V2.6.2.2 Method

V2.6.2.2 Intent

The intent of any Verification Method is to demonstrate that a Performance Solution meets the appropriate Performance Requirement(s). It is an optional approach to demonstrate compliance with the NCC Performance Requirements for energy efficiency.

A Performance Solution can provide flexibility where the prescriptive DTS Provisions are considered too rigid or inappropriate in assessing certain building designs. An Assessment Method, such as a Verification Method, can also be argued to allow for innovation and effective use of the building’s fabric to make the building more energy efficient.

Verification Method V2.6.2.2 is a comparative Verification Method as it assesses the heating load and/or cooling load of the proposed building design and compares it to the heating load and/or cooling load of a reference building.

The reference building characteristics are those of a building modelled using specific minimum DTS Provision clauses of NCC Volume Two Parts 3.12.1 to 3.12.4. In using the elemental DTS Provisions as the basis for the reference building, the thermal performance of the proposed building fabric may not be decreased below the minimum required by the DTS Provisions.

Verification Method V2.6.2.2 only applies to Class 1 and enclosed Class 10a buildings attached to a Class 1 building. It does not apply to detached garages or to open carports and is limited to the Performance Requirement P2.6.1.

V2.6.2.2 Methodology

The basic approach is that the annual heating load and/or cooling load (typically measured in MJ/m2/annum) of the proposed building design must not be more than the annual heating load and/or cooling load target of a complying theoretical reference building using the DTS Provisions.

This establishes the theoretical annual heating load and/or cooling load that would have been generated by that building design had it been built to comply with the DTS Provisions. This sets a quantified target (benchmark) that must be achieved when modelling the Performance Solution.

This approach requires two modelling runs with software (other than house energy rating software); the first is to set the heating load and/or cooling load targets (i.e. using the reference building described above), and the second is to demonstrate that the proposed building design can achieve this minimum target. Both modelling runs must use the same calculation method to maintain consistency.

The Verification Method V2.6.2.2 can facilitate certain “trade-offs” between different elements of the building fabric, such as reducing insulation in the walls whilst increasing the insulation in the roof or improving the thermal performance of the glazing.

V2.6.2.2 Compliance Requirements

The NCC climate zone determines whether the annual heating load and/or cooling load are necessary for determining compliance because the annual energy load of the proposed building must be equal to or less than the energy load of the reference building.

(a) Compliance with P2.6.1 is verified when a proposed building:

(i) Compared to a reference building, using a calculation method other than house energy rating software has:

In addition to the above heating load and/or cooling load requirements, the following must also be met:

(A) for building fabric thermal insulation, 3.12.1.1;

(B) for thermal break, 3.12.1.2(c) and 3.12.1.4(d);

(C) for compensating for a loss of ceiling insulation, 3.12.1.2(e);

(D) for floor edge insulation, 3.12.1.5(c) and 3.12.1.5(d);

(E) for building sealing, Part 3.12.3 or V2.6.2.3.

The Verification Method V2.6.2.2 additional requirements may not be part of the Verification Method V2.6.2.2 modelling process.

V2.6.2.2 The Reference Building

Several parameters must be used when calculating the heating load and cooling load of a reference building.

Where a Reference Building has not been followed, as per the above, it does not meet the Verification Method V2.6.2.2 and becomes an 'Other Verification Methods' under  the A2.2  Performance Solution. In this case, the appropriate authority must review and accept compliance with the Performance Requirement P2.6.1.

V2.6.2.2 The Reference and Proposed Design

Several parameters must be the same in both the reference building and the proposed building design. This is to avoid using energy efficiency criteria or calculations that could result in a more generous target for the reference building and then criteria or calculations that result in lower annual heating load and/or cooling load values for the proposed building.

(i) calculation method; and

(ii) location-specific data, including that of climate and topography appropriate to the location where the proposed building is to be constructed if the data is available or the nearest location with similar climatic conditions in the same climate zone for which the data is available;

(iii) impact of adjoining structures and features;

(iv) soil conditions;

(v) orientation;

(vi) floor plan, including the location and size of glazing;

(vii) number of storeys;

(viii) roof cladding and roof lights;

(ix) separating walls;

(x) external non-glazed doors;

(xi) intermediate floors;

(xii) floor coverings;

(xiii) internal heat gains from equipment and appliances;

(xiv) air infiltration and ventilation;

(xv) function and use of the building and spaces, including zoning, hours of occupation, hours of heating and cooling availability;

(xvi) space temperature settings within the ranges of 20°C to 21°C for heating and 25°C to 28°C for cooling;

(xvii) the profiles for occupancy and air-conditioning.

V2.6.2.2 Calculation Method

The calculation method used must comply with ANSI/ASHRAE Standard 140 and be capable of assessing the heating load and cooling load by modelling:

(i) the building fabric;

(ii) glazing and shading;

(iii) air infiltration and ventilation;

(iv) the function and use of the building, including zoning, hours of occupation, hours of heating and cooling availability and internal heat gains;

(v) relevant built-environment and topographical features;

(vi) the sensible heat component of the cooling load and heating load.

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