Dec 2013: A sustainable renovation and extension

Fitting strong ideals into a limited budget –a sustainable renovation and extension

The challenge

Like many new home buyers on a limited budget, Alex and Luke Wilkinson had to decide how to achieve their goals of living sustainability whilst being restricted by a rather limited budget. Their choices were further limited because they wanted to live in Inverloch where property values are not cheap.

The solution the beginning

Alex and Luke’s solution has been to buy a basic holiday home on a suburban block and use the rest of their funds to carry out renovations and build an extension which have substantially improved its ‘green’ credentials. This was a challenge because the house they bought had no energy efficient features to speak of. It was cold and draughty in the winter and hot in the summer, and orientated to the west– certainly not a comfortable place to bring up a young family. 


The first step was to block as many draughts as possible in the existing rooms and then insulate as much of the shell as they could. The simplest place to start was in the ceiling and so they put in batts with a R4 rating throughout to have the maximum effect. Insulating under the floor was harder but possible. So Luke spent several rather uncomfortable hours crawling between the stumps attaching concertina foil insulation with R2.4 rating to the bottom of the floorboards. This improved the performance somewhat but it was not until it was possible to fit wall insulation as part of the renovation / extension work that a marked change was apparent.

Extension and further renovation

The extension was planned to give the Wilkinsons a family room and at the same time they took the opportunity to rearrange the layout in the existing building to make the most of the northerly sun in Winter. The result has been to produce a much more open planned house which uses space more effectively and allows easier flow of movement between different areas in the house. It also means that natural cross ventilation of air is possible so that sea breezes can be used to keep the temperature down on hot summer days. As part of the renovation they also introduced a double-glazed, north facing window which brings sunlight directly into the main part of the original house for the first time.

The extension was only possible on the South end of the house which means it has been difficult to incorporate passive solar principles into its design. However, thoughtful planning has meant that sunlight from the North can enter directly into the room through windows placed at the top of the high walls which extend up above the original building. The room has thermal mass in the form of a concrete slab and a brick wall on one side. This, in conjunction with double glazed windows and well insulated walls, ceiling and floor means that it retains much of the heat that enters it.

There is also a slow combustion stove in the room which is only required on cold winter nights and is the main heating for the whole house.

Preliminary research (useful websites)

Luke carried out considerable research and planning before the final plans were ready to be implemented. He used magazines such as Green, Sanctuary and Owner Builder (available at the local library) and also found two websites that were particularly valuable. The first is Google SketchUp, a free software program which allowed him to plan possible designs and then view them from all angles in 3D. Using this program, Luke was able to draw up a number of possible designs for the extension and then select the most appropriate and practical one in consultation with his designer, Derek Ashby from ehldesign. (If you want to find out more, SketchUp is obtainable free from .)

The second website that was used is Ecospecifier (at ). This lists 5500 products, materials and technologies and rates their sustainable credentials. In particular, because the site shows what certification each product has received, if any, the Wilkinsons were able to decide whether claims made about any product were valid or whether they were an example of ‘Greenwash’. This was particularly useful in helping them to select materials which had genuinely low environmental impact, one of their three main selection criteria. The other criteria were to use local suppliers where possible and reuse existing materials were possible.

Environmentally friendly materials, appliances and fittings

With the assistance from Ecospecifier and their other research, Alex and Luke were able to choose the following materials, appliances and fittings:

  • The timber used to clad the extension and two of the walls of the existing house has been sourced from plantation timber which was radially sawn (to reduce wastage) and was grown and milled locally in Yarram
  • they have used low VOC paint, flooring and adhesives from a local outlets
  • the lights are low wattage LED’s sourced locally
  • all new appliances have been chosen for their energy and water rating using the website,
  • a 3.4 kW array of solar cells has been installed, which was obtained from and fitted by a local electrician, John Cutriss
  • A solar electric hotwater service installed by EcoSmart, Inverloch

Owner builder

Alex and Luke registered as owner builders. This meant they took responsibility for sourcing materials; their decision was assisted by the fact that they chose a local builder they knew was environmentally conscious and were comfortable consulting.  This was Chris Ball who Luke had worked with one other sustainability projects such as the Inverloch School Garden.  Chris shared Alex and Luke’s values of environmentally sustainable design and construction and proved valuable in looking for opportunities to promote a small environmental footprint, avoid waste and promote use and recovery of resources.