[Bldg-sim] ASHRAE 90.1 Definition of "Conditioned" - The PRM Reportfor LEED EAc1 and Appendix G Energy Model

[Ulrik Welle-Strand Horn]

Dear Mr. James V. Dirkes II:

Could you please clarify what you mean by "The definition depends only
indirectly on "U" values and wall areas?" I am not designing the mechanical
system, I am only reviewing it. Therefore I can't chose which spaces to
condition. The building has many rooms that don't have any cooling coils,
nor do they have any cold air entering the rooms. These must surely be
indirectly conditioned spaces?

For these indirectly conditioned spaces, I am wondering if I need to perform
the U-factor and surface area calculations and comparisons? The spaces in
question surely are not ventilated with 3 ACH from conditioned spaces. As
there are quite a few of these spaces, I just wanted to know if it is really
common practice to perform these calculations?

Thank you for a quick reply.

Sincerely yours,


*Ulrik Welle-Strand Horn *
Sustainability Engineer

*Silpa Inc.*
*s* i m p l e  .  *s* c i e n t i f i c  .  *s* u s t a i n a b l e
AMERICAS | MIDDLE EAST | ASIA
www.silpainc.com

India: +91.90080.96083

On Mon, Jan 12, 2009 at 9:06 PM, James V. Dirkes II P.E. <jvd2pe at tds.net>wrote:

>  Dear Ulrik,
>
> Regarding "conditioned space":
>
> "Conditioned space" seems pretty straightforward to me.  If, for example,
> the cooling system for a 10,000 sq.ft. space has 10 tons cooling capacity,
> then the capacity is 12Btu/hr/ft2 (10tons x 12,000 Btu/hr/ton / 10,000 ft2)
> This exceeds the ASHRAE threshold of 5 Btu/h/ft2, so it's "conditioned".  If
> the cooling system was only 4 tons, it would not be "conditioned" (only 4.8
> Btu/hr/ft2).
>
> The definition depends only indirectly on "U" values and wall areas.  For
> any given construction, you choose to provide an air conditioning system or
> not.  You can also choose to cool a lot or a little.  Each choice affects
> whether you end up with an air conditioning system greater than 5 Btu/hr/ft2
> or not.
>
> Heating works the same way, except the threshold varies by climate zone.
>
>
> *The Building Performance Team
> **James V. Dirkes II, P.E., LEED AP
> *1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
>
>
>
>  ------------------------------
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Ulrik Welle-Strand
> Horn
> *Sent:* Saturday, January 10, 2009 9:47 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] ASHRAE 90.1 Definition of "Conditioned" - The PRM
> Reportfor LEED EAc1 and Appendix G Energy Model
>
> Dear All,
>
> I would like to know if and how you consider ASHRAE's definition of
> conditioned space on page 13 of the 2004 version.
>
> Specifically, I am interested to know if you abide by this definition when
> listing the conditioned vs unconditioned area? The definition seems really
> specific to me, explaining how the system serving a conditioned area must
> have a certain capacity per square foot of building area served. It even
> goes on to explain how for some spaces one must consider the sum of the
> products of various U-factors and wall areas. To me, it does not seem like
> one can eyeball all these comparisons and definitions and therefore one has
> to go ahead and measure the capacities of systems and compare them with the
> area they serve, as well as do computations for rooms that might be
> indirectly conditioned.
>
> The PRM report for LEED requires you to list unconditioned and conditioned
> areas separately. Do any of you actually go through the calculations to find
> out if each single space in your project complies with the definitions put
> forward in the 90.1 document? It seems to me like more effort than what it's
> worth. I don't recall ever using this classification of unconditioned vs
> conditioned anywhere else in the LEED certification process. Especially, I
> don't recall ever having to use this definition to do the PRM model itself
> under Appendix G. Has anyone come across another place than the PRM report
> where the efforts of classifying their spaces accoring to the 90.1
> definition above has been rewarded? Please also let me know if any one of
> you have ever experienced trouble getting your project LEED certified
> because of lack of compliance with this definition.
>
> Lastly, the definition explicitly states that "Crawlspaces, attics, and
> parking garages with natural or mechanical ventilation are not considered
> enclosed spaces." Do most of you usually leave out car parks from the PRM
> area report? I am working on a building where about 60% of the floor area is
> parking space, meaning the sum total in my Space Summary will be much less
> than stated otherwise in the documents submitted to USGBC. I know that they
> are looking for all the total areas to be pretty consistent, and that some
> people experience problems when thes total areas don't match up. Has anyone
> ever dealt with this issue? If so, how did you deal with it?
>
> I appreciate any response you may have to any or all of my questions.
>
> Sincerely yours,
>
>
> *Ulrik Welle-Strand Horn *
> Sustainability Engineer
>
> *Silpa Inc.*
> *s* i m p l e  .  *s* c i e n t i f i c  .  *s* u s t a i n a b l e
> AMERICAS | MIDDLE EAST | ASIA
> www.silpainc.com
>
> India: +91.90080.96083
>
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