Gary Grant discusses Green Roofs, Living Walls and Rain Gardens

You know, it's an overwhelming argument in favor of urban greening. Plenty of evidence now and lots of peer-reviewed scientific papers to back it up. So it's not just the opinion of a few people, it's been shown to be real. So that's, you know, we're in a very strong position now.

Hello and welcome to Rethink What Matters, the podcast dedicated to aligning the economy, the ecology, and everyone for improved business profitability, stronger families, and a greener planet. And today I'm joined by Gary Grant of the Green Infrastructure Consultancy, and we're going to be discussing green roofs, living walls, and rain gardens.

Okay, Gary, thanks very much for joining me on this podcast, the Rethink What Matters podcast, where, you know, we're really about trying to bring the economy, the ecology, and everyone into alignment. As I say, once again, thanks very much, Gary, from Green Infrastructure Consultancy.

Good, good to be here, Paul. Yeah.

And we're going to be talking about green roofs. Living walls and rain gardens. And I've seen just some, you know, fantastic projects on your website. I mean, really, really great stuff, really big projects, really great things that you're doing there at Meadowbank Development there and Team London Bridge, the Greater London Authority, the David Attenborough Building, PwC Moore London. And, you know, it's really— I think as a subject, it's absolutely spot on for what we're all about. You know, again, you know, bringing the economy, the ecology, and everyone into alignment. And so I did a quick little bit of research, you know, just to look at all the benefits of this. And there are vast— there are many. There are stormwater management, habitat creation, energy efficiency, air quality improvement, biodiversity enhancement, roof longevity, noise reduction, aesthetic appeal, mental health benefits, groundwater recharge, and educational opportunities. So this is just brilliant for us. So, yeah, perhaps, Gary, you'd give us a little bit of an introduction to yourself and your journey that got you started on, you know, your interest in green roofs, living walls, and rain gardens.

Well, thanks for that, Paul. That's a pretty good list, isn't it, of benefits? You can't really argue with that. So, you know, it's an overwhelming argument in favor of urban greening, plenty of evidence now, and lots of peer-reviewed scientific papers to back it up. So it's not just the opinion of a few people, it's been shown to be real. So that's, you know, we're in a very strong position now. So I used to be, I used to work for the London Wildlife Trust back in the 1980s, and the idea of urban ecology and urban nature was a little bit fringe in those days. People thought that towns and cities should be grey and all the nature should be out in the countryside. There's still some people who perhaps think that way. They're a little surprised about urban biodiversity, urban greening. Around London, there were a few little bits and pieces that were left behind. They weren't all built on and there were a few nature reserves and so on. It was about hanging on to those places before they were built on, if you like. So it wasn't a very— it wasn't like now where we're saying we want to restore nature. It was more about hanging on to nature. But through that process, you know, we started— I started to think about, well, yes, we could restore nature here and there. And so I first got involved in green roofs back in the early '90s, 1990s, when There's an architecture firm called Archetype that would build schools and visitor centers and museums, and we put a green roof on the Horniman Museum extension. So it's a wooden building, a little green roof, Nordic-style green roof on there. And I didn't really know very much about it, but it just seemed the right thing to do from my point of view. I didn't know about all the benefits. I just wanted to put wildflowers on a roof. Yeah, and so that was one of the first ones I got involved with. And, uh, you know, over the years, um, there weren't that many opportunities. Um, however, um, uh, in the 2000s, um, there was a renewed interest in green roofs because people like Dusty Gedge had been to Switzerland and they'd seen that the Swiss and the Germans were already doing this kind of thing. The idea at that point was that when you lose a bit of waste ground which is full of wildlife, maybe you put that habitat on the building that's replacing the waste ground. That was the thinking back then. There was a renewed interest, and then I wrote a report for Natural England in 2003. I think it was English Nature in those days, Natural England, a report on green roofs in 2003. Won the contract to write that, wrote that report, which was a review. And then in 2008, the Mayor of London started, as a result of all the campaigning that had been going on in London, the Mayor of London thought, well, yes, this is a good thing. So there was an expectation after 2009 that the centre of London should have green roofs, and the local authority started to get involved and I joined a firm called Green Roof Consultancy around about 2009, which was involved in all that. And of course, later on, we changed the name of the company to the Green Infrastructure Consultancy because we got involved in green walls and rain gardens and planning and policy and all sorts of bits and pieces to do with urban greening. So it spread from the roofs, and now it's all sorts of things.

