insulation -- adding cabinets in knee wall

flamtap

Hi,

I have a bonus room over my garage. The bonus room has knee walls about 5' high on both sides, and a vaulted ceiling. I am planning to build cabinets in the walls to use the space behind the knee walls for storage.



Currently, there is pink fiberglass insulation below the finished room, in the knee walls, and in the ceiling above the room.

I'm seeking advice as to how I should plan to insulate when I put these cabinets in the wall. The cabinets will be stepped, with a 12" deep section near the top and a 24" deep section for the lower shelves.

My first thought is to insulate the space which will contain the cabinets. I think this would involve continuing the air baffles (is that the right term?) from the roof vents all the way down to the eaves, then continuing the fiberglass insulation in the rafters and in the floor joists.

This image is looking "up" the rafters towards the peak of the roof:


This is looking toward the eaves:


This attic space extends the depth of my house, maybe 40'. I plan to put the cabinets in the portion of the bonus room which is the front 12' of the space. I suppose I would either need to insulate the entire space, or build an insulated wall in the attic to enclose the section with the cabinets.

I have not done any insulation work before, so I have a general idea that I need to be worried about a vapor barrier and fire safety. What else? Am I headed in the right direction?

I live in North Carolina where we are dealing with heat and humidity for much of the year and the temperature rarely goes into the 20's or below.

Thanks for any advice and tips!

flamtap

joecaption

It's as simple as building 3 walls and a simple flat roof, There is no reason to have it even tie into the rafters that are there now. As long as the new walls and roof are insulated and the inside is sheetrocked it will work fine.
It would be best to install a header over the top of the new opening since this is a supporting wall most likly.
It would be the same thing as building a closet in a house, just insulated.

flamtap

Ok, that would simply things I think. I will have to check my planned cabinet dimensions to make sure I can fit everything in the space. Back to sketchup!

Interesting. I was thinking the wall is not load bearing since it appeared to be 2x4's tacked to the rafters and the floor, and studs in between, to support the wall. After googling the topic some, there are mixed opinions for similar projects. Some say it is load bearing, as the studs fall directly under the rafters. However, there is no support directly underneath the wall. The wall is supported by the floor joists that also form the ceiling over the garage.

My plan is to install 3 cabinets, each approx 46.5" wide so that I will leave every third stud in place. I think there would easily be room to add a header over each opening. Would jack studs be used on each end or can I attach the header to the remaining studs?

Thanks,
flamtap

joecaption

Since we have no idea what these cabinets you plan on using look like or how you plan on laying them out some info may not apply.
Why are you spacing them out?
Why would you leave studs in place?
Much simpler to just install one header and fill in with what ever you need.
That wall may or may not be a supporting wall, why take a chance?
Yes you have to install jack studs.

flamtap

I need to update my sketchup drawing. (I started this idea 5+ years ago).

My idea is to insert cabinets into the wall, rather than replace the entire wall with cabinets. I'm thinking two storage cabinets on the sides and a cabinet to hold flat-screen TV and equipment in the middle. There will be a little bit of space between each cabinet.

So rather than tearing down/re-framing the entire wall I'm hoping I can just cut holes in it where the new cabinets will go. But I will consider other arrangements. Before I make final plans I need to know what accommodations I need to make for insulation and structural considerations.

I don't have access to my old drawings on this computer, but I will try to post some later to give you a better idea of what I'm planning.

flamtap

joecaption

You would not want the space the openings only a 2X4 apart. There would be no way to trim or finish it out. 6" would be more like it.

flamtap

Agreed. I think in my original plan I must have had 30.5" wide cabinets 14.5" apart. (so remove one stud for each cabinet and have 2 studs in-between.)

I have in my head that I need a wider center cabinet now as I am planning for a larger TV. Obviously, I need to review my old drawings again!

flamtap

flamtap

Was able to get to one of my old drawings through an online backup. This might help give you an idea of what I'd like to end up with:



flamtap

Gary in WA

So what is the garage width? What size are the rafters- 2x10's? No center wall below in the garage? No beams below? What size are the floor joists- 2x12's?

Gary

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flamtap

The rafters are 2x8. The floor joists are 2x10. The garage is 24' I think, and there is a large beam across the middle supporting the joists in the center of the garage. I don't know what the beam is made of, it's enclosed in drywall, etc.

As for the insulation, I am considering this box idea more, except that I may use the rafters as the "top" of the box, and just build a back wall and sides where needed.

On an older similar thread, someone suggested using unfaced insulation with plastic sheets over everything for the vapor barrier. Any reason why that would be better or worse than the paper-faced batts?

Thanks for all the tips!

flamtap

Gary in WA

No poly: http://www.buildingscience.com/docum...commendations/

The paper-faced batts are variable; http://www.buildingscience.com/docum...vapor-barriers

Compare the ink stamp on the rafters for the species wood of rafters for spans; http://publicecodes.cyberregs.com/ic...?bu2=undefined May not need a header...the wall is for drywall/attic separation, not required structurally for your span if lumber grade is per minimum code.

Air seal the floor joists under the flooring, at the knee wall to stop air movement degrading your f.g. insulation there. Use housewrap or foamboard on attic side of knee wall (tight to extended baffles with proper ignition barrier only if required. Caulk the bottom plate on the attic side at subfloor to stop air infiltration/exfiltration. http://www.nrel.gov/docs/fy00osti/26450.pdf

http://www.buildingscience.com/docum...ty-insulation/

Gary

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flamtap

These links answer a lot of questions. The insulation in the current knee wall is paper-faced batts, so I will probably use the same in the new insulated wall.

I always wondered about vapor control in Southern climates... It seems like so many of projects on popular shows & websites are very Northern-centric.

I'm working on my plans in sketchup. I'll be back when I have some drawings to add.

flamtap