A new kind of roof coating developed by an Arizona State University spinoff company is having some success in cooling the buildings it’s on.
The firm, called EnKoat, is testing its product at the university’s Polytechnic campus. And the scientists who’ve helped develop it say it could also serve as a moisture barrier, helping increase the lifespan of roofs.
The idea of cool roof technology has been around for a little while now. Narayanan Neithalath, a professor in the School of Sustainable Engineering and the Built Environment at ASU, shares more with The Show about the product and what it does.

Full conversation
NARAYANA NEITHALATH: So right now, what has been developed by EnKoat is a coating system. It’s a, you could do it as a one part, two part coating system, depending on what your application is and how much of an effect that you want. But we can, we have the capability, and we've actually done this in different carrier media.
So now paint and coatings is one carrier media for these, these curable materials, and therefore it's as a coating. But we can do it in a cementitious slurry. We can do it in concretes, like I mentioned earlier. It could be multiple avenues to doing this.
MARK BRODIE: And what have you found so far in terms of how effective this can actually be?
NEITHALATH: So lots of coatings that you have in the market now reduce the temperature within a building by simply reflecting light away, and that is quite effective. You have a whole family of coatings that you have which will just reflect light away, and by that high emissivity that you have for the coating, you have a very good advantage, and you have plenty of them that's available in the market.
What this coating does, in addition to emissivity, it has a tuned, controlled microstructure where there is energy absorption and release within the coating as well. So it gives you the added effect. For example, if you have, you know, external temperatures of the coating on a hot day in Phoenix, when the temperature outside is 110, 115, a roof might be 140 [degrees] F. But if you use a very cool roof reflective coating, you can bring down to 121, 125. This will bring down to, this coating will bring down it even further, down to 100, 105. So you get that, that extra differential because of how the heat is absorbed and released within the microstructure, that's a difference. That's a fundamental difference.
BRODIE: So how is this different from for example, we hear a lot about cool pavement, which does a good job of making the surface temperature cooler, but doesn't do such a great job of making things because it makes things feel warmer, like, if you're walking on top of it. Like, how is this product different, and how maybe, how does it work differently than some of the other technologies that are out there?
NEITHALATH: Right. So, a very interesting question, right? So that's why I said, if you just reflect light off it, you will have a cooler, you know, you can get the internal cooler, but when you walk on top of it, the surface is going to be hot because it's emitting a lot of energy, right? Whereas what this material does is it has a certain capacity to absorb and store heat and release heat later on, so you basically delay the heat release from an instantaneous release point of view, so that you get a better benefit.
So to give you, give you how this works if you apply it on a roof, typically what you do is you drop the temperature of the building inside, but you also delay when that peak temperature inside that room is reached, we call it peak load shifting. So it's very good for electrical utilities, because now not everybody is hitting their peak load at the same time. That helps the utility companies manage their loads better.
BRODIE: So it almost kind of sounds a little bit like a battery, in the sense that it is absorbing the heat and then releases it later. Presumably, the goal would be to release it after dark, when it's cooled down a little bit?
NEITHALATH: Perfect. So, all of these materials that we have included within these coatings have temperature ranges in which they are active and they are dormant. The whole idea is to tune those, so the same coating that you use in Phoenix will not be applicable in Chicago. The same thing that's applicable in Chicago will not be applicable in Los Angeles.
You have to tune it to where the peak temperatures are and when the peak temperatures are. And similarly, what is applicable for Phoenix in summer is not going to be applicable for Phoenix in winter, but for example, we don't really need so much heat control in winter, so that's OK. But again, based on the climate, you have to tweak it. And therefore it is, I wouldn't really call it a battery, but yeah, it has some, some components of heat storage and release.
BRODIE: Yes, I've read somebody describe this as almost like an ice pack in a cooler that kind of goes from solid to a more liquid state. How exactly does that function?
NEITHALATH: Yeah, that's exactly how it does. I mean, wouldn't be, you know, solid, total solid to a total liquid. But some of these phase transformations happen where energy is absorbed in transforming the face. For example, if you are cooling water, if you are making it into ice, you give it energy, and energy gets absorbed into it, and then when you provide it more energy, it melts away, right?
So similarly, this material also, or whatever we have tuned within these coatings also have the capability to change from liquid to solid and solid to liquid. So when it absorbs heat, it changes from solid to liquid. When it releases heat, it becomes liquid to solid. So that transformation changes some of the heat transfer aspects, and if you can tailor it correctly with the appropriate thickness and the appropriate temperature range that you want for the application, you can influence the internal temperature in the buildings quite a bit.
BRODIE: So assuming that this continues to work the way that you expect it will, how big of a role do you think this product and this technology could play in the ongoing effort to try to mitigate the effects of heat and maybe bring down the temperature a little bit?
NEITHALATH: I think it's important, right? If you look at a city like Phoenix, we have a tremendous built-up roof area, especially in a place like Phoenix, where we are horizontally expanding rather than vertically, right? As compared to many other cities that go vertically up, we are a horizontally expanding city, which means we are creating a lot more surface areas, and a lot more surface areas where where heat gets trapped in, heat gets absorbed in.
So these kinds of coatings, not just this coating, but this family of coatings, and there are several other sister technologies also that do similar benefit, but the fundamental science is different. But all of these technologies, I think, are very, very critical in making sure that we have a built environment that is resilient to the high temperatures that we are going to see even moving on further in the next five, 10, 15, 20 years.