What's driving it at the time, though? Was it the aesthetics of it that was driving it? Was it, you know, just the people wanting to have obviously more greener spaces because they're nicer to live with? People recognize that nature is a good thing. It was less— was it less about, you know, what we're all looking at today, which is trying to, you know, address climate warming?

And, uh, yeah, uh, well, of course climate change was known about then, but it wasn't high on the agenda. I mean, from my point of view, I wanted more wildlife habitat, so that's where I was coming from. Yeah, I suppose people were— the way architects used to describe it back then was this footprint replacement. So the idea is that you've got a bit of ground you build on, you lift that ground up and put it on the top of the roof, so it's almost a way of minimizing your overall impact, if you like. But, uh, people Yeah, but it wasn't really about aesthetics, but of course designers are about aesthetics, so yeah, that's very important. But it's a very good question. I mean, the sustainable drainage agenda wasn't really there back in those days, and yet that is an important part of it, isn't it?

So it's really coming to its own now, is it? It's finding its place. I mean, it's going to be something which every, you know, everyone's going to want to do. I was speaking with somebody today about permaculture.

Oh yeah, yeah.

And that seems quite related to this as well, you know. It's maybe less on roofs and walls and things, but you can see how everybody's trying to get nature back into society and back into our living spaces and our own.

Of course, permaculture involves people growing, uh, food, and, uh, you can have a roof garden, of course. So green roofs are not just the lightweight ones, they're also gardens which you can access. And growing food on roofs is a big, big thing, you know, in, uh, across the world. There are people, you know, in, in some parts of the States this is a big deal. On the continent, growing food on buildings. In, in China you have this as well. It is a thing.

And so that's, that's, that's taken off as well.

Yeah, yeah.

Living walls and rain predominantly is a business-oriented thing. That's really what we're talking about here, isn't it?

Yeah, yeah.

How businesses can use it, and then whether that's in public spaces or in private spaces, I guess. So most of the projects, I think, if I understand this correctly, they're public. They're public projects. Well, there was one with PwC we saw there.

Well, there's a mixture. I mean, well, no, we've worked on policy with, you know, public bodies like the Mayor of London and so on, but most projects are private projects. So for instance, the David Attenborough Building, which is a— it was a refurbished 1970s building owned by the University of Cambridge, right? And that project, um, that building is reinforced concrete, so retrofitting is easier than it is on some buildings. It's a very strong building, and the brief there was let's get biodiversity on the building. So, okay, um, so, you know, that was for University of Cambridge. So, you know, it's quite a sophisticated client, but actually, you know, to begin with, there were plans to perhaps have green roofs which weren't as biodiverse as they could be. So our role was to really push that and have a high diversity of planting. So, yeah, that's a private project. A lot of the developments in Central London, like the You know, Elephant Park, which is in South London there, Elephant Castle, that's all new housing that all has green roofs because the planning body, which is Borough of Southwark, would have, would have required— well, they do require green roofs, right? So, you know, that's private. Sometimes people in the client group aren't perhaps aren't aware of this, but they have to do it anyway now in London. So yeah, other large—

there are some mandatory reporting requirements, I think. There are some mandatory reporting requirements coming in now, I think, aren't there?

Yeah, well, there's planning requirements. Yeah, there's planning requirements as well. You know, to get planning permission in central London for a new building, you need to put a green roof on it.

Right.

That's in the urban— Right. Yeah, yeah, yeah. Unless there's a good reason why you can't.

Right.

So it's an expectation. It's the default position now. So in central London, there are millions of square meters of green roofs now.

Okay, that's great. And, uh, so obviously they need to be maintained, don't they? So it's all right building it, but then are there— what are the issues around maintaining? Because I can't manage a pot plant, let alone a green roof.

So it depends what it is really. So if it's what we call extensive, that is, uh, relatively lightweight, relatively self- sustaining. And so the idea is that you just go up there now and then just to make sure everything's okay, uh, pull up a few unwanted plants. You know, there are plants that tend to spread like Buddleia, and they can cause problems, um, you know, wind-borne weeds and so on. Pull those up, unblock the drains, and so on. So very minimal, right? No maintenance— that, that's not correct— minimal maintenance.

