Robin Jade Conde

PODCAST: Where to find mold, Part 1

Minnesota is a moldy state and there are around 59 places where mold can hide! Today, Vickie Swenson from Minnesota Mold Inspections, LCC and Neil Saltzman from Inspection Services, help us unpack some questions about mold. 

They talk about how to find mold, how it develops, and how to prevent it. Vicky mentions that molds usually grow within 72 hours. Then she discusses the standards in inspecting and testing it. She highlights that the most common places where mold can hide is behind the bathtub, rim joist installations, and basement carpet.

Reuben also shares why he thinks warm water may develop mold faster. Tessa shares that molds can be present in both old and newly constructed houses. Bill asks about surface molds. They also discuss other kinds of molds and how much they can grow.

Neil highlights that humidity plays a big role in the development of molds. Vicky mentions the allergic reactions she’s developed due to exposure to molds.

The following is a transcription from an audio recording. Although the transcription is largely accurate, in some cases it may be slightly incomplete or contain minor inaccuracies due to inaudible passages or transcription errors.


Bill Oelrich: We’re gonna begin to unpack mold in all the fun places that it can hide.




BO: Welcome everyone, you’re listening to Structure Talk, a Structure Tech presentation. My name is Bill Oelrich, alongside Tessa Murry and Reuben Saltzman, as always, your three-legged stool, coming to you from the Northland, talking all things houses, home inspections, anything else that’s rattling around in our brain. Today, the thing that’s rattling around in our brain is mold. So we’ve got Vickie Swenson back from Minnesota Mold Inspections, and we’ve got our own Neil Saltzman, the newest mold inspector on the inspection services team here, and we’re gonna unpack some questions about mold. In fact, we’re gonna put a puzzle together that’s got… How many pieces Vickie? 59? 


Vickie Swenson: Yep. About 59 places where mold can hide.


BO: Exactly.


Reuben Saltzman: That’s all.


BO: We’re gonna begin to unpack mold in all the fun places that it can hide and just dig into Vickie’s brain. She’s got a tremendous amount of experience in this arena. And people love to learn about mold, and we’ve been in this business a long time, and I feel like I know just a minute amount about mold. So Tessa, Reuben, if you were to rate your mold knowledge on a scale of 1 to 10, where do you put yourself at? 


RS: I give myself a two or a three, pretty low.


Tessa Murry: Yeah, I’d say the same thing to identify something that looks like it could be mold, and we try to figure out the source of it and give some recommendations for people on ways to try and prevent it from growing back, but that’s about it.


BO: And everybody wants to know, how bad is this? Should I be concerned about this? And of course, we don’t really have any answers, because what you see on the surface could be just the start, could be the tip of the iceberg, or it could just be a little something that’s nothing to be concerned about. Vickie, where do you begin when you’re thinking about out mold and evaluating the house, and when somebody asks you, How big of a deal is this? What’s your standard answer? 


VS: Well, I think Tess hit it on the head, you wanna find it, figure out how it got there and prevent it, those are really the three big questions. When it comes to medical… When people are asking medical questions, I make it very clear, I’m a home inspector too, I’m like you guys, I’m not a doctor, I’m not a lawyer, I stay in my lane. What I do is answer the questions, Do you have mold? What kind? How much? How did it get there? How do you get rid of it? And is it gone? It sounds really straightforward answering those questions, it’s not… It’s very complicated because houses and people are complicated, people getting sick, people’s doctors diagnose them, it’s a very bigger question, but I try to keep with those simple answers and bring it down to that level of simpleness, simplicity.


BO: How many houses are you in, in a given year looking at mold? 


VS: Well, we just had a record week a couple of weeks ago, 29 in one week. So probably the average is about 15 per week, 15 to 20, so it’s a lot, we’re hitting well over 7000.


BO: And we’re almost 22 months into this pandemic. Have you seen a spike in business as a result because people are at home so much more than they used to be? 


VS: Yes and no. Minnesota is a very moldy State, it’s always gonna be here. Early during the pandemic, we were slow because people were just afraid to have anyone yet, but I always say we were lucky enough that enough people had us and that we could keep going. So I started wearing a mask for the pandemic, never have worn it for mold, but I do wear it now quite a bit just for the COVID reasons, that’s been interesting ’cause I’ve developed some allergic reactions to mold and I still have them with a mask on. No, I’m not wearing an N95, I’m wearing a paper mask, but that’s been an interesting observation.


BO: And we’ve talked about your sensitivity to mold in the past, and it’s like you don’t even need to send the samples in, you can basically tell somebody, You have any number of different molds based on your nose.


VS: It’s fascinating because I have developed four different allergic reactions, the most common one is my tongue swells a bit, when it’s heavy and carpet, my nose will run, when it’s wet on sheetrock it’ll go to my throat. And when there’s one called Chaetomium it makes my skin itch a little bit and it’s… I can’t use that in the reports because it’s all anecdotal, but it’s pretty reliable and then I can see like… Yep, that’s what I thought, because that’s how I felt.


TM: That’s amazing.


RS: That’s awesome.


BO: Neil, have you developed any allergic reactions to mold now that you’re in the mold testing business? 


Neil Saltzman: Not like Vickie has. No.


VS: It took five years. And then as time… I’ve been doing this, going on 17 years, so just from continued exposure, so people that live with it… Mold is an allergen, you can get inflamed muscles, joints, head, brain, so I think that’s… I stay out of the medical diagnostic part of it, but I tell people, I did get into this because one of our sons is allergic and he has asthma and his asthma would just fly off the charts when he was near mold, so I do recognize that it can make people sick, again, their doctors have to answer those questions once they know what kind of mold they have.


BO: Gotcha, perfect. Well, we talked about a puzzle and you came up with this beautiful list and there’s 59 different… How would you define it at places where mold can grow or places where you find mold, like how did… How and why did you begin creating this list? 


