Should I Use the H1 Schedule, Calculation, or Modelling Method for My Project?
NZBC H1 gives designers three ways to demonstrate energy efficiency compliance: the Schedule Method, the Calculation Method, and the Modelling Method. Most projects default to schedule because it's what designers know. Some use modelling when they didn't need to. Many miss the Calculation Method entirely — which often sits in exactly the right spot between the two.
Choosing the right pathway at the start of a project is a design decision with real consequences. Get it wrong and you're either paying for analysis you didn't need, or constrained by a compliance pathway that doesn't fit your design. Here's how to choose.
The three H1 methods are testing different things. Schedule asks: does each element meet the minimum? Calculation asks: does the building's calculated heat loss stay within budget? Modelling asks: does the whole building use no more energy than a reference building built to schedule minimums? They suit different projects — and the best choice depends on your design, not your habit.
The Three Pathways: What They Actually Do
Schedule Method
H1/AS1- Prescriptive: each element must meet minimum R-values for its climate zone
- Glazing area capped as a percentage of floor area
- No trade-offs between elements
- Fast and straightforward — no specialist software
- Does not reward performance above the minimum
- Fails if glazing exceeds the schedule limit
Calculation Method
H1/AS2- Calculates the building's total heat loss and compares it to a reference budget
- Trade-offs allowed: more glazing can be offset by better insulation, or vice versa
- No dynamic simulation — uses steady-state calculation
- More flexible than schedule without the complexity of full modelling
- Can be completed with a structured spreadsheet or dedicated tool
- Good fit for designs that are close to — but exceed — schedule limits
Modelling Method
H1/AS3- Comparative: proposed building energy use vs. a reference building built to schedule minimums
- Full dynamic simulation accounting for climate, orientation, solar gain, thermal mass
- Most flexible — can accommodate any design if the energy balance works
- Requires specialist energy modelling software and a qualified modeller
- Highest upfront cost and lead time
- Essential for high-glazing, complex, or high-performance designs
When to Use the Schedule Method
Schedule is the right call when the design sits comfortably within its constraints — which is more common than designers assume. Use it when:
- Glazing is within the schedule limits for the climate zone. If the window and door schedule comes in under the cap and there's no design pressure to exceed it, schedule is efficient and sufficient.
- The building is a standard form with no unusual geometry, construction type, or thermal mass strategy. The schedule doesn't reward these things, but it doesn't penalise them either.
- The brief is minimum compliance, nothing more. There's no value in paying for calculation or modelling to confirm what the schedule table already tells you.
- Time is tight. Schedule compliance can be confirmed quickly. The other methods introduce lead times and dependencies on specialist availability.
When to Use the Calculation Method
The Calculation Method is the most underused of the three — partly because designers jump from schedule straight to modelling when the schedule doesn't work, without considering whether the calculation method would solve the problem more economically.
It's the right choice when:
- Glazing modestly exceeds the schedule limit and you want to offset it with better insulation in walls, roof, or floor. The calculation method handles this kind of straightforward trade-off without the cost of full modelling.
- One or two elements are below the schedule minimum and you want to demonstrate that performance elsewhere compensates. Again, this is exactly what the calculation method is designed for.
- The design is broadly standard but with a specific deviation from schedule that needs a documented justification rather than a full energy model.
- Budget doesn't support full modelling but the design genuinely can't comply with schedule as drawn.
Use BEO's free online calculator to work through the H1 Calculation Method for your project — enter your element specifications, glazing areas, and climate zone to check compliance and explore trade-offs.
When to Use the Modelling Method
The modelling method becomes necessary — or strategically valuable — in a specific set of circumstances where the other two methods can't get you there:
The glazing significantly exceeds schedule limits
Contemporary NZ residential architecture frequently features glazing areas well beyond what either schedule or calculation can accommodate through simple trade-offs. A glazed gable end, full-height sliding doors across a north elevation, or a highly glazed commercial façade requires modelling to demonstrate that the overall energy balance still works — typically by accounting for passive solar gain, shading devices, thermal mass, and high-performance glazing specifications together.
The design has strong passive solar characteristics
Both the schedule and calculation methods ignore orientation. A north-facing glazed wall delivering substantial passive solar gain in winter is treated identically to the same glazing facing south. The modelling method accounts for solar access, shading, and thermal mass — and can demonstrate that a well-oriented high-glazing design genuinely outperforms a schedule-compliant building. This is one of the few cases where modelling can actually reduce the insulation requirement relative to schedule.
The project is also targeting Passive House or Green Star
If the project is running a Passive House or Green Star process alongside H1, the energy analysis done for that programme often overlaps substantially with what's needed for H1 modelling. An integrated approach consolidates both into a single workflow rather than running two separate compliance exercises.
The client wants actual performance data
A schedule compliance certificate tells you an element meets a minimum. An energy model tells you projected energy use, heat loss distribution, and the impact of specification changes. For clients deciding between insulation specifications, glazing upgrades, or heating system options, that information has real value beyond the compliance tick.
Non-standard construction
SIPs panels, CLT, rammed earth, or highly unusual geometry may not map cleanly onto schedule or calculation method element categories. The modelling method works from first principles and can accommodate these where the prescriptive methods struggle.
Quick Decision Reference
The Cost Question
Schedule is effectively free — it's a table lookup that a designer can complete in-house. The Calculation Method adds modest cost: a structured calculation that can be completed with BEO's free online tool or as a paid engagement if you want the report prepared and signed off by a building scientist. Full modelling sits at the top of the cost range, but frequently pays for itself when it enables a design that would otherwise require expensive changes or when it consolidates multiple compliance obligations.
The wrong instinct is to treat modelling as the "thorough" option and schedule as the "lazy" one. They're different tools for different situations. A complex design doesn't automatically need modelling; it needs whichever method correctly describes its compliance. A simple design that reaches for modelling is spending money to learn what the schedule table already shows.
H1 Compliance and Energy Modelling Across New Zealand
BEO Buildingscience provides H1 Schedule assessment, Calculation Method reports, and full energy modelling (Modelling Method) for residential and commercial projects across all NZ climate zones. Not sure which method fits your project? Start with our free calculator, or get in touch for a quick conversation at design stage.
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