# Trying to make my bonus room more comfortable



## 99ls1tj (Jun 6, 2016)

Greetings. I would like some advice on how to make my bonus room more comfortable. As you can see in the second pic, there is a large space between the bonus room floor and the insulation which is resting on the garage ceiling. 
I have gained access to one side of the room by adding a kneewall door. As of yet, I have not addressed the other side, which has 2 dormers. 

My plan is to try to blow in insulation and add blocking between the I joists. I'm wondering if I should remove the current insulation batts before I use the blow in, or if I should blow in above the batts. I've also seen where companies drill holes in the garage ceiling and add insulation that way. I'm open to any suggestions. 

Also, is there anything special I should know about adding blocking between the I joists? I thought I would find some fairly thick foam and cut it to cover the space between the I joists. I've seen some pictures where this has been done using spray foam. Would caulking be superior to foam? 

The next part of the puzzle is how to attack the walls. I've noticed the new houses around me are being built with 2x6" knee walls for r-19 insulation. I considered nailing some 2x2's to the studs and using r-19. I'm not sure this would be cost effective though. I also need to sheath the back of the walls. Any suggestions on what to use there? I would like to add some r-value if possible. I have read where there are issues with creating a double vapor barrier. The current r-13 insulation has a paper backing facing the bonus room. I'm also at a bit of a loss on the best way to handle the top of the knee walls since there is no top plate and the studs are nailed to the rafters. 

Below are some pics of the issues. Any and all suggestions would be greatly appreciated. 

Thanks





They just curled the insulation up to try to block the air flow


Back side of knee wall. R-13 which is working it's way out of the stud cavity



access door I installed


Attic above bonus room



Top of knee wall



The 2x10's are still part of the bonus room, but they are over the laundry room / hall / hall closet. I have a nice hump in the floor at the transition from the 2 x 10's to the I joists, but that is a good subject for another thread / project.


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## Windows on Wash (Aug 30, 2011)

Where is the home located? 

You are mostly on the right track.


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## 99ls1tj (Jun 6, 2016)

Windows on Wash said:


> Where is the home located?
> 
> You are mostly on the right track.


Good question, I should have included that.

Home is located just North of Atlanta, Ga.


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## Windows on Wash (Aug 30, 2011)

99ls1tj said:


> Good question, I should have included that.
> 
> Home is located just North of Atlanta, Ga.


Based on your location, you don't need any barrier and if anything, it would be located to the outside wall to keep the warm, moisture laden summer air from pushing in. 

http://buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

Best way to handle the knee wall would be with some foil faced poly-iso foam across the framing. Combination of the radiant barrier and uncoupling of the framing from the warm attic air should work well. 

I am not to worried about the vapor trap in this case as you won't be generating too much moisture in the bonus room and the kraft paper is probably poorly fit. If you are concerned about it, you could remove the insulation and install some mineral wool (roxul) that is un-faced. 

In terms of the floor joist cavities, just installing some blockers and air sealing them will allow that air to function as an insulation layer and give you much better performance out of the assembly. I wouldn't go cutting holes in the ceiling or try to fill it as is.


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## Gary in WA (Mar 11, 2009)

So the link shows no foil-faced foamboard except in really cold climates, warm climate- Atlanta- Zone 3; no faced foam, only unfaced according to the link. You don't need a vapor retarder next to drywall per your location, no faced insulation- only latex paint as per link. "I am not to worried about the vapor trap in this case as you won't be generating too much moisture in the bonus room and the kraft paper is probably poorly fit."------- link also showed difference between air barrier and vapor barrier, perhaps you are confusing the two- vapor barrier is 95% effective if 95% there, slits/gaps only effect an air barrier. 

Be sure to close-off the top of wall to the rafters or you will get outside moist air in your cavity trying to get out; with foil- you limit drying to interior only (50%), as per link. Remove the asphalt facing and caulk the drywall/stud joints to stop room air entering stud cavity with your 3000 HDD, caulk between bottom plate/subfloor, add the unfaced FG back in, caulk edges of studs/plates before adding unfaced foam board so it has 100% chance to dry either way, as per link. Optimum job; seal the edges of foam with furnace tape/mastic as it does shrink with age. Add some spacer blocking to staple a radiant barrier too, so any moisture can get out if it ever gets in "flow-through" assembly as per link. Probably need an ignition barrier on the foam if using for storage, check local AHJ.

Gary


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