VS: Because I tell people I’ve never met, clean houses I’ve never seen. They’ll call and they say they have this in their insulation, I send them a document, they say they have a spot on their sheetrock, I will walk them over the phone what to do, where to rent the tools. So every house is really kind of the same, so eventually when I heard that Neil was really getting more into mold, I proposed to Reuben, let’s do a podcast together, and I literally thought, this is the 17 places where mold hides. And then when I sat down to write the list, I’m like, Woah, it’s way more than 17, because it really is the same. Houses are houses, and it does happen to be… Rarely do I see something unique that I haven’t seen before, but that does happen and that’s really interesting, like, Whoa, I didn’t know that could happen. There was a condo, three-year-old condo in Wayzata, something happened to their shower control, so it didn’t flood the condo, it just ran hot water into the drain for two weeks, because it’s a condo hot water never runs out.


VS: So if you run a shower for two weeks, you will grow the most interesting mold, you will warp your your wood work, you will ruin everything in that room because it went in the drain it didn’t flood. It was all humidity, but it was probably the biggest indoor source of humidity. So I’m like I didn’t know that could happen. Or an old building and Carver that has this white Fungus hanging down that looks like something scary. That’s really just Aspergillus penicillium, but because of the moisture conditions it’s grown for 30 years into like seven inch fungus weird stuff.


RS: Fingers.


TM: The legs…


VS: Yes, try to picture like… Yes. Like slang tight. So I’ll send you those pictures later. So occasionally I see something I haven’t seen before, but 99% of the time every house is the same.


BO: Reuben you’ve lived in quite a few houses over the years. Have you ever run into a mold problem in any of the houses you’ve lived in? 


RS: My own house no, no, I can’t say I have. I am very heavy on the dry atmosphere in my house, we use lotion on our skin in the winter time and we keep our humidity somewhere close to around 20%. So I don’t think I’ve ever had a mold issue crop up. I don’t know, I should ask my pops, maybe he’d have a better memory of my houses than I would. You remember anything I’ve had? 


NS: Well I found it in your bedroom when I tore it apart and remodeled it last winter.


RS: The house I grew up in? 


NS: Yes exactly.


RS: Your house? 


NS: So there’s where your allergy started son.


RS: That’s where it came from.


NS: That’s where it came from. But really it had to be a water leak issue, and there was, and it got resolved. But yet there were some residual black staining on the framing when I took off the dry wall I found it.


TM: Was that wall below grade? 


NS: Yes.


TM: Okay, I’m sure that’s gonna be one of your locations Vickie, that you’re gonna list here coming out, right? 


VS: Yes.


NS: The low grades and surfaces.


VS: Because over half the mold is below grade. Yes.


BO: Where is the one spot you walk into the house every time and you say it’s gonna be there, if it’s gonna be there.


VS: I thought I should have rated the top five. What I started on a list is a plumbing access panel, and that’s because if you get a shower leak or bathtub leak there’s hopefully a nice little box you can open there and see, and if it’s leaked that’s what I put on there first is plumbing access you should always check that out.


RS: So you’re talking about the access panel behind your bath tub so you can get at the drain, and you’re saying you open up that access panel, and a lot of the time you’ll find mold from a concealed leak behind the tub right? 


VS: Exactly, especially in older homes… Well not even in older homes, there was a two-year-old condo… This is kind of a side note but the PEX plumbing, there seemed to be a lot of failures with the PEX plumbing connections. So a lot of these plumbers and these new constructions are having plumbing failures in brand new houses. And so this one in Minnetrista was growing mushrooms in the closet, but they didn’t notice it until they moved out, so now a new owner moved in and saw the mushrooms, so now is this the builders fault? The plumbers fault? The seller’s fault? It got really complicated, but the builder stood up and took care of it because it wasn’t… It happened during construction and just left there for two years. It was slow enough where it didn’t flood, but it caused a really big mold problem.


BO: Is that something that just… The fitting was loose or, it was drip drip or…


VS: Yeah, I don’t know what it is, ’cause I’m not a plumber, but there was a house in Edina, where by the time I had gotten there that was their fourth plumbing leak in their brand new house. So I think it’s because PEX is a plastic tube where the old water tubes were copper and soldered. PEX is now a plastic tube that’s hooked to your plumbing, and I just don’t think the connections are always made that securely. So when a plumbing access for your bathtub or shower, when you see mold, ’cause I’m dealing with one of these right now, like how far back does it go under the tub? You can’t see under the tub that well to know if you have to take the tub out or you can just clean that mold from using the plumbing access.


RS: And how critical would it be? Now let’s say there’s some mold and it looks like it’s going underneath the tub. How critical do you think it’d be to get at all of it? 


VS: Depends if the person’s getting sick or not. I’m of the opinion if you find mold, you wanna get it out of your house and the State Department of Health agrees with that, so I am a remove it if you find it person.


RS: Okay, alright, thank you.


VS: So the next sub-floor around toilet from wax ring leaks. So do you guys find a lot of wax ring leaks? That toilet I think people think, how is that gonna leak? I don’t even know if that’s clean water coming out of there or sewer water.


RS: Yeah, it’d be both. It’s typically gonna be sewer water, you flush your toilet, and it’s a stuff going down the toilet that’s gonna leak out, and we find a ton of those, and we use moisture meters around toilets, we use scanning moisture meters. Our protocol for home inspections is we scan the floors around every one to check for elevated moisture content in the wood below the floor covering, and we find a lot of them, that’s a good one.


VS: Yep, super common and sometimes when you take the vinyl or the whatever, I don’t like to see laminate in bathrooms, but sometimes you can see it under the vinyl, but when you take it out sometimes it’s just like an inch around the toilet, sometimes it’s spread out like three feet, so super common place to find mold.


TM: Is that a place Vickie, that’s pretty easy to remediate it? I guess it’s a softer surface, the wood sub-floor. Can you just clean it with something? Or you have to cut out the wood typically in the situations you’re seeing and replace the wood? 


VS: That’s a good question ’cause it just depends how long it’s gone on. In general wood can be cleaned if it’s not rotten, so if it’s rotten you cut it out, if it’s still viable then you clean it with a four-step process, which is Hepa vacuum, treating as much as you can, then use a product similar to concrobium mold control, not bleach, and then you seal it with an new cap sealant. But yeah, I’ve seen them rotten where you gotta cut ’em out.


BO: Just kind of touching on these, you have these events in your house, you spill some water, or maybe you have this leak going on around your wax ring or this drip from a faucet that nobody really taught. Does everything always have to be… As you just said, wood doesn’t always have to be replaced, but it feels like when something’s wet for a period of time, it’s gotta be fixed, it’s gotta be pulled out, or do you have a timeline where if it’s been wet for more than two weeks… Is there some line in the sand where this material comes up no matter what? 


