Andy Wojtowski

Podcast: Air Quality with Ross Anderson, Part 1

We interview Ross Anderson, president of the Minnesota Building Performance Association. We discuss energy score ratings for homes, managing indoor moisture levels and indoor air quality, and challenges faced by Minnesota homes. We also discuss the perfect setting for an air exchanger in a home, along with the ideal humidity level for a home.

You can get in touch with Ross through his company website, The Energy Network Worldwide.


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.

Ross Anderson: Climate zones are very important, especially if you’re in Minnesota where we build to the hottest hot and the coldest cold. So, we’re unique in how we build compared to a lot of other climate zones.

Bill Oelrich: Welcome everybody to Structure Talk, a structure tech presentation. My name is Bill Oelrich, your host alongside co-host, Tessa Murry and Reuben Saltzman and today in the studio, we have a guest with us, Ross Anderson. Ross is a indoor air quality expert. Is that fair to say, Ross? Go ahead and introduce yourself, if you like.

RA: Sounds great. That sounds great. I like that a lot.

BO: And you’re also the president of the Minnesota building performance Association.

RA: Correct Minnesota Building Performance Association, just a bunch of geeks from the University of Minnesota, Department of Commerce, a lot of energy testing companies, HERS Raters, sit around and talk about building science and get excited.

BO: Awesome.

Reuben Saltzman: We joined. Are we the only home inspection company?

Tessa Murry: Yes.

RA: You are, you are the only home inspection company, which is a little disappointing.

RS: Alright. We get that distinction.

BO: So Tess is our resident building science expert on the podcast, but we brought Ross in to talk about HRVs, ERVs and I expect a full-on geek fest to happen here in about 15 or 20 seconds so I’m just gonna unload and let you two go at it, right? Let’s talk about indoor air quality.

TM: Well, and so much more, ’cause Ross, aren’t you working with a lot of new construction builders…

RA: I do.

TM: And doing energy rating stuff?

RA: Yeah, so we do probably about 2,000 home energy ratings on new construction projects a year.

TM: Wow.

RA: So I get to see a lot of different homes from big customs to small production builders, so we get to see the whole gambit and help them try to build better homes.

TM: And explain the testing that you have to do ’cause you’re doing HERS ratings, you’re doing blower doors. What else?

RA: HERS rating basically, in layman’s terms, is kind of a miles per gallon for the house, it gives new construction house and existing homes, it gives it a miles per gallon score. The scoring system is zero to 200-300. Zero would be like a net-zero energy home. And it can actually go negative, so if you do have solar or wind on-site, you could actually go negative and sell power back to the grid.

BO: Okay, so we use a lot of acronyms around here. Does HERS stand for something or?

RA: Yes, it’s the home energy rating score is basically what a HERS score is.

BO: Gotcha, great.

RA: So it’s just the score that we as raters give a house and it’s built on a metric, so the energy efficiency of the appliances in the house, the heating system, how efficient and how the building shell is, the R values in the walls, how efficient the windows are. It all kinda goes into the final calculation to give it that energy score.

BO: Very good. I believe I had my home tested and received a HERS rating of… Feels like it was in the 80s. 1941 house in St. Paul.

RA: That is an excellent score. So 100 is kind of the national standard if your home was built to the 2006 energy code. So nationally, this is scored nationally, and it varies by climate zone. So a Minnesota house, score of 40 would be a little bit different than a Florida house score of 40. But the goal is that you score by climate zone. So as you’re comparing homes, I wouldn’t compare a 40 in Minnesota to a 40 in Florida. But in this climate zone, which we’re six or seven, for the Department of Energy, which kinda gets nerdy, but in the end more or less what we’re saying is this miles per gallon score is what we’re looking for. So if 100 is the 2006 and lower is better, I always say like golf the lower the score… Unfortunately my game is not that way, but the lower the score the better, and 80 would be actually really good especially for that year because the average one I see right now is about a 50 and that’s new construction where you get to do a brand new out of the box, so that’s actually pretty excellent for an older home.

