Comparing spray foam to batt insulation in my garage was a real eye opener after one winter

I did a garage reno last fall and went with spray foam on one side and traditional batt insulation on the other to see what would actually hold up better. After this brutal Edmonton winter, the difference is crazy. The spray foam side stays way more consistent temperature wise, even when it hit -35 last month. The batt side had some settling and a few spots where mice got in through the vapour barrier. I spent about $800 more on the spray foam for a two car garage, but honestly I think it's worth it for the air sealing alone. Has anyone else tried mixing insulation types like this or did you just pick one and hope for the best?

2 comments

2 Comments

martin.felix1mo ago

Good for you doing a side by side test like that. I did the same thing with my workshop out back a couple years ago and got almost identical results, the spray foam side just feels tighter and more comfortable no matter what the weather is doing outside. The mice issue you mentioned is a big one, I had voles chewing through my batts and nesting in there before I even finished the project. That extra money for spray foam hurts upfront but you are absolutely right about the air sealing being the real game changer, especially in a garage where you want to keep the cold and critters out. Seems like mixing them is a smart way to see for yourself what works best in your specific space.

thompson.nathan1mo ago

That reminds me of something I read from Building Science Corporation a while back, where they pointed out that most heat loss in a building comes from air leakage, not the insulation material itself. Your side by side test really proved that theory out in practice. The fiberglass batts can work fine if they are perfectly installed with a dedicated air barrier, but most folks just don't have the time or patience to get that level of detail right. Spray foam does the air sealing automatically, which is why you feel that difference even if the R value is technically similar. The rodent thing is another example of the same advantage, since there are no gaps for them to squeeze through and no fluffy material to chew up for nesting.