georgia so Mid 90's with ridiculous humidity is pretty common here in summer.

I am planning on a Mr. Cool 36K Btu for my space. I'm no professional but I think you should be fine with the 36K. However some on here will disagree with using ceiling fans in summer. There is an idea that the air will stratify with the cooler air staying lower in the building. Definitely keep us informed how it performs.

 

[GrayFlattop]

For a short-term fix, why not try what they use at commercial greenhouses in the summer? In the old days they would apply whitewash, but whatever you want to use - it could be a quick and inexpensive way to get short-term results.
https://www.greenhousegrower.com/technology/equipment/keeping-cool-with-greenhouse-shading/

Other options would be to have a reflective commercial window tint applied, but if the overall objective is to have more insulation up there, insulation either goes on the inside or the outside. Just last month, a friend had very good results with a room that would never stay cool in the summer. He had the roof (an addition with a shed roof) covered with 4 or 5" SIP panels and then a new shingle roof applied over it (aluminum flashing details at the edges). You could do something like this - just pave over the skylights with the SIP and have a new metal roof applied on top. https://raycore.com/insulated-roof-panels-wall-panels/?gclid=CjwKCAjwwdTbBRAIEiwAYQf_E-4pD2E0wEV2Xazd0Ky9Nn2zV7cCfKyGi_PWLER7YO1Irns986hDoRoCMIgQAvD_BwE

 

[sleek98]

The temp near the 12' portion of my ceiling is normally 5* higher than eye level, and the temp at the 16' level, I have coffer truss, is usually 10-12* higher than eye level. I keep it at 82 all the time when I am not out there. It will be 87-90 at the 12' portion of my ceiling and near 95 over the 2 post lift where the ceiling is 16'. I can only imagine that having fans would push the heat down and make the ac work harder. I have not added fans yet, plan is to put them in before winter.

 

[redxiii75159]

Ok update im having skylights completely removed with insulation added. Hopefully this should help. I get it done hopefully this Wednesday 4-17-19. Ill will let you guys know how it works out. Btw the 36k mrcool unit works wonders heating and cooling. It shall be even better after skylights are removed.

Sent from my LGMS210 using Tapatalk

 

[strutaeng]

Glad to hear you found a solution. Can you just insulate the skylights from below as it was already suggested? Maybe box them in and insulate. That way if you ever need more light, just remove the insulation?

Which system did you install? Was a DIY installation?

I'm looking at cooling a similar space as yours 23'x44'x17' high (house addition), but insulation for a home (R19+5 walls and R38 ceiling.) Based on on-line calculators, it say I need around 20kBTU, so was thinking a 24kBtu would work.

 

[theoldwizard1]

R10 is just enough to say that you have insulation.

In Dallas, you could not afford the electricity to run the A/C required to cool that building !

You need R30-R40 in the roof. That is about 6" of poly-iso or closed cell spray foam. Probably 3" in the walls. I would spray foam. Expensive, but it seals all of the small gaps.

Then you some way to shade the sum coming through the skylights.

Once you have proper insulation a second 18K A/C window unit will get you in to the "tolerable" range.

 

[redxiii75159]

Glad to hear you found a solution. Can you just insulate the skylights from below as it was already suggested? Maybe box them in and insulate. That way if you ever need more light, just remove the insulation?



Which system did you install? Was a DIY installation?



I'm looking at cooling a similar space as yours 23'x44'x17' high (house addition), but insulation for a home (R19+5 walls and R38 ceiling.) Based on on-line calculators, it say I need around 20kBTU, so was thinking a 24kBtu would work.

Thought about the insulation from below idea but those skylights condensate so much during the night when its cool and that would just be a mold nightmare. Besides these skylights only last about ten years then you have to replace them.

Sent from my LGMS210 using Tapatalk

 

[redxiii75159]

In Dallas, you could not afford the electricity to run the A/C required to cool that building !



You need R30-R40 in the roof. That is about 6" of poly-iso or closed cell spray foam. Probably 3" in the walls. I would spray foam. Expensive, but it seals all of the small gaps.



Then you some way to shade the sum coming through the skylights.



Once you have proper insulation a second 18K A/C window unit will get you in to the "tolerable" range.

I believe you may be right my friend as far as insulation goes. This will be my next move in the future. Does polyiso have some sort of adhesive backing because i really cant apply it unless it sticks to the roof. If it doesnt it looks like spray foam will have to do.

Sent from my LGMS210 using Tapatalk

 

[strutaeng]

I believe you may be right my friend as far as insulation goes. This will be my next move in the future. Does polyiso have some sort of adhesive backing because i really cant apply it unless it sticks to the roof. If it doesnt it looks like spray foam will have to do.

Sent from my LGMS210 using Tapatalk

How deep are the purlins? 6, 8, 10"? You can fill the purlin space with fiberglass, then install some 1x strapping perpendicular to the purlins and screw 4x8 sheets of polyiso, with seams taped with the Tyvek tape. Fitting the polyiso between the purlins is okay, but putting a full layer of continuous insulation below it will reduce the purlin "thermal briding."

Read this article.
https://www.greenbuildingadvisor.com/article/cut-and-cobble-insulation

While, you can insulate between girts (or rafters for that matter) with rigid insulation, I think it is easier and cheaper with fiberglass. Save the rigid for the continuous layer, as it is more expensive.

This is way cheaper than spray foam, and can be a DIY project. Use the money saved to add more insulation if you want to.

 

[slimcake]

So how did you turn out with the roof and how is the 36k doing??