BO: Well, it may have been 18, I don’t know. I just threw a number out to get the conversation going. And the guy who did it, Tess, you trained with him, Bruce Stahlberg and I know Bruce is a part of…

TM: Oh yeah, Bruce. MBPA.

BO: Yeah. So he was a fantastic guy, and I asked him that question, “What does this mean?” And he said, “Well it depends”. He gave me the standard answer.

RA: It’s a beautiful answer. And the score is nice, the score kinda gives you a little comparison. So, as it’s getting more popular in it’s… There’s actually a national Rater registry now for new construction home, so you can actually go on the Resnet website. Resnet is the oversight, and actually find out if your home has a HERS score. It’s all on there now, so it’s really cool. And especially if you’re buying a house you can find out what it originally was rated at and what the metrics were on the house when it was built.

BO: So you and Botanists kinda have a similar interest in climate zones, right?

RA: Correct. Climate zones are very important, especially if you’re in Minnesota where we build to the hottest hot and the coldest cold. So we’re unique in how we build compared to a lot of other climate zones.

BO: Can you dig into that for a second? Just why are we so unusual up here?

RA: Well, we have a lot of humidity, we have very cold winters, record cold winters quite often. And in the summer time we’re 100-plus degrees for some two to three weeks at a time. So now you have to build a building shell that can manage extreme amounts of moisture, extreme cold, and extreme warm temperatures and so we don’t just get to easily do an Alaska home where we’re mostly cold or a Florida home where you’re mostly warm, or even an Arizona climate where you’re really warm and dry. And so you’re really just managing one aspect of the build. So Minnesota we have a tough road ahead of us to build a decent house, that’s gonna last longer than 20-30 years.

BO: Okay, so if you do it wrong, we’re looking at 20 or 30 years on the high side?

RA: I would say, yeah.

BO: Great. Well, at least everybody knows what they’re doing and they don’t have any challenges.

TM: So I was gonna ask Ross, you work with a lot of builders and new construction. Building these houses is not easy, what are the most common things that these builders struggle with that you see while they’re building these houses?

RA: Well, I think the most common thing that builders struggle with would be educating each individual trade on how important they are to the building shell and how the building is constructed. So if you are concentrating on really getting a tight well-constructed building shell and your electrician comes in and punches a bunch of holes and doesn’t insulate or the plumber does some stuff that he doesn’t understand or people are drilling through different things. Just making sure you’re managing all that. And honestly, with the labor shortage in the construction industry, we’re seeing job superintendents stretched and not able to visit their job sites as much as they probably would like to, to stay on top of that. So that’s probably builder side, something they would be concerned about, I mean land prices and we can get into a lot of other things that make it difficult for builders to be price conscious, so they have to bid down their prices and get the lowest bidder in and people are asking for price per square foot and sometimes they don’t think they know what they’re asking for when they ask for that, because that pushes that builder into that lowest bidder realm so that he can compete and sell houses. So I think that that’s probably the biggest challenge builders have.

RS: Which was not educating all the different trades and letting them know how important their role is in energy efficiency?

RA: Correct.

TM: And building performance.

RA: Building performance, and comfort and all of it.

TM: Yeah, all of it. It’s like we’ve got all these different trades and they’re disconnected, no one communicates and so things get missed.

RA: Yeah, all the time. 100%. I think to one of the builders faults is a builder will design a house, or an architect will design a house, and then he gives the plan to the HVAC guy and he says, “Alright, I need you to get… Here’s your mechanical room down in this far corner and now you need to heat the room that’s up bonused over the garage and that has to be the right temperature, but you have to get over these six beams and around these four curves and make airflow go there”. And then the plumber’s gotta somehow get his piping over there and the electricians got to manoeuvre his stuff around and they’re all fighting for space and fighting for capital inside the building. It’s really good, if you find a builder that has a team that they’ve worked with for many years and all work together well, the odds of you having a really good house in the end are much, much higher for sure.

