Damien McGill, an engineer by trade and member of the Superhome Movement, says it’s no more expensive to run heat pumps full-time, and that doing so has health benefits, for humans, and for the building.
McGill has been monitoring three adjacent units he owns in central Christchurch. He lives in one himself and has not found any significant difference in his power bill from leaving the heat pump running 24/7 set at a constant 18 degrees Celsius.
“If you’ve already got it at 18, it doesn’t use much energy to heat to 20 or 21 degrees. If it gets down to 12 or 14 degrees then the heat pump has to work hard out to get it back up,” he says.
“It hasn’t cost me any more.”
However, McGill recognises that this advice may not work for everyone.
So Stuff called in the experts: Scientist Andrew Pollard, from building research organisation BRANZ, and Gareth Gretton, from government agency EECA, the Energy Efficiency and Conservation Authority.
Unfortunately, the answer is not simple.
Gretton says it is context-dependent.
If a house is extremely well-insulated and air-tight, it will not cost much to maintain at about 18 degrees, leaving a heat pump running even when no-one is home or overnight.
But most New Zealand homes are single-glazed and not optimally-insulated, and therefore leak heat.
“For your average New Zealand house with quite a lot of heat loss, leaving it on all the time is going to use a lot of energy.”
Instead, EECA’s advice is to run the heat pump when people are home, and to use a timer.
”You can set it to turn on just before you get home, or before you wake up in the morning. Doing that also means you’ll be less tempted to crank the heat pump at a high temperature when you get home to a cold house, or wake up in one.”
He said, of course if people were home during the day with children, working from home, or for any reason, to keep the heat pump running for comfort.
Gretton said he strongly recommended people leaving for the day should ventilate their home well beforehand.
”That’s 10 minutes of windows wide open – let all that air out of the house before you leave for the day.
You’re filling your house with nice dry morning air, and since you’re about to leave, it doesn’t matter that you’ve lost the heat.” He recommended buying a temperature and humidity sensor, so that people could “learn to operate their house”.
”A famous architect once said a house is a machine for living in. We need an instruction manual for the machine. By buying a sensor, you can learn how to operate your house.”
Pollard agreed that relative humidity was also important to control: People should aim for humidity between 40 and 60 per cent.
“A lot of homes will average about 70 per cent: That’s where the mould starts to grow,” he says. “It’s invisible before it becomes visible. It can hide behind surfaces, so often behind wallpaper rather than on the surface.”
To control humidity, people needed to heat their homes, ventilate, and also reduce the amount of moisture being released into the home’s atmosphere – for instance by using a rangehood when cooking, by not drying laundry inside, by closing bathroom doors and using extraction fans in the bathroom.
Pollard said children’s rooms should be heated overnight to the 18 degrees Celsius recommended by the World Health Organisation, but a small electric heater was a better way to do this than a heat pump, unless a ducted central heating-type system was installed.
“If it’s very cold outside, they’re working harder and are less efficient. Sometimes the outdoor unit has to be defrosted, actually blowing cold air inside. A 2015 study showed they actually produced twice as much heat energy as the energy that went into them.”
BRANZ studied New Zealanders’ use of energy in the home in its 1995 to 2005 Household Energy End-Use project, finding most houses were under-heated, too cold and “creating unhealthy living environments”.
Another study is underway.
source: stuff.co.nz
Need helping finding the best heating and cooling solution for your home? G-Force Healthy Homes Solutions offer a FREE, no obligation Measure and Quote Service which helps take away the headache and expense of getting it wrong.
OTHER HANDY RESOURCES
- Cold and Damp Home? Why YOUR HOME’S Indoor Air Quality Matters
We spend a significant amount of time indoors – at home, at work, even in our cars. It’s easy to assume that because these spaces offer shelter, they must be healthy environments. But the truth is, a poor indoor environment can have a surprisingly big impact on our health, especially a cold and damp home.… Read more: Cold and Damp Home? Why YOUR HOME’S Indoor Air Quality Matters - EECA BUILDING EXPERT SHARES TIPS FOR HAVING A WARM HOME ON A BUDGET
EECA building expert Dr Gareth Gretton shares some tips on how to prepare your home. How quickly the cold seeps into your home depends a lot on how well it’s insulated, Gretton said. “The best place to start is actually underneath… that keeps the heat in and stops the drafts coming up.” He recommends checking… Read more: EECA BUILDING EXPERT SHARES TIPS FOR HAVING A WARM HOME ON A BUDGET - GET AN INSTANT HEAT PUMP QUOTE
The crisp mornings and cool evenings are a gentle reminder that winter is truely on its way. For many homeowners, this means prepping the trusty heater and hoping it survives another season. But what if there was a more efficient, cost-effective way to keep your home cozy? Enter the heat pump! Heat pumps have become… Read more: GET AN INSTANT HEAT PUMP QUOTE - How do I get AN insulation GRANT IN NZ?
The Warmer Kiwi Homes Government programme offers insulation grants to low-income home owners (you must be a owner-occupier). You can get 80% paid for by the warmer kiwi homes grant. - MARCH HEAT PUMP SERVICE SPECIAL*
Heading into winter is a great time to get a heat pump service. Check out our Heat Pump Servicing special below and book your clean in so you can enjoy a warm home this winter. Specialoffer $170 + gst - How much does it cost to install a heat pump NZ?
Heat pumps are good for your wallet and the environment but how much does it cost to install a heat pump in New Zealand? Below we will cover some different types of models, their costs – which also includes installation cost.
