Insulation

[Patrick Casey]

Hi,

I am new to this forum and metal buildings in general.

I recently had a 24 X 36 metal garage built. I am looking at insulating it. The plan is to put a mini split in it at some point.

My heating and cooling objectives are
- keep it above freezing in the winter (at night)
- Temperature of 55 to 60 in the day
- not hotter than 80 in the summer

TBH I am questioning my wisdom in not having the insulation installed on the exterior side, between the uprights and the outer skin.

Has anyone here got experience with Prodex Total Plus 10mm from InsulationForLess?
The recommended installation for my situation has the product being attach to the inner side of the structural uprights and roof spars. The claim is R22. It is closed polyethylene foam covered with reinforced foil. The claim is R-22.

I would be covering this with OSB attached to furring strips.

It seems pretty minimalist.

Thoughts on this approach?

 

[shade]

Interior insulation then OSB then a final outer if desired such as drywall, metal liner panel, etc
I wouldn't do OSB but thats just a personal preference

 

[regguy1]

Hi,

I am new to this forum and metal buildings in general.

I recently had a 24 X 36 metal garage built. I am looking at insulating it. The plan is to put a mini split in it at some point.

My heating and cooling objectives are
- keep it above freezing in the winter (at night)
- Temperature of 55 to 60 in the day
- not hotter than 80 in the summer

TBH I am questioning my wisdom in not having the insulation installed on the exterior side, between the uprights and the outer skin.

Has anyone here got experience with Prodex Total Plus 10mm from InsulationForLess?
The recommended installation for my situation has the product being attach to the inner side of the structural uprights and roof spars. The claim is R22. It is closed polyethylene foam covered with reinforced foil. The claim is R-22.

I would be covering this with OSB attached to furring strips.

It seems pretty minimalist.

Thoughts on this approach?

ai response: Your skepticism is completely justified—and your instinct that this setup feels "pretty minimalist" for heating and cooling a standalone metal building is spot on.

The Truth About the "R-22" Claim​

The advertised R-22 rating is a marketing assembly calculation, not the physical material value.

• A 10mm (~3/8 inch) piece of polyethylene foam itself only provides a true conductive R-value of roughly R-1.5 to R-2.
• The "R-22" claims come from testing the product inside a sealed cavity with large trapped air spaces on both sides, specifically measuring downward heat flow (summer ceiling radiation).
• In winter, heat flows up and out through the roof and horizontally through the walls. Reflective radiant barriers do very little to stop conductive or convective heat loss in freezing weather. If you try to keep the garage at 55–60°F on a 15°F winter day using only 10mm of foam, a mini-split will run non-stop, struggle to keep up, and send your electric bill through the roof.

Thermal Bridging & Your Frame Choice​

You mentioned questioning whether you should have placed insulation on the exterior side (between the steel framing and the metal siding).
Installing a thermal break (like fanfold foam or thin reflective roll) over the exterior of the girts/purlins before the sheet metal goes on is ideal for stopping thermal bridging and condensation. However, doing so still would not have provided enough mass R-value to heat the space in winter—you would have needed interior cavity insulation regardless. So, you didn't miss out on a complete solution, just a thermal break.

A Proven Interior Retrofit Plan​

Because you want real temperature control (55–60°F in winter, sub-80°F in summer) and plan to install OSB walls over furring strips, here is how to build an effective assembly:

1. Use the Prodex as a Vapor/Radiant Control Layer (Optional)
   • If you've already bought the Prodex, strap it across the face of your metal uprights/roof spars, taping every single seam with foil tape.
   • This provides a radiant barrier for summer heat and acts as an air/vapor seal to prevent interior humidity from hitting cold steel.
2. Add Real Mass Insulation (Essential for Winter Heating)
   • Build out standard wood framing (2x4 or 2x6 wall framing/studs) or horizontal furring strips inside the metal frame.
   • Fill the cavity with unfaced mineral wool (Rockwool) or fiberglass batts (targeting R-13 to R-21 in the walls, R-21 to R-30 in the roof).
3. Finish with OSB
   • Fasten your OSB to the wood framing/furring strips.
   • The wood framing decouples the cold outer steel shell from your interior OSB, eliminating the thermal bridge and giving your mini-split a tight, holds-temp envelope.

Recommendation​

Do not rely on 10mm reflective foam alone if you intend to condition the garage during cold winter months. Treat the Prodex purely as a vapor barrier and radiant skin, and back it up with standard bulk insulation (batt or spray foam) before hanging your OSB wall panels.

