[Equest-users] Thermal Mass Wall and R-Value

[Bishop, Bill]

At least one of the ICF companies is using "effective" R-values for
their products. I attended a Home Show recently and was told R-50 for a
concrete wall with only four inches of foam board:
http://www.arxx.net/ICF_INSULATED_CONCRETEFORMS_r50.htm
 
They claim benefits of thermal mass and reduced infiltration to justify
the value.
 
As Karen said, best to model the actual wall construction layers.
 
Regards,
Bill
 
William Bishop, EIT, BEMP, LEED(r) AP | Pathfinder Engineers &
Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Please strive to live sustainably.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Thursday, April 22, 2010 6:30 PM
To: Karen Walkerman
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Thermal Mass Wall and R-Value
 
I agree with Karen. I have another thought though: could this be an
insulating concrete form wall (ICF) wall? Google ICF for info.

Carol
On Thu, Apr 22, 2010 at 2:39 PM, Karen Walkerman <kwalkerman at gmail.com>
wrote:
The best thing to do is model the actual wall construction, not just an
equivalent R-value, then you will get both the thermal resistive and the
mass effect properties in the model.
 
--
Karen
 
On Thu, Apr 22, 2010 at 12:30 PM, Rob Hudson <rdh4176 at gmail.com> wrote:
That is the answer i was expecting to here.  thanks for your input
 
On Thu, Apr 22, 2010 at 12:27 PM, Bruce Easterbrook <bruce5 at bellnet.ca>
wrote:
That doesn't sound right.  Poured concrete has an R-value around
0.08/inch.  When "effective" is used commercially it normally is a hocus
pocus addition for the mass effect but shouldn't be much more than 10%.
eQuest would calculate it as a lag effect based on the mass, so a steady
state value would be most appropriate.
Bruce Easterbrook


On 22/04/2010 10:38 AM, Rob Hudson wrote: 
	When creating a model, i noticed that the R-value of the
concrete i am using is the "effective" R-value, rated at 22.  Should i
use this or should i ask the concrete manufacturer for a steady-state
R-value which will be much more accurate based on the materials?
	
	-- 
	Rob Hudson
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-- 
Rob Hudson

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