The temperature is just right
Joanna Davis finds out what it is it like to live in a passive houses, and if there downsides.
Sian Taylor used to live in a home with stunning views of Lake Wakatipu in a sought-after part of Queenstown. But in winter, ice formed inside the bedroom windows of the 1980s house.
Taylor would come home from work with ‘‘a screaming baby who was hungry’’ and have to light a fire, then wait for the house to warm up.
Taylor, her husband, Mark Read, and daughter, Seren, now aged 7, moved just before 2020’s first Covid-19 lockdown into a new 145-square-metre home that she designed.
The certified Passive House, Threepwood, was awinner at the prestigious 2021 Te Kāhui Whaihanga New Zealand Institute of Architects Architecture Awards.
It’s easy to see the benefits of passive houses – especially compared with older homes that can be cold and damp. But what’s it like to live in one – and are there any downsides?
To be certified, a passive house has to meet strict international standards, including a blower test to show no more than 0.6 air changes per hour.
As well as airtightness, passive houses typically feature mechanical heat recovery ventilation (MHRV); super insulation, including under the slab; and thermally efficient windows that are often tripleglazed to eliminate condensation, draughts and mould.
Comfort
Taylor, who has been certified to design passive houses since 2012, says freedom from feeling cold is one of the main benefits she discusses with her clients.
‘‘No matter the time of year, I never think about: AmI going to be warm or cold when I come home?’’
She appreciates the health benefits of living in warm, dry conditions. ‘‘We’ve never had any condensation anywhere,’’ she says.
‘‘In the winter, you’re just healthier. You’re not feeling that seasonal change when you feel a bit rough.’’
However, she adds: ‘‘One con, and this is not really a con, is my daughter has no idea that outside will be cold. I literally have to force her to wrap up to go to school. She’ll be running around in shorts and T-shirts year-round.’’
Taupō woman Heather Darroch needed a bit of convincing to plan a passive house. It was her husband who was passionate about energy efficiency. The couple has futureproofed their 218sqm fourbedroom, two-bathroom home, by eHaus, which they moved into in November.
They have 20 solar panels on the roof, a charger for an electric vehicle (although they don’t own one yet), a 5000-litre water tank, wider doorways and an accessible shower.
Darroch loves the air quality. ‘‘You walk into each room and it’s the same air quality and temperature,’’ she says.
Bills
Taylor says the ongoing low energy costs are amajor benefit at Threepwood. In summer, solar panels produce ‘‘way more’’ energy than is used. Winter power bills have been low.
Dunedin retirees Frances and Sandy Ross moved last April to a three- to four-bedroom certified Passive House classic townhouse in Dunedin’s Toiora High St cohousing development.
The couple raised their family in a six-bedroom 1920s-era home where they heated only the room they were in.
‘‘Sometimes the [bedroom] temperature went down to 6 degrees,’’ Frances says. ‘‘We just put another blanket on.’’ Now, their home only ever gets as cold as 18.6 degrees Celsius – that’s early in the morning with no extra heating on at all.
Triple glazing means they are unaware of neighbourhood noise such as traffic and lawnmowers, and they also have very low power bills – November’s bill, which included electricity for cooking, hot water and charging their Nissan Leaf EV, was $98.
Cost
When Stephen Canny built his PassivēinOHouse tatara, near Invercargill, it needed to be big enough for regular visits from his and wife Kathy’s six children and 13 grandchildren.
Canny says their two-storey, 290sqm home actually cost less than a standard build because he and Kathy helped to build it and also managed ‘‘a lot of the process and procurement’’ themselves.
They helped build staircases, fixed battens, and did all the exterior painting and timberstaining.
Taylor says experts generally estimate the cost at between
3 per cent and 17 per cent above that of a standard new build.
Two considerations can minimise extra cost, she says: getting the orientation of the house right, and minimising the complexity of the design.‘‘Our house is literally just a square.’’
Technical know-how
Because Canny has been involved in large construction projects professionally, he was confident about managing the purchase of building supplies, including the SIPs (structural insulated panels).
He paid $21,300 (delivered) for triple-glazed windows and doors made by a German company in China. The quote for a local firm was $117,500.
‘‘Normally we’re sticklers for supporting local manufacturing, but there was no comparison in this case.’’
The only downside he experienced was that the solar system installers could not properly integrate the solar hot water system with the underfloor heating and the hot water heatpump.
‘‘I don’t think they had the technical know-how for this kind of activity: They needed to do a bit of upskilling.’’
Designing differently
Ross said there was an element of designing differently, which might not suit everyone.
‘‘The architect told us the trend is to have huge picture windows, but you don’t design passive houses like that.’’
Passive houses can warm up if too much direct sun is allowed to get in, so have to be designed carefully to get the right balance. ‘‘Our upstairs windows are not huge – about 1metre wide.’’
The couple love their new home. ‘‘Passive House makes such a lot of sense. If every bit of heat that you have, including your body heat, is kept overnight, it’s just so sensible. It should be embraced by many more people.’’
Taylor and Read chose their section with the orientation in mind: ‘‘We’re right next to Mark’s granddad’s old farm, which he liked, but it’s also north-facing, full sun.
‘‘The whole of the north facade is glazed. The overhang stops it getting too hot when the sun is high in summer but warms the housewhen the sun is low in winter. Those are real basics that cost no money.’’
Darroch says her new home never gets too hot, unlike the ‘‘to building code’’ home they built in Wellington in 2015, nor too cold like their former 1970s home.
‘‘When we’d been in a couple of weeks, I realised I had a pile to be donated full of electric blankets, duvets, fans and heaters,’’ she says.
‘‘We’re very happy with the spaces and the way it’s worked out. Because it’s a new concept, you do need good guidance. You have to do your due diligence.’’