How well insulated is your home?

Having the right insulation is important to keep the heat in, in the winter and out in the summer. It helps us feel comfortable and keeps our heating, ventilation, and air conditioning systems in economy mode.

Home renovations, sloppy installation, old low standards - any number of factors can affect the effectiveness of your insulation. Since most insulation is in the ceilings, floors, and walls, any problems with it are often out of sight, out of mind. After all, it's hard to feel comfortable during temperature extremes and your electricity bills are high. Knowing a little more about the principles of insulation will help you decide if it's time to make a change.

Traditional glass wool insulation creates a thermal barrier. In this way, it keeps the heat inside (winter) or outside the building (summer). The purpose is to impede the movement of heat.

Insulation is not an air barrier. Air can still pass through the glass wool, and air contains heat. Therefore, the more air that passes through your insulation, the more heat the insulation blocks. When that air is significantly hotter than the air on the other side of the insulation—such as indoor air in the winter or outside air in the summer—it's harder for your insulation to keep heat in or out.

Here's one way to think about it. Let's say you're insulating a small shed. There is a large hole on one side that leads out. Instead of nailing a board over the hole, you just put glass wool. Done, right? Well, not quite.

Every time you run a heater in the shed, it seems like it will never turn off and reach the desired temperature. The reason is that the warm air created by the heater quickly escapes through the hole in the wall - it hardly matters that the insulation is there.

What is the lesson? To optimize the effectiveness of the thermal barrier (insulation), you must also optimize your air barrier. This is creating hermeticity (airtightness) of the building structure: the missing link between insulation and comfort.

This is creating hermeticity (airtightness) of the building structure: the missing link between insulation and comfort. Warm air moves from the bottom of the structure up to the top.

In the context of insulation, this means that you should prioritize insulation in the ceilings and in the floor (insulated bypass space). Next, you need to pay attention to the walls. If most homes already meet these requirements, which they do, where is the problem?

Enter an air seal. Most homes have insulation in the ceiling and walls. However, they rarely contain barriers that stop warm air from entering through gaps and cracks around ducts, plumbing, wires and cables, bathroom fans, ceiling fans, ceiling hoods, electrical outlets, vents.

They may look like small gaps and cracks. Individually, they are. Cumulatively, however, they can equal leaving a window open all year, this is known as an "air leak". Preventing it is the key to improving comfort, reducing your electricity bills, and getting the most out of your insulation.

Older houses are usually poorly insulated and lack air sealing. You need to fix this. Pre-2000 homes aren't necessarily "old." A two-story home built in 1980 isn't that old when you compare it to a 1960s brick house or a 1920s bungalow. As mentioned, housing construction over the years has almost never prioritized building hermetic closure.