Interview response from Peter Massini
Plant selection is a really interesting question. There are various ways to look at this.
The first consideration is what sorts of plants are going to thrive in what can be quite difficult locations due to factors like shading, exposure, dessication, and air turbulence in urban environments and also factor in issues such as climate change.
The Right Trees for a Changing Climate website and the Trees and Design Action Group Species Selection for Green Infrastructureare useful resources. The Trees and Design Action Group has other good guidance documents on other issues which can be downloaded here.
For green roofs its primarily about specify different soil depths and substrates to achieve what you want from the roof. Within reason you can grow the same plants on a roof as you could grow in a garden or which would grow in the wild – large shrubs and trees and wetland plants excepted unless a very special green roof has been designed. Typical plants for green roofs include those that would normally be planted in a Mediterranean style garden or gravel garden. For roofs designed specifically for wildlife the British Flora Biodiverse Green Roof guide includes a list of native suitable plants suitable for green roofs.
For green walls plants have to be more robust and hardy. Often evergreen species are used, many of which are non-natives, including: harts tounge fern; box-leaved honeysuckle; hard fern; common ivy, big blue lilyturf, spindle and Mexican fleabane Some additional plants are listed here https://www.gardenersworld.com/plants/plants-for-a-living-wall/.
For carbon Barcham Trees and Treeconomics have just created carbon performance certificates for the trees they supply.
Regarding air quality there is currently a lot of research being undertaken to identify how to use vegetation and which plants perform best with.
Transcript of Interview with Dusty Gedge, Green roof specialist
Interview with Wendy Allen, a UK garden designer who specialises in rain gardens
A.R: My project is based on the selected area of a hospital site ( see map) and there are some surface areas likely to be flooding and I thought a rain garden would be a potential solution. As the garden would often be shaded by the hospital & trees, what plants would you suggest? – Does this vary with sunlight exposure?
W.A : I wouldn’t use your circled area as a rain garden / too much tree root area would be affected. SHADED AREAS WITH GROUND LEVEL PLANTING TEND TO REMAIN MOIST – a search for ‘plants for moist shade, or woodland plants, should all work. Evergreen ferns (Polystichum var. Work well) and If planting in a rain planter or close to base of a wall, use plants for dry shade. Carex and Bergenia are two examples.
A.R: I really liked your school rain gardens where the rain garden had sculptural elements that were also contributing to the function, do you have any suggestion how I could integrate these sorts of elements into my design without causing disruption to the surrounding roads?
W.A: Overhead channels are a good way to achieve this, or use fluted channels at surface.
A.R: Do you have any other suggestions for the rain garden or any things I should consider?
W.A: Consider permeable paving for parking areas. Create rain planters at base of all downpipes to capture and slow the flow.
A.R: Do you have a plant list that could help me suggest plant species across my design? I was also thinking that storm water planters could also be integrated else where across the site. Are the certain plants more suited to planters?
W.A: The smaller plants in list in UK rain garden guide will also work in planters – Carex Ice Dance my no. 1. Knoll Gardens website have lists of grasses for different aspects.
A.R: Is there anything else you think I should consider, or you think I may have overlooked?
W.A: Work with natural levels on site if doing a rain garden. Where is the lowest point? Where will a rain garden overflow to? Urban Design London guide as referenced in my presentation is a great guide.
Email Interview Questions With Gil Schalom, a low energy ecological architect & Penney Poyzer, an environmentalist
- How do you monitor the change in energy / how successful your solutions were? – Carbon footprint, energy , heat etc.
G.S: Generally on a domestic scale retrofit the houses are monitored via the utility bills and final air tightness results. The feedback on success is usually this plus client satisfaction and reports on comfort and wellbeing levels. It would be good to be able to monitor temperatures, relative humidity and moisture and CO2 levels but there usually isn’t the budget for these and they could be done later. A co-heating test would be the ultimate but this is generally far too expensive and invasive, so best to keep things simple.
- Are you aware of any policies around green infrastructure around Nottingham (aside form the carbon neutral strategy) and are you involved in that in anyway?
G.S I am not involved in any of this but I know Penney was heavily involved in producing the Well Being Design Guide https://www.dqfnottingham.org.uk/wellbeing-design-guide, Penney can tell you more.