BO: Boy, this is good stuff. But my head now is filling with questions and I can feel it swelling as we’re sitting here, we’re gonna step away for just a minute but when we get back let’s dig into this indoor air quality topic a little bit and Ross piqued my attention at a training event that happened a couple of years ago and that’s why we called him in and so let’s talk about indoor air quality when we get back. And Ross, please tell me your company.

RA: The company that I currently work for and do HERS ratings and energy testing for new construction is The Energy Network Worldwide. Worldwide we added ’cause we thought it would be cool I guess, but we’re currently Minnesota only. Dream big, I think that’s the goal.

RS: We could do the same, you guys. So what do you think?

BO: Structure Tech 1…

RS: Structure Tech worldwide?


RA: Worldwide.

RS: Structure Tech Worldwide.

BO: He’s taking me back to my youth of the Saturday morning in world wide of sports.

RA: For sure.

BO: Yeah, there you go. Okay, we digress. Alright, so two, probably three, years back, Ross had a training session for HVAC technicians, which we are not, as home inspectors. But some of us home inspectors showed up that day and you were talking about HRVs, ERVs and these great little mechanical boxes that sit in the basements of new mechanical rooms in houses and you mentioned one thing and it just struck me. And you talked about houses are never static, you can’t just build it and set it up and expect it to perform like that forever. And you said at times will come into people’s houses and try to set up their house according to how they live in their house, take us through why that’s important.

RA: Well, I think if your home has an ERV or HRV, and it’s… One is called an energy recovery ventilator, it manages a little more moisture and humidity, where the heat recovery ventilators is basically just recovering heat. If you go back to the reason why we’re putting those in now it’s because the thought process for the energy code nationally and especially in Minnesota is, the tighter the building shell the more energy efficient the home will be. If you don’t have the air, the warm air, rising and leaking out the attic in turn, trying to balance the pressure to pull the cold air in, older leakier homes obviously you feel that draft constantly, so you’re constantly running your furnace. The tighter the building shell that you have on the house the less the furnace runs and so that’s the goal. We want the furnace to run least as possible, we want the heat to stay in the house or the air conditioning to stay inside the house. That being said, the other stuff we trap inside is all the moisture.

RA: As we breathe, cook, clean, shower, we create a bunch of moisture in the house and now we’ve trapped all that moisture inside the house also. So the ventilation systems were put in place to help manage that moisture that’s in the house. Now, I laugh because quite often I see older couples building these houses I call their pyramid, which would be the eight bedroom monster house that they’re building at the end of their life, and it’s a couple that lives in this house and the house is set up to ventilate for eight bedrooms and two people live there. So if you have a house that’s set I think, not to get too techy, but the code is.

BO: Oh, we like techy.

RA: Bedrooms plus one, so it’s ventilating for… If it’s eight bedrooms it’s ventilating for nine people, right?

BO: Okay.

RA: And you have two people that live there, you’re over ventilating this house. You’re getting quite a lot of ventilation, so being able to ramp that ventilation down is something you’d wanna manage. And vice versa, if you have a house where you have a lot of family members. I always laugh because my house at Christmas time, we will have all my in-laws from South Dakota come in and I have 16 people now staying in my house, crammed in there for a weekend, and my windows will be raining water. So my ventilation strategy is go around and crank every bath fan on and tell everybody leave them on, right?

RS: Yeah.

RA: So that’s our ventilation strategy for the weekend. But when they all leave…

RS: Do you have an HDRA at your house?

RA: I don’t. I know, my house was built in the ’90s. It doesn’t need one, as I do more improvements at will.

RS: But if you had one you would crank that all the way up to high as soon as everybody got over?

