Garage ceiling insulation and possibly walls

[lalojamesliz]

I've been spending a lot of time working on my 69 mustang and recently got a 12k split system ac unit. On days that's its under 104 I can keep the garage at 78 but the ac isn't able to rest.

Would insulation for the ceiling really help?

It's a 2 car garage connected to my home on the garage back wall and the sun hits my garage door all day. The walls and ceiling have drywall but no insulation. I've considered removing my wall drywall, adding insulation and re-drywall but easier said than done.
I had to cut a acces hole to get in the garage attic when i had solar panels installed and I've climbed up a few times for some wiring additions.
Im just trying to see what I can do to my garage to insulate it better. It gets in the mid 30's and sometimes in the 20's during winter so keeping the heat in is also a plus then.

Right now all I have is 2" foam board on my garage door.
This is the current step for my car but even after I finish my car (yeah ok...) I'm always working on something in my garage. So it was a matter of time before I got to adding a ac unit

 

[billconner]

Seems perfect application for blown in cellulose. I think it would make a world of difference. Enough loose in attic so it is 12" when it settles. You can dense pack the walls - just use a hole saw near top and tube cellulose in. You'll want a blower with an airlock and may want to buy a smaller tube. Feed it into wall cavity and start blowing - very lean air to cellulose - and withdraw tube as it starts to plug up. You'll get the hang of it after a cavity.

It would be easy to keep it comfortable.

 

[lalojamesliz]

Seems perfect application for blown in cellulose. I think it would make a world of difference. Enough loose in attic so it is 12" when it settles. You can dense pack the walls - just use a hole saw near top and tube cellulose in. You'll want a blower with an airlock and may want to buy a smaller tube. Feed it into wall cavity and start blowing - very lean air to cellulose - and withdraw tube as it starts to plug up. You'll get the hang of it after a cavity.

It would be easy to keep it comfortable.

You think it would make that much difference from now?
So near ceiling height cut a hole and just fill right. I'll look for horizontal 2x4's and if i find any ill just make another hole below them.
I'll look into it. Thank you

 

[billconner]

I think your split system will rest a lot. Just doing ceiling will make a big difference. Seal as many holes and penetrations in it as possible - caulk or foam around pipes and wires and such. Convection - just air passing through and out - is biggest looser, then radiation (I'll bet it's sweltering in attic space on sunny days - the roof deck just radiating heat) and then conduction. But the cellulose will help with convection and definitely block a lot of radiant heat, as well as minimize conduction, especially if over lower truss chord or ceiling rafter.

Attic is easy, so maybe do that first and see if it's good enough, but walls will reduce drafts and save energy.

 

[CombatNinja]

If I understand your setup correctly, I think your comfort gains would go in this order:

1. Insulated garage door
2. Insulation in the ceiling
3. Insulation in the walls

This is also reflective of cost in most expensive to least. I look at #2 as being the sweet spot and where I would start.

 

[Bucko]

If I understand your setup correctly, I think your comfort gains would go in this order:

1. Insulated garage door
2. Insulation in the ceiling
3. Insulation in the walls

This is also reflective of cost in most expensive to least. I look at #2 as being the sweet spot and where I would start.

Air leakage is one of your biggest enemies with a controlled climate and should be addressed as well. I would also look at making sure there are no penetrations in the ceiling and your garage door seals are intact. The door will be difficult to seal up but mitigating other areas will slow the movement of cool air being sucked out. Caulking around outlets and making sure any attic hatch is sealed. I've made boxes out of the foamboard that sat over the attic stair access in my old home. Made a notable difference in temp at the hatch when tested with a temperature gun.

 

[acer66]

I got r38 in the ceiling and the walls are unfilled cinder blocks, the south facing garage door has 1&1/2” foam boards.
It is amazing how cool it stays with these insane temps right now even with no ac running.

 

[My Old Tools]

Most of your heat gain is through the roof. Insulating the attic is the biggest pay back, west and south walls would be next, north wall for winter.

 

[lalojamesliz]

Most of your heat gain is through the roof. Insulating the attic is the biggest pay back, west and south walls would be next, north wall for winter.

