David Ross, AECOM presents on the regulatory Impact Assessment for Part L dwellings at the SEAI Energy SHow, April 2018.

1. Regulatory Impact Assessment for Part L
Dwellings
David Ross, AECOM
18 April 2018

2. Project Scope
DHPLG appointed AECOM and Currie and Brown to carry out the
following :
– Energy and carbon performance modelling for 5 typical new
dwellings constructed to NZEB performance levels
– Identify the uplift in capital cost for NZEB performance
– Assess any associated overheating risk
– Review the performance of renewable energy systems in multi-
storey apartment blocks
– (Identify the additional capital cost of major renovations to a
cost optimal level as required under EPBD)

3. Definition of NZEB
The European Energy Performance of Buildings Directive has the
following definition:
– “a building that has a very high energy performance…. The
nearly zero or very low amount of energy required should be
covered to a very significant extent by energy from renewable
sources including energy from renewable sources produced on-
site or nearby”

4. Definition of NZEB
DHPLG has the more explicit definition:
– Maximum Energy Performance Coefficient of 0.30
– Maximum Carbon Performance Coefficient of 0.35
– Minimum Renewable Energy Ratio of 0.20

5. Specifications to meet NZEB: Dwelling types
Building Category Building Type Floor Area
Single Family
Buildings
Semi-Detached
House
126 m2
Detached House 160 m2
Bungalow 104 m2
Apartment Block Mid-Floor Flat 80 m2
Top-Floor Flat 80 m2

6. Specifications to meet NZEB: Fabric and Services
Elements Proposed Part L 2018 specification
External Wall U-value 0.13
Floor U-value 0.14
Roof U-value 0.11
Windows U-value 0.9 (Triple glazed)
Thermal Bridging Y-value 0.05
Air Permeability 5
Ventilation strategy Natural ventilation (or cMEV at 3m3/m2/hr)
Heating system 91.3% mains gas condensing gas boiler
Controls
Boiler interlock
Time and temperature zone control
Hot water demand
1 shower with 6 litres/min flow restrictor
1 Bath
No electric showers
Overall target of 125 litres/person/day
Hot water cylinder 120 litres, 100mm factory insulated
Lighting
100% low energy lighting:
· A+ Rated Bulbs, 94 lumen/cW, 4 W/m2

7. Specifications to meet NZEB: Renewables (Semi)
Heating and
Ventilation
PV
(kWp)
PV
(% roof
area)
EPC CPC RER
Gas Boiler
NV
1.15 7% 0.30 0.28 0.22
Gas Boiler
MVHR + AP of 3
0.85 5% 0.26 0.24 0.20
Heat Pump
NV
0 0% 0.25 0.21 0.42
Heat Pump
MVHR + AP of 3
0 0% 0.25 0.20 0.33
MVHR: SFP = 0.8 W/l/s, HR = 85%
HP: Individual air to water, underfloor heating, SH =400%, DHW = 200%

8. Specifications to meet NZEB: Renewables (Mid-flat)
Heating and
Ventilation
PV
(kWp)
PV
(% roof
area)
EPC CPC RER
Gas Boiler
NV
0.85 8% 0.30 0.29 0.27
Gas Boiler
MVHR + AP of 3
0.55 5% 0.27 0.26 0.20
Heat Pump
NV
0 0% 0.29 0.25 0.37
Heat Pump
MVHR + AP of 3
0 0% 0.29 0.25 0.29

9. Uplift in capital cost to meet NZEB
Currie and Brown provided 2017 Dublin Cost data
– Internal cost database (live projects they are supporting)
– Cross-checked with peers who have independent experience of
the Irish construction market
– Cross-referenced with a third party database in the Irish market
Uplift against TGD 2011
– Based on Appendix E of TGD 2011
– Amount of PV varying by building type

10. Uplift in capital cost (depending on compliant solution)
Building Type Additional
CAPEX
(€/m2)
Additional
CAPEX
(%)
Semi-Detached House 12 to 39 0.9 to 2.9
Detached House 13 to 49 1.0 to 3.5
Bungalow 14 to 65 1.0 to 4.2
Top-Floor Flat 13 to 49 0.7 to 2.9
Mid-Floor Flat 8 to 49 0.5 to 2.9
– NZEB can be achieved ~0.5-1.0% uplift of current CAPEX
– Lowest cost solutions: PV or HP alone (CAPEX associated with
move to triple glazing & LZCs)
– Higher cost solutions: SHW or adding cMEV/MVHR

