Why Warm Roofs Save Energy in New Zealand

A Smarter Approach to Building Thermal Performance

Energy efficiency has become a defining focus in New Zealand construction. With the introduction of further H1 energy-efficiency requirements, rising operational energy costs, and growing sustainability expectations, thermal performance has become a hot topic. Among the most effective strategies for improving thermal performance and building longevity is the adoption of warm roof systems.

A warm roof places insulation above the structural roof deck, creating a continuous thermal layer. This system design reduces heat loss, manages condensation risk, and delivers long-term durability and performance advantages—making it a preferred solution for building owners, developers, and specifiers across the country.

Warm roof systems are now widely recognised as the standard for high-performance commercial roofs in New Zealand, particularly for Green Star-rated buildings and projects seeking long-term sustainability and operational efficiencies.

How Warm Roofs Work

Traditional cold roof build-ups position insulation below the roof structure, allowing the roof deck and framing to remain cold. In New Zealand’s varied and often humid climate, this can lead to interstitial condensation forming within the roof cavity, creating long-term risks such as mould, corrosion, and structural damage.

Warm roofs reverse this logic by placing insulation above the structural deck and beneath the waterproofing membrane. This keeps the deck warm, stable, and protected while moving the dew point outside the building structure.

This design offers several critical benefits:

• A continuous thermal envelope with minimal thermal bridging
• Condensation risk virtually eliminated within the roof structure
• Passive performance—no mechanical roof ventilation required
• Membrane longevity improved by temperature stability below the waterproofing layer

Hybrid insulation solutions—such as PIR board combined with internal ceiling insulation—can also be incorporated to achieve project-specific thermal targets and optimise performance.

Key Benefits for Architects and Specifiers

✔ Energy Efficiency

Warm roofs significantly reduce heat loss, helping buildings maintain stable internal temperatures year-round. This reduces heating and cooling loads and supports compliance with updated H1 energy-efficiency requirements.

✔ Condensation & Moisture Control

By shifting the dew point outside the roof structure, moisture and condensation risk inside the ceiling cavity is eliminated. With no moisture build-up, there is no need for mechanical roof ventilation, reducing roof penetrations and protecting the waterproofing integrity.

✔ Healthier Indoor Environments

Preventing condensation and mould contributes to healthier indoor air quality—supporting building wellness goals and long-term occupant comfort.

✔ Space Efficiency

With no requirement for ventilation hardware, warm roofs provide more usable service space in the ceiling cavity, simplifying coordination for mechanical and electrical services.

✔ Design Flexibility

Warm roofs can be specified across a wide range of roof structures, including:

• Flat and low-slope commercial roofs
• Podium structures
• Terraces and landscaped roofs
• Solar-ready and green-roof ready roofing systems

✔ Proven New Zealand Performance

Equus Soprema has supplied warm roof solutions in New Zealand since 2008. Today, over 70% of new flat roofs installed through Equus are designed as warm roof systems—a testament to industry confidence and performance history.

Certified Systems for New Zealand Conditions

Equus Soprema warm roof systems provide robust compliance and assurance pathways, with independent quality verification and system certification.

Key approvals and warranties include:

• Codemark certification for bitumen membrane warm roofs down to 1:100 falls
• BRANZ Appraised warm roof systems and membranes
• Material warranty up to 20 years on all systems
• Duotherm Warm Roof: warranty up to 25 years, including 20-year manufacturer insurance-backed membrane warranty

These certifications ensure performance and compliance under New Zealand Building Code conditions, giving specifiers confidence in long-term results.

Technical Support & Project Assurance

Equus Soprema provides technical support throughout design and specification, including:

• Project-specific Condensation Risk Analysis (CRA)
• Wind uplift calculations
• H1 compliance
• Full detailing review and support
• Building Compliance Pathway documentation

These technical services streamline specification, reduce time-consuming RFIs, and ensure each warm roof is engineered to suit its project, climate zone, and building use case.

Every warm roof is supported through design, approval, and construction phases, helping deliver compliant, durable, and high-performing building envelopes.

Performance in Sustainable and Low-Carbon Construction

Warm roofs are increasingly specified in Green Star buildings due to their thermal efficiency and ability to stabilise internal temperatures. By improving passive energy performance and reducing HVAC load, they contribute directly to lower operational energy use and carbon reduction goals.

When paired with systems like Soprasolar pedestals for solar photovoltaic integration or green roof build-ups, warm roofs become a key platform for high-performance and future-ready building design.

A Sustainable, Future-Proof Roofing Solution

Warm roofs are now considered best-practice for energy-efficient commercial roof design in New Zealand. With proven performance, strong compliance pathways, and industry adoption accelerating, warm roof systems offer a smarter, more resilient roofing solution for modern buildings.

By insulating and waterproofing above the structural deck, architects can deliver buildings that are more energy-efficient, healthier, and longer-lasting—ensuring enduring value for clients and better outcomes for occupants.