Underfloor Insulation W/non-standard Joists? - Insulation - DIY Chatroom Home Improvement Forum

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


Thread Tools Search this Thread
Display Modes
Old 03-06-2012, 01:54 PM   #1
Join Date: Dec 2011
Posts: 109
Rewards Points: 101

underfloor insulation w/non-standard joists?

Hey guys, I need to insulate under the floor in my 1950's ranch. The floor joists are 4x12's that vary from 4' to 8' apart. I'm not sure how I should go about hanging/holding the batts to the underside of the floor. It looks pretty simple if you have 16" or 24" oc joist but how is it typically done on a house like mine? Thanks, 1
1dumbquestion is offline   Reply With Quote
Sponsored Links
Old 03-06-2012, 01:56 PM   #2
Exterior Construction
Windows on Wash's Avatar
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 26,008
Rewards Points: 808
Blog Entries: 41

Rigid foam cut to fit would be ideal as it will yield a higher R-Value per inch.

After that, cutting batts (Roxul or FG) is somewhat easy (easier with Roxul) and covering them with a tyvek or insulation webbing will help support them.
Windows on Wash is online now   Reply With Quote
Sponsored Links
Old 03-06-2012, 03:05 PM   #3
AGWhitehouse's Avatar
Join Date: Jul 2011
Posts: 1,378
Rewards Points: 500

I second WoW...
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Sponsored Links
Old 03-06-2012, 11:16 PM   #4
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

Oregon Energy Code requires R-30 for 10" joists, which is probably what the Inspector wants rather than the R-25 (8" joists), seems they always want more....http://ecodes.biz/ecodes_support/fre...Efficiency.pdf

I would use some unfaced R-19 batts sitting on 2" (R-10) foil-faced foam board (Thermax) with the air space above: http://www.buildingscience.com/docum...n-crawlspaces/ Note: no vinyl floors.

This would stop radiant, stop air movement so you can use f.g. and lower the dew point temperature in the cavity = no condensation worries, even here in the Pacific Northwest. Add a 2x2 nailer at beam level at exterior perimeter. Add some utility 1x4 strapping under the longer spans, tape all joints against air, use the scraps with canned foam on the concrete wall from decking to nailer. Be sure the dirt is covered with poly.

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.
17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
Gary in WA is offline   Reply With Quote
Sponsored Links

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
Where would I purchase metal shims? Vincer Building & Construction 19 05-28-2011 10:46 PM
Any way to splice joists together? tpagel Carpentry 26 04-28-2011 05:32 PM
Cut Joists - How to Repair? stubits Building & Construction 13 03-16-2010 05:12 PM
Basement cable location on joists BasementVirgin Electrical 12 02-24-2010 10:56 AM
Best subfloor and material thickness nugentcn Flooring 7 09-07-2008 12:48 PM

Top of Page | View New Posts