There are three distinct ways in which windows detract from your insulation. First, heat can bleed directly through the glass via conduction. Second, windows can either raise the natural temperature by allowing solar energy into the house, or lower it by keeping it out. And third, weak seals between a window and wall can promote air flow, drawing out more heat and creating drafts.

Solid doors avoid the issue of solar energy, but of course they’re often associated with even more air flow. This is a particular problem if the door isn’t properly fitted with its jamb. Meanwhile, heat conduction doesn’t change much, although it is possible to swap out traditional wood doors for other materials like fiberglass, which have benefitted from technological advances.

All professionally-made windows are rated for their effects on the three areas of heat loss. The U-factor tells you how resistant the material itself is to conduction. Solar heat gain coefficient (SHGC) tells you how well the window transmits the sun’s energy. And air flow around a window frame is measured in cubic feet per minute per square foot (cfm/ft2).

Two of these three ratings are no-brainers when it comes to choosing the most energy-efficient option for your budget. A lower U-factor and a lower the cfm/ft2 rate mean better insulation. It’s only with the SHGC that your decision will be seriously affected by where you live and what type of household climate you prefer.

A high SHGC rating is what you want in order to warm your house faster in the winter. The window will let in more solar energy, giving your thermostat a modest boost. But a low SGHC rating will keep more of that energy out during the winter, allowing your air conditioning to cool the house down more quickly.

If you live in an area with harsh winters and mild summers, or vice versa, then the decision is made for you. Otherwise, you might have to make a tough decision about whether it’s easier to tolerate a little less heat on a cold day, or a little more on a hot day. Money might also factor into that decision, depending on how your heating costs compare to your cooling costs. 

On the other hand, with technology constantly improving, it’s possible to carefully design your household insulation in order to get the best of all worlds. Windows with variable tint can change their SHGC depending on how sunny it is, and energy efficient window attachments can compensate for times when the weather conditions aren’t ideal for your normal insulation.

When you call us for a free estimate, we can walk you through a range of different options. With a combination of window replacements, weather stripping, attachments, and everyday strategies, we can help you lower your energy consumption to levels you might never have thought possible.