Grass roofs aren't the only way of topping a home in an environmentally-friendly way. Solar systems are now being integrated into the roof to provide sophisticated home heating and cooling. And tyres from old cars could also be going up in the world.
Ambient Energy Systems has launched an ultra green whole-house heating system that promises to turn conventional SAP calculations on their head. By marrying three diverse technologies together, the system is capable of delivering virtually all the heating requirements of a house with no more than a couple of 100w circulation pumps, augmented by occasional use of a 2kW heat pump.

Underfloor heating is preferred over radiators and the system can provide summer cooling - both features that may appeal to upmarket housebuilders. The capital cost is estimated at less than £2000 per house.

How does it work? Rather than using solar panels in the conventional sense, the roof covering itself is made of hollow aluminium extrusions through which is pumped a heat transfer fluid. The roofing material looks similar to a conventional slate covering, though it is actually a series of interlocking planks.

Because the system uses a heat pump, the flow into the roof can be controlled so that it is always colder than the return which means that the liquid in the roof will always be able to absorb usable heat from the external air, even at sub-zero temperatures. When the outside air temperatures are warm, the system operates at greater efficiency - without recourse to the heat pump.

The system also uses two thermal stores (which can be buried under the ground). These are linked together to maximise efficiency. They also enable heat to be stored over a 24 hour period and this consequently allows the system to utilise off-peak electricity.

The Ambient Energy endothermic heating system is available in a variety of configurations. At its simplest, it is integrated with a conventional boiler and reduces the amount of fuel burned. At its most sophisticated, it provides a summer cooling mode as well as almost all the hot water and underfloor heating a house could need: here the only additional heating required is an electric immersion heater, needed occasionally to get domestic hot water up to 60°C.

The system is the brainchild of former architectural consultant Alan Ridett and has been developed in conjunction with the University of Portsmouth. "We estimate that the cost of providing central heating and hot water for a typical family home will be little more than £130 per year, a reduction of between 50% and 70% compared with conventional systems," says Ridett.

From garage to gable

Another new roofing product, this time from Germany, also offers exemplary green credentials. Ardesia is a roofing slate made from recycled rubber, and at a cost of under £15/m2 it is as cheap as any roof cover on the market, save the profiled concrete tile.

Rubber roofing slate is a relatively new technique, originating in Canada. The German product has been in manufacture since 1998 and is now available across Europe. Slates are made from waste car tyres, melted down and extruded into appropriate shapes. The only additional ingredients are a small amount of HDPE - also recycled - and colouring agents. The slates are available in five colours: black, slate grey, light grey, green and red.

Rob Carlin of UK agent Euro-Bati-Concept says that the rubber slates have performance advantages when compared to slate. "It is a lightweight product and much easier to work with," he points out. It is claimed that the rubber slates have a lower wastage rate as they can't easily be broken.

The basic roof slate comes in a 240 mm by 380 mm format and can be laid at any pitch over 20°. Variations are available for vertical hanging.

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