Warm Roof Systems for Superior Insulation and Building Performance

Maximise energy efficiency and long-term performance with warm roof systems that excel in New Zealand’s demanding climate.

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Energy Savings – Lower power bills with continuous high-performance insulation.

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Tapered Boards – Save time and money by creating the fall within the insulation.

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Moisture Control – Avoid condensation by keeping the roof structure warm and dry.

What Is a Warm Roof - And Why It's Ideal for NZ Conditions

A warm roof is a flat roof system where insulation is installed above the structural deck, rather than below it. This keeps the entire roof structure on the warm side of the thermal envelope, improving thermal stability and eliminating the risk of condensation within the roof cavity.

In contrast to traditional cold roofs, which require ventilation and can result in internal moisture, warm roofs deliver both durability and energy performance in a single, compact system.

Warm roof systems are now widely recognised in New Zealand as the most reliable flat roof solution, particularly as the climate becomes more extreme and building performance expectations become more demanding.

Thermal Efficiency, Airtightness and H1 Compliance Made Simple

Warm roofs support continuous insulation, meaning fewer thermal bridges and a more stable interior environment. This makes it easier for designers to meet or exceed H1 energy efficiency standards, which require higher R-values and encourage a greater focus on airtightness.

Airtightness in warm roofs is improved because the insulation and membrane layers create a tight external shell, allowing internal air control systems to operate effectively.

By integrating airtight membranes, vapour control layers and high-performance insulation like PIR, warm roofs allow designers to confidently target high levels of performance for the building envelope.

Nuratherm Tapered PIR System

PIR insulation designed to create falls. Improves drainage and thermal performance.

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Nuratherm PIR System

High R-value PIR insulation boards for warm roof systems. Lightweight, durable and CodeMark certified.

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Nuraply TPO

Single-ply Nuraply TPO membrane provides watertight integrity for low-slope roofs. For architectural smooth clean lines.

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Nuraply 3PM

Durable bitumen membrane for flat roofs. Offers double-layer waterproofing with a textured mineral chip finish.

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How Tapered Insulation and Substrate Choices Can Save Time and Cost

Many people assume that warm roofs are more expensive than traditional cold roofs. However, when a cost-effective metal tray is used as the substrate in place of plywood, overall build costs can be reduced by more than $50/m². The savings in material and installation time more than offset the additional cost of premium PIR insulation.

For concrete or CLT substrates, tapered insulation provides a smarter alternative to poured screeds. It eliminates the need for wet trades, shortens construction timelines and simplifies sequencing. By combining thermal insulation and drainage fall in one layer, tapered boards streamline installation, ensure effective drainage to outlets and deliver a more efficient and reliable solution than traditional methods.

FAQs

What is a warm roof system and how does it work?

A warm roof places insulation above the roof deck and below the waterproofing membrane. This keeps the structure warm and moves the dew point outside the building envelope, reducing condensation risk. Unlike cold roofs, no ventilation cavity is required, making warm roofs ideal for airtight, energy-efficient buildings in NZ's varied climate.

What are the benefits of installing a warm roof in New Zealand?

Warm roofs improve energy efficiency, simplify H1 compliance and reduce the risk of moisture damage. By placing insulation above the deck, they minimize thermal bridging and help maintain a consistent internal temperature. This improves comfort, lowers heating bills and extends the life of the roof system.

How does a warm roof improve energy efficiency?

A warm roof creates a continuous insulation layer with no gaps or thermal bridges. This reduces unwanted heat loss in winter and heat gain in summer. In New Zealand, where new energy code requirements demand higher roof R-values, warm roofs are one of the most effective ways to meet performance targets.

What materials are commonly used in warm roof construction?

Warm roofs typically use rigid insulation boards such as PIR (polyisocyanurate), combined with a waterproofing membrane - either TPO, bituminous or PVC. In situations where fire performance is critical, ROCKWOOL may be used as an insulating layer. A vapour control layer is recommended for all warm roofs. The substrate can be concrete, plywood, CLT or metal tray profiles.

Can a warm roof be retrofitted over an existing flat roof?

Yes. Provided the existing roof is structurally sound and well bonded, a warm roof can be overlaid with new insulation and membrane. This avoids full tear-off, reducing disruption and cost while upgrading the building's thermal performance and weather resilience. Tapered boards may be used to introduce fall if the existing roof has ponding issues.

Related Webinars

Part two of our Tapered Roof Design series, where we’ll unpack how incorporating drainage slopes can unlock more ambitious, functional, and compliant roof designs.

Smarter Warm Roof Design with Drainage Slopes II

Discussing how incorporating drainage slopes can unlock more ambitious, functional, and compliant roof designs.

Presented by Shane Clarke (Nuralite), Hilton Boshard (Nuralite), Peter Mills (Nuralite) and Erin Hallett (Respond Architects).

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Explore the architectural advantages of integrating tapered falls within warm roof systems.

Tapered Roof Design

Discussing the process, costs and real-life case studies of Nuralite's Tapered Warm Roof Solutions.

Presented by Shane Clarke (Nuralite), Scott Squire (Nuralite) and Peter Mills (Nuralite).

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