NECB 2015 Question

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Good morning,

This is a question for my follow Canadians that have experience with the
NECB 2015 code.

What is everyone's take on what fenestration area to model for the
reference model when the Proposed model area is less than the maximum

Specifically, I'm referring to Part which states "If the total
vertical fenestration and door area to gross wall area (FDWR) of the
proposed building differs from the maximum permitted by Article,
the FDWR of the reference building shall be adjusted proportionally along
each orientation until it complies with that Article."

Do people interpret this as if my Proposed FDWR is say 20%, then my
Reference FDWR is to be increased to say 40% (based on a Zone 5 climate)?


Chris Hadlock's picture
Joined: 2012-01-23
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That's my interpretation, although I know of at least one local code
(Ontario's SB-10) that has modified this:

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On Thu, Mar 14, 2019 at 9:46 AM Chris Hadlock via Equest-users <

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Kyle Anders's picture
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bfountain's picture
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Good morning,

That would be my interpretation too. It differs if it is more or less than
the maximum permitted and should be adjusted for the reference as maximum
permitted.This approach is different than with ASHRAE 90.1 and gives a
significant advantage to projects with less windows than usual (which is a
good thing). Same approach is taken with Energuide ratings : HOT2000
software adjust the ratio of reference building as soon as the proposed
building is outside the minimum and maximum ranges : 17% - 22%.

This interpretation would also be confirmed by the LEED V4 Canadian ACP (
that states that projects can use the NECB reference at some conditions,
including :

*Apply fenestration area convention similar to ASHRAE 90.1-2010 *
Maintain the same FWR (as defined by NECB, including doors) for the
Reference as exists in the Proposed Design, up to the prescribed maximum.
If the Proposed Design?s FWR exceeds the prescribed FWR, scale down the
fenestrations in the Reference case accordingly.

However, NECB is quite unclear on this topic and it could be good to have
an official guidance :)

Benjamin Zizi
Coordonnateur technique

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Le jeu. 14 mars 2019 ? 09:58, Kyle Anders via Equest-users <
equest-users at> a ?crit :

Benjamin Zizi2's picture
Joined: 2019-03-25
Reputation: 0

Thanks you to all the respondents. I've had 3 consistent responses that in
fact the Reference window area is to be set to the maximum allowable in all
cases (for the NECB code), which I'll take as general (modeler's) agreement.


On Thu, Mar 14, 2019 at 10:47 AM Benjamin Zizi

Chris Hadlock's picture
Joined: 2012-01-23
Reputation: 0

Hi Chris,

I agree as well, that?s how we?ve been interpreting it. Basically in Calgary climate zone 7A if the proposed design has a 20% FDWR then the reference building can be set to 33%. And there?s also an allowable skylight area (I think it?s 5% or less?) which can be applied to the reference building as well.

Menush Akbari BEng, PEng, BEMP, CMVP
Associate Principal, Energy
c 250 777 3380

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Calgary | Nelson
Member of Integral Group

Menush's picture
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