VS: You’re kind of referring to something, the IICRC is a group that the inspection, Institute of Inspection Restoration and Cleaning, they write standards for structural drying and mold removal, so the S-520 as the standard that most people follow for mold removal. When it comes to drying… Let’s say they get there and someone’s dishwasher sprung a leak, and their sheetrock’s been wet for a week because they were on vacation, that standard says that if something’s been wet over 72 hours it should become coming out. So technically, you’re right, a toilet leak that’s gone on for two years, probably should, but if it’s they can dry it normally they’re gonna sand it and clean it instead of remove it.


BO: Okay, and there’s no jurisdiction that says this has to be done per se, there’s just really set guidelines.


VS: Correct, and it’s all voluntary guidelines, but most of the good mold companies are operating under that IICRC S-520 guidelines. I always say there’s three levels of workers in the mold business, there’s the handy man, they just take out the moldy sheetrock put up new and they’re done… Or take out the carpet and put up new and they’re done. The good mold guys are all gonna follow that standard, but then there are… Apparently, there’s a standard that’s even stricter than that, the restoration industry association, because when my colleagues tells me that when you have mold on a wall, the S-520 says that you should remove sheetrock for two feet beyond visible mold. He says that stack up that pulls up those spores up on the wall and you have to take off the whole wall to do a good job, so that’s even higher, there are people operating at an even higher standard than the S-520, but most people are gonna do a good job using the S-520.


BO: Very good, thank you.


VS: Yep, framing studs. Like a lot of times, I think when I started writing this list and when I go into a home, for some reason, everybody thinks mold is just gonna be… They’ll be able to see it on the sheetrock, people always say, Well, I don’t have a mold because they think they’re gonna see black mold on a white sheetrock, and that is the case, and a lot of these I will talk about, but they don’t consider that it’s in their carpet or their attic or their insulation, for some reason, they’re just… Because they’ve probably seen it on walls, that’s where they think they’re gonna see it. But if you have framing studs behind sheetrock that have been wet from plumbing leaks, ice dams, washing machine overflows, it’s probably gonna be on the framing studs behind the sheetrock too, so that’s one reason you have to take that sheetrock off and this probably come up a couple of times, but when sheetrock’s been wet, you do have to take it off because it could be on the other side of the sheetrock, it could be on the framing studs.


TM: I wonder how many houses have that issue with mold growing on the studs just from the initial construction phase. You know with all the moisture and you know being exposed to the elements and all of that, and if a house is built very quickly and there was a lot of rain, like how many houses have that issue that never had a plumbing leak before? 


VS: A lot. A lot. It depends who your builder is, so my husband and I worked on one very reputable builder last year, they poured the foundation the skint slab in the winter, it caused so much humidity that every trust grew mold. So I was working for a different cement guy at the time, and I said, Well, how would you avoid that? He said, don’t pour your slab in the winter. So that’s one. They had to sand it off every single trust during construction. Some of these big builders, they’re in a hurry, so they don’t take time, it’s so easy to watch that wood when you’re building… I tell people, if you’re gonna build a house go there every single day, get your own moisture meter, look at the wood, if it’s changing color sand it off, it’s such a simple thing, but a lot of builders don’t take time to do that, and I’ve had… Well, we have someone buy a multi-million dollar house, they just left framing studs in the utility room, you could see it on there, but the worst thing is they had this utility panel with all these hoses and wires, they took a moldy piece of OSB put it in here and put all these wires and I could swab it right there, I’m like wouldn’t you at least take a new piece of OSB, this house is $2.7 million and you’re putting this moldy OSB. So it happens all the time, this is a really good point test.


TM: Yeah, I think a lot of people that are buying houses, or at least my experience with clients is if they’ve had a problem with mold in an older house before they automatically think that buying a new house, they won’t have those issues, you won’t find mold in a newer construction house. And if you do find mold that’s like… Is very unexpected. People are shocked by that.


VS: I think they say that between the framing studs, the cement, the sheetrock, I don’t know, there’s like a 100,000 gallons of moisture in a new house, it takes a couple of years to dryout, and so you have to leave all your doors open, I’ve had people by a new house, and leave their doors closed because they’re not using those rooms and they grow mold and… Yeah, I know that it happens on the framing studs from the rain. There was an apartment building down in Bloomington a couple of years ago, and the city made him have a mold inspection because they left it open so long, and I walked through for two days and just identified all the mold, and a mold company went in, they had to pay $20,000 to get all that mold taken, but if the city hadn’t made him go in, they just would build around it.


BO: What’s your definition of leaving it open, were the window is not installed and the building paper wasn’t on and the roof wasn’t on, or what…


VS: Yeah, well, this, I think just because it was a big apartment building and they didn’t get the… I’m guessing, they didn’t get the real sheathing in on time, but I have a client right now being… He’s building a new house that he wants to back out because apparently his builder has the trim on the sheetrock up, but there are still doors that are missing, exterior doors, he’s really concerned, so I don’t get as involved in as much of new construction. We built our house 17 years ago, we were here every day, if it rained, I took a squeegee and took the water off my sub-floors. We did all our own construction backing. We were here, my uncle built it, so we were here every day taking care of that stuff, and we had really good air quality.


BO: Interesting that, I don’t think a builder would have the manpower to do that, that’s a whole another team of people coming in at night.


VS: But they should at least watch the color of the wood, mold is a visual thing at that point. If your wood is turning color it’s probably mold sanded off. So to me, it would be a very easy thing, but they tell me these builders are under these strict timeline, so they don’t take the time. For a while when I first entered the business, there was a move towards encapsulate and treating the word, so you go by and you see this house, it was all painted blue with this anti-microbial coating, but I don’t see that happening anymore.


BO: Reuben, Tess, do you remember when we had the conversation with the architect and builder from Golden Valley, who talked about running the de-humidifiers for, what, was it two weeks or something like that, to try to dry out the wood after these houses are…


RS: Yeah, that was Rob Vassallo, he was a huge proponent of that, he said “That’s the only way you should ever build the house.”


