[Equest-users] wwr calculation

James Hansen JHANSEN at ghtltd.com
Thu Oct 20 03:51:26 PDT 2011


I model garages all the time.  I haven't done a building in a while that
didn't have some sort of conditioned space in the garages that needed an
adjacent unconditioned space (but without exterior walls) to properly
analyze.  Plus for LEED these days, they want all of your building areas
in the model to match those entered by the architect in the PI forms.
So you are supposed to model garage elevator lobbies, semi-heated
mechanical spaces, main electric rooms, unheated garage space, etc.  

 

Also, my garage at work has windows :)

 

-James

 

From: Pasha Korber-Gonzalez [mailto:pasha.pkconsulting at gmail.com] 
Sent: Thursday, October 20, 2011 6:33 AM
To: deepika khowal
Cc: James Hansen; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] wwr calculation

 

I disagree with both of you.

First of all, who models Garages in their models anyway?  What a waste
of time.---this scews the gross floor area, and nothing in a parking
garage impacts the HVAC equipment loads of the conditioned spaces....you
can always input your garage vent fans and lighting as single exterior
load input numbers in your model which simplifies the whole modeling
project and billable time spent WITHOUT compromising on the calculations
of energy use....

Second of all---poor example for offering windows in a parking
garage--this is never real life, and a non-applicable example doesn't
"hold water".   At least give an example that is comparable to real life
situations...  Parking garages are either open air, or underground
(without fenestration...)   Have you ever had a project where Mechanical
cooling needed to be provided to a parking garage?  I hope not because
these are considered transient space types.

If you are modeling your LEED buildings according to appendix G --90.1
you do not include the above grade garage wall area in your gross
building WWR calculation.

FOURTH---Deepika---you are modeling a residential home from your picture
you sent us.   YOU CANNOT USE ASHRAE STANDARD 90.1 TO MODEL LOW-RISE
RESIDENTIAL BUILDINGS!

You are using and interpreting the wrong standard, you need to use
ASHRAE Standard 90.2 for Non-commerical Residential buildings.    You
will need to use this new reference as everything you are referring to
does not apply for your project or your project model.
 
The real answer to your question is the Nebraska Cornhusker football
team IS BETTER than the Virgina Tech Hoakies!     GO BIG RED!!!!
Pasha

On Wed, Oct 19, 2011 at 3:15 PM, deepika khowal
<deepika.khowal at gmail.com> wrote:

I agree with James .

if its unconditioned space, we should not claim the window area . that
way we can have higher WWR for rest of conditioned spaces.

 

 

On Wed, Oct 19, 2011 at 1:56 PM, James Hansen <JHANSEN at ghtltd.com>
wrote:

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...

 

GHT Limited
James Hansen, P.E., LEED AP
Senior Associate
1010 N. Glebe Road, Suite 200
Arlington, VA  22201-4749
703-243-1200 (office)

703-338-5754 (cell)
703-276-1376 (fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

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
	>
	>
	>
	>

	> <image.png>
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