House 5

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Before renovation

House 5 belongs to a retired couple.   It has a single-storey with three bedrooms, living room, and open plan dining and kitchen. There is an ensuite, a separate toilet, bathroom and laundry. The house is clad with brick in the east, and weatherboard on the rest of the house. The timber framed windows are in good condition apart from the stays, leading to draughts. The house has a metal tile roof. The majority of the floor of the living areas is suspended timber, apart from the concrete slab floor of the lounge and the attached garage.

This house had its roof insulated and hot water cylinder wrapped in an EnergySmart insulation renovation from the Hutt Mana Energy Trust a couple of years earlier.  Some insulation was found in the garage walls but the underfloor was uninsulated.  The home is heated with a flued open gas fireplace in the lounge and a convection heater in the dining room.

The householders were keen to make their home warmer.

The renovation package

House 5 received a standard thermal retrofit with efficient hot water and a heat transfer system.  The house already has gas, and with a low occupancy house, the use of a ‘heat on demand’ system will reduce heat loss from hot water cylinders, and save energy. 

The major features installed were:

  • topping up ceiling insulation with a R1.8 blanket.  
  • insulating timber suspended floors with R2 foil-backed bulk insulation
  • laying under-floor polythene
  • replacing electric storage hot water cylinder with gas instant hot water units, one a high efficiency condensing model, at the two service areas
  • draught-stopping sliding door
  • installing ducted heat transfer system to move warm air into hallway by bedrooms
  • installing low flow shower head
  • ducting bathroom extraction fan to outside rather than into the roof cavity
  • using compact fluorescent bulbs in high-use light fittings
  • replacing old inefficient recessed kitchen lights with CA rated halogen downlights
  • a worm farm
  • a plumbing maintenance check


Improvements as a result of the renovations

Overall the improvements in house performance were relatively minor.  There were small improvements in winter reticulated energy use, space heating or hot water heating energy use.

A slightly warmer home

Temperatures in the family room and main bedroom improved slightly as a result of the measures.   Average winter temperatures in the main bedroom increased by 0.6°C.  Family room average temperatures didn’t change, but there was a reduction in the lowest temperatures experienced.

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 and bedroom, we can see a  ~1°C increase.  The temperature most often recorded in the family room before renovation was 14°C; after renovation, it was 15°C.  Likewise the bedroom moved from the most common temperature of 13°C to 14°C after renovation.

The heavy ceiling and under-floor insulation has helped retain the warmth in this home; however, the flued gas fireplace in the living room doesn’t seem to be producing enough heat to make the house really warm. 

Humidity levels were tested in July and found to be above 70% over half of the time. 

Lower power bills

The household’s electricity use reduced by 35% - largely as a result of the change in hot water system to instant gas hot water.  However, gas use increased by a similar amount, so the household may not have felt any cost savings. In the 2007 post-retrofit winter ,a reduction in hot water heating energy was also observed.  This is likely to be a result of the improved efficiency of the hot water system (instant gas is more efficient than a D grade electric cylinder), however again these savings were taken back in the 2008 winter. 

In the 2007 post-retrofit winter, a reduction in space heating energy was seen - likely as a result of the thermal improvements making the home easier to heat.  However this efficiency was largely taken back in the second winter. 


What the householders noticed

The householders felt the house was warmer, even though the monitored temperatures did not increase by much.  They felt that insulating underfloor and in the ceiling had made the most difference.

The new low flow shower head gave the impression of using less hot water, masking their increase in hot water use.

Draught stopping the sliding door has brought the added benefit of less noise and more quiet.


Our analysis

This home received a limited renovation, and its performance, as measured against the benchmarks of Beacon’s HSS High Standard of Sustainability®, could still be better. 

The household’s combined gas and electricity use remains high at around 12,500 kWh per year.  The benchmark for electricity and gas use is 7300 kWh per year.

Despite the increases in temperatures, 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. It is quite common for occupants to feel that temperatures have risen more than they actually have after insulation retrofits.  This is because we are sensitive to a combination of environmental conditions – draughts and air movement, humidity and temperature combine to determine how cold or warm we feel.

Further heat could be retained by draught stopping windows and installing heavy thermal curtains and pelmets.

No changes in heating efficiency were made in this home, which post-retrofit should have performed quite well for warmth - with (old) wall insulation, moderate ceiling insulation and heavy under-floor insulation.  This case study appears to confirm the hypothesis that an efficient heating system is needed alongside insulation, otherwise long term energy efficiency and healthy temperatures are unlikely to occur.  We suggest the next priority for this household would be an efficient heating system, possibly a heat pump in the bedroom.

Humidity, the percentage of moisture in the air, is recommended to be between 40% and 70%. 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.  We suggest installing a rangehood in the kitchen to remove moist kitchen air, in addition to heating the home more.

Apart from the plumbing check, no measures were undertaken in this house which would be expected to impact on water use.  The household’s average per person water use was 195 litres/pp/day compared to the benchmark of 125 litres/pp/day.


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House 5, Papakowhai