Blown-in Fiberglass Attic Insulation - Building & Construction - DIY Chatroom Home Improvement Forum


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

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

Reply
 
Thread Tools Display Modes
Old 11-16-2010, 07:29 AM   #1
Newbie
 
Join Date: May 2009
Posts: 4
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


I have loose fill in my attic to the top of the joists. It's a ranch with a 4/12 pitch so I have very limited access. The soffits are continious vented as is the ridge. My builder friend told me I wouldn't need baffles with the blown-in fiberglass. Checking here for a second opinion on the baffles. He said the blown-in fiberglass doesn't compact and I will get adequate air flow without baffles.

Advertisement

jdieter is offline   Reply With Quote
Old 11-16-2010, 07:39 AM   #2
Member
 
Join Date: Mar 2007
Location: Long Island, NY
Posts: 9,519
Rewards Points: 2,000
Default

Blown-in Fiberglass Attic Insulation


This is not a contractor I would hire. Blown in fiberglass will hinder air flow.
Ron

Advertisement

Ron6519 is offline   Reply With Quote
Old 11-16-2010, 01:09 PM   #3
Member
 
Join Date: Dec 2008
Location: Fairbanks, AK
Posts: 1,847
Rewards Points: 1,000
Default

Blown-in Fiberglass Attic Insulation


Ron is right. Why FG instead of cellulose? FG is pretty poor insulation, unless you are dense-packing that Spider stuff. There are a variety of reasons to not use FG. Greenbuildingadvisor.com and buildingscience.com have lots of info on it. john
jklingel is offline   Reply With Quote
Old 11-17-2010, 12:27 AM   #4
Registered User
 
Join Date: Mar 2009
Posts: 9,972
Rewards Points: 2,010
Default

Blown-in Fiberglass Attic Insulation


I agree with both previous posts. More reading: Insulation & Baffle
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
Old 11-17-2010, 07:56 AM   #5
Newbie
 
Join Date: May 2009
Posts: 4
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


The reasons I'm using blown-in fiberglass are; no vapor barrier under exisitng insulation, trusses are 24" centered with 1/2" drywall ceilings and I'll need to go from R13 to R40, when fully insulated for the most part all the attic wiring and other utilities will be buried, and a few other reasons. Here's a link to an unbiased review of the 2 types from the North American Insulation Manufacturers Association, http://www.naima.org/pages/resources.../pdf/BI475.PDF
I contacted Owens Corning regarding soffit venting and here was there reply. My contractor friend is in Fl. and I'm in Indiana, don't know if that had a bearing on his statement regarding soffit venting, and I didn't ask him if that was acceptable with his local code.

For attics with continuous soffit venting: add rafter venting every 8' if there is continuous ridge venting, or every 4' for all other types of ridge venting - make sure the rest of the openings between the attic and soffit are protected to keep the insulation out of the soffit area.
jdieter is offline   Reply With Quote
Old 11-17-2010, 09:35 AM   #6
Member
 
Join Date: Mar 2007
Location: Long Island, NY
Posts: 9,519
Rewards Points: 2,000
Default

Blown-in Fiberglass Attic Insulation


Quote:
Originally Posted by jdieter View Post
The reasons I'm using blown-in fiberglass are; no vapor barrier under exisitng insulation, trusses are 24" centered with 1/2" drywall ceilings and I'll need to go from R13 to R40, when fully insulated for the most part all the attic wiring and other utilities will be buried, and a few other reasons. Here's a link to an unbiased review of the 2 types from the North American Insulation Manufacturers Association, http://www.naima.org/pages/resources.../pdf/BI475.PDF
I contacted Owens Corning regarding soffit venting and here was there reply. My contractor friend is in Fl. and I'm in Indiana, don't know if that had a bearing on his statement regarding soffit venting, and I didn't ask him if that was acceptable with his local code.

For attics with continuous soffit venting: add rafter venting every 8' if there is continuous ridge venting, or every 4' for all other types of ridge venting - make sure the rest of the openings between the attic and soffit are protected to keep the insulation out of the soffit area.
It isn't even common sense to put insulation in the soffit. Building code aside.
Ron
Ron6519 is offline   Reply With Quote
Old 11-17-2010, 01:48 PM   #7
Member
 
Join Date: Dec 2008
Location: Fairbanks, AK
Posts: 1,847
Rewards Points: 1,000
Default

Blown-in Fiberglass Attic Insulation


Quote:
Originally Posted by jdieter View Post
The reasons I'm using blown-in fiberglass are; no vapor barrier under exisitng insulation... when fully insulated for the most part all the attic wiring and other utilities will be buried, and a few other reasons. Sorry, but I don't see the reasoning behind the no VB. IF you need one, and that is a big IF, I think the cellulose will be better as it can buffer moisture absorption. Be sure to air seal.

...trusses are 24" centered with 1/2" drywall ceilings and I'll need to go from R13 to R40... Robert Riversong, housewright.com and one of the gurus on greenbuildingadvisor.com, installs massive cellulose on 1/2" rock, 24"OC. He has been at this for decades.

Here's a link to an unbiased review of the 2 types... Unbiased? Hardly. This is right from their web site: "NAIMA is a trade association of North American manufacturers of fiber glass, rock wool and slag wool insulation products."

