[Equest-users] URGENT: Window U-values: Total window assembly v/s Glass only

Omar Katanani omar at ecoconsulting.net
Fri Jul 29 06:55:28 PDT 2011


Thanks Bruce,

 

I have an additional question:

 

*       In the "Glass prop.jpg" file attached, I entered the glass
conductance as 0.6 Btu/h-ft2-F

*       In the "Window specs.jpg" file, I entered the frame width as
zero.

*       However, when I look at my LV-D report, I notice that the
Average U-value for the windows is 0.509 Btu/h-ft2-F

 

Why is this number different from the glass conductance, given that I am
assuming the frame width zero (i.e, the window is only composed of
glass)?

 

I need to figure this out in order to argue with the LEED Reviewer that
eQUEST has the ability to capture frame effects.

 

Many thanks,

Omar

___________________________ 

Omar Katanani
Sustainable Design Engineer

Email: omar at ecoconsulting.net

 

EcoConsulting (Lebanon)

Nahas Building, 4th floor

4 St-Maron Street / Georges Haddad Avenue

Postal Code: 2028 5806 SAIFI

Beirut, Lebanon

Tel:          +961 (0) 1 971 266
Mobile:    +961 (0) 3 045 045

 

EcoConsulting (UK) Ltd
28 Marshalsea Road
London, SE1 1HF
Tel:  +44 (0) 207 939 0989
Fax:  +44 (0) 207 939 0981

Website: www.ecoconsulting.net <http://www.ecoconsulting.net/> 

 

  

________________________________

From: Bruce Easterbrook [mailto:bruce5 at bellnet.ca] 
Sent: 28 July 2011 19:36
To: Omar Katanani
Subject: Re: [Equest-users] URGENT: Window U-values: Total window
assembly v/s Glass only

 

I would try showing the frame effects are accounted for.  I checked my
ASHRAE Fundamentals text and the SHGC numbers seem close for 6mm glass
double glazed with an aluminum frame in Table A8.2.  This is a
complicated area and I don't get this deep into it.  This also seems to
be a LEED US wrinkle from the question.  The reference to referencing
A8.2 would only apply to the base case anyway not to your proposed
glass.  So it would seem to me you show eQuest does account for the
frames, which it does and that your proposed glass values are reasonable
or you look at NFRC and pick a manufacturer making a window close to
what you are proposing.  I think the biggest problem is the reviewer is
not very experienced and is just giving you a stock reply.
Bruce

On 28/07/2011 11:01 AM, Omar Katanani wrote: 

Hi Bruce,

 

The project is in Lebanon, and there are pretty much no standards
relating to energy whatsoever!

 

The LEED Review I got is the following:

 

"It is It is unclear whether the window U-value of 0.26 and SHGC of 0.28
used for the Proposed case accounts for the impact of the window frames
on the whole assembly as required by ASHRAE modeling protocol. Please
provide additional information to confirm that the framed assembly
U-value was used for the Proposed case windows (e.g. showing that the
whole window assembly has been tested by NFRC, or verifying that LBNL
Window5 calculations have been provided for the whole assembly, or
verifying that the frame effects are captured within the energy modeling
software), or revise the model referencing ASHRAE 90.1-2007 Table A8.2
if needed."

 

Can we argue that the frame effects are captured within eQUEST, as per
the underlined phrase?

 

Do you recommend using table A8.2, or are its U-values too high?

 

Best regards,

Omar

___________________________ 

Omar Katanani
Sustainable Design Engineer

Email: omar at ecoconsulting.net

 

EcoConsulting (Lebanon)

Nahas Building, 4th floor

4 St-Maron Street / Georges Haddad Avenue

Postal Code: 2028 5806 SAIFI

Beirut, Lebanon

Tel:          +961 (0) 1 971 266
Mobile:    +961 (0) 3 045 045

 

EcoConsulting (UK) Ltd
28 Marshalsea Road
London, SE1 1HF
Tel:  +44 (0) 207 939 0989
Fax:  +44 (0) 207 939 0981

Website: www.ecoconsulting.net <http://www.ecoconsulting.net/> 

 

 

________________________________

From: Bruce Easterbrook [mailto:bruce5 at bellnet.ca] 
Sent: 28 July 2011 17:36
To: Omar Katanani
Cc: Robby Oylear; Brad Robinson; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] URGENT: Window U-values: Total window
assembly v/s Glass only

 

