- The road to hell is paved with good intentions.

- When we bring these new toys into our home, they produce things that we might not know.

- They now have HD cameras built into the televisions.

- Indoor environments are hugely complex chemical reactors.

- Construction is a bit of a game of dominoes.

- A lot of these homes, they will look nice in the end.

That's exactly why people don't know the difference.

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- In trying to fix our problems, are we actually just rearranging them?

- For every product advertised to fix something in your home, there is its shadow.

The byproduct you might not suspect.

- Every home is a system and all the parts interact through physics, chemistry, and microbiology.

But since we can't predict the specific combination of products in your home, we can't predict their interactions.

- But there are ways to buy and even build in a less chaotic way that gives us more control over the hazards we face every day.

(solemn music) - [Grace] It's the shields we build and the risks we take.

It's the disasters that will test us and what will grow from them.

It's real life.

And the physics, chemistry, and microbiology of the science of homes.

- Okay, so the interesting thing about the indoor environment is that there are lots and lots of products out there to improve the indoor environment.

There's almost a truism in indoor air that you shouldn't add anything to indoor air, and yet there are so many products that do just that.

In some cases we only have a little bit of direct evidence of their harm.

In other cases, we have a lot of evidence.

People do these things because they think it's good or because it makes them feel better and it actually potentially causes harm.

- We mocked up an entire home almost in one of our large chambers in the back of our research lab.

So we studied washing machines, we studied dishwashers, we mocked up a shower.

We even had a bathtub that would fill up and we had a human simulating puppet kind of simulating a washing event of somebody sitting in a bathtub.

We studied what happens when you use different consumer products in your home, when you have an ozone source in the home.

And it was one of the first studies that showed how different chemicals released from consumer products interact with ozone and form bursts of particles in the air, it really opened our eyes to the amount of chemistry that can actually occur when you have two things coming together in a home, somebody using an air freshener, a solid air freshener or a spray air freshener, or even somebody wearing a nice scented perfume in the presence of an ozone source inside of the home, - Ozone is part of pollution.

Just part of our everyday lives.

Recent discoveries show that we can actually carry ozone around in our skin oil and off gas it somewhere else.

One place we're exposed to a lot of it is flying at 35,000 feet where most single aisle planes are exposing you to ozone levels well above those in a polluted city.

We still wear N95 face masks when we fly because first of all, we live in an ocean of air and it gets gross, but also we monitor carbon dioxide when we travel as a proxy for all the other stuff coming out of the people around us.

We see sky high levels of breath byproduct when we're sitting on the tarmac, and it's not what I'd call healthy.

Even when the ventilation kicks back on.

Even a marvel of technology like an aircraft can be better tuned for performance.

Building and owning performance tuned homes sometimes to us, seems a little bit like an elite thing and more and more people are working on the challenge of making this stuff affordable for everyone.

I'm about to introduce you to somebody who is one of my favorite builders in the entire country, Scott True from Dimora Homes, Bastrop, Texas.

Scott.

- With housing being difficult to afford, how do we make high performance affordable?

- It's a big challenge and one that I'm trying to figure out.

I'm implementing a lot of different things from homes that have higher budgets and just trying to figure out which items have the greatest impact, the most bang for your buck.

But I also have to combine that with what are the skills of the people building affordable homes?

It can seem simple, in some ways it is, but I think the difficult thing is finding methods that the local workers can and are willing to do.

I mean, that goes for everything that we do.

We've gotta find ways of building that can be done by these people that live here.

- [Corbett] You may have heard we can skip all that hard work and just get our homes 3D printed, but remember, there are no silver bullets and every product comes with byproducts.

All right, Jorge, show us what you got.

- So 3D printers are very popular.

You can even buy them as toys for your kids, and I find them very interesting.

But we have to remember that when we bring these new technologies and new toys into our home, they produce things that we might not know.

You can definitely smell the chemicals cuffing off a 3D printer.

As scientists, we're not saying that you can't have these things in your home.

