IES-VE User Forum

Hi,

Is it possible to make some minor improvements to the default values used in VE compliance? These play an important role in EPCs particularly for existing buildings.

The iSBEM technical manual has several equations for when values aren't known. Examples being:

DHW Secondary circulation loop length is a function of the area served
DHW Pump power is a function of the loop length
PV Panel shading factor is established through descriptions e.g. Modest, Significant or Heavy. A default of 1 is very optimistic for a shaded site.

As this all comes straight from BRE, I assume it is all official and approved.

Ross

Hi Ross

Just playing devil's advocate here (I actually like your idea)

Looking into my crystal ball I think there are two reasons IES will give for not wanting to "improve" the defaults:

1) it would encourage the use of software defaults in general which should really be discouraged (new users may also get confused as to what can be safely left on defaults and what really should not be)

2) it could become quite a big commitment in resources for IES since the defaults would need to be kept up to date with subsequent revisions of the guidance documents.

Hi CP,

Both fair points, although I don't think the defaults really get revised in iSBEM.

Its just a bit strange that the authorities are very keen to audit assessors to ensure EPCs are consistent, but at the same time they approve software with completely different defaults!


Ross

Heh, differing defaults is only the tip of the iceberg. The BRE have approved both IES and Tas and they use different fan powers for the notional building

Also, although iSBEM doesn't talk about defaults, if IES based its defaults on the fallback recommendations therein, they would presumably need to change the IES defaults whenever iSBEM revises it's advice.