YOU WON'T BELIEVE THIS: Green Roofs Galore

[Zeno Swijtink]

May 3, 2008
Rain or shine, the answer to climate change can be found on your roof
Hannah Fletcher

Rodney and Diana Lord are not classic eco-warriors. They live in the middle of a sea of Victorian semis in southeast London. They wear loafers and smartly pressed shirts. And while they know they really should use energy-saving light bulbs, they just “haven’t got around to it”.

Yet in 2002 the couple became unwitting ecological trendsetters when, on a plot of land in Camberwell, they built a thoroughly modern house with a thoroughly modern roof.

The flat roof, covered in hardy sedum plants, acts as a natural insulator, keeping the house warm in winter and cool in the summer. When it rains, the plants absorb more than 50 per cent of the water, helping to prevent the kind of deluges that have wreaked havoc over the past few years. The rest of the water drains off and enters a rainwater-harvesting system where it is stored in an underground tank and pumped up for household chores.

“We didn’t design it with the environment in mind,” Mr Lord, 62, admitted as he stood on his roof. “It was about comfort, convenience and aesthetics. But now we find the environmental advantages really satisfying.”

Six years on, and Britain is rushing to catch up with the Lords. As the dual consequences of climate change — flooding and drought — manifest themselves with alarming regularity, and with water bills set to increase by about 6 per cent this year, homeowners, businesses and local and national authorities are looking to their roofs to manage water and cut costs.

As a result, Britain is experiencing one of the biggest booms in Europe in the “green roof” and rainwaterharvesting industries. Sales of rainwater-harvesting systems have more than doubled every year for the past four years. An industry worth about £500,000 in 2004 has now grown to more than £10 million.

The number of green roof companies has increased fivefold in as many years. Where fewer than 10,000 square metres of sedum blanket were laid annually, that figure is now approaching 100,000.

“We’re rapidly running out of water in Britain,” said Roger Budgeons, director of Rainharvesting Systems. “Water supplies are under severe stress, and people are more aware of the issue.”

In April last year, the Government’s code for sustainable homes made it mandatory for all publicly financed new buildings to cut water usage from 150 litres per person per day to 105 — a target most easily achieved through rainwater harvesting.

This month this became a requirement for privately financed social housing as well, and insiders predict that water legislation for private homes and companies could be introduced within a few years.

Many organisations have ploughed ahead in anticipation. Hundreds of thousands of employees and customers at Marks & Spencers, B&Q, Tesco, Asda and Sainsbury’s, as well as prison inmates, are already flushing waste, washing floors and watering plants with rainwater.

Buried in the ground beneath these buildings are storage tanks the size of tennis courts. When it rains, water pours into the systems at the rate of one bathtubful per second.

Lisa Farnesworth, a director at Stormsaver, which has installed many of these rainwater harvesting systems, said that the companies would be reducing their mains water usage by up to 80 per cent and saving more then £10,000 a year on their water bills. In private homes, where smaller harvesting systems cost about £2,000 to install, homeowners can cut their water costs by 40 per cent.

Green roofs might not reduce your water bills but, according to Dusty Gedge, the founder of Livingroofs.org and president of the European Federation of Green Roof Associations, they can cut your air-conditioning bills.

As well as absorbing up to 60 per cent of rainwater, green roofs can lower the surrounding air temperature by up to 11C. “2005 and 2006 were exceptionally hot summers, particularly in London and Manchester,” Mr Gedge said. “Comet was selling one air-conditioning unit a second. But if we all had green roofs, we wouldn’t need air-conditioning.”

Just last month, Britain’s first policy on green roofs was produced by the Mayor of London. Sheffield, Bristol, Manchester and Birmingham are all soon to follow. “There are thousands of square metres of roof going up all over the place,” Mr Gedge said. “It’s happening. It’s really happening.”

[savewater]

I love it! Fabulous. Wonder how long it will take the peeps here
in the US to get truly hip?? Perhaps when our backs are against the
wall and we're purchasing water monthly from a huge conglomerate.
We've got a conventional roof (boring), replacing a crummy and noisy metal roof. For us, we'll be focusing on Water Catchment, collecting gutter
runoff in tanks. Very conserving and comforting. Thank you so much for writing about the Lords and the movement in Britain.

Here's to living SMARTLY and wisely, always conserving.

Bonnie

May 3, 2008
Rain or shine, the answer to climate change can be found on your roof
Hannah Fletcher

Rodney and Diana Lord are not classic eco-warriors. They live in the middle of a sea of Victorian semis in southeast London. They wear loafers and smartly pressed shirts. And while they know they really should use energy-saving light bulbs, they just “haven’t got around to it”.

Yet in 2002 the couple became unwitting ecological trendsetters when, on a plot of land in Camberwell, they built a thoroughly modern house with a thoroughly modern roof.

