On Mon, 5 Jan 2004 20:45:48 -0000, "John Stumbles"
] wrote:



I've assumed 220mm brick + 13mm plaster, U=2.0 (from BS5449 - I see Myson
use a figure of 1.8 for this construction).

I would expect the extension to have a fairly large heat loss because
of the external wall area.

(The extension shares a party wall with next door.)
I make its loss though external walls 712W. (Actually that includes a new 2m
extension to the ground floor at the back, which has insulated cavity
walls.)

OK, so that takes out a fair chunk of outside wall area down to a much
lower heat loss.



How have you treated the party walls?

I've assumed next door temperatures of 15 downstairs, 10 upstairs (more
pessimistic than the usual 18 up and down, I know).

Seems reasonably conservative.



So for example my big main room (through lounge) has a party wall area of 2
(party walls) * 7.4m (width) * 2.4m (height) = 35.52m^2, and therefore a
heat loss of 35.52 * 2.0 (U value) * 6 (21C - 15C temp diff) = 426 Watts


In the very first house that we had where I installed heating, it was
also a terrace, although quite a bit larger than this one - probably
about 1.5m wider and quite a bit deeper, with an original 2 storey
extension. There was also a fourth bedroom in the loft - basically
in the apex area of the main part of the house.

The design was done when it was customary to allow 3kW for the HW
cylinder. I can remember that the total heat load, worst case, with
10% allowance came to 20kW and I used a legendary Potterton Netaheat
16-22 wound up to full power. This would have meant that the house
peak requirement was probably around 14kW. I did design assuming no
heating in neighbouring properties though.



..andy

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