"Hugo Nebula" wrote in message
...
[Default] On Thu, 16 Aug 2012 08:59:31 +0100, a certain chimpanzee,
"David WE Roberts" , randomly hit the keyboard
and wrote:

We need SAP calculations for our extension - I assume because bi-folds are
over 25% of new floor area.

Can anyone recommend an online firm to do these?

Presumably you been asked to supply calculations to show that your
proposed extension performs no worse than a notional extension by your
Building Control section. This is shorthand for, "there's no way your
extension will comply with that much glazing, but I can't come out and
say it, so you have to get your own calcs to convince yourself".

If so, what they're looking for is the total additional heat loss from
an excess of glazing in Watts/degree C. You can then try and offset
this heat loss from elsewhere within the extension, or if not
possible, elsewhere in the building (e.g., additional loft insulation,
more efficient boiler, etc.).

If you know how to work out U-values (or your architect does), you
shouldn't need to go to the expense of getting two SAPs ('cos that's
what you'd need - one for the house + notional extension, & one for
the house with improvements + proposed extension).


It is a standard 'jobs for the boy/girls' thing.
Allegedly the person producing the report has to have a SAP accreditation
specific to the type of building (commercial or residential).
If the glazing is more than 25% of the new floor area BC want a SAP report -
as you say this will be a list of improvements elswhere in the building to
justify the amount of glass, plus a thermal gain calculation to show that in
fact with that much glass the house will be a sauna on a sunny day.

Leaving aside the issue of accreditation (which sounds like a Part P kind of
thing), I just don't have time to learn how to do the detailed calculations
at the moment.
I suspect the BCO doesn't either, and relies on the report from an
accredited SAP person.
Having the architect do it would not be free, anyway, and he would just
offload it to someone with the accreditation and the software package and
pass the charge on at cost plus.

Standard charge seems to be £150+VAT.
Our BCO does them but is off on holiday for a couple of weeks and we need
them soonish.
Sounds a bit suspect, doesn't it?
BCO says "sucks teeth Lot of glazing there, mate, need a SAP report.
Luckily I can do one for you".
However the rules seem pretty specific so it is possibly not as dodgy as it
seems at first glance.

Cheers

Dave R
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

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