Insulation. How much does your house have?

Insulation Basics

The purpose of insulation is to slow the rate of heat transfer.  Insulation does not stop heat from moving out of your home in the winter or into your home in the summer.  Insulation traps air pockets within itself and it is this that insulates.  We measure insulation value with the concept of thermal resistance or R value. The higher the R value the greater the thermal resistance.

All building materials have insulating value:  plaster, drywall, vapour barrier, wood sheathing or boards and siding.  These just don’t trap as much air as fibre-glass insulation.  For example, a 2 x 4 exterior wall with wood sheathing, vapour barrier and drywall may have a R value of 2 – 3.  So if you add fibre-glass batts with a value of R 12, your total wall insulation is actually at R 14 or 15.

The following shows the different R values of materials we use to insulate.   We base the R value on approximate R-value per inch.

Ideally insulation should have most of the following characteristics:

  • High R value
  • Inexpensive
  • Durable (lasts the life of the home)
  • Completely fills cavities
  • Stops air leaks
  • Stops vapour diffusion
  • Moisture and rot resistant (because all houses leak eventually)
  • Non-combustible
  • Chemically inert

No insulation available today meets all of these points.

What do you have in your home?

While most of the insulation in your home is not visible without some demolition, wall insulation for example.  You can know what is in your attic.  The two highest points of heat loss are walls and attic.  The following is a list of building codes and practices regarding insulation. This is broken down by year so you can get an idea of what your home was built with.

  • 1950 and earlier:  R 7 attic and 0 in walls
  • 1950 – 1960: R 8 attic and R 7 walls
  • 1960 – 1974: R 10 attic and R 8 walls
  • 1974 – 1980: R 12 attic and R 10 walls
  • 1981 – 1982: R 20 attic and R 12 walls
  • 1983 – 1989: R 28, 32 attic and R 12 walls
  • 1990: R 38 attic and R 21.8 walls
  • 1993: R 38 + attic and R 22 walls

As a result of a number of factors including higher fuel costs and greater focus on efficiency, homeowners have gone to great lengths to increase the insulation values.  Here is an example of a home I inspected recently that was built in 1916.  Firstly, wow!  What a beautiful home!  Secondly there were many insulation updates to this wood frame 2 storey Colonial Revival home.

  • Insulation was added to the attic.  There was no obvious sign that there was original insulation from construction.  Cellulose (loose fill) was blown in (about 10 inches deep with an R value of  32).
  • While there was evidence of some shredded paper insulation in some exposed interior wall sections, it is unlikely that the balloon frame exterior walls had much or any.  What may have been there would have likely fell to the main floor section.  A type of synthetic stucco was applied over the exterior walls on top of approximately 2 inches of polystyrene boards (adding about R 8).  With the existing wall members (2 x 4 studs and 1 inch pine boards) the total R value is likely up to as much as R 12.

There are a number of ways to add insulation and some are better then others.  Ideally the added insulation does not compact the existing and does not stop air flow in the attic venting space.

Air barriers, vapour barriers and air flow are very important when we talk about insulation.  Part two of this blog will focus on these.









Posted by Jeremy Scratch

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