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Ep. 2: BBS - Radon Deep Dive · Bozeman Builders Science

• Ian White: Welcome back to the Bozeman Building Science Podcast. I'm your host, Ian, and today we're gonna talk about radon. Radon is one of those subjects where I think a lot of homeowners know just enough to know that they're supposed to care about it. It's a radioactive gas that comes from the ground and you test your home for it. But if the number comes back too high, somebody like me shows up, drills a hole through your concrete floor, sticks a piece of PVC pipe into it, and puts a fan on the other end. And somehow that's supposed to fix the radioactive gas problem. Which, when you actually stop and think about it, it is kind of a strange solution. Why would that work? Why is the radon getting into the home in the first place? Why can one house have almost no radon while another house right next door has a ton? And probably most importantly, why do we care about any of this in the first place? And that's what I want to work through today. Not just what radon is or what number you're supposed to remember. I want to get underneath the answer a little bit. Because once you understand where radon comes from, what it's actually doing to the body. How air and pressure move through a home and what a mitigation system is really changing underneath that house, the whole thing starts to make a lot more sense. And that's the goal. By the end of this episode, I want that pipe and fan to make sense, because it's just another system in your home. So let's start at the beginning. What is radon? Radon is a naturally occurring radioactive gas, and that sounds like one of those definitions that is technically correct, but it doesn't really tell you that much. So let's back up. Radon comes from uranium that exists naturally in rocks, soils, and sediments. Over a very, very long period of time, that uranium breaks down through a radioactive decay process. Eventually, That process produces radium, and radium produces radon. The really important difference here is that radon is a gas, meaning it's not necessarily stuck in the rock or soil where it originated. If conditions allow it, that gas can move. It moves through tiny spaces between soil particles, gravel, and cracks and fracture in rock. And Montana happens to have plenty of geology capable of producing elevated radon. I don't want to turn this into a geology podcast and start running through uranium deposits and different rock formations. The important part is that the raw ingredients are absolutely here. But this is where radon starts getting interesting. Because knowing that the ground around a home has the potential to produce radon does not tell us what the radon level is going to be inside of the house. Those are two very different questions. The geology gives us a source and potential. But we have to start looking at the soil immediately beneath the building, how easily gas can move through it, and how the building itself interacts with that soil. In other words, we have yet another system. Actually, we have several systems interacting with one another. And this is probably one of my favorite examples of why I don't like trying to predict what a house is doing from one isolated piece of information. We've tested two homes in Bozeman. That were about as good of an example of this as one could ask for. They were nearly identical spec homes, maybe 10, 12 feet apart, similar construction and crawl spaces, and both homes were vacant during the time of testing. They were tested about a week apart during the same general season under similar conditions. One home came back around two pico curries per liter, and the other more than 20, 10 times higher. Now looking at those two homes from the outside, there was nothing obvious that would have made you say, Well, of course, that one is gonna be ten times higher. They were just two different buildings sitting on two different pieces of ground. And even if the geology beneath them was very similar, the exact soil conditions, pathways, and the way the air was moving through each building all impact the final result. That's why I'm really careful when someone says, My neighbor tested low. That's useful information about your neighbor's house, but it is not a radon test for yours. And the same thing works in the other direction. If the house next door tests high, it does not automatically mean you will have a problem as well. It means radon is clearly present in the area and you have a very good reason to measure your own home. At some point we have to stop trying to predict the answer from the neighborhood, the foundation type. or how new the home is, we have to actually measure what this particular building is doing. But before we get into measurement, I think we need to answer a more important question first, which is why do we care? Because if radon was just another harmless gas moving through the soil underneath the home, none of the rest of this matters. The word radioactive tends to get people's attention pretty quickly. But I don't think that's enough of an explanation. I want to understand what the radiation is actually doing. When radon decays, it produces other radioactive materials that we usually refer to as radon decay products or radon progeny. And unlike radon gas itself, many of those decay products can attach themselves to tiny particles floating around in the air. things like dust, smoke, pet dander, all the little stuff that's already floating around your home that you're breathing every day. And when you breathe those particles in, some of those radioactive decay products can be deposited in the airways inside your lungs, where they continue to decay. When they do, they release something known as an alpha particular as an alpha particle. This is where I use an analogy that is definitely not a perfect description of nuclear physics, but I think it's a useful way of picturing what is happening. I think of an alpha particle like a tiny piece of subatomic shrapnel, And that alpha particle is moving at a speed very hard for us to comprehend, nearly 5% the speed of light. It doesn't travel very far, but if that radioactive decay happens next to the cells lining your lungs, it doesn't need to travel very far at all. It can dump a massive amount of energy into a very small area of tissue. One of the things that energy can damage is DNA. And that's the part that matters. I