[Equest-users] wwr calculation

[James Hansen]

I don't think I agree with this advice

 

Under ASHRAE 90.1-2007, Section 5.2.1, part of the requirements for the PRESCRIPTIVE method requires that "the vertical fenestration area does not exceed 40% of the gross wall area for each space-conditioning category". 

 

The definition for "space conditioning category" simply says:

 

                non-residential conditioned space,

                residential conditioned space, and

                nonresidential and residential semiheated space

 

It doesn't list unconditioned space.  Now I know this info is listed in the prescriptive requirements, but if it was my model, and I had a garage that had 100% window area, there is no way I would count that towards the gross WWR, particularly if I was applying for LEED, and these inconsequential windows pushed my WWR above 40% and thus penalized my proposed building.  In fact, I might not even model the windows, unless I felt they were going to superheat the garage and start impacting adjacent space cooling loads.

 

Just my opinion...

 

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James Hansen, P.E., LEED AP
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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of PKConsulting
Sent: Wednesday, October 19, 2011 4:04 PM
To: deepika khowal
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] wwr calculation

 

It doesn't change for unconditioned or conditioned.  It is only a function of gross wall area (ft2) and window area (ft2).   Don't think too hard about this.  You are looking for a needle in the wrong haystack.   This one is straight forward with no tricks...

 

WWR is for whole bldg not space by space.


Pashalu


On Oct 19, 2011, at 12:20 PM, deepika khowal <deepika.khowal at gmail.com> wrote:

	Thanks Pasha

	 

	yes , i have been using LV-d report.

	 

	Am confused how it work for an unconditioned space.

	Thanks

	On Wed, Oct 19, 2011 at 11:01 AM, PKConsulting <pasha.pkconsulting at gmail.com> wrote:

	It should be the gross wall area for everything above ground.  Use the lv-d report to find the numbers to calculate the overall WWR for your entire bldg.   There is a summary page at the end of the lv-d report.  Look for the line called-'all walls'.  You can use those numbers to calc WWR percentage.
	
	Pashalu

	
	On Oct 19, 2011, at 11:39 AM, deepika khowal <deepika.khowal at gmail.com> wrote:
	
	> Hi all
	>
	> I have a question about calculating WWR.
	> for example, if the south wall area is 700sf and total window area is 70sf then the WWR should be 10%.
	> but if 50% of south wall is part of a garage and is unconditioned, then in calculating WWR , should I include only the wall area for conditioned space or it should include complete facade?
	> Thanks
	>
	> Deepika
	>
	>
	>
	>

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