I would appreciate your advice on electric radiators. I am in the process of retrofitting my home. Over the last few years I have had solar panels fitted, upgraded the insulation, and will have triple-glazed windows fitted soon. The next stage is changing from oil-fired heating to a heat pump; however, I am increasingly hearing about electric radiators as an alternative heating source. I have a detached two-storey four-bedroom house built in 1961, which had a Ber of C2 prior to the above work. Can you advise on whether they are suitable for a house as opposed to a smaller apartment, and what are the pros and cons associated with them?
As we all transition from fossil fuels to renewable energy, the use of electricity for heating our homes is increasing. However, improving the fabric and energy-efficiency of your house is the first step – unless you can afford to be profligate with a surplus of energy from your PV array which, on a standard semidetached home, is unlikely, even with battery back-up.
Improving the fabric of the building will mean that not only will you require less energy for heating, but the home will be more comfortable, with spin-off benefits for your health and the building’s health if carried out correctly.
Direct electrical heating systems, no matter how efficient the sales brochure might suggest, are wasteful, since they can only convert the incoming amount of electrical energy to the same amount of heat energy if they could be 100 per cent efficient, which, of course, they are not, with the best struggling to reach 90 per cent efficiency.
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Most electricity is still derived from fossil fuels, and that proportion is rapidly reducing, with new renewable generation from wind turbines and PV arrays coming online. Some years ago the Rocky Mountain Institute carried out a study which found that fossil fuel generation, at best, only provides – to the point of end-use – some 10-15 per cent of the available energy in the source fuel. This is due to extraction, generation and distribution losses. That is quite a staggering statistic, and illustrates why we need to wean ourselves off these historical fuel sources, as well as the inefficient direct electrical devices such as the panel radiators you are suggesting.
Damp air from bathrooms and kitchens has the advantage of higher quality energy that can be transferred by entropy, the latent energy in wet air
By using clean electrical energy to recover heat energy from the environment, we can begin to reverse the negative efficiencies noted above. The Sustainable Energy Authority of Ireland (SEAI) promotes the use of air-to-water heat pumps, as these suit most types of property and have efficiencies of more than four to one, meaning that you get four units of heat for every one unit of electricity used. They do this by compressing larger volumes of low-grade energy in the air to smaller volumes of higher grade energy in water, which can then be circulated around your home, usually by underfloor pipework. Water-to-water heat pumps are more efficient again but do require large areas of ground to bury pipes or a ground source well drilled to the aquifer, and are not suitable for most smaller properties.
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Another option is “exhaust air heat pumps”. These recycle the heat energy already or incrementally induced into the volume of air in the house by using a small heat pump to transfer and augment energy in exhaust air into the incoming fresh air required for healthy living. Damp air from bathrooms and kitchens has the advantage of higher quality energy that can be transferred by entropy, the latent energy in wet air.
Such systems can be very efficient in a well-sealed and insulated property and can bring the energy demand within the capacity of a PV and battery backup system, meaning that for most of the year, heating and hot water can be almost free. This technology is well understood but there are few manufacturers as yet who are providing these units, noting that double ducted systems are again more efficient than single duct types. Search the internet for “exhaust air heat pumps”, ask the SEAI, or talk to your local chartered building surveyor who will be able to advise you on the best ways to reduce your energy requirements.
Fergus Merriman is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland
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