Above Grade Walls

This section discusses:

• The necessary performance functions of an exterior wall
• Why air tight construction is necessary
• Thermal bridging in wood frame construction
• Typical exteriors wall construction types:
  
  • 2x6 wood frame
  • 2x6 with exterior rigid insulation
  • 2x4 with exterior rigid insulation
  • double wall construction
  • insulated concrete forms
  • rigid insulating core panel walls

Performance functions of an exterior wall

In addition to supporting the structural loads of the house, exterior walls must also:

• resist the infiltration of wind from the exterior
• resist the outward flow of warm moist interior air
• resist heat flow in both directions

Cold winter winds entering or passing through an insulated wall cavity will reduce the effectiveness of the insulation, cause uncomfortable interior drafts and uneven room temperatures and unnecessarily increase the money you have to pay in heating bills.

Internal house pressures (caused by mechanical systems such as exhaust fans and furnaces or the outside winds) can force warm, moisture laden interior air into the exterior wall cavities to condense and potentially cause mold and rot conditions.

When Manitoba's winter temperatures reach 30 below and we try to keep the interior air in our homes at plus 70, the exterior walls of our homes see a 100 degree temperature difference between inside and out. Without a properly selected, designed and installed wall system, excessive heat energy will flow outwards and be lost in the winter while higher internal heat gains in summer will cost you more in air conditioning costs.

A properly constructed wall ensures that all components of the wall system work together to produce a durable, structurally sound system that is optimally resistant to heat and air flows.