On Mon, 5 Jan 2004 01:51:08 -0000, "John Stumbles"
] wrote:




For the floor, you have to take into account the perimeter/area factor

if it is a ground floor so there are tables of numbers rather than
single figures.

The BS just has a couple of fudge factors for different floor areas of
solid
floors (reflected in Barlo's 110sqm, 50sqm and Terraced house options).

For a boarded floor (non T&G), I suppose one should consider the
draught proofing effect of the carpet as well, but that is pretty hard
to assess.....

Well it's all pretty approximate (unless you get into the sort of detail in
Part L1) so I'm surprised they haven't at least included some average-ish
sort of figures e.g. cheap'n'nasty rubber-backed | deluxe thick pile on
cushioned underlay.

I see Barlo's help file also refers to the BS and shows the same table (as
also in the Barlo) but then goes on to describe the P/A method. However
their calcs seem to just use the BS table - no P/A.

I suppose for uninsulated suspended floors the heat loss through the floor
vastly exceeds the loss round the peripheries so you can in practice pretty
much ignore P/A - ?

This is basically what TNP said. For a suspended block floor, you
could effectively treat it as a wall on the basis that the outside
temperature is across the entire underside. This would give a worse
heat loss calculation than using the P/A factor, but for a heating
design will mean that you err on the side of more heat provision.

For timber floors, possibly the U values published assume no P/A
anyway.

Obviously it's a different situation if you are trying to demonstrate
that a new house construction falls within energy consumption
guidelines as opposed to a heating design for an existing property
where you want to make sure that there is adequate heat provisioning.
Generally on a property without cavity insulation, the largest heat
losses tend to be through the walls anyway, and the floors about third
on the pecking order.

Another factor is how does one treat party walls? Should it be to
assume that next door has no heating and that therefore the party wall
is effectively external, or that next door has heating and that
therefore there is a net zero transfer - or something in between?
If you consider a typical terraced property, they are often three
times as deep as wide, so the party wall areas are substantial in
comparison to the external.




..andy

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