I should have explained it like that.... my garage door faces south so it gets sun all day. My east wall gets the morning and my west wall gets the evening.
My north wall is connected to my home and has a metal type of Framing and I'm guessing that's to help prevent driving through it.

To get the cellulose sprayer free rental I need to buy 20 bags. According to some calculator for that insulation I only need 9 for my ceiling.

I'll have to see if it's better to buy the 11 extra to get the free rental or to just buy 9 total and pay for the rental

Or I can work something out with a friend.....

 

[The Cobbler]

as mentioned, the biggest heat gain is thru the roof.
my circa 1950's home had r-8 to r-12 in the attic . I upgraded to about r50 If I remember correctly about 12 years ago .
the old Ac would run continuous and shut off in the middle of the night and cycle . the new AC installed at the same time ( same size) cycles on even the hottest days and never struggles to have a 25°f differential . with the old AC & insulation, it would struggle with a 18° to 20° differential

 

[racecougar]

Insulation and air sealing makes a MASSIVE difference. I'll recommend adding a bag or two on top of what the calculator says. You'll use it.

 

[lalojamesliz]

This sounds like a easy project for my next days off

 

[dcg9381]

If I understand your setup correctly, I think your comfort gains would go in this order:

1. Insulated garage door
2. Insulation in the ceiling
3. Insulation in the walls

This is also reflective of cost in most expensive to least. I look at #2 as being the sweet spot and where I would start.

I disagree with this a bit. Biggest bang for the buck in insulation in high heat environments is almost always the ceiling / roof deck (depending on type of insulation used).

Walls would be next, but garage door is much easier in this case..

 

[billconner]

If you're buying at a big box store, those blowers seem to sit there most of the time. See if you can't talk a free loaner. An extra couple of bags won't hurt as racecougar suggests.

I have found the big box loaners are not usually the air lock type of blower, so beware. Just harder to dense pack the walls (slightly more R and no settling) with a non air lock machine.

 

[CombatNinja]

I disagree with this a bit. Biggest bang for the buck in insulation in high heat environments is almost always the ceiling / roof deck (depending on type of insulation used).

Walls would be next, but garage door is much easier in this case..

You said you disagree then conclude exactly the same thing. I said his best bang for buck is the ceiling. Maybe you are saying that you disagree with the garage door being the single biggest contributor to heat. I live in the Southeast and I have two homes on the same street (one is a rental). Both have West-facing metal garage doors that are getting blasted by the sun from about 2 pm on. The one with cheapo insulated doors that are probably R6 at best is 12-15 degrees cooler than the garage without by the time the sun goes down. These garages are constructed and insulated in the same way. I'm not saying the walls or ceilings do not play a role as well but the uninsulated metal door will be so hot to the touch that you wouldn't want to keep your hand on it for too long. That is putting a whole lot of heat into the space, more so than the ceiling which is admittedly bigger in surface area but 50 degrees cooler.

 

[dcg9381]

--

 

[dcg9381]

If I understand your setup correctly, I think your comfort gains would go in this order:

1. Insulated garage door
2. Insulation in the ceiling
3. Insulation in the walls

This is also reflective of cost in most expensive to least. I look at #2 as being the sweet spot and where I would start.

I may be misinterpreting, but it reads (to my tangled brain) like you think the door would make the biggest difference. Doors and windows are generally (at best) poor insulators compared to walls. I might agree with you if you have a big door with huge gaps, but I was generally taught that most energy loss/gain is through the roof/ceiling - but that may be particular to our hot as hell climate down here.

It's cool to disagree / agree, whatever... No offense intended.

 

[CombatNinja]

You're in Austin. You telling me you don't think an uninsulated metal garage door facing South would be your biggest contributor to heat gain?

 

[firebirdparts]

You're in Austin. You telling me you don't think an uninsulated metal garage door facing South would be your biggest contributor to heat gain?

Nobody is going to agree with you on this, no matter how many times you post it. And really, the OP doesn't really need us doing that in this thread.

 

[lalojamesliz]

Hahaha we can leave te garage door out since I already have 2" foam board on it

 

[buzzworth]

Be sure the attic has a source to ventilate the heat above the insulation or you will create a hot moist area. Ridge vent on the roof? Soffit vents ?
Do not block the airflow against the underside of the roof sheathing or it will rot from the inside.

