De-mystifying heating systems

By now, I’m sure you’ve heard or seen numerous ads touting some miracle radiant heater or special pellet stove that will “slash your heating bill by 50%!”…or something similar. Lots of claims about how efficient the heating system is and how much money it will save you.

The plain truth is that how much money, and energy, any heating system will use is mostly dependent on the building itself and how efficient it is, or isn’t (see my previous post on the building envelope). Try putting your car heater on full blast with your windows down on a day like today (-30 wind chills) and you get the picture – it doesn’t matter how much heat the system puts out if you can’t keep the heat in.

For the purposes of this discussion, let’s assume we start with building you a very efficient home. The choice of heating system could be oil, natural gas, wood/pellet, electric, solar-assisted, air-source heat pump or geothermal heat pump, or perhaps a combination. In all cases, passive-solar design features should be incorporated into the house as much as possible to harvest this free heat. We’ll also assume you’re building a house that is, say, 2500-3000sf in total (if we’re truly searching for efficiencies, smaller homes should be considered).

Let’s dispense with oil right out of the gate. Personally, I won’t install it in a home; it has too much environmental disaster potential (anyone remember a recent tank leaking a large amount of oil into a Bedford lake??) and if you’re watching global prices, it’s likely to become extremely expensive in the coming years. Plus, the CO2 emissions from extracting, processing, transporting and burning the oil are huge. Natural gas is far cleaner than oil, is more efficient and does not require a tank. It is, however, still a petroleum product that has to be extracted, processed and shipped to be burned…and is limited in its availability.

Wood and wood pellets are less common as a main heating system, however can be used in a main furnace in conjunction with the forced-air circulation system that is now required in all new construction. There’s a lot more work involved in splitting (if you choose to), stacking, storing, moving and cleaning up after the wood (or pellets)…and you have to be there every day to keep the furnace stoked, but for those who prefer to do that, and have access to the wood (it is a renewable resource), then it can be a viable option.

Electric heat, via a boiler for radiant heat or from baseboards, was commonly used in the past, however is waning in use due to its percieved costs and the fact that if it is your main heat source, you no longer qualify for most of the rebate programs out there for efficient housing. Even though we have an ongoing shift to increased renewable electricity in Nova Scotia, I still agree that electricity should not be the primary heat source.

All of the above sources suffer from one common drawback. They cannot ever achieve above 100% efficiency, and by that I mean produce more than 1 unit of energy for every unit of energy you feed into the system. You may get as high as 90-95% at best, yet it is still always more energy in than out. Remember that every system is still drawing electric power to run fans, burners and any associated equipment…and the fossil fuels (with perhaps the exception of wood) caused more energy to be burned off getting to you from start to finish than they possess when you finally get to burn them. That part is scary.

That leaves us with what I believe to be the best options; solar, air-source heat pumps and geothermal heat pumps. Solar panels can be used for pre-heating domestic hot water, for pre-heating air, and for providing electricity. Relying on solar for most of your heat is possible with a very good design, building orientation and high-performance envelope. Be sure you have some expert advice as this is not for amateurs. The beauty of solar is that once you have the system in place, you’re not “buying” energy from any source to provide heat, so you can achieve more than 100% efficiency (you still need electricity to run fans, etc.). As long as the sun is there, the heat will be there.

Heat pumps have become very popular, and for good reason. Even though you need electricity to run the compressor and fans, it actually produces more energy that it uses – from 300% to as much as 520% efficiency, with the geothermal systems being on the higher end. Air source heat pumps provide both heating and cooling (you simply reverse the system to cool in summer – it works on the same principle as your refrigerator) so you get both features with one system – none of the other systems can do this. The real gem is the geothermal heat pump systems; they provide not only heating and cooling (at a higher efficiency than the air-source units), but also pre-heat your domestic hot water so less energy is needed to bring it up to the temperature you want at your taps and shower. Even better is that during summer with the system is in cooling mode, all the heat it extracts from the air inside the home gets transferred into the hot water pre-heat tank so that very little energy is needed to use the water at your taps/showers. It’s a real all-in-one system that has the free energy of the earth available 24/7 regardless of weather conditions, time of day or time of year.

Of course cost is a consideration. Of the systems I choose as the best, the air-source heat pump would be the lesser priced to install with the solar and geothermal systems being a bit more, though also deliver the best bang-for-the-buck in the long run. All are very efficient and you can’t really go wrong with any of them. Actually, let’s not use the term “cost” and call it “investment“, since that’s exactly what it is…an investment in your home that produces enormous savings in purchased energy. And that helps our communities stay cleaner as well as lower your costs and add significant value to your home. Ten years from now when someone is looking to buy a house, they will be looking most favourably at the ones that use the least energy. Want yours to be at the top of the list?

Remember that when you build a high-performance envelope around the house, and incorporate good design elements, your system really does not have to work very hard to keep you warm, or cool. So invest in good construction so that your operating costs are kept very low, and stable, and see both the savings grow over time as well as your re-sale value.

As always, please do provide your questions and comments.

Andrew W. Alcorn, CET
Innova Builders, Inc.
www.innovabuilders.ca
andrew@innovabuilders.ca

Andrew is a member of the Halifax Chamber of Commerce Energy Advisory Group
and the Canada Green Building Council (Atlantic Chapter) Residential Committee

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One response to this post.

  1. Posted by Susann Hudson on July 31, 2012 at 4:35 pm

    Hi
    I have an older 100 yr old house in Halifax. The oil furnace is too old now and it’s time to replace the oil tank. I’m looking at getting rid of oil and putting in a heat pump and air to air fan coil.
    I have one quote and info on systems made by Payne. Curious to know if you have anyone you can recommend for another quote on installing such a system. Or do you do this – or only work on new construction?

    I also need to install a different source of heating my domestic hot water and need to find out what would be the best and most efficient system.

    I would love to know your thoughts on any of the above as this is a large investment for me on a single income.

    Susann Hudson

    Reply

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