Appendix A. Comparison between L2 England 2013 and 2021

This appendix provides a summary of the changes between 2013 & 2021 iterations of L2A.

Headlines:

· Reduce emissions by 27% (non-domestic on average)

· CO2 target (TER) plus new primary energy target (TPER)

· Notional building U values tightened

· New emission factors including for electricity monthly values

· New emission factors for heat networks

· New Part O (overheating) for residential elements

· Solar gain checks for non-residential spaces

· 1000m2 non-residential buildings need to produce a TM54 energy forecast

· CIBSE 2016 TRY weather files are to be used in place of 2006

(Affects thermal/energy simulations and solar gain limit targets)

· Weather files upgraded to DSY1 for Part O overheating simulation

Key details:

· Side & top-lit space types now affect notional fabric

· High & low hot water demand classification added

· Notional building heating fuel as actual

· Notional building U values tightened

· Notional non-repeating thermal bridging allowance is 10% (actual is 25%)

· Notional building now includes PVs (unless heat pump)

· Revised approach for determining the illuminance level for a zone in the Notional building

· Revised approach for accounting for primary energy due to electricity generated on-site by renewables

· Updated options for HVAC systems (added added ‘VRF’ and ‘Chilled ceilings or passive chilled beams and mixing ventilation’ )

· Calculation of the corresponding fan energy

· Revised approach for calculating the fan energy associated with demand control of ventilation

· Emission factors for electricity values are now monthly

· New grid displaced PV energy source added

· New district heating values (still as single input value for CO2 Factor & Primary Energy factor)

· In the AB you specify new/existing district heating this influences NB factors directly

Notional building details:

· Size, shape, zoning, topographical shading & weather is the same as the actual building as 2013

· Local shades are ignored

· Openings are generated with the same dimensions as 2013

· Non-repeating thermal bridging allowance is 10% (actual is 25%)

· Air permeability tightened to 3 & 5 m3/h.m2 at 50Pa (side/unlit & top-lit)

· Aux energy: pump power density is the same as 2013

· Aux energy: fan pump power density is the same as 2013 except for HEPA filters (Hosp_OpTheatre)

· Aux energy: local mechanical exhaust is the same as 2013

· Power factor is the same as 2013

· PVs included based on equation 9 but reduced if heating demand is met with a heat pump (100% demand met means no PV in NB)

· Lighting design illuminance: set as the Actual building but clamped to the maximum or minimum illuminance as per activity (template)

· The general lighting is based on lighting with efficacy of 95 luminaire lumens per circuit-watt; so a notable tightening over 2013 value of 60

· Display lighting LPD: luminous efficacy of 95 light source lumens per circuit-watt so the display lighting power density in the Notional zone will be from the NCM Activity Database multiplied by 0.158 (2013 was 0.682)

· Parasitic power density to 0.1 W/m2 for photoelectric or occupancy dimming control (2013 was 0.3)

· U values overall tighter for side & unlit activities; windows at 1.4, although top-lit roof-lights are more generous at 2.1

· Thermal capacity is light / very lightweight

· Construction details (app A): layers have been updated

· Heating fuel & efficiency set by the actual building

· High & low hot water demand classification & actual fuel sets notional seasonal efficiency, fuel & if-storage for notional building DHW

· Cooling SSEER is revised and heat recovery efficiency is revised

Actual building details:

· Non repeating thermal bridging allowance + 25% (notional & reference 10%)

· Pump power densities the same as 2013 but new entries for VRF / chilled ceilings

· Fan power density equation 15 has changed (now x 0.85)

· Lighting design illuminance must be pro rated to NCM minm. in activity database when less than the NCM minm.

· Lighting inference: luminaire luminous efficacy value of 95 (2013 uses 60)

· Demand control ventilation aux energy adjustment has been revised

· Modular & potable buildings TER & TPER factors revised

· Criterion 3 limiting solar gains: benchmark glazing g-values and for type 3 area have been reduced (type 1&2 where 0.68 in 2013)

Reference building details:

· Definition is the same as 2013

· Construction U values & thermal mass are the same as 2013

· Non-repeating thermal bridges allowance 10% same as 2013

· HVAC now defines all spaces as naturally ventilated with the same 27degC cooling setpoint as 2013

· The HWS seasonal efficiency is the same as 2013

· Lighting illuminance level is defined similar to that for the notional building; the W/m2. 100 lux values are the same as 2013

· Manual switching is defined the same as 2013