[Greenbuilding] windows - flush vs recessed

[John Salmen]

I think it makes sense that having gone through the process of modelling a
window (therm) you follow through with observing the placement. It is true
that the gains are marginal but if such gains are continually discounted in
a building process - they accumulate. I've modelled other instertices like
sill plate fnd wall with rigid insulation and found minor improvements with
offsetting plates onto insulation, etc. Are these important? Depends how
much rests in the details.

It would not be high on my priority list if the design has not afforded high
performance windows and other basic upgrades.

I have always felt that anecdotally recessing a window is important for
shielding or breaking wind - It would be nice to see some studies on that.

-----Original Message-----
From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of John
O'Brien
Sent: January-30-12 7:49 AM
To: jfstraube at gmail.com; Green Building
Subject: Re: [Greenbuilding] windows - flush vs recessed

On Mon, Jan 30, 2012 at 8:47 AM, John Straube <jfstraube at gmail.com> wrote:
> Hiya George. Of course I know it is per unit length, as I quoted the 
> units of W/mK So if I have a 5' by 4' window (1.5 x 1.2m) the 
> additional heat loss of 0.01 W/mK is 0.054 W/mK or in 0 F weather, 2 
> Watts. Lets say we allow us 0.03 W/mK difference between the ideal 
> location and the location preferred by the owner, or builder, or the 
> window durability.  Now we are up to 6 Watts/window. In a house with 
> 12 windows, this is 72 Watts, at DESIGN CONDITIONS for Zone 5, and we 
> have 2000 W flowing through the windows themselves.  The prescence of 
> absence of overhangs and neighboring buildings will likely have this 
> much ipact on heat loss.
> The real reason to worry about this stuff are the examples of when it 
> is done horribly, and you have a 0.2 W/mK (which works out to 
> 41W/window or 500W for 12 windows at design) detail and you start to 
> risk condensation on the window edge.
>

http://passivehouse.us/passiveHouse/2010_Passive_House_Conference_Presentati
ons,_November_5_files/2010%20Conference-Windows%20Roundtable-Bronwyn%20Barry
.pdf

Where most of the 'window should be in the middle' has been coming from.
Anyone want to take a stab at her numbers?

She claims "By moving the windows to the center of the wall the Annual Heat
Demand was reduced by 22%."

Seems somewhat not insignificant.

J

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