See above after the bullets. I'd check out greenbuildingadvisor.com and buildingscience.com before I made the big decision, myself. Cheers. john
jklingel is offline   Reply With Quote
Old 11-17-2010, 04:59 PM   #8
Registered User
 
Join Date: Mar 2009
Posts: 9,972
Rewards Points: 2,010
Default

Blown-in Fiberglass Attic Insulation


jd, your report is from mostly fiberglass insulation manufacturers, look at the bottom of the page....

Make sure your f.g. will not have convective loops, depends on the density: http://www.homeenergy.org/archive/he...92/920510.html

http://infrared-energy.com/files/Spe...onProblems.pdf

http://michaelbluejay.com/electricity/insulation.html

Air seal the attic first, as Jk said (thanks for the link on weight): http://www.familyhandyman.com/DIY-Pr...s/Step-By-Step

The figures you received are way off, you need soffit vents in every bay: http://www.airvent.com/homeowner/pro...it-specs.shtml

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
Old 11-18-2010, 09:33 AM   #9
Member
 
Join Date: Nov 2010
Posts: 100
Rewards Points: 75
Default

Blown-in Fiberglass Attic Insulation


Id look at blown in borate cellulose. We just had that done and love the results. Beyond the green aspect, theres also the fact that its more fire retardent and deters insects and rodents. Our energy company highly recommended cellulose over FB from an energy consumption standpoint as well. btw: Make sure you get the receipt to list the cost for materials so you can get an energy tax credit.
Wiscbldr is offline   Reply With Quote
Old 11-20-2010, 06:33 AM   #10
Newbie
 
Join Date: May 2009
Posts: 4
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


Oops you-all are correct it wasn't an unbiased report. Anyway looks like cellulose is about 20-30% more efficient than fiberglass. So far the only thing that I don't like about cellulose is the weight, 2-3 times heavier than fiberglass and I can all ready see waviness in my ceilings.
jdieter is offline   Reply With Quote
Old 11-20-2010, 08:08 AM   #11
Newbie
 
Join Date: Nov 2010
Posts: 10
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


Quote:
Originally Posted by Ron6519 View Post
It isn't even common sense to put insulation in the soffit. Building code aside.
Ron
Agreed!
ClimateControl is offline   Reply With Quote
Old 11-20-2010, 08:10 AM   #12
Newbie
 
Join Date: Nov 2010
Posts: 10
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


how about spray foam and a radiant Barrier?
ClimateControl is offline   Reply With Quote
Old 11-21-2010, 07:14 AM   #13
Newbie
 
Join Date: May 2009
Posts: 4
Rewards Points: 10
Default

Blown-in Fiberglass Attic Insulation


If I understand foam application correctly the existing batts would have to be removed, if I were a young pup I'd go that route but I doubt if I would make it to the break even point at my age.
jdieter is offline   Reply With Quote
Old 11-21-2010, 08:46 AM   #14
Member
 
Join Date: Dec 2008
Location: South Western Ontario
Posts: 955
Rewards Points: 500
Default

Blown-in Fiberglass Attic Insulation


I had my roof replaced as an insurance claim about 15 years ago after a massive windstorm, but the roofer just took the job and reshigled. No extra vents, no inspection for airflow. The replacement shingles were really bad on the west side of the house within 12 years. He didn`t add or inspect my vents or recommend any soffit upgrades. This time around I wanted to insulate the attic as well so after re-roofing I read a lot, added ducting every 3rd space on my 4-12 pitch and increased the soffit vents to match.
There is a correct ratio of soffit to rooftop air flow. If you ignore that and restrict it with insulation you will be throwing money away. I believe that in my case my shingles aged premarurely as well. Either way, I blew in the attic myself , now R50. Even my second roofer didn`t address the lack of grilles in the soffit or inside attic area although he did increase the rooftop venting and inspect the attic before I insulated, and the guys at the pro desk where I get my materials had very little knowledge as well...Proper airflow will keep your house more moderate year round and help your attic function better. FYI I used recycled treated blown material and a rental.$300 for about 800 ft increased from R14-R50. Tough, dusty job but very satisfying. I would not want to try anything but blown with the 4-12 pitch
Chemist1961 is offline   Reply With Quote
Old 11-21-2010, 01:39 PM   #15
Member
 
Join Date: Dec 2008
Location: Fairbanks, AK
Posts: 1,847
Rewards Points: 1,000
Default

Blown-in Fiberglass Attic Insulation


I know it is more work and money, but.... No idea why your sheet rock has bowed, but if it were mine I would either accept the bows as artistic, or install 2x4 blocking to the trusses and screw the 'rock up to them, then blow in lots of cellulose. Robert Riversong (housewright.com) has been blowing in lots of cellulose w/ 1/2" 'rock, 24" OC for decades w/ no problems. Good luck. john

Advertisement

jklingel is offline   Reply With Quote
Reply


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
Adding Attic Insulation barneyrubble Building & Construction 2 08-23-2010 02:50 PM
rigid insulation under an attic storage floor? merlanvp Building & Construction 5 07-30-2010 08:32 PM
attic insulation question justin76 General DIY Discussions 6 01-23-2008 02:28 PM
Attic Insulation jim_arnau Building & Construction 13 11-07-2007 09:59 AM
Do I Need Attic Insulation? Carbo HVAC 9 09-16-2005 12:28 AM




Top of Page | View New Posts