House 9

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he was home a lot when not at work. 

Before renovation

House 9, with a single occupant, is a typical two-storey townhouse, built in 1976. The downstairs is clad in sheet material and has a concrete slab floor, while the upstairs is clad in fibre cement weatherboards and has a timber suspended floor. The windows are all single-glazed with older aluminium frames. There is a concrete block firewall between the two townhouses on the western wall. The roof is concrete tiles. Upstairs contains an open plan kitchen, dining and family room area as well as two bedrooms, a bathroom and a laundry. Downstairs has a single internal garage below the master bedroom, a large rumpus room and an unused sauna.

The walls and ceiling of the house were insulated with low levels of older batts, while the underfloor area remained uninsulated.

A fan heater heated the master bedroom, a portable halogen radiant heater and a fan heater downstairs in the rumpus room.

The householder wanted to increase the warmth of the home, reduce cold-related health problems and reduce energy costs. 


The renovation package

House 9 received a moderate thermal retrofit with some other small scale improvements, including:

  • putting a layer of R2.4 batts over existing insulation and ceiling joists to remove thermal bridging, raising insulation to approximately R4.0.
  • insulating timber suspended floors with R2.0 foil-backed bulk insulation
  • laying under-floor polythene
  • installing mid-floor insulation between the garage and master bedroom
  • installing wall insulation on rear of wall to underfloor and garage
  • installing a Showerdome to address mould in bathroom
  • installing a heat pump
  • draught-stopping the sliding door to the garage
  • adding R1.1 hot water cylinder wrap and 15mm pipe lagging
  • using compact fluorescent bulbs in high use fittings
  • a plumbing maintenance check
  • a worm farm

Improvements as a result of the renovations

An easier home to heat

Temperatures in the family room and main bedroom increased slightly between the 2006 and 2008 winters, with a 0.4 °C increase in average temperatures, and the home required less energy to heat.  There was an increase in temperatures between the 2006 and 2007 winters; however, these were reversed in the 2008 winter resulting in an overall reduction in mean temperatures in the living room.  There was also a slight decrease in the mean bedroom temperatures.

The most common temperature experienced in winter in both the family room and the main bedroom has stayed the same.  The temperature most often recorded in the family room, both before and after renovation, was 16°C, and the most common temperature in the bedroom remained at 15°C.  In both rooms, however, there has been an increase in the frequency of warmer temperatures, and a decrease in the frequency of colder temperatures.

Relative humidity levels in the home, while at times elevated, were normally within an acceptable range in the main bedroom.

Lower power bills

The householder’s electricity use reduced quite a lot.  The hot water cylinder wrap was the main contributor to energy efficiency from the renovation.  However, other changes in the occupant’s use of the house, such as the extent of heating, resulted in more energy being saved than the hot water cylinder wrap achieved.   Overall, the householder used significantly less electricity to heat their water with a reduction of 21% in hot water energy use during winter.

This contributed to an overall reduction in their electricity use of ~20% over the winter and ~12.5% over the whole year.


What the householder found

The householder noticed lower electricity bills, which was attributed to lower hot water energy, and was pleased with the warmth indoors during winter.  He reported having fewer colds.

The householder was satisfied that winter temperature problems have been resolved but found that the house overheats in summer.  Cooling actions undertaken were mainly opening windows; the heat pump was not used for cooling.

The heat pump was set to start 15 minutes before arriving home from work.  Unless it was really cold in the weekends, it was not reportedly used.  The householder only used a fan heater in the mornings in the bedroom (rather than switching the heat pump on).

The Showerdome reduced mould in the bathroom and the householder reported that he didn’t need to use as much hot water.  However, a tall visitor had some trouble breathing in the shower with the Showerdome.  When combined with the fan in the bathroom, the Showerdome resulted in little to no mould in the bathroom, although thre was still some condensation on the windows.

The householder reported that he would look for good insulation and double glazing in any future homes, and that the experience had taught him the value of trapping the sun.


Our analysis

Electricity use has reduced to 4,900 kWh per year which is quite low and compares well to the benchmark for electricity use of 7300 kWh per year.  Further reductions in electricity use could be made by upgrading the fridge/freezer and chest freezer with a modern, energy efficient appliances, and by installing a solar hot water system.

The temperatures in this home in winter are still lower than the HSS High Standard of Sustainability® benchmark.  The average minimum winter overnight temperature was 15.5°C in the main bedroom and the average minimum winter evening temperature in the living room was 16.9°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.  Of particular note are the relatively small fluctuations in temperature within the home - likely to be a result of the ceiling, wall and floor insulation keeping the temperature relatively even throughout the day and night.  Given a heat pump is the main heating source, efficiency of heating method doesn’t appear to be an issue.  From the data it is clear that heating energy used in this home is very modest, and that is the major reason why the home does not meet healthy indoor environment quality indices.  Occupancy interviews indicate that the homeowner does not feel that the home is inadequately heated and that it is perceived as comfortable.

We suggest installing double glazing, or secondary double glazing, on southern windows to further retain heat.  To reduce overheating, we suggest installing shading (such as an awning) on western windows.

Relative humidity, the percentage of moisture in the air, is recommended to be between 40% and 70%.  Relative humidity levels were only above 70% occasionally - about a tenth of the time - and are linked to cold indoor temperatures.

Apart from the plumbing check, no measures were undertaken in this house which would be expected to impact on water use.  Average water use was 193 litres per person per day, compared to the HSS High Standard of Sustainability® benchmark of 125 litres per person per day.

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House 9, Papakowhai