[Bldg-sim] Vented cavity behind brick or precast panels and effective R-value

[Chalfoun, Nader V - (chalfoun)]

This might be useful.  In this paper, the cavity wall was tested on stud wall and not on masonry walls.  Benefit of applying the cavity wall strategy resulted in adjusting the outside heat gain/loss film coefficient by convection from the surface while reduced the solar absorptance acted as a shading element to the existing wall.  A 5.8% saving in cooling load in a hot-arid climate of Tucson Arizona was achieved.


To get an equivalent effective R-Value, sometimes you may run the simulation again, increasing the R-value of the existing wall until you achieve the 5.8% reduction in cooling (not sure if it works in all cases?)


Nader

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From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> on behalf of Michael Hsueh <mhsueh at integralgroup.com>
Sent: Friday, March 4, 2016 2:23 PM
To: Keith Swartz; Jones, Christopher; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Vented cavity behind brick or precast panels and effective R-value

John Straube has a white paper floating out there specifically about the reduction of insulation R-value as a function of air circulation in cavities. I’d go check out the BSC website (or RDH, which they’re a part of now) to see if it’s available (or email them to point you to that publication).


Michael Hsueh | Integral Group | T 510.663.2070 ext 2041 | D 510.457.0141
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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Keith Swartz
Sent: Friday, March 04, 2016 1:16 PM
To: Jones, Christopher <Christopher.r.Jones at wspgroup.com>; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Vented cavity behind brick or precast panels and effective R-value

Christopher,

The ASHRAE Handbook has a section about thermal resistance of air spaces. See the 2013 Fundamentals Handbook starting on p. 26.12. Is that what you are looking for?

Keith Swartz, PE | Senior Energy Engineer
Seventhwave
608.210.7123 seventhwave.org

From: Jones, Christopher [mailto:Christopher.r.Jones at wspgroup.com]
Sent: Friday, March 04, 2016 12:52 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] Vented cavity behind brick or precast panels and effective R-value

Is anyone aware of any analyses of the effective insulation properties of brick or precast veneer with a vented air space? I assume the air in that cavity is moving slowly but it isn’t completely still therefore you can’t include all of the insulative properties of those two layers on the outside of a wall?


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Christopher Jones, P.Eng.
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