Most efficient way to heat my home?

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Most efficient way to heat my home?

Postby simoga13 » Sat Mar 07, 2015 12:45 pm

We live in an old double brick building that we have renovated extensively to make it our home (it was an old church/hall). We've double insulated where we've been able to but the place is still really cold in winter. I've put up with it just to save money but I really don't cope with being cold - in fact, I'm already panicking about the upcoming cold season!

The house is about 210m2 with the living room being about 64m2. The ceiling heights range from 3 - 4m (skillion) and we have about 20m2 of windows facing directly north (distributed across living and bedroom areas). We are on a beautiful old timber floor that probably doesn't help because it can't hold heat.

We have a 2kw solar system on the roof that pays for all of our current electricity costs (we are on the 60c feed in tariff).

I haven't been able to get any good advice regarding this issue and just wonder what others are doing to stay warm and beat the cost?

I need some ideas for efficiently heating our home. I'm not sure whether to just source an efficient electric heater, add some more panels to our roof or look at a solar powered heating system.
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Re: Most efficient way to heat my home?

Postby Gordon-Loomberah » Sat Mar 07, 2015 1:58 pm

Welcome to the Energy Matters Forums Simoga13 :)

I'd start with underfloor insulation, cold floors make for cold feet, and can make you feel colder than you might otherwise, if your feet weren't feeling like ice blocks.

I'm supplying some of my winter heating with a 78 evacuated tube system and hydronics radiator, which I blow air through, and it costs nothing to run :) The addition of a heat pump would mean it could supply all my winter heating, but that is way beyond my budget limitations.
New efficient heat pumps will produce in the order of 4 times the heat energy used by the compressor, so represent ~400% efficiency, vs 100% for straight resistive type electric heaters. Reverse cycle air conditioners can now do up to 500-600% heating efficiency (and almost as good for cooling), for small units in the order of 2-2.5kW output, and are well worth considering too.
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Re: Most efficient way to heat my home?

Postby simoga13 » Sun Mar 08, 2015 1:34 pm

Thanks for your reply Gordon-Loomberah.

You've given me some good ideas and, yes, I've decided to start with underfloor insulation. We do have an evacuated tube hot water system and I believe there is some scope to use that to heat the house so will be investigating that further. Did you set up your own hydronic heating? I would be interested to learn more about this option.

Thanks again!

:D
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Re: Most efficient way to heat my home?

Postby Gordon-Loomberah » Sun Mar 08, 2015 2:42 pm

Yes, I did all my own hot and cold water plumbing here for house water and hydronics, perfectly legal when not connected to a town water supply. It's just a simple circulating pump between evac tube heated reservoir and a radiator in the house, manually controlled.
I did buy a thermostat controller for it, but decided it wasn't really necessary, as I don't need a constant thermostatically controlled temperature, so will use that for something else. More or less clothes are the best thermostat control!
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Re: Most efficient way to heat my home?

Postby Smurf1976 » Sun Mar 08, 2015 4:31 pm

Happy to help but just one question first - where is the location (city / town or at least what state)?

Energy prices vary hugely between regions of Australia, hence needing to know the location. :D
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Re: Most efficient way to heat my home?

Postby simoga13 » Sun Mar 08, 2015 8:19 pm

Hi Smurf1976.

We are located in West Wallsend, a suburb of Lake Macquarie, Newcastle NSW.

:)
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Re: Most efficient way to heat my home?

Postby Cherokee Solar » Mon Mar 09, 2015 9:03 am

simoga13 wrote:We live in an old double brick building


There are quite a few double brick buildings around these parts of Victoria and they are always cold. It takes a lot of energy to heat up that huge thermal mass. Being a church hall do you have an internal second story? Over winter a lot of hot air rises so it will actually be warmer nearer to the ceiling?

A neighbour has a double brick house and has a massive boiler to run hydronic heaters from. It uses a lot of wood and so does not get used.

I have an 8kW wet back on the back of my wood heater chamber and that can realistically run 3 hydronic radiators - not a lot more. Solar hot water keeps the system topped up with heat as well. I have a wood lot so can burn as much timber as I can be bothered seasoning - but timber is expensive.

The walls in your house will radiate the cold at you over winter and you will be unable to adequately heat them. Make sure they get direct sunlight over winter and shade over summer and that may help a lot.