 

[couch67]

welcome. yeah 10mm (3/8") of foam will not yield much R-value. Rigid foam board is about R5 per inch.

what is your location - that will help others with giving better help.

 

[WildBill]

I have a 24x36 metal shop with BlueTex 2mm radiant barrier and no insulation. I put it over the frame before adding the sheet metal. I run a 24k Mr.Cool minisplit. It gets from -20 to 100F here. The Mr.Cool is great in the summer and has no issue getting it as cold as I want very rapidly, for very little energy cost, but its not ideal in the winter with no insulation. While it will keep my shop warm its really inefficient below about 35F when it starts freezing up and has to reverse to defrost itself. I supplement it with a $80 Chinese diesel heater.

BlueTex makes no crazy claims and points out its material is a radiant barrier, not insulation. As a radiant barrier and for sealing up the building against drafts its great, I measured something like a 30F wall temp difference when testing it with/without during the build, it very much reduces temps in the summer. My nephew who was helping put the shop up was wrapping himself in it to stay cool. I also really like the heavy duty clean white interior material, you can hose it off if needed and makes for a nice bright shop.

R22 for the Prodex stuff is a lie. BlueTex calls mine R1 at best, and makes it very clear its not designed to be insulation. They have a lot of good videos and info about foam/foil material.

Metal Building Insulation | BlueTex Insulation

BlueTex Insulation provides insulation on metal buildings of all types, from metal garages, workshops, barns to airplane hangars. Explore our products and services. Also, garage door insulation kits and vapor barrier tapes.

bluetexinsulation.com

 

[Patrick Casey]

I am in Richmond, Va. It is pretty hot in the summer and moderately cold in the winter.

The building is white

welcome. yeah 10mm (3/8") of foam will not yield much R-value. Rigid foam board is about R5 per inch.

what is your location - that will help others with giving better help.

with a galvalume roof. So that will reflect heat.

I have a 24x36 metal shop with BlueTex 2mm radiant barrier and no insulation. I put it over the frame before adding the sheet metal. I run a 24k Mr.Cool minisplit. It gets from -20 to 100F here. The Mr.Cool is great in the summer and has no issue getting it as cold as I want very rapidly, for very little energy cost, but its not ideal in the winter with no insulation. While it will keep my shop warm its really inefficient below about 35F when it starts freezing up and has to reverse to defrost itself. I supplement it with a $80 Chinese diesel heater.

BlueTex makes no crazy claims and points out its material is a radiant barrier, not insulation. As a radiant barrier and for sealing up the building against drafts its great, I measured something like a 30F wall temp difference when testing it with/without during the build, it very much reduces temps in the summer. My nephew who was helping put the shop up was wrapping himself in it to stay cool. I also really like the heavy duty clean white interior material, you can hose it off if needed and makes for a nice bright shop.

R22 for the Prodex stuff is a lie. BlueTex calls mine R1 at best, and makes it very clear its not designed to be insulation. They have a lot of good videos and info about foam/foil material.

Metal Building Insulation | BlueTex Insulation

BlueTex Insulation provides insulation on metal buildings of all types, from metal garages, workshops, barns to airplane hangars. Explore our products and services. Also, garage door insulation kits and vapor barrier tapes.

bluetexinsulation.com

I was looking at the BlueTex site. Their claims seem a little more down to earth. The reality is that I just want the temperature to be warm enough not to freeze my pressure washer in the winter (at night) and bearable on a winter date, and cool enough in the summer that I can close the doors so I don't have to swat mosquitos.

Some sound deadening would be nice too - but that seems a bit more involved.

 

[WildBill]

I am in Richmond, Va. It is pretty hot in the summer and moderately cold in the winter.

The building is white


with a galvalume roof. So that will reflect heat.


I was looking at the BlueTex site. Their claims seem a little more down to earth. The reality is that I just want the temperature to be warm enough not to freeze my pressure washer in the winter (at night) and bearable on a winter date, and cool enough in the summer that I can close the doors so I don't have to swat mosquitos.

Some sound deadening would be nice too - but that seems a bit more involved.

Your weather is way less extreme than mine, you would probably be fine with any decent radiant barrier and a mini split. Obviously more insulation would be better, but I haven't been able to justify it vs my very inexpensive cooling and heating costs. Even in July when it sits around 90-100F here it only costs about $50 to keep my shop at 68F for the month. I like it on the cool side. A mini split will really help with the humidity as well, my shop stays 30-40% humidity year round.