Well, surprisingly my accreditation body belongs to the respected building services institution... . Probably worth checking with everybody's else accreditation bodies. It saves a lot of time to enter lighting this way.
I intend to use the design lux level for each activity. It indeed makes the lighting power density worse if the design lux level is higher than the NCM (IES) lux levels.
While discussing the lighting I want to ask if anybody else receives the BRUKL calculation from different consultancies stating that the actual building lighting consumption is better than the notional building lighting consumption. It happened to me on a few occasions and I'm struggling to believe that this is actually achievable.
Interesting topic all and valid points made. It is clear that this is another Part L2a/EPC 'grey' area and hence there are a number of routes that can be adopted, each perhaps with their issues. Perhaps the view could be taken that if the compliance tools being used are accredited (which they are), then surely any implementation they allow would be justifiable? My take on the input options are:
1.) That the gold standard approach, as CP has stated, is to use LPD and lux level figures. The presumption here is that a suitable maintenance factor has been applied as part of the LPD calculation (i.e. x 0.8 etc.). This approach should be taken where possible. Of course you have a much greater chance of being able to adopt this approach at design stage than at the as-built stage as contractors won't typically provide LPD and lux (Dialux) calculations and in my experience the design engineers likely won't have updated Dialux calculations in line with the actual installed fittings (if changed). So in this scenario what do you do? Demand Dialux outputs? That's unlikely to win any friends and it in all honesty is an unrealistic approach in many circumstances.
2.) Next option, it also appears that it is acceptable to adopt the luminaire efficacy (+lux level) approach. Again the presumption is that a suitable maintenance factor has been applied to the luminaire lm/W values. However, where would the design lux values come from? Dialux etc? Well if Dialux calculations existed then surely the LPD approach would be taken. Now, as far as I can tell, the only option if this approach is taken is to leave lux levels as per the default (Notional). This of course could be viewed as a concern.
3.) Now last but not least would be the total zone-by-zone circuit wattage approach whereby the total power consumption of all fittings per zone are summed and applied on a room-by-room basis. In my mind this approach is effectively the same as the LPD x lux approach (assuming maintenance factors match), though it is often far simpler to source/calculate total wattage values than request/receive dialux calculations for all spaces. The total wattage values for each fitting would be sourced from appropriate luminaire data sheets. Taking this common sense approach would of course mean that the achieved lux levels are not stated (no option to do this anyhow via this route) and this would perhaps be questionable if a space were to be designed to a lux level below the Notional lux level assumption.
VVladinovsky wrote:Thanks CP
While discussing the lighting I want to ask if anybody else receives the BRUKL calculation from different consultancies stating that the actual building lighting consumption is better than the notional building lighting consumption. It happened to me on a few occasions and I'm struggling to believe that this is actually achievable.
VV
It is achievable.
The notional building will calculate its W/m2/100lux on equation 7 of the NCM modelling Guide 2013 which assumes a luminaire efficacy of 60lm/W, a maintenance factor of 0.8 and is dependent on the ratio of total wall area to total floor area. I think this means the notional building can get down to about 2.4W/m2/100lux but no better than that.
This is actually pretty easy to beat with modern LEDs with many open plan offices achieving 2.0W/m2/100lux and under and the very highest efficiency (and very expensive) fittings can even get under 1.0W/m2/100lux.
JohnLloyd wrote:If you remove the "maintenance factor" from the W/m2/100 lux calculation you'll get a result much closer to that you got when using the lm/W figure.
It doesn't say you should do that in the NCM Guide, but it doesn't say you shouldn't either.
That's a great idea John except that I think the inference method is already supposed to account for a 0.8 MF. I make this wild claim on the following basis:
The NCM modelling guide clearly states that the notional building's lighting power density per 100lux is based on a luminaire efficacy of 60lm/W and a maintenance factor of 0.8.
If you set the actual building to inference and set the luminaire efficacy to 60lm/W, the resulting W/m2/100lux is exactly the same as that shown in the notional building. This can only mean that the inference method is using exactly the same governing equation as the notional building which we know includes an allowance for MF.
. Probably worth checking with everybody's else accreditation bodies. It saves a lot of time to enter lighting this way.