VS: Yeah, I agree. I agree, but he said for two weeks, I’m sure they could do other things in those two weeks, but just so many builders don’t do that.


TM: It’s like out of sight, out of mind, right? If we put sheetrock over it, who’s gonna see it? 


VS: Yes. That’s exactly right.


BO: Well, mother nature sometimes cooperates better than others. I think, the summer of 2021 was a pretty good year for building. It was pretty dry.


VS: Yeah, yes.


BO: We didn’t get a ton of storms, so.


VS: Yep.


BO: Tessa, I gotta come back to you on this because you’re our wood expert. Could you tell me from an absorption perspective, young pine in the material we’re using to build houses now compared to old growth fur. One is a sponge compared to the other one, that’s like a rock, right? 


TM: Yeah. Well, thank you, Bill. I wouldn’t consider myself a wood expert. There are so many more people [chuckle] better qualified than I am.


BO: Well, you had a class that was about woods, specifically, right? 


TM: Yes, I did. I did take quite a few classes about just wood, but. Yeah, I think the main thing to note… And we’ve talked about this in previous podcasts, it’s just the difference between like, old growth lumber that was used in these older houses… We’re talking like 1900, 1920s, even in the 40s, versus the materials we use in more modern houses, like OSB and fiberboard and chipboard and, you know, wood that’s grown very quickly and harvested to create these products. It’s gonna have a lot less heartwood, which is naturally more durable. So that type of product just doesn’t have the durability that the older wood had. And so when it gets wet, if it can’t dry, you’re dealing with mold and moisture issues and rot a lot faster.


BO: Vickie, when you’re in houses and you see water leaks, is warm water, will that tend to grow more mold than cold water? Or does it not make a difference? 


VS: I have never been asked that question. And that probably would be a microbiology question, and again, to make it clear, not a doctor, not a lawyer, not a microbiologist. I’m a home inspector, but that is an interesting question.


BO: Reuben, what do you think? If you’re making a wager.


RS: If I had to make a wager, I’d say the warm water. Why? I don’t know, I think you need a few things for mold growth. You need to have the right temperature and you need the water and you need a food source. And I’d say you start with a warm temperature, you’re that much closer to having mold in a finely calibrated environment. But I think in reality, it’s not gonna make much of a difference. We’re talking, like, hours difference for…


VS: Yes. [chuckle]


RS: The time it takes for that water to cool down, so…


VS: I love that…


RS: Not much…


BO: Interesting.


RS: Difference is my guess.


BO: I’m sure there’s really smart people and microbiologists out there can help us with this, so please feel free to correct us. Even like, how much water is in a house that needs to be pulled out. Vickie, you said a pretty big number and I won’t dispute that.


VS: Yeah. I am not an expert on that, yeah, but that’s what…


BO: Yeah.


VS: I’ve been led to believe, it’s a lot of water. But I was at a mold class once where the instructor said they were in a crawl space and they could see the mold growing at an inch per hour, so Reuben is right, when the right conditions are right, it grows.


TM: Aw.


VS: And it can grow in 24 to 48 hours, but they were watching it grow.


RS: Hold on. I gotta underscore what you just said, “an inch per hour.”


VS: Yeah.


TM: What? [laughter]


VS: They could see it, forming.


RS: Now, see, that’s just wild. And so often we’ll get these reports about, We found mold here, we found mold there, and it’s like, it doesn’t look that bad, but obviously there’s mold. And then you’ll get this “expert,” I’m doing air quotes here. It’s good pod to have air quotes. You get this “expert” who comes in. It’s a handy man. And they will diagnose this mold as having been there for X number of months, and say, “There’s no way this just showed up over a couple of weeks. This has been here for a long time.” And your home inspector obviously missed it. This was definitely here when you had your home inspection three months ago. [chuckle] And I just wonder how can you possibly know that? And…


VS: You can’t. You can’t. Every insurance adjuster… Because what happens… A basement floods, the drying guys go in and they find mold. And the classic question is, Was this mold from this water last or here before? And so, if you could take a mold test and age it, everybody would love that, but it doesn’t work that way. You can’t age mold tests.


RS: Sure. Thank you.


VS: Sometimes, Reuben, when they’re seeing that… ’cause I’m working on one right now. The women bought the house, and all of a sudden there’s mold everywhere. My conclusion is the guy cleaned it with bleach. It looked good for about a month and now it’s coming back.


RS: And that’ll happen, huh? 


VS: Oh, yeah. Bleaches that makes it look like it’s gone, but it doesn’t stay on the surface long enough to kill those little ruts, so it’ll come right back.


RS: Okay.


BO: It’s your guess on something like that, Vickie, that they didn’t get the wood dry enough? 


VS: Oh, this is on her sheetrock.


BO: Oh, okay.


VS: On her sheetrock on her baseboards.


BO: Okay.


VS: And so, what I do when I see mold near the bottom of the wall on the sheetrock or baseboards, I lift the carpet to see if there’s… If you see darkness, water stains under the carpet, then there’s some sort of leak. But if it looks perfect under that carpet and it’s just on the wall, that’s humidity. And it was showing up everywhere, so I’m like, “Do you think this seller was growing plants in here?” Because that’s another thing that causes mold, when people have their indoor farms. And she said she did find some mushrooms growing. So he might have had a little farm going in there. I’m convinced with the mold showing up everywhere that he just wiped it off with bleach, ’cause he came back a week later after she moved in to check it out, and I think he was looking to see if the mold came back.


TM: Wow.


VS: Strange things, so.


BO: [laughter] Oh, yes. 2021. You can do a lot of things and people don’t cast judgement anymore.




VS: We’ll talk about this later, like, cat-urine mold. Cats can go around and spray on walls, you can get mold everywhere from that too, so.


NS: Eww! 


BO: Oh my goodness, is that…


VS: Yeah, that’s coming up. [chuckle]


BO: What number is that on the list? Because…


VS: Oh, I didn’t remember them, but that’s definitely coming up, ’cause that’s a thing. Cat and dog urine mold.


BO: Humans, we love our pets sometimes a little too much.




BO: You can overlook a thing or two.


