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Three items you require to take into consideration when retrofitting a environmentally friendly roof

As the govt announces even further commitments in direction of carbon reduction, one particular of the layout developments we assume to see in 2021 is the broader consider-up of eco-friendly roofs.

There are lots of ecological added benefits when developing a green roof. These contain: 

  • Introducing mass, thermal resistance and absorbing considerably less heat than regular roofs, so you minimize the carbon footprint and the city warmth island influence
  • Creating a habitat for animals and bugs. As properly as immediately giving an surroundings and foods source, planted roofs also great and humidify the bordering air, making a beneficial microclimate
  • The vegetation in eco-friendly roofs can filter out carbon dioxide, nitrates and other unsafe resources. This also can help strengthen local air high-quality, which can profit equally humans and animals. (you can assume to listen to a lot additional on the topic of air high quality and in excess of-heating throughout 2021)
  • Dependent on the inexperienced roof design and style, the immediate water operate-off can be lowered significantly – by as much as 90 per cent, lowering worry on drainage devices and in switch supporting to mitigate localised flooding
  • Plants are also productive at cutting down noise, as they supply purely natural audio insulation they can minimize reflected seem by up to 8dB.

The ecological and environmental positive aspects outlined over generally enhance in line with the substrate depth. For case in point, the environmental gains of shallow environmentally friendly roofs are on the total significantly a lot more modest than these offered by intense types, owing to the more compact array of vegetation that can be grown.

The rewards are very clear but what about the regulations? Effectively, if you want to carry out repairs on, or re-address a pitched or flat roof, you will need to have acceptance, if:

  • You have out structural alterations or the loading of the roof covering noticeably changes
  • The performance of the new covering will be drastically distinct to that of the existing covering in the party of a hearth
  • You are changing or restoring a lot more than 25 for every cent of the roof space.

The crucial constructing rules problems are to do with structure, hearth protection and thermal insulation effectiveness.


The load-bearing ability of a making ought to be known right before organizing a eco-friendly roof and a structural engineer’s assistance is essential. The masses can be important, including vegetation, increasing substrate and any drinking water held in the process.

It is crucial to contemplate not just the weight of plants when planted but their pounds at maturity, as these can be noticeably heavier around time, and to allow for for the bodyweight of saturated plants and substrate, rather than dry weights. You also will need to allow for short-phrase loads, together with wind uplift, particularly with bigger shrubs. For retrofitting a inexperienced roof, it is crucial to set up early no matter whether the installation will exceed the existing structural capacity of the building and the extent to which this will need to have to be modified to assist the set up. In some circumstances, it is probable to strengthen an present roof in strategic regions (and not throughout the total roof) in order to obtain the structure consequence while also minimising prices.

If you are making it possible for entry to the roof, then remember to let for the fat of men and women who will use the place and of any mobile machines that will be used. Also bear in mind to deliver guarding and safety to the roof edge.

Fireplace basic safety

In relation to fire functionality, the typical consensus is that, as prolonged as the green roof is kept moist, it is likely to be remarkably resistant to ignition. It has been advised that a green roof may possibly represent a fireplace hazard if it dries out (such as could occur in a drought if no irrigation is furnished).

In 2013 the Ministry of Housing, Communities and Local Govt commissioned a investigation report from Exova Warringtonfire, which concluded that the growing medium used in eco-friendly roofs can not be ignited and flame unfold does not occur. Temperatures acquired at the lowest point in the environmentally friendly roof substrate are not superior plenty of to end result in ignition of the materials used below the escalating layer, therefore environmentally friendly roofs are generally thought of to be risk-free in the party of a hearth.

Some treatment must be taken in the selection of the plants them selves. Succulents are usually deemed the lowest fire threat, whilst conifers are between the optimum. European rules propose that .5m-vast gravel fireplace breaks ought to be provided all around the edges of the roof, all around openings penetrating the roof, and at 40m spacing on greater roofs.

Thermal insulation

The degree of insulation a living roof can provide although depends on numerous components these as humidity stage. As moisture ranges can change enormously based on seasonal elements, green roofs are not generally recognised in making restrictions as acquiring a U-worth, so you will require to upgrade the insulation to the roof in the typical way.

That claimed, throughout the winter season months thermal performance can be as a great deal as 25 per cent larger adhering to installation of a environmentally friendly roof. In the summer months, a eco-friendly roof has the potential to retain homes cooler than bare roofs by an common of 15°C, so installing a environmentally friendly roof masking can cut down the require for synthetic cooling methods. Hopefully these positive aspects will be recognised in foreseeable future variations of the laws.

You can come across out much more about environmentally friendly roofs in the Environmentally friendly Roof Organisation’s Inexperienced Roof Code of Finest Practice for the British isles.

Geoff Wilkinson is controlling director of Wilkinson Building Consultants