Sanctuary: Modern green homes

Cleaner, Greener Hot Water

This is an excerpt from an article in Sanctuary magazine issue 15.

Close coupled or split system? Gas or electric booster?
Solar hot water presents some intriguing choices.

Words Sarah Robertson

Misty Cronin and her family recently built a townhouse in an inner suburb of Melbourne. Solar hot water was just one of a number of sustainable features incorporated into the design by Breathe Architecture’s Jeremy McLeod. With water heating accounting for about 25 per cent of household energy use and solar capable of supplying from 50 to 90 per cent of household hot water demand, Misty was sold.

“It just makes sense, why not? The sun’s out there, why wouldn’t you? It was kind of a no-brainer,” she explains.

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Solar hot water

This is an excerpt from an article in Sanctuary magazine issue 3.

In the average Australian household, hot water accounts for 30% of energy use. Water heating is second only to transport as a households largest cause of greenhouse gas emissions. However a solar water heater can reduce your emissions by as much as four tonnes of CO₂ or more per year—the equivalent of taking a car off the road! By using the energy from the sun to heat water at zero costs.

Depending on where you live and your climate a solar hot water system can provide between 50 and 90 per cent of your hot water needs. The initial purchase price will probably be higher than a similarly sized non-solar water heater but the savings made in energy bills will generally pay for this difference in less than 10 years—in as few as four years in some cases. A solar system generally has a longer lifespan than a conventional unit, so financial returns can be considerable over the life of the system.

This benefit has been recognised by the federal and some state governments and is encouraged in the form of renewable energy certificates (RECs) and rebates. Rebates vary from state to state, but can save you a great deal on the cost of a solar water heater, making them more economically viable.

Flat-panel and evacuated tube collectors

Most solar hot water systems use solar collectors (in the form of panels or tubes) to absorb energy from the sun. Water is heated by the sun as it passes through the collectors. It then flows into an insulated storage tank for later use.

The most common form of solar collector is the flat-plate panel. They consist of a dark coloured, metallic absorbing plate to which a network of pipes is bonded. This arrangement is then placed in an air-tight metal box with a glass cover on the top and insulation on the back and sides to reduce heat loss. As the sun shines on the collector panel the water in the pipes becomes hot due to conduction from the collector plate

In the last few years another type of collector has started to appear on the Australian market. These are known as evacuated tube collectors. They consist of two glass tubes (one inside the other) that are bonded to each other at each end to form a sealed space between them. The surface of the inner tube is coated with a heat-absorbing coating. The space between the two tubes has most of the gas removed from it (hence they are evacuated), which provides a high level of insulation. As solar radiation passes through the outer glass tube and heats the inner tube, it is trapped by the lack of gas, which would otherwise allow heat loss. As a result, the efficiency of these collectors is higher than flat plate collectors, and evacuated tube collectors are suited to colder climates as they even perform well on cloudy days.

Save energy

This is an excerpt from an article in Sanctuary magazine issue 6.

Get a solar hot water system. A solar water heater can reduce the greenhouse emissions of an average family by as much as four tonnes of carbon dioxide per year – the equivalent of taking a large car off the road.

Buy energy-efficient appliances, particularly big-ticket items such as fridges, washing machines, dishwashers and TVs (choose LCD over plasma). For a comparison of appliances, see www.energyrating.gov.au.

Replace your incandescent lights with compact fluorescent or light-emitting diodes. Shun “low-voltage” halogen downlights – these are major users of electricity and require you to put gaps in the ceiling insulation to let their heat dissipate.

Turn off appliances with standby power (evident from the little lights that shine on them even when they’re “off”) at the plug. The “phantom load” these consume while idle can add up to as much as 10 per cent of your total energy bill.

Soak up the sunshine

This is an excerpt from an article in Sanctuary magazine issue 5.

If you want to keep your home warm during winter the first step is to consider good passive solar design and high levels of insulation. If extra heating is required for comfort, solar hydronic heating is often a good option. Solar hydronic heating warms your home by taking advantage of an environmentally friendly energy source—the sun. Hydronic heating systems are typically gas-fired and have been used in Europe for almost a century. Solar hydronic heating systems that use evacuated tube solar collectors as the primary method of heating the water needed for the hydronic circuit are now available on the market.

How does it work?

Solar collectors capture energy from the sun and heat the water in a storage tank to the required temperature via a coil in the top of the tank. If the solar system does not heat the water in the pipes sufficiently, a backup boiler comes on and boosts the temperature. A pump circulates the hot water through pipes around the hydronic circuit, and the heat is transferred into the room through wall mounted panel radiators or through piping laid in a concrete slab floor during house construction. A separate heat exchange coil in the tank can provide domestic hot water for household use.

