House 2

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Before renovation

House 2 is a two-storey colonial-style house belonging to a semi-retired couple.  This four bedroom home has a coated metal tile roof and a mixture of weatherboard and sheet cladding. The windows are timber throughout, with the exception of three new aluminium windows in the master bedroom, which was recently extended by around a metre. The lower storey is smaller than the upper storey, and backs onto a bank. The upper storey has timber suspended floors, while the lower storey has a concrete slab floor. The living areas and three of the four bedrooms are upstairs. The living area is approximately 140m2.

Fibreglass batts were installed throughout the ceiling cavity at least 24 years ago, and only the master bedroom had wall and underfloor insulation. The home still retained its original electric low pressure hot water cylinder, which was located within the ceiling cavity.

The house was heated with a wood burner, and oil column heaters downstairs when adult children are home.

The householders reported high levels of humidity requiring a dehumidifier. They wanted to reduce energy costs, and also liked the idea of an ‘eco-friendly’ renovation.

The renovation package

House 2 received a basic renovation package.  Insulation levels matched standards from Environment Canterbury and Ministry for the Environment energy retrofits, with the addition of waste-related features and improvements to indoor environment quality. 

The renovation included:

  • upgrading ceiling insulation to R2.6 and relaying dislodged existing insulation
  • insulating the suspended floor with R2 foil-backed bulk insulation
  • laying under-floor polythene vapour barrier
  • adding R1.1 hot water cylinder wrap and 15mm pipe lagging
  • adding an extra fan added to the heat transfer kit, and shortening ducting
  • installing a new cat door to stop draughts from a broken cat door to the garage
  • fixing a broken extraction fan in the bathroom
  • using compact fluorescent bulbs in high-use light fittings
  • a worm farm
  • a plumbing maintenance check

Improvements as a result of the renovations

A warmer home

Temperatures in the family room and main bedroom improved significantly as a result of the measures.  Average winter temperatures in the family room increased by 1.6°C.  Average winter temperatures in the main bedroom increased by 1.1°C.

These temperatures are given as averages (mean), and as the overnight temperatures are still low, it brings the average temperature down. 

However, looking at the most common temperature experienced in winter in the family room, we can see a  ~1°C increase.  The temperature most often recorded in the family room before renovation was 15°C; after renovation, it was 16°C.  15°C remains the most common temperature in the bedroom, although there is a reduction in the frequency of lower temperatures.

The ceiling and under-floor insulation has helped retain the warmth from the wood burner in this home.  The temperature increases occurred without any increase in the amount of wood used.


Lower power bills

This household’s electricity use reduced quite a lot - probably through a combination of the improved efficiency of the hot water system (from wrapping the hot water cylinder and lagging the pipes) and the changes in the household. Overall the household used significantly less electricity to heat their water with a reduction of 11% in hot water energy use during winter.

This contributed to an overall reduction in electricity use of ~6% over winter and ~35% over the whole year.


What the householders found

The householders were keen to reduce expenditure on energy, become more ‘eco-friendly’ and address problems with humidity.

The householders have found the house to be much warmer – in fact, even warmer than the measurements suggest.  Despite leaving the doors open, the family room is easily heated and they believe that they are receiving more benefit from their enclosed wood burner.

They have found the basement drier and can walk around the house in bare feet without becoming chilled. They put this down to the under floor insulation which they would have installed earlier if they had known the benefits.  They have given away their dehumidifier as they no longer need it. However, the householders removed the polythene ground cover in the basement after a previously unidentified site drainage problem caused water to build up on top of the polythene. 

They did not find the worm farm successful.

Our analysis

When this home’s performance is measured against the benchmarks of Beacon’s HSS High Standard of Sustainability®, it could still perform better for these homeowners. 

Their electricity use is low at around 4900 kWh per year compared to the benchmark for electricity use of 7300 kWh per year.  The lower power bills may also reflect changes in occupancy with adult children moving out of home. We would suggest replacing the old hot water cylinder with a heat pump hot water system.

While the temperature increases are good, both the family room and the main bedroom remain below the HSS High Standard of Sustainability® benchmarks.  The average minimum winter overnight temperature was 13.4°C in the main bedroom, and the average 24 hour winter bedroom temperature was only 14.2°C.  Our benchmarks, based on World Health Organisation recommendations, set a minimum of 16°C overnight in bedrooms and 18°C in the evenings for family rooms.  We suggest further improving the home’s indoor temperatures  by extending insulation to the walls, topping up the ceiling insulation to maximum levels and adding thick thermal curtains and pelmets.  We also suggest replacing the old wood burner with a modern low emission wood burner, and installing a heat transfer system to take heat to the bedrooms.

Humidity, the percentage of moisture in the air, is recommended to be between 40% and 70%.  Humidity levels were tested in July and found to be above 70% a third of the time.  Humidity is linked to the cold indoor temperatures, as cold air holds far less moisture than warm air.  In cold temperatures, the moisture naturally in the air settles on cold surfaces such as un-insulated walls, ceilings and windows as condensation.  Condensation and cold are the perfect conditions for growing mould which thrives in humidity greater than 70% on cold surfaces with condensation potential.

The polythene ground cover would have been effective in preventing moisture coming up from the ground into the house – a common cause of damp and mould.  However wider site drainage problems meant that stormwater going under the house ended up ponding on top of the polythene.  The best option here would be for the stormwater to be diverted and the drainage problems to be sorted, as this moisture otherwise will continue to rise into the house.

Apart from the plumbing check, no measures were undertaken in this house which would be expected to impact on water use.  The average per person water use was 220 litres/pp/day compared to the benchmark of 125 litres/pp/day.


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House 2, Papakowhai