Emily Elias: As the philosopher Rob Thomas from Mashbox 20 once said, “man, it’s a hot one”. I’ll spare you the rest of the lyrics to ‘Smooth’, but summer is here. And on this episode of the Oxford Sparks Big Questions Podcast, we are asking, how do I keep my house cool without cranking on the air conditioning?

Hello, I’m Emily Elias, and this is the show where we seek out the brightest minds at the University of Oxford, and we ask them the big questions. And for this one, we have found a researcher who’s pretty cool.

Nicole Miranda: My name is Nicole Miranda. I am a senior researcher at the University of Oxford, specifically in the Engineering Department, and looking at sustainable cooling.

Emily: Okay, so sustainable cooling. So you’re a cool lady. So the reason we have you here today is because obviously we’re in the thralls of summer. There are heat waves forecasted. It is gonna be a hot one. How do we stay cool?

So I wanted to kind of approach this from a couple different ways. First of all, let’s assume that, you know, I’m a renter, I don’t have a ton of money. What can I do to stay cool in the hot months?

Nicole: Well, it’s always recommended to go through a passive first approach. So that means not giving in to the urge of running to the supermarket or a shop, and getting an air conditioner, because air conditioners are very energy intensive and carbon intensive. Now that carbon intensity is falling because the electricity is getting greener, however, it’s still going to be costly. So a passive burst approach means how we can cool ourselves without using intensive energy, using shades, using water bodies, using vegetation, things that can help us in a more cost effective way, but also that are quite effective. So we always recommend a passive first. And if you’re a renter, you would find that it’s a bit difficult to do things that are embedded in the building because you’re not the owner of the house.

Emily: Exactly. If I was all of a sudden installed, air conditioning, not only would I be out of pocket, but my landlord would probably be pretty annoyed with me.

Nicole: Exactly. So you should always talk to your landlord, obviously, because there is efficient ways of putting shading outside so that you cover the heat gains through windows.

Emily: So is blocking the sun like my number one go to thing that I should be worried about?

Nicole: Yes! So, within the passive solutions, there’s many options. One is blocking the sun, and easy things like drawing the curtains when the sun is outside is very useful. However, there’s another one that we here in the UK love to do, which is opening the windows, and that’s really effective. So if you open a window on one side of the house or room, and then another window on the other side, you get this lovely cross ventilation, and that makes wind go through the house and gives you a nice thermal comfort effect.

Emily: Thermal comfort, is that like fancy researcher for breeze?

Nicole: Oh, yeah. Well, it’s like, how are you comfortable regarding temperature, humidity and the wind around you? Are you thermally comfort, that’s what it embraces.

Emily: Yeah, thermal comfort. Learn something new every day.

Nicole: Yeah. So ventilation is a really important one, but you just need to be careful when you’re opening windows, because if there’s no breeze outside and actually it’s hotter outside than inside, you’re better off keeping that window shut. And that’s a common mistake we do here. We think, oh, it’s hot and we open the windows. But actually, it’s sometimes more convenient to keep the hotter temperatures outside and shield your house.

Emily: Is there like, a better window to open? Like, so say in my house, there’s a sunny side of it, and there’s like, a shady side of my house. Should I open windows that are on the sunny side of the house, or should I open windows on the shady side of the house?

Nicole: Well, you could combine opening windows that are on opposite side of the house, because that will allow a ventilation, like, from one window to the other. So it advances through the house, right? The wind moves and that’s what you want. But on the sunny side, I would draw the curtain so that that sun doesn’t come in directly. So you still have the wind able to escape the room and the house, but you’re shading yourself from those heat gains from the sun.

Emily: And it just feels kind of like antisocial in the summer to have your windows closed and, your curtains drawn. But that is, that can be, I guess, in some instances, the best solution?

Nicole: Absolutely, yeah. If you see in more extreme heats in Africa, many houses have tiny windows, and that’s to protect them from the heat. And so they’re quite dark inside and there’s a lot of other issues with that. But to combat the extreme heat, it’s lowering those heat gains of the windows, of the opening.

Emily: Okay, now let’s just imagine I have a tiny bit more money and I can splash out on a device. what should I put my money towards? Should I go for a fan that does, like, 10,000 things and has a computer built into it, or should I just grab a really cool bucket and fill it with water and ice?

Nicole: Interesting. So I think a fan is a very smart way of cooling, especially here in the UK, because it gets hot, but it’s those couple of days in the year where it’s really uncomfortable. So if you help yourself with a fan and it, can be one of those mobile ones that you move it with you around the house or, you know, something a bit more flexible to use, that’s a really good solution.

And you see cases like in India, which they have extreme heat throughout the year and they have fans on their ceilings and they have fans that are on the windows. And it’s a big fan culture. So fans are definitely a good option.

Now, a big bucket of ice, just to go back to that one, isn’t always the best solution because the UK is quite humid at times. And so if we don’t have dry air around us to absorb that humidity that the bucket of ice and water is producing, then it’s just going to make us more uncomfortable. We’re going to get more humid, and that’s not great for that thermal comfort that we were talking about.

