# new attached garage insulation



## Windows on Wash (Aug 30, 2011)

In theory, the vapor control goes towards the warm side wall to keep the moisture from migrating to a cold side and forming condensation. 

Garages are different in that you can have a bunch more moisture in them than you can inside the conditioned air of the home. 

Have you looked into maybe skinning the wall between the garage and the home (prior to drywall) with some rigid foam? It will help with the thermal bridging and control the moisture as well as help with air seal.


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## ryansdiydad (Aug 16, 2015)

I haven't thought of that. And I know that even thou i will cover it with fire rated drywall I am not keen on putting that foam anywhere that we might actually have fire issues. Yes it is irrational. 

If I do the rigid foam, do I still use faced batts in the garage exterior walls? 

Or do I have this backwards and use unfaced batts in the garage and faced batts in the house? Since the garage is not heated and the temperature variance between garage and outside wont be nearly as much as a house and outside.


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## Windows on Wash (Aug 30, 2011)

If you do the foam, you would not use faced insulation in this case. 

If you cover the foam in fire-rated drywall, you should be quite fine. If you are a bit worried about it, cover the adjoining walls to the home with 2 layers. Shouldn't be that much of a bump in materials pricing.


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## ryansdiydad (Aug 16, 2015)

So I would use foam between the house and garage with unfaced batts in the walls or no batts at all? And faced batts in the exterior garage walls?

Thanks for the help!


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## Windows on Wash (Aug 30, 2011)

How built is the garage now? What state in the construction process?


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## ryansdiydad (Aug 16, 2015)

it is framed sheathed and the roof is on...


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## Windows on Wash (Aug 30, 2011)

What is your exterior cladding going to be? Some rigid foam to the exterior would certainly help keep that space more temperate and lessen the strain on the interior wall system as well.


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## Gary in WA (Mar 11, 2009)

Welcome to the forum!

If you add foamboard, you will need to buck the jambs out at the man door. IMHO, skip the foam inside the garage; temperatures will be tempered from the garage structure, stopping wind (chill-factor), rain, fog and mist. I would guess 5-20*F warmer thanks to having it there. When parking a wet car, the engine, hood, roof, brakes, tires and exhaust will dry a lot of the water most will be vaporized and rises with the warm air. This air/moisture goes through the ceiling drywall to attic, removed by the stack effect (warm air rises) with attic ventilation. Same stack effect that moves your warm garage air to the ceiling after settling soon after entry when cold. I doubt much at all will move laterally to deposit on your house wall especially when moisture moves from wet to dry and warm to cold. Some may still be on the car. There is only warm air from the car to drive the moisture; up, not sideways. Warm room air/moisture is trying to get out through the garage wall, not let warm air/moisture in during heating season- without a driving force. 

It should be ADA and add some foam strips to the studs if worried about thermal bridging. http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/ Without foam, your walls will be slightly warmer than a cold wall (exterior garage) due to some heat loss. Cover drywall with a latex paint to protect from any moisture in the air. Spend the savings on a high-density FG batt (at least in garage) rather than R-19 (low-density) inherent with heat-robbing convective loops and R-value loss at install. 

You are under the IBC; http://www.cmdgroup.com/building-codes/vermont/
Ask your AHJ, (local amendments) I doubt you need fire rated drywall (5/8" Type X); http://publicecodes.cyberregs.com/icod/ibc/2006f2/icod_ibc_2006f2_4_par101.htm


Unless you have a furnace on that wall (need 5/8" there)... be sure to install that area before HVAC comes, if GC'n yourself. Remember you carbon monoxide alarm; http://firesafety.vermont.gov/sites/firesafety/files/pdf/Code%20Info%20Sheets/2012_firecode.pdf

"The garage walls are 2x6 with full 4" bed stone veneer, full brick, and some hardie board siding."--------------- you don't want Tyvek behind brick veneer, use foamboard as WoW said or a semi-permeable cover on OSB; http://buildingscience.com/documents/reports/rr-9909-drainage-planes-and-air-spaces/view

Your Zone; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=Vermont

Requires- not code but to omit the interior asphalt paper-facing and be worry-free; http://buildingscience.com/document...ulating-sheathing-vapor-retarder-requirements

Are you siding, windows/doors install?

Gary
PS. What is going on at the fascia/barge boards?......


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## ryansdiydad (Aug 16, 2015)

Lots of great information.. Thanks Gary. 

My contractor was saying that I might have to put 2 layers of 5/8 drywall up. I think to try to convince me to let him do the drywall instead of me. I am goin to drywall the garage and let his guys do the inside of the house. Looking to save a buck everywhere I can.

What to you mean about the fascia?


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## SeniorSitizen (Sep 10, 2012)

If you will be pulling a snow packed car into the garage save enough money back to invest in a good squeegee. Those fender wells can contain a good load of water.


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## Gary in WA (Mar 11, 2009)

"My contractor was saying that I might have to put 2 layers of 5/8 drywall up. I think to try to convince me to let him do the drywall instead of me. I am goin to drywall the garage and let his guys do the inside of the house."------------- tell him you will ask the BI about that when you visit them with other questions... and that - then you will know where you stand. Should get him thinking straight- with your two-way meaning ending... lol. 

Just I hope the architect drew the fascia like that as normally they would rip the tails only- of the rafters for a 6" high so it ties better at the rafter barge/rake interface. And, plumb-cut the fascia rather than square-cut. A few Craftsman houses used that detail, but always with a larger barge board than fascia board. 

Judging by the wavy roofing overhang, did they install a metal drip-edge flashing? https://www.google.com/search?q=metal+drip-edge+flash&ie=utf-8&oe=utf-8

Gary


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## Gary in WA (Mar 11, 2009)

Your fascia detail is used mostly with a built-in gutter system, when the board extends above the roof plane and wood cant strips are added to the inside corner. Very neat as no gutter system is exposed, especially the eyesore angled brackets for a regular gutter to get it plumb/level. Be sure to use a "drainable" housewrap (or rainscreen) behind the Hardie (reservoir siding); http://buildingscience.com/documents/insights/bsi-071-joni-mitchell-water-and-walls

Gary


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