Even new homes built to code can trap heat and damp, leaving buyers with mould, rot and soaring bills.
While the Building Code has come a long way, it may come as a surprise that even brand-new dwellings built to the current standard may not be as comfortable or habitable as one might expect.
Damp, mould and overheating can and do still occur.
That’s because there is a gap between the letter and the spirit of the law – and into that gap fits the New Zealand Green Building Council’s (NZGBC) Homestar standard.
Without Homestar, says NZGBC Business Development Manager Matthew Cutler, the ghosts of the leaky building saga could continue haunting the land.
“Leaky buildings had to do with weathertightness, letting moisture into homes from the outside,” he says.
“Shortcomings in the building standard that persist to this day mean many buildings could still have moisture problems, except this time it is from the inside. Regardless of its origin, moisture means damp, damp means rot, and rot is destructive and unhealthy.”
Even a brand-new dream home could wind up a sauna in summer or a damp cave in winter if moisture is trapped in. That can happen because of a lack of adequate ventilation, or if there’s not enough shading like window eaves to help prevent the home from overheating.
This oversight can lead to horror stories: “We’re seeing that play out in the headlines of new buildings or units getting so hot they become uninhabitable, and homeowners with no recourse as their dwelling is built to standard,” he adds.
Cutler describes the Building Code clause addressing internal moisture as ‘woefully inadequate’. “We are dealing with freshly built homes that pack in moisture from timber and concrete, and without proper ventilation, it’s trapped. Along with moisture from kitchens, bathrooms and breathing, that can turn into mould and rot. It doesn’t matter where the water comes from, the effect is the same if it’s stuck inside.”
Cutler points out that while the Building Code requires openable windows, that doesn’t guarantee airflow. The real test, he stresses, is whether buyers ask practical questions – for example, will the home have a constant supply of fresh, filtered air, and how much will it cost to keep the whole house at a healthy 20C? Builders and developers, he adds, quickly appreciate the difference when definitive terms are used.
Homestar, he continues, is designed to address exactly these deficiencies in liveability. Available since 2011, it rates dwellings based on comfort, health and energy efficiency. The latest version includes a requirement for continuous mechanical ventilation.
Homestar is intended to contrast the Building Code’s bare-bones approach. “That means less condensation on the windows so the home is more comfortable in winter, and equally so in the warmer months,” he stresses.
Where the code is reactive, Homestar is proactive: “If designers aren’t, for example, doing energy modelling on every new build, then the people moving in are essentially crash test dummies,” he adds.
Building to Homestar levels isn’t just for feel-good vibes; it’s smart business. The features and benefits of these homes can make them more appealing at sale, potentially commanding higher prices.
Some builders can achieve Homestar at no extra cost, while others may see a small uplift of around 0.5% to 1.3%. But with mortgage rate discounts available for Homestar homes – plus the energy savings they deliver – many homeowners could be better off within just a few years, and save tens of thousands over the life of their loan.
As Cutler notes, “There are market incentives which can make it more expensive to not do Homestar. And you’ll avoid potential moisture rot, dangerous mould, and benefit from a healthier and more comfortable home every day.”
That sentiment is shared by developers already embracing the standard. Urban Plus Chief Executive Daniel Moriarty says: “We want to lead by example and demonstrate to other residential housing developers the need to embrace Homestar – the more homes built this way the better. We want to show it’s easily achievable and it benefits society on a greater level.”
Ōtautahi Community Housing Trust Chief Executive Cate Kearney adds: “Using Homestar helps us design and deliver homes that will be dry, healthy and comfortable all year round while keeping energy bills down. It’s a great way for us to achieve our purpose and ensure we’re looking after people and the community.”
With more than 14,000 Homestar homes already built, the standard is setting a new benchmark for Kiwi housing. Homestar-rated dwellings aren’t just built to last; they go beyond compliance to be warm, dry, efficient and ready for the future.
Want to know more? Visit https://nzgbc.org.nz/homestar-for-home-buyers