But in the right conditions, evaporative cooling, which is the bucket of ice and water, is quite effective. So we have to start learning how to monitor humidity. If you go out to Met Office, it gives you humidity.

Emily: Any fine weather app will provide you what the humidity is pretty much.

Nicole: Yeah, yeah.

Emily: Okay. Now, you are obviously in a different area of science where you’re not studying buckets of ice, necessarily. You’re looking more at houses themselves. So imagine that I am Kevin McCloud on Grand Designs. I’m building a massive, environmentally friendly house because I’ve got so much money in my pockets to burn. What should I be looking at if I was going to be knocking down walls and trying to make my house as energy efficient as possible?

Nicole: So, yeah, that atually, I’d like to make an important point here. The UK has very good new build regulations. So if you’re building a new house, there is regulations and codes to make that house resilient to overheating. However, in the case that you’re saying, it’s like a retrofit issue, and unfortunately, that’s where we need more efforts made because most houses that’ll be here in 50 years are already built and those houses are not necessarily following the new regulation because they were built a while back.

So we need to focus on programs for retrofitting our houses and our beautiful buildings because we’ve got great historical buildings, but they’re usually made traditionally to keep heat in because the winters are harsher than the summers.

As climate change continues to have its effect, we’re going to have more and more hot weather here in the UK. Unfortunately. it seems that we’re going to be one of the top countries to have an increase in relative change for cooling needs. And that means, yeah, we need to look at what do we do with our retrofitting. So a passive first approach should be applied for retrofitting as well.

And that could include ventilation. So if you have windows that are only on one side of the house and they’re not connected to the other side, there should be. If you’re knocking down walls, think of that. Think of, like, how are we going to make this breeze pass when it’s needed? Think of insulation. It’s a great retrofit solution that is commonly associated with heating. But insulation is fantastic for cooling as well because it allows you to put a barrier that will divide the outside from the inside. So if it’s really hot outside and you’ve managed to cool inside, that cool, which isn’t a very scientific term, will remain inside better, because it’s encapsulateI.

Emily: So similar to, like a cooler, like an ice bag. When you’re going to the park with, like, your beers or your soda pops, shall we say? It’s the same sort of principle. Like, if you put a bunch of ice in it, the insulator keeps the cool in as much as if you put something hot in it, it keeps the hot in.

Nicole: Absolutely. and then I’d also recommend looking at those new regulation. It’s part of the building regulate, and there’s great ideas in there. Like, for example, on top of windows, to just put a horizontal, call it wing, that allows for shading. So when the sun is really high up and it’s at the hottest time of the day, those windows are really shaded, they’re not being hit by those solar gains. So there’s tons of things we can do with our retrofitting in the UK.

Emily: And I suppose, like, if you have like a giant sort of shade built into the building, in the winter, it’s not really going to hurt anything, and in the summer, you’re going to benefit from the shade off of it.

Nicole: Absolutely. So in the winter, the sun is lower, so you’re still going to be able to benefit from those heat gains because then you want them in and the sun is lower anyway. But in the summer, when the sun is higher, you want to shade the right angles of the sun rays, right?

Emily: So it’s a hot, hot summer. What are you, Nicole Miranda, doing to stay cool?

Nicole: I am very much paying attention to the temperature outside to know when to close the window. So in the morning, I wake up, it’s nice and fresh, usually before the heat comes in, and I open all the windows that I can. And if I’m working from home, I’ll keep an eye out and as soon as I see the sun moving through the house, I start drawing curtains where the sun is hitting, and I start opening them where it’s shaded.

So I keep an eye on the temperature. If I take a break, a coffee break, I’ll go outside. See, okay, it’s getting too hot outside, so I’m going to start shutting all the windows now to keep that fresh breeze from the morning inside. I’m quite lucky because the walls in my house are quite thick. And so that’s quite convenient, too, to keep that heat outside. But it’s all curtains and windows strategy.

Emily: That seems like a good strategy.

Nicole: Yeah. And cold drinks, of course. Yes, that a coffee break would be an iced coffee. And we also have fans and we turn the fans on at night. That just helps bring the fresh air. So we put the fans on the staircase to just pull that cool air from the bottom of the house up and it’s quite effective, yeah.

Emily: And what is your policy on popsicles and ice cream sandwiches?

Nicole: Absolutely. Why not? Delicious and refreshing.

Emily: This podcast was brought to you by Oxford Sparks from the University of Oxford with music by John Lyons and a special thanks to Dr Nicole Miranda.

We’re getting ready for our next season of the Big Questions Podcast which will start up in autumn when it’s a bit cooler. So if you’ve got a big question and you’d like it answered, reach out to us. We are on the internet @OxfordSparks and we have a website oxfordsparks.ox.ac.uk.

I’ve said it once, said it before. I’ll say a thousand times. Come on guys, send us your questions. I’m Emily Elias. Bye for now.