If you are using a tent buddy.
To say yourself hassel why not just use a 40$ filter that will get you through the few months of growing needed.
As with such cold temps, if you do stick to the garage you'll have to make it so, that when it goes into lights off, (that it'll be the warmest part of your day) especially in pre flower, you want to keep your temps in a 4-5c range or you'll have excess stretching.
And, there's 1 more way you can do it. Without having to install any foam or heating.
Get a cheap co2 exhale bag.
And put on your timer, so your exhaust, (intake fan) comes on every 5 mins out of 30 just to lower your RH, this will keep up your temp without too much trouble.
And with the added co2 it'll allow you to grow in hotter/ higher rh environment.
Good luck.