Will Dean wrote:

"Andy Hall" wrote in message
...


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?


The HVCA guide reckons you should treat adjacent property as unheated, but
then half the U value for the wall because the adjacent property probably
will be heated.

I think this rather bizarre alternative to using the real U value and
changing the temperature drop is just because that's the way their example
worksheet does things. (It does a single temperature drop multiplcation at
the end of everything.)


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.


Having just done a complete heat-loss for my house, and realised that the
fabric loss was about 55% of the total, with the vent loss being 45%, it
does seem that there's a slightly misplaced obsession with exact 'U' values
when vent rates are basically picked from a list of 1,1.5,2 or 3.

For example, disregarding all the windows (i.e. treating them as wall) in
this house makes about 5% difference to the total loss. As you're probably
going to be adding 10-20% of hand-wavy 'distribution loss' and 'intermittent
heating factors' at the end of the whole process, I did finish up wondering
why I'd bothered measuring everything so carefully.

JOOI, what do other people who've done detailed heat-loss calcs come up with
for vent vs. fabric loss?



I forget, but at building reg sort of U values, the vent loss is getting
close to dominating IIRC.


Will