[BLDG-SIM] Loads not met interpretation in ASHRAE 90.1-2004

Xiaobing Liu XLiu at climatemaster.com
Tue Jul 10 09:32:34 PDT 2007


Kristin:

Thanks for your reply. I will forward your response to the list.

If the standards only address sensible load, I'm wondering whether the Unmet Load Hours is sufficient to evaluate the performance of a HVAC system, especially in humid climate where indoor humidity control is an essential part of the HVAC system. Since indoor humidity control may consume significant energy depending on the equipment/system used, I think the unmet latent load or the indoor humidity level should also be accounted for in the building energy performance evaluation to get fair comparison between proposed and baseline building designs.

Xiaobing

-----Original Message-----
From: Kristin Field [mailto:fieldkm at yahoo.com]
Sent: Tuesday, July 10, 2007 11:10 AM
To: Xiaobing Liu
Subject: Re: [BLDG-SIM] Loads not met interpretation in ASHRAE 90.1-2004


Xiaobing,

I tried to send this email to the list, but there's a
glitch that doesn't allow my messages to get through. 
Anyway, here's my response for you at least:

My interpretation is that the standard is addressing
sensible load only and that it is for building-wide
hours of load unmet, not by zone.  Anyone disagree?

For eQUEST/DOE-2.2, this would mean that I'd say to
use the number on the BEPS report instead of from the
SS-R reports (although those are very helpful to look
at for other reasons).

Kristin Field

--- Xiaobing Liu <XLiu at climatemaster.com> wrote:

> All:
> 
> Regarding the Unmet load, is it for sensible load
> only or total load (sensible and latent)?
> 
> Xiaobing
> 
> -----Original Message-----
> From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com]On
> Behalf Of Perron,
> Brett
> Sent: Tuesday, July 10, 2007 9:47 AM
> To: BLDG-SIM at gard.com
> Subject: [BLDG-SIM] Loads not met interpretation in
> ASHRAE 90.1-2004
> 
> 
> John,
> The few LEED projects I've modeled for (3), we've
> used unmet load for
> hours for the whole building.  I like to use the
> Summary Tab under the
> Air-Side HVAC screen to view details about my
> systems including unmet
> load hours.  The only thing is that it's only
> available for the baseline
> design and can't compare with any parametric runs.
> Hope this helps, 
> Brett
> 
> -----Original Message-----
> From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com]
> On Behalf Of Rohini
> Brahme
> Sent: Tuesday, July 10, 2007 10:12 AM
> To: BLDG-SIM at gard.com
> Subject: [BLDG-SIM] Loads not met interpretation in
> ASHRAE 90.1-2004
> 
> I usually look through the zone report (SS-H? - the
> one which shows the
> undercooled or underheated hours for each zone) to
> see if any zone has
> unreasonably high numbers. Fixing these zones
> usually gets me a very low
> number for unmet hours for the total of all zones. I
> would be curious to
> see what others have to suggest. In your case, going
> through 76 zones
> would be quite tedious.
> - Rohini
>  
> All:
>  
> ASHRAE 90.1-2004 has design criteria for Equipment
> capacities on Page
> 176 of the Standard (G3.1.2.2). It talks about Unmet
> load hours on the
> proposed design AND the baseline design not
> exceeding 300 hrs (of 8,760
> Hrs), and the delta between base and proposed not
> differing more than 50
> hours.
>  
> Is this WHOLE BUILDING, or BY ZONE? I have 76 zones
> in my building, and
> to play the Unmet loads game between these two
> models is harder than
> trying to hold water in my hands.
>  
> Any thoughts, interpretations, or suggestions?
>  
> John R. Aulbach, PE, CEM
> Project Manager
> Nexant, Inc.
> 100 North Barranca, Suite 820
> West Covina, CA 91791 USA
> Phone: 626-430-9054
> Fax: 626-430-9060
> email: jaulbach at nexant.com
>  
>  
>  
> 
> 
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