But any roof should be looked at Anyway, I suppose there are specific plants, yeah, that lend themselves to being on a roof.

Yeah, yeah, very low-growing, drought-tolerant. You don't irrigate, it just looks after itself. And that, that's the key to it, having the right drought-tolerant plants, sedums and other wildflowers that don't need much looking after. But of course, if it's a garden, that's something different. You'll need people potentially going there certainly frequently or regularly, just keep an eye on it, because as we know, gardens do fall apart. But a garden is also used quite a bit, isn't it? So yes, it's not really a burden, it's just an amenity that needs looking after.

I was going to ask, actually, you know, to what extent are these gardens actually used rather than just being, you know, a lawn on top of a building?

Well, the— you could have lawns, although they're not that common because of course they need to be mown. But most roof gardens are paved areas mixed with seating and planting.

Okay.

And you know, they are very popular. I mean, they're great place obviously to have a party, have a, an event.

Okay.

But, uh, you'll find that roof gardens in London, um, I mean, there are one or two open to the public as well, um, You know, in Fenchurch Street, you've got a roof garden there, which is owned to the public.

Okay.

But most of them are very well used because it's a great spot to have your lunch, a great place to have a meeting during the day, special events. So yeah, it really adds a lot to a building.

Right, okay. And so what are the challenges then, or what are the prerequisites for having a roof garden? Maybe you're in an older building, a company might be in an older building and think, yeah, we want to do this. Are there some obvious things they could look for to see if, you know, one might fit before they get a consultant in?

Well, yeah, I mean, the first thing you need to know is whether or not you've got the strength in the building to take the weight.

Right.

So before you do anything else, you need a structural engineer to let you know how much loading there is available. You know, quite a lot of older buildings are surprisingly strong. So I worked on a building that used to be a print printing works from the '50s, plenty of strength in there, no problem putting a roof garden on. But of course, other buildings may, may not have the strength in the structure to take that. So yeah, absolutely, for retrofitting older buildings, that can be a challenge to be able to take all that weight, but it can often be done. I mean, we estimate that you know, a third of the commercial buildings in London could be retrofitted with extensive green roofs. And there are a few clues as well. So for instance, if you see a building with paving slabs on it which are holding down the insulation, that's a common style of roof on a flat roof. Those paving slabs weigh more or less the same as an extensive green roof. So if, so you know already, if you were to swap out swap over the paving slabs with a green roof. You would know, obviously it needs to be confirmed by an engineer, but chances are you can do that. So there's quite a lot of potential for retrofit. And then of course with new building, although there's an extra cost, it shouldn't really be a problem for the architects and structural engineers to design these things into the building. That shouldn't be a problem at all.

Yeah, brilliant. And so we've got the benefit there then of habitat creation. Yep. So that's, you know, energy efficiency as well. So it's a natural insulator up there?

Yeah, well, yes, but it's better to think of it this way. So when you have soil and vegetation, you, in summer, you get evaporative cooling.

Right.

There's a shade effect, but you get evaporative cooling. So that actively cools a building in summer, having soil vegetation on it.

It's a good point.

So that really is a significant thing. And there's an interesting variation on extensive green roofs called solar green roofs or bio-solar roofs where you combine PVs with the extensive green roof. And that means you get cooling from the green roof, which increases the efficiency of the PV. So that's a really interesting story and worth having a look at.

Solar panels? Is this solar panels?

Solar panels combined with a green roof, and it's the cooling, uh, which is the thing. And of course, um, the water, the rain that lands on that roof is partially absorbed in that soil, and then it's that which, um, evaporates later on, giving you the cooling.

Right, okay.

So that's the energy side. It's mainly about shade and cooling.

Right, it's great how sort of the infrastructure, the buildings and nature are starting to work together.

Exactly, yeah.

Yeah, that's really, really cool, isn't it? Really cool. I love that.

It's literally cool. Yeah.

Yeah. So literally cooling. So, you know, and obviously nice space is great for productivity, right? I mean, we all like a nice place to work in, space to work in.

