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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorjongarrett
    • CommentTimeJul 11th 2007
    Suppliers of skirting board heating systems are claiming some impressive savings in running costs over traditional radiators. Does anybody know if such savings are likley? Am I right in thinking that savings are achieved by getting away with setting a lower room temperature ie 19 degrees instead of 21oC?
    • CommentAuthortony
    • CommentTimeJul 11th 2007
    19 instead of 21 will save 10%

    Heating the coldest part of the room maximises heat losses so is bound to cost more.
    If a room needs a certain amount of heat, it doesn't make any difference how it is delivered, everything else being equal.

    Also, a blanket statement like "19 instead of 21 will save 10%" is also misleading. It depends what the design conditions are: if the
    outside design temperature is -20C (like here in Montreal) the difference between 19 and 21 is more like 5% - but things like airleakage also are a complicating factor. The only way to really know what the savings are by turning down the thermostat are to run some heat loss calculations. Heating system cycle times are also affected by setpoint temperature and it could be that
    lowering the thermostat causes short cycling and therefore less efficient operation of the heating device - which may negate any
    potential savings that were envisaged. This is especially true where boilers are typically greatly oversized so rarely run at their
    peak efficiency.

    Paul in Montreal.
    • CommentAuthorfuncrusher
    • CommentTimeJul 13th 2007
    Tony: There is more to 'heating the coldest part of the room' than it appears. The coldest part is usually the part with the greatest heat losses. The most efficient way to achieve room-wide comfort is to heat this region. If you position heat input elsewhere, you over-heat the other areas of the room in order to achieve target comfort in the coldest. In essence, heating systems should replace heat losses, not convey heat to zones whereit is unnecessary.
    • CommentAuthortony
    • CommentTimeJul 13th 2007
    Fun, I sort of agree but that is for comfort. For energy saving and reducing heat losses then the coldest part of the room is the very worst place to site a heat source. Would you put a radiator on top of the window sill? Certainly skirting heating cannot reasonably claim to save energy in my way of looking at it.

    ( PS - do you fancy doing me a consultation for a proposed new house?)
    • CommentTimeJul 16th 2007

    You seem to be suggesting that there are two different approaches for choosing the ideal position for the heat source, either for comfort or for energy saving.

    However, as far as I am aware, the only reason for having heating in the first place is for comfort. Therefore assuming you wish to use the whole room then you will want a comfortable temperature throughout. Therefore I agree entirely with Funcrusher's logic for locating the heat source in the coldest area.

    If you have a drafty cold spot in a room then you might be tempted to turn up the thermostat to a higher level than you would if you had sited the heat source to eliminate drafts and cold spots e.g. by putting a radiator under a single glazed, sash window. This is the logic I've used when deciding on radiator positions where you have single glazed windows in a room, which have to be retained in a conservation area.
    • CommentAuthortony
    • CommentTimeJul 16th 2007
    Re heat losses and energy saving the idea of putting the heat source at the coldest place means that more heat is going to be lost than would have been it had been somewhere else this is because in order to heat the room the heat source has to be warmer than the rest of the room. Therefore more heat will be lost compared to having that part of the room at the minimum comfortable temperature.
    • CommentTimeJul 17th 2007
    I understand your thinking Tony and it stands to reason that the higher the temperature adjacent to the window, the greater the losses through that window will be. However I still think the best approach is to site the heat source to give the most comfortable distribution of heat (e.g. under the window) and then tackle any heat loss problems separately, such as by reducing draughts, installing secondary/double glazing etc.

    I'm currently sat in a single glazed office next to the window, which is fine in the summer. However, if our radiators were only positioned on the opposite wall (some 9 or 10m away) , then in winter I don't think it would actually be possible to make me warm enough next to the window without baking the people on the other side of the office next to the radiators.

    My office is a fairly extreme example, and in a newer, highly insulated building with better airtightness the location becomes far less important as losses are much lower and the temperature differences much less.
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