Hi Omar,
    This is where LEED and eQuest can get complicated.  As you are
outside the US the NFRC test results won't apply to you.  This is a US
window test standard.  Being from Canada we have CSA test requirements
for windows, we don't use NFRC.  Basically you need to use the base
standard for your country for your baseline.  LEED Canada has adjusted
the LEED documents in this area to reflect our testing agency and what
we consider a base window.  Has the country you are building in done the
same?
    So to get you going I would assume a base window in eQuest for the
baseline.  Use 6mm clear glass, 1/2" air space, 6mm glass, metal spacer.
Also pick a base frame as well, this would depend on the type of
building you are doing, so select a plain frame in common use, if metal
choose a frame without a thermal break.  This should be easy to defend
on a LEED review.  If there is a specific country version of LEED for
your location then you could adjust for this later once you get the
required information.  For your proposed you would build the window you
are considering using the window manufacturers specs.  All manufacturers
will not offer all glass types.  In the window industry there are the
glass manufacturers, they make the glass.  Window manufacturers buy the
glass and make the frames.  Now you can see the reasoning behind the
NFRC testing and testing the total window, glass and frame, it is window
manufacturer specific.  But it does make a conflict with eQuest and the
way it was programmed and the way windows are input.  Realistically the
frame it not going to make much difference except if it is metal and
there is a thermal break.  The glass being the overwhelming area of the
window is going to have the largest impact.  This is what you want to be
playing with in eQuest, determining the cost effectiveness of different
types of glass and the payouts.  As long as you operate from a realistic
baseline which is the current standard construction used in the country
of the build then you can evaluate your proposed glass because you are
looking at differential costs and savings.  If your baseline changes it
won't make very much difference, you have already been able to select
your window, it will just effect the payback period and it will be a
minor difference.  This does let you get 98% of the window work done.
Bruce Easterbrook P.Eng.
Abode Engineering

On 28/07/2011 08:40 AM, Omar Katanani wrote: 

Dear all,

 

Thank you for your responses.

 

1.	Are the NFRC testing and the values in table A8.2 used for the
Baseline, Proposed, or both scenarios?

 

2.	Let's say I do not have NFRC test results and decide to use the
values in table A8.2. For a clear double glazed and metal frame type, I
get an assembly U-factor of 5.1. How can I input this into eQUEST? As
far as I know, I can enter the glass properties and the frame
properties. Do I have to play with the glass properties and check the
LV-D report for the calculated Assembly u-value?

Similarly, for the baseline, Tables 5.5-1 to 5.5-8 of ASHRAE 90.1
provide the assembly u-values for vertical glazing. How can I enter
these values into eQUEST?

 

3.	I am attaching the specs of the proposed glazing. These numbers
are for the glass only (note that the u-values reported are NFRC ones).
Additionally, I know that the frame will be aluminium. Do I still need
NFRC U-values for the whole assembly, or is the NFRC usually for the
glass only? If yes, how can I calculate the whole assembly U-value
(given that eQUEST doesn't have the ability to calculate this)

 

Thanks for clarifying this, as my project is outside the US and we are
not too familiar with standards such as NFRC.

 

Best regards,

Omar

___________________________ 

Omar Katanani
Sustainable Design Engineer

Email: omar at ecoconsulting.net

 

EcoConsulting (Lebanon)

Nahas Building, 4th floor

4 St-Maron Street / Georges Haddad Avenue

Postal Code: 2028 5806 SAIFI

Beirut, Lebanon

Tel:          +961 (0) 1 971 266
Mobile:    +961 (0) 3 045 045

 

EcoConsulting (UK) Ltd
28 Marshalsea Road
London, SE1 1HF
Tel:  +44 (0) 207 939 0989
Fax:  +44 (0) 207 939 0981

Website: www.ecoconsulting.net <http://www.ecoconsulting.net/> 

 

 

________________________________

From: Robby Oylear [mailto:robbyoylear at gmail.com] 
Sent: 28 July 2011 00:53
To: Omar Katanani
Cc: Brad Robinson; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] URGENT: Window U-values: Total window
assembly v/s Glass only

 

Omar,

 

To directly answer your question:

 

"I'm assuming that, given that I entered the u-values for the glass
only, and then I entered information about the frame, then I need not
worry about any conversions in U-values, since eQUEST has all the
necessary information to calculate the equivalent u-value of the whole
pane + frame assembly,right?"

 

No.  Your method will result in an assembly U-value based on your input
glass conductance and whatever default frame properties that the eQUEST
wizard will use.  I have never tried to let eQUEST determine an assembly
value, as NFRC values are required for LEED and code compliance studies.
I would not be surprised if the values eQUEST is calculating (shown in
LV-D and LV-E reports like previously mentioned) are much different than
what you'll actually see in the test results.

 

Again, NFRC values are a LEED requirement, so unless you're just doing
preliminary analysis for a client, you need to receive NFRC simulation
reports or certified product directory numbers in accordance with NFRC
100.

 

Robby Oylear, LEED(r) AP BD+C

Mechanical Project Engineer

Energy Analyst

 

D 206-788-4571 | C 206-354-2721

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

 

 

 

On Wed, Jul 27, 2011 at 2:44 PM, <omar at ecoconsulting.net> wrote:

Dear Robby,

Yes, I am modeling for LEED purposes.
I'll look into A8.2. But at least, is my method correct for the proposed
scenario?