RA: 100%. And actually windows are a great way to manage your moisture in your house. As you see the windows start to get moisture on them and beat up, turn your… If you have an HRV or ERV, I would turn it up and then as that dries out you can bring it back down. But to your point earlier, 100%. People move in and it might have been a six-bedroom house that had six people living in it and now the new homeowners are just two people in this beautiful big house and that ventilation system is running constantly for six people. And that’s how it was set up by the builder and that’s how they leave it. And if you don’t need it that high now you’re actually wasting energy by running that thing a lot more. Go ahead.

TM: I have a question.

RA: Go.

TM: And Reuben does too. And I know you do too, Bill. Okay…

BO: You guys don’t have to raise your hand, ’cause nobody can see it.

RS: Otherwise we all talk at the same. She’s doing that for us.

TM: I know. I’m claiming the floor space.

RS: Tessa’s got the conch.

TM: How many of the builders that you work with… How many builders do you work with? You said before the podcast…

RA: I’d probably… Well, we do 2000 homes. I’d say we probably work with 40 builders in town.

TM: Okay, that’s a lot of builders. How many of them understand the calculations that go into figuring out how much ventilation a house needs and understand that and understand how the system works and can explain that to their clients?

RA: Very few, if any. The builders I work with, we try to put together a strategy so that when they hand off the house to the new homeowners, whoever it is, that they actually have a strategy of how they’re gonna tell the people about that. Because now that you have this super tight house that piece of equipment that no one grew up with, no one’s ever seen before, all of a sudden it’s in their house and they go down and look at it. I always tell a funny story in my presentations, and a true story. A good friend of mine built a $1.2 million house, he calls me up and his windows are raining water and he’s gonna sue the builder and the builder put terrible windows in his house, and middle of winter. And I’m like, “Wow. Okay”, so I go over. First thing I do is B-line to the mechanical room, go down there and there’s that plug-in. Just waving in the wind.

TM: Not even plugged in.

RA: Not even plugged in. And I ask him, I say, “Is this how you got the house?” Because he’s only been there for six months. “No, no, that thing just brings cold air into the house so I just unplugged it, what do I need that for?”

TM: And he probably had his April air turned way up too.

BO: Can you sue yourself? [chuckle]

RA: So he wasn’t very happy, I think he was kinda excited to sue his builder. But anyways, in the end, it was his fault. But it’s really the builder’s fault for not educating him…

TM: For not educating. Yeah.

RA: On how it works, right?

BO: That’s awesome information, I love these conversations but we’re gonna step aside for just a second, and when we come back we’re gonna get to Reuben’s question.

RS: What’s the magic number that everybody should set their HRV or ERV to, Ross?

RA: That is my favorite question, ’cause every builder would do that if there was a magic answer. The best answer is you’re just gonna have to live in your house and figure out how it works the best, because some of the issues we run into are, as ERVs and HRVs are installed, the basic mechanics behind it is, it’s a box that brings air into the house, fresh air from outside, while it exhausts the stale air out of the house. As the stale air leaves it pre-warms that cold air as it comes in. So you’re not getting the blast of cold air directly into the house. Now that being said, over time, they plug. And the intakes get dirty and people don’t clean the filters, just like they don’t change their furnace filters. So if you said 20%, 30% or however the gauge was set is the number and no one is changing the filter or doing anything, it should probably be 50% or 60% as it’s ramping up. So winter is really crucial, really paying attention to the moisture on the windows and that frosting going on is really what I would pay the most attention to, just kind of a no-brainer easy way to kind of monitor how your home lives. I always tell builders, they’re building Ferraris now, right?

RA: People in the day we all used to build Ford trucks and we could change the oil and do all the work on them. Now we’re building these high-powered Ferraris. And people don’t know how to change them, and they don’t know what to do with them and they’re just not educated enough on what to do with these great houses.

RS: And they’re a lot more sensitive too.

RA: Unbelievably sensitive.

RS: Would it be fair to paraphrase to say if you got an HRV run it at the minimum setting it takes to prevent condensation at your windows?

