Green, blue, brown and white roofs
Environmentally friendly roofs are becoming more and more trendy. The most commonly known one is the green roof but there are other varieties: brown, blue and white. Learn more about them and their differences in this short guide.
Designers always put special importance into the elevations of buildings because they are perceived from the street and have a significant visual impact. But what about the roofs and especially flat roofs or what we call the 5th façade? It's a perfect opportunity to collect water and reuse it, improve wildlife with vegetation while also improving the performance of the building and combat the carbon footprint that building works have. Furthermore, this is a great outdoor space for people to enjoy that is still mostly underused.
Cities are generally full of impervious surfaces causing lots of flooding issues. Rainwater has to go through the sewage system instead of filtered through the soil directly into underground rivers. We have replaced forests and fields by concrete, asphalt or brick and that's not a sustainable way of designing cities. The city of London, like many others, is becoming more conscious of this and therefore trying to adapt to climate change putting new regulations in place. Lots of cities around the world have already passed regulations to try to incentivise these types of roofs.
1. Green Roof
A green roof is covered in vegetation. This can be an extensive roof, with a thin layer of plants which are low maintenance or an intensive roof which is thicker, has a more varied vegetation and has a similar maintenance to a garden .
Green roofs serve a range of purposes:
Absorb CO2
Act as insulation
Reduces demand for heating and cooling keeping the internal temperature more stable
Act as habitat for wildlife such as: insects, bees, butterflies or birds which are usually declining in cities
Recreational opportunities.
Positive impact for humans too. Increased amounts of green areas in cities is proved to help our health and general wellbeing.
2. Blue Roof
This type of roof stores the rainwater to be reused for other purposes like watering the plants or flushing toilets (basically any non-potable purpose) which reduces the demand on the mains water supply. Furthermore it can also restrict the speed it goes into the drainage system to avoid straining the infrastructures. Like green roofs they can help cooling buildings and urban areas.
3. Brown Roof
This roof is a variation of the Green roof but focused on biodiversity. This roof uses the soil and rumble from the constructions site excavations as substrate in order to recycle it in place.
A brown roof is where the substrate surface is left to self-vegetate from windblown and bird lime seed dispersal. These roofs are the best way of replicating the wild urban spaces that are found at ground level since similar plants will colonise the roof too.
4. White Roof
This is the oldest environmentally friendly roof. It has been used in the Mediterranean, for centuries. Painting a roof white reflects up to 85 per cent of the sunlight. This keeps the building cooler and reduces the need for air conditioning. By not holding heat they also don't warm the city up either, reducing the overall temperature. White roofs are the best option of all types at reducing heat but unfortunately they don't collect the rainwater or store it and don't help with improving the wildlife situation.
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