For many years, your options for attic insulation have been limited; either blown in loose fill (fiberglass or cellulose) or  fiberglass-based batt insulation.   These types are usually installed on the attic floor.  There is nothing wrong with these products.  However, if your goal is to maximize your energy savings, it is important that the installer seals air leaks around windows, ducts, wires, pipes, attic stairwell covers, and gaps between the attic floor and the floor below.   The goal is to prevent warm air from the house from rising into the attic in the winter, where it will tend to heat the attic and the interior side of the roof.  The heating of the interior side of the roof is what causes ice dams to form.   One problem with adding floor insulation to your attic is that it takes up lots of floor space, and may leave you with little or no storage space.  Also, it is difficult to seal all the sources of heat escaping from the floor below.

There is a newer process that is safe and very effective in keeping your roof cold, which will do a great job in preventing ice dams.  This process is called Spray Foam Insulation.   It is not as common as the older types, primarily because it hasn’t been around that long and the cost is higher.  However, a google search for Spray Foam Insulation will produce a number of contractors in your area who specialize in this process.  The material used is called Icynene.   This is becoming very popular for insulating the entire house in new construction.

The idea of spray foam insulation is that instead of insulating the attic floor, we apply the insulation to the attic ceiling and end gables, completely sealing the attic space.   The product is applied with a spray gun, expands to around 100 times its liquid volume in seconds, and is extremely effecting in sealing all gaps and cracks.   It will generally do a much better job at insulating your attic because the product is applied directly to the place where it is needed – the attic ceiling.  All soffit vents and attic ridge vents are sealed, and there is generally no need to vent the attic in the summer or use an attic fan.  A spray foam insulated attic will be comfortable all year round.  It will be slightly cooler than the floor below in the winter, and slightly warmer in the summer, but not that much.  In short, the attic becomes a “conditioned” space of the house that is just as comfortable as any other room in the home.   And you lose no storage space because there is nothing applied to the floor.  Any HVAC units in the attic (like central air conditioning units) will probably run more efficiently in the summer since they will now be installed in a relatively cool environment.

The product, after applied, looks like fluffy foam, similar to what you see used in some packaging material.   It will be semi-rigid after it sets up (about an hour), and it can be anywhere from 6 to 20 inches in thickness, depending on what type you use and how much you want to spend.  One drawback is that you will need to clear everything out of your attic before it is applied, but the good part is that you can put it all back and use all your attic floor space for storage afterwards.

The two main types are called open cell and closed cell insulation.  The open cell insulation is cheaper, has a lower R-value, and may require a thicker application.  The closed cell requires less material but is significantly more expensive.   It will also tend to offer more moisture resistance, but this is not important for an attic application.   You will probably find that the cost of open cell spray foam insulation is around two or three times the cost of the older style floor insulation,  but the spray foam insulation should do a much better job at insulating your attic, and should greatly lower the probability  of problems with ice dams, because the interior of your attic roof will be very cold.  Over time, the cost should be recovered in energy savings both to heat and cool your home.   The attic will stay relatively warm in the winter and cool in the summer.

Craig Forman is a Green Newton board member. This post was previously published in the January/February 2017 edition of GN’s Green News.