Heating without gas
May 4, 2021 9:21 PM   Subscribe

I was all set to get gas ducted heating installed at our new place, but it looks like there's a big push to move away from natural gas fueled appliances where we live. What are our other options?

Details:
* I have a young child who will be crawling and walking soon
* The house is relatively small, mainly looking to heat two bedrooms at night time just to maintain a comfortable temperature (around 20 degrees celcius)
* I'm really anxious about the possibility of a house fire, so want to be confident that whatever we use is at low risk of causing one
* Hoping for something quite energy efficient
posted by kinddieserzeit to Home & Garden (16 answers total) 2 users marked this as a favorite
 
Best would be a split-system reverse-cycle air conditioner.

When these are in heating mode, something like 80% of the heat energy they push into the house is actually being extracted from cold air outside the house by making it even colder; the rest is waste heat from the power directly consumed by the unit itself. This makes a heat pump's running costs about a quarter of those for e.g. a fan heater or an oil column heater, both of which deliberately convert all the electric energy they consume into waste heat .

The only heating technology that lets you pay less for the energy it uses than a heat pump is passive solar.

The hottest component inside a heat pump never gets more than a few degrees warmer than the heated air flowing through it, which makes them very unlikely to set anything on fire. And unlike any form of combustion furnace, gas included, heat pumps make zero carbon monoxide.
posted by flabdablet at 9:40 PM on May 4 [6 favorites]


The only heating technology that lets you pay less for the energy it uses than a heat pump is passive solar.

Agree with everything else you wrote, but this depends on the cost of gas vs electricity where you live. Gas can be very cheap.

It also depends on the ambient temperature. Heat pumps will struggle at less than 0 C outdoors. So climate matters a lot for this question.
posted by mr_roboto at 9:54 PM on May 4 [2 favorites]


Response by poster: Sorry, left out a couple of details:

* Located in Melbourne, Australia. Probably at the very coldest it will get down to 4 degrees celcius at night time.

* We have a split system in the loungeroom and were considering the same for the bedrooms, but I feel that they are much less cost efficient than ducted gas heating. I also feel like the heat is not as pleasant (based on my experience where we currently live)
posted by kinddieserzeit at 10:04 PM on May 4


I feel that they are much less cost efficient than ducted gas heating

They could be, but really only if you're paying way too much for electricity. Have a look at Amber Electric.

I also feel like the heat is not as pleasant

A ducted gas furnace and a split system heat pump do exactly the same thing to the room air that runs through them: they make it warm. That's all they do. If the heat from one of them is distinguishable in any way from that from the other, the only possible reason for that is the way they make the air move within the room.

Most of the cost of a ducted system is going to be in labour and materials for the ductwork; the machine that actually makes the air warm is going to be a relatively minor contributor. So if you like the feel of warm air that seeps slowly into a room through floor registers, you can achieve that with a ducted heat pump and be absolutely sure that the air quality will be the same as what you get from a ducted gas furnace.
posted by flabdablet at 10:52 PM on May 4 [2 favorites]


If the heat from one of them is distinguishable in any way from that from the other, the only possible reason for that is the way they make the air move within the room.

Though there could be a perceptible difference between having a smaller volume of warmer air entering the room and a larger volume of less warm air (with the total amount of energy involved being equal, of course).

As I have no experience living in a house with ducted-air heating I can't tell at what level of that particular difference it may become noticeable.
posted by Stoneshop at 3:25 AM on May 5


What's the state of underfloor electric where you are?
And how much do you like your current floors?
The concept, very simply, is to rig wiring (not hot, like a toaster, but warm, like an electric blanket) under the flooring. House electric warms the floors, which warms your feet and a crawler's tum, and radiates upwards to the whole room.
There's no circulating fan, standing at a nice warm air vent thrill, though.
posted by bartleby at 3:26 AM on May 5 [1 favorite]


Underfloor electric is at least five times as expensive to run as a heat pump, because all it's doing is converting electric energy directly into heat.

The same effect can also be accomplished by running water tubing, rather than electrical resistance heaters, through the subfloor. This is hydronic heating and it has the advantage that the heat source can be anything: solar collectors, heat pumps, gas furnaces or all of the above. It can also be retrofitted to existing structures using radiant wall panels rather than tubes in the slab.
posted by flabdablet at 3:42 AM on May 5 [1 favorite]


there could be a perceptible difference between having a smaller volume of warmer air entering the room and a larger volume of less warm air (with the total amount of energy involved being equal, of course).

The smaller-volume-of-warmer-air option favours stratification, where the warm air rises in a column that doesn't mix much with the bulk of the room air and ends up in pooling near the ceiling. Concentrating hot air in parts of the room where people don't live wastes energy, so the registers in a well designed ducted system are built to diffuse the warm air as it enters the room in such a way as to break up these rising columns and promote rapid mixing. This makes those theoretically perceptible differences very, very small in practice.
posted by flabdablet at 3:52 AM on May 5


Best answer: I also feel like the heat is not as pleasant (based on my experience where we currently live)

I found the reverse cycle unit in our previous home (a rental in Melbourne’s inner north) to be very unpleasant, like a hair dryer blasting hot or cool air on us, no matter the setting. But investing in a higher quality unit makes a huge difference in comfort; a friend’s high-end unit heats the room as comfortably as ducted gas heat.

We ended up going for hydronic heating (we live in a regional town now) and it’s wonderful, but I wish we’d made a different choice for environmental and future financial reasons. Gas won’t always be this cheap, and for good reason...
posted by third word on a random page at 5:10 AM on May 5 [1 favorite]


Though there could be a perceptible difference between having a smaller volume of warmer air entering the room and a larger volume of less warm air (with the total amount of energy involved being equal, of course).