We're not saying you can't have candles, you can't have products in your home.

You can't have 3D printers in your home.

When you bring contaminants such as these into your home, you have to counterbalance it with ventilation, again, as long as it's not polluted.

So that could be opening a window while you're doing these activities.

That could be turning on a kitchen exhaust fan, that could be putting a fan in a window and taking that polluted air out of your home, and that's really for your own benefit, for your long-term health to do these things.

- The fundamental basis for keeping the air clean in our homes almost always comes back to a filter.

It strains the air so that particles get removed.

- Oftentimes people will ask me about air cleaners that will add things to the air, and sometimes they can actually add harmful chemical compounds such as ozone that may be associated with health effects in and of themselves, and they might also not be effective.

- You should never be present when there's an ozone generator of any kind on.

You should probably never purchase an ozone generator for personal use in your house.

They rarely do what they're supposed to do or what they claim to do.

One of the most interesting cases that I was ever involved with involved the guitar player in a very well-known rock and roll band.

His neighbor wanted to put in a helicopter pad on his property, and this particular person who called me had fought his neighbor.

The neighbor hired somebody to spray skunk oil into the individual who called me's car and house and property.

This person spoke with his insurance company.

The insurance company said, call this company.

They'll come in and make the smell go away.

Well, the company that came into his home set up, to my recollection, I believe, six commercial size ozone generators, switched them all on full blast and forgot to tell the family they shouldn't be in the house when these things were switched on.

The person had a three-year-old daughter, a dog, a wife and himself who all became sick.

It also harmed a lot of works of art.

It degraded a lot of rubber in the house, rubber gaskets.

They had leaky water heaters because of ozone reacting with rubber.

So it really damaged the house in my opinion, permanently.

- Ozone does have a utility.

We use it in the lab for for disinfecting things.

It's used in some medical context for disinfection.

It's used in some swimming pools as an alternative to chlorine for disinfection.

It's that fresh scent.

We often associate it with like a thunderstorm on a mountain kind of thing.

It smells good.

I think most people think ozone smells good.

The dark side or the problem is that every textile, every rubber, every piece of plastic, a linoleum flooring, everything indoors reacts with ozone, and then you get this whole new chemical soup and it's different in every house.

And even if people do the right thing and make sure there's no people around, ozone reacts with all that stuff and forms other stuff, which can last for a long, long time.

- The chemistry in our buildings is very complex.

If you're trying to change the air chemistry in a building, you have to do it pretty quickly.

You have maybe a couple of hours for that chemistry to occur.

When we try to intentionally change the chemistry in a space, we may get unexpected products, unexpected results, or there may not be enough time to realize a substantial effect.

So it's actually a very challenging thing to do, to intentionally control the chemistry in an environment as complex as our indoor spaces.

That's really a hot topic that we need to study a little bit more.

- There was this condo in downtown Toronto and we were monitoring the particle concentrations for a year, and every day at midnight, the concentration would start going up and up and up and up.

You know, it would go up for a few hours and then it would slowly start declining after that.

Every day like clockwork.

And I came up with all these ideas, what it must be, but nothing really made sense.

And then it turns out it was this little essential oil diffuser.

The person ran it on a timer both to get the humidification benefit as well as mainly the scent out of it.

And it was creating these particle concentrations that I can only describe as like what you would have in a polluted city every night while they were sleeping.

And you know, that got us really interested in what are these things.

And so essentially it's like a little ultrasonic humidifier, very small, put a little bit of water in, a little bit of your favorite essential oil.

The oil itself causes a lot of particles to form.

And then also the water we use, there's a bunch of minerals and other things in it that end up as aerosol.

People who live in places with hard water are familiar that there's often kind of a little trail of white powder near their humidifier, that's that same aerosol.

That got us really interested because we've all been in stores where it's clear that something is being emitted into the air.

So with a colleague, Mike Mack, who's in psychology, we did a study where we had about 60 test subjects and we exposed them either to very pure distilled water, so almost no particle generation, grape seed oil, to my nose unscented and lemon oil, which makes a very strong scent.