11. Assess overheating risk
Apply new CIBSE TM59 modelling methodology and criteria
to assess residential overheating
– Criterion A (living rooms, kitchens & bedrooms)
Internal temperature should not exceed a defined comfort
temperature by 1°C or more for more than 3% of occupied
hours over the summer period (May to Sept)
– Criterion B (bedrooms)
The internal temperature between 10 pm and 7 am should not
exceed 26°C for more than 1% of annual hours

12. Assess overheating risk
– Undertook IES thermal modelling
• Five dwelling forms
• Manchester 2020s DSY1 weather file (Dublin data TBC)
• TM59 methodology occupancy profile, heat gains etc
– Occupants:
• Detached house: 4 bed 8 person
• Semi-detached house: 3 bed 5 person
• Bungalow: 3 bed 6 person
• Apartments: 2 bed 4 people
– Daytime occupancy assumed in all cases

13. Assess overheating risk
– Windows start to open in occupied rooms when indoor
(operative) temperature > 22C and fully open when
temperature > 26C. Reverse occurs at temperatures fall.
– Internal doors open all the time, with the exception of bedroom
doors which are closed overnight
– Windows: g-value = 0.6 (triple glazed, low E, soft coat)
– Orientation
• Living rooms face west. Apartments assumed west and south
• No external shading or internal blinds/ curtains assumed for
base-case

14. Assess overheating risk
– Risk mitigation sufficient where dwelling overheated
• Occupant controlled curtain/ blinds drawn on the east, west
and/or south façades when incident solar radiation
• Incident radiation to lower shade - 200 W/m2
• Incident radiation to raise shade - 150 W/m2

15. Assess overheating risk: Before any mitigation
Building
Type
Room
TM59 Criteria A TM59 Criteria B
% hours
exceeded
Pass/Fail
% hours
exceeded
Pass/Fail
Semi
Detached
Living Room 2.8% Pass - -
Bedroom 1 1.6% Pass 0.58% Pass
Bedroom 2 1.0% Pass 0.55% Pass
Bedroom 3 3.5% Fail 0.79% Pass
Detached
Living Room 2.7% Pass - -
Bedroom 1 1.4% Pass 0.94% Pass
Bedroom 2 1.4% Pass 0.91% Pass
Bedroom 3 1.8% Pass 0.85% Pass
Bedroom 4 1.8% Pass 0.88% Pass
Bungalow
Living Room 3.4% Fail - -
Bedroom 1 0.8% Pass 0.52% Pass
Bedroom 2 2.0% Pass 0.85% Pass
Bedroom 3 2.2% Pass 0.85% Pass
Top Floor
Apartment
Liv / Kitchen 3.3% Fail - -
Bedroom 1 0.7% Pass 0.49% Pass
Bedroom 2 1.1% Pass 0.55% Pass
Mid Floor
Apartment
Liv/ Kitchen 4.1% Fail - -
Bedroom 1 0.9% Pass 0.64% Pass
Bedroom 2 1.4% Pass 0.70% Pass

16. Renewable energy systems in apartment blocks
– Evaluate ability of city apartment block to meet RER of 20%
• Two apartment blocks: 6 & 14 stories (12 units per floor)
• Heat pumps or PVs (roof only)
– To work out the maximum available roof area for PVs:
• 70% of roof area available for PV, after services and over-
shading
• 20% allowance for spacing between panels and access.
• Net maximum available area of 56% of the total roof area.

17. Renewable energy systems in apartment blocks
– Results showed
• gas boilers and PVs feasible to 12 stories
• Heat pumps feasible for all heights
Ventilation
Package
Heating
Package
kWp per
apartment
EPC CPC RER Comply
Natural ventilation Gas boiler 0.50 0.33 0.31 0.16 No
Natural ventilation Heat pump - 0.28 0.24 0.37 Yes
MVHR Gas boiler 0.50 0.28 0.26 0.18 No
MVHR Heat pump - 0.28 0.24 0.29 Yes
Results for 14 storey apartment block

18. – The dwelling types achieved compliance with proposed NZEB
specification using different design solutions.
– Average cost uplift across dwellings was 1.9%. Range of 0.5% to
4.2% depending on dwelling and design solution.
– Overheating analysis indicated a relatively small overheating risk
based on the new CIBSE TM59. The mitigation package was fairly
limited to occupant controlled curtain/ blinds.
– Heat pumps are feasible solution to meet RER on all apartment
blocks. PV is feasible for the apartment block modelled up to 12
storeys in height.
Conclusions

19. Thank You