The lowdown on heat pump settings that will save power
It’s logical when you think about it. Heat rises, so for wallmounted heat pumps to be most effective, their vents should point downwards. Joanna Davis has a lesson in warming her house.
It turns out I’ve been using my heat pump all wrong – and maybe so have you. It’s a basic matter of physics: hot air rises. So to get the most out of my wall-mounted unit, I need to have the vents pointing down, towards the floor.
But my work-from-home desk is directly underneath the heat pump and having air, even warm air, blowing on you is unpleasant.
So I’ve had the vents pointing straight out, directing air well above my head, since always. I need to move my desk, says Richard Popenhagen, eco design adviser for Nelson City Council.
Other heat pump settings he often sees which aren’t recommended? Not setting the mode to ‘‘heat’’, setting the temperature above 22C, and the fan setting not left on auto (where the unit operates most efficiently).
Moving the vents will help my heat pump be more effective. At the moment, it seems like it’s just not capable of doing its job, warming our main living area, and I often use electric heaters, too.
Popenhagen has plenty of other ideas to help with that. He’s giving me a video call consult on how I can heat my 1945-built, single-glazed Nelson home.
Seven councils nationally provide free services like Popenhagen’s to their ratepayers. The advice focuses on your home’s thermal performance, moisture management, and heating.
If people have mastered those, Popenhagen also has advice on solar power, rainwater harvesting and grey water recycling. ‘‘Those are good things to do, but they don’t keep you warm in winter, they don’t keep you healthy,’’ he says.
He reminds me of the World Health Organisation’s advice that homes should be a minimum of 18C, higher if young children, elderly people or unwell people are home. ‘‘We know most New Zealand houses are nowhere near that,’’ he says.
It’s regularly 13C in my son’s bedroom. I’ve been monitoring it off and on for a while now. ‘‘Health studies show if temperatures drop below 16 degrees it affects respiratory function,’’ he says. ‘‘Winter illness, hospitalisations and deaths spike in winter in New Zealand, more than other OECD countries.’’
Oh dear.
We go through my house’s current performance. The fact it has ceiling insulation is great. ‘‘That’s usually the biggest heat loss, and the easiest thing to improve,’’ he says. ‘‘You can’t have too much. The more the better.’’ Another layer would help though, in my house.
Windows are the ‘‘big problem child’’, he says. While double-glazing would be best, he acknowledges it’s ‘‘such a challenge, cost-wise’’. But he has a few simple, cheaper options.
The curtains in my dining room are ‘‘a perfect example of a curtain that will do practically nothing for you’’, in terms of heat loss, he says. They’re made from a single-layered, thermal fabric that extends to the window sill.
Curtains that don’t go to the floor create a chimney effect and drop cold air into the room all night, he says. ‘‘For curtains to be effective, they need to come down and sit hard on the floor,’’ he says.
The so-called ‘‘thermal’’ fabrics they’re made from is a misnomer. ‘‘Branz and Consumer find they are pretty useless. They were never invented for thermal performance, but to stop curtains rotting in the sun.’’
The best curtains have a separate lining, and ideally are made from a fabric with another layer – an inter-liner of a ‘‘fleecy micro quilt’’. People on a budget can improvise by making an extra layer by pinning on polar fleece, or cheap acrylic blankets.
Moisture is the next problem to be tackled. Wet air takes a lot more energy to dry out and heat.
Do you use your kitchen’s extractor fan?
I confess I hardly ever do, because it sounds like a jet plane taking off. Popenhagen has heard this before.
‘‘So many people tell me, ‘We don’t use it or only occasionally.’ When I ask why, invariably the answer they give me is: ‘It’s too noisy.’’’
But cooking can add up to 3L of moisture inside your home, he says. ‘‘Although you’re making it in your kitchen, it equalises quickly throughout the home.’’
If you don’t have a fan, just using pot lids can also significantly reduce moisture in the air.
Do you dry clothes inside the home?
Guilty again. Just one load can put 5 litres of water in the air, Popenhagen says. Ideally, we’d dry clothes outside. If not, the best option is to use a clothes dryer, vented to the outdoors. ‘‘If you’re just opening a window, shut the door between the laundry and the rest of the house.’’
Is the bathroom ventilation adequate?
The extractor fan should have a minimum diameter of 15cm, he says, and a minimum airflow of 50 litres per second.
‘‘We want to remove the moisture fast,’’ he says, adding that there are a couple of tricks. One is to also crack open a window, to allow air to come in to replace the air being extracted.
The other is to always shut the bathroom door. People often don’t do that if the bathroom is an ensuite, he says.
‘‘Shower domes are great. They’re a micro version of keeping the bathroom door shut. Keep the door to the shower shut after you’re out. Squeegee the shower off after it’s cooled down.’’
Should we open windows to air out bedrooms?
‘‘This is the other thing that a lot of people get wrong,’’ Popenhagen says. ‘‘We do need to ventilate our houses to bring air inside because the outside air is usually drier. But, you should do it in the warmest part of the day, just after lunch.’’
I can manage that because I work from home. For people who are out most of the day, Popenhagen advises a quick flush out of 10 to 15 minutes before they leave in the morning.
More advice on dealing with moisture and condensation, and on home heating and insulation is available at ecodesignadvisor.org.nz, as is design advice for new builds.