Projecting Wall Insulation Value by Garage Interior wall temp

[Flash21]

Hi all - I'm in Zone 4 marine

Garage is an attached 37x24x9. There is heated living space covering ~3/4 of the garage. All garage walls are drywalled from original 1990s construction. Garage doors are uninsulated wood.

I'm planning on adding heating (A/C not required) to my garage.

I've read some articles and threads on how to check whether my walls are insulated but don't really want to cut holes in the drywall and the electrical boxes didn't provide any insight. I assume the ceiling is insulated.

Question is: Can I use an infrared thermometer to measure the various spots on the interior garage walls and compare to the exterior temperature to extrapolate what my wall insulation "r" value is? If so - what is the transfer function?

In the winter, the garage stays consistently ~20 degrees above exterior without the doors opening and closing. (i.e. 25 degrees outside, garage is ~45 degrees) I have a natural gas fired forced air furnace in the garage to heat the house, there are some short runs uninsulated ducts so that would give a very minor bump in temperature in the garage. Plus the heat loss from the room above and the one short run of shared interior wall with the house.

thanks for the help - I'll use the data to know whether i need to tear out and insulate and use it for heat load calculators.

 

[Kaizen]

No. Too many variables. Thickness of rock. Mil of vapor barrier. Etc. garage door is probably biggest heat loss.
If you have walk cabinets you can take one down and cut hole behind


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[Vahispd]

+1 on the no. Other variables include how well the insulation (if present) was installed, air sealing of sheathing penetrations and sill etc.

Are there other houses nearby that were built when yours was? Maybe those neighbors have had a wall open and can provide some info on what the builder installed in their house?
You can contact your local building code folks and ask what the minimum insulation code was when your house was built. That may give you a starting point for an R-value or if insulation was required.
The exterior wall of my attached garage had pegboard installed - great I thought! I discovered the pegboard was screwed directly to the studs and the wall was not insulated; the city code office stated the wall did not need insulation because it is not a living space.

An IR thermal imager is the better tool for your situation. You may be able to use the IR thermometer to guess whether the garage wall is insulated by checking wall surface temps in the house and garage and comparing the results, but there are likely several factors that make this unreliable at best.
My house was built in 2005, basic tract house to minimum code (mostly). I just checked and the surface temps of the drywall inside my house ranged from 63-67 degrees F depending on interior/exterior wall, proximity to doors/windows etc. Air temp in the house is ~69 degrees F and the outside temp is 53 degrees F.
Surface temps of the drywall in the garage were 63-64 degrees F. Garage air temp is 65 degrees F. I have part of the exterior wall opened up for an electrical upgrade and the back of the sheathing is 57 degrees F.

Not sure if that helps any.

 

[jbwilkins]

1990's construction would normally equal no insulation in a garage.

If you're sure there's something there, then 2x4 walls woudl be ~R-11 and 2x6 would be ~R-19, floor above an unheated space could be ??? (maybe R-19). You should be able to get a idea of the wall thickness by looking at and penetrations (windows/doors) and the thickness of the jambs.

Oh, and the garage being 'warmer/cooler' than the outdoors means very little. Since it's attached it's affected by the conditioned walls/rooms above. Their could also be a ton of leakage into the grarage from the house.

 

[Flash21]

OK - thanks for the great comments and input. I'll investigate more and if I can't determine by other means, I'll cut a hole.

 

[Vahispd]

I've drilled holes in drywall and had a bit of fiberglass insulation wrap around the drill bit if I went too far into the wall. Not the ideal way to check for insulation, especially if you have a vapor barrier, but it's another option.

 

[Ralf11]

you can get a +/- estimate from the gradient in temp.

the main source of insulation is the ... ah... insulation

sheet rock, lumber R values can be looked up but are low resistance to heat flow

measure near the center of the wall, away from any doors/windows

 

[Flash21]

Yeah, I might just grab some test data in the middle of the wall -- try and hit it between two studs for the sake of data. Will report back on what I find.