[Bldg-sim] Unusual Result

[Jaigath Chandraprakash]

Thank you Karen, Joe, and everyone for your advice. 

To answer your question if the building has an economizer, no it does not have 
an economizer. I have also asked the mechanical designer regarding the 
electrical load in his design criteria and he did confirmed that his assumptions 
are typical for this type of building. I am really tempted to adjust the 
electrical load because it is too high compared to typical offices and I agree 
with you Karen that equipment do runs only at a fraction of the day.


Thanks again,

Jaigath 




________________________________
From: Karen Walkerman <kwalkerman at gmail.com>
To: Jaigath Chandraprakash <cjaigath at yahoo.com>
Cc: bldg-sim at lists.onebuilding.org
Sent: Fri, September 24, 2010 7:14:47 PM
Subject: Re: [Bldg-sim] Unusual Result

If most of your cooling loads come from internal loads as you said, then having 
windows with a higher U-value allows the building to lose heat to the outside 
any time it is cooler outside than inside.  If you look at ASHRAE 90.1, the 
requirements for windows changes dramatically as you move from colder to warmer 
zones.  In warmer zones, the allowed U-value is higher, but the SHGC is lower. 


Also, it is usually good to verify that this is actually the case, often 
installed equipment runs only a fraction of the day, or at a fraction of the 
peak energy use.  If your internal loads are not actually as high as you are 
modeling, this could change things.

Lastly, does the building have an economizer?  This may make sense for this 
particular project.

--
Karen


On Fri, Sep 24, 2010 at 5:59 AM, Jaigath Chandraprakash <cjaigath at yahoo.com> 
wrote:

The project I am working on is an office building that operates 20 hrs per day 
with most of the loads occuring at night and low occupancy on daytime. It is a 
cooled by a DX roof unit and has a very high internal load. No heating equipment 
is required because the building is in Climate 1. I was surprised that when I 
changed my window U-value from 0.3 to 0.7 I got less cooling consumption. I 
always thought that getting low u-value will give me less coling consumption. 
Can somebody tell me why I am getting less cooling when I use a higher window 
U-value?
>
>Thanks,
>
>Jaigath
>
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