Save energy without replacing your windows

Posted on Dec 7, 2014


Q: When it is cold, especially at night, it feels very chilly near windows. My budget will not allow for efficient replacement windows. Are insulating window shades a good option? Can I make some myself?

A: Anytime you feel chilly, it is not only comfort being sacrificed. Your windows are losing energy, which drives up your utility bills. This is also true during summer when heat, not only the sun’s direct rays, transfers in and forces your air conditioner to run more.

What you feel near windows at night during winter is not just cold air. Your body is transmitting heat by radiation through the glass to the supercold sky. You will find it is much chillier by the window on clear nights. This phenomenon explains ground frost on above-freezing temperature nights.

Since new, low-e (low-emissivity) replacement windows will exceed your budget, window shades and low-e window film are two reasonably priced options. Always caulk and weatherstrip your windows. If there are many air leaks, any improvements you make to the glass will not be particularly effective.

Installing insulated window shades will provide the most improved comfort and energy savings year-round. Several years ago, I installed Warm Window shades with R-6 insulation value in my home office. I already had double pane, low-e windows and there still was a great comfort improvement.

When selecting insulated window shades, important factors to consider are the insulating R-value, how well they seal when closed, easy of operation, and appearance. If they are difficult to open and close or they do not look nice, you likely will not use them as often as you should.

Almost all commercially available window shades list the R-value on the packaging. They should include some type of air barrier film sewn inside the shade material to block air flow. An aluminumized or other type of low-e film is best to also help block radiant heat transfer through the material.

There should be deep vertical tracks which mount on the sides of the window opening. Deeper tracks create a longer path for air leakage to travel. Adhesive-backed vinyl tracks are effective. Also, look for brush or foam weatherstripping on the bottom edge where it rests on the windowsill when closed.

Cellular shades are a less expensive option and are good where you still want natural lighting. Double-cell types create an additional air gap for better insulation, although it’s still not as good as true insulated shades.

The most common type of do-it-yourself window shade is a Roman shade design. The key to efficiency is to make them as thick as possible, yet still fold up well and to include a reflective air barrier inside. Mylar film works well.

Q: I want to build a greenhouse for plants and to also help heat my house. I want to use a concrete floor to store solar heat, but it is unattractive. Is it possible to add color to the floor?

A: Colorants can be added to concrete before it is poured. A darker color can be more effective for solar heating. If you use ordinary powdered colorants, thoroughly mix them in to avoid a blotchy appearance.

There also are liquid colorants available for concrete. They are somewhat more expensive to use than powders, but they are easier to mix in thoroughly. Also consider stamping a decorative pattern into the surface.

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