VS: My husband did one that was just out of control, like, they had destroyed the house. But, you’re right. People on their pets. I know how that goes. When I’m talking about framing studs behind sheetrock… Okay, so, one time I was in a house and I don’t know how they found this. And I think this happens in the stucco homes. The wall was rotten under. The studs were completely rotten under a window leak, but the sheetrock looks just fine, because the plastic protects the sheetrock. So this is one of the hardest things about finding mold inside walls, like, you could have no indication there’s a problem, but once they took off the sheetrock, it was totally destroyed framing studs in there. They must have found it from the outside and figured out water had come in from me outside, but that’s what makes it hard to be a mold inspector. Some of this stuff is hard to find. It can be rotten and you can’t even tell.


BO: That’s why they need to go to Reuben’s Water Intrusion Class, and they’ll hone in on that like a bloodhound and be like…


VS: Really? I think I need to go to Reuben’s Water Intrusion Class.


RS: I’ll send you the link.


VS: Yeah? Thank you.


RS: Yes.


BO: So let’s kinda keep pushing down the list here, ’cause, I mean there’s some things that are obvious and you can touch on those really quickly, but Vickie, where are these places that are the not so obvious that the mold kinda rears its head? 


VS: I would say carpet insulation, but you just asked me, should I move through the list a little quicker? 


BO: Well, but yeah, let’s just kinda touch on them, we’ll post the list, so everybody knows what we’re talking about, but I’m kind of looking for those Easter eggs that you wouldn’t really…


VS: I would say rim joist insulation. Rim joist insulation is in the top five places where mold hides, and some of it’s dust, but maybe test so that you can say, why does it condense there so much? Because the first time I started realizing this, it was so wet in the spring you could smell it. He called because of an odor because his insulation was all wet. And so a lot of this is dust that collects in the insulation, but then mold grows on the dust, so I’d say rim joist insulation and basement carpet are the two biggest sources because sometimes you have to pull back the rim joist insulation and it’s really dark on the back, so why does it condense there? 


TM: If you’re talking about a fiberglass batt type of insulation, air can move through fiberglass, it’s like a filter, it’s air permeable, and so when you have warm, humid air inside your house, and it’s cold outside in the winter, that warm, moist air will eventually move through that insulation, and will hit that cold surface of the rim joist, especially if you’ve got a gap between insulation, even if you’ve got an impermeable insulation like spray foam or like a rigid board insulation and it’s not touching the rim joist, you’ve got a gap between the insulation and the wood, that is a perfect location for that moisture to condense and sit there and then turn into mold, and so fiberglass, especially since that air will move right through it, you’ll get condensation on the back side of that fiber glass between the rim joist and the fiber glass. I don’t know, Reuben, do you wanna add anything to that? 


RS: Well, yeah, I’m reminded… My last house, and we had talked about mold problems in our houses, and I completely forgot my last house… Right when I bought the house, I knew about this issue. There was mold growing behind the vapor barrier in the basement, someone had put poly up in the unfinished basement on all the stud walls, and there was insulation behind that, and I had mold growing on that on the back side of the poly and in the fiberglass insulation all over the basement, it was a walkout basement, so I had it going on all over the place at that house, and it’s a result of warm, humid air coming into the basement in the summer time, and then condensing on the back side of that poly. And then you have moisture trapped in there, you end up with mold growth growing on the dust, so that would be a good example, too. And by the way, my solution there was ripped it all out, had somebody dispose of all the insulation, all the poly, there was no mold that you could see on any of the wood or any of the rest of the surfaces, and we ended up spray foaming the entire basement and that was the end of that. It was fine ever since.


BO: In that situation, is that mold a concern, like it’s outside of your envelope, so do you have to address it? 


VS: What do you mean outside the envelope? It’s in your basement.


BO: Well, it’s outside your condition space, it’s not the air you’re breathing, and so it feels like… ’cause there’s mold everywhere in the environment, right? You get outside, there’s mold everywhere, so would these level of spores exceed what you would just be breathing in at the exterior of your house? 


VS: Well, so interestingly, I just sent Neil a document. Because, this is one of the top five. Fiberglass and above grade walls in unfinished basements is one of the top five places that mold grows. And Reuben was right, it comes during the summer, but also the winter, the first time I ever saw it, I was buying a house, he pulled back the insulation, and there was slush on the sheathing behind the insulation, so I came right home, ’cause my house is the same age… I get ice crystals behind the insulation, and it gets through those staple holes, so the real way to prevent it is once you put up sheetrock, I think some of that moisture gets absorbed, so it’s gonna grow. I tell people, it’s not a building defect, it’s a building science phenomenon, nothing’s wrong with your house, this is gonna happen in every house, I have it in my house. You’re right, sometimes it’s just in the insulation of the vapor barrier and not on the wood, but I’ve seen it where, especially with OSB sheathing instead of build rite, you can get it on that, I’ve seen it build up really bad.


TM: You know, you want your air barrier to be consistent and continuous, any, even little staple holes through poly vapor barrier can allow a ton of moisture and humidity from the air to get into the wall cavity, and I would say, Bill, that a wall cavity, technically, is not outside the building envelope, it is the building envelope, and that air in the wall can circulate and get into the air that you’re breathing in the house, so it can be a concern for people’s health if there’s mold growing behind that poly vapor barrier.


VS: And then what I found through testing is 50% of the time it comes into the air, 50% of the time it stays behind the vapor barrier and you don’t know until you test, and so some people…


TM: Interesting, that probably depends too on the pressures in the house, is it a negative pressure, and it’s sucking air through the walls into the basement.


VS: How big are those holes, how much mold is there, yep. So some people when they have it, they’ll have me test and if it’s staying behind the vapor barrier and they’re not gonna ready to finish their basement, they’ll take it off when they finish their basement and start over, ’cause even though it’s part of the… I would take it out before I would build, even though it’s part of the envelope, it is mold. Some real estate agents will say, ‘No, it’s just dirt,’ but I have tested enough of it to know it is mold. Never the toxic black mold… There’s not enough moisture to grow the toxic black mold, but it’s mold.


BO: Vickie, can you talk about testing just a little bit, we’ve talked about places, and we’ll continue to talk about places, but what does this testing look like, and is it something that catches every room, can you tell how much is in every room, or do you have to test in every room? 


