SOLAR HEATING
The roofs of Aussie houses are becoming increasingly cluttered. This bulletin discusses the types of water heating systems now commonly found on house roofs, and possible design standards to regulate them.
Solar hot water tube array systems
Solar hot water systems have two main components – an array of black tubes to heat the water, and a tank to store the hot water. The array of tubes come in two types: glass covered panels, looking like PV panels, and exposed pipes. The closer the storage tank is to the array, the less heat loss and so the more efficient the system is. The more people living in the house, the larger the tank needs to be, and the larger the array. The tank can be placed on the roof, typically immediately above the array; in the roof space; or on the ground. On the roof is easiest and cheapest, but also the most visible. Within the roof space is more expensive, harder to access, and may cause significant damage if the tank leaks. On the ground is the least efficient, but easiest to access, and leaks are unlikely to cause much damage, if any.
Solar hot water tube array systems may include glass covered panels or an exposed arrays of pipes. The associated hot water storage tank is most efficient mounted directly above the heating pipes, but also the location is most unsightly.
Thermodynamic panels
Thermodynamic panels can be used with a heat pump as an alternative to a solar hot water system. They work if the air temperature is at least 15 degrees Celsius. As they absorb latent heat, not sunlight, they can run day and night. They can be mounted on any surface exposed to the outside air, including roofs and walls, whether in sun or shade. A thermodynamic panel heat pump system is more efficient than a solar hot water system, but is also more expensive to buy.
Thermodynamic panels can be mounted to any surface including walls and roof. They absorb ambient heat and so do not need sunlight.
Flexible solar water heating piping
Flexible black piping on the roof of a house can be used to heat water for space heating, hot water, and for heating swimming pools. Space heating is achieved via hydronic panels or under floor heating. Compared to PV panels, solar thermal heating needs a large roof area in direct sun. Due to the large area covered, and the contrast of the piping with the underlying colour of the roof cladding, these systems tend to be more unsightly than other solar water heating systems.
Solar water heating piping stands out over the underlying colour of a roof.
Black piping is less conspicuous on a dark roof.
Issues and potential controls
Water heating panels and pipes can look unsightly and can add to the number of disparate elements on a roof, making it cluttered. Water tanks can be especially unsightly. An estate’s design code and design review panel might take into consideration many factors when considering the placing of panels and pipes on a roof or wall.
“As standard solar panels are considered unsightly, they may be installed on roof faces that do not directly face the streetscape. When connected to solar hot water systems, no associated on-roof water heaters, tanks or plant will be permitted.” (Heritage Estate, Chirnside Park, Victoria)
If a house’s north or west facing roof planes and walls also face the street, the optimal locations for panels and pipes may be detrimental to the streetscape. To minimise their prominence, panels may be placed on the rear part of the house, be colour matched to the roof or walls, or be low profile.
“PV panels and solar water heating system panels may be installed flush on the roof except on the face closest to the street. Tanks associated with the water heating panels must not be on or above the roof.” (Atticus, Woodstock, Victoria)
For resource efficiency reasons, some estates require their installation.
“A solar hot water system, including roof mounted collector panels, must be installed.” (Bankside, Rowville, Victoria)
While solar heating panels and pipes may be seen as eyesores, they are becoming more common on new Australian houses. Estate developers need to decide how restrictive to be regarding the placement of these panels and pipes. An estate’s design code might allow panels and pipes anywhere on a roof, restricted to less conspicuous areas, require only solar panels, or ban panels and pipes altogether.