Brad: I think you need to enter the center of glass u-value in the
"Glass Type", and then enter the frame properties in the "Window"
properties...

Best,
Omar



Quoting Brad Robinson <brad.robinson at yahoo.com>:

	
	
	Is the u-value listed for a manufacturer and specific model on
the NRCAN website centre of glass or overall assembly?  Many windows are
custom made to suit so I am unclear if each individual custom window
would need to be tested.
	
	
	
	In eQuest, when entering the window, if the u-value represents
the whole window, including frame, do you need to enter a frame width,
conductance etc as well under the Window Frame section under Window
Properties?  Thanks.
	
	
	Brad Robinson
	
	
	
	________________________________
	From: Robby Oylear <robbyoylear at gmail.com>
	To: Omar Katanani <omar at ecoconsulting.net>
	Cc: equest-users at lists.onebuilding.org
	Sent: Wednesday, July 27, 2011 12:32:08 PM
	Subject: Re: [Equest-users] URGENT: Window U-values: Total
window assembly v/s Glass only
	
	
	Omar,
	
	The answer depends on the purpose of your study.  If you're
trying to get results for a client on the impact of the glazing on their
energy performance, this may be adequate.  Make sure you've entered in
the framing information properly (metal vs. non-metal).
	
	I'd recommend opening up your simulation output results file
(xxxx.SIM) and going to the either the last page of the LV-D report or
sort through your LV-E report to see what value eQUEST has calculated.
Compare these values to the ASHRAE Fundamentals results for overall
assembly values including frame to see how close you've come.  I would
not blindly trust that eQUEST will give you an appropriate overall
assembly value based on entering only the center of glass number.
	
	However, if this is for a LEED study, this is not adequate.
This an excerpt from an e-mail I sent out recently regarding LEED and
NFRC requirements.
	
	In order to meet LEED EAp2 Minimum Energy Performance, the
project must comply with all mandatory provisions of ASHRAE 90.1-2007.
Section 5.4.2 Fenestration and Doors requires that fenestration
performance be determined per section 5.8.2.  Section 5.8.2.4 U-factor
requires that the U-factor for the overall fenestration area (including
framing) be determined in accordance with NFRC 100. If you do not have
NFRC data available, values from section A8.2 are the only acceptable
alternative.
	
	Robby Oylear, LEED(r)AP BD+C
	Mechanical Project Engineer
	Energy Analyst
	 

	D206-788-4571 |C206-354-2721

	
	www.rushingco.com
	
	
	
	
	
	On Wed, Jul 27, 2011 at 8:14 AM, Omar Katanani <
omar at ecoconsulting.net> wrote:
	
	Dear all,

	 
	I have a small question regarding entering

	window properties to eQUEST:

	 
	I have read a lot of emails in the forum

	discussing NFRC testing, LBNL Window 5 import, and other topics
that I haven?t
	paid attention to before.

	 
	The way I modelled my windows is the

	following:

		 
		       1. I have manufacturer?s specifications listing
the glass U-values, not the total assembly.
		       2. In the ?Glass Types? (eQUEST Detailed Mode), I
created glass types, and entered the glass conductance, visible
transmittance, SC, and emissivity from the manufacturer?s details I
have.
		       3. When creating windows, I specify which glass
type (from the ones I created in step 2), in addition to the frame width
and conductance.

		
		 
		I?m assuming that, given that I

	entered the u-values for the glass only, and then I entered
information about
	the frame, then I need not worry about any conversions in
U-values, since
	eQUEST has all the necessary information to calculate the
equivalent u-value of
	the whole pane + frame assembly, right?

	 
	I appreciate your feedback / comments

	today if possible, as this has become really urgent!

		 
		Many thanks,
		Omar
		___________________________
		Omar Katanani
		Sustainable Design Engineer
		Email: omar at ecoconsulting.net
		 
		EcoConsulting (Lebanon)

		NahasBuilding, 4th floor

		
		4 St-Maron Street/ Georges Haddad Avenue
		Postal Code: 2028 5806

	SAIFI

	Beirut, Lebanon
	Tel:          +961 (0) 1 971 266
<tel:%2B961%20%280%29%201%20971%20266> 
	Mobile:    +961 (0) 3 045 045
<tel:%2B961%20%280%29%203%20045%20045> 
	 
	EcoConsulting (UK) Ltd
	28 Marshalsea Road
	London, SE1 1HF
	Tel:  +44 (0) 207 939 0989
<tel:%2B44%20%280%29%20207%20939%200989> 
	Fax:  +44 (0) 207 939 0981
<tel:%2B44%20%280%29%20207%20939%200981> 
	Website: www.ecoconsulting.net
	 
	 
	 
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