 

[lalojamesliz]

Be sure the attic has a source to ventilate the heat above the insulation or you will create a hot moist area. Ridge vent on the roof? Soffit vents ?
Do not block the airflow against the underside of the roof sheathing or it will rot from the inside.

Great info! Thank you! I was planning on just spraying as much as I could fit hahaha

 

[racecougar]

Yeah, don't do that. Assuming you have soffit and ridge vents, you'll need to install baffles to prevent the insulation from filling/blocking the soffit vents to allow a path for air to pass through the soffits and out the ridge.

 

[lalojamesliz]

I see vents/screens along the outside up top where the roof overhangs about a foot.

I'll figure something out because I won't be able to easily reach them from up top unless I cut holes in my ceiling where they are at..... I'll probably just do that

 

[dcg9381]

You're in Austin. You telling me you don't think an uninsulated metal garage door facing South would be your biggest contributor to heat gain?

In my opinion, yes. Both garage doors and windows, even when highly insulated (consider triple pane glass) have a fraction of the R factor of a 2x4 or 2x6 wall. If you look at at "recommended" R values in the construction industry by climate zone, you'll notice that recommendations for ceiling/roof deck insulation are much higher than for exterior walls. That's likely because that's where the most heat is gained/lost.

So, yes, I'd insulate the roof first.

I have a 40x60x16 building. It has 3 x 14x14 foot "roll up" doors. They're not insulated panel doors. We've spent time sealing up the gaps/cracks and installing seals on the doors, but at the end of the day they're fairly thin steel. The rest of the building is open cell foam insulated and I can cool it very well with 2 x 24k BTU ductless units. I didn't run the "manual J" - as I just through I'd start with 2 units and add more as necessary, but I assure you it cools very well - I assume a manual J would indicate a need a lot more capacity for 40x60x16... And my foam is probably only R-12 to R-15 all the way around..

I've got no "proof" to show you, but if it was my building, priority would be roof, walls, then garage doors... Consider it opinion and I'm open to respectful disagreement. If you can show me I'm wrong, I'm also open to learning something new.

Edit: OP, One way to add a little "science" to it would be to use a FLIR camera (these have gotten a lot cheaper and can attach to some smart phones). Take a look at surface temps of garage doors, walls, and roof deck... Report back.. Or use a $20 laser temperature sensor for a less visual means of doing the same thing...

 

[lalojamesliz]

In my opinion, yes. Both garage doors and windows, even when highly insulated (consider triple pane glass) have a fraction of the R factor of a 2x4 or 2x6 wall. If you look at at "recommended" R values in the construction industry by climate zone, you'll notice that recommendations for ceiling/roof deck insulation are much higher than for exterior walls. That's likely because that's where the most heat is gained/lost.

So, yes, I'd insulate the roof first.

I have a 40x60x16 building. It has 3 x 14x14 foot "roll up" doors. They're not insulated panel doors. We've spent time sealing up the gaps/cracks and installing seals on the doors, but at the end of the day they're fairly thin steel. The rest of the building is open cell foam insulated and I can cool it very well with 2 x 24k BTU ductless units. I didn't run the "manual J" - as I just through I'd start with 2 units and add more as necessary, but I assure you it cools very well - I assume a manual J would indicate a need a lot more capacity for 40x60x16... And my foam is probably only R-12 to R-15 all the way around..

I've got no "proof" to show you, but if it was my building, priority would be roof, walls, then garage doors... Consider it opinion and I'm open to respectful disagreement. If you can show me I'm wrong, I'm also open to learning something new.

Edit: OP, One way to add a little "science" to it would be to use a FLIR camera (these have gotten a lot cheaper and can attach to some smart phones). Take a look at surface temps of garage doors, walls, and roof deck... Report back.. Or use a $20 laser temperature sensor for a less visual means of doing the same thing...

A flir camera sounds nice but I need to be smarter with my money since i wont use itflr anything else..... I do have a temp gun though.

Next time I run my garage ac I'll check the temps. As of right now I want to buy the cellulose insulation after I install some baffles to prevent blocking the vents.
I've got more projects than I can currently handle but this is definitely up on my list