This is 99% invisible. I'm Roman Mars. This winter is going to be brutal. I mean, it is just going to suck.

And if you're like me, you've been spending a lot of time at homes in March, and it's starting to feel a little claustrophobic, maybe more than a little, a lot claustrophobic.

Though, if you think about it, were you actually going outside all that much before the pandemic?

Modern humans are essentially an indoor species. We spend roughly 90% of our time indoors, and that was before the pandemic hit.

This is author Emily Antis.

And my book is The Great Indores, The Surprising Science of How Buildings Shape Our Behavior, Health and Happiness.

Emily's book looks at how our indoor spaces are actually a giant mystery.

There is so much we don't know. Like, there are thousands of bacteria and microbes living inside our homes, and we haven't really studied them.

So, you know, we spend so much time in these places that we don't think of them as exotic or interesting.

You know, if you're an ecologist, you want to go to the Amazon or to Antarctica, and maybe you're not that interested in the ecosystems that are in our homes.

So, there's all this complexity that we're just scratching the surface of.

Today, as we head into a winter lockdown, we'll talk to Emily about how sunlight and ventilation and the tiny, creepy crawly things in our homes can influence our health and well-being, and how we can use design to make our indoor spaces so much better.

So, let's talk about these microbes, which is the creepy crawly as part of your book.

We haven't studied the bacteria and microbes that live inside our homes all that much.

What is living there? How bad is it? Like, what kind of a forest am I living in?

Yeah, well, so, one study to start to quantify this comes from North Carolina, and they studied several dozen homes there, and they found that on average, the homes housed 2,000 different types of microbes.

So, that is mostly bacteria, but it also includes some fungi, and it's actually more diverse inside our homes and outside them, and that's because the microbes are coming from a couple of different sources.

So, the vast majority of bacteria in our homes, at least, are coming from us, so we now know that our bodies are covered with and full of microbes, and when we move around to space, we are shedding them constantly.

So, that's a large part of what's in our homes, but then there are also species that live in our homes.

You know, maybe they're growing in the plumbing, or they're growing in the insulation. One of my favorite home environments is the extreme environment of the dishwasher or the washing machine.

So, if you think about what's happening in there, it's mostly bone dry, which microbes don't like, but then every once in a while, it gets completely saturated with water, it gets real hot, you put detergent in it, and it turns out that's selected for these strange kinds of black yeasts that don't look anything like any other yeasts scientists have found anywhere.

So, it seems to be this unique ecosystem. And then, finally, we have the microbes that are drifting in from outdoors, so things that live in the soil or in water, and it attaches to us, or it comes in through an open door window.

...