Window Shades That Help Buildings Stay Cool Naturally
Why Solar Shades and Cellular Shades are Among the Most Effective Window Treatments for Passive Cooling
In this weekly Q&A column, retired builder/building inspector Cam Allen answers readers’ home renovation questions. Have a question? Enter it in the form below.
It is no secret that we are going to see another El Nino this year with temperatures projected to reach previously unheard of record highs. Most predictions say it will begin to affect our weather in North America dramatically by early summer and continue well into the fall of 2026.
The summer sun’s rays produce approximately 230 BTU per square foot of glazier surface. This means a large single-pane window facing south with an opening five feet high and six feet wide allows nearly 7000 BTU of heat into your home. When you compare the fact a small free standing gas fireplace can emit 18–20,000 BTU it’s not hard to see how a house full of windows can produce so much heat. This of course translates into the necessary cooling capacity to counter-balance this much heat or solar gain, which it is known
as.
To generate this increased cooling capacity, the demand for air conditioning is increasing rapidly. Today it’s the number one HVAC installation cost for any home being renovated. It is also becoming one of the largest electrical operating costs in the home.
Solar and Cellular Shades
Shading windows from heat and cold goes back to the Ming dynasty. The Chinese developed a roll up system with bamboo that is still used in a similar fashion today.
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Today, we suggest you investigate both solar shades and cellular shades. There is a distinct difference in these products.
Solar Shades
These type of shades create a still air space between your room and the glass. They are effective both in summer and winter.
Some years ago I had the pleasure of working with a company in Ottawa called Krumpers Solar Blinds. They produced one of the most effective solar shades I have seen. They project savings of upwards of 40 percent of your energy bills, while allowing a clear unobstructed view, as their website states. They are also deeply involved in reducing the carbon footprint of their manufacturing.
Cellular Shades
The other, not quite so pricey, option are cellular shades (also known as honeycomb shades). They are very effective, especially if you move up from single cell to double or triple cell. Single cell shades are a slim cellular design that traps air in the cellular pockets, providing a small amount of
insulation. They are available in light filtering material along with room darkening or blackout fabrics allowing varied levels of light control and privacy. Blackout cellular shades work well for bedrooms or windows facing a major street.
The type I have seen most often are double cell shades. They are manufactured with twin cells that greatly improve the rigidity and the long-term durability of the shades.
Single cell shades struggle to get an insulation rating much over R1 to 1.5 whereas double cell shades commonly exceed R3. If you consider stepping up to the triple cellular shades it can reach on average (depending on the fabric) from R4 to R5.
Cellular shades also offer a small amount of noise reduction and they add a clean low-profile look to your windows when they are drawn up.
As a home DIY project these are not difficult to install. That said, taking your time to get them measured to fit snugly and allow them to operate smoothly is the first step once you have decided on the type, fabric, light density and number of cells in your individual shade. Once you have done your homework, measure “twice” in at least 4 spaced widths inside your window opening. You will be surprised by the differences you may find in width. Excess window frame foam when the window was installed often “warps” the frame so you will have to find a common width that will allow the cellular shade to operate smoothly. Once you have received your order, follow the manufacturer’s instructions to the letter. Some offer YouTube videos for you to watch before starting your installs.
Lastly, if you have older thermal pane sliders and the budget will just not stretch for new ones, cellular shades are a viable option. They will significantly reduce your heating and cooling bills at a fraction of the cost. If you have existing drapes, don’t ignore the energy value of shades. Coupled together they will allow natural light if you have the proper fabric in your cellular shades. During the heat of the day or at night in the winter, close both for added savings.
Images from Depositphotos
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