Tuesday, January 29, 2013

Home Insulation: How much do I need?


How much do I need and how do I know if I have enough?

The most important factor in effective insulation is to create an “envelope” which includes floor, walls and ceiling areas. In order of importance; #1 the ceiling, #2 the floor and last #3 are the walls. If one of these areas is under insulated or not insulated, the effectiveness of the envelope system is breached.
 Most people overlook the floor as a critical space to insulate properly. Cold air is dense and warm air is lighter, therefore cold air comes up through the floor and pushes out the warmer air through the ceiling and out of the building.
Insulation is measured in an “R-value”. The R refers to the amount of thermal resistance in the material. The bigger the number, the more (or higher) insulative properties it has. Bigger is better here.
The amount of insulation (R-Value) depends on the climate zone of where you live. Click here to view the recommended Energy Star map of which you can then determine your climate zone. These R-values are a minimum and can always be increased as you so desire and as space allows.

What types of insulation are available?

  There are generally 4 types of insulation:

  •        Batts (fluffy blanket type)
  •       Rigid (foam boards)
  •       Blown-in
  •       Foam (expansion type)

BATTS are the most common. These are usually fiberglass batts that are rolled out like a blanket, are flexible and can be installed in all 3 building surfaces (walls, floor, and ceiling). This is also the most cost effective.

RIGID FOAM boards are dense and typically used in cases where you need a higher R-value and very little space to do it in. For example; on a vaulted ceiling you may need an R-38 and have a 2x10 rafter to work with. A fiberglass batt of R-38 will be approximately 12” thick and a 2x10 is actually 9” deep. You are now 3” short of your goal. TIP: You should never compress a fiberglass batt into a smaller space as you will reduce the R-value that it is designed for. Rigid foam is more expensive than batts and requires more labor to install. If installing between framing members, every piece must be cut individually.

BLOWN-IN insulation is on the lower end of the cost spectrum, similar to batts, and can be cost effective if installed in an open attic area in terms of labor. However, because of the nature of the application, the material can shift or compress over time and become uneven in open spaces (attics) and slide down wall cavities resulting in a reduced R-value. It is also really annoying if you have to dig through gobs of the stuff to service something in your attic and breathe the resulting dust fibers as well as being terribly itchy. For obvious reasons, it cannot be installed in raised wood floor applications.

EXPANDING FOAM is a product that must be installed/applied by a professional. It is NOT a DIY kind of project. This is a newer type of material that starts out being a liquid and when it hits the air, it expands and hardens in place. It typically has a much higher R-value per inch than most other types of insulation because of its density. It is similar to the cans of spray foam that you use to seal cracks, but applied on a much larger scale. It is the most expensive material on the market by far. However, it has advantages such as sealing the entire space (wall/ceiling/floor cavity) and no drafts or critters. Some products are approved for use in non-ventilated areas such as vaulted ceilings (or cantilevered floors) and therefor you are not required to provide a 1” air gap between insulation and roof sheathing, giving you a higher R-value in the end. Products that are “closed-cell” are minimal expanding and won’t damage your framing if over applied.

There are some disadvantages of expanding foam insulation. It is flammable and will release deadly, toxic fumes when it burns. If you read the manufacturer’s fine print, it cannot be left exposed and it must be covered with a fire rated material such as ½” cement or fire rated gypsum board. Some forms of this insulation even contain hazardous chemicals that can cause you to suffer from lung cancer or skin-related problems. Check with the vendor of the product for compliance with LEEDS and low VOC content.


  1. I always knew that it was important to insulate your home, but didn't know that walls were 3rd in importance. Great article, thanks for sharing. I'm glad I came across this because I'll need to put some insulation in my attic. Calgary gets some very cold winters.

  2. Warm House Insulation & Heating highly offer a wide range of optimum quality Insulation Materials to the valued customers.

  3. It is very useful and informative post that shares very interesting facts about Home Insulation.

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