Tackling Overheating in New Homes: A Growing Concern for Kiwi Families

By James Chong | Published on 15 January 2026

As New Zealand summers become progressively hotter, a growing number of newly built homes are failing to provide safe and comfortable indoor environments. Reports of excessive indoor temperatures, particularly in modern terraced housing and apartment developments, are no longer isolated incidents. Instead, overheating is emerging as a systemic issue with serious implications for occupant health, energy consumption, and the long-term resilience of our housing stock.

Government agencies, industry leaders, architects, and homeowners are now raising concerns that current building regulations have not kept pace with changing climate conditions and housing typologies.

Modern two-story house with large windows and light-colour facade. Long projecting wall, and roof overhang for sun shading. Elevated living area set amidst lush green landscaping and framed by tall trees.

A Regulatory Gap in the Building Code

At present, the Building Act and Building Code do not include explicit performance requirements to limit maximum indoor temperatures in residential buildings. While the Code has progressively strengthened thermal insulation standards (most notably through recent H1 updates), it does not adequately address the risk of overheating, particularly in higher-density housing.

This regulatory gap prompted an open letter to Building and Construction Minister Chris Penk from a coalition of industry leaders, including Auckland Council CEO Phil Wilson and New Zealand Green Building Council CEO Andrew Eagles, alongside architects and construction professionals.

“Too many recently built homes are experiencing unacceptably high indoor temperatures during summer,” the letter states. “The Building Act’s primary goal is to ensure people can use buildings safely without risking their health. Current regulations do not adequately address overheating in higher-density housing.”

Minister Penk has since acknowledged the issue, noting that while insulation standards have improved energy efficiency, ventilation and heat dissipation have not received the same level of attention. He has confirmed that upcoming Building Code revisions will place greater emphasis on reducing overheating in multi-storey dwellings such as townhouses and apartments.

Modern terraced housing features sleek, white sunlit balconies that offer a serene view of lush greenery, with sun shading overhang against a bright sky.

Why Are New Homes Overheating?

Research and post-occupancy studies point to a combination of design, planning, and regulatory factors that contribute to excessive indoor heat in modern homes.

1. High-Density Housing Typologies

Terraced houses and apartments typically have fewer external walls, limited window openings, and shared party walls. This reduces opportunities for natural cross-ventilation and heat escape, particularly in mid-terrace or single-aspect units.

2. Solar Exposure Without Adequate Control

Many developments are designed to maximize daylight and meet minimum sunlight requirements. However, without effective shading, large areas of glazing, especially on north and west-facing façades, can lead to excessive solar heat gain during summer afternoons.

3. Poor Window Placement and Orientation

Incorrectly positioned windows can exacerbate overheating rather than alleviate it. For example, large west-facing windows without shading can cause significant late-afternoon heat build-up, while insufficient opening windows limit night-time purging of heat.

4. Inadequate Ventilation

Both natural and mechanical ventilation systems are often undersized or poorly integrated. In some cases, homes are so airtight that heat becomes trapped, particularly during prolonged warm periods.

An Auckland Council study of newly constructed terraces and duplexes identified poor window orientation, minimal external shading, and a lack of cross-ventilation as the primary contributors to overheating, issues that are largely preventable at the design stage.

The Real-World Consequences

Overheating is not merely a comfort issue. Excessively warm indoor environments can negatively impact sleep quality, productivity, and overall health, particularly for children, the elderly, and those with underlying medical conditions.

To cope, many occupants turn to portable or fixed air-conditioning units. While this provides short-term relief, it also leads to higher electricity bills, increased greenhouse gas emissions, and additional strain on New Zealand’s energy infrastructure.

Climate projections indicate that by 2050, the number of days exceeding 25°C could triple in some regions. Without intervention, today’s overheating issues risk becoming tomorrow’s widespread housing failures. As Andrew Eagles aptly summarized: “It’s like a sauna, without the fun.”

Practical Solutions to Prevent Overheating

The good news is that overheating can be significantly reduced through thoughtful, cost-effective design strategies implemented early in the project lifecycle.

1. Passive Design Strategies

• Orientation: Position living spaces to reduce exposure to harsh summer sun while still allowing winter solar gain.

• Shading: Incorporate roof overhangs, pergolas, external louvers, or retractable blinds to control direct sunlight.

• Material Selection: Use effective roof and wall insulation, light-coloured external finishes, and reflective roofing materials to minimize heat absorption.

  
  

2. Improved Ventilation

• Cross-Ventilation: Design dwellings with openings on opposing façades where possible, allowing air to flow naturally through the home.

• Mechanical Ventilation: Where natural ventilation is limited, specify energy-efficient mechanical ventilation systems designed to remove excess heat without compromising indoor air quality.

  
  

3. Glazing and Window Design

• Use double-glazed or low-emissivity (low-E) glazing to reduce unwanted heat transfer.

• Provide operable windows that allow occupants to control airflow and release heat during cooler evening and nighttime hours.

  
  

4. Landscaping and External Features

• Plant deciduous trees or install green façades to provide seasonal shading.

• Use green roofs or high-albedo (reflective) roof surfaces to reduce heat build-up at roof level.

  
  

5. Thermal Modelling and Performance Testing

Architects can use dynamic thermal modelling tools to predict overheating risks during the design phase. These tools allow designers to test different orientations, shading devices, glazing ratios, and ventilation strategies before construction begins—a practice already standard in Australia and the UK.

Importantly, these measures are not complex or prohibitively expensive. In many cases, small design adjustments can deliver significant improvements in comfort and energy performance without requiring major legislative reform.

An example of passive solar techniques for houses

Design Expertise Matters

With an increasing proportion of new housing delivered as terraces and apartments, reliance on minimum compliance alone is no longer sufficient. Design quality and performance must be prioritized.

Unveil Architects has proven experience in mitigating overheating in high-density residential projects. Our approach considers each site’s unique context, including orientation, material selection, shading devices, window placement, and ventilation strategies. The result is homes that remain comfortable during summer while maintaining strong energy efficiency and architectural integrity.

The Path Forward

As climate conditions continue to change, addressing overheating in new homes is becoming a public health, environmental, and economic imperative. By combining intelligent passive design, effective shading, improved ventilation, and evidence-based performance modelling, New Zealand can ensure its modern housing stock remains safe, comfortable, and resilient for decades to come.

Disclaimer: The views expressed in this post are my own and do not represent the opinions of any organization or employer. The content is for general information only and should not be taken as professional advice.