# Insulating wall between house and garage



## 11RileyJ (Sep 3, 2015)

Hello all,

Our house has always had issues with staying cool during summer. Here in Florida's Gulf Coast, summer lasts forever. We had the HVAC tech come in and he said our unit is rated to be able to cool our tiny 1,151 sq ft house. Yet if there are more than 3 or 4 people in the house, the temperature climbs from 76 to 80 and stays there as the AC runs continuously. 

We plan to have new insulation blown into the attic (built in 1950, who knows how long the current insulation has been there), but I've been looking to find other ways to insulate. I recently had to remove the drywall that acts as a firewall between our attached garage and the house to install a new receptacle for our entertainment center. I started to wonder if I could insulate this 8x8 section with batts. I know it's not a huge area but the installation would be easy and materials would be cheap. 

I have a couple questions and forgive me if they're of the palm-to-the-forehead variety. I understand the variance in building codes but is it GENERALLY acceptable to insulate between the main dwelling of the house and the garage? I know it's code to have fire-rated drywall between the two but I'm unsure if that would prohibit insulation underneath. Secondly, I've seen batting come faced and unfaced. Which would I need? My thoughts were since the garage contains a lot of moist Florida air I'd probably need the faced batting. Is that so? 

Thanks for any insight offered. And again please forgive my ignorance. New(ish) homeowner here trying to do everything I can to control costs (electric bill) through DIY projects.

Justin


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## Windows on Wash (Aug 30, 2011)

Yes. Not just accepted but recommended. Be sure to air seal between the two so that there is no communication between the air of the two spaces either. 

If you install an vapor barrier equip insulation, it should go towards the warm wall. In this case, that is towards the garage here. 

Look at some radiant barrier in the attic as well. Is it vented?


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## 11RileyJ (Sep 3, 2015)

Thanks.

Yep, there are a couple vents on the other side of the house (the house is "L" shaped). Unfortunately there's also triangular opening to the attic from the garage. Our garage is unfinished. I've been wondering about cutting some rigid insulation to close up that gap so no air can move from the garage to the attic. 

How can I achieve an air seal? Is that something I would have to do BEFORE I put the drywall back up or is that something done after?


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## Windows on Wash (Aug 30, 2011)

Before. 

Caulking and foam to seal any and all gaps.


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## Gary in WA (Mar 11, 2009)

'Yep, there are a couple vents on the other side of the house (the house is "L" shaped). Unfortunately there's also triangular opening to the attic from the garage. Our garage is unfinished. I've been wondering about cutting some rigid insulation to close up that gap so no air can move from the garage to the attic."-------------- Welcome to the forum!

Are the garage walls insulated? If not - and block (CMU) as many FL houses are- install some RB on furring strips; http://www.fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/construction.htm

Adding an RB in house attic will help a lot, cover any exposed foamboard with an ignition barrier- per code, and do you really want more hot humid air into the attic, especially if HVAC unit/ducts are up there; http://www.floridabuilding.org/FBC/publications/AtticVentReportFinal.pdf

Gary


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