like to think of DNA as the blueprint your cells are working from. Your body is constantly replacing cells, copying instructions, and building new material from that blueprint. And your body is pretty good at dealing with damage. A damaged cell may repair itself. It might recognize that something is wrong and die. Your body has all kinds of quality control mechanisms. Constantly working in the background. So the idea is not that one alpha particle hits one cell and suddenly you have lung cancer. The concern is exposure over time. If you repeatedly damage enough copies of that blueprint over a long enough period, you increase the opportunity for a mistake to make it through the quality control system. The damage may get repaired incorrectly, or a mutation could survive when it normally wouldn't. Maybe a cell starts behaving in a way it shouldn't. We're just constantly adding opportunities for biological mistakes. And over enough exposure and time, that increases the risk for lung cancer. And that's really the health concern that we're talking about with residential radon. It's not an immediate poisoning. It's not something where you walk into a home with an elevated radon level and suddenly start feeling sick. We're talking about long-term risk, and that distinction matters. Because I don't want radon to scare people. I work with this stuff professionally, and I take it seriously. But taking something seriously and being afraid of it are two very different things. Now there is one comment I hear often that I think is worth addressing. radon mines. People go sit in radon mines because they think the radiation is good for them. And yes, there really are places where people intentionally expose themselves to radon as a form of alternative therapy. And there is actually a scientific idea behind at least part of that argument called radiation hormesis. And that doesn't just apply to radiation, but the basic hypothesis is that a very small dose of something harmful can sometimes trigger protective or adaptive responses in the body. Think of a cold plunge, for example. Extreme cold elicits a positive response in the body. If you were to remain in there for longer than necessary, you could be exposing yourself to hypothermic conditions for longer than the body is designed to handle. Now this isn't a concept somebody invented specifically to defend, right on mines. Hermesis is a very real area of scientific discussion. There are researchers who've argued that very low doses of ionizing radiation may stimulate repair or protective mechanisms, and radon therapy has been studied in that context. But here's the distinction that I think matters. The existence of that hypothesis does not mean we should jump from low dose radiation may produce certain adaptive biological responses to therefore chronic radon exposure in my home. Is not a lung cancer risk. They are not the same claim. The public health guidance we use for residential radon still treats exposure as a lung cancer risk, and the recommendation is to reduce unnecessary exposure rather than intentionally maintain an elevated concentration in your home. So if you've heard about the radon mines or caves, You're not imagining it. There is a real idea behind that conversation. It just doesn't make the residential radon question disappear. Now that we understand why radon matters, let's come back to the home. We've established something important. There can be radon in the ground, and there is a legitimate health reason to reduce our exposure to it. But there's a missing step. How does radioactive gas from the soil? underneath our building actually make its way into the air we're breathing inside the home. Let's forget radon for a minute and think about air. Your home is constantly moving air. Warm air rises. Bath fans and dryers move air outside, and anytime air leaves the home, that air has to be replaced. The house does not really care where that replacement air comes from. It may come through small leaks in the building envelope, might come through an open door or a window, or mechanical ventilation. Some of it might come from underneath the home. And this is where pressure becomes really important. Air moves because of pressure differences. If one area is at a slightly higher pressure and another is slightly lower, air tends to move toward the low pressure area. You do not need a huge pressure difference for this to matter. We're talking about very small pressure differences that are happening continuously inside all buildings. And in a lot of homes, especially during colder weather, the lowest portions of the home can operate at a slightly lower pressure than the soil beneath or around the foundation. Think about what happens in the winter. We heat the air inside of our home, and that warm air becomes more buoyant and rises. Some of it leaves through the upper portions of the building. And as that air leaves, replacement air has to come from somewhere lower. That's known as stack effect. During a Montana winter, when it's warm inside and very cold outside, that temperature difference can make stack effect even stronger. So now the lower part of the home may be sitting at a slightly lower pressure relative to the soil beneath and around it. And if there's a pathway connecting the two, soil gas can move inward. If that soil gas contains radon, the radon comes with it. So do not really like saying that radon finds cracks in your foundation. Radon isn't necessarily looking for anything. That crack is just a pathway. And the pressure difference is what's actually doing the work. It doesn't matter the pathway, the underlying idea is the same. We have soil gas on one side and indoor air on the other, and if we have a pressure difference encouraging air to move between the two, we have soil gas entry, and that's the system. This is also why radon cannot really be understood in isolation from the rest of the home. The radon system is interacting with a building that already has other systems moving air and changing pressure. A dryer, fireplace, they change the pressure. And no one of those things automatically creates a radon problem, but they're all part of the environment that a radon system has to operate inside. We cannot pretend that a radon mitigation system exists in its own little bubble. It is part of the building. The mitigation system is one participant in a much larger pressure system. And this is probably one of the biggest ideas I