Could you provide me with an overview of the work GCCA is doing around the world on the issue of Urban Heat Island?

Kurt Shickman

We are a non-profit, and we do a lot on urban heat island mitigation, but the main focus is on reflective surfaces – roofs or walls. There has been increasing recognition in hot and cooler cities that extreme heat is a major problem, with significant research in over a year and a half that highlights the cost of inaction for cities to quantify the meaning the full way, not just to avoid the negative but to achieve positive outcomes. Estrada et al 2017, Nature, Climate Change – found that heat doubled the cost of local climate change. A median city of 1,700 studied would pay an additional 5.6% of its economic output by 2100, if heat goes unchecked.

Has awareness grown, owing to recognition of the economic paybacks that adoption of Urban Heat Island strategies might have for each respective country?
At first, cool roofs were driven by energy considerations and energy policy/codes – that value energy savings. When you peel back the onion and look at the cost benefit, you see something in the order of one-and-a-half to one, in favour of cool roofs on base energy, not even peak demand reduction. The cost benefit varies a lot by climate but is nearly always above 1:1, even in colder areas. In the US, the economic payback is anywhere between zero and six years on base energy demand reduction alone.
For energy savings with health requirements, it’s between 7x and 12x compared to the cost. We can look at data that shows reduced heat deaths and hospital visits. In a paper, published in the Journal of Climate Change , they found that a moderate deployment of a cool roof and pavement programme would have a payback 12 times its cost. This includes maintenance.
There is a tremendous amount of benefit. The challenge that must be eliminated is the fact that a lot of the value is hidden from decisionmakers. It isn’t apparent on profit and loss statements. There’s a huge role here for policy to make people aware of these benefits and also to transfer the benefit to decision-makers through incentives. Until we realise the benefit, we won’t have adoption at the pace we need. We are doing a lot to raise awareness, to make cities aware of the benefits beyond what they are looking for.

What do you consider to be the bottlenecks in this regard?
As you can imagine, if you are a mayor, there is a lot of bureaucracy entrenched in agency infrastructure that have to be brought in the same room and that can be a real challenge. Heat is a weird topic in that sense. In New York, in the Urban Heat Island [meetings], aside from us there are also people from New York Emergency Services, police, city architects and planners, health department, community groups, researchers, universities – all these different groups have different ways of talking about what they do. It’s getting folks to think about it, as a common problem. That is easy to say but challenging to put into practice.
It’s almost never the numbers that drive it – it’s the stories. I won’t say the city, but I had a conversation with the public-safety group – the police, fire [department] and first responders. They started to look at the issue of heat in cities and found that there is a statistically significant increase in domestic violence calls in hotter areas. There is an actual impact on crime, if we do something about the heat. There’s a lot of different ways to look at it, there’s no one message.

Could you elaborate further on the role that policy plays in this regard and the need for collaboration between the public and private sectors?
Policy doesn’t mean regulating, it could be incentivising. There are different ways to structure policy, some voluntary and some involuntarily – a mix of the two is needed. So far, no one is setting the ceiling, they are setting the floor. In most places, with a few exceptions, bringing up the floor doesn’t hurt the manufacturers.

We all default towards what is easy, to use and get benefit from one technology and strategy – but it’s a systems approach. A lot of things need to work in tandem to make change. That’s hard to do without collaboration among policy makers, researchers, to look at [the issue in a] more systematic way.
We don’t go and say, just do a cool roof; it has to be symbiotic with Green infrastructure. You can’t go in with one solution; you need a policy-maker to spur that conversation, especially in the developing world. It’s also about the industry, manufacturer and the people on the ground, including the construction industry; it is important to make sure their voices are heard.

Could you comment on the uptake of adoption of cool roofs and pavements today, among contractors and consultants across the United States?
We are seeing two big changes in the market over the last 10 years. With regard to the membrane roofing, thermal plastic membranes that are placed on commercial buildings, there is the EPDM rubber, primarily black, and TPO and PVC, primarily white. It is naturally that colour. What we have seen, in the last 10 years is a flip-flop in the market, from being predominantly EPDM-dominated, to one dominated by TPO and PVC. This is driven by positive
economics but also the fact that a cool roof is a LEED credit with the USGBC. So in UHI, there is a huge shift in what’s being specified for commercial roofs. I will say from 35 to 65 the shift went from 68 to 32 in favour of white products. Not just in the warm climates but all the way up to the Canadian market there is a fundamental shift. Over the last five years, we have a couple of cities that have taken the next step.
In the US, in most of our residential peak roves we mostly use asphalt shingles, like black asphalt, some tar and granules. Cool granules have been in the market but were prohibitively expensive. Some cities mandated cool roofs for residential developments. Two markets actually spurred a tremendous amount of innovation, to bring a product at a more mid-tiered price. There is also a lot of growth in areas outside where it is mandated. LA mandated
cool roofs in 2015. A manufacturer told me they sold more cool roof shingles in a city outside LA, which is not under that regulation, than in LA. We are starting to see people do something about it.

Have you observed the same positive trend in cool pavements, as you do in cool roofs?
Cool pavements are much trickier. There is a lot less human interaction with the roof than pavement. If you reflect light from the pavement, you may increase natural lighting, which reduces lighting load but increases cooling load, because more solar radiation enters a building. It could have more, or less, impact on pedestrians. You may decrease temperatures on the street level but increase thermal load on pedestrians.
LA, Melbourne and Tokyo are doing a lot. They find the best conditions you can put a pedestrian in are cool pavements with ample shade trees and structure-reflected. Shady spaces [offer] the biggest reduction on a pedestrian’s thermal load. It’s worse when you have barren area. The same intervention could be for the best or for the worst. It depends – it’s really not a one size fits all.
However, we can’t just not address pavements – they are a huge part of our cities. On average, one in every three metres is some kind of pavement. There is a significant, impactful urban heat island mitigation benefit from cool pavements, but where we are, in terms of the technology here, there is also a global warming impact that may outweigh the benefits. There is a need to innovate. When you turn a surface from dark to light you create a cooling effect on earth but also a warming impact on the atmosphere. If I create this cooling effect on a road, from dark to light that cancels the warming effect of x tonnes of greenhouse gases in the atmosphere. There is a sustainable way to look at this. When you factor [the global warming effect on the benefits], it trumps it 150 times.
A lot needs to be done on cool pavements. We need to be mindful of how they are applied– specifically, as well. If your goal is urban heat island mitigation, there is tremendous benefit. If you were to ask what I recommend as a minimum, for cool roofs, I would say “yes” in nearly every climate zone, unequivocally. For the same question on pavements, I wouldn’t say that’s my answer. I’m not against it. For me, what I would like is the transportation department to study and look at cool pavements. We do need to study the local-level impact of cool pavements. No question, we need an UHI solution for pavements. It’s too big a part of the cities, but we can’t just say, “Make them all light coloured”. We need a much better local understanding.

Hannah Jo Uy is Assistant Editor at Climate Control Middle East magazine. She may be contacted at hannah@cpi-industry.com