Our bespoke living roofs offer a guaranteed watertight roofing solution that reduces rain water run off, enhances wildlife habitats and provides you with valuable additional amenity space.

The environmental benefits of a green roof

Reducing rainwater run-off
Most of the water that falls on land covered in vegetation is absorbed to become part of the water table. This water is then absorbed by plants, or evaporates back into the atmosphere. The water which falls on the hard surfaces in an urban area runs off, via drainage systems, into rivers. As a result, the water table is lower, water quality in rivers and streams deteriorates, and flooding can result.

Biodiversity and wildlife

A green roof creates an ideal undisturbed habitat for invertebrates, which is of benefit to the bird population. Plant species which cannot compete with the aggressive species which dominate more fertile ground can thrive in the shallow soil of a sedum roof.

Reducing the urban heat island effect

Large urban areas have their own specific climate with higher humidity, night-time temperatures and pollution levels than surrounding areas. The resulting degradation in air quality is particularly dangerous to people with asthma and other respiratory diseases, and can increase convection currents which can generate more rainfall over cities. Urban vegetation uses heat energy to power evapotransporation. Evapotransporation is the combined effect of transpiration – where a plant draws moisture up through its root system and releases it into the atmosphere – and evaporation of water from the soil and leaves. As part of a wider network of urban green spaces, even a small green roof is contributing to the cooling effect.

Reducing air pollution

Trees can filter out fine airborne particles as the air passes over their leaves and stems, and these particles are then washed by the rain into the soil. Extravagant claims have been made about the effects of green roofs on air pollution: their contribution to this effect is probably small, but studies have shown that green roofs are very effective in trapping heavy metals which could otherwise contaminate water supplies.

Reducing noise pollution

Roofs made of hard surfaces tend to reflect sounds. Green roofs can absorb sound: with lower frequencies being blocked by the substrate, and higher frequencies by the vegetation. More research is needed to back up some of the more extravagant claims of the green roof industry in this regard.

The economic benefits of a green roof

Increased roof life

Heat exposure, solar radiation and ultraviolet radiation all take their toll on roofing materials and reduce their lifespan. A green roof is protected by its layers of substrate and vegetation, which also has the effect of reducing fluctuations in temperature by day and overnight, which is another cause of the degradation of roofing materials. Green roofs need to be built to a high standard in order to be 100% leak-proof, so they start off in excellent condition and are protected from atmospheric damage. The Hertalan membranes we use are guaranteed for 20 years, and the expected life of the a green roof can be anything from 50 to 100 years.

Lower maintenance needs

The roof may need some watering through the summer – this will depend upon the choice of plants. The leaves which will ultimately block the gutters of a conventional roof will tend to stay on a green roof until they are incorporated into the substrate as humus.

Insulation and energy efficiency

Some general claims are made about the improvements in energy efficiency that will come from a green roof. The fact is that the thermal benefits of green roofs will vary depending on the choice of plants and the type and thickness of the growing medium. However the following principles hold true.

• In summer, a green roof will heat up less, and will lose heat by evaporative cooling.

• In winter, the green roof will provide some measure of insulation, depending on the thickness of the materials used and the type of plants. Evergreen plants such as sedum are more effective than, for example, a wildflower meadow, which will die back in winter.

The amenity and aesthetic value ofgreen roofs

Amenity value

In densely populated urban areas, roofspace is an underused resource. If designed with sufficient load-bearing capacity and created with recreational use in mind, green roofs can create vital new amenity space. A green roof is better protected against human traffic than conventional roofing materials.

Food production

An appropriately designed roof garden can be a source of fresh, healthy, local food.

Aesthetic value

The mental health benefits of green spaces for residents of urban areas have been well documented. Even seeing plants on an inaccessible roof will apparently benefit people's stress levels, lower their blood pressure and reduce muscle tension. Urban roofscapes tend to be unappealing and positively ugly– green roofs are an attractive alternative which benefits everyone who has sight of them.

Under construction in Montpelier, Bristol, this vegetable garden doubles the available amenity space of this inner-city Victorian terrace.

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