New Zealand’s energy efficiency rules (H1):

What’s changed for glazing, what to specify, and why timber joinery performs so well

By Aaron Dando – Owner, Dando Doors and Windows

If you’re building a new home, or doing a major renovation, you’ll hear the term “H1”. H1 is the New Zealand Building Code’s energy efficiency clause. It influences insulation, windows, and glazing performance.

MBIE updated the H1 documents in late 2025, with a transition period through to late 2026. The practical impact is that glazing is now more often treated as a performance input to compliance, rather than a simple note on the plans. This is not new news to most architects and energy assessors. However, it is very relevant for builders, developers and homeowners when it comes to quoting, procurement, and avoiding late changes.

We’re Dando Doors and Windows, a timber door and window manufacturer. This article explains how glazing is now typically handled, what flexibility remains, and what information we need to price and manufacture accurately.

1. Glazing isn’t just “double glazing” anymore

For many projects, the note “double glazing throughout” is now too vague at pricing stage.

That’s because there are multiple performance levels, and appearances, within double glazing. For example clear double glazing, Low E double glazing, Low E plus argon, warm edge spacers, different glass thicknesses, acoustic laminates, and safety glass requirements.

These choices can affect
• energy efficiency performance
• comfort and condensation behaviour
• the visual appearance of the glass
• cost and lead time, especially for large glazed doors

In short, glazing is often part of the energy efficiency compliance evidence, so it pays to confirm the intent early, before the job is priced and ordered.

2. Who decides the glazing performance

In practice, glazing performance is determined by the design team.

The architect or designer issues the drawings and specifications and controls the consent set. Sometimes an energy assessor or modeller is involved, particularly where modelling is used.

As the joiner, we don’t pick the H1 inputs. We manufacture to the specification and can offer options, but the project needs a clear glazing basis so the quote matches what will ultimately be approved and built.

3. Why plans and compliance documentation need to match, especially with modelling

Where modelling is used, the energy analysis is expected to align with what is shown in the consent documentation, as closely as reasonably practicable. The reason this matters is simple.

If the model assumes Low E plus argon, or a certain solar performance, but the drawings or specs only say “double glazing”, you can end up with late changes once someone locks in the compliance basis.

Late changes can mean repricing, variations, delays, and sometimes rechecking compliance.

Even when you’re not modelling, many teams now treat glazing as something that should be clearly specified early to keep procurement smooth.

4. A key shift from the old approach: less “minimum glazing R value”, more whole building performance

In earlier versions of the rules, it was common to see glazing discussed as a simple minimum “R value” requirement. For example R0.46 was a common benchmark for windows and doors in some zones in the previous framework.

Under the current framework, glazing is typically treated as an input into the overall calculation or modelling approach, rather than relying on one simple minimum note on the drawings.

For builders and homeowners, the takeaway is this
• you may see more projects using a window performance schedule
• you may see a clearer glass make up specification
• you may see less reliance on a single “minimum glazing R value” line

5. Timber joinery: warmer by design, and the numbers people care about

Timber is a naturally insulating material, and the frame is a real part of the overall window and door performance, not just the glass.

Using the current typical housing reference table commonly used for housing comparisons, timber framed windows and glazed doors sit at approximately
• R0.44 for a common clear double glazing performance band
• R0.56 for a common Low E double glazing performance band

In the same reference table, thermally broken aluminium sits lower for the equivalent glazing bands. In plain terms, on these common comparisons, timber framed windows and glazed doors deliver around 37.5 percent to 43.6 percent higher R value than thermally broken aluminium, noting that actual results vary by window size and design.

Why that matters is simple. Higher R value means less heat transfer through the window or door system. This typically improves comfort and helps reduce condensation risk, especially in bedrooms and living areas with large glazed openings.

6. Can a new build still use single glazing

In some special cases, single glazing can be explored, but only if the project’s designer or energy assessor can demonstrate compliance through the energy efficiency calculation or modelling approach.

Single glazing usually makes compliance harder unless other parts of the home are upgraded, for example roof, walls and floor, and or window areas are kept modest. In practice, most homeowners still choose double glazing, clear or Low E, for comfort, condensation control, and resale expectations.

The key point is that if a project team wants to explore alternatives, it needs to be done early and documented clearly so the quote, consent set, and compliance basis all line up.

7. Clear double glazing vs Low E: performance and appearance

This is one we discuss often with homeowners because it affects both feel and aesthetics.

In the past, when projects were commonly trying to meet a simple minimum glazing R value benchmark, Low E was often the default choice to help achieve the required performance. With the current approach being more flexible and more often supported by calculation or modelling, some projects can potentially meet the overall requirements using clear double glazing, depending on the design, glazing area, insulation levels, and other factors.

