Jumping to this topic because, while its just one of the special features that help the house be more energy efficient, it’s been on my mind lately. Also it’s not something you see discussed very much. Energy efficiency in a general way is a given for any building that claims to be even slightly “green”, but the details of heat delivery aren’t talked about too much. That is perhaps because in many cases airconditioning is provided, and that means an air delivery system. Most people want to use the central air to provide the heating as well as the cooling. For one thing, it’s cheaper that way – at least for installation or first cost. An air-based system is also simpler if you are using ground-source heat pumps, what is usually now known in the US as geothermal. (That’s not really the correct use of the term, true geothermal uses natural heat from volcanic sources ). Heat pumps using ground water are more efficient than traditional electric cooling and, especially, heating – the overall equation compared to all methods is not quite so simple however and we’ll maybe talk about that later.
Another reason that different types of heating are not discussed much is because, for water-based systems, radiant floor heating has become a huge preference in Green building. It provides an even background heat, it is incorporated into the fabric of the building, and it can use very efficeint heating boilers. Boilers are claimed to be more efficient the lower the temperature of the water provided, and radiant floors use a very moderate temperature. After all, you would not want to fry your tootsies now would you?
One of the big advantages of water-based heating as opposed to hot air, is that it allows more control of the spaces. It is easy to ‘zone’ part of a building, to have a thermostat that automatically controls only that area – for example the bedrooms. That is much harder with air systems, unless there are multiple central AC units. This ability to control the heat and use only what is called for, is a major route to greater efficiency and lower fuel use. Underfloor, or radiant floor, heating, can be zoned with separate thermostats. However it is usually not controlled on a room by room basis. Also, and this is a major drawback in my opinion, the heat cannot be rapidly controlled. It takes time, maybe several hours, for the the structure to heat up and the low heat to warm a whole area. So if you leave the house during the day, or want to turn the thermostat down at night, a long warming-up period must be allowed for. And while the strucutre is cooling, all that built up heat is slowly leaking away. The inside temperature is higher than it has to be, and the whole house is therefore losing heat at a higher rate.
Radiators give the best heat control, and I think the highest potential efficiency and lowest fuel use. Not only have I zoned the house so that there are separate thermostats for upstairs – the bedrooms – and the downstairs living spaces. Each radiator also has a thermostatic valve so that its temperature can be set higher or lower. Thus for example if my daughter leaves home for a while – as one of them has right now – that room can easily have its temperature turned down. If I am motivated and energetic, I can even fine tune the house during the day, turning a particular space up or down as we use it. The radiators respond very fast, so in half an hour or less a space can be brought up to its desired temperature. These are pressed steel panels, not the heavy ribbed cast iron creations that perhaps come to mind with the word “radiator”. They are made in Europe – mine are from the UK and obtained via an agent in Canada. This brand is not expensive. I could have used the more common American baseboard solution. That’s fine, but it hampers the placing of furniture. Radiator panels are more compact.
Another big advantage of the panels is that they allow a lower temperature setting to be used. This is because the body senses radiant energy through the skin, and adds this to the general bodily sensation of warmth. The panel radiators are sitting on the wall in clear view, and they have a hot – but not too hot to touch -surface. Since, in addition, there is no moving air to cool the skin, an appreciably lower temperature – and less energy use – is accceptable than with hot air systems. I was surprised to find that I can be as comfortable with the thermostat at 66 deg as I was in my old place, which had hot air, when the thermostat said 70 degrees. Well insulated walls with a higher interior surface temperature probably help too, but I think it is mainly the heating system.
It is a great system and, once again, the most efficient means there is of keeping a house warm. As far as I know.