The flat roof, covered in hardy sedum plants, acts as a natural insulator, keeping the house warm in winter and cool in the summer. When it rains, the plants absorb more than 50 per cent of the water, helping to prevent the kind of deluges that have wreaked havoc over the past few years. The rest of the water drains off and enters a rainwater-harvesting system where it is stored in an underground tank and pumped up for household chores.

“We didn’t design it with the environment in mind,” Mr Lord, 62, admitted as he stood on his roof. “It was about comfort, convenience and aesthetics. But now we find the environmental advantages really satisfying.”

Six years on, and Britain is rushing to catch up with the Lords. As the dual consequences of climate change — flooding and drought — manifest themselves with alarming regularity, and with water bills set to increase by about 6 per cent this year, homeowners, businesses and local and national authorities are looking to their roofs to manage water and cut costs.

As a result, Britain is experiencing one of the biggest booms in Europe in the “green roof” and rainwaterharvesting industries. Sales of rainwater-harvesting systems have more than doubled every year for the past four years. An industry worth about £500,000 in 2004 has now grown to more than £10 million.

The number of green roof companies has increased fivefold in as many years. Where fewer than 10,000 square metres of sedum blanket were laid annually, that figure is now approaching 100,000.

“We’re rapidly running out of water in Britain,” said Roger Budgeons, director of Rainharvesting Systems. “Water supplies are under severe stress, and people are more aware of the issue.”

In April last year, the Government’s code for sustainable homes made it mandatory for all publicly financed new buildings to cut water usage from 150 litres per person per day to 105 — a target most easily achieved through rainwater harvesting.

This month this became a requirement for privately financed social housing as well, and insiders predict that water legislation for private homes and companies could be introduced within a few years.

Many organisations have ploughed ahead in anticipation. Hundreds of thousands of employees and customers at Marks & Spencers, B&Q, Tesco, Asda and Sainsbury’s, as well as prison inmates, are already flushing waste, washing floors and watering plants with rainwater.

Buried in the ground beneath these buildings are storage tanks the size of tennis courts. When it rains, water pours into the systems at the rate of one bathtubful per second.

Lisa Farnesworth, a director at Stormsaver, which has installed many of these rainwater harvesting systems, said that the companies would be reducing their mains water usage by up to 80 per cent and saving more then £10,000 a year on their water bills. In private homes, where smaller harvesting systems cost about £2,000 to install, homeowners can cut their water costs by 40 per cent.

Green roofs might not reduce your water bills but, according to Dusty Gedge, the founder of Livingroofs.org and president of the European Federation of Green Roof Associations, they can cut your air-conditioning bills.

As well as absorbing up to 60 per cent of rainwater, green roofs can lower the surrounding air temperature by up to 11C. “2005 and 2006 were exceptionally hot summers, particularly in London and Manchester,” Mr Gedge said. “Comet was selling one air-conditioning unit a second. But if we all had green roofs, we wouldn’t need air-conditioning.”

Just last month, Britain’s first policy on green roofs was produced by the Mayor of London. Sheffield, Bristol, Manchester and Birmingham are all soon to follow. “There are thousands of square metres of roof going up all over the place,” Mr Gedge said. “It’s happening. It’s really happening.”

[Tars]

Thanks for this fascinating post, Zeno! As it happens I have three low-pitch household roofs that are due to be re-roofed. I'd been planning on using white reflective PVC sheeting. Now after reading this, I'm going to look at using sedum groundcover. My initial concern is that, due to the relatively dryer climate here than in Britain, I probably would actually have to water the roofs during at least half of the year. I'm wondering too if there might be weight concerns. Also, the underlayment for a sedum roof...something that can be depended on not to break down for 10+ years...

Anyone have any suggestions for a suitable sedum groundcover for this zone?

[Lenny]

Good article.Thanks.
Read once that in an average storm, an average roof can catch about 12, 000 gallons of water. That's a LOT of storage. Anybody have practice on it?

[PeriodThree]

That number, 1 storm on 1 roof = 12,000 gallons of water, doesn't seem right to me.

1 gallon of water = .134 cubic feet
1 cubic foot = 7.48 gallons

If a storm yielded 1 inch of rain, then a 2,000 square foot roof
would (assuming I am doing my math right!) yield
2000/12 = 166.7 cubic feet of water

166.7 * 7.48=1246.92 gallons.

So, not 12,000, but a not too shabby.

Maybe a week's consumption for a family of 4

Good article.Thanks.
Read once that in an average storm, an average roof can catch about 12, 000 gallons of water. That's a LOT of storage. Anybody have practice on it?

[Dynamique]

the 12,000 gallon figure may be what one of these roofs can collect over the course of a rainy season, although it sounds a tad high for the climate in this area.

That number, 1 storm on 1 roof = 12,000 gallons of water, doesn't seem right to me.

1 gallon of water = .134 cubic feet
1 cubic foot = 7.48 gallons

If a storm yielded 1 inch of rain, then a 2,000 square foot roof
would (assuming I am doing my math right!) yield
2000/12 = 166.7 cubic feet of water

166.7 * 7.48=1246.92 gallons.