VS: That’s a good question. When I was first trained, they told me that… So you do air testing… Mainly, I do air testing and surface testing, so an air test is done with a plastic cassette hooked to a pump and you draw air through and there’s a microscope side inside with sticky tape that counts your airborne spores. A surface test is a taper swab that says, “Yes, that thing on your wall or your insulation or carpet is mold.” When I was trained, they said, “Oh, this would cover 1500 square feet.” There’s a guy on the internet that I trust that said the capture zone is more about the size of a football. I’m gonna go with the latter. It’s not 1500 square feet, I have tested locations about 15 feet apart and gotten different results, so then a lot of people test on a tripod.


VS: They put this little plastic that sat on a tripod, I left my tripod at someone’s house, so I started testing, I run a full 10 minutes. You run the air test depending on if I see sheetrock dust, well, maybe I just say get rid of the sheetrock dust, I’ll come back when it’s gone. But I need to test when I can tell something is in the air, and I’ll run a shorter test. But mainly I run a 10-minute test. So I slowly move that around the room, I go from side to side and different heights, so I think I get better air tests because of that approach. Now, someone told me that there’s a guideline for testing that said I shouldn’t do that because if I’m walking on carpet, I could be releasing some spores… My thought is like, we’re trying to find the spores in the room, not just the air, so there are other people that do agitated air test, so there are different caveats for ways to do this testing, but I have found that I get really good results when I slowly move that around a whole room, but pretty much one room at a time, if you wanna know everything in your house, you’d probably have to test every room.


TM: Neil, is that kind of the same approach you’re taking? 


NS: For testing every room? Yeah, well, we typically do like Vickie does, one outside one inside, and I try and select the area that would be the highest concentration or the area of most concern, which to me is in Minnesota our basements. That’s where I always… Get down to the basement and we talk about common areas or that concrete block, it’s gonna be black and moldy. To me, that’s number one spot and then just to piggy pay back on what you said about the rim joist area, you pull some of that fiberglass away in the cold areas in the winter, there’s frost back there for sure. So that frost melts, gets wet, causes mold. So I’m in agreement there, for sure.


VS: So what’s the deal with this new gray muddled insulation that they’re putting in? Do you guys know what I’m talking about? It’s no longer pink or yellow, it’s gray and it looks moldy from that start. I don’t know the reason.


RS: It’s called pre-moldy.


VS: I’m like oh, great, now, it’s gonna be harder to tell if that’s gone bad because it’s… Really weird…


TM: Is it rock wall? Or is it fiber glass? Or what’s the texture like? 


VS: I don’t know, it’s like fiber glass, but I don’t know the difference between rock wool and fiberglass, rock wool.


TM: I wonder if it’s rock wool…


VS: You’ll see it… But it’s very strange, it’s sort of muddled looking it looks moldy. It’s not, it just looks moldy. It’ll make our jobs harder.


TM: Send us a picture.


BO: I think I have some in the cabin, and I’m not sure why the contractors used one and then went to the other, and maybe it was a supply issue, who knows. But I think I know what you’re talking about. It’s kind of a more organic looking material versus the pink that we’re used to seeing or the yellow, each of those manufacturers did that kind of as a branding thing, wasn’t it? 


VS: Oh, oh, Okay.


NS: Probably.


BO: I mean, pink insulation was always Owens Corning, and yellow was… I forget… Neil, You’re gonna have to tell me this one…


NS: It’s not coming to me. Sorry, Reuben, you got it? 


RS: No, sorry.


BO: We’ve stopped Reuben Saltzman. Mark it down. This is a moment in time. Believe it certainty.


VS: So what kind of, Tessa, do you like? The spray foam on the rim, or do you like… I like the little panels where they cut ’em and fit ’em in because I think that’s cheaper.


TM: Yeah.


VS: And easier to remove if you have a problem, but that’s just my opinion.


TM: I would say, if you’re cutting individual pieces of XPS or EPS rigid foam and putting it in between each floor joist at the rim area, the labor is gonna be really expensive on that, just the amount of time it takes to do that, so I think it’s more cost effective and easier just to do… If you’re talking new construction, the spray foam, and that’s what you’ll see in a lot of new construction is just closed cell spray foam sprayed right against the rim joist. It’s interesting, ’cause I’d say in older houses, there are pros and cons to insulating and you have to kind of weigh those pros and cons and figure out what’s best for you. There are some houses where I wouldn’t recommend, and people are gonna cringe and say this, wouldn’t even recommend putting insulation in the rim joist. Because when you do that, when you add let’s say fiberglass against a rim joist, you’re actually preventing heat and air flow from getting to that room, and so you’re reducing the surface temperature of that wood, which will cause more condensation issues when the warm, humid air in the basement gets to it and touches it.


TM: It’s the same kind of phenomena of like in the winter time, if you keep your blinds closed all the time, you’re gonna get more condensation on your glass because you don’t have that heat and that air flow getting to it and warming it up. So your basement rim joist can have the same problem. You put the insulation in there and you actually create a moisture problem that you never used to have when it wasn’t there, and you would just have more heat and air flow moving through it. And that’s the problem with houses, and you’re looking at what type of materials they use, is there energy moving through that material to dry it out if it gets wet? When you put materials over top of the wood, like fiber glass insulation, you’re decreasing the drying potential of it, and it can actually create mold or durability issues. So I think it just depends on the house, it depends on the situation of whether or not I’d recommend adding insulation.


BO: Yeah, and Tessa to talk about that point a little more, you talk about some of the downside to that, there’s a blog post I did, I think it was last year, it was about a year ago, and it was titled Beam Fill and the Case of the Missing Rim Joist.


TM: Yes.


RS: And it’s where they would put beam fill on the rim joist area and then typically they’d insulate over it, and so often we’ll find that there is no wood behind that beam fill anymore. The rim joist is completely gone. It just rotted away to absolutely nothing and I’ve got a nice photo collage of houses where we found that happening… So yeah, there can be really serious consequences.


TM: Drying has to be greater than the wetting, right, and if you’ve got wood buried in this beam-filled concrete and it’s wicking moisture, or you’ve got insulation against it and you still have these condensation issues and moisture getting trapped, then you’ve created a new problem. So you have to be really careful. That’s what building science is, is kind of weighing the risk to the benefits and figuring out, okay, yes, you’ll save money on your heating, cooling costs and maybe make it a little bit more comfortable in the basement but is it gonna create mold, moisture, durability issues? 


