IES-VE User Forum

Hi IES users,

I have a question regarding the NCM lighting profies in VE Compliance.

When modelling a school, VE compliance applies the appropriate NCM template to each room (classroom, circulation etc...)

According to these templates, classrooms appear to have no lighting gains during summer months (logical), however ancillary spaces have lighting gains all year round.

This seems unrealistic to me, but that's what the NCM templates say. I'm talking about profiles "NCM D1Edu_Toilet_Light[ BRE] estimates", "NCM D1Edu_Circulation_Light[BRE] estimates", etc...

The variation profile is greyed out, so we can't change these templates in our actual model. However, if we apply a dimming profile that is modulating (0,1) we can turn off the lights in our actual model completely during the summer. In practice the dimming profile will act as a variation profile this way. By doing that we can get a good margin from the notional.

The question is, are we allowed to do that? My guess is that we can't, because we have to compete with the notional building on equal terms, even if this means that we must have the lights on during summer, which is unrealistic (and why would the variation profile be greyed out anyway?). However, in the NCM modelling guide I haven't found anything that forbids that, creating a big opportunity for savings compared to the notional model.

I would like your opinion on this.

Regards,
George

Hi George,

You won't be allowed to do this. With Part L you are not simulating your real building (i.e how it will be used in the real world). Instead you are modelling the actual building which is the geometry, constrcutions of the real building with but with NCM Occupancy schedules and plant operation. See the following post for more on difference between them.

Paragraph 173 of the NCM Modelling Guide explains that the reason for this is to get a better like for like comparison between two buildings of the same type.

Hi Terence,

Thanks for clarifying this, created a lot of confusion to me.

The key is paragraph 173: "Thus, it is possible for the Building Regulation 26 compliance test and EPCs to compare
buildings on the basis of their intrinsic potential performance, regardless of how they may actually
be used in practice". I hadn't noticed that before.

Regards,
George