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Radiator sizing after 6" celotex insulation

Discussion in 'Plumbing and Central Heating' started by bazmdiy, 15 Sep 2013.

  1. bazmdiy

    bazmdiy

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    Hi All,

    Hope someone can reassure me with radiator sizing! Sorry for the amount of detail but I dont know how else to present the problem...

    As a retirement project I have built an extension part of which is a kitchen 6x6x2.4m.

    Construction is timber frame with fermacell "plasterboards" externally and wood cladding (3 external walls facing East West South). Internally fermacell plus pine wainscoting.

    Floor is pine T&G over 225 joists over 450mm cavity to concrete site base.

    Insulation in walls, floor and pitched roof is 150mm Celotex. Ceiling also has 100m knauf "earthwool" (had some spare!).

    Windows are wooden double glazed 4-14-4 glazing unit. Glass about 3.5sqm.

    Now I am at the point where I need to buy radiators...

    Looking at all the Heat Calculation tools I get answers from 2 to 4Kw heat requirement. However, I feel that they do not reflect the amount of insulation I have. If I calculate (I'm no expert) the heat loss (using r-value u-values for celotex wood etc) I get a ridiculous 600watt heat loss.

    I'm just too nervous to install a 1kw (3000BTU) of heating.

    Anybody gone through a similar situation or have experience of heat installation in well insulated rooms?

    Many Thanks
     
  2. Agile

    Agile

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    The simple answer is that the 600w is probably correct but may have over looked some cooling aspects and air changes.

    Most would fit about 2-3 kW as a minimum and expect it to be oversized which will give the advantage of faster warm up and enable a lower flow temperature to improve boiler efficiency.

    Tony
     
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  4. dcawkwell

    dcawkwell

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    Even a 1 to 1.5kw radiator will take little space up.
    Go for something large and will heat the room up quickly.
    The thermostatic valve will then take care of the temperature.
     
  5. bazmdiy

    bazmdiy

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    Hi - Thanks for response. I will go for 3 rads = 2.2Kw. If that isn't enough I can fire up the 8Kw Clearview wood burner!
     
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