P.P Have you looked at the City Council’s website? There is a search tool. The Wellbeing Design Guide – and other design guides are set out very clearly. I co- authored the wellbeing design guide which is based on a nature first approach.
I am the person who came up the concept behind the Green Quarter which is a proposal for a sustainable mixed use vision for the Broadmarsh centre. https://drive.google.com/file/d/18waQTC-iezbAjTPrdh06tsxVSY-OW7g_/view
I did a google search for green infrastructure for Nottingham city council – which you could have done very easily yourself.
https://www.nottinghamcity.gov.uk/information-for-residents/community/investing-in-green- infrastructure/
- Do you have any examples of green infrastructure that you integrate into projects?
G.S As I say, my projects are usually one-off domestic and so offer limited opportunity to include ‘infrastructure’, depending on how you define the word. Many of my projects include living roofs and some form of sustainable urban drainage, plus may include PV solar panels that contribute energy to the grid, and efficient all-electric houses contribute to better local air quality but beyond that, looking at street and town scale infrastructure is not generally appropriate for my area of work.
- How would you describe the relationship between green infrastructure and carbon neutral solutions?
G.S I’m not sure how to answer this. I also don’t really like the
term ‘carbon neutral’ as it is too wooly and could imply doing things really badly and wastefully locally while offsetting carbon via totally unrelated projects elsewhere as an extreme example, hardly a sustainable approach! I prefer to talk about deep energy efficiency (refurb or new build) and low or zero carbon technology as this puts the onus on local solutions. Green infrastructure is such a broad term that could encompass anything from trees and biodiversity, to sustainable drainage, composting and sewage, circular systems, to district heating, to renewable energy to local power grids with their own generating and storage, to EV charging, vehicle to grid schemes to trams, cycle lanes and other more sustainable transport, to solar farms and large scale wind turbines, etc. etc., Localising the food system and reducing food waste and local green jobs are also a massive part of the picture (Penney’s area of expertise). Even fast broadband could be considered green infrastructure if it reduces transport requirements, so the question is far too huge and general for me to answer meaningfully. My area is energy efficient housing including retrofit and of course every single project successfully delivered will contribute to reduction in resources such as fossil fuel and water. Greening the landscape with trees and other well considered vegetation can sequester carbon in the soil, produce local food growing opportunities which reduces transportation and plastic packaging etc. and reduce flood risk, which itself can reduce carbon emissions. On site renewables and EV charging points can reduce the carbon emissions in transport. That’s as far as my scale of work extends. Larger scale projects can encompass larger scale thinking.
- What are things to consider when retrofitting older buildings?
G.S I will comment on dwellings in a northern European climate, as this is my area, larger buildings and different building types and climate regions may encompass other
principles. Minimising energy in use through a fabric first approach is key – i.e. minimise how much energy the building requires to heat and cool is a win-win and far better than simply slapping on the renewables. This usually includes substantial amounts of insulation installed with care so that the insulation is continuous with no gaps (thermal bridges). High performance glazing, usually triple glazing with very good air tightness but also where possible designed to optimise passive solar gain (not too much in summer to avoid overheating, not too little in winter). Air tightness is also crucial, as is providing some form of mechanical ventilation, usually with heat recovery in this climate. Working hard to achieve good results for these is the very best starting point. However, heritage and context are crucial and sometimes it is too challenging to achieve all of this, for example in some Conservation Areas, listed buildings, etc. so the approach needs to be on an individual basis. The implications of the retrofit measures on the health of the building (moisture, condensation, fresh air, water penetration, daylight, etc) all need to be carefully considered. Next also look at embodied energy in the materials and methods used to achieve it (minimise steel, concrete and plastic). This is often inherent in retrofitting as much of the embodied energy is in the retained parts of the building but look at applying these principles to what is added as well. Next look at LZC (low and zero carbon) ways to provide the small amount of heat required, e.g avoid fossil fuel appliances like gas boilers, favour heat pumps or district heating etc. Only then look at potential for providing on site renewables and possible energy storage like batteries if budget allows.
- Do you have an suggestions I could consider for my hospital project?
G.S Sorry, it is not my area. I do know there is a Passivhaus hospital recently built in Germany and a medical building in Leicester.