Forums | Home Repair | Home Improvement | Painting | Interior Decorating | Remodeling | Landscaping


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

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

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-23-2010, 12:25 PM   #1
Newbie
 
Join Date: Aug 2010
Posts: 6
Share |
Default

Over or under insulation in attic?


Is it better to run electrical wires over or underneath the insulation in the attic?
PhillyRyan is offline   Reply With Quote
Old 08-23-2010, 07:17 PM   #2
Member
 
dSilanskas's Avatar
 
Join Date: Mar 2008
Location: Cape Cod, Massachusetts
Posts: 474
Default

Over or under insulation in attic?


six on one hand half dozen on the other. It doesn't matter but it looks better if it's under.
dSilanskas is offline   Reply With Quote
Old 08-23-2010, 08:08 PM   #3
Member
 
Join Date: Jan 2010
Location: Saskatoon Sk. Canada
Posts: 391
Default

Over or under insulation in attic?


Your cable may need to be derated(increased in gauge)when run on the hot side of the insulation.
daveb1 is online now   Reply With Quote
Old 08-23-2010, 08:18 PM   #4
Member
 
dSilanskas's Avatar
 
Join Date: Mar 2008
Location: Cape Cod, Massachusetts
Posts: 474
Default

Over or under insulation in attic?


V
Quote:
Originally Posted by daveb1 View Post
Your cable may need to be derated(increased in gauge)when run on the hot side of the insulation.
Derating your wires due to the insulation in a house? Im sorry but that has to be the ??????????? i've ever heard....

Last edited by beenthere; 08-24-2010 at 02:11 PM. Reason: Rephrased teh staement to be more polite
dSilanskas is offline   Reply With Quote
Old 08-23-2010, 08:47 PM   #5
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,450
Default

Over or under insulation in attic?


Quote:
Originally Posted by dSilanskas View Post
V
Derating your wires due to the insulation in a house? Im sorry but that has to be the most stupid thing i've ever heard....
Um, what? Ambient temperature is a necessary factor to consider for derating. If putting the wire on the outside of the insulation exposes it to very high temperatures in the attic, it may need to be derated. With that said, it will not USUALLY be necessary to derate because of this, and most people ignore it.
mpoulton is offline   Reply With Quote
Old 08-23-2010, 08:58 PM   #6
Member
 
dSilanskas's Avatar
 
Join Date: Mar 2008
Location: Cape Cod, Massachusetts
Posts: 474
Default

Over or under insulation in attic?


Quote:
Originally Posted by mpoulton View Post
Um, what? Ambient temperature is a necessary factor to consider for derating. If putting the wire on the outside of the insulation exposes it to very high temperatures in the attic, it may need to be derated. With that said, it will not USUALLY be necessary to derate because of this, and most people ignore it.
Magnetic everyone ignores it because no need to derate in an attic. If it was such an issue than why isn't there ever issues with the way we (electricians) wire houses. Never ever have i had to derate while running my wires in attics. Its just not needed
dSilanskas is offline   Reply With Quote
Old 08-24-2010, 08:10 AM   #7
Newbie
 
Join Date: Aug 2010
Posts: 6
Default

Over or under insulation in attic?


It seems if you put it over the insulation then it would be exposed to much higher temperatures but if you bury it under the insulation so that it's almost right against the cooled part of the house, then it wouldn't be able to disipate the heat that's generated in the wire itself due to current. So which is worse, the ambient heat of the attic or the heat from the current??
PhillyRyan is offline   Reply With Quote
Old 08-24-2010, 08:59 AM   #8
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,781
Default

Over or under insulation in attic?


At the attic floor the temperature should not be too bad. I would just go by the NEC (RE cable spacing) and not bother to derate the cables simply because of the attic temperature.
__________________
The average homeowner who lost his house in the Oklahoma tornadoes should move for good and not rebuild. Too much complexity watchdogging the contractor. Too much a chance to be defrauded.
AllanJ is offline   Reply With Quote
Old 08-24-2010, 11:36 AM   #9
Registered User
 
Join Date: Mar 2009
Posts: 9,886
Default

Over or under insulation in attic?


"Secure within 12" of box & maximum 4-1/2' intervals --- 3702.1 '06 IRC 314.17C '08 NEC(not to the insulation) right below de-rating from the manufacturers stamp: http://books.google.com/books?id=eLo...0attic&f=false
Remember the boards within 6 &7' of the access.

Be safe, Gary
__________________
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!
Gary in WA is offline   Reply With Quote
Old 08-24-2010, 02:10 PM   #10
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 23,491
Default

Over or under insulation in attic?


Quote:
Originally Posted by dSilanskas View Post
V
Derating your wires due to the insulation in a house? Im sorry but that has to be ??????????? thing i've ever heard....
Strange. Wire is rated by the ambient temp it is installed in.

While low draw circuits aren't usually effected. Higher current drawing devices are.
beenthere is offline   Reply With Quote
Old 08-24-2010, 02:24 PM   #11
zpm
yeah, right
 
Join Date: Jan 2009
Location: California
Posts: 142
Default

Over or under insulation in attic?


Quote:
Originally Posted by AllanJ View Post
At the attic floor the temperature should not be too bad.
That depends on where you live.
For my house, on a 100 degree day with the A/C running
The temp at the peak can top 125.
The temp above the insulation can hit 105.
The temp under the insulation against the sheetrock is about 80.
__________________
Honey, does this tool belt make me look FAT?
zpm is offline   Reply With Quote
Old 08-24-2010, 09:36 PM   #12
Inspector/Instructor
 
codeone's Avatar
 
Join Date: Dec 2009
Location: NC
Posts: 369
Default

Over or under insulation in attic?


Quote:
Originally Posted by dSilanskas View Post
V
Derating your wires due to the insulation in a house? Im sorry but that has to be the ??????????? i've ever heard....
This has already been taken into account with NM cable having to be rated out of the 60 degree column. and now for se and ser when run in the interior of a house in insulation with the 2008 NEC.
codeone 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
Attic Insulation gruntman Roofing/Siding 12 12-04-2010 09:01 PM
Remove old attic insulation and critter mess? merlanvp Building & Construction 6 07-27-2010 04:36 PM
Attic insulation and soffit venting zacker Building & Construction 1 07-15-2010 10:17 PM
Finishing Attic, insulation question pjgsteelers Remodeling 1 07-13-2010 01:59 PM
adding attic insulation to existing insulation strouddljs General DIY Discussions 4 11-09-2009 05:06 PM




Top of Page | View New Posts

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