Energy retrofits will add layers of insulation, air tight and vapour retardant materials to control the flow of heat, air and moisture in the building. These additions will also affect other materials and assemblies throughout.

Most of the materials that are used in energy retrofits are conventional and commonly used already by contractors and renovators - the ordering, handling and installation of these materials may not require much in the way of learning. In some cases, however, there may be materials that will require contractors to use a slower, more careful approach, or that are new to the construction industry and require training to fully understand their application.

There may also be built assemblies that will need clear detailing so that layers are placed and sequenced properly. There may be framing details, for example, where walls meet roof structures that need special attention to ensure continuity of control layers while maintaining good drainage of water on the exterior.

WHAT ARE ASSEMBLIES?

When a house is being built, construction workers will put various materials together to create ASSEMBLIES - structural elements, control layers, windows and doors, electrical / plumbing / mechanical systems, and finish layers.

The combination of these layers in foundations, floors, walls and roof systems will be measured for performance in the following ways:

• Structural integrity - The arrangement of materials in horizontal, vertical and angled planes work together to make a building strong and resilient. Engineers design assemblies for our building codes that are rated for shear strength, compressive strength or ability to resist a bending or twisting force.
  
• Effective thermal value - When materials are layered from interior to exterior, they combine their capacities for resisting (or conducting) the flow of heat energy. This "effective" thermal performance is measure in R-Value or U-Value to determine how well or how poorly an assembly acts as an insulator.
  
• Surface area heat loss - The flat surfaces of wall, floor and roof assemblies in a building will conduct heat energy from warm to cold. Heat loss through surface areas is very important to control in cold climates like Canada. The rate of heat loss can be slowed with insulation and airtightness layers
• Air leakage losses - Cracks, holes and poorly sealed openings may create air leaks that carry heat energy and moisture in the air flow. This may lead to condensation and/or trapped moisture in assemblies, which could develop into mold or materials degrading. Air leaks may also force heating and cooling equipment to work harder, which could shorten the useful life of this equipment. Creating an airtight building envelope is very important.
• Ease of use - Window and door units are assembled and installed in a building so that they will open and close properly, lock tightly and seal against the weather. They will also integrate with air, moisture and thermal control layers - this integration helps to support the overall energy efficiency of a building.
  
• Operational efficiency - Heating, cooling and ventilation appliances are rated for efficiency by how well they convert input energy sources - electricity, natural gas, etc.. - into usable energy output. These systems will have connections and/or circulation systems, like ductwork or radiators, that are part of their overall efficiency.
  
• Thermal bridge heat loss - When heat energy can conduct through solid building materials from the warm side to the cold side of an assembly, this is called a thermal bridge. Common thermal bridges are clusters of framing materials, metal components, brick and concrete. As building envelopes add more insulation and air tightness strategies, the effect of thermal bridges are amplified. This type of loss may be prevented by 'breaking' the bridge, usually by applying some type of continuous insulation material toward the exterior.