For a long term solution, cover the brick work with a timber stud and plaster wall and pack that with insulation. A 90mm wall will provide room for R1.5 batts. A 200mm wall 90mm + 20mm space + 90mm will allow you to pack in R3.5 batts - which is what I've done here and the house is always warm in winter and cool in summer.

Under floor insulation is a great idea too which I do here too. Add glass fibre batts under the floor and hold them against the floor boards using steel wire. Easy.
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Re: Most efficient way to heat my home?

Postby Smurf1976 » Mon Mar 09, 2015 8:31 pm

A structure like that is going to be difficult to heat no matter how you do it.

Maximise solar gain, insulate where possible etc as others have said. This will help keep the heating costs down. Also active solar systems to help reduce the need for, and cost of, other heating as others have said.

Beyond that, for some sort of added heat, the sensible options are either reverse cycle air-conditioning or a wood fire (not sure what wood costs where you are though?). Also a ceiling fan will help push hot air down to where you need it assuming the ceilings are high.

Wood versus air-con?

To work out the cost of heat from wood, take the price of wood per tonne (dry) and divide that by 2700. That will give you an approximate cost per kilowatt hour of heat actually put into the room by a slow combustion wood heater. Eg $100 per tonne / 2700 = 3.7 cents / kWh. This is based on dry firewood and a real world heater efficiency of 60% which is typical.

For the reverse cycle air conditioner, take the electricity price in cents per kWh and divide that by the COP (co-efficient of performance) of the unit which will be somewhere around 4. Eg electricity at 14.9 cents per kWh / 4 = 3.7 cents per kWh.

Gas? If you have natural gas (mains gas not bottled) available then to compare that with the other options, take the price in cents per MJ and multiply by 4.5 (or if gas in your area is sold by the kWh then multiply that figure by 1.25). Eg gas at 11.26 cents per kWh (or 3.12 cents per MJ) multiplied by 1.25 (or multiplied by 4.5) = 14.1 cents per kWh of heat delivered. This assumes an 80% appliance efficiency which is typical.

Note that those prices are for Tasmania so you'll need to check your actual electricity and wood costs. I suspect they'll be somewhat higher in your location. Forget bottled gas and electric resistive heaters - in your situation they'll send you broke in no time.

Wood pellets are another option. I haven't mentioned cost since it varies a lot based on location but you'll get about 4.2 kWh per kilogram of pellets. So cost per kg divided by 4.2 gives cost in kWh. Note - wood pellets are for use in wood pellet heaters, you don't burn them in a normal fireplace or wood heater. They're moderately common in some places, eg Tas and NZ, but unheard of in others. Not sure if it's an option where you are.

Another option, there are also heaters that run on wheat. Yes wheat! It's cheap stuff if you're in the right location and buy in bulk, not really an option if you're in the city however. It's a legit technology, wheat can indeed be burnt as a heating fuel and it burns quite cleanly, and such heaters are commercially manufactured.

Pellet and wheat heaters both blow hot air out and tend to have little if any radiant heat output despite there being a visible flame.

The other option is to not heat the air at all and just heat the people via radiant heating. There's quite a few options there:

Wood heaters produce radiant heat, especially if you buy one designed to maximise this aspect of it's performance (some are designed to maximise the output of hot air).

Gas radiant heaters are another option, particularly if mains natural gas is available.

Lots of electric options although costs will be higher than with wood or gas (COP of any electric resistive heater is 1, not 4 as with the air-conditioner, so cost per unit if heat is far higher although you'll be using less of it by only heating people and objects not the air).

First step - insulation etc.

Second step - decide whether you want to heat the whole place, or just use radiant heating to warm people and objects only. Heating the air will need a lot more energy, but avoids the "freezing cold as soon as you're not in front of the heater" problem.

Third step - which fuel? Electric? Gas? Wood?

Fourth step - worry about the details of the actual heating system.
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Re: Most efficient way to heat my home?

Postby simoga13 » Tue Mar 17, 2015 8:27 pm

Thanks so much Smurf1976. The information you have provided is terrific!

I think I'm leaning towards wood at the moment but I have lots of research to do.

Thanks again.

:D
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Re: Most efficient way to heat my home?

Postby Smurf1976 » Tue Mar 17, 2015 10:58 pm

Just an addition to my previous post, in that all prices should be in cents.

Eg for wood you take the price per tonne (eg $100) which is 10,000 cents per tonne and divide that by 2700 to get price per kWh which, in this example, will be 3.7 cents.
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