want you to keep in mind through the rest of this episode. Radon is not just a radioactive gas problem. It's a building interaction problem. The ground provides the radon, the building provides the pathway and the pressure difference. That pressure difference determines whether soil gas moves inward. And once you look at it that way, a lot of the common questions about radon get much easier to understand. I don't have a basement. So do I really need to worry about radon? And it's a completely reasonable question. Radon does not require a basement. If you don't have a basement and instead have a concrete slab underneath your home, you still have concrete separating the living space from the soil beneath the building, but there can still be cracks, plumbing penetrations, and joints around that slab. It's the same idea. Soil gas on one side and indoor air on the other. If a pathway and pressure differential exist between the two, radon can enter. A crawlspace changes the picture again. Now we may not even have a concrete slab separating the home from the soil. If the crawlspace ground is exposed, or there's simply a loose plastic liner that's not sealed as an air barrier, radon can move out of the soil and into the crawlspace air. From there, that air can further communicate. into the rest of the home above it. It's a different foundation, but it's the same underlying system. And it's an important distinction. The foundation type helps determine a lot about how one might investigate a radon problem, and it tells us a lot about what a mitigation system might eventually look like. But it doesn't tell us whether the home has elevated radon. And the same thing is true for the age of the home. A brand new home can have elevated radon levels, just like an old one. A house can have a passive radon pipe installed during new construction and still need to be tested. None of those details ever gives us the final answer. They give us information about the building. Which brings us back to something we touched on earlier with those two neighboring homes. At some point we have to stop predicting, and we have to measure. So what does a radon test actually tell us? A radon test is taking all of the previously discussed interacting variables, like the geology, the building, the pathways, and how the air is moving, and gives us a number that represents the radon concentration in the air during that test. And for most homeowners, the number they're familiar with is four. But I want to be careful with the way we think about that number. Four is not a magic line where three point nine is completely safe and four point zudly becomes dangerous. Radon risk does not work like a light switch. It exists along a continuum. The EPA recommends taking action at four picocuries per liter or higher, but it also recommends considering mitigation between two and four. So think of four as a decision point and not a biological cliff. And another thing that matters here is that radon moves. The number in your home is not necessarily identical every hour of every day. The weather, pressure, and the way we operate the home changes those levels. So if you have a continuous radar monitor in your home and see one ugly hourly spike, it does not automatically mean something has failed. The context, duration, and average matters. And this is where testing can get much deeper than we should probably go. standards around where we place a device, how long we test, and what conditions need to be maintained during certain types of measurements. I am certified through the NRPP as both a radon measurement professional and a mitigation specialist, and part of the value of that training is learning how to collect information in a standardized, repeatable way, rather than just putting a radon monitor somewhere and assuming the result means what we think it means. The important point is much simpler. We cannot look at a house and know its radon level. You can't use your neighbor's result or your foundation type. You have to measure. Once we have that measurement, we can finally come back to the question we started with. How does drilling a hole in the floor, attaching a piece of pipe, and putting a fan on the other end of it actually change any of this? So, how does a radon mitigation system actually work? Because this is where everything we've talked about starts coming together. We have radon underneath and around the home, we have potential pathways between the soil and the indoor air, and the house can create a pressure differential that encourages soil gas to move inward. So what if instead of just trying to seal every possible pathway and hoping we were able to find all of them or get to them? we deliberately changed the pressure relationship between the building and the soil around it. And that's the idea behind a radon mitigation system. In a concrete setting, we create a suction point underneath the slab. We connect that suction point to piping and then use a fan to create negative pressure underneath the building. Essentially a glorified shop vac. But this is where the wording matters. We're not trying to vacuum radon out of your living room. We're trying to intercept the soil gas before it becomes indoor air. The house may already be creating a slight pressure difference that encourages soil gas to move inward and upward. What we're trying to do with the mitigation system is create a larger pressure differential under the slab than the home is creating above it. The house is influencing the soil gas in one direction. We want the mitigation system to create a stronger influence in the other. Once that clicks, the pipe and fan suddenly stop looking so strange. We're just manipulating pressure, and we're giving soil gas an easier path. We're exhausting it outside before it becomes part of the air you're breathing, and that's the basic system. A crawl space is not much different. Instead of a slab, we deploy a piece of plastic known as a vapor barrier. The perimeter edges are sealed and each section of liner is depressurized, again pulling that radon gas out and up before it ever has a chance to enter the home. And that's the basic system. But basic does not mean identical. And this is where actual buildings start making things interesting. Each radon system needs to be custom tailored for the building that it is in. I'll give you a really simple example. We had a basement with one central footing running lengthwise through the