The Code Tools - H1 Calculator is a web-based tool for assessing the thermal efficiency of buildings and verifying compliance with New Zealand Building Code clause H1. For compliance purposes, this calculator can be used to assess housing and other buildings with an area of occupied space no greater than 300 m2.
The thermal property values of all building materials are set in accordance with NZS4214 tables E1 (a-c).
Buildings with thicker cladding can still be assessed with this calculator, however, the benefits of the extra thermal resistance will not be reflected in the results, indicating better performance than calculated.
Construction R-values of walls and roofs are calculated in accordance with NZS4214, and the isothermal planes method is used to account for thermal bridging. Roofing, roof underlay, and wall underlay are omitted for simplicity and because these elements have a negligible effect on thermal performance.
Surface resistance values are set as follows, and in accordance with NZS4214 Para 5.2
Areas of building elements that are not part of the thermal envelope must not be included in your calculation.
The construction R-value of the slab is in accordance from H1/AS1, Appendix F, Tables F1.2.2A-X. Area and Perimeter values must be measured on the interior side of all walls that delineate the extent of the thermal envelope.
Trusses are assumed to have timber frames. Truss spacing is assumed to be at 900mm centers. Truss chords are assumed to have a width of 90mm.
Truss roofs are presumed to consist of a plasterboard layer, a timber framing and insulation layer, and an insulation layer.
The still air space in a truss roof is deemed to have an R-value of 0.11 (non-reflective) in accordance with NZS4214 Table E2.
'Layer 1' is the bottom layer of insulation and is positioned between the truss chords.
'Layer 2' is the top layer of insulation and is positioned on top of layer 1 and the truss chords.
Rafter roofs are presumed to consist of a plasterboard layer, and a timber framing and insulation layer.
The R-value of typical joinery types is as per with H1/AS1 table E1.1.1.
All cladding is assumed to be installed over a ventilated cavity, consequently, the thermal resistance of all cladding is de-rated by 50% in accordance with NZS4214.
External walls are presumed to consist of a plasterboard layer, a timber framing and insulation layer, a ventilated cavity layer, and an external cladding layer.
Internal walls are presumed to consist of a plasterboard layer, a timber framing and insulation layer, and a plasterboard layer.
Direct fix claddings and rigid air barriers are not supported by this calculator. Buildings with these features can still be assessed with this calculator, however, the thermal benefits of these features will not be reflected in the results, indicating better performance than calculated.
The heat loss of the reference building is calculated in accordance with H1/AS1 table 2.1.3.4a.
The heat loss of the proposed building is calculated in accordance with H1/AS1 paragraph 2.1.3.6.