Garage insulation

[gfmucci]

Central Florida 1.5 car garage (12' x24' x8') surrounded by interior walls on 3 sides with insulated metal garage door facing south.

Attic temps are typically +100 to 120+. While the attic over the garage has 5 or 6 inches of blown insulation, there still seems to be too much radiated heat from the ceiling.

I have an 8,000btu ac in the garage that barely achieves a 10 degree cool down below outdoor temps.

Questions:
1) Would it be worthwhile to blow another few inches of insulation in the attic?

2) The metal garage door insulation is the thin adhesive metal backed foam mounted on the struts. Would it help to blow insulation into the 2" voids between the metal door and the stick-on insulation?

 

[gfmucci]

Central Florida 1.5 car garage (12' x24' x8') surrounded by interior walls on 3 sides with insulated metal garage door facing south.

Attic temps are typically +100 to 120+. While the attic over the garage has 5 or 6 inches of blown insulation, there still seems to be too much radiated heat from the ceiling.

I have an 8,000btu ac in the garage that barely achieves a 10 degree cool down below outdoor temps.

Questions:
1) Would it be worthwhile to blow another few inches of insulation in the attic?

2) The metal garage door insulation is the thin adhesive metal backed foam mounted on the struts. Would it help to blow insulation into the 2" voids between the metal door and the stick-on insulation?

Despite no responses to this question, I am having another 6" blown in to my garage attic. I'll report after awhile. Any other comments certainly encouraged.

Oh, and the insulation firm said adding anything else into the garage door void between the existing foam and the metal won't accomplish anything except lightening my wallet.

 

[billconner]

Cellulose is better at blocking radiant transfer than fibreglass. Not sure what you have or are adding.

 

[Showkey]

As a side note…….Think your way under estimating attic temperatures.

So yes…….more insulation will improve cooling. Thats also a big ask for 8000 btu in Florida heat and humidity.

This guy is selling attic power vents…….but…….his 160* is not far off.

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[gfmucci]

Cellulose. I've never seen the attic temp above 130F. Typically tops around 120. Yes. It is a big ask of the 8,000 BTU unit. Takes the temp down around 10 degrees below ambient. Hoping with the added insulation it might come down 15 degrees.

 

[welder4956]

I'm not sure what you mean by "interior walls on 3 sides". Are those walls adjacent to interior rooms that are cooled by the house AC, or are they just covered by dryall? If those walls are along the outside of the house and are not insulated, that may be another source of heat transfer. You could open a hole at the top of each stud bay and blow in insulation if there is none.

 

[gfmucci]

I'm not sure what you mean by "interior walls on 3 sides". Are those walls adjacent to interior rooms that are cooled by the house AC, or are they just covered by dryall? If those walls are along the outside of the house and are not insulated, that may be another source of heat transfer. You could open a hole at the top of each stud bay and blow in insulation if there is none.

2 sides ac space, 1 side behind masonry block wall is neighbors garage. Block remains coolish. The only outside space is behind the garage door.

 

[Ak Jim]

Is there a published R value of the door? You might want to consider a different door. You can go all the way up to R-17 or so. Sounds like most of your heat is coming thru the garage door.

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[welder4956]

One other thing to check is whether the garage attic space is vented. Make sure there are enough soffit vents and either ridge vent or roof vents to keep hot air from building up in the attic space. You need at least 1 sq ft of vent for every 300 sq ft of attic space, but preferably more than that. 1 sq ft of vent per 150 sq ft of attic space would not be too much.

 

[Showkey]

Cellulose. I've never seen the attic temp above 130F.

Did you measure the bottom side of the roof decking ???