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Shade Cloths for Windows
Last updated 2014.02.22
What is a Shade Cloth?
It's like sun-block for the most sensitive part of your house – the sun-facing windows. The objective is to stop the majority of the energy embodied in direct sunlight (insolation) in order to reduce the solar heat gain through your windows. The result is less heat being produced in your house, when you don't want it. If you live in a hot southern area, shade cloth could save you hundreds of dollars on your energy bill.
There are several techniques that can accomplish this. You can plant trees to block the sun from your windows, but these tend to be ineffective near mid-day (the hottest part of the day), because you don't want trees so close to the building. You can apply solar-blocking films to the outside of your windows, however, these are permanent, which means you also lose the benefit of solar gain during cold weather when you want it. You can use shutters, but these tend to block your view through the window completely, and required going outside to open them and close them when desired. You can install awnings, however, these tend not to be effective against morning and late afternoon and early evening sun, and many people do not care for the aesthetics, or are not permitted to use them on street-facing windows due to covenants or municipal ordinances. You can retro-fit deeper eaves under your roof to provide the desired shading in summer, but this is likely to be expensive and very intrusive during the renovation period. After considering these options, and others, we came up with custom-fitted shade cloths for our windows to reduce summer solar gain.
The fitted shade cloth has the following advantages.
Sliding window from inside, with shade
cloth fitted to both panes (339 KB)
Our window shade cloth is essentially a piece of fabric rated for outdoor use, in a colour selected for acceptable aesthetics. It is light in colour to reduce the heat conversion effect associated with darker colours.
While there are a number of possible means for attaching the cloth to the window, we have settled on the following method. We insert a rare-earth permanent magnet into the seams of the cloth at each corner. For larger windows, we install additional magnets along the top seam. Then, we use clear silicon seal to "glue" coated, steel (magnetic) washers to the windows in the appropriate locations. The magnets in the seams of the cloth then attach to the steel washers. This holds the cloth in place in all but high winds. Even in high winds (over 80 km/hr gusts), at least one bottom magnet remains attached, so we have never lost a cloth (yet).
That should provide enough information for you to make your own. We recommend washing by hand, and hanging to dry. The magnets make machine washing and drying impractical.
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