For many homeowners, the appeal of clear double glazing is simple
• it is usually the most neutral and crystal clear in appearance
• it can offer cost savings compared with higher performance glazing options

Low E double glazing can provide improved thermal performance, but it can sometimes show a slight tint, and in certain angles or lighting conditions it can show a subtle haze, sheen, or reflective film effect. This is often a normal visual characteristic of the coating interacting with daylight or strong internal LED lighting, not necessarily a defect.

If you’re sensitive to glass clarity, large feature glazing, strong downlights, or carefully curated interior finishes, it’s worth discussing early. We can help confirm glazing options and pricing so your final selection matches the look, comfort, and project requirements.

8. What we need to quote accurately, so you avoid late changes

To keep pricing clear and avoid variations, we ask for one of the following from the architect or designer.

Option 1, best, a performance requirement
A window and door schedule that states
• the required window and door performance, often shown as Uw or R value or Rwindow
• if modelling is used, any solar performance requirement, often called SHGC, and relevant shading assumptions

Option 2, a clear glazing specification
A schedule or spec clause that clearly states
• clear vs Low E, whether argon is used
• glass thickness and cavity, the insulated glass unit build up
• spacer type
• any safety or acoustic requirements

If the plans only say “double glazing”, we can still price, but we may need to provide options, because different double glazing make ups can perform, and look, quite differently.

9. Why early clarity saves time and money

When glazing is clearly specified early
• quotes are comparable, apples with apples
• lead times are more predictable
• there are fewer variations
• what gets installed matches the project’s energy efficiency compliance basis

Want help choosing the right glazing

Send us your plans and window schedule, even at concept stage. We’ll help you compare clear double glazing vs Low E vs Low E plus argon, explain the appearance differences, and make sure the quote reflects what’s intended for the build.

Need advice

If you are unsure about
• correct painting requirements
• warranty conditions
• maintenance obligations
• best practice for timber joinery

Please contact us early. We are always happy to help clarify what is required.

📍 Auckland showroom
🚚 Nationwide
🧾 Free estimates & technical guidance

Browse:

• Timber Windows Range → here

• Timber Doors Range → here

• Bifold Windows → here

• French Doors → here

Why Timber Joinery Fails – And It’s Usually Not the Joinery

Understanding the Critical Role of Correct Painting on Timber Windows and Doors

By Aaron Dando – Owner, Dando Doors and Windows

At Dando Doors and Windows we manufacture high-quality timber windows and doors designed for New Zealand conditions.

Our joinery is carefully crafted using proven systems and quality materials, and is built to provide many years of reliable service.

However, once our products are installed on site, their long-term durability depends heavily on one final stage:

The quality and completeness of the painting system applied by others.

Over many years we have seen the same pattern repeat:

Well-made timber joinery fails prematurely not because of manufacturing defects, but because essential painting requirements are not followed on site.

The Reality: We Don’t Control the Painter

Every set of joinery we supply includes written care and warranty instructions.

These instructions clearly state what must be done to protect timber joinery from moisture and weather exposure.

But as the joinery manufacturer we do not:

• engage the painter

• supervise the painter

• control their scope of work

• apply the coatings ourselves

That responsibility sits with the builder or homeowner.

When those instructions are not followed, the consequences are predictable:

• early paint failure

• swelling and movement

• moisture ingress

• deterioration of glazing beads

• reduced lifespan of double glazing units

• and eventually – timber decay

This is frustrating for everyone involved – particularly when the root cause is avoidable.

Two Critical Painting Requirements That Are Often Missed

There are two simple but essential requirements that protect timber joinery from moisture ingress.

Both are clearly stated in our warranty documentation. Both are supported by NZ standards and industry guidance.
And both are regularly overlooked.

Requirement 1 – Paint Must Overlap Onto the Glass

Our Care, Maintenance and Warranty document states:

“The paint skin should overlap onto the glass 2mm on the exterior surface to ensure a proper seal.”

It also requires:

“A complete waterproof paint skin must be maintained at all times on all edges.”

This overlap detail is not cosmetic – it is functional.

Why the Paint Overlap Matters

The junction where glass meets timber – at the glazing bead – is one of the most vulnerable moisture points in any window or door.

Even with modern glazing tapes and sealants, there is still a fine interface where moisture can sit or slowly track into the timber.

To protect this junction, best practice requires a continuous paint film that bridges from the timber onto the glass.

Paint that stops neatly at the edge of the bead may look tidy, but it leaves a microscopic pathway for water.

This Is Confirmed by Resene Technical Guidance

New Zealand’s leading paint manufacturer Resene advises:

“Ideally, you need to overlap the primer and topcoats up onto the glass by 2–3mm. This provides a watertight seal so moisture cannot get between the glass and putty.”