VS: It’s interesting you say that because my house is 18 years old and I’ve never had any rim joist insulation and my heat bill is really low.


TM: Good.


VS: So I wonder, do you need it? Because I don’t have it and I’m not having a problem.


TM: Good, hm.


BO: I think you’re chasing after maybe cost savings that aren’t gonna be there, right? Experts way smarter than I can tell me if that’s false statement, but at some point you just have to go: Is it worth it? After I do all that work and pay all that money to save whatever it is on my heating bill. I was thinking as we were sitting here, surface mold, Neil, Vickie, do you get really worked up about surface mold or is it just something you feel like can be wiped off and cleaned off, and life is good? 


VS: Surface on a window, on sheetrock, on an attic sheathing? 


BO: Yeah, It depends I guess. I’m talking inside surfaces inside your house, things that discolor, that look awful ’cause they turn that black or dark brown color, but I’m not sure that there’s a lot to be afraid of when it comes to that type of mold.


VS: I tell everybody, in fact, I’m going to do a test tomorrow where the restoration company has… He mentioned the word mold and the office manager is having a bird. People shouldn’t be so afraid of mold, take it seriously, but… Yeah, I mean, ’cause you said you shouldn’t be afraid of. It really is just water damages and moisture is the problem, small or big, but, yeah, nobody should be afraid of mold, but a lot of people are. So I do talk about here… Mentioned if sheetrock has been wet when you have to cut it out because it could be in the framing studs on the back side. There’s the condition I’ve nicknamed gold mold, it grows on unpainted sheetrock, you’ll see it in the basements around the steps, or if someone has like an underground garage. It’s only on the unpainted sheetrock, it’s a little yellow spot. It’s Aspergillus, but I call it gold mold.


VS: So when you have that, you vacuum it, scrub it, Zinsser Mold Killing Primer and Zinsser Perma-White paint. Surface mold would be on your windows, I mean, I kind of think all mold is surface mold because it’s really not… Wood rot is a different fungus, if you’ve got wood rot, you don’t have mold anymore, it’s a whole… Now it’s a different fungus that’s taken over. So I would contend that most mold is on surface. Once it starts going deeper, you do have a bigger problem. If you have a serious leak that goes on and your wood’s rotting, that’s not mold anymore…


BO: I guess what I was thinking, Vickie, was you walk into a room, and you with your sensitivities, and all of a sudden, your tongue starts swelling up and your… You hit like three of the four conditions, but you don’t see anything. You’re like, this room looks totally clean, and that’s where I feel like bells and alarms would be going off, like, “Hey, there’s a problem in here.” Where you walk past a window and it’s got every color that you can imagine right out in the open for you to see and it doesn’t bother you in the least.


VS: Yep, because it’s different types. I mean, people are allergic to different types, but, when we were talking about framing studs, and the question was about below grade, that is one of my biggest questions. So you have framing studs on a wall, they’ve been there for 30 years, there’s probably some insulation and vapor barrier and paneling or sheetrock, like, those things are getting a little damp back there, so that’s one of the hidden causes where I would probably react and you don’t see it, is the framing studs behind walls and finished basements.


VS: Even, and so I had a question mark, either, like any wall, like the wall sitting behind me, could that have mold in the fiberglass? There was a house I saw once in Blaine, I took up the sheetrock and yes, the fiberglass on the main level did have some mold. And I just think that we live… And I’m not a building scientist, but my understanding is, if you only heat, like if you live in Alaska where you don’t use a lot of cooling and you put the vapor barrier on one side, if you primarily heat… If you’re down in Florida, you primarily cool. You put it on a different side. We live where we heat and cool and you’re not gonna keep the condensation out of that wall.


BO: So I’ll just and I know she wants to talk about it. [laughter]


NS: Look, I’ll just throw this out if you’re gonna throw my name in there Bill. Yeah, I would say we should be concerned about it if we see it and we should clean it up, and mold can be cleaned up. And then we got to be concerned about the relative humidity inside, make sure that that is low. If you’ve got a high relative humidity, you’re gonna grow mold. So that’s one area we wanna address with our clients.


BO: What about our wood floors that are gonna move around, if we don’t have 50% humidity in the house? 


NS: You don’t wanna go above 50, yeah.


VS: So that was one of my things on here, was the whole house humidifiers, because people think my conclusion is that spec guys love ’em, but the building scientists hate them. And I see people leave them, they’re supposed to turn on to a summer/winter switch, people forget to turn that, so now they’re putting all this humidity in the summer. People swear they’re off because this control is gonna measure the humidity, like, “No, they’re running most of the time”, I just tell people to take them up because I agree that no house needs an extra humidity.


BO: We did touch on one thing briefly and then got away from it, but I do wanna ask about this because it’s something that looks scary when you see it, but I’m wondering if it’s really scary, and that’s mold on attic sheathing. What’s the recommendation there? 


VS: Okay, so most attic mold is found in the summer when someone’s selling their house and a general home inspector finds it. But it happens in the winter because… And this is in here too, people think, “Well, I don’t have attic mold because I don’t have a roof leak.” Most attic mold is coming from condensation at roof leaks, so most of it’s gonna be dark. When you go up there and you see white mold growing up there, that’s more humidity. And there was one last February, when it was really cold, the whole month of February, all we worked on was attic. And I did not know an attic could smell musty. This was this bad, it was raining so bad, the woman had to have a bucket in her kitchen to catch the water coming out of her attic. Because she bought a town house, the roofers roofed over the vents, so that was one problem, it couldn’t escape, but she was also, liked it really hot and humid in there, so she kept it 80 with 80% humidity, so the perfect storm of this going up there.


VS: And she had the white and the dark, but it smelled musty up there, so that was really alarming. But the reason it was so alarming is two months before that, we were working over in Hudson and there was a small Rambler, a low-pitched roof Rambler, 45 years old. I joke like, “Why did it take me to figure this out?” Okay, so they’d had so many attic problems, they’ve been fighting water stains on their ceiling, someone had put in an air exchanger hoping that would help. Two years before, their wood in their attic had gotten so rotten that they had to chop off the top of their house and put on new rafters and new sheathing. And so we went there, opened up the attic, you could see right over the bathroom it was already black and icy again.


