Prefab metal garage insulating and cooling question

mk77 · Mar 20, 2017

I've been looking through the forums the past week and I finally decided to make an account today. I know there are tons of metal building insulation and condensation questions on here, but they all vary and don't specifically answer my questions. I'm planning to build a 24'x30' prefab metal garage on a concrete slab. The building will be used as a race shop. I live in North Carolina so humidity and condensation is my main concern. My buddy has the same building with the bubble insulation and during the winter and when it rains during the summer everything is soaking wet. (BTW his shop is not heated nor cooled and doesn't have any exhaust fans/vents.)

My plan is to insulate it well and I want to sheet the walls and roof, so I can heat and cool it fairly easy. (If I get it insulated well, I think I can efficiently cool it with a good size window unit.)

The bubble wrap insulation doesn't seem to be effective from what I have seen in my buddy's shop. Since the garage will not be heated and cooled 24-7, I've thought about putting vents in the walls near the roof and installing an exhaust fan with a humidistat.

My questions are:
- Since it is a metal building that does tend to cause condensation with temp changes what is an alternative insulation that won't mold if it happens to get moist?
- Do you think the automatic exhaust fan will help with humidity so I am able to sheet the roof and walls?

Thanks for your input. I know it a lot and chopped up but it's just difficult to explain everything haha.

Barnabas · Mar 20, 2017

I just bought a steel-walled warehouse in North Carolina and have been ripping out the rotted lumber and pink fiberglass insulation. What were they thinking? &#55357;&#56398;

I do know that any wood that touches the metal walls or concrete floor will be treated lumber. I am also researching insulation options.

2nr · Mar 20, 2017

I am currently underway for my metal building. My garage will have heat but no cooling. I am locating a good quality spray foam insulation. I will be incorporating ventilation but my slab I what I am heating.
That's my 2 cents!

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andersen24 · Mar 20, 2017

For what it's worth, my neighbor has a 1600 sq foot metal shop and turned me onto this product. His walls and roof are insulated with their products and I was blown away with the difference. I have a 1200 sq foot metal shop and it is a night and day difference. I haven't pulled the trigger yet as there are other higher priority projects I have. He's an aeronautical engineer (propeller head) and researches the HECK out of everything. Plus it doesn't hurt that his company used the same material (not the same company though) and its a 100,000 sq foot facility. I am curious to hear if someone has done the spray insulation. But price wise, I like the potential of this.....

http://www.insulation4less.com

and no - you can look at my previous posts, I don't work for them or know anything about them - just giving information!

brownbagg · Mar 20, 2017

i bought a used hotel heat pump that heats and cools. I just put it in the doorway and drop the door on top of it, move it in storage when i dont need it

mk77 · Mar 21, 2017

andersen24 said:
For what it's worth, my neighbor has a 1600 sq foot metal shop and turned me onto this product. His walls and roof are insulated with their products and I was blown away with the difference. I have a 1200 sq foot metal shop and it is a night and day difference. I haven't pulled the trigger yet as there are other higher priority projects I have. He's an aeronautical engineer (propeller head) and researches the HECK out of everything. Plus it doesn't hurt that his company used the same material (not the same company though) and its a 100,000 sq foot facility. I am curious to hear if someone has done the spray insulation. But price wise, I like the potential of this.....

http://www.insulation4less.com

and no - you can look at my previous posts, I don't work for them or know anything about them - just giving information!

I think that the foil fiberglass insulation that they offer would definitely be better than the bubble insulation.

73RR · Mar 21, 2017

Spray foam may be your best solution. No, not cheap initially, but long term pays dividends.
This may help: http://www.vaisala.com/Vaisala Documents/Application notes/PreventingCondensation.pdf

readhead · Mar 21, 2017

Spray foam is starting to show up problems with premature rust thru of sheeting and structural components.

73RR · Mar 21, 2017

It is generally not a good idea to spray the exposed metal roofing for several reason. If structural iron is showing problems I'd guess that the foam is not thick enough to stop condensation.

forAK · Mar 21, 2017

73RR said:
It is generally not a good idea to spray the exposed metal roofing for several reason. If structural iron is showing problems I'd guess that the foam is not thick enough to stop condensation.

Or it was open cell with no vapor barrier.

readhead · Mar 21, 2017

The problems showing up don't seen to vary from closed to open cell. We are noting in our contracts that any and all warranties are void if spray foam is installed.

jcthorne · Mar 21, 2017

If the shop is not used every day, its entirely possible that its far cheaper to just leave the metal building un-insulated and oversize the heat and air systems to compensate. Real insulation installed properly in a metal building is not cheap or easy. Since my heating days are less than 20 a year and cooling days less than 40, we decided to go this route. Costs roughly a couple bucks a day to heat or cool. Would not make sense if we used it all the time. The building was also not new construction so moving everything including equipment out of it factored into the cost of insulation.

Lots of folks will disagree with me. It was not the 'green' answer but was the most cost effective and works for us.

TractorJeff · Mar 21, 2017

I've worked in metal construction buildings that are insulated and there have not been issues with longevity that I know of. Most times Internal rain is related to the building not being opened up often enough for the air to exchange and the outdoor heat to get in and warm up the items stored inside.

73RR · Mar 22, 2017

forAK said:
Or it was open cell with no vapor barrier.

Contrary to popular belief....open cell is a vapor barrier.
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http://www.energsmart.com/spray-foam-insulation/open-vs-closed-cell-foam.html

73RR · Mar 22, 2017

readhead said:
The problems showing up don't seen to vary from closed to open cell. We are noting in our contracts that any and all warranties are void if spray foam is installed.

That seems a bit extreme. Do you also control their diet?

readhead · Mar 22, 2017

Sure, if they are eating spray foam. Do you have anything useful to offer?

forAK · Mar 22, 2017

73RR said:
Contrary to popular belief....open cell is a vapor barrier.
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Negative. Well maybe if Google is wrong..... Try this: "is open cell spray foam a vapor barrier"

73RR · Mar 22, 2017

forAK said:
Negative. Well maybe if Google is wrong..... Try this: "is open cell spray foam a vapor barrier"

http://www.energsmart.com/spray-foam-insulation/open-vs-closed-cell-foam.html

I guess that we all believe what we want to. The real deal is that we should use what works in our specific geographical location.

Prefab metal garage insulating and cooling question

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