Although modern joinery uses timber glazing beads rather than traditional putty, the technical principle is identical:

Seal the timber-to-glass junction with a paint overlap.

“But We Don’t Use Putty Anymore”

Correct – and that does not change the requirement.

Whether the interface is:

• putty to glass, or

• timber glazing bead to glass

…it remains a critical moisture entry point.

The paint overlap requirement applies to both systems equally.

Requirement 2 – Tops and Bottoms Must Be Fully Sealed

The second common failure is even more basic.

Painters frequently omit:

• the top edges of doors

• the bottom edges of doors

• the tops and bottoms of window sashes

Because these areas are not readily visible, they are often left uncoated.

Unfortunately, they are also the areas most prone to moisture uptake.

Industry Guidance Agrees

The Master Painters NZ Association advises that:

“Failing to seal the top and bottom edges of the door is likely to void the door manufacturer’s warranty.”

Unsealed edges are a well-recognised cause of:

• swelling

• paint breakdown

• moisture ingress

• premature timber decay

This Is Backed by NZ Building Code and Standards

New Zealand Building Code durability provisions and NZ Standards require that:

• Timber components must be protected from moisture

• Protective coatings are applied to all surfaces

• Finishes are applied in accordance with manufacturer specifications

AS/NZS 2311 – Guide to the Painting of Buildings – reinforces the need for complete coating systems to protect timber joinery from weather exposure.

When coatings are incomplete, the building element is no longer adequately protected.

It Also Affects Double Glazing Warranties

Many people don’t realise that poor painting can also affect the warranty on insulating glass units.

Double glazing warranties generally require that joinery is maintained in accordance with the joinery manufacturer’s standards and care instructions.

Painting is therefore critical not only to the timber, but also to the long-term performance of the glazing.

Why This Is a Difficult Issue for Joinery Manufacturers

We invest significant time and effort producing joinery that is designed to perform for many years.

When painters do not:

• overlap paint onto the glass, or

• seal tops and bottoms

…the joinery is left unprotected.

Years later, when problems appear, we are often asked to assess issues that are the result of incomplete or incorrect painting, not manufacturing defects.

What Builders and Homeowners Need to Ensure

If you are responsible for painting timber windows and doors, it is essential to ensure the following:

At the glazing bead:

• Primer, undercoat and topcoats extend onto the glass by approx. 2mm

• A continuous paint film bridges timber to glass

• This applies to modern timber glazing beads as well as traditional putty systems

On doors and sashes:

• Tops and bottoms are fully sealed

• All six faces are coated

• No raw timber edges remain

General requirements:

• Coatings applied in accordance with AS/NZS 2311

• Manufacturer specifications followed

• Quality exterior-grade paint systems used

Our Position

At Dando Doors and Windows we stand fully behind the quality of our manufacturing.

However, we cannot be responsible for:

• painting carried out by others

• incomplete or incorrect coating systems

• instructions that are not followed

Timber joinery will only perform as well as the protection applied to it.

Our Recommendation

To ensure long-term durability and full warranty protection:

• Overlap paint onto the glass by approximately 2mm at all glazing beads

• Fully seal tops and bottoms of all doors and window sashes

• Follow our written painting instructions in full

These are small details, but they have a major impact on performance and lifespan.

Need Advice?

If you are unsure about:

• correct painting requirements

• warranty conditions

• maintenance obligations

• best practice for timber joinery

…please contact us before painting begins.

We are always happy to help clarify what is required.

📍 Auckland showroom
🚚 Nationwide
🧾 Free estimates & technical guidance

Browse:

• Timber Windows Range → here

• Timber Doors Range → here

• Bifold Windows → here

• French Doors → here

Timber vs Aluminum Windows in NZ: Insulation, Condensation & Comfort (2025 Guide)

Replacing windows is one of the most effective ways to improve comfort, warmth and energy efficiency in a New Zealand home. But most people focus only on the glass — when in reality, the window frame material plays a major role in insulation and condensation control.

This 2025 guide explains the real differences between timber and aluminium windows under New Zealand climate and building standards, helping homeowners, builders and architects make fully informed decisions for renovations and new builds.

1. Timber provides the best insulation for New Zealand homes

When comparing window frame materials, the biggest difference is how much heat each material conducts. This directly affects comfort, warmth and energy efficiency.

• Standard aluminium frames conduct heat very easily — they quickly transfer outdoor temperature inside, making homes colder in winter and hotter in summer.

  This results in lower overall insulation performance, even with good double glazing.

• Thermally broken aluminium improves performance — a “thermal break” reduces heat transfer through the frame.

  This allows aluminium to meet the minimum H1 energy code when combined with high-performance glass, but it still performs below timber overall.

• Timber is naturally insulating — it slows heat transfer between inside and outside, helping the home stay warmer, drier and more stable in temperature.

