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

[Dahlstrom, Aaron]

Christian -



If the key issue is the vintage of the ASHRAE information used to estimate the loads per square foot - I am curious if ASHRAE has updated the loads per square foot check figures published in their ASHRAE Pocket Guide<http://www.techstreet.com/ashrae/products/1703568>. I have a 2001 and 2009 vintage: the 2009 version updates the Expected Lighting & Equipment Heat Gain (Office goes from 4 / 6/ 9 W/sf to 2 / 2.5 / 4 W/sf, low/med/hi) but keeps the expected Refrigeration density the same (360 / 280 / 190 sq ft / ton).



I wonder if the Refrigeration values in the current edition match the refrigeration values in the reference your client's in-house engineer is using.



Aaron



Aaron Dahlstrom, PE, LEED(r) AP

In Posse - A subsidiary of AKF| 1500 Walnut Street, Suite 1414, Philadelphia, PA 19102

d: 215-282-6753| m: 267-507-5470| In Posse: 215-282-6800| AKF: 212-354-5656

e: ADahlstrom at in-posse.com | in posse web: www.in-posse.com | akf web: www.AKFGroup.com





-----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 2:57 PM
To: 'Jim Dirkes'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] New Rules of Thumb for Design Loads



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<mailto: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<http://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<mailto: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<http://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<mailto: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<http://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>

[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<mailto: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<http://www.sudassociates.com>













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