The backup burner can be run off natural gas, solid fuel or LPG. If you live in an urban area the most economical and environmentally friendly fuel for the backup is natural gas. Solid fuel can be labour intensive and LPG can be up to two and a half times more expensive than natural gas and will significantly increase the running costs of the system.

The components that make up a solar hydronic system are:

• an evacuated tube solar collector to capture energy from the sun
• tanks to store the hot water that is heated during the day
• backup burner which can heat water to a thermostatically-controlled temperature
• a pump to circulate water through the hydronic circuit
• piping that carries the water from the boiler to the panel radiators or to the in-slab pipes and back again for reheating.

A crucial component of the system is the mixing valves, which regulate the water temperature. The evacuated tubes are capable of producing high temperatures, so for safety and reliability reasons it is essential that these temperatures are controlled.

Getting the heat out

Panel radiators are most commonly made of pressed steel and can be installed in existing homes or during the building process. Each panel can be controlled independently, which gives you the benefit of being able to shut off heating in rooms that are not being used.

In-slab piping or ‘foil coils’—made from polyethylene—are generally installed during the building process, but a concrete slab can sometimes be introduced to an existing home during renovations. When considering in-slab piping for your home talk to a concreter who is familiar with your area to ensure that your slab is not likely to shift or crack. The piping can tolerate some kinks and movement, but in-slab piping will not be suitable for all land areas. The piping is usually laid out in a minimum of three zones, which gives you the benefit of controlling heating to only the rooms which are being used. Once heated, the concrete slab floor converts into a radiant heat bank that releases heat evenly throughout an area.

In-slab floors can be tiled or the slab can be finished as a polished concrete floor. Carpet is generally unsuitable, due to the carpet underlay acting as an insulator and preventing the heat being released, but floor rugs can be an option. Timber floors can be laid over in-slab piping. However, the thickness of the wood can impact on heat transference and may also affect the warranty on the timber as the wood may shrink and buckle if it is not already kiln dried.

Setting the scene

This is an excerpt from an article in Sanctuary magazine issue 5.

The road to Michelle and Warwick Marshall’s home was shrouded in a heavy fog that seemed in no hurry to lift. A worrying sign, I thought, considering the entire house design had been driven by the property’s spectacular views. As I left the car, however, the mists began to clear, revealing tantalising glimpses of northern Sydney’s Garigal National Park and Middle Harbour.

Michelle and Warwick have lived on the site since 1999 when they bought a basic, brick-veneer weatherboard cottage. According to Michelle it was like living in a tent—hot in summer and freezing cold in winter—albeit one pitched in a great location.

“We fell in love with both the block and the bushland that surrounds it,” she says. “We’d always planned to renovate to take better advantage of the views, but when we brought our building designer Dick Clarke to the site, even though he prefers to work with the existing structure rather than demolish and rebuild, he reluctantly recommended rebuilding from scratch.”

The views drove the design, but it meant that the building would need to face away from the sun and require a combination of intriguing roof angles to maximise passive and direct solar access. Five years later, the new house sits perched at the edge of a six-metre sandstone platform with balconies cantilevered out into space to capitalise on the outlook to the south.

From the start, an important priority was minimising the building’s environmental impact and maximising its sustainable features, including the use of recycled and sustainable materials wherever possible. The original weatherboard house was given away, while its brick veneer was recycled as fill. Forty per cent of the concrete reinforcing was also recycled.

Building designer Dick Clarke says: “The project faced several challenges, including a council restriction on the height of the building, a structural issue regarding the balcony overhang, and serious concerns about the threat of bushfires, thanks to the home’s position at the top of a bushland escarpment.”

A bushfire’s intensity can double for every 10 degrees of slope, and research has shown that many houses survive the initial firefront only to succumb to burning embers igniting timber decks, eaves, gutters and window frames.

“With this in mind we opted to have no timber on the bush side (the balconies are suspended concrete slabs, rather than timber decks), as well as fire-rated finishes throughout the exterior and windows protected with screen inserts,” Dick says. “A cleared area below the house is also intended to help slow a bushfire’s momentum, while the gutters have been leaf screened, which has the added advantage of keeping the home’s rainwater supply clean.”

A dedicated fire-fighting reserve of 5000 litres of water is maintained at the bottom of the custom-designed in-ground concrete rainwater tank. It also has an outlet that the fire brigade can access in an emergency. The tank itself is concealed under a terrace, but is positioned away from internal floor areas. This provides a thermal break, keeping the cold rainwater away from the living floors. Similarly, the three concrete balconies are disconnected from the main structure of the house at the wall line, providing a thermal break to help control inside temperatures.

