[Bldg-sim] New Rules of Thumb for Design Loads

[Dru Crawley]

Those old rules of thumb can mean significantly higher capital cost. I
remember a project in the DC area about 20 years ago. Their rules of thumb
came up with 10,000 tons (yeah a big building) ... but when a colleague did
a back of the envelope calc (in the days before we even hope for low-energy
buildings), he came up with 3,000 tons... and that was very conservative.
So the owner was about to (and did) pay for 3x the size needed and I'm
willing to bet the building rarely goes over 2,000 tons.


On Tue, Oct 29, 2013 at 2:57 PM, Christian Kaltreider <
ckaltreider at sudassociates.com> wrote:

> David, Dru, Jim,
>
> Thanks.  I will consider the DOE reference buildings as an option, at least
> for comparison.
>
> Jim, to answer your questions without getting into project details...We
> have
> been asked to give our opinion on the expected loads for a proposed
> building
> so the owner can have an idea of what impact it will have on their central
> plants.  We'll do this based primarily on similar past projects of ours.
> However, the owner has an on-site engineer who is using very old ASHRAE
> documentation to come up with his own (very high) design load estimates.
> Apparently ASHRAE used to publish sf/ton guidance for office buildings?  I
> would like to have some more current documentation to show the engineer to
> help support my explanation of why our prediction will be lower than his.
> Also, I think my wording concerning credibility came out wrong.  I
> certainly
> wasn't implying that my company isn't highly capable/credible.  But it's
> always nice to have a DOE report as backup documentation!
>
> Thanks for your help,
> Christian
>
> -----Original Message-----
> From: Jim Dirkes [mailto:jim at buildingperformanceteam.com]
> Sent: Tuesday, October 29, 2013 9:48 AM
> To: Christian Kaltreider; bldg-sim at lists.onebuilding.org
> Subject: RE: [Bldg-sim] New Rules of Thumb for Design Loads
>
> Christian,
> I suspect that you and your company are very credible and shouldn't
> hesitate
> to claim the truth of that.  Your client probably would not have retained
> you if that were not true!  It would be nice to have a 1000 building study
> from DOE, though :) I wonder why your client is asking?  There are so many
> design possibilities and at the end of the day, design load affects only
> equipment size (including the electricity and fuel services).  These, in
> turn, can be "managed" by choices for insulation, lighting, etc.
> Another thing to consider (after assessing your firm's liability from
> lawsuits) is that design loads occur infrequently in most climates, so much
> so that a full energy model analysis can sometimes show that the impact on
> comfort is minimal for a nominally UNDERsized HVAC system.
> It's a tangled web!  I think I'd ask the basis of their concern about peak
> load.
>
> James V Dirkes II, PE, BEMP, LEED AP
> www.buildingperformanceteam.com
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
>
> -----Original Message-----
> From: Christian Kaltreider [mailto:ckaltreider at sudassociates.com]
> Sent: Tuesday, October 29, 2013 9:21 AM
> To: Jim Dirkes; bldg-sim at lists.onebuilding.org
> Subject: RE: [Bldg-sim] New Rules of Thumb for Design Loads
>
> Jim,
>
> Thanks.  Yes, I can do my own little study, and I can also just look back
> at
> results from past projects.  That's a good suggestion.  But I was hoping to
> have something credible to reference (outside my own firm) for the owner.
>  I
> have seen DOE/National Lab comparisons of annual energy usage between the
> different versions of 90.1...I was hoping there might be something similar
> for design loads.
>
> Thanks,
> Christian
>
> Christian Kaltreider, LEED AP | Energy Analyst Sud Associates, P.A. | T
> 828.255.4691 | F 828.255.4949 | www.sudassociates.com
>
>
> -----Original Message-----
> From: Jim Dirkes [mailto:jim at buildingperformanceteam.com]
> Sent: Tuesday, October 29, 2013 9:11 AM
> To: Christian Kaltreider; bldg-sim at lists.onebuilding.org
> Subject: RE: [Bldg-sim] New Rules of Thumb for Design Loads
>
> Dear Christian,
> I do not know of any such resources!
> What do you think about creating a "typical" building and trying out
> various
> envelope, lighting, plug load and HVAC options in your climate to see the
> impact of each? That should not be too daunting a task.
>
> James V Dirkes II, PE, BEMP, LEED AP
> www.buildingperformanceteam.com
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Christian
> Kaltreider
> Sent: Tuesday, October 29, 2013 9:06 AM
> To: bldg-sim at lists.onebuilding.org
> Subject: [Bldg-sim] New Rules of Thumb for Design Loads
>
> Hello Group,
>
> Does anyone know of any articles/papers/publications which address peak
> design loads for buildings as energy codes evolve?  I am looking for basic
> rules of thumb for sf/ton (cooling) and btuh/sf (heating).  People use
> these
> rules of thumb all the time for initial assessments, sanity checks on
> simulation results, etc, but I'm not sure that the rules of thumb are being
> updated as energy codes become more aggressive.  For example, the engineers
> I have been around since I entered the engineering world (granted, that was
> only a few years ago) seem to always go back to 400 sf/ton as a standard
> value, then adjust up or down depending on building characteristics.  I
> haven't seen this  number change as buildings improve, or as I move to
> different climate zones.  To be clear, I am interested in design loads, not
> annual energy usage.
>
> (Note:  Before anyone lambasts me for even bringing up rules of thumb for
> design, I'll go ahead and say that I know they are gross estimations at
> best, and should be used with extreme caution and judgment.  Nonetheless, I
> see them used all the time, so I might as well get as good numbers as I
> can.
> And a project I am on right now actually requires it (by owner) in
> preliminary design.)
>
> Thanks for your help,
> Christian
>
>
> Christian Kaltreider, LEED AP | Energy Analyst Sud Associates, P.A. | T
> 828.255.4691 | F 828.255.4949 | www.sudassociates.com
>
>
>
>
>
>
>
> _______________________________________________
> Bldg-sim mailing list
> http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to
> BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
>
>
>
>
> _______________________________________________
> Bldg-sim mailing list
> http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to
> BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20131029/3c38ee33/attachment-0002.htm>