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When a house has a heat recovery ventilator (HRV) and complies with minimum air-tightness requirements, the insulating values can be reduced in most cases. Refer to the NBC for insulation requirements for building assemblies when HRVs are installed. The NBC requires the building envelope to have a minimum effective thermal resistance but allows some minor penetrations such as pipes, ducts, equipment with through-the-wall venting, packaged terminal air-conditioners or heat pumps, shelf angles, anchors and ties and associated fasteners, and minor structural members, as permitted thermal bridging elements. Unheated and unventilated enclosed spaces, such as porches and garages, are not required to be insulated. Major structural penetrations through the building envelope such as floor and roof decks, balcony slabs, beams, columns and ornamentation or appendages must be taken into account in determining effective thermal resistance when the sum of their areas is greater than 2 per cent of the penetrated gross wall area. Except for a balcony or canopy, any ornament that penetrates an exterior wall or insulated roof or ceiling and breaks the continuity of the insulation must be insulated (a) on both of its sides inward or outward from the building envelope for a distance equal to 4 times the thickness of the penetrated wall insulation; and (b) to an effective thermal resistance no less than that required for the exterior wall. Mechanical ducts, chases and electrical system components such as pipes, conduits, cabinets, panels or recessed heaters located in the building envelope must have an effective thermal resistance not less than that of abutting assemblies. Expansion or construction joints, or joints between walls and doors or fenestration, must be insulated to provide thermal continuity across the joints.
Wall assemblies inclined less than 60° from horizontal are considered to be roof assemblies, and roof assemblies inclined 60° or more from horizontal are considered to be wall assemblies for the purposes of determining the effective thermal resistance. In calculating the effective thermal resistance of roof assemblies, all related structural framing must be taken into account. It is relatively easy and economical to insulate wood-frame construction by filling the spaces between the framing members with interior insulation, which usually costs less than insulation intended for exterior use. Typically, insulated wood frame walls use 38 × 140 mm (2 × 6 in.) studs with wood sheathing and batt insulation. However, in colder Canadian climate zones, additional insulation is required either in the exterior or interior side of the framing members (see Table 11 Effective thermal resistance of assemblies in buildings with a heat recovery ventilator on p. 272). Methods of insulating these different areas are explained in the following sections. The figures show a number of possible methods of insulating building elements, but there are other acceptable methods.
Basement Floors Insulation is generally not required under basement floors that do not contain heating elements. RSI-2.32 (R 13) insulation must be placed under heated floor slabs in climate zones up to 4999 HDD, and RSI-2.85 (R 17) is required in colder climates. Extruded polystyrene is commonly used under basement floors because it is resistant to damage from water and is strong enough to support most floor loads.