[Equest-users] Modifying existing historic windows

[Nicholas Caton via Equest-users]

The “assembly 0.67” for a single layer of glass leaves me a little uncertain – I think if you dig deeper you might find the manufacturer may have some helpful context around that figure.  Do they suggest the net impact of the low-e glass, associated framing, trapped air layer, and conductive transfer of the seals in contact with the existing assembly nets an effective U-0.67 for a given/standard window size?  If so, your math looks pretty okay for the assumptions stated (just expand on what that 0.67 means in documenting your approach)!  If not or if this isn’t made very clear, you may need to perform a more involved analysis to account for one or more of those items.

For savings accuracy with existing/historical window retrofits (not always a priority with LEED certification, understandably), I might also be interested (resources permitting) to test a mockup installation before & after to explore the impact on infiltration reduction in your model.  That may more fully capture the cost:benefit ratio if the value of the measure is under active consideration.

~Nick

[cid:image001.png at 01D327FA.71FB7AD0]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

D  913.564.6361
M  785.410.3317
F  913.564.6380
E  nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

[cid:image002.png at 01D327FA.71FB7AD0]



From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Morteza Kasmai via Equest-users
Sent: Thursday, September 07, 2017 4:44 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Modifying existing historic windows


Dear all,

I am modeling a historic building and the scope of work is to modify the existing windows by adding a storm window to the existing industrial steel sash windows. The storm window is one layer Low-E glass with aluminum framing with brake (assembly U-0.67).
Assuming the existing one layer clear glass window has U-value of 5.8, can I assume the assembly R-value of the window system as the total R-values of both of the windows as following, and would it be acceptable by the LEED reviewer?
Total R-Value: 1/5.8 + 1/0.67 = 0.172 + 1.49 = 1.662
U-Value = 1/1.662 = 0.6
I would appreciate your help in this matter,
Morteza


[https://lh6.googleusercontent.com/Uuukta80GuFfvKouzA0mdSvUXqml7MtSwSiw-evuGMU=w147-h43-p-no]


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