[Greenbuilding] [BULK] Re: underfloor insulation R-values & materials

[Lawrence Lile]

It won't save one BTU of energy to insulate between floors if the two floors are the same temparature. Heat loss doesn't occur because of volume,  heat loss happens across exterior walls because of temperature differences.   
 
This myth of "heating volume" is one of the most pervasive myths about heat transfer.  After carefully calculating I needed a 1.5 ton AC unit for an extremely efficient, but large, house, an HVAC contractor told me "We use 3 tons for a house of that volume."  He could not be convinced that heat flow doesn't go to volume, but goes from hot to cold.  
 
That being said, many people insulate between floors for noise control.  Bedroom above a kitchen?  Good place for a little insulation.  Party wall between two tenants?  Definitely a good place for insulation.  Npisy teenager bedroom?  Another good spot.
 
Also, if you are able to shut down whole rooms, and insulate the interior walls from the rest of the house, you might be able to save some energy, because you are effectively doubling the insulation between you and the outdoors.  I can't imagine this would be very cost effective though. 
 
 
--Lawrence Lile
 

________________________________

From: greenbuilding-bounces at listserv.repp.org on behalf of John Messerschmidt
Sent: Fri 12/1/2006 1:07 PM
To: greenbuilding at listserv.repp.org
Subject: [BULK] Re: [Greenbuilding] underfloor insulation R-values & materials



Speaking of floor joists, does it make any sense to insulate between floors
inside the building envelope?  There are 8" of empty space there, that I
would rather not heat, but with the cost of insulation, maybe the
cost/benefits wouldn't be worth it.  There are also noise considerations.
Any ideas or comments?




-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Lawrence Lile
Sent: Wednesday, November 29, 2006 6:50 PM
To: Alan Abrams; Don Jennings
Cc: greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] underfloor insulation R-values & materials

I'd keep the cellulose out of basements.  It loves moisture, and looks
like a good platform to launch the next wave of mutant molds from Mars.
Only use it where it can dry out.  They don't even recommend using vapor
retarders with it! 





Lawrence Lile, P.E., LEED AP
Senior Electrical Engineer
Project Solutions Engineering
573-443-7100 X 221
573-999-3450 Cell
1390 Boone Industrial Dr Suite 200
Columbia MO 65202

-----Original Message-----
From: Alan Abrams [mailto:alan at abramsdesignbuild.com]
Sent: Wednesday, November 29, 2006 4:28 PM
To: 'Don Jennings'; Lawrence Lile
Cc: greenbuilding at listserv.repp.org
Subject: RE: [Greenbuilding] underfloor insulation R-values & materials

>
> Wet Spray cellulose is your friend.  Cheap, 100% recycled, always
fills
> up gaps and odd shapes unlike Batts, you can spray it upside down into
> an overhead space (usually through a screen that looks like mosquito
> net)  It will fill up any shape space, and it is better R value than
> most of the alternatives.  The only thing better is biobased (made
from
> soybeans) foam, but the price is steep.

LL-

I agree with you in principle about the use of cellulose.  Please
consider
this, however: 

We've been insulating existing basements by furring out the perimeter
walls
with 1 5/8" metal studs held 2" off the wall, and foaming (with icynene
or a
clone) between and behind the studs.  If there's a moisture problem we
install a conventional subslab perim drain and line the walls with
enkdrain
(down to the subdrain) before patching the slab and installing furring.

What do you think about substituting cellulose in a case like that?

Cheers-
-AA 



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