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