  Timber consistently offers the highest insulation performance when paired with modern double glazing.

Because the frame accounts for 15–25% of the total window area, upgrading the frame material can dramatically improve the real-world warmth and comfort of the home.

2. Timber significantly reduces condensation and mould

Condensation forms when warm indoor air meets a cold surface. Aluminium frames get cold quickly, promoting condensation, especially in bedrooms and bathrooms.

Timber frames retain heat and stay warmer internally, which:

✔ reduces visible condensation

✔ protects paint and seals

✔ prevents mould growth and sill damage

✔ creates a drier, healthier home

For families and asthma-sensitive homes, this is a major comfort and health benefit.

3. Pricing has changed — aluminium is no longer the “cheap” option

Historically, aluminium was significantly cheaper. But under the updated H1 Energy Efficiency requirements, standard aluminum no longer meets insulation performance in most new builds.

To comply, aluminum must now be thermally broken, which:

• adds cost

• adds plastic components

• adds manufacturing complexity

As a result:

The price gap between aluminium and timber has reduced significantly.

Today, homeowners are comparing thermally broken aluminium vs timber, not “cheap aluminium vs timber.”

4. Installation, flashings and weathertightness — who is responsible for what

Windows are only one part of a weatherproof wall assembly.

Weathertightness is achieved through the cladding, flashings, building wrap and sealing, not the joinery alone.

We do not supply flashings, because they are specific to the cladding system and building consent drawings. The builder is responsible for:

• installing sill and head flashings

• integrating the frame with the building wrap

• sealants and finishing systems

• following E2/AS1 and the consented details

Our role is to supply joinery that meets NZS 4211 — Performance of Windows.

Correct installation and finishing are required to achieve full weathertightness.

5. Glazing options — the best insulation comes from the right combination

We manufacture joinery to accept a full range of glazing options:

• Low-E double glazing

• Argon gas fill

• Safety glass (toughened/laminated)

• Acoustic glazing

• Privacy glass

The best thermal performance comes from combining:

an insulating frame + high-performance glass

6. Protecting your investment — painting and maintenance

To protect performance and warranty:

Before exposure to weather:

• Apply two top coats of quality exterior paint or film-forming clear finish

• Paint all six surfaces — front, back, top, bottom and both sides

• Prime any areas where timber is removed for hardware

Ongoing care:

• Clean annually

• Recoat when early signs of paint wear appear

• Avoid dark exterior colours (LRV < 45) on sun-exposed elevations

• With proper finishing and maintenance, timber joinery delivers decades of reliable performance.

Ready to compare options or get pricing?

Email your plans or measurements for a fast quote: info@dando.net.nz

If you’re comparing timber and aluminum joinery and want to understand the performance and price differences for your home, our team is here to help.

We manufacture NZS 4211 tested, JMF-certified, double-glazed timber joinery for homes across New Zealand and were recognised by JMF in 2025 as the largest NZ timber window and door producer nationwide.

📍 Auckland showroom
🚚 Nationwide
🧾 Free estimates & technical guidance

Browse:

• Timber Windows Range → here

• Timber Doors Range → here

• Bifold Windows → here

• French Doors → here

Timber vs Aluminium Windows in NZ – FAQs

Are timber windows warmer than aluminium in New Zealand homes?

Yes. Timber is a natural insulator, so timber window frames conduct far less heat than standard aluminium. This helps keep more warmth inside in winter and reduces overheating from sun-exposed frames in summer.

Do timber windows help reduce condensation?

Timber frames stay much closer to the indoor temperature because they don’t conduct heat like aluminium. That means the frame surface is warmer on cold mornings and less likely to attract condensation compared to standard aluminium frames.

Are thermally broken aluminium windows as good as timber for insulation?

Thermally broken aluminium is a big improvement over standard aluminium and can perform well when paired with good double glazing. However, timber still has better natural insulation and usually outperforms aluminium in frame-only comparisons.

Which window type is quieter – timber or aluminium?

Both frame types rely mostly on the glass and seals for sound control, but timber’s density and natural damping often give it an edge over standard aluminium frames, especially in older homes where aluminium joinery can rattle or flex.

How much maintenance do timber windows need?

Exterior timber needs regular painting or staining to keep moisture out, just like weatherboards or barge boards. If they are properly primed, painted and kept well-sealed (especially on the top and bottom edges), modern timber windows are durable and low hassle.

How long do timber windows last compared to aluminium?

Well-made, well-painted timber windows can last many decades in New Zealand conditions. Aluminium won’t rot, but powder coating can chalk and fade, and standard aluminium can struggle with condensation and thermal performance over time.

This article is general industry guidance. Performance outcomes depend on glazing type, installation quality, building design and maintenance. Refer to your building consent documents and builder for project-specific requirements.