paola sassi, senior lecturer school of the built...

School of the Built Environment

Zero heating house?

Paola Sassi, Senior lecturerDepartment of Architecture, Oxford Brookes University


• Background to project

• Design aims and construction

• Initial cost appraisals


Cardiff


Cardiff city centreSite plan


Design aims

• Minimise operational energy

• Design for closed loop material cycles

• Create a healthy living environment• Enable a low ecological footprint lifestyle


Design aims




• Build two flats: one to live in and the other to fund the construction


Design aims





Minimise operational energy

Design based on Passivhaus standard

• Passivhaus is a house that provides a comfortable environment without auxiliary heating

• Maximum heating requirements of 15 kWh/m²a• Maximum air changes per hour 0.6

• Maximum total primary energy requirements of 120 kWh/m²a

• Energy requirements should be covered by alternative energy forms

• Provide a Factor 4 improvement on energy use of the typical new housing development


Energy consumption comparison

electricity

ventilation energy

Hot water heating

Space heating

1930’s UK home

Typical UK Building Regulations

250-300kWh/sqma

200kWh/sqma


Passivhaus design principles

• Well insulated building fabric - Compact and well insulated building envelope with U-value of less than 0.15 W/m²K AND U-values of windows including glass and frame not to exceed 0.8 W/m²K AND minimise cold bridging

• Airtight structure - maximum 0.6 air changes per hour

• Passive solar heating - South orientation of living spaces with maximum glazing on south side of building and minimal overshadowing

• Ventilation with heat recovery of stale air. Mechanical ventilation with heat recovery with over 80% efficiency. Passive pre-heating of fresh air entering the building, possibly through a earth ducts

• Water heating using alternative heat sources such as with solar panels and heat pumps.

• Appliances to be energy efficient


Ground floor First floor

Mezzanine


North Elevation South Elevation


Passive solar - harnessing solar heat

South elevation North elevation


Passive solar - harnessing solar heat

14961068

98152

64207

00

1334709

00

kWh/akWh/a

Heat Gains Solar RadiationTransmission Losses

21392604

98152

104518

00

19371933

00

kWh/akWh/a

Heat Gains Solar Radiation

Transmission Losses

U-value windows 0.7W/m²K U-value windows 1.6 - 0.7 W/m²K


Wall and roof construction – U-value 0.13W/sqmK

• Ply finish to walls

• Plasterboard for fire protection

• 100mm service void insulated with hemp

• Vapour control layer

• 200mm structural frame insulated with hemp

• 80mm timber fibre insulation

• Render/ timber cladding finish


Minimising cold bridges

Inward opening windows with min. 50mm insulation covering the frame externally


Airtight construction


Airtight construction Test results ground floor flat

• 1.8 m³/m² = 2.7air changes/hr

Test results first floor flat

• 1.3 m³/m² = 1.7air changes/hr


Mechanical ventilation with heat recovery


Mechanical ventilation with heat recovery (92%)


Solar thermal panels and photovoltaics (1.25kWp)

2993 CO2 kg/a without renewables

546 CO2 kg/a savings from PVs

864 CO2 kg/a savings from solar thermal

1583 CO2 kg/a with renewables


Solar thermal cylinder


Carbon dioxide emission further improvements









Alternative hot water and heating from gas

Existing hot water and heating electric


Design aims





Design for closed loop material cycles


Timber32 Cork3Carpet1 vinyl1 2 fixed with adhesive

Floor finishes

Ply with natural glues 3Plasterboard12wall /ceiling finishes

Timber 23 Chipboard 1Floor panel lining

Timber 3PVC1 / Metal2Rainwater goods

Timber3Conc. tiles1 slates2Roof finishes

Timber123Brick1 Render2External cladding

PE1 2Vapour control

Hardboard 23 OSB 1Wall panel lining

Wood fibre insulation 2polyurethane1External insulation

Recycled cellulose fibre 23Rockwool1Insulation btw studs

EPS1Insulation below ground

timber123Frame windows doors

timber3Concrete 12Foundations

Naturally recyclable Industrially recyclable Non-recyclable Building elements

Table 1 – Specification of three housing types divided by material waste disposal optionsHouse 1= 1 House 2=2 House 3=3


Waste by weight Waste by volume


Design for closed loop material cycles - Problems

Easily overcome problems

• Render – Alternative = rainscreen cladding

• Concrete slab - Alternative = suspended timber (or other) floor• Under ground extruded polystyrene insulation – Alternative = foam

glass• Plaster – Alternative = timber or other cladding

Not easily overcome problems• Concrete foundations – Alternative = steel or timber piles

• Sealants for acoustic separation and airtightness – Alternative design configurations or compressible fillers


Design aims





Create a healthy living environment

• Materials associated with minimal off-gassing of formaldehyde and other volatile organic compounds

• Hygroscopic materials, including hemp and timber, to help balance the humidity of the building

• Ample natural light throughout the dwellings.


