EcoRenovator  

Go Back   EcoRenovator > Improvements > Conservation
Advanced Search
 


Blog 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 12-18-09, 05:05 PM   #1
tasdbois
Lurking Renovator
 
Join Date: Oct 2008
Location: Mirabel, QC
Posts: 28
Thanks: 0
Thanked 0 Times in 0 Posts
Default Conduction, convection and radiation

Convection is usually not much of an issue in house insulation when everything is sealed but under rare circumstances. The thicker the better as far as conduction is concerned. But what about radiation?

I am wondering what kind of heat loss from the house in cold weather is due to radiation. I'm getting a house built, so I'll make sure it's well sealed and the r value is decent, but I'm wondering whether or not a radiant barrier would be worthwhile. BTW I live in a very cold climate.

tasdbois is offline   Reply With Quote
Old 12-18-09, 05:14 PM   #2
Daox
Administrator
 
Daox's Avatar
 
Join Date: Aug 2008
Location: Germantown, WI
Posts: 5,519
Thanks: 1,157
Thanked 374 Times in 305 Posts
Default

Convection can happen through/inside fiberglass as the temperature differential increases. I'd recommend staying away from it.

http://ecorenovator.org/forum/conser...uantified.html

I haven't seen amazing proof that radiant barrier is really all that great. According to the studies I've seen, its more effective as you have less and less conventional insulation. This makes sense since the savings from the radiant energy would be a larger and larger percentage of the energy saved. With high a high r-value enclosure, the benefits of radiant barrier appear to be quite small. Unfortunately, I don't have time to dig up the article I'm referring to, but I'll get it when I can.
__________________
Current project -
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Daox is offline   Reply With Quote
Old 12-18-09, 07:24 PM   #3
tasdbois
Lurking Renovator
 
Join Date: Oct 2008
Location: Mirabel, QC
Posts: 28
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Thanks for the comment. I've read through a lot of stuff linked over at builditsolar.com and the only convection issue I could find was with loose fill fiberglass. I'm supposed to get batt insulation in the walls and cellulose in the attic, but I'll inquire about using cellulose in the walls too.

With 2 by 6 outer walls construction and batts insulation I get r21 walls with not much space to add more stuff to increase the r value in a cost effective way. I was just wondering if adding thin radiant barriers could help in a significant way. I've read that it should help, but just thought i'd ask here for your opinion.
tasdbois is offline   Reply With Quote
Old 12-18-09, 08:38 PM   #4
GaryGary
Apprentice EcoRenovator
 
Join Date: Nov 2008
Location: SW Montana
Posts: 139
Thanks: 1
Thanked 21 Times in 15 Posts
Default

Hi,

The R21 or R19 quoted for FG insulated 2X6 walls is figured as though the wall had no studs or other thermal bridges. In reality what you get on a real wall is more like R14. One way to get around this is to use rigid foam board on the outside under the siding -- the foam board has no thermal bridges.

Adding 1 inch rigid foam board takes the R14 up to R18.4.

See the "Whole Wall Heat Loss Calculator" on this page:
Heat loss and energy simulation software

Another good wall is the Mooney wall:
Mooney Wall -- A low cost, high R value wall
The pictures show the Mooney straping applied to a 2X4 stud wall, but you could just as easily use it on a 2X6 stud wall.

I would seriously consider dense packed cellulose in the walls rather than FG. To me, there is no reason to believe that the same kind of convection losses you get in loose fill FG would not occur in bat FG. Its alos takes a whole lot of care to fit FG bats well enough to avoid gaps etc., and most insulation guys are not going to take the time to do it.

Gary
GaryGary is offline   Reply With Quote
Old 12-19-09, 07:53 AM   #5
Xringer
Lex Parsimoniae
 
Xringer's Avatar
 
Join Date: Feb 2009
Location: Woburn, MA
Posts: 4,897
Thanks: 111
Thanked 248 Times in 228 Posts
Default

If I was "getting a house built" in a cold climate, I would really worry about windows.
Make sure they are the best you can get and limit the amount on the north side,
or those that can't see much sun during the day.

The north side of my home has an add-on Den. The sliding Anderson windows keep that room extra cold all winter!
I am now considering adding another layer of glass over them.
Storm Windows ? Rolling Storm Window by Harvey

The sliding Anderson windows come packed with buyers remorse.
They leak and double pane just isn't enough for shaded areas when it 10 deg outside..

Xringer 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

Forum Jump


All times are GMT -5. The time now is 08:09 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design