Yeah.

Living walls. I mean, we're talking about green roofs, there's living walls, there's rain gardens in a minute. Living walls, like vertical gardens.

Yeah.

I guess there must be some limitations as to what, where you can put a living wall. You can't just put one up anywhere.

True, but in some ways there are more possibilities because you can usually find a way to take the weight. So, you know, with a roof, there may be situations where you can't have a green roof, but most walls can be modified to transfer the weight. You know, you can use steel subframes and so on to spread weight to load-bearing parts of the wall, or you can transfer the weight down the wall. So, or you can grow lightweight climbing plants on, on trellises. So there's usually a way of vegetating a wall, right? And it doesn't really— obviously you don't want to cover windows, but it doesn't really matter either what direction the wall is facing in because you can choose plants that are say shade tolerant for north-facing, or, or don't mind the extra sun for south-facing, or, or in between for east and west. So, so there's a, there's a lot of possibilities for vegetating, um, vertically. And of course, the great thing about that is you get the cooling, which we've already talked about, but people can see it.

Yeah.

Um, and, and it's relatively inexpensive, um, compared to— well, it depends what it is. If it's just climbing plants, that's very, very inexpensive and easy to look after. If it's what we call modular green walls, intensive green walls, that's a different story, you know, where you're irrigating, you've got thousands of plants in modules, that's a lot more. You know, it's an overwhelming argument in favor of urban greening, plenty of evidence now, and lots of peer-reviewed scientific papers to back it up. So it's not just the opinion of a few people, it's been shown to be real. So that's, you know, we're in a very strong position now.

Hello and welcome to Rethink What Matters, the podcast dedicated to aligning the economy, the ecology, and everyone for improved business profitability, Stronger families and a greener planet. And today I'm joined by Gary Grant of the Green Infrastructure Consultancy, and we're going to be discussing green roofs, living walls, and rain gardens.

Okay, Gary, thanks very much for joining me on this podcast, the Rethink What Matters podcast, where, you know, we're really about trying to bring the economy, the ecology, and everyone into Alignment. As I say, once again, thanks very much, Gary, from Green Infrastructure Consultancy.

Good, good to be here, Paul.

Yeah, and we're going to be talking about green roofs, living walls, and rain gardens. And I've seen just some, you know, fantastic projects on your website. I mean, really, really great stuff, really big projects, really great things that you're doing there at Meadowbank Development there and Team London Bridge. The Greater London Authority, the David Attenborough Building, PwC Moore London. And, you know, it's really, I think, as a subject, it's absolutely spot on for what we're all about. You know, again, you know, bringing the economy, the ecology, and everyone into alignment. And so I did a quick little bit of research, you know, just to look at all the benefits of this. And there are vast, there are many, there are stormwater management, habitat creation, energy efficiency, air quality improvement, biodiversity enhancement, roof longevity, noise reduction, aesthetic appeal, mental health benefits, groundwater recharge, and educational opportunities. So this is just brilliant for us. So yeah, perhaps, Gary, you'd give us a little bit of an introduction to yourself and your journey that got you started. On your interest in green roofs, living walls, and rain gardens?

Well, thanks for that, Paul. That's a pretty good list, isn't it, of benefits? You can't really argue with that. So, you know, it's an overwhelming argument in favor of urban greening. Plenty of evidence now, and lots of peer-reviewed scientific papers to back it up. So it's not just the opinion of a few people, it's been shown to be real. So that's, you know, we're in a very strong position now. I used to work for the London Wildlife Trust back in the 1980s, and the idea of urban ecology and urban nature was a little bit fringe in those days. People thought that towns and cities should be grey, and all the nature should be out in the countryside. There's still some people who perhaps think that way. They're a little surprised about urban Urban biodiversity, urban greening. So, you know, around London there were a few little bits and pieces that were left behind, you know, they weren't all built on and there were a few nature reserves and so on. So it was about hanging on to those places before they were built on, if you like. So it wasn't a very— it wasn't like now where we're saying we want to restore nature, it was more about hanging on to nature. But through that process, you know, we I started to think about, well, yes, we could restore nature here and there. I first got involved in green roofs back in the early '90s, 1990s, when there was an architecture firm called Archetype that would build schools and visitor centers and museums. We put a green roof on the Horniman Museum extension. It's a wooden building, a little green roof, Nordic-style green roof on there. And I didn't really know very much about it, but it just seemed the right thing to do for, from my point of view. I didn't know about all the benefits. I just wanted to put wildflowers on, on a roof.