And we looked at the concentrations in the space, but what we were really interested in was the cognitive function.

And to make a lot of science and a very long story short, we found that exposure to the lemon essential oil made people behave more impulsive.

When there's a scent being emitted in a store, I think that part of the reason for that is to make people spend more money and it's taking advantage of the same thing.

- So some air cleaners might be attempting to intentionally produce, you know, very powerful oxidants like hydroxyl radical or hydrogen peroxide.

And when I see air cleaners that are claiming to produce these species, I like to ask myself, if these air cleaners are so powerful, do I want to exist in that space?

When that powerful chemistry is happening, those oxidation reactions can happen inside our bodies and contribute to inflammation and oxidative stress.

The converse of that is if it's completely safe and fine for you to be in the space, then what is the mechanism of action by which they're impacting the air quality in the space you're in?

So I think that's like a simple question that you should ask yourself if you're evaluating what kind of air cleaner you should buy for what kind of environment.

- Ionizers.

So I could talk all day about ionizers.

One of my first research projects was about ionizers and that led to years of legal trouble and other things.

It's quiet.

They're very low energy compared to something like a filter.

You don't have a filter that you have to replace.

The first problem is many of them are not that effective because they don't move that much air.

The second problem is some of the ways we generate ions also generate ozone.

And the third issue is that there are now two large, well done studies that show when people get exposed to ions, they have negative health outcomes, particularly cardiological health outcomes.

So ultraviolet lights again have been around for decades and they're used to sterilize.

Almost every modern hospital has a very extensive UV system.

With COVID especially, you can buy a UV system for your house.

UV light, if it's in the right wavelength range or the wrong wave light range will emit ozone.

And so you can have a UV light that's actually causing harm.

- The disinfection of air itself requires a much different design than a disinfection of a surface like a cooling coil in an HVAC system.

You need a smaller dose of ultraviolet light to deactivate a static surface that's not moving.

You can imagine if you have a lot of air moving through an HVAC system, you have a lot less time, so you need a much bigger dose.

And so in the past year there've been a couple of studies that have shown that there may be some downsides to that.

There are very few downsides to overdesigning filtration.

There's really not a risk of being like you filter the air too much.

So that's why you often hear indoor air quality scientists advocating for mechanical filtration.

It's a pretty safe way of improving the air quality in the space with very few downsides.

- Most recently we've been studying air fryers, a really popular household appliance.

There's very little known about what comes out of an air fryer.

The air fryer uses a very different technology from conventional cooking.

There's a very large fan blowing hot air through it.

And so we wonder if there's gonna be a different profile of different compounds that might come out.

And what we have found is that the air fryer does emit more than traditional cooking.

If you take the same recipe, if you do it either by a pan or by the air fryer, we compare those two and we found that air fryer generally emits more.

But one advantage of the air fryer is that you can cook with less oil.

And so if you scale back on the oil that you use, you can actually reduce what comes out of the air fryer.

We actually already have a solution.

We have kitchen hoods, we have fans.

If we can improve ventilation, we don't reduce the emission, but we can lower the concentration by bringing more of that pollutant outside and breathe less of that.

- It's doable, it's just understanding where to spend your money.

Ideally, I want to build a tight home, not just watertight, but airtight.

One that is well insulated, one that has a correctly sized HVAC system that can run long enough to dehumidify, a balanced ventilation system where it's not de-pressurizing or pressurizing the home.

But adding all of that equipment is, I mean, it's not just that the equipment costs money, but the labor costs money.

And oftentimes it will be crews that have never done this before.

And so that will even add more costs because they'll charge a little bit more and then maybe I'll have to fix something and have someone come back out.

So with that, it's not just money, but it also complicates the whole building process.

So these are the challenges.

- It seems like construction is a bit of a game of dominoes and you wanna make sure the dominoes aren't falling too fast.

- That's right.

(chuckles) - This is my first home purchase.