VS: The rest of the attic was still okay because it was only two years old. The problem was the bathroom fan vented out the side of the house, not up through the roof. And for 45 years, this little bath fan… And she had her bathroom remodeled, she had the air exchanger, who didn’t check this bathroom fan sending all the moisture right up into a vent. It came out of the fan and up into the attic for 45 years. So when you see something like that, that’s really drastic, but when you have to chop off the top of your house and you don’t fix that problem and you’re risking that again, or you have this musty smelling. When it gets that bad, that’s the problem. I agree with you, a little bit of mold up there isn’t going to contaminate your living area, but if you don’t control the moisture, you can get in trouble like that.


BO: I wonder sometimes it’s like, that’s there, I’m here. Is that as big of a concern? And everybody has, the answer to that is, it depends who owns it. So if I own it and I’m trying to sell, and somebody looks at it and says that’s a concern well then, now I’m on the hook. And even though I’m not worried about it, I have to make a decision. Is it a big deal or not? And…


TM: You know what? I just wanna add something real quick. Reuben and I talk about this and continuing education courses for real estate agents of like, what’s a big deal? What’s not? What do you do about mold growing on an attic on the sheathing and stuff? Yes, most of the time, it’s caused by warm, humid air from the house, leaking up through these attic bypasses and getting into the attic and then condensing on the under side of the roof sheathing. And so if you don’t seal those attic bypasses or if you’ve got a fan that’s venting into the attic, that’s just… That’s a whole house attic humidifier going right there, it’s gonna make the problem worse and you’re just gonna continue having that problem.


TM: But if you stop the source of the moisture from getting into the attic, seal up all these little attic bypasses, then the air in the house and to the attic is not going to communicate… There’s not gonna be any pathways for that moldy attic air to get into the house if you do proper air sealing. So would you be concerned about mold that’s growing on the outside of your house? No, that’s outside the building envelope. So the recommendation we always give people is, okay, we can see some signs of moisture up here. Stop the source of it, seal these attic bypasses, make sure fans are venting out properly, and if there’s a little bit of mold up there, I wouldn’t be concerned about air quality in my house because of it.


VS: You’re right, the type of mold that grows up there tends to be Cladosporium, which doesn’t really spores, but during the summer, the air flow can be a little bit different. If you’re super sensitive and you have a bad problem, you could maybe be affected in the summer when they…


TM: Definately.


VS: Instead of warm air going up, the air is coming down.


TM: Yes yeah, if you have these big attic bypasses and that attic air is being pulled into the house because of the negative pressure, if you’ve got a air conditioning system that’s running and pulling that air in. Yeah, for sure.


VS: But this was my question for you Tessa because 80% of the time when people have attic molds, they clean the sheathing, the insulation stays. And so we talked about how prone insulation is to mold, but is the attic insulation… Does the condensation only happen on the sheathing or is that insulation laying on the floor prone to condensation that… Because that’s a gray area for me, I never know, is it moldy, should they keep it or not? 


TM: Well, I’ll give it my best shot to answer, but I’m curious to hear what Neil and Reuben and Bill, what you guys think too, but I feel like I’ve seen so many attics where moisture in the attic was a problem, and you could see condensation on the roof decking or even the raining attic syndrome, you just mentioned, with the woman who was catching the water dripping through her ceiling because of that, where the insulation just gets soaked. And I think if the insulation gets soaked, I’d probably recommend replacing it, but I don’t think I’ve ever seen, visibly seen mold growing on fiberglass or mold growing on a like a cellulose. And I’m sure they put chemicals and mold inhibitors in that, so that’s a good question. I think if it can dry out pretty quickly, I wouldn’t be too concerned about it. What do you think, Reuben? 


RS: I can say during the winters of 2009, ’10 and ’11, I did a ton of ice dam inspections. We had really snowy winters, and I was in a lot of troubleshooting for people, finding a lot of attic bypasses, and there were a handful of attics I went into… Now granted, this is like a decade ago, but there was a handful of ’em I went into where there would be frost on the top layer of loose fill fiberglass insulation, so it’s like you can kind of put your hand on it, you rub your hand over gently and you could feel the insulation was all wet in frosty and there’d be some dark marks in that insulation. If the insulation was the right color, you could see it. So it can happen, it’s just really unusual. It’s gotta be extreme circumstances for it to happen, I’d say most of the time it’s happening on the really cold surfaces, like the sheathing and the nail heads.


NS: I’d say that’s where I’ve seen it, sheathing nail heads, but very little on insulation in the attic.


VS: So it’s okay that 80% of the people leave their insulation… That’s kind of what I thought too, but…


TM: Yeah. I would say so.


NS: I would say so.


BO: And I’m completely unqualified to answer this question, but I would think that the fiberglass would be less of an issue than the cellulose, depending on when the cellulose was put in, and there’s all kinds of other things in your attic too, it’s a pretty dusty area and you get other creatures living up there sometimes, and mainly behind things that could probably turn to mold too. Okay, I think we should maybe begin to put a wrap on this, and we failed at the beginning ’cause we said we’re gonna get through 59 things. We knew we weren’t gonna get through seven of them. Okay, it’s just the way it goes. These conversations begin to meander and this situation, this topic is complicated, and if possible, Vickie, I think we should just go ahead and decide now, we’re gonna do a part two, and maybe we’ll get to topic number 15 by the time we’re done with a session number…


BO: But we’re gonna go further on this on our next episode because it’s really interesting that there isn’t one thing that causes mold, there’s not one solution for fixing it, and everybody kinda has a little different thing about it and that’s what makes this such an interesting conversation. But thank you, Vickie, we appreciate you spending some time and signing up for another long conversation about your work. Remind everybody where they can find you.




BO: Awesome.


VS: There is only one thing that causes mold and that’s water, on the technicality.


RS: Very good.


BO: Thank you for correcting me because somebody would have but everybody, thank you for listening you’ve been listening to Structure Talk, a Structure Tech presentation. My name is Bill Oelrich, alongside Tessa Murry and Reuben Saltzman. Thank you for listening we will catch you next time when we go deeper on this conversation.