The Building Code's insulation tables disappear in November. Here's what changes.

What is changing

For years, the easiest way to show a new house met H1 was the schedule method: a lookup table of minimum insulation values for the roof, walls, floors, windows, and doors. Hit the numbers in the table and you were done.

The sixth edition of the acceptable solution for housing (H1/AS1) removes that table. The older edition can still be used for building consent applications until 26 November 2026. After that, the schedule method is gone, and every new home proves compliance one of two ways: the calculation method or the modelling method.

This is a change of method, not a change of standard

Worth being clear on one point, because it has been muddled in a bit of the noise around this. MBIE's position is that the level of energy efficiency a home needs to reach has not changed. The performance is the same. What has changed is how you demonstrate it. The rigid one-size table is out, and a whole-building assessment is in.

Why that is actually good news

The schedule method was simple, but simple came at a price. Because it fixed a minimum for every element, it left no room to trade off. Want more glazing on the north face to capture winter sun? The table did not care. You still had to hit every other number regardless.

The calculation and modelling methods look at the building as a whole. They let a strong element make up for a weaker one, as long as the total heat loss is no worse than a reference home built to code. In plain terms, the budget can go where it earns comfort, rather than where a table said it had to.

The modelling method goes further again. It runs a full thermal simulation of your actual design against a reference building, and it accounts for things the table never could, like orientation and solar gain. For anything with generous glazing or an unusual form it is often the only sensible route, and it shows you running costs and summer overheating risk while it is at it.

What it means if you are about to build

If your consent goes in before 26 November 2026, you still have the choice, and which edition suits your design is a decision worth making deliberately.

If it goes in after that, your home will comply by calculation or modelling. That is not a burden. Done early it is an advantage, because the trade-offs only pay off when the big decisions, orientation, form, glazing, and construction build-ups, are made at the start. The expensive version of H1 is the one patched together at consent, when a late cladding change quietly breaks the numbers.

Either way the takeaway is the same. Energy performance is now a design conversation, not a box ticked at the end. That suits how we work anyway.

How we handle it

We run H1 compliance in-house as part of our documentation. We use the calculation method routinely and model where the design warrants it. If you are planning a build that will consent in 2026 or later, we will confirm the right pathway for your project at the start, not at the end.

Thinking about a build? Get in touch, or download our H1 Compliance Guide for the full picture.

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