Upgrading Exterior Walls

Walls have large surface areas and are responsible for a significant percentage of a house’s heat loss. Older homes constructed from solid materials like stone, log or brick usually have no insulation on the inside: there is often just a small air space between the outside covering and inner frame wall. This drainage cavity should be insulated as it can cause water leakage and condensation.

No insulation is needed for hollow concrete-block walls. The "thermal bridging" effect of the hot and cold air permeating these blocks is negligible.  It is easy to insulate traditional frame walls because accessible cavities are usually available. Determine possible obstructions to insulation such as cables or duct work using available construction techniques. These obstructions should be removed if possible, to avoid interference.

Solid stone, log or brick walls can be insulated from either outside or inside, depending on:

• Building heritage appeal. Homes with traditional solid materials are too beautiful to cover. Insulation should always be on the inside. 
• Further refinishing on the outside. This is a good reason to insulate from the outside before refinishing the exterior siding for a refurbished look.
• When the inside walls are cracking or the wallpaper is not to your liking. This is an instance to prefer interior insulation as new lath and plaster may be required for a general update. Both interior and exterior finishing may be needed. If your objective is energy efficiency, do both. That will give the home a ‘good as new’ look while being insulated inside-out. 

Factors which determine your choice of insulation include construction type, cost of materials and your skills.

Frame-Wall Cavities

Frame-wall cavities are the easiest upgrade option if they are empty. When it is already half-done from a previous insulation job, it is impossible to finish it well and is a waste of your time and money.

You can determine the amount of insulation needed in a wall by using a flashlight and checking the electrical outlets (switched off) during your assessment. For non-existent or little insulation, your contractor can recommend cellulose fiber or polyurethane foam to fill the cavity. The preferred material is then pushed through tiny holes drilled into the exterior or interior areas.  The exterior siding holes are then plugged by wood dowels. Once repainted, they give an invisible finish. To insulate brick homes with blown insulation, you’ll need to remove certain bricks, spray the insulation then replace the bricks. If interior insulation is to be performed, a hole will be drilled into the drywall or lath-and-plaster surface at various points, then filled, smoothed and repainted after insulation is complete. 

If interior insulation is preferred but the interior drywall or lathwork is bad, holes need to be drilled into the existing surface before covering them with a complete vapor and air barrier. You can even add a new drywall on top of the current surface – this is cheaper than a fully-framed interior wall and takes up negligible space.