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Presentation to Dublin City Council
17th May 2013
Flat Top Block Deep Retrofit – Energy
Long Block : Existing Energy Stats
Average BER – E1 (328 kWh/m2 y)
Average CO2 – 3497 kg/y
Delivered Energy – 16,093 kWh/y
Primary Energy – 18,648 kWh/y
Target BER of Deep Retrofit – A2
Initial Esquise Proposal
Individual gas boilers
Brick and steel proprietary facade system
Passive stack ventilation using existing chimneys
Tools of assessment
Build Desk U• U Values• Condensation Risk
Dwelling Energy Assessment Procedure• Building Energy Rating, CO2 emissions• Delivered Energy, Primary Energy
Therm 7.0• Linear Thermal bridges, Psi Value• For Calculation of Thermal Bridging Factor,
y
Initial Energy Strategy
Solar thermal panels, evacuated tube 1 sq m
per person, 4 sq m ground floor apartments
Individual gas boilers : Baxi Heating Solo
condensing boilers 91.3% efficiency
Q50 of 5 m3/h/m2 (reduced from 5.24 m3/h/m2
measured)
Area of south facing windows increased from
3 sq m to 5 sq m
U Values – typical wall 0.13 w/(m2k), roof 0.12
w/(m2k), gable wall 0.14 w/(m2k) windows, 0.7
w/(m2k), doors 1.2 w/(m2k),
Floor 0.2 w/(m2k) – involved removing
existing floor
Thermal bridging (y) factor : 0.05 (assumed)
from 0.32 (calculated)
U value calculations
Typical wall 0.13 w/(m2k). 200mm
expanded polystyrene external
insulation with render finish. 60mm
Kingspan K17 type phenolic insulated
plasterboard
Gable wall 0.14 w/(m2k) 200mm
expanded polystyrene with 70mm
insulated plasterboard
Floor : 0.2 w/(m2k). 160mm rigid
phenolic insulation
Roof construction 0.14 w/(m2k),
160mm rigid polyurethane
Reliance on fabric insulation to
achieve energy targets
Result of initial intervention
Group Heating
Centralised boiler system (required output 310 kW)
with heat exchanger units in each apartment
Reduces Delivered Energy Demand from 62 kWh/m2
y(A3) to 54.5 kWh/m2 y(A2)
Reduces Primary Energy Demand from 68 kWh/m2 y
to 44 kWh/m2 y
Reduces CO2 emissions from 12 kg/y per m2 to 8
kg/y per m2
MVHR
Mechanical Ventilation with heat recovery –
default Specific Fan Power (2 w/(l/s))
More realistic Y Factor based on ACDs (0.08)
Facilitates a major reduction in U Values
Walls : 0.19 w/(m2k)
Floor : 0.18 w/(m2k)
Thermal Bridging Factor
Calculated values range from 0.029 (mid - mid 2
bed unit) to 0.063 (unit 9, ground floor end)
Reduces Space Heating Demand from 656 kWh/y
to 551 kWh/y (Unit 9)
More pronounced effect on top - end reducing
Space heating Demand from 998 kWh/y to 804
kWh/y (Unit 32)
Overall improvement for top – end unit in primary
energy consumption from 47 to 45 kWh/m2 y
Space Heating Demand
Space heating demand in some units
virtually nil
Typical mid-mid unit (i.e. 20, 27) : 6
kWh/y
Unit 13 (mid unit) 3 bedroom : 16 kWh/y
Typical ground floor unit : 342 kWh/y
Water Heating demand remains
consistent
Biomass group Heating
Introduced to reduce CO2 emissions and
improve sustainability
Wood pellets – bulk supply
91% efficiency gas boiler to 85% efficiency
wood pellet boiler
CO2 emissions reduced from 602 kg/y to 228
kg/y in typical unit (unit 37)
Reduction in Group Solar Area
Conformity with TGD Part L Renewable Energy
Technologies met by introduction of Biomass
boiler
Reduce overall area of evacuated tubes from 120
m2 to 80 m2
Originally calculated as approx 1 m2 per person
% contribution of group solar reduced from 36%
to 27% in a typical apartment
Results
Area weighted
BER of A2 (36
kWh/m2/y)
Achieved without
over reliance on
fabric insulation
Conclusions
Iterative process
Balance required between fabric
insulation and systems
Difficulty in attaining certified
efficiencies for group heating systems