At a previous house we replaced an old gas forced air furnace with an efficient modern heat pump, and it was definitely weird getting used to the change. The gas furnace would blast quite hot air for a relatively short time, whereas the heat pump would run for a long time and would blow air that was warm, not hot. It took longer to make a large temperature change in the house, but it also kept things way more even (and was cheaper).
posted by Dip Flash at 6:30 AM on May 5


Best answer: Just confirming what flabadblet is saying here. I work in a related field - off grid solar, where we have to help people choose heating regularly - and reverse cycle air conditioning is definitely the way to go for you. If you want the gold standard and can afford it, get a Daikin. Otherwise, Mitsubishi Heavy Industries (not Mitsubishi Electric) are good. We got one for our office last year. Worth noting too that you can have reverse cycle ducted if you prefer that to multiple split systems. Talk to an installer who does both and see what suits you best.

Natural gas used to be extremely cheap but we're selling so much overseas now - for hardly anything, alas - that local prices have risen dramatically in recent years. Gas is also good to avoid from a greenhouse emission point of view.

And you can use them for very efficient air conditioning in summer. Something we'll all be needing more of in the future. The proportion of electricity from renewable sources in Victoria is growing fairly quickly, so it will become better and better as time goes by. Add rooftop solar to the house too if you can. It's very cheap now and you should be able to organise to use what you produce so you don't have to worry about any export issues that may come up in the future.
posted by mewsic at 7:07 AM on May 5 [1 favorite]


We ended up going for hydronic heating (we live in a regional town now) and it’s wonderful, but I wish we’d made a different choice for environmental and future financial reasons. Gas won’t always be this cheap, and for good reason...

Hydronic distribution from a central heat pump is available.

You can trade off considerably higher installation costs against slightly lower running costs if you make your heat pump ground sourced instead of air sourced, but in Melbourne's climate there are better ways to spend the money.
posted by flabdablet at 9:03 AM on May 5 [1 favorite]


like a hair dryer blasting hot or cool air on us, no matter the setting

Our indifferently insulated weatherboard house in East Gippsland has a couple of Stirling branded split systems we bought cheap from Aldi, and they don't feel like that at all. They just make it nice and warm or nice and cool inside and they're pretty quiet too.

Running full tilt, each one consumes about 600 watts. On most days for most of the day, I can buy electricity from Amber for well under 25c/kWh. So if we wanted to bake ourselves in the middle of winter or freeze ourselves in the middle of summer, running both of them will usually cost us less than 1.2kW * 25c/kWh = 30c/hr. Because we generally don't run them anywhere near full tilt, it's usually much less than that.

Amber passes on the wholesale market price, so electricity occasionally costs much more than 25c/kWh during peak grid load hours on still days in the height of summer when the shitty old Valley coal plants aren't getting much help from the wind. Amber's phone app tells us up front what the current spot price is, and also offers predictions with reasonably good accuracy for the next 24 hours. So that lets us sidestep peak hour prices by running the coolers as hard as they'll go for the hour before the peak, then turning them off for the duration.

I've never seen our electricity price spike like that in winter, so heating is always cheap.
posted by flabdablet at 9:23 AM on May 5


Response by poster: Thanks everyone. I'm feeling more confident in split systems now, just need to do research to choose the right ones for the rooms.

The description of not so great split systems feeling like a hair dryer is so fitting. But I suspect the issue might be that the system where we currently live isn't quite right for the space.

I'm surprised that panel heaters didn't come up at all though!
posted by kinddieserzeit at 7:59 PM on May 5


I mentioned panel heaters here as a retrofit option for a hydronic setup. They work OK, and if the heat source driving the hydronic loops is a heat pump, are about as economical to run as you'd expect.

Panel heaters built around electric resistance elements, by way of contrast, are as shockingly expensive to run as any other form of electric resistance heating. There is no such thing as an "efficient" resistance heater despite the marketing claims made for fan heaters with ceramic elements, free standing oil-column radiators and so on. Converting a high-quality form of energy like electricity directly into a low-quality form like sub-100°C heat is hugely wasteful compared to running a heat pump with it instead.

The closest you'll ever get to "efficient" electric resistance heating is radiators that warm skin directly by beaming infrared light at it, as opposed to warming the entire space that people occupy.

Panel heaters, including the hydronic types, do this to some extent as well as warming the room air to some extent. The warmth that radiates from a panel heater feels pleasant though not as immediately noticeable as that from a smaller, hotter source like a bathroom radiator, and they're very quiet and don't kick up dust. But they do tend to promote stratification, where a pool of hot air forms under the ceiling and takes forever to extend down to people level unless you stir it in with something like a ceiling fan; so if you're controlling them with a room air thermostat, they will run for longer at a time and therefore waste more energy than something designed for better air mixing in the first place.

The "hair dryer" effect with a split system (or any kind of air-based heating, really) will usually be a result of using one that's too big for the space it's installed in. Ideally a heater fan will move the room air just enough to promote good mixing. A heater designed to do that in a huge room will naturally end up feeling a bit blast furnacey in a small one.
posted by flabdablet at 9:09 PM on May 5


And yes, having a single huge split system installed in the lounge room that's trying to keep the whole house warm by virtue of having a fan in it that would be more at home under the wings of a 747 jumbo jet is the kind of cost-cutting bullshit move that far too many landlords impose on their tenants.

It gets done in order to tick a box on a "habitability" requirement sheet somewhere by providing what's theoretically enough total heating capacity for the dwelling at the lowest feasible installation cost. It's cheap and it feels cheap.
posted by flabdablet at 9:21 PM on May 5


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