I've been wanting to buy for a long time, but it wasn't really till this year that things kind of worked out.

I was definitely looking for a home that had high performance, high energy efficiency, and my energy bill is actually cheaper than it was at my one bedroom apartment in Austin.

Initially when we had the inspection done, I couldn't tell that the air was even on 'cause it's so quiet and so subtle, but the house just stays perfect temperature.

Even when we had temperatures drop down into the 20s in February, the windows, there weren't even any coldness or air kind of seeping in through there.

I just kind of set it and forget it and I don't have to do anything.

It's great.

- The way that I became a builder was when we were living in this neighborhood, we had our first home built and we watched the process, but we also watched the process of other homes being built around us.

And not only did it look simple, but also we noticed a lot of, I guess, flaws.

And I kept wondering how am I noticing these flaws and these builders don't notice them and I'm not a builder.

I mean I have some construction experience but in other kinds of construction.

And so I just kept wondering, you know, why is this flashing not in front of the thing that it needs to protect or why are they making a hole here and it never gets sealed or protected?

And sure enough, these are real issues.

It just happens that not a lot of builders, at least in this area, are dealing with those issues.

A lot of these homes, they will look nice in the end and that's exactly why people don't know the difference.

- [Grace] Performance built homes and smart homes are not the same thing.

We're cautious about any smart home systems and here's why.

- The internet of things is, as it's often called, whether it be this simple webcam that I'm looking at that's connected to my computer or this shiny home that I'm in that has, yes ceiling fans that came enabled with a wifi connector in it.

They now have HD cameras built into the televisions.

Your fridge has operating systems on it that can be controlled.

What would happen if somebody was to gain access to your HVAC or to your vent hood over your cooktop or your oven?

Imagine coming home and finding that your home was just as hot as it was outside.

And no matter what you do, you can't unlock the new code that's been installed on the thermostat.

You can do all sorts of mischief with that or you could actually do some serious harm, especially when we control the electricity.

Which outlets will function?

Is there a healthcare device plugged into those outlets?

The smart door lock, the smart deadbolt or the garage door that can be cloud controlled.

When it comes to these cloud controlled devices, while there is security, they put a lot of that back onto the customer.

You will typically find within days of being made available to the public, a security professional like myself has published a blog detailing step by step how they were able to overcome that security.

And you can go online right now and find hundreds of thousands of open webcams both inside and outside of homes that are unsecured and publicly broadcasting to the internet.

The users did not set them up properly.

They can't send the device out secure, typically because the level of complexity that it would then take to set these devices up would negate the ease of use.

So users would stop using them.

they would need individuals like myself on call to go and do it.

Unfortunately, there's not that many of us to go around.

The cybersecurity industry currently has over one million open job spots.

When you start thinking about what could happen, obviously that becomes a problem.

Take time, think about it.

Read the book.

Complex passwords, multi-factor authentication, protect yourselves.

- Guys, I'm in Miami at this Natural Disasters conference and I want you guys to see what I see when I go through something like this, because the people who are trying to mitigate disasters are trying to do good things.

And of course the road to hell is paved with good intentions.

That is an example of engineering at work.

Engineering being a series of compromises because you can't have everything.

It is portable, it is weather resistant, shaped perfectly like a dome would be, but it's made out of fiberglass that's gonna be potentially sealed, like air sealed.

So it might be super airtight.

So you might have whatever you put in there, off gassing.

So now the air quality really suffers.

Humidity in there is gonna be kinda a nightmare.

You're gonna have the same problem that I had in my hotel room here, which is that it's gonna cool really easily, but it's not gonna dehumidify very well.

This is not to do with homes, but here's the Florida Keys.

And all of this is basically very shallow.

So what they're trying to do is just drop the temperature of this water going right through here from 90 degrees on the surface to 80 degrees, by going down to the cold water underneath it and bubbling that up here.

And they're using the fact that there is a velocity of the water that way to basically cool this water and then that cool water will carry through between the strait between Cuba and Florida.