Yeah.

And so that was one of the first ones I got involved with. And, uh, you know, over the years, um, there weren't that many opportunities. Um, however, um, uh, In the 2000s, there was a renewed interest in green roofs because people like Dusty Gedge had been to Switzerland and they'd seen that the Swiss and the Germans were already doing this kind of thing. The idea at that point was that when you lose a bit of waste ground which is full of wildlife, maybe you put that habitat on the building that's replacing the waste ground. So that was the thinking back then. And so there was a renewed interest. And then I wrote a report for Natural England in 2003. I think it was English Nature in those days, Natural England, a report on green roofs in 2003.

Right.

So won the contract to write that, wrote that report, which was a review. And then in 2008, the Mayor of London started, as a result of all the campaigning that had been going on in London, the Mayor of London thought, well, yes, this is a good thing. So there was an expectation after 2009 that the centre of London should have green roofs, and the local authority started to get involved. And I joined a firm called Green Roof Consultancy around about 2009, which was involved in all that. And of course, later on, we changed the name of the company to the Green Infrastructure Consultancy because we got involved in green walls and rain gardens and planning and policy and all sorts of bits and pieces to do with urban greening. So it spread from the roofs and now it's all sorts of things.

What was driving it at the time, though? Was it the aesthetic appeal of it that was driving it? Was it, you know, the people wanting to have obviously more greener spaces because they're nicer to live with? People recognize that nature is a good thing. Was it less about, you know, what we're all looking at today, which is trying to, you know, address climate warming.

And, uh, yeah, uh, well, of course climate change was known about then, but it wasn't high on the agenda. I mean, from my point of view, I wanted more wildlife habitat, so that's where I was coming from.

Yeah.

Um, I, I suppose, um, people were— the way architects used to describe it back then was this footprint replacement. So, right, the idea is that you've got a bit of ground you build on, you lift that ground up and put it on the top of the so it's almost a way of minimizing your overall impact, if you like. But, yeah, but it wasn't really about aesthetics, but of course designers are about aesthetics, so yeah, that's very important. But it's a very good question. I mean, the sustainable drainage agenda wasn't really there back in those days, and yet that is an important part of it, isn't it?

So it's really coming to its own now, is it? It's finding its place. I mean, it's, uh, it's going to be something which every, you know, everyone's going to want to do. I was speaking with somebody today about permaculture.

Oh yeah, yeah.

And that seems quite related to this as well, you know. It's maybe less on roofs and walls and things, but you can see how everybody's trying to get nature back into society and back into our living spaces.

And yeah, well, of course permaculture involves people growing, uh, food Yeah, and, uh, you can have a roof garden, of course. Um, so green roofs are not just the lightweight ones, they're also gardens which you can access. And growing food on roofs is a big, big thing, you know, in, uh, across the world. There are people, you know, in, in some parts of the States this is a big deal. On the continent, growing food on buildings. In, in China you have this as well. It is a thing.

And so that's, that's, that's taken off as well.

Yeah, yeah.

Living walls and rain gardens predominantly is a business-oriented thing. That's really what we're talking about here, isn't it?

Yeah, yeah.

How businesses can use it, and then whether that's in public spaces or in private spaces, I guess. So most of the projects, I think, if I understand this correctly, they're public, they're public projects. Well, there was one with PWC we saw there.

Well, there's a mixture. I mean, well, no, we've worked on policy with you know, public bodies like the Mayor of London and so on. But most projects are private projects. So for instance, the David Attenborough Building, which is a refurbished 1970s building owned by the University of Cambridge. And that project, that building is reinforced concrete, so retrofitting is easier than it is on some buildings. It's a very strong building, and the brief there was let's get biodiversity on the building. So, okay, So, you know, that was for University of Cambridge, right? So, you know, it's quite a sophisticated client, but actually, you know, to begin with, there were plans to perhaps have green roofs which weren't as biodiverse as they could be. So our role was to really push that and have a high diversity of planting. So yeah, that's a private project. A lot of the developments in Central London, like the You know, Elephant Park, which is in South London there, Elephant Castle, that's all new housing, that all has green roofs because the planning body, which is the Borough of Southwark, would have— well, they do require green roofs.