So, not 12,000, but a not too shabby.

Maybe a week's consumption for a family of 4

[Zeno Swijtink]

the 12,000 gallon figure may be what one of these roofs can collect over the course of a rainy season, although it sounds a tad high for the climate in this area.

Not really. Average rainfall in Sonoma County is about 30 inches. Of course, there is a huge variability across the county, with average yearly rainfall in Cazadero 70 inches, Sebastopol 40 inches, with its own variability over time.

Since the rain is not evenly over the year, the roof may get soaked and not capture all the water.

[Dynamique]

Living roofs getting saturated during the rainy season is something to take into consideration, especially with a rather binary climate like we have here. A living roof needs to be designed very carefully and built using materials, such as very light perlite-based soil and a special type of membrane over the roof structure, and plants designed for the situation. This is not something that an amateur should take on!

Zeno, from the rainfall stats you give, it sounds like a metal roof could collect quite a lot of water during the rainy season! We're currently installing a metal roof on our house and you've given me some inspiration. It involves a pond or a cistern to store the runoff Thank you!

Not really. Average rainfall in Sonoma County is about 30 inches. Of course, there is a huge variability across the county, with average yearly rainfall in Cazadero 70 inches, Sebastopol 40 inches, with its own variability over time.

Since the rain is not evenly over the year, the roof may get soaked and not capture all the water.

[PeriodThree]

I disagree :-)

In general, unless it is something with a high risk of harm to human life 'amateurs' should try to take on projects like this.

A substantial part of our strength as a nation has come from so-called amateurs feeling like they can do things, taking on projects-even absurd ones! And prevailing.

We need our experts, of course, but amateurs bring something basic to bear.

Organic farming, biodiesel, the web, and aviation are all things where amateurs have lead.

This is not something that an amateur should take on!

[Dynamique]

Having your roof collapse due to the extra weight from all that water and soil is what most sensible folks would consider a high-risk scenario!

Definitely look into it and implement it, but consult someone who knows what s/he is doing and is qualified to help you avoid problems. There's also the issue of permits and and the legal stuff. A structural engineer may be in order to ensure that the roof does not cave in, for example.

"Amateur" or grass-roots type initiatives are great and where the majority of good ideas come from. However, there is a need for expertise and often people trained in the subject area are the ones who get the ball rolling. For example, a significant contribution to the R&D for biodiesel was from the chemistry and ag sciences departments at the University of Idaho.

I disagree :-)

In general, unless it is something with a high risk of harm to human life 'amateurs' should try to take on projects like this.

A substantial part of our strength as a nation has come from so-called amateurs feeling like they can do things, taking on projects-even absurd ones! And prevailing.

We need our experts, of course, but amateurs bring something basic to bear.

Organic farming, biodiesel, the web, and aviation are all things where amateurs have lead.

[PeriodThree]

Well, thank you Dynamique. I won't do green roofs now, since clearly any attempt I made would result in my roof collapsing :-/

Having your roof collapse due to the extra weight from all that water and soil is what most sensible folks would consider a high-risk scenario!

Definitely look into it and implement it, but consult someone who knows what s/he is doing and is qualified to help you avoid problems. There's also the issue of permits and and the legal stuff. A structural engineer may be in order to ensure that the roof does not cave in, for example.

"Amateur" or grass-roots type initiatives are great and where the majority of good ideas come from. However, there is a need for expertise and often people trained in the subject area are the ones who get the ball rolling. For example, a significant contribution to the R&D for biodiesel was from the chemistry and ag sciences departments at the University of Idaho.

[Dynamique]

Gee, dude(ette), I didn't mean to rain on your parade here!

Of course do your due diligence and research and see if it would be feasible for you. We did some research on the concept and asked around a bit when we realized that our roof needed to be replaced. We concluded that it would be more expense and upkeep than we were willing to do. Instead we went with a metal roof that has a number of energy-saving benefits and can be used to collect rainwater for storage in a rainbarrel or cistern.

If it looks like the living roof would be beneficial and you're willing to do the maintenance, then go for it! But do use some common sense and get qualified expertise when you're over your head. There are organizations that have experience and can help you out.

There's got to be at least one architect in the Sebastopol area who is familiar with green roofs. There's probably at least one non-profit organization in the US that can provide info and referrals. The public library has books on "green" building techniques. The Solar Living Center in Hopland may have some resources available.

Well, thank you Dynamique. I won't do green roofs now, since clearly any attempt I made would result in my roof collapsing :-/

[Melodymama]

" you're willing to do the maintenance, then go for it! "

Duh! Did you ever really think how hard it would be to get the lawnmower up there?

[Braggi]

" you're willing to do the maintenance, then go for it! "

Duh! Did you ever really think how hard it would be to get the lawnmower up there?

I would like to increase the area of my kitchen garden. I have a metal roof and very sturdy beams supporting it. I could put a heck of a lot of pots up there and I just might do that.

I'll be the deer would have trouble getting up there!

-Jeff