# Insulating Detached Garage Ceiling



## Nealtw (Jun 22, 2017)

You need venting from the soffit to the ridge, after that you look at insulation.
Can you post pictures if peak inside and out and top of wall inside and out.


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## imtheomegaman (Jul 6, 2018)

Nealtw said:


> You need venting from the soffit to the ridge, after that you look at insulation.
> Can you post pictures if peak inside and out and top of wall inside and out.


I'll get some pics posted this evening. I was hoping to avoid having to deal with that kind of venting. If it helps I have an exhaust fan near the peak.

Thanks.


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## Nealtw (Jun 22, 2017)

imtheomegaman said:


> I'll get some pics posted this evening. I was hoping to avoid having to deal with that kind of venting. If it helps I have an exhaust fan near the peak.
> 
> Thanks.


 So that would work for the upper vent, you just need are to get in.


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## SeniorSitizen (Sep 10, 2012)

It's not realistic to think that detached garage's eaves and gable ends are sealed like a piece of vulcanized rubber. Just insulate and enjoy a poker game if that's occasionally available in your private pool hall.


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## imtheomegaman (Jul 6, 2018)

SeniorSitizen said:


> It's not realistic to think that detached garage's eaves and gable ends are sealed like a piece of vulcanized rubber. Just insulate and enjoy a poker game if that's occasionally available in your private pool hall.


That's my question though, what kind of insulation?

It's Southern California so we don't get the deep freezes, or tons of rain so I was figuring that simply insulating would do a good enough job.

That said, I don't want to throw good money after bad.


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## Nealtw (Jun 22, 2017)

imtheomegaman said:


> That's my question though, what kind of insulation?
> 
> It's Southern California so we don't get the deep freezes, or tons of rain so I was figuring that simply insulating would do a good enough job.
> 
> That said, I don't want to throw good money after bad.


 It is also about the heat of the roof and making the roofing last longer.


With out a ceiling you can feel the heat that comes from the room, that is why you have a fan. How hot would it get in a much smaller space above the ceiling?


The R value is just a measure of time. How long with it take for heat or cold to get to the other side. Even with AC in the space below, all the cold air goes straight to the floor and pushes any warm air to the ceiling where you need the cold to combat the radiant heat from the attic. Keeping the attic just a few degrees cooler makes a difference.
Then there is discussion about trapped moisture.


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## SeniorSitizen (Sep 10, 2012)

If I'm reading right the garage has 2x6 ceiling joists. If so I'd probably be looking at rock wool batts etc. to fill those 2x6 joists. In your area I wouldn't be concerned with a vapor barrier.


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## Porsche986S (Dec 10, 2017)

I'm not clear on your ceiling , do you have a finished ceiling that isn't insulated ? Or do you have no ceiling and when you look up you are looking at the rafters ? My 2 cents you need a finished ceiling ( drywall , metal ) and then add insulation . At a minimum go with Kraft faced 24 " on center from local big box store or lumber yard . R19 will be 5.5 " thick and will " fill " your 2 x 6 rafter cavities . The kraft face provides a vapor barrier . See how that works out , if you think it's better but still a little hot then you can add unfaced fiberglass rolls or blown in on top of the existing first layer . Ideally you would want about R38 - R40 . But there is no question you need good attic ventilation as mentioned by others .


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## imtheomegaman (Jul 6, 2018)

Ok hopefully this makes things a little more clear:























The one with the vent fan shows the peak of the roof and the fan of course. I ended up with some R-21 Batts.

I've been told to use some of that sheet foil insulation on top of that, not sure if that's worth the extra couple hundred it would cost.

Thanks for all the replies.


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## imtheomegaman (Jul 6, 2018)

Also purchased an infrared thermometer. Was getting readings of 140 degrees on the surface of the ceiling. :vs_mad:


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