insulating upstairs living space


Old 09-26-01, 03:49 PM
Visiting Guest
Posts: n/a

Hi guys,
I'll TRY to keep this short as possible. I'll give you the basic facts first. I've gotten so many different inputs from this and other web sites that i'm ready to wrap MYSELF in poly barrier and crawl in a hole. My head is spinning.
Have a cape cod home with 12/12 pitch. Upstairs is about 1,200 sq. ft. Framed in 3 beds, bath and play room. Live in Michigan in a "Snow Belt' and pretty open windy area. Exterior walls are 2x6 and so are rafters.Outside of house is wrapped with 3/4 celotex under vinyl siding.
Input has been everything from unfaced glass with poly barrier to minimum code is usually sufficient. I've also been told to and not to insulate rafter area behind 5 ft. knee walls. Floor behind knee walls is insulated with r-30 faced glass.
What I have planned is this :
All exterior walls , knee walls, and angled part of ceiling to have faced glass r-19. Flat part of ceiling to have r-38 faced glass. Have vented rafters from behind knee wall to upper attic above living space for soffit to ridge vent circulation.Caulking all fixtures and cracks and using window tape for drafts. Part of this project is above garage.About 350 sq. ft. Using same approach except ceiling of garage(floor of living space) has r-38 with 2 layers of 5/8 drywall and all seems and perimeter is caulked and taped.Garage will be insulated later.Haven't planned on using any poly barrier because most of my materials are bought , and I hear two stories on putting poly over faced glass. One says don't do it . The other says do it,it's just inspectors that don't think out of the box so they don't know any better than the codes their enforcing. I simply don't know ! This is my last string of posts on this subject- will be starting next week.
Any input on this whole project is greatly appreciated whether it's in addition to, or a whole different approach. Or if you just want to rip me a new one- go ahead, doesn't hurt anymore.
Oh yeah- do I need to vent rafter area above ceiling in dormers ?Also, floors of said living space have faced r-30 glass.

Thanx in advance, Bill

I'd rather be working, at least I get paid !
Sponsored Links
Old 09-27-01, 06:51 AM
Visiting Guest
Posts: n/a
Basic insulation theory. You insulate the walls, ceilings, floors of the area you want to control the temp.

If you have living space inside an attic and part of the attic is not living space and you insulate the outer most wall/roof, then you have effectively included the non-living space in your heating/cooling zone.

Should you insulate the rafters over the knee wall space AND the knee wall space? The insulation on the knee wall will be the outer edge of your temp controled area. The insulation on the rafters will help keep the temp between the knee wall and the rafters more consistent. But you really don't care because you are not living in that area and you are in effect wasting material and effort insulating the rafters. One possible benefit would be that any heat escaping through your insulation will be trapped before it gets to the roof, melting snow and causing ice dams.

Should you ventilate overtop of the ceiling and below the rafters? Yes. Look into getting something like PropaVents to create a vent space for the angle part of the wall/roof that is insulated. This will allow ventilation to travel from your soffits to the attice peak.

Look into foam-in-a-can to fill the holes in the framing used for utilities. Fill the holes with the foam. Easy way to reduce drafts.
Old 09-27-01, 09:24 AM
Visiting Guest
Posts: n/a
do not put poly over kraft faced fiberglass, and if you use expandable foam to fill voids (which I reccommend) only put it in about 1/2 thick at most...The idea is to stop air penentration, which a 1/2 " is more than sufficient.... Over filling voids with foam can cause problems in certain situations..usually around windows and doors, too much foam can cause the framing around doors and windows to move and not allow them to open and close correctly...

In the existing attic areas that remain, I believe you said have an R-30 currently.. I would place R-11 unfaced batts over the top of the existing insulation running the opposite way. I live in the Metro Detroit area and wouldnt suggest anything less than R-38 in your ceiling areas.

Good Luck

Old 09-27-01, 12:50 PM
Visiting Guest
Posts: n/a

Thanx guys. My rafters are vented and I have the foam. My question about venting was directed towards the dormers. The area above the living space in dormers has soffit on either side, no ridge vent. (dormers are (3)6 ft. and (1) 10 ft. wide) Just wondered if you think that's enough ventilation or if I should add a vent at the top to achieve the same soffit to ridge vent effect like the rest of house .

Thanx again, Bill
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: