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NZ StatutoryRTA 1986HHS 2019

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HomeGuidesHeating Calculation

HHS Pillar 1 of 5 · Regulation 6

Healthy Homes Heating Standard — NZS 4246 Schedule 2 Calculation

How to calculate the required heating capacity for a rental property living room under the Healthy Homes Standards using the Schedule 2 formula and BRANZ ALF 3.5.

Last updated 12 August 2026 11 min read MBIE-aligned

On this page

  • Definition
  • Compliance threshold
  • How to comply
  • Common failures
  • FAQ
  • Definition
  • Compliance threshold
  • How to comply
  • Common failures
  • FAQ

Definition

Healthy Homes Heating Standard The Healthy Homes Heating Standard requires every rental property's main living room to have a fixed heater capable of maintaining a minimum indoor temperature of 18°C, calculated using the Schedule 2 formula: kW = (Volume × Temperature Rise × 1.0) ÷ 1000, where Volume is the room's interior volume in cubic metres and Temperature Rise is the local BRANZ climate zone delta. ALLWISE auto-fills this calculation from address + room dimensions + ceiling height.

Compliance threshold

18°C minimum; kW per Schedule 2

Formula

kW = (Volume_m³ × ΔT_zone × 1.0) ÷ 1000

How to comply — step by step

  1. 1

    Measure the room

    Measure the main living room's length, width, and ceiling height in metres. Record exact dimensions, not estimates.

  2. 2

    Calculate the volume

    Multiply length × width × ceiling height to get Volume in cubic metres (m³). For example, a 5m × 4m room with 2.4m ceilings is 48 m³.

  3. 3

    Look up the BRANZ climate zone

    Use the property's address to look up the BRANZ climate zone (1=warm north, 6=cold south). The zone determines the Temperature Rise (ΔT).

  4. 4

    Apply the Schedule 2 formula

    kW = Volume × ΔT_zone ÷ 1000. For Zone 2 (Auckland/Wellington): ΔT = 14. Zone 3 (Christchurch/Dunedin): ΔT = 15. Zone 6 (Invercargill): ΔT = 18.

  5. 5

    Verify the heater capacity

    Confirm the installed fixed heater nameplate capacity is ≥ the calculated kW. ALLWISE auto-compares nameplate to required kW and flags shortfalls.

Common heating calculation failures

  • Heat pump sized below the Schedule 2 kW requirement
  • Portable electric heaters (not fixed — fail HHS)
  • Heater in hallway instead of main living room
  • Wrong climate zone used (e.g. Zone 2 instead of Zone 3 for Christchurch)

Frequently asked questions

What is the Healthy Homes heating temperature requirement?
The Healthy Homes Standards require the main living room to maintain 18°C. The required heater capacity (kW) is calculated using the Schedule 2 formula based on room volume and BRANZ climate zone.
Is a heat pump accepted as a fixed heater under HHS?
Yes. A heat pump installed by a qualified technician is accepted as a fixed heater, provided its nameplate heating capacity meets or exceeds the Schedule 2 calculated kW for the room.

Skip the manual calculation

Need an assessment for this standard?
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ALLWISE auto-fills the heating calculation check into every statutory pack based on the property address, room dimensions, and BRANZ climate zone. Court-defensible evidence in 11 minutes.

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Other HHS pillars covered by ALLWISE

Insulation R-valuesVentilationMoisture BarriersDraught Stopping