Insulating the garage attic.

CZ4diy · 11-10-2010, 10:30 AM

Is it worth insulating the attached garage attic? I'm looking to keep temps a little less extreme. I live in SE Michigan where winter temps average 15- 20 degrees F and can get up to 90 degrees F during the summer. Currently the temps in the garage are holding 10 degrees +/- ambient. When it was 2 degrees, it was 19 in the garage. And that's because I've insulated the door with a fiberglass kit. The house was constructed in 2000. It has the typical firewall with fiberglass batt on the 1 1/2 walls it shares with the house. The rest of the walls are exterior and bricked. One double pane window facing north.

My intention is to overwinter potted trees and less than hardy plant material. Am I going to get any better (warmer) results with attic insulation?

Second question: What about moisture? I'm already experiencing problems with the door panels freezing shut with condensation now that it's insulated. Any thoughts here?

urbano · 11-10-2010, 12:57 PM

Can I put thin plywood over attic rafters and then put the insulation on top of this? I will not use the attic. There would be a dead air space between attic florr and the room cieling

240sx4u · 11-10-2010, 01:43 PM

Quote:

Originally Posted by CZ4diy

Is it worth insulating the attached garage attic? I'm looking to keep temps a little less extreme. I live in SE Michigan where winter temps average 15- 20 degrees F and can get up to 90 degrees F during the summer. Currently the temps in the garage are holding 10 degrees +/- ambient. When it was 2 degrees, it was 19 in the garage. And that's because I've insulated the door with a fiberglass kit. The house was constructed in 2000. It has the typical firewall with fiberglass batt on the 1 1/2 walls it shares with the house. The rest of the walls are exterior and bricked. One double pane window facing north.

My intention is to overwinter potted trees and less than hardy plant material. Am I going to get any better (warmer) results with attic insulation?

Second question: What about moisture? I'm already experiencing problems with the door panels freezing shut with condensation now that it's insulated. Any thoughts here?

I am not sure about the moisture, sorry. I am in southern WI and it gets pretty cold here too. I have insulated walls and did blown insulation last winter. Made a big difference in how warm the garage stayed. Mine is heated with a modine hot dawg as well.. so it never gets below 45. The heater cycles VERY infrequently with the new attic insulation.

jklingel · 11-10-2010, 11:05 PM

"Heat goes to cold. Period." Insulation slows the process, so absolutely insulate the lid. I assume you will insulate the walls, too (if they are not already so). Putting boards over the trusses will defeat the purpose somewhat. Dead air is not a great insulator. Blow cellulose into the spaces and save yourself the time and money of installing paneling; you'll get a better insulation up there, too. Blow as much cellulose as is recommended for your area (plus 2", if it were me), but make sure your sheet rock can support the extra load. 1/2" 'rock, 24" OC will not support a ton of insulation; sorry, but I don't have the numbers, so see an good builder or engineer. Likely, a city engineer can answer that in 2 seconds, and free. Then, what about a vapor barrier? Recommended for your area? If none is recommended, then do whatever it takes to install an AIR barrier. That may mean re-doing the sheet rock to specs, or, worst case, tearing it out and re-doing it. If demolition is not your thing, then perhaps a vapor retarding paint will help.