Part L2A 2013 – “How to pass” – Part 2

The Notional Building

To assess carbon compliance with the Part L 2013 building regulations, the building as designed is entered into modelling software and compared to a baseline building known as the ‘Notional’ building.

The Notional building is defined by the rules in the NCM modelling guide (for buildings other than dwellings). The following Notional parameters will be the same as for the building being assessed:

– Geometry
– Servicing strategy
– Fuel type
– Occupancy profiles

How to pass

 
The Notional building for the 2013 regulations is described below – as the building emissions must not be greater than the Notional emissions, a proposed building with identical parameters would pass the 2013 carbon emissions criteria.

However, in reality trade-offs would occur – it is not mandatory to meet any of these individual standards; instead overall carbon performance must be equal or better. Note that trade-offs are subject to certain minimum standards being met.

U-values:

– Walls: 0.26 W/m²K
– Roofs: 0.18 W/m²K
– Exposed floors: 0.22 W/m²K
– Glazing: 1.6 W/m²K, g-value = 0.40
– Rooflights: 1.8 W/m²K, g-value = 0.55

Air permeability:

– Generally 3 m³/m²/hour @ 50Pa or 5 m³/m²/hour @ 50Pa for buildings less than 250 m2.
– Higher for warehouse/ industrial buildings.

Heat generation:

– Distribution losses:10% distribution losses for space heating and 5% for domestic hot water
– Natural gas: Space heating: 91% – DHW: 91%/ 95% for radiant heating in industrial or warehouse buildings
– Electric heat pump: Space heating: 270% – DHW: 270%
– Bio-fuels: Space heating: 70% – DHW: 70%
– Direct electric: Space heating: 91% – DHW: 91%

Cooling:

– System Energy Emissions Rate (cooling energy out/ primary energy in), SEER = 4.5

Fan powers:

– Central systems: 1.80 W/l/s where ventilation provides heating or cooling, 0.9 W/l/s where ventilation does not provide heating or cooling
– Terminal Specific Fan Power: 0.30 W/l/s
– Exhaust  Specific Fan Power: 0.40 W/l/s (Local) or 0.60 W/l/s (remote from zone)
–  Demand controlled ventilation: Based on CO2 sensors, variable speed fans

Lighting:

–  Efficacy: 60 luminaire lumens per circuit-watt
– Daylight dimming: Applied in all zones that receive natural daylight
– Occupancy sensing: All zones (manual on- auto off)