'Tip 6' for Direct Action: Solar efficient no-grid home, built by...?

*This is the sixth part in a series of 'Tips for Direct Action'. Click here for parts one, two, three, four and five.

Could you imagine a house with just one small $500 heater that uses less than half the annual electricity of a fridge? A house that's so efficient that with a small battery system (now available from companies like ZEN Home Energy Systems) could operate through winter, even in cloudy Melbourne, without being connected to the electricity grid?

This is a house that we should all be able to own and on Friday last week I visited Ewan, the proud owner of such a house located right within Environment Minister Greg Hunt's own federal division of Flinders, on Victoria's Mornington Peninsula.

This home isn't some boutique, architect designed fandangoed building, either, It's a stock-standard volume-built house that was upgraded (mostly through checking boxes in a 100-page catalogue) from Henley, a large scale house builder better known for their McMansions than environmentally friendly builds.

In the coldest months of June, July and August this Henley nine-star house required just 385kWh of heating input. Utilising a standard LG 3.2kW split system reverse cycle air conditioner (COP of 5.42) that monthly winter heating requirement can be delivered with just 71kWh which due to the thermal mass isolated inside the building can be run overnight on the off-peak tariff ($8.50 per month).

And what did it cost?

The Henley house had a $220,000 base price and for just 15 per cent ($35,000) more it was upgraded to barely require a heater (coming in at just under 10-star). However, this cost is offset by not plumbing and connecting gas, about $5000, and not installing an evaporative swamp cooler and a large gas heater, about $8000.

The current one-off upgrade price would be between 30-50 per cent more expensive than if Henley or any large volume builder included these features as standard in all their new homes.

Being smarter about your space

One way of looking at the upfront capital cost difference is if the floor area was reduced from, say, 220 to 200 sq m – then the upgrade would be cost neutral to the customer.

The savings

From $500-1000 per year compared to a paper rated but untested large new development six-star house. And a much more comfortable house than can be achieved even after throwing a whopping great big heating and air conditioning system at it as a kludge fix to lack of build quality, draughtiness and poor insulation.

So what was done?

1) Orientation

This bit of the equation didn't cost anything but you have to have a site that will allow you to run the living area and master bedroom along the north side. There is a problem in many developments that do not have block sizes to allow for this, and that needs to be fixed up at the local/state government planning stage (though there's always an opportunity for 'direct action' lurking in every corner).

2) Eaves

The standard volume built house doesn't have much in the way of eaves. Eaves were pushed out all around the perimeter in order to shade the houses ample north facing glazing in summer, a further saving for the budget conscious could be had by only opting for the eaves on the north side.

3) Glazing

Glazing was upgraded with Argon filled DGUs (double glazed units) 6-8mm glass 12mm air gap, which cost around $8000. By using double glaze units its the same in terms of energy losses as halving the amount of glazing while maintaining solar gain with north facing glazing. If the volume builder could offer triple it would be like reducing the glazing (again from a losses perspective) to a third. With these savings a large amount of north glazing can be present maximising the solar gain in wintertime to reduce the need for heating. Southern Victoria is a heating climate with 80 times the energy used for heating versus cooling.

4) Walls

The exterior bricks were dropped and replaced with Kingspan Kooltherm5 R4.0 phenolic insulation boards which were then rendered for the final finish. Now in my book this should have saved money rather than cost more as bricklaying is a very laborious, time consuming and costly task, not to mention that firing bricks is incredibly energy intensive.

5) Insulation

The Kingspan boards mentioned above are cladding the walls ready for rendering at R4.0 combined with the standard R2.7batts, between the studs in the walls. The roof has R6.0 batts installed between the ceiling joists carefully laid to make sure there were no gaps combined with an R1.5 blanket under the rooftop corrugated iron.

6) Air leakage

A very important part of the job was in regards to air leakage. The house was air pressure tested and sealed up in a way that is standard in Europe and exemplified in the Passiv Haus standard. This was performed by the team at Victorian based Air Barrier Technologies and cost $1200 and in practice meant that air would not get in between the slab and kingspan boards, around windows and doors,\ and especially around the penetrations made by plumbers and electricians behind kitchen sinks, the stovetop and oven. Architraves, kickpanels, light and power switches were also sealed. Just above the walls between the ceiling and the roof inside the roof cavity was sealed as air movement across bulk batts significantly derates them. 

7) Heat recovery ventilator

Once the house was sealed up to 1.1 ACH50 (about 0.05 ACHnat) a Mitsubishi Heat Recovery Ventilator was installed (around $3000 and a 40 watt average fan). The unit has four small ducting port holes in the wet areas and kitchen which draw air and remove it through the HRV's heat exchanger. At the same time fresh air is brought in, heated up and filtered by the HRV and then delivered to the living areas and bedrooms. The only direct connection to outside is a rangehood (that includes a damper) located directly above the stove top. The decision was made to bypass the HRV for the rangehood to avoid the heat exchanger/filters from getting clogged up.

8) Hot Water

The house has a evacuated tube solar hot water service which the owner may consider coupling with a heat pump hot water unit to increase the renewable share of hot water from 75 per cent to 90 per cent-plus.

9) Solar photovoltaic system.

The house has a 10kW solar photovoltaic system with 2xSMA 5000tl-21 inverters and LG 250 watt panels which cost $14,000. Similar sized systems have been installed around Melbourne for up to $2000 cheaper, however the owner wanted to be comfortable with the company that he engaged for the work. This solar system will wipe out all the household's daytime energy use and allow for the addition of a battery storage system at a later date when the costs come down a bit more (costs are forecast to drop 30-50 per cent in the not-too-distant future).

10) Cooking

An induction cooktop obviously. they're quite straightforward and the public is becoming much more familiar with this technology as being the best cooking platform for aspiring chefs!

The missing ingredients to make it 10-star?

An upgrade from double to triple-glazing and edge slab insulation might get this house to a point where it doesn't require a heater. Both are attainable upgrades and wouldn't add significantly to the overall build cost. I'm sure there are other opportunities to improve on the cost equation and comfort level and the best way to do that is to get on with the job and build 10-star houses, like Ewan's, en masse.

Back to Greg Hunt, business and Direct Action

For business: So Henley (and all the other volume builders out there) what about advertising a nine-star or, even better, 10-star model front and centre in your standard catalogues?

For Greg Hunt and the Coalition: How about meeting with Henley's sustainability people and visiting Henley's nine-star home that is sitting smack-bang in the middle of your electorate and find a way for all of our volume built homes across the country to meet this standard. Can cost of living pressures meet Direct Action for more comfortable energy and hip pocket saving homes?

Matthew Wright is the executive director of not-for-profit Zero Emissions Australia to volunteer goto the website