DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > General Home Improvement Discussion > insulating vaulted ceiling w/ rigid foam

Help Support House Repair Talk by donating using the link above.
Thread Tools Search this Thread
Old 05-24-2006, 08:27 AM  
Junior Member
Join Date: May 2006
Posts: 1
Default insulating vaulted ceiling w/ rigid foam

Hi, my wife and I live in western New York in a house we bought last year. Our house is well insulated and weather-tight except for one area. This area was once attic space that the previous owner converted to a loft overlooking the kitchen. Itís ceiling is framed with 2x6ís and the finished ceiling (drywall) is sloped/vaulted. There is currently R-19 fiberglass jammed into the 5.5Ē rafter cavity with a cheap Styrofoam type baffle that is most likely crushed in several spots. This area is the only one that continually melts snow in the winter resulting in ice dams. Heat during the summer also builds up in the loft due to the roof heat coming into the house.

I would like to take the dry wall down and replace the fiberglass with rigid board. This is the only way I can get close to R-38 without lowering the ceiling too much (peak of the ceiling is approx 4í above the loft floor). I have looked into spray expanding foam, but even that doesnít give me the R-value without adding more rigid board. The only thing I am concerned with is how much the rafters expand due to summer humidity. If I re-insulate during the summer tightly squeezing the insulation boards between the rafters, will the foam boards become loose during the winter when the rafters dry out and possibly shrink? Also, do I need to get the insulation value up to R-38, or is R-30 enough to keep the snow on the roof?

Thanks for any help given me.

rroth is offline  
Reply With Quote
Old 05-24-2006, 07:53 PM  
inspectorD's Avatar
Join Date: Dec 2005
Location: Litchfield, CT
Posts: 4,490
Liked 265 Times on 209 Posts
Likes Given: 772

Default On the right track...

Sounds good,dont worry about the wood movement, it has most likely done it's dance.
Fill the bays and try to get at least a 1/2 inch foam board to span all the rafters.You can nail these to the rafters enough to hold them up. This creates a thermal bridge and seals the roof.Then sheetrock over that ,just use longer screws.No vapor barrier is needed in this installation.Have fun.....

Just My
Made in the
inspectorD is offline  
Reply With Quote
Old 06-01-2006, 04:53 PM  
Senior Member
Join Date: Mar 2006
Posts: 2,990
Liked 4 Times on 4 Posts


There is also a method of insulating called the "Ice House" wherein you leave a 1" space next to the roof sheathing and fill the rest of the space with insulation. This would also require soffit vents and a vent-a-ridge so you can get full air flow between each rafter. This method will also keep your shingles cooler in the summer and, if they are asphalt, it will make them last years longer.
glennjanie is offline  
Reply With Quote
Old 12-13-2009, 09:22 PM  
Senior Member
Join Date: Dec 2006
Posts: 331

Just make sure like Glenn said that you do leave a gap between the rigid board and the underneath side of the roof sheathing. It can get ugly on the inside with mold and ugly on the outside with curled shingles.
cibula11 is offline  
Reply With Quote
Old 12-15-2009, 06:15 AM  
Join Date: Oct 2009
Posts: 98

This technique you could increase the profundity of insulation between the rafters. Alternately, you could insulate the roof deck under the shingles using several inches of foam in addition to foam board or other types of insulation placed between the rafters below.

Best Regards,
Superpack is offline  
Reply With Quote
Old 12-15-2009, 08:16 PM  
Senior Member
Join Date: Mar 2009
Posts: 402
Liked 38 Times on 36 Posts
Likes Given: 10


WHEN was this...... lol
Be safe, Gary

GBR is offline  
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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

Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
Rigid Foam Panels Under Drywall Ceiling aNYCdb Insulation and Radiant Barriers 7 01-05-2017 06:53 PM
insulating a vaulted ceilings in a 2003 manfactured home? bartko116 Green Energy and Sustenance Living 2 09-01-2014 06:15 PM
vaulted ceiling? Half-Mine Garage & Workshop Forum 1 03-23-2012 07:48 AM
Insulating a non vented vaulted ceiling JLoc Insulation and Radiant Barriers 8 02-15-2012 03:58 PM
Rigid foam board under carpet? jenjencali Flooring 1 12-23-2010 12:49 PM

Newest Threads