H1/AS1 2025 Changes: The Schedule Method Is Gone — Here’s What You Need To Know

The latest update to H1/AS1 has removed the Schedule Method entirely. This is one of the biggest changes to H1 since 2021, and it affects how insulation, glazing, and overall energy efficiency are shown for consent.

This shift might look like extra work at first, but in reality, it’s going to save money, reduce over-specification, and create more comfortable homes.

And if you want the best results for both budget and performance, using the H1 calculation method or full H1 modelling will give you the most flexibility.

If you are looking for someone to create an H1 report for you, contact us here.

1. The Schedule Method Is Gone — Here’s Why It Matters

The Schedule Method used to offer a quick “table-based” compliance path, but it came with a major downside: it often forced unnecessarily high insulation levels, especially in ceilings and glazing.

Now that it’s gone, all projects must use either:

• The Calculation Method, or

• Full H1 Modelling (VM1)

This shift means compliance is now based on how the building actually performs, not generic assumptions.

2. Why Removing the H1 AS1 Schedule Method Is Actually a Good Thing

Lower build costs

Because the Schedule Method was conservative, many homes ended up with:

• higher R-values than needed

• expensive glazing that didn’t add meaningful comfort

• over-spec’d walls and roofs

With the Calculation Method, we can now match insulation levels to the actual design — meaning you only pay for what’s needed, not what’s assumed.

3. Removal of Ground Floor R-values — What Changed and Why

One of the biggest surprises in the update is the removal of minimum R-values for slab-on-ground floors.

Why MBIE removed ground floor R-values

• Ground performance varies hugely based on soil type, moisture, insulation placement, slab thickness, and perimeter detailing.

• A single table value could not accurately represent real performance.

• Blanket R-values often forced unnecessary under-slab insulation, increasing cost without improving comfort much.

What this means for you

• You only insulate if the design requires it — not because a table tells you to.

• Many clients can now avoid expensive under-slab insulation entirely.

For many standard homes, this is a direct cost saving.

4. Changes to Wall R-values — More Realistic, Less Guesswork

H1/AS1 now aligns more closely with the new modelling rules by requiring more accurate recognition of thermal bridging in framed walls.

Why this matters

Traditional R-value tables assumed perfect performance, but real walls lose heat through:

• studs

• plates

• lintels

• junctions

The updated method provides:

• more realistic wall R-values - now R1.6- for the whole country rather that R2.0

• better alignment between AS1 and VM1

• clearer pathways to reduce glazing performance if wall build-ups are improved

Practical outcome

Builders may see slightly lower R-value ratings for standard framed walls, but architects gain more control through:

• smarter framing layouts

• better insulation placement

• optimised wall systems that unlock glazing flexibility

This is a net positive for most projects.

5. Internal Measurement Rules — Internal Dimensions Only

H1/AS1 now requires all areas to be calculated from internal dimensions:

• wall areas

• roof areas

• floor areas

• thermal envelope boundaries

Why this matters

This will feel painful at first. The industry has relied on external wall measurements for decades, and most design workflows, CAD templates, and drafting habits are still built around external dimensions. This shift means everyone needs to adjust how they take off areas and how drawings are structured.

But despite the initial frustration, this change is good for projects long-term.

Internal measurement:

• standardises calculations across all designers

• removes ambiguity that used to slow consents

• eliminates inconsistent area take-offs between architects, builders, and modellers

• reduces RFIs dramatically by aligning everyone on the same measurement method

• ensures H1 calculations don’t inflate insulation requirements based on cladding, cavities, or external wall build-ups

6. Why You Benefit Most From This H1 AS1 Change

For builders

Less over-specification

The old Schedule Method often forced unnecessary insulation upgrades, especially in ceilings and slab floors. With performance-based calculations, you install only what the design truly needs - no more overbuilding just to meet a table.

Easier pricing and material selection

Because insulation and glazing are now tied to the actual design, pricing becomes far more predictable. You avoid late-stage changes that blow out budgets or require re-quoting.

More predictable outputs for clients

Clients often panic when they hear they “triple glazing”. With proper calculations, most projects land in a far more reasonable range - making the build easier to explain and easier to sell.

Fewer surprise R-value increases at consent stage

Under the new rules, architects and H1 consultants work from the same internal measurement method and the same performance assumptions. This removes the sudden R-value jumps that used to appear once the Schedule Method was checked by council.

For architects

Greater design freedom

You’re no longer boxed in by rigid tables. Shading, orientation, glazing distribution, roof form, and wall build-ups all contribute to compliance now — which means creative architecture is less restricted.

Better glazing flexibility

With accurate performance calculations, you can often keep the design intent without needing expensive low-E upgrades. In many cases, smart tweaks to walls or roof areas free up glazing performance where it really matters.

Cleaner pathways for complex shapes and mixed-use

The old Schedule Method broke down quickly on anything unconventional. The Calculation Method and modelling pathways handle complexity far better - ideal for irregular footprints, large windows, double-height spaces, or mixed-use buildings.

To read about the full H1AS1 changes you can go to the offical Building Performance website here.

7. Calculation Method vs Full Modelling — Which Should You Use?

Calculation Method (AS1)

Great for:

• standard designs

• simple alterations

• homes that are already well-aligned with their climate

• homes with a low level of glazing

Benefits:

• cost-effective

• reduces unnecessary insulation upgrades

• easy to integrate into your workflow

Full H1 Modelling (VM1)

Best for:

• designs with high glazing areas

• architecturally-driven layouts

• clients who want maximum comfort

• cases where you want to lower insulation or glazing specs

• tricky sites or mixed-use

• houses with high levels of glazing

Benefits:

• most flexible pathway

• often delivers the lowest build cost overall

• identifies smart design tweaks that save thousands

• produces the most comfortable buildings

If you want to balance cost, comfort, and design freedom, modelling is the strongest option.

We Can Help You Deliver Consistent H1 Compliance Without Over-Specifying

With the Schedule Method removed, you now need either Calculation or Modelling — and that’s where our expertise makes the difference.

We help you:

• reduce insulation costs

• lower glazing performance requirements

• avoid unnecessary redesigns

• get consents approved faster

• optimise comfort for your clients

Builders, architects, and designers across NZ rely on our H1 reports to keep projects moving with minimal cost and maximum clarity.

If you want an H1 calculation or full VM1 model that just passes without over-spec, we’re here to help. Contact us here to find out more.