Funny the timing on this news brief: I had just taken down our two fixed awnings a couple of days after this post. Took about a half an hour; we take them down in the fall just when we start seeking the solar gain they have been blocking and before any snow load will stress them.
And taking these fixed awnings down is exactly what the DOE-2 model used for this analysis struggles with. While DOE2 works with great finesse on optimizing window performance for exterior attachments like roller screens and retractable awnings, it can’t really handle fixed ones well at all.
That is how you end up with screwy results that show a net energy loss for fixed awning in colder climates. Turns out that EnergyPlus is a better modeling “engine” for most window attachments, and something on which we are working hard in the Lawrence Berkeley National Lab’s DOE project on window attachments. Within the next several months, we will have a qualitative window attachment selection tool to guide users as they compare the performance benefits of about 15 – 20 different attachment options. And then within the next 18 months or so, we will have a quantitative “engine” (using EnergyPlus) woven in to the selection tool so that all window attachment options can be fairly compared.
And by the way, we only have our awnings on the west side of our house—that is where all the solar gain comes here in Brattleboro on our lot. And since we have installed our four awnings (two fixed on the first floor, and two retractable on the 2nd floor), we have pretty much eliminated ANY active air conditioning in our home. Something else that models won’t pick up—eliminating active cooling!
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