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Low-E 272 or 366 for PNW

HU-94684957
last month
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In Vancouver BC (zone 4C?), replacing our old double-pane clear windows with triple pane argon-filled. Most quotes I have received are for 366/clear/180 but I'm starting to suspect this is overkill for the climate. There are federal and provincial rebates going on where this combination nets you the maximum rebate, however I've also researched and found that 270/clear/clear qualifies for partial rebates. It is marginally cheaper net of rebates so cost is not the issue. The main considerations:

1. VT - we have large windows and I want to keep as much of that natural light as I can. The window estimator says there is minimal difference between 366 and 270, but it's not apples to apples as the 366 combination has another coating of 180 that would lower the VT more. I have also heard 366 has more of a greenish tinge.

2. 366/clear/180 - would my heating system have to work harder to heat my home in the winter with the reduced SHGC? I have struggled to find an equation to calculate approximate cost of heating and cooling between the two options. My understanding is that Vancouver is still a 'heating degree' climate even though it's far less cold compared to the rest of Canada. Most of the windows are east-facing.

I have central AC so the 'comfort' in the home during summer remains the same regardless - I am sure either option will drastically reduce my energy bill. It feels cold in the winter as the windows are are drafty though. Am I missing something else? Do I need another low-e coating on surface #5 or is the 270/clear/clear better?


edit to include numbers:

270/clear/clear fixed window: U-Factor 0.21, SHGC 0.27, VT 0.5

366/clear/180 fixed: U-Factor 0.17, SHGC 0.19, VT 0.44

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