House 3

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Before renovation

House 3 belongs to a young family of five and also houses a small business run from home during the day.  Built in the 1970s, the house contains a large open plan living and dining area, and kitchen on the upper floor. The bedroom wing contains three bedrooms, a large foyer, bathroom and toilet upstairs. Downstairs there is a laundry, toilet, small and large offices, and recently an additional office was put into the rear of the garage. The living area is approximately 120m2 excluding the office space.

The exterior cladding is a mainly weatherboard and sheet cladding, with concrete block around the addition, and a small stone veneer façade at the front of the garage. The lower floor has a concrete slab floor, while the upper floor has timber suspended floors. The corrugated iron roof was in poor condition and is partly skillion, partly cavity. The windows were single-glazed in unventilated aluminium frames, which were badly degraded and in need of replacement. 

Interestingly, the walls contain batts which appear to have been installed when the house was being constructed, yet the roof was uninsulated until the new owners installed R2.6 batts in the ceiling cavity over the bedroom wing. The skillion roof above the living areas and the underfloor area beneath the bedroom wing were uninsulated.

The house was heated with two heat pumps, a large unit upstairs, and a smaller lower efficiency unit downstairs in the offices. A fan heater was also used in the office area. A wood burner was occasionally used in the lounge but had rusted under a leak, and the childrens’ bedrooms were heated with oil column heaters. There was a heat transfer system from the lounge into the master bedroom.

The hot water cylinder, while being under a decade old, was too small for a family of five at 135 litres capacity.

The family wanted to increase indoor warmth and improve energy efficiency. They felt the house had problems with noise, cold and excessive condensation.  They also wanted to modernise the house with lowered ceilings and new lighting at the same time as improving the performance of the house.


The renovation package

Installing double glazing, House 3

House 3 was renovated with a high thermal retrofit with efficient heating and a solar hot water. The major features of this renovation were:

  • lowering the skillion ceilings in lounge, dining and kitchen and insulated with R3.6 batts
  • replacing the roof and relaying existing insulation, R2.6 insulation put over top and over ceiling joists to remove thermal bridging
  • insulating the suspended floor with R2 foil-backed bulk insulation
  • laying under-floor polythene
  • stripping, re-insulating and re-lining walls of thermal envelope to R2.4 
  • re-building pelmets
  • installing a new MEPS compliant woodburner
  • replacing windows with standard clear double glazing and standard frames.
  • installing an evacuated tube solar hot water system and 300L cylinder
  • installing a kitchen rangehood
  • a plumbing maintenance check
  • replacing single flush toilets with dual flush toilets
  • installing a flow restrictor on the shower heads
  • a worm farm

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 1.7°C.  Average winter temperatures in the main bedroom increased by 3.8°C.

These temperatures are given as averages (mean). 

 Looking at graphs of how often each temperature was recorded, the most common temperature experienced in winter in the family room stayed the same  at 20°C.  However, there has been a massive reduction in the coldest temperatures, with the family room never dropping below 12°C, and being above 16°C for most of the time.  The picture is even better in the main bedroom where there has been a ~5°C increase.  The temperature most often recorded in the main bedroom before renovation was 14°C; after renovation, it was 19°C.  As for the family room, there has been a massive reduction in cold temperatures - to the point where time below 16°C has been almost eliminated.

The heavy insulation and double glazing has helped retain the warmth in this home from the use of your wood burner and ducted heat pump system.  The temperature increases occurred even though the efficient heating sources produced substantial reductions in heating energy use.

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 within that range all of the time which is great.

Lower power bills

The family’s electricity use reduced considerably - largely as a result of the installation of the solar hot water system, the heat pump central heating and the improved thermal performance of the home.  Overall they used significantly less electricity to heat their water with a reduction of ~55% in hot water energy use during winter.  They also used less ~62% less energy to heat their home. 

This contributed to an overall reduction in their electricity use of ~33% over winter and ~9% over the whole year.

Water use

The installation of the solar hot water system resulted in the family increasing their hot water use by 21%.  Low flow shower heads have minimised the extra water use, and the free solar water heating has kept power bills low.


What the family noticedSolar panels, House 3

The family report that they are noticing lower electricity bills, and believe that the solar hot water system has particularly contributed to lower costs.  The solar hot water has been very effective for their family use, although they report lower heating costs and seemingly endless supply has meant they no longer feel the need to ask the children to get out of the shower.

The family find that the ducted heat pump system is heating the whole house including bedrooms, and have reduced their use of the wood burner.  They are particularly enjoying using the whole house rather than the previous experience of having to “huddle around the fire”.

The new windows, as well as bringing the benefits of double glazing, have also reduced draughts. They find the solar gain in the lounge with heat being trapped in by the double glazing has improved winter temperatures.  In fact, it is so warm, the family are concerned about potential overheating in summer and have installed sunscreens on the lounge windows.

The problems with condensation have been entirely eliminated along with the mould problem.

The changes exceeded the expectations of the family with benefits they never expected. The double glazing has also made the house a quieter one, reducing both indoor and outdoor noise.  They feel the house is healthier for the whole family to live in, and as a extra benefit, they like the modernised look of the house.  They have enjoyed improved health with fewer colds and flu, and their asthmatic child was able to use an inhaler less frequently.

Our analysis

Although this family’s home is performing well, as measured against the benchmarks of Beacon’s HSS High Standard of Sustainability®, it could still perform better for them. 

The household’s electricity use is still moderate at around 9024 kWh per year.  The benchmark for electricity use is 7300 kWh per year so further improvements could be made.

As a result of the improvements, the indoor winter temperatures meet our HSS High Standard of Sustainability® benchmarks.  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.

As well as the plumbing check, dual flush cisterns were also installed in the home.  The family’s average per person water use was low at 125 litres/pp/day compared to the benchmark of 125 litres/pp/day.

Because of the extent of thermal improvements we made to this home, we also looked at summer time temperatures.  These have increased quite a bit, which is no doubt why the family has been using their heat pump system for cooling.  However, the amount of cooling they are doing may result in their electricity savings being negated, and we think physical measures to reduce the extent of overheating in the home are probably a good idea.  We suggest installing movable sun shades on western and northern windows, and passive vents or security stays to allow windows to remain open during summer for cooling

The underfloor polythene stops dampness rising into the house from the ground, and the rangehood was installed to get rid of moisture-laden air from inside the house.  Addressing indoor temperatures and moisture sources has reduced condensation and mould making a healthier home for the family.  We suggest a bathroom extract fan would assist with the removal of indoor moisture.

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House 3, Papakowhai