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.
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