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National Building Code 2010 The amount of fenestration and section 9.36

Myrtbnye

Registered User
Joined
Sep 24, 2020
Messages
1
Location
New Brunswick
I am working on the design of a house and the architect wants a large room (living, dining and kitchen about 900sqft). She wants the walls to have a window and door to wall ratio of about 60%. How will this affect the effective thermal resistance of the walls?
 

cda

Sawhorse 123
Joined
Oct 19, 2009
Messages
18,861
Location
Basement
Welcome

Buy good glazing?

Give it a day or two for answers

The architect does not have the answer??
 

tmurray

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Joined
Jun 10, 2011
Messages
1,903
Location
NB, Canada
I'm assuming the building is a Part 9 building.

In regards to 9.36, there is no impact that you need to worry about in regards to the effective thermal resistance of the walls. There are some limited situations where it would, like for manufactured homes, but otherwise the windows just need to meet the U value or ER rating and the remainder of the wall just needs to meet the R value for above grade walls. The code in general assumes a window to wall ratio of %22, but that is for an entire cardinal direction, but there is no restriction on this on most buildings.

Now, outside of the code, how will this affect the overall thermal resistance of this building face? Severely. The required effective R value of a wall is 17.5. For windows and doors it is about 3.5. A mechanical engineer once told me a rule of thumb was if the windows and doors make up %10 of the wall, they will account for %50 of the heat loss through that assembly.
 
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