Potentially you could use this anywhere, but I think that the idea of using the flow and the pressure and the temperature, it's the same thing that we're always dealing with in homes.

And basically what we do is of course weather systems inside of homes.

And by the way, this would cost to deploy this and change the temperature for four days.

You're saying it would cost 674 and a half million dollars and that includes all the cost of the diesel and the ship rental and all that stuff for an entire season.

But it would give you $16 returns in the disaster lessening for each dollar you spend.

Isn't that crazy?

Like the scale that we're thinking of when we talk about natural disasters is just, blows my mind.

One of the other things that makes me sad is thinking about the workforce.

I believe this is like eight feet by eight feet with an eight foot ceiling.

How are you getting the ventilation?

'Cause the little bunk is built into a little nook and they said, "Oh, we cut a hole in the top."

And I was like, "Okay, well how's the air getting back in to replace it?"

And they said, "Why are you asking so many questions?"

They're gonna have massive humidity problems.

This is not a good living situation.

Like you're putting people who are going to help people into living situations that are also potentially disaster prone, from a building science perspective.

So, here we are again, - In early 2000, you might remember that a lot of envelopes were sent that had anthrax spores in them.

The federal government, nobody knew how to deal with that issue.

How do you clean the building up?

Do you just tear the building down?

These giant, you know, almost million square foot buildings and set 'em on fire?

You know, what do you do?

So there was a lot of research that was done on what kinds of fumigants you could inject into buildings that would get into all the nooks and crannies of the buildings, that would get into the HVAC system, that would get into people's drawers in their desks, in their offices.

These things are still used in some places after hurricanes to fumigate homes and churches and schools to get rid of mold, right?

Same chemicals, same high levels as were used during the anthrax spores.

What do they do to indoor materials?

And we found that they do quite a bit.

So we found a lot of really interesting chemistry involving chemicals like chlorine dioxide, which is still used in the Gulf Coast after hurricanes to fumigate buildings.

And chlorine dioxide can engage in some chemistry that actually leads to corrosion of wiring, of copper wiring.

And it can generate some really interesting toxic byproducts.

So that was one of the many chemicals we studied with 24 different building materials that I think really opened people's eyes to the potential impacts of fumigating buildings to do good.

But at the same time, having this byproduct, which is maybe not good, - Finding crews to work with me was a challenge.

Initially I was on the quest to find people that care and I was convinced that that's the secret ingredient.

But that's hard to do.

No one's gonna care like I care.

But that's okay.

That's okay.

I'm looking for people that are willing to learn.

But the other thing I've learned is I need to listen to them as well.

Sometimes they have good ideas and I need to consider that.

Sometimes their ideas aren't that great, but they're just stuck on it and they don't want to change.

That's okay too.

I can adapt.

And so that's what I've been doing over the years is adapting what I've learned to what people are willing to do.

And it's become really a collaborative effort.

I had workers walking off jobs when I was being picky and I was pointing out every little detail to them.

Even on my own personal house, I had the framing crew tear down everything, pack up their tools right in the middle of it and take off.

I have to understand where to draw the line.

There are mistakes I see when I come to the job site.

I know I can point out maybe one fourth of them.

(laughs) If I point out too many things, it just becomes stressful for everybody.

In order to get those things fixed, I need to wait for the right moment.

- Many of us, and we know who we are, can't help trying to fix things.

It drives us.

- And that's what keeps the world moving forward.

But don't forget to carefully consider the byproducts you may also be buying when you bring home your new fix-it.

- All the science we're scouting this season can be practically applied to your specific home if you take the time to think through the factors and dynamics.

- All of which you can learn much more about at HomeDiagnosis.tv.

Stay with us.

(dramatic classical music) (classical music continues) (classical music continues) - [Kids] "Home Diagnosis" is made possible by support from Broan NuTone.

Better air.

Better life.

By the Got Mold?

test kit.

Real science, real simple.

By AirCycler, Retrotec, Rockwool and RenewAire.

By generous support from-