R19 Insualtion In 2x4 Wall - Building & Construction - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction


Thread Tools Display Modes
Old 11-30-2010, 11:44 AM   #1
Join Date: Sep 2010
Posts: 3
Rewards Points: 10

R19 insualtion in 2x4 wall

While finishing my attic, I added 1" extruded polystyrene to the backs of the 2x4 knee walls. However, when doing this, I noticed the builder placed R-19 in the 2x4 knee walls. From a chart I found online, the compressed R-19 will provide R-13 insulation value. Therefore, I am considering leaving the R-19 in place since it proved the same R-value as replacing it with R-13. Any suggestions or comments?


SOCON is offline   Reply With Quote
Old 11-30-2010, 11:55 AM   #2
Join Date: Mar 2007
Location: Long Island, NY
Posts: 11,002
Rewards Points: 4,966

R19 insualtion in 2x4 wall

You can buy R15 batts for the 2x4 wall and the foam borad. As a head's up, you're supposed to cover the foam with sheetrock as it will burn and give off toxic smoke.


Ron6519 is offline   Reply With Quote
Old 11-30-2010, 12:59 PM   #3
concretemasonry's Avatar
Join Date: Oct 2006
Location: Minneapolis/St. Paul, Minnesota - Latitude 45.057 Longitude -93.074
Posts: 3,971
Rewards Points: 2,430

R19 insualtion in 2x4 wall

The R-value is just the insulation value of the stuff between the studs/joists and not a acurate measuement of the wall/ceiling R-value. The wood studs will cut the wall insulation value by 10 to 20%. - Even much more with steel studs. - This is just for short term advertising numbers and do not accurately reflect the longer term properties that also relate to mass and weather cycles. Extruded polystyrene board is good at minimizing the thermal short-circuiting of the studs, since it is a continuous barrier and does not permit infiltration.

concretemasonry is online now   Reply With Quote
Old 11-30-2010, 05:14 PM   #4
Registered User
Join Date: Mar 2009
Posts: 10,825
Rewards Points: 3,716

R19 insualtion in 2x4 wall

I would leave it be. The compression means it is now denser than before, unable to have convective loops within it, the same as the denser R-15. If you can meet all 5 requirements in here, you may not have to cover the board. Air space above sloped ceiling to upper attic- need to cover it; http://www.hcpdc.com/pdf/Dryer%20Ven...quirements.pdf

Be sure to close the floor bays and the end of upper insulation between rafter bays to prevent wind-washing; below vents: http://www.simplesavings.coop/simple...ee%20walls.pdf

If any ads are present below my answer or words underlined/colored, I do not condone/support/use the product or services listed/linked to, they are there without my consent.
WELCOME to the forums, if I forgot to say it!
Gary in WA is offline   Reply With Quote

insulation; foam; wall

Thread Tools
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
Cutting through masonry wall mwpiper Remodeling 4 04-17-2010 11:30 AM
building a wall against an exterior wall Mike L General DIY Discussions 2 08-20-2009 03:50 PM
Adding drainage to existing retaining wall? pcballgame Landscaping & Lawn Care 5 04-14-2009 04:29 PM
Atlantic-need your opinion on markd's comments about my vapor barrier? yummy mummy Building & Construction 11 03-07-2007 10:47 AM
Load Bearing Wall? Traybae Building & Construction 1 11-05-2006 02:01 PM

Top of Page | View New Posts