Straight Talk Articles
Things are Looking Up: Three Steps to an Efficient Attic
Dear Pat and Brad:
I’m convinced we could reduce our high heating bills if we add more insulation to the attic. How do I make sure everything’s done right? - Kelly
It’s great that you’re focused on your attic, as this is often the area you can get the most bang for the buck on your efficiency investments.(1) But insulation is just one part of an energy-efficient attic.
STEP 1: SEALING
Attics are often the place where warm air leaks out of the house in winter or into the house in summer. Trouble spots include anything that comes through the attic floor, such as recessed lights, the chimney, the attic hatch and pipes, ducts or wires coming through the attic floor.
It’s easiest to seal properly before adding or improving the insulation. For more details on air sealing, see our August 2020 article or the Energytips website noted at the end of this article.
STEP 2: VENTILATION
Many attics are under-ventilated, which allows moisture and heat to build up. Moisture causes harmful mold and wood rot. In summer, a poorly ventilated attic is prone to overheating, which can bake shingles and shorten their life. In winter, a warm attic can melt snow on the roof, causing it to run into your gutters and then freeze, causing ice dams.
Good attic ventilation lets air flow from a low point to a high point. This is usually done by installing soffit vents and insulation baffles around the perimeter, plus vents near the peak of the roof. If there is no way to install enough attic ventilators, an attic fan can be installed to provide a mechanical assist to exhausting overheated air.
STEP 3: INSULATION:
The three main types of insulation for attics are loose-fill, batt, and rigid. Whichever type you have, it needs to provide a high-enough level of insulation for your region, measured in R-value.
Batt and rigid insulation will often have the R-value printed on them. Loose-fill, which is blown in, is the most common for attic floors, and its R-value is approximately its depth in inches multiplied by 2.8.(2) In general, your attic should have 14-24 inches of loose-fill if you live in a Northern State and 11-14 inches if you’re in a Southern State.(3) You can find the recommended level for your region at www.energy.gov/energysaver/weatherize/insulation
If you have loose-fill that is less than the recommended amount, you should be able to add more on top of it, as long as there aren’t any moisture problems or rodent, ant or termite infestations. If your existing loose-fill insulation was installed before 1990 it could be Vermiculite, which may be contaminated with Asbestos,(4) which can cause cancer when particles are released into the air. It’s good to have the insulation tested. If it’s contaminated, have it removed by a professional before beginning work.
Remember to seal and insulate any walls in the attic that border conditioned space, such as skylight openings.
Some of these steps are challenging, and are best done by a contractor. If you decide to do your own work in the attic, be aware of numerous hazards. Disturbing old wiring can cause shorts in your electrical system. Roofing nails will often pierce the attic ceiling.
Another danger is stepping off the rafters. Years ago, I (Pat) decided to do some work in my attic on a hot afternoon. The heat must have gotten to me because I slipped and crashed through the attic floor. My daughters were surprised to see their dad’s legs dangling from the ceiling, with broken sheetrock and insulation everywhere.
We hope this brief information helps you take the next steps to a more energy-efficient attic.
This column was co-written by Pat Keegan and Brad Thiessen of Collaborative Efficiency. For more information on a more energy-efficient attic, go to the December 2020 More Information Page.
(2) fixing basement moisture problems is a major topic all its own, with a variety of approaches.
(4) For more info, see our August 2020 article on Sealing Air Leaks.
Skylights can be a beautiful feature on a home, but are often a source of heat loss. Photo Credit: Darien and Neil, Flickr.com