Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-31-2011, 01:22 PM   #1
Newbie
 
Join Date: Nov 2009
Posts: 4
Share |
Default

Insulating 2x4 attic ceiling rafters help needed


My friend in Sacramento CA (climate zone 3 has cathedral ceiling recommendations of R22 to R38) is looking to insulation his attic ceiling. The home is in the historic part of Sacramento has was built around 1910. The attic has full 2x4 in. rafters that are as straight and solid as the day they were put on the house (I have looked at them). He is starting a project to finish off the attic and make a very large usable room in it. The house is 40 feet by 40 feet with a mansard roof. The roof has four trapezoid sides that meet at the top at an 8ft by 10ft flat roof (at the very top of the house). The 8ft by 10ft flat roof is 13ft above the attic floor. There is about a 4 foot knee wall extending from the floor of the attic to the roof rafters on the outside edges.

Can anyone suggest a good method to insulate the 2 x 4 rafters? My friend is thinking of purchasing 8ft by 4 ft. foam insulation sheets and nailing them to the underside of the rafters (could he use foam sheets thicker than 2in ?). This leaves a 4 in air space between the roof and the insulation.

He is wondering if he would have to create openings at the bottom and top of the rafters to allow air to circulate up the rafters. His house has a stucco exterior including a stucco overhang.

Does anyone have suggestions as how he can best insulate his attic ceiling?

Thanks for your help. It is much appreciated.

tseverson is offline   Reply With Quote
Old 10-31-2011, 07:13 PM   #2
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: VA, MD, DC
Posts: 5,530
Default

Insulating 2x4 attic ceiling rafters help needed


I would suggest a larger than 2" rigid foam. Make that the inside insulation layer and go bigger for better overall R-Value.

2" of foam is at most an R-13 plus the additional 2" in the rafter bays is only an R-25 max (if using Poly Iso foam). That will give you the 2" ventilation space as well.

Windows on Wash is offline   Reply With Quote
Old 11-01-2011, 07:57 PM   #3
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

Insulating 2x4 attic ceiling rafters help needed


http://www.buildingscience.com/docum...r-all-climates

http://docs.google.com/viewer?a=v&q=...1txlzU01V4JQIg

http://www.simplesavings.coop/simple...ee%20walls.pdf

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
insulating attic eastside Insulation 10 09-09-2011 11:03 AM
Insulating garage / adding attic Red Squirrel Building & Construction 4 04-19-2010 07:33 PM
Insulating a Perfectly Good Ceiling Creekbender Building & Construction 2 03-02-2010 06:55 AM
Ceiling condensation icemand Building & Construction 1 12-15-2009 05:16 AM
Old ceiling replacement idsp General DIY Discussions 12 07-25-2009 10:48 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.