ASHRAE 09.1-2007 Requirements for Baseline Wall Density

Wes Lawson

Mechanical Engineer

Bala Consulting Engineers

LEEDuser Basic Member

4 thumbs up

February 28, 2013

Hi all, I am performing energy simulations for my baseline and proposed buildings for EAc1 (and EAp2). Can anyone help me out with the baseline wall density (lb/ft^3) that I should be using? Per ASHRAE 90.1-2007, Table 5.5-4 (Building Envelope Requirements for Climate Zone 4), the above-grade, steel-framed wall for non-residential buildings has a U=0.064. What is the corresponding wall density for this type of wall? Does ASHRAE 90.1-2007 say what to use for the baseline wall density? Also, any suggestions on what to use for an aluminum metal panel wall system (my proposed deisgn) would be great. Thanks!

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 02/28/2013 - 22:21

Are you looking for a specific number or just something like light, medium or heavy? Steel-framed would be light. If your software is asking for a specific number I would expect to be able to find default values within the software to use. If you can't find what you need within your software or its user manual Chapter 26 in ASHRAE Fundamental lists the density of a wide variety of building materials so you could add it up. The density is there to account for the thermal mass and 90.1 does not specify a specific value to be used for this effect. In fact the density of the walls could be very different between the baseline and proposed.

Wes Lawson

Mechanical Engineer

Bala Consulting Engineers

LEEDuser Basic Member

4 thumbs up

Thu, 02/28/2013 - 22:46

Hi Marcus, Thanks for the reply. I will use Chapter 26 of ASHRAE Fundamentals for my proposed design wall density. Could you provide me with light, medium, and heavy ranges? For the baseline I will use the light density since I am using a steel-framed wall. Do you typically provide a density a for the baseline wall construction? A colleague of mine told me that he does not. Is he correct? Wouldn't this skew baseline results in comparison to the proposed design? Please let me know. Thanks!

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Fri, 03/01/2013 - 19:56

As I understand it some software uses the light, medium, heavy designation and I would assume the software would designate the range. I did a quick search in some of our older load calculation manuals and Carrier lists the range for wall assemblies from 20 to 140 lbs/ft3. Technically the density should be entered for the baseline wall. The reality is that for steel-framed it makes little difference since the density is so low. If you do not enter it for both then it will not account for any thermal mass effect. Typically this is neutral (steel-framed in the proposed) or benefits the savings (masonry construction in the proposed) in many project types so not accounting for it tends to be neutral or hurts the overall energy savings so the result is conservative and the reviewer would not likely comment.