# R13 insulation in 2x6 walls?



## superme1000 (Jul 13, 2015)

I just purchased a house with a 30x30 detached two story garage. The garage currently does not have any insulation or drywall, and I would like to change that. 

The first floor is framed with 2x6s, and has a 12ft ceiling. The second floor is framed with 2x4s, and has a maximum height of 10ft from the floor to the tallest point of the roof. The roof is framed with 2x6s.

Now my question is can I use R13 to insulate the entire garage? I know 2x6s call for R19, but my local hardware store currently has an amazing deal on R13: about $6 per 15" x 32' roll. The cheapest R19 is about 4 times that price. Are there any problems with using R13 in 2x6 walls (besides being less efficient than R19)? I plan on heating/cooling the garage only while I'm wrenching on a vehicle. I will install a mini split unit for heat/AC.


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## SeniorSitizen (Sep 10, 2012)

Go for it. Just be sure you staple the flaps to the 2x6 edges as it was designed to be installed.


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## Fix'n it (Mar 12, 2012)

best practice = use the proper insulation = if its made for 2x4 walls, that is what it should be used in. if its made for 2x6 walls, thats where it should be used.

now, if you use the cheap fiberglass bats made for 2x4 walls. you can push 2 bats into the 2x6 wall and get better insulating as the 2 bats would equall 1 good one.

but, for what you want to do = just drywall the first floor and get to work on the cars.


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## Gary in WA (Mar 11, 2009)

R-13 (medium density) is actually more efficient than R-19 (LOW-density and R-18 when compressed in a 2x6 wall); http://www2.owenscorning.com/litera...ul Compressed R-Value Chart Tech Bulletin.pdf

Two layers as said would give R-23 minus the thermal bridging of the studs. No convective loops as with R-19; pp. 45-47; http://www.buildingscienceconsultin...010-03-10_When_R-Value_Doesn t_Measure_Up.pdf

R-13 is just R-19 compressed, same amount of fibers, smaller air pockets. You don't want an air space on either side of batts, unless the sheathing was air-sealed. 

Gary


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## SeniorSitizen (Sep 10, 2012)

The insulation has air pockets so there is nothing wrong with an air space between insulation and sheathing. If the cavity was completely filled with R-19 there would still be air between the sheathing and insulation.

Air Sealing - only retards air movement. Hermetically sealing prevents any air movement but that isn't going to happen for a nominal fee in residential construction.


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## craig11152 (Jun 20, 2015)

Given that its a detached garage that will get infrequent use, IMO if you choose not to do it textbook its no big deal.


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## Gary in WA (Mar 11, 2009)

And it's the air movement that kills fiberglass insulation, either infiltration or exfiltration, the air space just gives a small hole more area to move all over the product from the backside; http://www.greenbuildingadvisor.com...ir-leakage-degrades-thermal-performance-walls

Air space in front, next to drywall is detrimental; https://www.google.com/url?sa=t&rct...pCFvoJlgzLf5dFA&bvm=bv.83134100,d.cGU&cad=rja

Gary


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