Thermal performance has become one of the biggest considerations in modern window and door design. Across the country, homeowners are looking for ways to make their houses warmer in winter, cooler in summer and less prone to condensation. Haydon Rogers, product specifications manager at Altus, says these questions come up in almost every project he sees. People want clarity on R-values, glazing choices and frame types, and how those decisions affect day-to-day comfort.

Understanding thermal performance

At its core, thermal performance is about resisting heat transfer. “R value is the thermal resistance,” says Haydon. “That’s the material property of the window, the door, the wall, whatever it might be within your building envelope that stops the heat transfer from inside to the outside or the outside to the inside.” A higher R-value means better insulation, which helps retain heat in winter and block solar gain in summer.

Matching choices to climate

New Zealand’s varied climates mean there is no single answer. In colder southern regions, triple glazing is increasingly popular. “We want to keep as much of that heat that we’ve generated in the home with your fire or your air conditioning… so triple glazing is quite a good way to do that,” Haydon explains. For Auckland and other temperate zones, double glazing with a thermally broken frame often provides the right balance between performance and cost.

Thermal systems also work in the opposite direction, keeping interiors cooler in hot summers. In areas like Central Otago, where winter nights drop below zero but summer days can top 30 degrees, performance glass helps control overheating as well as retain warmth.

Getting the balance right

Haydon often recommends mixing thermal and non-thermal products depending on orientation and room use. South-facing windows may benefit from thermal frames, while sunnier northern elevations can sometimes perform well with standard systems. The key is to design with the whole house in mind. Fabricators can model R-values for different options, showing how they fit into the overall thermal envelope.

For homeowners, the message is clear. Investing in the right glazing and frames can mean fewer draughts, reduced condensation and lower energy bills, all while making the house more comfortable to live in every day of the year.

Disclaimer: This article is based on a podcast featuring insights from experienced professionals and is intended for general information and inspiration only. While we aim to share valuable guidance, please seek personalised advice from qualified professionals before making decisions about your property, finances, or renovation plans.