ACT 7.1.4 External Glazing - Application of Part 3.12.2
Subject to (b), in applying Part 3.12.2 to an addition or extension all glazing on the respective storey, including the addition or extension and any existing glazing in the unaltered part of the storey, must be assessed where Part 3.12.2 indicates the whole storey must be assessed. However, the Total System U-Value of an existing glazing unit in the unaltered part of the building can take account of any of the following:
Window treatments listed in Table ACT 22.214.171.124, to the extent provided in that table, where the glazing unit incorporates the respective treatment in compliance with the notes to that table.
Window shutters mentioned in Annex G of international standard ISO 10077-1, (Thermal performance of windows, doors and shutters — Calculation of thermal transmittance), where the glazing unit is readily closed in by the shutters, and the shutters can be readily opened so they do not shade the glazing of the unit, and the closed shutters comply with the respective construction, material and permeability provisions of that Annex G.
The Total System U-Value of the existing glazing unit, incorporating shutters, can be calculated by adding the inverse of the respective shutters’ value of additional thermal resistance, ΔR, from Table G.1 (Additional thermal resistance for windows with closed shutters), of the above-mentioned Annex G.
If an addition or alteration fails to incorporate a wall that can contain translucent glazing with an area of at least 1 m2 or 1% of the addition’s or alteration’s floor area, whichever is the greater, not overshadowed by a building in winter, and orientated within the north sector shown in Figure 126.96.36.199, then all glazing (existing or otherwise) in the storey need not comply with the requirements of 188.8.131.52 that relate to aggregate conductance of the glazing if—
the addition or alteration has a total floor area not exceeding 50 m2; and
compliance with the requirements of 184.108.40.206 that relate to aggregate conductance of the glazing would not result in a building (or part thereof), as extended or altered, having its energy efficiency reduced below—
the relevant statutory minimum, which is the minimum energy efficiency requirement, if any, that all or part of the building, respectively, was required to achieve when constructed or altered; or
for a building that has not been altered or extended, the current energy efficiency of the building, which is the lesser of its energy efficiency determined using the factors Part 3.12 covers, or the energy efficiency it would be required to achieve under Part 3.12 if it was to be built; or
the aggregate conductance of the glazing is in accordance with BCA requirements that applied in the ACT immediately before or anytime after the adoption of BCA 2010 in the ACT; and
bulk thermal insulation has been added to the roof of the unaltered part of the building, in accordance with the requirements of 220.127.116.11 that apply to roofs with an upper surface solar absorptance value of not more than 0.4.
The Building (General) Regulation 2008, section 29 (Unaltered parts need not comply with building code—alternative energy efficiency requirements for external glazing Act, s 29 (2) (b)) prescribes when windows with solar control film or when "isolated glazing" need not comply with the BCA, Part 3.12.2, in relation to a substantial alteration mentioned in the Building Act 2004, section 29 (Approval requirements). Those alternative energy efficiency provisions may apply to existing windows that ACT 7 applies to whether or not the window is in respect of a "substantial alteration" as defined in the Building (General) Regulation 2008, section 23 (Substantial alteration—Act 29 (2) (a)). However, the storey's area mentioned in 18.104.22.168(b) must exclude the enclosed area, ΔA, that the isolated glazing unit is located in. Isolated units must be in an area enclosed by walls and doors (a "zone"), and all glazing units in the zone must be treated as isolated units. ΔA is the zone's area, and must be counted only once for a particular zone, even if the zone has more than one isolated unit. If the ABCB's glazing calculator is used to demonstrate compliance, isolated unit details need not be entered (they may be disregarded), and if so, the entry for the storey's area must be reduced by the sum of each ΔA value for each zone. The ΔA reduction does not apply to glazing units disregarded because of the solar control film, because they lack zone requirements.
Figure ACT 7.1.4
|Diagram a.||Addition incorporating a wall within the north sector|
|Note: Plan showing a method of compliance with certain requirements of ACT 7.1.4(a) and (b), in assessing window energy efficiency as part of a deemed-to-satisfy alternative to using house energy efficiency rating software.|
Figure ACT 7.1.4
|Diagram b.||Addition incorporating a wall within the north sector|
|Note: Plan showing a method of compliance with certain requirements of ACT 7.1.4(c), in assessing window energy efficiency as part of a deemed-to-satisfy alternative to using house energy efficiency rating software, where the ABCB’s 2009 glazing calculator may be used rather than the current calculator, as a concession.|
Table ACT 22.214.171.124 Glazing unit U-Values
|Glazing unit (not taking account of any window treatments)||Improved U-Values with window treatments|
|U-Value||R-value||Holland blinds only||Closed weave curtains only||Heavy drapes only||Closed weave curtains & pelmet||Heavydrapes & pelmet|