This article is a sequel to Part 1: Insulating Foundations - Slab-on-Grade, and discusses the role and placement of insulation in the basement wall itself. The insulation can be placed in 2 distinct locations, each having its own advantages and disadvantages. These locations are discussed below.
Insulation on the Outside Face of the Wall Which Touches the Surrounding Earth
It is believed that this method is ideal for achieving a dry basement. The insulation, usually of rigid fibreglass, is placed over a damp-proofing coating or material and extends from the footing to just below the finished grade level. A perimeter drainage system consisting of gravel and perforated pipes is also recommended.
The advantages of this system are:
- reduction of heat loss
- the minimization of thermal bridging
- better protection against moisture entry through capillary action
- protection against the freeze-thaw cycles
- reduction in the possibility of condensation on the basement surfaces
The disadvantages are:
- It is not usually practical for existing buildings
- Exterior insulation may be subject to attack by insects
- Your contractor may not be aware of all the details required for this type of construction
Insulation on the Inside of the Basement Wall; Insulation on the Outside Face
This insulation can be placed easily and is sometimes placed in basements from grade level to the frost line.
The advantages of this system are:
- A suitable solution for existing buildings
- Offers a wide choice of insulation types, as it is on the inner face of the wall
- The threat of insect attack in minimal
- Isolation from the cooler earth is better, especially during the winter months
The disadvantages are:
- Fire-protecting the insulation may be necessary
- Perimeter drainage is required to avoid the insulation from absorbing the moisture in the walls. Interior space may get reduced a bit
- Good construction detailing for air sealing, etc. is required
In Part 3, which will follow, the discussion will focus on new and innovative methods for insulating foundations.
Go To Page: 1 2
