A warm home provides a haven from life’s storms in every sense – protecting us from the cold rain and comforting us after the buffering of a difficult day. Here’s how to go about creating a cosier and happier home this autumn.
Words Rebekah White and Sarah Heeringa
A house that is warm and dry is essential for our comfort and ongoing good health. And just as it’s hard to be happy when you’re feeling cold or sick, having a warm house also sets the stage for your home to be a more harmonious one.
The World Health Organization recommends a minimum indoor temperature of 18°C in living areas and 16°C in bedrooms. But uninspired design and a general lack of insulation mean that during winter, many New Zealand homes fall below these basic thresholds.
How much does your household spend on power? If your home is not designed to catch and retain warmth, then as sure as autumn follows summer, come the chilly months, you’ll be spending a fair whack of your hard-earned money just trying to keep warm.
According to the New Zealand government’s Energy Efficiency and Conservation Authority (EECA), around 35 percent of the energy used in the average Kiwi household goes on heating. It’s an expensive exercise – and as the effects of global warming start to have a greater impact, energy prices are predicted to rise.
Most of us use electric heaters, gas fires, wood burners or old-fashioned open fires to heat our homes. Some of us remember nasty old flats where you could see your breath inside, ski jackets were de rigueur, and putting the oven on and leaving the door open was the only way to warm things up a bit. Maybe you live in a house a bit like that now.
But we can be smarter than this! If you’re renovating or building from scratch, the right structural modifications can improve energy efficiency and dramatically reduce power bills. But for the rest of us, there are loads of other simple things that can help make your existing heating more efficient. Whether your home is new, old or rented, a few seemingly modest changes in your house or your living habits can make a substantial difference over time.
A house that doesn’t require heating? No, it’s not just a fantasy – and no, it’s not located near the equator, but in the suburbs of Auckland. A real-world, real-time test case dubbed the Zero Energy House, it produces as much energy as its inhabitants consume over the course of a year. It’s packed with clever design tricks to keep it warm and dry at minimum cost. And while it’s connected to the grid, the Zero Energy House both purchases and sells surplus electricity generated on-site. Over the course of a year, the volume of electricity bought and sold equals out to a zero balance. Here’s how it works.
Designed around the sun.
Making smart choices when you’re building results in the biggest energy savings. Capture sunlight by considering which way around the house is oriented, plus the site location, solar aspect and roofing needs.
The Zero Energy House has a concrete floor to capture heat from the sun and release it as the house cools. “To regulate heat capture throughout the year, an overhang was designed for the northern side of the house around seasonal sun angles,” says Matt Fordham, who worked closely on the project along with friends and Zero Energy House owners Jo Woods and Shay Brazier.
“In winter the lower sun angle penetrates under the overhang to heat the slab; in summer the overhang acts as shading to reduce heat capture.”
Build in efficiency. New houses are often designed with the biggest living area allowed. But large houses are less energy-efficient than smaller ones, as bigger spaces require more heating. Shrinking your house plans also frees up money to spend on other things. “At one stage during the Zero Energy House design we shaved about four percent off the building’s size,” says Matt. “This saved enough to pay for the solar hot water and photovoltaic systems.”
Power with solar. All of the energy produced by the Zero Energy House is via roof-mounted solar panels, which cover the entire north-facing section of the roof. There are eight solar hot water panels, plus 88 photovoltaic panels that simply replace ordinary roofing tiles or steel. “One of the main reasons we decided to go solar is financial,” says Matt. “The average Auckland home spends $2,000 a year on electricity – that’s $50,000 over the typical 25-year mortgage term. Our solar system cost a fraction of that, and if we sell the house we can advertise it with up to 25 years of pre-paid power.”
Trade electricity over the grid. The electricity generated from solar photovoltaic panels fluctuates throughout the day and across the seasons, meaning you need a storage solution to even out the peaks and troughs. “We decided not to use batteries because of the high cost and toxic elements they contain, such as lead and acid,” says Matt. “Instead, we’re effectively using the electricity grid for storage. When we generate more than we need, we sell it; when we produce less than we need, we buy it back.”