Right.

So, you know, that's private. Sometimes people in the client group aren't perhaps aware of this, but they have to do it anyway now in London. So yeah, other large-scale—

There are some mandatory reporting requirements, I think. There are some mandatory reporting requirements coming in now, I think, aren't there?

Yeah, well, there's planning requirements. Yeah, there's planning requirements as well, you know. Um, uh, to get planning permission in central London for a new building, you need to put a green roof on it, right? That's, um, right. Yeah, yeah, yeah. Unless there's a good reason why you can't, right? So it's an expectation, it's the default position there. So in central London, um, there are millions of square meters of green roofs now.

Okay, that's great. And, uh, so obviously they need to be maintained, don't they? So it's all right building it, but then are there— what are the issues around maintaining? Because I can't manage a pot plant, let alone a green roof.

Well, it depends what it is really. So if it's what we call extensive, that is, uh, relatively lightweight, relatively self- sustaining. And so the idea is that you just go up there now and then just to make sure everything's okay, pull up a few unwanted plants. You know, there are plants that tend to spread like Buddleia, and they can cause problems, you know, wind-borne weeds and so on. Pull those up, unblock the drains, and so on. So very minimal, right? No maintenance— that, that's not correct. Minimal maintenance.

But any roof should be looked at Anyway, right, and I suppose there are specific plants, yeah, yeah, themselves to be on a roof.

Yeah, yeah, very low-growing, drought-tolerant. You don't irrigate, it just looks after itself. And that, that's the key to it, having the right drought-tolerant plants, sedums and other wildflowers that don't need much looking after. But of course, if it's a garden, that's something different. You'll need people potentially going there certainly frequently or regularly, just keep an eye on it, because as we know, gardens do fall apart. But a garden is also used quite a bit, isn't it? So, yes, it's not really a burden, it's just an amenity that needs looking after.

I was going to ask, actually, you know, to what extent are these gardens actually used rather than just being, you know, a lawn on top of a building?

Well, you could have lawns, although they're not that common because of course they need to be mown. But most roof gardens are paved areas mixed with seating and planting.

Okay.

And you know, they are very popular. I mean, they're a great place obviously to have a party, have an event.

Okay.

But you'll find that roof gardens in London, I mean, there are one or two open to the public as well. You know, in Fenchurch Street, you've got a roof garden there, which is owned to the public.

Okay.

But most of them are very well used because it's a great spot to have your lunch, a great place to have a meeting during the day, special events. So yeah, it really adds a lot to a building.

Right. Okay. And so what are the challenges then, or what are the prerequisites for having a roof garden? Maybe you're in an older building, a company might be in an older building and think, yeah, we want to do this. Are there some obvious things they could look for to see if, you know, one might fit before they get a consultant in?

Well, yeah, I mean, the first thing you need to know is whether or not you've got the strength in the building to take the weight.

Right.

So before you do anything else, you need a structural engineer to let you know how much loading there is available. You know, quite a lot of older buildings are surprisingly strong. So I worked on a building that used to be a print printing works from the '50s, plenty of strength in there, no problem putting a roof garden on. But of course, other buildings may not have the strength in the structure to take that. So yeah, absolutely, for retrofitting older buildings, that can be a challenge to be able to take all that weight, but it can often be done. I mean, we estimate that you know, a third of the commercial buildings in London could be retrofitted with extensive green roofs. And there are a few clues as well. So for instance, if you see a building with paving slabs on it which are holding down the insulation, that's a common style of roof on a flat roof. Those paving slabs weigh more or less the same as an extensive green roof. So if, so you know already, if you were to swap out swap over the paving slabs with a green roof, you would know, obviously it needs to be confirmed by an engineer, but chances are you can do that. So there's quite a lot of potential for retrofit. And then of course with new building, although there's an extra cost, it shouldn't really be a problem for the architects and structural engineers to design these things into the building. That shouldn't be a problem at all.

