Learnings from Recent New Home Monitoring Projects

Transcription

1 PRES/31 Learnings from Recent New Home Monitoring Projects Lois Easton

2 Good practice group builder homes Two houses built in 2009 in Rangiora & performance monitored over 2010 calendar year House 1 standard design for the development good practice in solar orientation, thermal envelope House 2 same design plus an internal thermal wall (EnerG Wall) Houses HERS rated House 1 received 4.5 stars and House 2 (EnerG Wall) received 6 stars 3 bedrooms and 142m 2 (incl. double garage) Houses built as part of Council affordable rental housing portfolio 2 adults & 2 children in one home and 2 adults & 3 children in the other

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4 Performance against the HSS High Standard of Sustainability Criteria Benchmark House 1 House 2 (EnerG Wall) Energy use (Climate Zone 3) 7,300 kwhr/yr 14,400 kwh/yr 10,800 kwh/yr Temperature (Living room) Average 18 C 5-11pm in winter 21.0 C 22.0 C Temperature (Bedroom) Relative humidity (Living room) Relative humidity (Bedroom) Average 16 C 11pm-7am in winter * 16.3 C 17.7 C Average 40-70% 5-11pm in winter * 51% 48% Average 40-70% 11pm-7am in winter * 66% 60% Mechanical extract ventilation, IEQ checklist passive venting, DPM, no UFG Yes Yes heaters * Winter has been taken as May to September

5 Key findings The houses were warm and dry and healthy temperatures BUT This was achieved through high energy use. In both cases, heat pumps were used and in the case of House 1, they were used for summer cooling as well as heating The EnerG Wall had a minimal impact on the house occupancy behaviour outweighed this

6 Design of the EnerG Wall The design EnerG wall could be improved to optimise the performance of the thermal mass. Some design improvements are: Maximise the exposure to sunlight by locating the wall closer to the external environment (in this case the walls were situated deep within the building) Leave the surface exposed (in this case the wall was lined with plasterboard) Locate the wall within the insulated envelope of the house (in this case one wall backed onto an unconditioned space, the garage).

7 NZ Housing Foundation s HomeSmart Home The house was built in 2009 Design was standard to the development but amended to meet Beacon HomeSmart Home guidelines and achieve an 8 Star HERS rating 4 bedrooms and 160m 2 (incl. double garage) House is occupied by a family of 2 adults,2 children and 2 teenagers Performance monitoring occurred over the 2010 calendar year

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9 Performance against the HSS High Standard of Sustainability Criteria Benchmark NZHF HomeSmart Home Energy Use 5800 kwh/year 3890 kwh/year Water Use 125 litres/person/day Living Room Mean Temperature Bedroom Mean Temperature Living Room Mean Relative Humidity Bedroom Mean RelativeHumidity >18 C pm in Winter* >16 C - 11pm-7am in Winter* 40-70% pm in Winter* 40-70% - 11pm- 7am in Winter* 117 litres/person/day 19.0 C 18.0 C 62% 62%

10 Key features which contributed to high performance Photovoltaic panels generated 50% of electricity used Heat pump hot water system Passive solar design High insulation and double glazing Water efficient fittings Efficient lighting system Greywater system reused 30% of greywater produced Rainwater tank

11 Photovoltaic system

12 Photovoltaic system performance Energy (kwh / day) Grey water system Rest of house PV system 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

13 Occupant experience Found the house to be very warm in winter only used the heater when first moved in with newborn baby Did find the house hot in summer particularly upstairs Very pleased with hot water system felt it was a major reason for low power bills Happy with the greywater system Would have liked a larger rainwater tank 2010 drought meant tank ran dry

14 Impact on the occupants Reduced asthma and inhaler use Reduced illness in the baby and children Increased awareness of energy efficiency and their impact on the environment Started composting and planned to install a vege garden Location by extended family in the wider subdivision was a real positive Rated the house a 8-9 compared to previous homes

15 Comparison with other high performance homes Compared with the 2 Beacon NOW Homes and 2 good practice group builder houses The NZHF HomeSmart Home performed as well, or better than the high performance NOW Homes on all indices Performance far exceeded that of the good practice group builder houses The NZHF HomeSmart Home was the star performer in terms of electricity use even without the photovoltaic panels

16 Rangiora House 1 Rangiora House 2 (EnerGWall) NZHF HomeSmart Home Waitakere NOW Home Number of Occupants Annual reticulated energy use Average winter living room evening temperature Average winter bedroom overnight temperature Average living room relative humidity 14,400 kwh/yr * 10,800 kwh/yr * 3890kWh/yr 7400 kwh/yr 21 C 22 C 19 C 20.3 C 16.3 C 17.7 C 18 C 19.1 C 51% 48% 62% 57% Average bedroom relative humidity 66% 60% 62% 60% *Due to the greater heating demand in the South Island, the HSS benchmark for reticulated energy use in Rangiora is 7300 kwh/year

17 Cost benefit of key features Based on current electricity and installation prices the simple payback periods are: 8.5 years for a heat pump hot water system 22 years for the photovoltaic panels 32 years for the greywater system Electricity prices have risen 72% in the last 10 years with a 30% further increase payback periods drop to: 6.8 years for a heat pump hot water system 16.9 years for photovoltaic panels

18 Passive solar and high performance thermal design From an occupant perspective, the thermal performance gives the greatest benefits Reduced/minimal heating costs Improved health Improved wellbeing Of these, they see reduced energy costs are the smallest benefit

19 Water efficient design Low cost for water efficient fittings makes these a top priority While the greywater system was a good performer, in urban situations a larger rainwater tank plumbed to outside, toilet & laundry gives a better financial payback (17.5 years)

20 Areas for improvement Some layout and design improvements Maximising usefulness of living areas (more open plan) Getting the balance between garage size and living space size right Better stack and cross ventilation like the Rangiora houses, the NZHF house overheated in summer

21 Key conclusions The NZHF HomeSmart Home delivered an excellent high performance outcome for the household and the environment Some of the features included in the NZHF HomeSmart House would ideally be included as standard in all NZHF new homes Good passive solar design Heat pump hot water system Water efficient fittings High specification insulation in ceiling & walls Double glazing in bedrooms In Auckland, rainwater systems

22 Overheating in houses and thermal models The NZHF house received an 8 Star HERS Rating, and the Rangiora Homes received 4.5 Stars and 6 Stars respectively All of these homes had overheating problems the NZHF house included a solar powered stack vent but this was not enough It seems neither HERS nor ALF (and now Homestar) deal with overheating issues adequately