Insulation: hidden key to comfort and savings

Brett Freeman | Improvement Center Columnist | July 29, 2013

Not having sufficient insulation for your home is like going out in the winter without your puffer coat. When you leave your winter coat home, you can run in place or do jumping jacks to increase your body's metabolism and keep warm. But your home doesn't jump around and burn calories; if your house isn't adequately insulated, the furnace just burns up your money.

The fact is that heating and cooling costs account for at least half of your home's energy use. Adding insulation can reduce that expense by as much as 30 percent, according to the U.S. Green Building Council (USGBC.) If your house is poorly insulated or lacks insulation altogether, you might save even more. So, it certainly is worth wondering -- and finding out -- whether your house is insulated appropriately.

Why do I need insulation?

On a hot day, go up into your attic for an instant reality check. Attic temperatures can go as high as 150 degrees in summer despite the soffits and ridge vents that are designed to create air flow. This is because there is not enough insulation in most homes' attics, so heat is readily conducted from the roof into the attic.

Now go downstairs, get a step stool and put your hand on the ceiling beneath the attic. A mere 10 inches above your hand it's hotter than Death Valley in August. But while the ceiling may feel warm if your roof insulation is less than adequate, it gives you barely any indication of just how hot it is upstairs.

How much is enough?

Determining whether you have enough insulation is a multi-step process. The Environmental Protection Agency table on its Energy Star website shows recommended levels of insulation in different climate zones. It's a good place to start. The next step is to see how your insulation measures up to Energy Star's recommendations.

"If someone calls and says, 'Hey, my house is getting hot,' or 'Hey, my house is getting cold,' we send someone out to check the subfloor and check the attic," says Jim Warner, owner of Jim Warner Insulation in Reno, Nev.

Can you see the floor joists in the attic? These are the 2-by-8 beams sitting on their sides. If so, you need more insulation. Having adequate attic insulation is vital -- in summer it's all that prevents the sun from turning your attic into an oven. And in winter, remember that heat rises. It can rise right through the ceiling into the attic leaving the rest of the house in need of heat and making your furnace work overtime.

The good news is that in addition to being the easiest part of the house to check for insulation, the attic is also the easiest place to add insulation. The simple fix? Have loose-fill insulation blown in on top of existing insulation.

"As a general rule, the attic needs to have 12 inches of insulation," Warner said. "That's my rule of thumb in any climate zone."

If you have a crawlspace or unheated basement, make sure there is insulation between the floor joists. If there isn't, installing batt insulation is typically a relatively easy and inexpensive DIY project. In crawl spaces, be sure to use batt insulation with no facing on either side because even properly ventilated crawl spaces can have a lot of moisture. If you use insulation with facing, the material can trap moisture between it and the subfloor, which can lead to mold or fungal damage.

Should I get an energy audit?

A full-blown energy audit can help you determine how your house loses energy, particularly from air loss. This process involves a blower door test, which requires specialized equipment. Energy auditors use the blower door to seal one of the doors in your house and blow air inside. This allows them to use infrared thermometers to identify places where air is leaking out of your house. Consider having this test done if you live in an older house or it's drafty in the winter.

The audit also includes an evaluation of insulation levels and whether your attic has adequate ventilation. "Ventilation is a must, it has to be addressed," Warner says. "An under-ventilated attic can be as bad energy-wise as an under-insulated attic."

What about the walls?

Checking or improving insulation in exterior walls is a more difficult proposition because the insulation is behind plaster or drywall. That can make it difficult, as well as expensive, to upgrade. But particularly if you live in an older house, it's worth investigating.

"If it's an older house and your walls are plaster, chances are there's no insulation," Warner says. "If it's 20 or 30 years old, you probably need more [insulation]."

Checking to see if you have insulation behind your walls is as simple as drilling a hole. If you do need more, loose-fill insulation can be blown in:

  1. Cut holes between wall studs roughly every 16 inches -- either from inside through the walls, or outside through the siding.
  2. Blow in the insulation. However, from outside it's more expensive and siding patches are tough to hide.
  3. Patch the holes. Indoor repairs to plaster or drywall, unlike siding patches, can be virtually invisible if done well.

If your house is more than 20 years old and has loose-fill insulation that has compacted or is not performing well, new blown-in insulation is also an option for you. The method is the same as for homes with no insulation, but before the new insulation is blown in, the existing insulation must be vacuumed out.

So, does your home have enough insulation? It's worth taking five minutes to at least check your attic, but as Warner pointed out, most older houses are under-insulated, and houses over 40 years old may have no insulation at all. If you do need more, he says adding insulation is relatively inexpensive -- $.75 to $1.00 per square foot, and in many cases it's an easy fix that can have a dramatic impact on your energy costs.

About the Author

Brett Freeman is a freelance journalist. He also owns a landscaping and irrigation company in North Carolina. Previously he has worked as a beat reporter, a teacher, and for a home improvement company, and he used to own a bar/live music venue.