Live without heating. Thirty percent of the typical Auckland household’s energy bill goes towards heating. The Zero Energy House is designed to not require heating at all! This is because the building envelope retains heat as effectively as possible – plus a double-layer of insulation was installed in the walls, meaning it has a thermal performance 50 percent above the building code. “It also means we avoid ‘cold spots’ common in heated houses,” says Matt. “And because the house is warm in every room it eliminates the health problems associated with moving between warm living areas and cold bedrooms.”
Live without cooling. With such a well insulated home, ventilation is important. But a cooling system can be expensive to install and operate.“We designed the home to be kept cool without the need for systems,” says Matt. “Overhangs on the northern side keep the living areas shaded in summer, and we’ve used dual-tilt windows to allow ventilation. They are secure and sheltered from rain, so we can leave them open to ventilate the house even when no one is home.”
Minimise toxic materials. “Alongside the Zero Energy goal, we wanted to create an environment in and around the house that was as free from toxins as possible,” says Matt. “This meant looking past marketing brochures and researching the actual materials used in products.” The walls feature non-PVC cabling and piping, plus non-VOC paint. The exterior is covered in non-treated macrocarpa cladding. “The cladding smells great and is naturally silvering off over time – during construction the builders were able to work it and leave sawdust to compost directly into the soil.”
Recycle timber. When building a house there are many opportunities to use recycled timber from renovation or demolition projects. The Zero Energy House features flooring made from recycled rimu found on TradeMe, a kitchen island bench made from repurposed decking timber, and kitchen cabinetry made from kauri originally from an old Auckland pub. “Recycling timber doesn’t just reduce environmental impacts – it gives a new home a sense of connection with its wider city surroundings and heritage,” says Matt.
Capture rainwater. “We have a rainwater tank buried at the front of the section that is used to retain water for a variety of uses in the home – toilet flushing, the washing machine, and garden hoses,” says Matt. It’s even used for homebrew! Although the rainwater tank was installed for water conservation reasons, there are also wider benefits – it reduces the volume of water that needs to be both treated at and pumped from centralised reservoirs to city suburbs.
Pumping water. The Zero Energy House has solar hot water panels on the roof, so it needed a smart pumping solution to move water from where it is stored to where it is needed. “We’ve installed an intelligent pumping system that knows when to switch between the normal street supply and the rainwater tank,” says Matt. “It also takes a reading from the hot water cylinder to gauge how fast to pump water around the solar hot water panels – if the water needs significant heating it pumps it slowly, giving it more time on the roof to heat; if it doesn’t need much it pumps it around the roof faster.”
Low-flow taps. Efficient taps and showerheads can significantly reduce the volume of water consumed in the home. For example, the Zero Energy House’s showerheads decrease water consumption by up to 30 percent. This also has an impact on energy requirements. “Because we are heating our water using solar hot water panels, using low-flow showerheads and taps means the size of the solar hot water system can be smaller,” says Matt.
Monitor performance. When you use your appliances can make a big difference, so a monitoring system can help you figure out how to run your home most efficiently. The Zero Energy House’s system reports on energy production and consumption, temperature, humidity, and water flow. For those of us living in conventional homes, innovations such as the new online tool GEM from Mercury Energy can help us track and potentially reduce our power usage.
Not all of us have the option of making large-scale structural home changes. However, there are plenty of deceptively simple ways to make your home warmer and more efficient. Wanganui-based green building expert Nelson Lebo renovated “the cheapest house in New Zealand” (pictured right), transforming it from a rundown wreck to a cosy cottage with power bills of less than $20 per month. What’s more, he did it on a shoestring budget, and in between writing his PhD thesis. Nelson kept a diary of the transformation on his blog, Eco Thrifty Renovation (www.ecothriftydoup.blogspot.com) and now runs community workshops and energy audits helping others. Check out www.facebook.com/ProjectHeatWanganui for more details and advice.