Changes to HVAC and DHW systems option in the approved software Part L 2021.
1. Major change to the way VRFs are modelled for EPC and Part L.
For many years, assessors would come across the problem of modelling a VRF system that incorporated a centralised mechanical ventilation system, an arrangement that was common in the past and is becoming more and more popular nowadays.
In the past, due to the limitations in the NCM and the software, assessors had to model this as a split-multisplit HVAC and the centralised mechanical ventilation SFP was entered at the zone level of every zone treated with mechanical ventilation. This was problematic for many reasons, mostly for Part L compliance considering that the SFP on the zone level is considered to be one for a local mechanical ventilation system, with low SFP, which was what the Notional Building would use. This created a discrepancy that made compliance and meeting minimum values from the ND Building Service Compliance Guide a lot harder.
With the new version of the software for Part L 2021 the assessors now have more option to represent this type of installation more accurately.
- VRF with natural ventilation – Select ‘Split or multi-split system’, and then adjust the efficiencies in the Heating and Cooling sub-tabs to values suitable for the VRF.
- VRF with mechanical ventilation – Select ‘Variable refrigerant flow’.
(i-sbem version 6.1.b user manual)
The Variable refrigerant flow option allows for mechanical ventilation to be set on the system’s level, representing a centralised mechanical ventilation system, that is compared appropriately with a similar system in the Notional building. This rectifies the issue assessors have faced for years.
2. Major change in the options for Changing facilities in the NCM activities database for D2 General Assembly and Leisure plus Night Clubs and Theatres
Domestic Hot water demand has been an issue with D2 Building type properties that had showers and changing facilities. The demand assumed was high and it was a challenge when the aim was Part L compliance.
With this in mind, there are now 3 different options in terms of NCM activities for changing facilities for this building type.
- Changing facilities with showers - High usage - An area used for changing, containing showers - high HW usage. This activity should be assigned to the shower area and all associated changing areas.
(assumed DHW demand of 120 l/d/m2 of activity)
- Changing facilities with showers - Medium usage - An area used for changing, containing showers - medium HW usage. This activity should be assigned to the shower area and all associated changing areas.
(assumed DHW demand of 60 l/d/m2 of activity)
- Changing facilities with showers - Low usage - An area used for changing, containing showers - low HW usage. This activity should be assigned to the shower area and all associated changing areas.
(assumed DHW demand of 30 l/d/m2 of activity)
The options allow for a greater flexibility of options in order to represent the design more accurately and make DHW demand targets more meaningful.
DHW demand for other building type has also been adjusted to more representative values to reflect the design of modern buildings.
For more details on the above and other changes in the new version of the NCM please have a look at the latest version of the NCM modelling guide and the NCM database.