Yeah, brilliant. And so we've got the benefit there then of habitat creation. Yep. So that's, you know, energy efficiency as well. So it's a natural insulator up there.

Yeah. Well, yes, but it's better to think of it this way. So when you have soil and vegetation, you in summer, you get evaporative cooling.

Right.

But there's a shade effect, but you get evaporative cooling. So that actively cools a building in summer, having soil vegetation on it.

It's a good point.

So that really is a significant thing. And there's an interesting variation on extensive green roofs called solar green roofs or bio-solar roofs where you combine PVs with the extensive green roof. And that means you get your— you get cooling from the green roof, which increases the efficiency of the PV. So that's a really interesting story and worth having a look at.

Solar panels? Is this solar panels?

Solar panels combined with a green roof, and it's the cooling, uh, which is the thing. And of course, um, the water, the rain that lands on that roof is partially absorbed in that soil, and then it's that which, um, evaporates later on, giving you the cooling.

Right, okay.

So that's the energy side. It's mainly about shade and cooling.

Right. It's great how sort of the infrastructure, the buildings and nature are starting to work together.

Exactly.

Yeah, yeah, that's really, really cool, isn't it? Really Cool.

I love that. It's literally cool. Yeah.

Yeah. So literally cooling. So, you know, and obviously nice space is great for productivity, right? I mean, we all like a nice space to work in, space to work in. Yeah. Living walls. I mean, we're talking about green roofs, there's living walls, there's rain gardens in a minute. Living walls, like vertical gardens.

Yeah.

I guess there must be some limitations as to what, where you can put a living wall. You can't just put one up anywhere.

True, but in some ways there are more possibilities because you can usually find a way to take the weight. So, you know, with a roof, there may be situations where you can't have a green roof, but most walls can be modified to transfer the weight. You know, you can use steel subframes and so on to spread weight to load-bearing parts of the wall, or you can transfer the weight down the wall. So, or you can grow lightweight climbing plants on, on trellises. So there's usually a way of vegetating a wall, right? And it doesn't really— obviously you don't want to cover windows, but it doesn't really matter either what direction the wall is facing in because you can choose plants that are say shade tolerant for north-facing, or, or don't mind the extra sun for south-facing, or, or in between for east and west. So, so there's a, there's a lot of possibilities for vegetating, um, vertically. And of course, the great thing about that is you get the cooling, which we already talked about, but people can see it.

Yeah.

Um, and, and it's relatively inexpensive, um, um, compared to— well, that— well, it depends what it is. If it's just climbing plants, that's very, very inexpensive and easy to look after. If it's what we call, um, modular green walls, intensive green walls, that's a, that's a different story, you know, where you're irrigating, you've got thousands of plants in modules. That, that's a lot more, um, involved. But, you know, still, I still can be a good value for money if— as long as you can afford the maintenance.

And it's really about the aesthetic appeal of it. It's about the working space. It's about creating a nice environment. Obviously, there's the benefits for the environment and cleaning the air as well. But are they growing in popularity? Are more companies doing it?

Yeah, I mean, the first green wall I worked on was at the Westfield Shopping Centre in Shepherd's Bush. I think that was about 2006 or '07. And at the time, the industry for what we call modular green walls didn't exist in the UK. But since then, and we brought products from Canada, I think it was, but since then, there's, you know, several companies have established themselves to provide green walls. You know, there are 3 or 4 quite large companies now doing this and then a few other smaller ones. And, you know, I'm seeing green walls pop up all over the place. Shopping centers now, you'll see green walls, hotels, And then of course the climbing plants on schools. Schools are very, it's very popular because it's a way of, as you say, a way of intercepting air pollution as well. Private dwellings and also interior planting with green walls as well is very popular, just using houseplants but really getting spectacular effects. So I think the agenda there is about health and well-being, you know, lowering blood pressure, um, that kind of thing.

Nice to be around living.

Exactly. Yeah, yeah, yeah.

Nature, we just probably absorb that without even realizing it, you know. Probably calms us down. Yeah, noise reduction as well, I guess. So probably.

Yeah, yeah, yeah, that's right. Um, um, uh, the, the green wall in Shepherd's Bush was really a barrier between the residential, um, area