Wednesday, June 26, 2019

The Grass is Greener on the….Roof?

The Grass is Greener on the….Roof?


Green roofs were once seen as the preserve of millionaires. Nowadays the idea of a garden on a roof is quite utilitarian – it serves the environment and its community in a number of ways.

For a start, greening the built environment makes it look better more a minimal outlay. Green roofs also help to keep materials like waterproofing membranes and old wood from the landfill, as they prolong the lives of membranes and can be a suitable venue for old beams and so on.

The impact of rain in urban areas is lessened by green roofs, as some water is taken up by the soil and plants, from where it goes back into the atmosphere.

In the summer, the growing medium and plants on a roof hang onto up to 90 per cent of the rain it receives. In winter it’s up to 40 per cent. This helps to reduce the strain on sewer systems after heavy storms.

green 300x225 The Grass is Greener on the….Roof?

Plants on roofs can help to keep cities cooler by releasing water due to evaporation, and also by absorbing some of the light that would get absorbed by dark roofs and radiate out into the air, forming the “urban heat island” effect.

The extra plants on green roofs can capture airborne pollution particles and filter out noxious emissions.

It’s not all about energy and pollution, though. Green roofs can become community gardens, or commercial spaces, like restaurant terraces. They can also become children’s parks and even create jobs – those plants need caring hands, right?

It’s estimated that if there was a $10 billion investment in the US to make 50 billion square feet of green roof area (less than one per cent of the country’s total roof space), this development could create up to 200,000 jobs. These roofs are surprisingly easy to construct. They are usually based on a layer of metal roof cladding, which has standing seams to provide “trays” for a substrate of small stones and finally soil.

On the domestic front, the insulation that a green roof offers cuts the amount of energy needed to heat or cool a house. This reduction can be up to 75 per cent.

A green roof can also cut out noise – especially low frequency notes – by up to 40 decibels. These spaces also attract more wildlife, like birds and insects. If these animals have more places to live and thrive, their populations are more resistant to environmental changes.

Green roofs can also attract people. To put it simply, green spaces make people feel better. How many times have you seen hospital patients sitting in the hospital gardens? It’s not just for fresh air, as time spent in calm places reduces blood pressure and anxiety. Local residents can gather on these roof gardens to meet, eat, play and make community decisions.

Urban agriculture projects thrive on roofs – the residents of an apartment block might grow some fruit and vegetables on top of their building. This is empowering and highly sociable.

Schools and colleges should think about a green roof so that students can earn more about botany, biology and the environmental issues we all face.


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