[Equest-users] peak heating demand

[Alex Krickx]

My response to Deepika was offline - I meant to share it with the list:

Windows will affect the peak loads of heating and cooling systems. I would consider the cost/sizing implications of both heating and cooling systems AND annual energy costs in figuring out which system is most cost-effective.

Cheers,
Alex

From: Arpan Bakshi [mailto:arpanbakshi at gmail.com]
Sent: Wednesday, May 18, 2011 3:08 PM
To: deepika khowal
Cc: Alex Krickx; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] peak heating demand

Deepika

Sizing is based only on peak load or what is also called design load.

Building A could have a peak load which is half of Building B, but if Building A is running its systems at peak capacity 24/7, its annual energy use could be many times that of Building B.



Arpan Bakshi, LEED AP BD+C
YRG sustainability

On May 18, 2011, at 5:44 PM, deepika khowal <deepika.khowal at gmail.com<mailto:deepika.khowal at gmail.com>> wrote:
Thanks Alex
I think the explanation you gave was very clear.
so when we design HVAC system, which loads we should consider?
for windows with better R-values, the peak load may b lesser but its overall annual demand will be higher.
how to account for this in HVAC sizing?

On Wed, May 18, 2011 at 12:02 PM, Alex Krickx <akrickx at seriousmaterials.com<mailto:akrickx at seriousmaterials.com>> wrote:
Hi Deepika,

I’m not sure how eQUEST calculates loads, but I can imagine a scenario where your results make sense:

Peak heating load probably happens at night/early in the morning, right? So it probably depends on insulation (R-value) and not solar gains (SHGC). My guess is the window with the higher peak demand has low R-value (since you need lots of heat to make up for losses). But this window could have a high SHGC, so when the sun is out you benefit from passive heating (and have lower annual heating demands).

I’m guessing your other window (with lower peak heating) has a better R-value - it retained heat better. This window may have a lower SHGC (possibly due to additional low-e coatings) and so it get less passive heating throughout the year and needs more heat to be added to the building during daytime hours.

This will depend on the windows you’ve modeled, building type and climate. Perhaps if you share some more info on the project the answer will present itself.

Regards,
Alex Krickx

Alex Krickx, LEED AP
Building Energy Specialist
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1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124<tel:408.541.8124>

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From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of deepika khowal
Sent: Wednesday, May 18, 2011 11:19 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] peak heating demand

Hi all
I am modeling the performance of different glazing types in a building.
I realized for one glazing, the peak gas demand is lower than other glazing but total heating energy is higher?
how does equest calculate these loads and energy?
Thanks


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