[Bldg-sim] why the autosized design air flow rate differ so much in different floor?

[Nick Caton]

An extension of Robert’s advice:  Check your first floor’s inputs for increased infiltration loads the second floor does not have.  This behavior may be normal, considering doors/vestibules/windows.

I don’t think I’m totally following your exhaust strategy, but another general caution per your word choice:   You may not want to have a “roof” on your first floor.  If you ultimately do have a  roof (exterior) surface sandwiched between your floors (easy mistake if you defined each floor as a separate shell), you have possibly nearly doubled your roof loads for the building.  Much further discussion on this and how to handled inter-floor heat transfer in the archives, but planes sandwiched between shells should generally be either interior surfaces of some sort (air/framed/adiabatic), or deleted.

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of ??
Sent: Sunday, February 26, 2012 11:36 PM
To: RobertWichert
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] why the autosized design air flow rate differ so much in different floor?

I think I have known one of the reasons( if more than one).
I set a self-defined wall in the Wizard data edit mode, using the R value definition. However, the R value automatically became U value under Detailed data edit mode. So the roof heat conduction is very large. Besides, I set a ceiling in the second floor which exhaust the hot air out, so the roof conduction load in the second floor is zero. These settings caused the first floor load much larger than the second floor.

At 2012-02-27 01:32:12,RobertWichert <robert at wichert.org<mailto:robert at wichert.org>> wrote:

Five to ten times?  Check your occupancy carefully.  It sounds like outside air to me.  You either have no occupants on the second floor or ten times the occupants on the first floor.




Robert Wichert P.Eng. LEED AP

+1 916 966 9060

FAX +1 916 966 9068















===============================================

On 2/26/2012 4:42 AM, James Hansen wrote:
It's almost surely your first floor slab.  The default configuration and U-value for these constructions are usually very poor.

-James

On Feb 26, 2012, at 7:31 AM, "韩星" <foolishstar at 163.com<mailto:foolishstar at 163.com>> wrote:
Hi, every body,

I now have a difficult problem. I found that the autosized design air flow in the first floor is much larger than the second floor, about 5-10 times of the second floor. I cannot figure out the reason, because the indoor lighting, equipment power and the occupant density are all the same for the two floors.
In my opinion, the second floor should have a higher air-conditioning load than the first floor because it is the building's top floor. But the result is just the opposite.
I really want to know the reason and how I should deal with it.
Thanks
Xing

_______________________________________________
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<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>
________________________________
The information contained in this communication is confidential, may be privileged, and is intended only for the use of the addressee.  It is the property of GHT Limited.  Unauthorized use, disclosure or copying of this communication or any part thereof is strictly prohibited and may be unlawful.  If you have received this communication in error, please notify me immediately by return e-mail or by e-mail to ght at ghtltd.com<mailto:ght at ghtltd.com>, and destroy this communication and all copies thereof, including all attachments.  Thank you. <http://twebmail.mail.163.com/js4/index.jsp?sid=UDYFdguCzYsIyLszvuCCSyCZdvNvhKtL>



_______________________________________________

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<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20120227/6ec2be18/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 1459 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20120227/6ec2be18/attachment-0002.jpg>