---
title: "Insulation (H1) Rules: When a Shed or Commercial Building Needs Them"
description: "H1 is the part of the Building Code that deals with energy efficiency: how well a building holds heat, through insulation, glazing and airtightness. For houses, it’s well known. For steel commercial and industrial buildings, the key question is simpler:…"
url: "https://steelspan.co.nz/advice/insulation-h1-rules-when-a-shed-or-commercial-building-needs-them/"
updated: "2026-11-09"
category: "Consents & Rules"
---

# Insulation (H1) Rules: When a Shed or Commercial Building Needs Them

H1 is the part of the Building Code that deals with energy efficiency: how well a building holds heat, through insulation, glazing and airtightness. For houses, it’s well known. For steel commercial and industrial buildings, the key question is simpler: which parts of the building will be heated or cooled?

## Conditioned vs unconditioned space

The H1 documents use two terms that matter here:

- **Conditioned space** is the part of a building that may be heated or cooled, directly or indirectly.
- **Unconditioned space** is everything inside the building envelope that isn’t.

In a typical warehouse or workshop, the big open floor is often unconditioned, while the office, showroom, lunchroom or a temperature-controlled area is conditioned. H1 requirements focus on the conditioned parts, so the layout decides a lot of the cost.

## Which compliance path applies

- **H1/AS2** applies to buildings other than housing with more than 300 m² of occupied space. When working out that area, parts classified as industrial, outbuildings or ancillary are left out.
- **H1/AS1** (or the H1/VM1 calculation method) covers housing and smaller non-housing buildings.
- **HVAC systems** in larger buildings have their own verification route and need a mechanical engineer’s input.

Your designer confirms the classified uses and which path applies. This affects insulation levels in roofs, walls and floor slabs, window performance, and in larger buildings, lighting power.

## What it means in practice

- **An unheated farm shed or storage building** usually has no H1 insulation requirement, though you may still want insulation for comfort or to control condensation.
- **A workshop with a heated office** needs the office area to meet H1. Putting the office in one corner, with an insulated wall between it and the workshop, keeps the conditioned area small.
- **A showroom or office building** needs the full treatment: insulated roof and walls, compliant glazing and, for larger buildings, lighting and HVAC checks.

## Insulating a steel building

Steel buildings insulate well when it’s planned. Roofs can take insulation blankets under the cladding, walls can be lined with insulated systems, and slab edges can be insulated where required. Planning it at the design stage is far cheaper than adding it later.

## How Steelspan approaches H1

We work out conditioned and unconditioned areas at the design stage, so the H1 cost is in the budget estimate rather than discovered at consent.

## Talk to Steelspan

Tell us which parts of your building you’ll heat or cool, and we’ll design the envelope to suit. Use our Easy Shed Quote or call 0800 787 726.