News Brief

Fixed Awnings' Heating Penalties Can Overshadow Savings

By Erin WeaverFixed awnings in cool climates can create a net increase in energy spending, while retractable devices are more likely to increase energy savings, according to a new study.

In conjunction with the Professional Awning Manufacturers Association and screen manufacturer Phifer Incorporated, California firm White Box Technologies modeled the energy performance of various awnings and exterior roller shades in 50 locations across the U.S. In cities like Miami, with the longest cooling seasons, fixed awnings reduced solar gain and yielded cooling energy savings, but those savings decreased in cooler climates. Even when used only during the cooling season, fixed awnings in northern cities like Boston can block the sun’s heat when it’s needed and result in heating penalties of up to $60 a year at standard fuel prices—canceling out money saved on electricity for cooling.

In all but the hottest climates, retractable or removable awnings are preferable, the researchers conclude. Modeling for exterior roller shades exhibited similar trends, but with average savings of about 25% less than that of awnings.

Published October 2, 2012

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Comments

October 23, 2012 - 5:34 am

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!