House 6

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Before renovation

The sixth house, owned by a semi-retired couple with adult children often at home, was built in the 1970s, and has a living area of approximately 190m2. The house is mainly of timber-framed weatherboard construction, with some sheet cladding around the lower part of the house and concrete block around the family room extension. The roof is concrete tiles, and the foundations are concrete slab beneath the garage and family room, and timber suspended floors under the rest of the house. Half of the windows on the southern side of the house are newer aluminium, while on the northern side they are a mixture of older aluminium and timber.

The ceiling cavity is insulated throughout with batts, but the insulation is patchy and was poorly laid. The house also has downlights throughout, creating holes in the insulation throughout the house, causing additional heat loss. The occupants have insulated the floor below the lounge, which is the ceiling of the garage. The batts have been pushed into place, and have folds and gaps throughout the cavity. The rest of the underfloor is not insulated, nor are the walls.

The home is heated with a woodburner in the family room, oil column heaters in the bedrooms, and a portable LPG heater is moved where it is required.

The householders wanted to improve the warmth and dryness of their house and increasing its liveability into their retirement. One bedroom was persistently damp and cold, and had affected the health of a daughter sleeping there. They also saw the project as giving them ideas on what they could do to with the house to both increase its thermal performance and to increase its value.


The renovation package

House 6 was originally to be the control house for the project with no interventions at all.  However, as House 4 changed hands and was no longer part of the research, House 6 received a basic ceiling top-up, the equivalent of earlier government subsidies.  Data from this house enabled us to show that the basic subsidised level of insulation was not adequate to improve homes and has helped us to lobby government for higher subsidised levels.  The top-up included:

  • topping up the ceiling insulation with R2.6 to reach approximately R4.0
  • wrapping the hot water cylinder
  • lagging the hot water pipes


Improvements as a result of the renovations

Initially some slight improvements in temperature were made but, after the second winter, reductions in heating led to a colder home.  Average temperatures in both the family room and main bedroom dropped.

The temperatures are given as averages (mean), and as the overnight temperatures are low, it brings the average temperature down.  The most common temperature experienced in winter in the family room and bedroom remained at 14°C.  The most common temperature in the master bedroom dropped a degree - moving from 14°C in 2006 to 13°C in 2008.

The drop in temperature was a result of heating the house less in 2008 than was done in 2006, which may, in part, be due to the house being uninhabited for some of the year.  While the house had some insulation improvements, these alone won’t make a house warm, but they will help keep heating from escaping outside the house.

Relative humidity remained below healthy levels, and this dwelling performed worst of all of those in the study in relation to both humidity and temperature. 


Lower power bills

The household’s electricity use did reduce (11%) - largely as a result of reduced hot water use and changing occupancy. Total annual reticulated energy reduced from 7100 kWh/year to 6300 kWh/year.

Wood burner use for heating also reduced.


What the householders found

Unsurprisingly the household found little improvement from the basic top-up of insulation, but some small improvements in water heating costs from simply wrapping cylinder and pipes. They were relying on electric blankets and spot heating as they felt they couldn’t heat the house adequately.   They were disappointed not to have had a more extensive renovation.

The householders tell us what they really need is information on how to improve the comfort and energy efficiency of their home. They were prepared to spend money to put the house right but wanted to know what interventions were likely to give them the greatest ‘bang for the buck’.


Our analysis

Knowing what to do and where to spend your money to improve your home is a common problem.  All too often, homeowners install expensive technologies first before addressing the basic problems.  This is one of the reasons for the Papakowhai Renovation project – to find out what will give the ‘biggest bang for the buck.’  The next step, HomeSmart Renovations, will focus more clearly on providing information and advice for homeowners and developing a renovation pathway individualised to each home and family.

Although limited, this basic renovation has been useful in showing that even a simple and cheap intervention, such as lagging pipes and wrapping cylinders, can have an effect on power bills.  Equally, to get healthy indoor temperatures, much more than ceiling insulation is required.

While the household’s electricity use is low, temperatures and humidity levels in the home could improve a lot.  Both the family room and the main bedroom remain below the HSS High Standard of Sustainability® benchmarks.  The average minimum winter overnight temperature was 13.7°C in the main bedroom, and the average 24 hour winter bedroom temperature was only 12°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 the next step for insulation is the walls, starting with the main bedroom and the lounge.  Because all but one of the bedrooms are on the colder side of the house, we suggest that insulating any bedroom which is going to be occupied.   Where the exterior walls are concrete block, installing polystyrene insulation will help prevent heat escaping through the wall into the bank from the family room and the wood burner.  This can then be rendered with plaster.  Draught stopping windows and using thick thermal curtains are relatively cheap ways of preventing heat loss through windows.

This household significantly under-heats the family room, even in the evening, with only minor increases in temperature.  Living in cold homes is associated with greater likelihood of respiratory illnesses, colds and flus.  We suggest the household upgrades their heating, by either using their wood burner more, or looking into buying a heat pump.  A heat transfer system can take the heat from the room with the wood burner to the bedroom, provided that the wood burner is used more often so there is excess heat to be transferred.  Alternatively install a new efficient wood burner in a more central room in the house, so that the heat is better spread around the house.   If the family don’t use the wood burner a lot, we suggest buying a heat pump

Relative humidity, the percentage of moisture in the air, is recommended to be between 40% and 70%.  Relative humidity levels were tested in July and found to be above 70% almost all of the time.  Relative humidity is linked to the cold indoor temperatures, as cold air holds far less moisture than warm air.

There are a range of things which we think are contributing to the dampness of this home.  As well as needing more insulation and better heating, 25-30kg of moisture rises up from the ground underneath a house every day - a polythene vapour barrier can stop this at relatively low cost.   It is also important to get rid of moisture from bathroom and kitchen use - a rangehood in the kitchen will vent that moisture outside.    The family’s unflued LPG heater will also be adding a lot of moisture to the home.  For each hour these heaters run, they add 1 litre of water into the air, as well as a range of toxic gases such as carbon monoxide and nitrogen oxides.  We strongly recommend the household get rid of this heater. 

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House 6, Papakowhai