middle of it. We installed a suction point on one side, and on that side, we were able to create the pressure difference we needed underneath the slab. but that pressure field. was unable to reach the other side of the basement. And when you stop and think about the construction, it makes perfect sense. There was a continuous concrete footer running down the middle of the slab. And that footing was acting as a boundary. We had created the pressure relationship we wanted on one side, but were unable to reach the other. By adding another suction point to the other side of the footing, it solved the problem beautifully. Same house, same mitigation fan and same basic principle, but the physical construction of the building changed the way the system had to be designed. And that's why I like the phrase custom tailored when we talk about a radon mitigation system. The physics are the same, but the home is the variable. One house may have a single slab, and another multiple foundations or even crawl spaces connected to the basement. I don't want to go too far into the diagnostic side of this, because we could spend an entire episode talking about how we determine whether pressure is actually extending beneath different areas of the building. You don't need to become a radon mitigator to understand your home. I want you to understand why the individual building matters. You can't just pull a generic radon system off the shelf, bolt it onto every home, and assume the outcome will be the same. The system has to interact with the building that is actually there. And that brings us right back to the bigger idea. Your home is a system, and the radon mitigation system is just another smaller system within that home. Now once people understand that radon enters through pathways, the next question is usually pretty logical. Why don't we just seal all the pathways, all the cracks and plumbing penetrations? And sealing absolutely has a role. If we have a giant open pathway between the soil and the home, closing that pathway can really help. It can also help a mitigation system create a meaningful pressure field underneath the slab. But sealing alone is rarely the whole answer. A foundation is not an airtight bowl. Concrete cracks and penetrations exist. And there are plenty of other pathways that may be difficult or impossible to access. More importantly, if the pressure difference that was encouraging soil gas into the building still exists, simply sealing one visible crack does not necessarily solve the system. The air may find another pathway. That's why I tend to think of sealing as a supporting pressure strategy. And not a replacement. We're not just chasing cracks around the basement with a tube of sealant, we're trying to change how soil gas moves around the building. Now, this is where I want to come back to something we touched on earlier. A radon mitigation system does not get to operate in a vacuum. We are deliberately changing the pressure underneath a building. That building already has systems that move air. It may have combustion appliances, mechanical ventilation, or a fireplace. those can all influence radon. A mitigation system has to be installed in a way that respects the rest of the building. A natural draft water heater is a good example. Those appliances rely on buoyancy and pressure to move combustion gas up the flue. If you create the wrong pressure conditions around that appliance, you can interfere with the way it drafts. Now that doesn't mean radon mitigation and natural draft appliances cannot coexist. They absolutely can. It means the person working on one building system needs to understand that other systems exist This is why I'm so fascinated by building science. You can pull on one thread and pretty quickly discover that it's tied to three other things. there are some rabbit holes in here that I absolutely want to go down. Radiant slabs are one of them. How does heating the slab itself change the behavior of the air and soil underneath the building? How might that affect radon movement? I have questions. But that's not the rabbit hole we're going down today. The point is simply that the systems in a home do not exist independently, and if we change one, we need to understand what else may be affected. So after installation, how do we know the system actually works? Let's say we've tested the home, looked at how the building is constructed, and we've installed the mitigation system. The fan is running, we've got suction, and everything looks as it should. But does that mean the radon levels are going to be low? Not at all. And I think this is a really important way to close the loop. We test again. Because the whole point of this process is not to install equipment. The point is to reduce the radon concentration inside the building. Before mitigation, the test tells us what is this combination of geology, soil, building, weather, and pressure producing inside the home? And then we change the system. And afterward, another test tells us did the change actually produce the outcome we wanted? And that's the important part. Did we actually lower the radon? Because if we didn't, then there is still something about the system that we do not understand, and we need to keep working the problem. So let's come back to where we started. You've got a naturally occurring radioactive gas coming out of the soil underneath a home. On the surface, the solution is a piece of PVC and a fan. That sounds almost ridiculously simple, but now we can see everything underneath it. The geology creates the radon, and the soil allows that gas to move. The building creates pathways and pressure differentials. We measure the result of all those things interacting. And if that radon level is elevated, we deliberately change part of that pressure system so the soil gas has an easier path outdoors than it has into the home. And then we test again. And suddenly the mitigation system isn't magic. It's just building science. That to me is the part worth understanding. If all I ever tell you is radon is bad, test your home. If it's I install a mitigation system, you can memorize that and repeat it, but you still don't really know why any of this works. Once you understand the system underneath the answer, you don't have to memorize it, and it starts to make sense. And hopefully the pipe and fan makes sense too. That's all I got for this one. Thanks for tuning in, and we'll catch you on the next one.