Sustainable Wanaka Wastebuster
Friday, August 08, 2008
New Zealand homes have historically been extremely inefficient: 30 years after insulation became mandatory, around 350,000 homes are poorly insulated or have no insulation at all. Many of those are in the Queenstown Lakes District, where many houses were built for summer use only but are now lived in year round.
In addition to the insulation problem, the cost of energy to households has risen in real terms by 16% since 1995. Owners of thermally inefficient homes are paying more year on year to heat their homes or are accepting inadequate levels of heating to keep the cost down.
At Alexa Forbes' house in Frankton, there are many examples of energy efficient measures which have made their old villa more comfortable, livable and cheaper to run. She and her partner Sean Drader have spent the last 5 years adapting the old house, including removing internal walls to make an open living room, adding large windows to the North, retrofitting insulation in the ceiling and floor, installing solar water heating, a heat recovery ventilation system and thermal blinds.
However, some parts of the house are still very cold in winter and Alexa called me for advice on how to improve it further. The 'Eco Design Advisor' scheme, which I provide through Sustainable Wanaka, is a free service for homeowners, designers and builders wanting advice on any aspect of sustainable building: healthy materials, passive solar design, energy and water efficiency, renewable energy and landscaping, to name a few of the main issues.
The North facing side of the house, showing new glazing and solar panels
Alexa and Sean converted 6 small rooms into one on the North side of the house and opened up the entire North wall to the sun. They laid a stone floor in the 2 metres adjacent to the glazing (using stone from Arrow Junction). This 'thermal mass' absorbs the sun's heat and, although it doesn't feel warm, regulates the internal temperature of house by storing the sun's heat captured during the day and re-releasing it at night. It also helps keep the house cool in Summer.
The new windows are double glazed 'composite' windows – timber frames (for warmth and resistance to heat loss) on the inside and aluminium on the outside (for durability and stability).
The Yunca fire does a good job of heating the house and also provides a back up to the solar for water heating. Alexa says there are only 3 months in the year when they use any electricity for water heating. Her solar panels were installed 5 years ago when experience of solar in the industry was generally minimal. However, some initial glitches aside, the solar is now working very well. I suggested insulating the pipes that run between the fire and the cylinder above and adding a cylinder wrap, to minimise heat loss.
The living room, showing alterations such as the stone floor, North facing windows, and thermal blinds
Ceiling
Alexa and Sean installed extra insulation in the ceiling, which has helped save money on power bills and made the house feel warmer. They have done a good job, installing the insulation tightly between the joists without compressing them. However, I discovered a few gaps in the insulation which need to be filled in. It is worth noting that even a 2mm gap around the edge of insulation batts can reduce the 'R-value' (a measure of a material's resistance to heat loss) by around 20%.
I also advised Alexa to add a second layer of batts over the top, running perpendicular to the existing batts. This will cover up any gaps in the bottom layer and cover the joists, which transmit far more heat than the insulation that surrounds them.
Alex resisted having recessed downlights fitted in the living room during the renovation. Recessed downlights, favoured by electricians for the uniform light they provide, are inefficient for several reasons. Firstly, they require a aperture to be made in the insulation, which compromises the thermal integrity of the building,and secondly, the heat they generate causes warm air to rise from them which pulls warm air out of the living space below. If the living space is a kitchen or bathroom this air is damp and the moisture condenses in the roof space. While recessed downlights create uniformly lit spaces, they are not a sustainable lighting option.
Well fitted insulation
Gaps can be seen beneath the heat recovery ventilation system
Floors
Uninsulated timber floor, showing the floorboards from beneath
If you are doing this yourself, be careful as several people have electrocuted themselves by stapling through electrical cables while installing foil insulation under houses. Sean had to contend with white tail spiders and cat poo – it may be worth employing someone to this for you!
Heating
The heat recovery ventilation system has proved to be failure. The system is designed to extract warm 'waste' air from the living room and use it to preheat incoming fresh air from outside, which is then ducted into the bedrooms. However, Alexa says that even when she holds a fan heater to the extract vent in the living room, no heat arrives in the bedrooms. I suggested removing the heat exchanger as it is obviously not working, and convert the system to a standard heat transfer system, in which heat is extracted from the living room and ducted directly into the bedrooms. New heat transfer systems can be bought from hardware stores or from specialists companies.
Windows
Most of the windows are old single glazed timber sashes (the new french doors excepted). These are loosing a significant amount of heat and make the bedrooms uncomfortably cold. I suggested fitting 'secondary' glazing, which is effectively a second, single glazed window, fitted internally within the existing reveal. These could be fixed panes -which are cheaper - and can be removed in Summer. The principle is to create a still layer of air between the window and the room – it is the air which is the insulator in double glazing. Old windows – or any windows for that matter – can be improved by fitting well-fitting blinds or curtains which also provide a still layer of air: good curtains can effectively make single glazing perform the same as double glazing. This is why it is so important to close curtains at dusk. I also suggested fitting draught-strip to opening windows and fixing gaps in the frames of fixed panes.
Sustainable Living
Alexa has implemented a number of sustainable living measures, beyond the alterations to the house. She and her neighbour share a chicken house (with very happy occupants), a vegetable garden, a compost heap and greenhouse. Both houses have their own private outdoor space, but they share these parts of the garden, saving them both space.
Each 1% improvement in energy efficiency in New Zealand Homes will result in $17 million of savings and reduce the country’s CO2 emissions by 0.1%. Little changes such as those made by Alexa and Sean - and the changes they will be making – will make a big difference to your comfort, your heating bill and your environment.
The Eco Design Advisor is an initiative of BRANZ and in this district is funded by QLDC, Ministry for the Environment and EECA. Sustainable Wanaka project manage the service. To make an appointment, contact Jessica Winter on 0275837444 or at jessica@sustainablewanaka.co.nz