Create a healthy living environment – thermal comfort

UNITS 4 AND 5 03/03/08 TO 04/03/08 - unoccupied

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Unit 4 Entrance

Unit 4 Living room high lvl

Unit 4 Cpd with hot water cylinder

Unit 4 Bathroom

Unit 4 Living room low lvl

Unit 4 Corridor

Unit 4 Bedroom

Unit 5 Bedroom

Unit 5 Living room

Unit 5 Mezzanine


SUMMER DAY - Ground floor flat OCCUPIED

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Unit 4 Entrance

Unit 4 Living roomhigh lvl

Unit 4 Cpd withhot water cylinder

Unit 4 Bathroom

Unit 4 Living roomlow lvl

Unit 4 Corridor

Unit 4 Bedroom


SUMMER DAY - UNIT 5 UNOCCUPIED

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Unit 5 Bedroom

Unit 5 Living room

Unit 5 Mezzanine


Design aims





Calculation of ecological footprint – www.myfootprint.org

There are only 15.71 global hectares available per person on a renewable basis.


Initial cost appraisals

• Is it affordable?

• What is the payback for the energy efficient design?


Initial appraisals

yesyesPVs

yesyesSolar thermal panels

yesyesyesyesExternal insulation

yesyesyes300mm insulation within structure

yesyesPassivhaus certified windows

yesyesProclima with maximum airtightness

yesyessunpipe

yesCentral heating no MVHR

yesMVHR 70%

yesyesMVHR 92%

yesRainwater harvesting

yesLow dual flush WC

yesMinimal PVC

yesFully demountable construction

yesNatural insulation

4321House specification option


Cost comparison

£14,928.87yearly mortgage payments (5.45) + energy running cos ts£14,592.00Yearly mortgage payments (5.45% interest repayment mortgage for 25 years)£16,392.87yearly mortgage payments + energy running costs

£336.874 - Yearly energy costs

£16,056.004 - yearly mortgage payments (6.45% interest repayment mortgage for 25 yrs)18.3%£30,787.34£199,090.43total paid

Built option - energy efficient AND eco - Option 4

£14,460.87yearly mortgage payments (5.45) + energy running cos ts£14,124.00Yearly mortgage payments (5.45% interest repayment mortgage for 25 years)£15,876.87yearly mortgage payments + energy running costs

£336.873 - Yearly energy costs£15,540.003 - yearly mortgage payments (6.45% interest repayment mortgage for 25 yrs)

14.5%£24,448.17£192,751.25total paidEnergy efficient but NON-eco - Option 3

£14,906.17yearly mortgage payments + energy running costs

£1,262.172 - Yearly energy costs£13,644.002 - yearly mortgage payments (6.45% interest repayment mortgage for 25 years)

0.6%£929.31£169,232.40total paidNON-energy efficient and NON-eco - Option 2

£15,228.26yearly mortgage payments + energy running costs£1,656.26Yearly energy costs based on PHPP

£13,572.00Yearly mortgage payments (6.45% interest repayment mortgage for 25 years)£168,303.08total paid

percentage increase on base

additional cost compared to baseBld Regs equivalent - Option 1 (base)


Yearly mortgage and energy costs

£0

£2,000

£4,000

£6,000

£8,000

£10,000

£12,000

£14,000

£16,000

£18,000

option 1 -2008 energy

prices


prices


prices

option 3A -2008 energyprices and

1% mortgagediscount forrenew ables


prices

option 4A -2008 energyprices and

1% mortgagediscount forrenew ables

Yearly energy costs

Yearly mortgage payments (6.45% interestrepayment mortgage for 25 years)


option 4A - 2008 energy prices and 1% mortgage discount for renewables-£299.39

option 4 - 2008 energy prices £1,164.61

option 3A - 2008 energy prices and 1% mortgage discount for renewables-£767.39

option 3 - 2008 energy prices £648.61

option 2 - 2008 energy prices -£322.09

option 1 - 2008 energy prices £15,228.26


£12,000

£12,500

£13,000

£13,500

£14,000

£14,500

£15,000

£15,500

£16,000

£16,500

option 1 - 50%increase in energy

prices


prices


prices

Yearly energy costs

Yearly mortgage payments (6.45%interest repayment mortgage for25 years)


Thank you

Questions?

paola sassi, senior lecturer school of the built...

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