Zolton Cohen: Insulated shades have drawbacks that may offset benefits

Q: Im looking into the cost and energy effectiveness of installing interior insulated window shades in my home. In the solarium, the second-floor windows face south and east, and there is an extensive overhang, so summer sun is not an issue. The windows are double-paned and filled with argon gas, and total about 200 square feet.

Since it is a second story, I would need a remote mechanical device to raise and lower the shades, which increases the price significantly. I know a tax credit or write-off is available.

We heat primarily with propane, augmented with forced air solar in the fall and spring.

After looking at the websites of a couple of manufacturers, I found it difficult to determine what type of shade would insulate the best and whether the payback over time would make the investment worthwhile. (My husband doesnt think it would.) What do you suggest?

L.S., Kalamazoo

A: Unquestionably, adding insulating shades to your solarium windows would help prevent heat loss during the winter. Because heat moves to cold, any material that retards heat flow between the warmth inside and those cold windows will slow down heat loss.

However, how much you could save is utterly unknowable. So many variables make it impossible to put any firm number on the potential reduction in propane consumption.

One thing is certain, though: The added expense of a motorized activation system would add years, if not decades, to any return on investment. You would spend a lot of money for relatively little gain. If thats the only way to control the shades on the second-story windows, you might have no other choice. But, obviously, the more you spend on the installation, the less sense it makes from a cost/benefit standpoint.

Insulated shades, as youve discovered in your research, come in many types. All are effective, some more so than others. Generally, the thicker and bulkier the shade, the more effective the thermal barrier. In that way, shades are similar to attic insulation.

If you do put shades on the windows, youll need to be cognizant of the potential for condensation to form. Adding shades would cool the glass to the point that water could condense on the pane surfaces out of any warm, humid air getting behind the shade. Then you would have to deal with puddles on the windowsill, water possibly dripping down the wall and the risk of mildew and mold forming.

Window Quilt makes a roll-up insulating shade designed to prevent condensation. The companys products are made with seals along the edges and bottom that block air from getting behind the shades. The seals also make the shade more energy-efficient. So, if youre still thinking of going forward with this project, that might be one option to explore.

If you dont install shades, consider indoor storm windows that stay in place. Permanently-affixed storms avoid the need to raise and lower shades. Plus, they seal well enough that condensation wont crop up. The insulation value likely wont be quite as high as with a good insulated shade, but theyre worth looking into.