Tempo:
to the concrete foundation walls. In this case, a vapour barrier is required to prevent vapour from entering the space between the wall finish and the concrete wall. The vapour barrier is typically sheet polyethylene.
Walls Above Grade For wood-frame residential construction, the most common vapour barrier for above-grade walls is sheet polyethylene. Vapour barrier paint on gypsum board or plaster can also be used. Spaces between floor joists at floor/wall junctions also require a vapour barrier. The most common are sheet polyethylene as shown in Figure 16 (p. 50) or rigid insulation. The vapour barrier must be tightly fitted into these spaces, but does not need to be sealed.
Roofs Sheet polyethylene is usually used as a vapour barrier in ceilings separating conditioned space from attic space.
HEAT FLOW CONTROL The National Building Code has requirements for minimum insulating values in building assemblies. The building envelope must be designed to ensure adequate performance of the insulation by preventing the decrease of the effective thermal resistance due to air leakage, convective loop heat flow, thermal bridging or moisture. The required levels of insulation are determined by the number of heating-degree days (NBC Appendix C) where the building is located.
Insulation The effectiveness of a building assembly such as a wall or ceiling in resisting the flow of heat is measured as its thermal resistance or RSI-value in metric units (R-value in imperial units). Although materials used for structure, cladding
and finishes have some resistance to the flow of heat, insulation materials are required to provide sufficient levels of thermal resistance. Insulating materials have nominal thermal resistance values determined by laboratory testing. Construction assemblies have effective thermal resistance values, which usually are lower than nominal values because they take into account thermal bridging through materials caused by framing members and fasteners that have less insulating value than the insulation material itself. Wherever one component of a building envelope meets another part and the planes of insulation do not physically join, the insulation must be overlapped for a distance of at least four times the distance separating the insulation. For example, where above-grade walls with insulation on the exterior meet a foundation wall with insulation on the interior, the insulation is separated by the thickness of the foundation wall. In this situation, interior insulation must overlap the exterior insulation by four times the thickness of the foundation wall.
Types of Insulation Insulation is manufactured from a variety of materials and in various forms. The most common types of insulation used in wood-frame housing are described below.
Batt Insulation Batt insulation is made from fibres of glass, mineral or steel-mill slag spun together with a binding agent. The product comes in lengths and widths to fit standard framing spaces and in a range of thicknesses that provide different RSI-values (R-values). Most batt insulation is called “friction fit” because it is made slightly wider than the standard framing space and held in place by friction. Batts should not be compressed to fit a smaller space because this reduces the insulation value.
Walls Above Grade For wood-frame residential construction, the most common vapour barrier for above-grade walls is sheet polyethylene. Vapour barrier paint on gypsum board or plaster can also be used. Spaces between floor joists at floor/wall junctions also require a vapour barrier. The most common are sheet polyethylene as shown in Figure 16 (p. 50) or rigid insulation. The vapour barrier must be tightly fitted into these spaces, but does not need to be sealed.
Roofs Sheet polyethylene is usually used as a vapour barrier in ceilings separating conditioned space from attic space.
HEAT FLOW CONTROL The National Building Code has requirements for minimum insulating values in building assemblies. The building envelope must be designed to ensure adequate performance of the insulation by preventing the decrease of the effective thermal resistance due to air leakage, convective loop heat flow, thermal bridging or moisture. The required levels of insulation are determined by the number of heating-degree days (NBC Appendix C) where the building is located.
Insulation The effectiveness of a building assembly such as a wall or ceiling in resisting the flow of heat is measured as its thermal resistance or RSI-value in metric units (R-value in imperial units). Although materials used for structure, cladding
and finishes have some resistance to the flow of heat, insulation materials are required to provide sufficient levels of thermal resistance. Insulating materials have nominal thermal resistance values determined by laboratory testing. Construction assemblies have effective thermal resistance values, which usually are lower than nominal values because they take into account thermal bridging through materials caused by framing members and fasteners that have less insulating value than the insulation material itself. Wherever one component of a building envelope meets another part and the planes of insulation do not physically join, the insulation must be overlapped for a distance of at least four times the distance separating the insulation. For example, where above-grade walls with insulation on the exterior meet a foundation wall with insulation on the interior, the insulation is separated by the thickness of the foundation wall. In this situation, interior insulation must overlap the exterior insulation by four times the thickness of the foundation wall.
Types of Insulation Insulation is manufactured from a variety of materials and in various forms. The most common types of insulation used in wood-frame housing are described below.
Batt Insulation Batt insulation is made from fibres of glass, mineral or steel-mill slag spun together with a binding agent. The product comes in lengths and widths to fit standard framing spaces and in a range of thicknesses that provide different RSI-values (R-values). Most batt insulation is called “friction fit” because it is made slightly wider than the standard framing space and held in place by friction. Batts should not be compressed to fit a smaller space because this reduces the insulation value.
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