Exterior Insulation Upgrades

If you have to improve old siding, you might as well improve the exterior insulation too. You have a choice of methods for adding insulation underneath the new siding, which will increase your home’s overall "R/RSI" value significantly. New siding with blown-in insulation eliminates filling in access holes as well as repainting. 

Other points to note are:

• More insulation is possible via high-density stiff insulation sheets or by putting in a new wall cavity over the existing siding.
• For a poorly-insulated house made of stone or solid brick, install the vapor barrier directly on the interior under the new insulation.
• There must be some space allocated in door and window openings to allow for the extra insulation’s thickness.
• Make sure that no water runs from the roof to the gap between the walls. This can ruin the insulation as well as cause rot and structural damage. Use an eave extension or flashing to avoid this.
• Ensure that the completed insulation is sealed against outside air. This will protect against strong winds once the insulation work has been completed.

Applying Exterior Insulation

Exterior insulation can be carried out in myriad ways. Refer to your local building supply dealer for the materials required. No matter which method you choose, it is crucial to cover the whole upgrade carefully in a spun-bonded olefin air barrier (preferably Tyvek® brand) and to tape up all the joints.

Exterior insulation can easily be added with insulated siding materials, although this limits the insulation values (which may be low). Your building supplier can probably recommend better options. These can be installed in the same manner as non-insulated siding products.

Stiff board insulation can be put on top of current surfaces with suitable fasteners and adhesives. Consult your local building supplier/contractor for the best materials for your application. However, stiff board insulation needs to have all its joints tightly sealed and taped to reduce air leakage as much as possible.

It is possible to add stiff board or batt insulation to a new wall that is framed over the old siding structure. Batt insulation needs a thicker wall for the same effect.

• Place the new wall over the old siding wall.
• Perform the insulation work with total coverage at all joints and between studs.
• Use spun-bonded olefin to apply an air barrier with properly-taped seams and edges.
• Water must not drip from the roof onto the top of the new wall extension.
• Wind must not enter the wall cavity from any part of the framing plates.

Upgrading Interior Insulation

Your earlier assessment of requirements will help you determine the best method, which includes choices such as:  

• Upgrading a wall when there is damage to the existing structure, such as plaster or lath falling off.
• Putting stiff board insulation on top of an existing wall. This will require a drywall finish to complete the process.
• Design and build a new frame wall which may take up some interior space but at the same time offers quaint window boxes and increased home insulation values with a