After more than a decade scrutinising and writing about environmentally sustainable design and building products for the magazine, Warren McLaren bravely turns the microscope on his own retrofit project.
My printed copies of The Last Straw, an international journal of straw bale and natural building, commence with Volume 1, 1993. I participated in one of the earliest practical workshops on strawbale construction in Australia. I worked for five years in Australia’s first commercial strawbale building. So, where do I live? In a cosy, earth-rendered home of straw? Alas, no. Instead, I reside in the proverbial triple-fronted, brick veneer house, complete with a black tile roof! It rankles.
But sometimes, real life trumps daydreams. When my wife and I moved out of Sydney to a country village, my choice of rural location won out. In balancing the ledger, she got the type of house she wanted. Having previously built two homes from scratch, she pined for something she could just walk into, without needing to lift a finger. And who is going to argue with a pregnant woman?
With my long-held vision of building a strawbale home left unrequited, I needed to embrace a new challenge. Was it possible to green the basic, stock-standard Aussie house? Without a mortgage, or a loan?
Well, we’ve given our best shot. In fact, the only renovations we’ve made in the past six years have been solely about making our home more comfortable for humans, whilst being less of a burden on the broader environment.
Our new home was the epitome of Australian house vernacular, especially for the end of the last century, when it was built. However we did inherit a few saving graces, such as blown cellulose insulation in the ceiling, a slow combustion wood heater, ceiling fans in the bedrooms, a north facing aspect and eaves sized correctly to block summer sun from entering windows.
What then have we done to up the ante on these few scant eco-credentials, and improve the liveability of our abode?
Firstly we replaced the original carpet (a rapidly wearing polypropylene) with a more durable all wool berber. We had also tried to go with a natural jute underlay, such as Tontine’s Wunderlay, but our carpet company was rather recalcitrant and wouldn’t come to the party, saying they didn’t have any experience with such products. In the end, a recycled foam underlay was used beneath.
Nearly all of the north and south facing windows are floor-to-ceiling panes of ordinary 3mm glass. The Your Home Technical Manual reckons up to 40 per cent of a home’s heating energy can be lost, and up to 87 per cent of its heat gained through windows. Obviously the fenestration in our abode was completely unsuited for the Southern Highlands of NSW, where it snows briefly every few years, with temps easily dropping to −8°C during the winter, and summer highs nudging 40°C.
Your Home Technical Manual gives advice on glazing in such regions: “… double glazing is recommended in this climate because on each winter’s day there are 19–20 hours of heat loss through glass with a maximum of 4–5 hours of heat gain.” We would’ve loved to have replaced all the windows in the house with funky new double-glazed windows, but there were three reasons why we didn’t: embodied energy, inconvenience and cost.
New double glazed windows aren’t cheap, especially when we planned to upgrade every window in the house—bar the wet rooms.
Our compromise was retrofitted double glazing: Magnetite. Optical-grade acrylic panes are fitted with magnetic strips that seal with a resounding ‘thunk’ onto a mini-frame of quad-like plastic that has been mounted into the window reveal.
Using data from the Australian Window Association’s Window Energy Rating Scheme (WERS) Magnetite suggests that a retrofit such as ours improves the U value of windows by 40.3 per cent. Visitors to our home reckon, anecdotally, that it has added about 8°C to the inside warmth during winter.
To further mitigate any night-time loss of heat, we installed curtain rails and fully enclosed curtain pelmets around the top of window architraves. Of course, windows are but one element of the building shell. There is next-to-nothing that’s thermally efficient about brick veneer walls and they are rather awkward to insulate once construction is finished. We briefly considered the notion of taking off the plasterboard and lining all the walls with batts. Those three nemesis of embodied energy, inconvenience, and cost again quickly quashed the idea.
I did toy with the idea of covering the external brick walls with sheets of corkboard insulation by Portugal’s Amorim Isolamentos. But with Australian suppliers very thin on the ground, we decided our fledgling family couldn’t afford the expense and risk of experimenting with something so left-field.
In the end we settled on Insulabloc. This is expanded polystyrene foam sliced into little 1cm cubes. The product has a high recycled content and is made in Australia. Insulbloc Australia provided test results from the Australian Wool Testing Authority (AWTA) showing Insulbloc garnering a thermal insulation rating of R4.0 per 100mm thickness. It was installed by removing tiles above the cavity wall and blowing the tiny blocks into the wall void with a big reverse vacuum style hose. Insulbloc suggest such a finished insulated wall is equal to about R6.
Above and Below: Insulbloc is easily pumped into existing brick veneer cavity walls to offer an insulation rating of about r4.0 per 100mm.
The wall between lounge and garage was an uninsulated stud wall with plasterboard on both sides. Here a hole saw cut openings for the Insulbloc to be inserted while a thin sheet of insulating batt was positioned to keep the cubes in place until I got around to plastering the cutouts back in, and repainting.
In the roof we already had the blown cellulose that was in-situ when we moved in. To supplement that, we self-installed two layers of R2 Tontine Thermal Batts . These batts are made of soft, non-itchy thermally bonded polyester fibre with 83 per cent recycled content.
These efforts on the building envelope have greatly improved the comfort of our home. We reconfigured the open plan nature of the house by adding three timber-framed glass doors to the lounge room. These allow us to control heat flow and noise.
Alas, that ghastly black tile roof remains, and is, I believe, the greatest contributor to heat ingress into the house during summer. Having said that, after Aussie Solar installed a 2kW solar array of 12 photovoltaic panels we shaded a significant portion of the north facing tiles. Thirty evacuated tubes from the gas boosted Hills Esteem solar hot water system shade another part of the roof.
Rain Harvesting’s Advanced Leaf Eaters filter out gutter debris as precipitation is diverted to our 27,000 litre rainwater tank, and a Davey RainBank pumps rainwater from the tank to our Bosch front-load washing machine , laundry, toilet and yard taps irrigating our nine veggie beds and 30 fruit and nut trees.
Above: Davey Rainbank
Below: Rain Harvesting Advanced Leaf Eater
We have also picked the usual array of low hanging fruit for a green retrofit. Lighting is now either compact fluorescents or LED strips and globes. External doors and yard gates are lit with motion-sensor, solar-powered LEDs. Our east-facing windows have removable shadecloth screens to reduce the heat gain of the summer sun. A large shade sail is erected each summer over the north facing wall, to similarly keep old Sol from throwing his heat onto the bricks there. We replaced the energy guzzler of electric stove with an Omega induction cooktop. Being highly energy efficient, it has the instant heat of gas, without the attendant dangers of naked flames and non-combusted, unflued gas.
What is still to be done? A massive amount. I’d love to cover those black roof tiles with a light coloured reflective paint, or at the very least install a sun-powered, hot air extraction fan, like the SolarWhiz. If the grape and passionfruit vines turn out not to be successful summer wall screens, then we may need to bag or render the external brick walls, also with a light coloured reflective paint. Very average vinyl flooring in the kitchen and dining area is scheduled to be replaced, probably with cork. Some dark spaces would benefit from a solar powered ‘skylight’, such as the Solaro Day or Kimberley Illume, which both avoid issues of heat gain usually associated with skylights.
However, the piece de resistance may well be a renovation of the double garage into a guest bedroom and extra living space. This will require the current work bench and tool storage, currently domicile in the garage, to relocate to new premises, resulting in a new workshop being erected in the backyard. Maybe strawbales will get a look in, after all. One can but dream.