We have had our first hard frost. We are now officially starting to heat our homes. We have already traversed 6 percent of the heating season.

We know that because the Bangor Daily News tracks degree-days on the weather page. A degree-day is the measure that people in the heating industry and energy characters like Dick Hill and me use to track how cold the weather really is. We have many years of historical data available to compare the current season to and decide whether we are too hot, too cold or just right.

This year, we are right on track. Degree-days are calculated by measuring the high temperature for the day and averaging it with the low temperature for the day. That number is then subtracted from 65 degrees. The result is the number of degree-days for that particular day.

A temperature of 65 degrees is assumed to be warm enough that we do not need to heat our homes. If the outside temperature is above 65, your heat should not come on if this theory is correct.

In reality, that number could be lower, 60 or even 55 degrees, since our homes are — in theory — well-insulated and stay warmer because of all that insulation. We also run more electrical devices than we did when we started collecting degree-day data.

All those electronic gadgets we run in the average home add a fair bit of heat to the house. Electrical devices take the energy that they use, do their thing — whether it is lighting a room or running a TV — and ultimately convert it to heat. That heat is useful in winter and has to be removed from the house during the warmer months.

We are, in a sense, blessed by a cooler climate in that we get to use much of this electrical wastefulness to keep our homes warm.

Of course, since we are living in properly insulated houses, one area that we can still attack is the window. The most common, better windows are insulated to about R-3, while the average wall is probably hitting around R-20.

We find many newer homes with astounding amounts of glass. I confess to this sin, since there are a lot of nice things to look at from my house. We like to introduce natural light into our homes at all times of the year. We pay a big thermal price for that.

The average well-insulated house has more heat lost from windows than from any other part, except if there is a big hole in a wall or roof. Sadly, that does show up in some homes.

Newer windows are showing up on the market with higher insulation values. They can be as high as R-6 by introducing additional layers of glazing, usually plastic, between the glass outer layers. Such windows were introduced about 20 years ago but have had mixed success. The plastic inner layers yellowed and broke down when exposed to long-term sun-light. I anticipate that newer glazing methods will last longer. Buyers, check your warranties.

A simple way to approach the big heat-loss issues with windows is to use an insulated window covering. This does not necessarily mean some ugly, klunky covering that you don’t want to look at.

You can start with a simple plastic window shade. By drawing the shade to the windowsill at night, you can cut that window’s heat loss by 10 percent. No big investment, nothing weird-looking — just this simple practice. And it is free, if you already have shades. You also can use insulating shades, honeycomb shades, pop-in foam panels and foam-insulated shutters.

Each of these items is a larger investment, but insulating windows at nighttime yields a tremendous benefit, especially if you have a lot of windows and you draw the shades at night. And you can almost laugh at the number of degree-days.

Questions for Tom Gocze should be mailed to The Home Page, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. A library of reference material and a home-project blog are at bangordailynews.com/thehomepage.