In converting an existing attic space to a master suite, the question has come up as to weather to 1. insulatie between the floor joists from the eaves to the knee walls, up the knee walls and then between the rafters to the peak or 2. insulate between the rafters from eaves to peak (with baffles fo cource). Any advice? Also, should the existing blown in between the floor joists be removed, or leave as a “sound barrier”?
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I prefer to see the entire attic space brought into the envelope of the house...meaning insulate the rafters from eave to peak.
This will allow you to use the space behind the kneewalls for storage...either via small access doors, or from drawers build through the kneewall. You could also put mechanicals in the kneewall should that be neccessary.
I'd leave the insulation that's between the joists alone.
New house? Old house? Quality of current building envelope? Ensure that your basement is somewhat tight before you cap the top of the house's envelope.
I was going to edit my previous post to add this link, but it hasn't been released by the censors yet, so...here you go:
http://forums.taunton.com/tp-breaktime/messages?msg=1516.1
Where do you live?
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
Washington DC area. The house is approximately 50 yrs old, appears well built and well insulated in the walls and attic area.
Billy,
I agree with Mongo that you should go ahead and insulate so that the storage spaces are more or less conditioned space. It makes for a much nicer storage area.
I would recommend looking into Icynene foam. It's sprayed on, and is an expanding foam. Vaulted ceilings are a great application for Icynene, since it DOES NOT require stand-offs for ventilation -- therefore, you won't need eave or ridge vents, either. You can just have it sprayed right on the roof sheathing, and then rock the interior.
I did it this way on my house, and avoiding the venting issues saved me a ton of time (and money). In Seattle, I paid about $1.50 per square foot for 4" thick coverage, and about $2.00 per square foot for 6" thick coverage, including labor.
Ragnar
Thanks for the advice! I'll be looking inot that.
I used Icynene and love it, but one note of caution:
check with your local inspector that they will allow a "non-vented roof structure" when you are done!
I had a close call on that with my place. I think that if it had really come down to it I could have negotiated and explained but was lucky and able to skirt the issue (built a 'second skin' cold roof for other reasons). The inspector definitely made me feel like I would have been in for quite a lot of hassle...
What I wanted to ask him (but wisely kept my mouth shut, as he was signing off my approval) was what in the heck does an SIP structure do to meet his code requirement for 'mandatory roof venting' ?
Of course, if you are retrofitting an existing house, and do not need a permit/inspection then don't worry about this nonsense. My warning applies mainly to new construction, and I think if prepared for can be dealt with during the design inspection (show the inspector the engineered design with a non-vented roof (Icynene, SIP) etc, etc).
Now, let's see if this thread takes off on another venting vs. non-venting rant!