Green bathroom renovations, part 1

This is an excerpt from an article in Sanctuary magazine issue 7.

Not everyone can afford to renovate their home or undertake a new build, but most of us at some stage will want to update our bathroom. A bathroom renovation can be as extensive as replacing all fixtures and surfaces, rewiring and plumbing, or it can be as simple as regrouting your tiles.

Archicentre’s latest cost guide estimates comprehensive bathroom renovations cost from $9200 to $24,000, less for ensuites, making a bathroom renovation metre-on-metre one of the most expensive rooms in the house to renovate. So it makes sense to take time to research and plan, to get it right from the outset so that you’ll be happy with the results for a long time.

Once you commit to a green bathroom renovation you need to do your homework. Do the materials, fixtures and appliances minimise or avoid environmental harm during their production and use? Are they made from renewable or recycled materials? Are they made locally? Can they be reused or recycled? With all these considerations you will need to factor in the time it will take to locate, order and deliver each item.

Solar hot water

Renovating a bathroom is a good excuse to have a look at your water heating system and to get it right from the outset if you’re starting from scratch.

There are many reasons to choose a solar hot water system over a conventional gas or electric unit. Probably the most important benefit is that of greenhouse gas emission reduction. A solar water heater can reduce the greenhouse emissions of an average family by as much as four tonnes of CO2 per year – the equivalent of taking a car off the road.

On 3 February 2009 the Australian Government announced a new rebate of $1,600 to eligible home owner-occupiers to replace existing electric hot water systems with solar and heat pump hot water systems. See www.environment.gov.au/energyefficiency for more information. This new rebate is in addition to the Renewable Energy Certificates (RECs) your system may be eligible for – see www.orer.gov.au/swh/index.html.

The initial purchase price of a solar hot water system will probably still be higher than a similarly sized non-solar water heater but the savings made in operating costs will generally pay for this difference in less than 10 years — in as few as four years in some cases. Also a solar system generally has a longer lifespan than a conventional unit, so financial returns can be considerable over the life of the system.

Showers

Showers typically use 30 per cent of a household’s water, so choosing the right showerhead will not only make a huge difference to saving water around the home it will also reduce your water and energy bills. Old style shower heads can use more than 20 litres a minute; new showerheads can give you a decent shower for less than half that.

The government’s WELS (Water Efficiency Labelling Scheme) compares, rates and labels a range of products for water efficiency. Showers rated by the WELS scheme are rated from zero to three stars. Shower heads which have a flow rate of nine litres of water per minute and under are accredited three stars (WELS is testing higher-rating showerheads, but for the time being three stars is tops).

When you’re buying a showerhead, choose the highest star rating but also take note of the flow rate displayed on the label. The WELS website (www.waterrating.gov.au) has a list of shower heads with the lowest flow rate. These include the Astra Walker, with 4.7 litres per minute, and the Quoss system (which is available from most hardware stores) with a 5.5 litres per minute rating. If you’re looking for the more contemporary aesthetic of a larger rose there is the Phoenix with a flow of around eight litres a minute or the Methven Satinjet Kiri and Genesis range (7.5 litres). The Abey ovale range (www.abey.com.au) is an overhead rainshower with seven litres per minute (one of the lowest rainshower flow rates around).

Note that some three-star rated showerheads are not compatible with gravity fed or older instantaneous hot water systems due to the low water pressure or high flow rates required in such systems.

Steer away from showerheads that emit a fine spray of water. The water will get cold quicker, which means you’ll end up turning up the hot water, thereby using more energy, or you’ll need to stay under the shower longer. According to WELS’ Jennifer van den Tol, they are looking at a “comfort test” to help you assess the quality of the showers, but in the meantime you’ll have to do your own homework.

Dick Clarke from Envirotecture likes to design bathrooms with a view to their longevity and easy of use. His ideal green bathroom would be designed with a polished concrete floor with a microtexture finish (to avoid slippage) and with large wall tiles. “By taking away the things that harbour dirt and grime you eliminate the need for cleaning,” says Dick. He also recommends single glass pane showerscreens embedded in the wall and floor to eliminate the need to use silicone. “Keeping silicone out of bathrooms should be a major goal.”

Every Drop Shower Saver

Ever wanted to turn off the water when you are soaping up or shampooing your hair, then turn it back on to rinse, all without losing your temperature settings? The Every Drop Shower Saver allows you to do just that. Available from Flux Research (www.showersaver.com.au). The Oxygenics shower heads from CleverLad (www.cleverlad.com.au) have a similar feature built into them. They have a lever on the side that allows you to turn the water flow down to just 1.5 litres per minute – so you stay warm while using very little water.