RA: That sounds perfect, that would be a great rule of thumb just because they do use energy and the more often they’re running they will tax your energy bill. So if you’re running them at high all the time you’re gonna have an energy penalty for that. And you’ll get over-drying and you’ll have issues with your hardwood floors and cracking and other things like that. There’s kind of some unintended consequences of over-ventilating your house, but under-ventilating is obviously where you’re gonna run into some of the mold, moisture, and other issues.

RS: So what’s the ideal humidity level to keep your house at during the winter? [chuckle]

RA: Oh what a great question, Reuben. I would say the most humidity you can handle without wrecking your house.

RS: Perfect, perfect.

RA: There’s a lot of people that like them very humid.

TM: Depends on the house too.

RA: Yeah, and if you have an older house that ventilates naturally, the cold air outside is gonna be a lot drier and you’re gonna feel drier. So I’ve been in a lot of older homes where they’ve had multiple humidifiers onto the furnace system, which scares me quite a bit.

RS: Yeah, me too, yeah.

BO: Larry is raising his hand in the background. We’re currently in what, a 1910, 1905, 18-something, okay, wow, 1890. It ventilates well.

RS: Yeah.

BO: Let’s just call it that.

RA: They do.

RS: It’s a durable home too.

BO: Right.

TM: Resilient.

RS: I was talking about how these old houses with all this air leaking through the walls, it is very durable. You’ve got a built-in drying method.

TM: Can dry.

RA: They dry out nicely.

BO: So if you’re taking visual cues off the windows, are all windows created the same, and are the visual cues we’re getting in my house the same as what we’d see in Reuben’s house or Tessa’s house?

RA: I would say they’re very similar. And you’re looking at… So an R value, if you were to take the R value of a window, you’re looking at the difference between, even if you have an extremely efficient window, it’s probably an R7 or an R8, unless you have a super-passive house window that’s R14. But the average window is probably an R3 or an R4, even if you go from a single pane, which is nothing, to a double pane or something nowadays. The efficiencies of windows is more the air sealing with new windows than it is so much the R value or the…

TM: Glazing value.

RA: The glazing and stuff on it, correct. They’re still great, and they’re still quite a bit better than they used to be, but it’s the air leakage and the air penetration for the windows.

BO: So we’re not making any adjustments if the single panes are one way, you don’t go, “Oh, turn it down a little, we need less ventilation on that home.”

RA: I would bet that if you have single-pane windows in your house, you probably don’t have an HRV or ERV.


BO: Well, exactly, exactly. So thanks for bringing it to realness.

RA: But if you do, then that probably works just the same.

BO: I thought I needed one at one point, but somebody thankfully talked me out of it.

TM: Do you have bath fans and a kitchen vent in your house?

BO: That’s a whole different conversation that we won’t have on this…

RA: That’s a whole another trail we could go down.

BO: Yes, yes.

TM: So Ross, what are some of the most common warranty issues that you’ve seen working with new construction?

RA: Funny you bring that up. I always, in my little presentations, I always say it would be very interesting if people could test drive a house, how much different houses would be built nowadays. If you could actually test drive the house, live in it for a couple months and say, “Huh, for some reason, these two bedrooms are not very warm and are very difficult to keep above 50 degrees or 60 degrees,” they would change quite a bit. But it’s always comfort. It’s always comfort, almost always comfort. The number one callbacks for people is comfort. If you have a major water leak or anything like that, that means there was a defect in something and that usually gets fixed pretty easily. The comfort issues are the tough ones, they really are. A great way a builder could build a house would be if they would all just meet at the beginning prior to designing and everybody could get their area and their chases and have them all cleaned, homes would perform so much better but it’s just… It’s not in the cards right now. But yeah, comfort, to answer your question. Comfort’s number one. And I laugh quite a bit because the bonus room over the garage usually is the master bedroom.

TM: The least comfortable room.

RA: Yeah, and when Mom is not happy then no one’s happy, so that’s the calls I get quite often.

TM: And you know what’s fascinating to me is, and I’ve heard this a lot too from people that have lived in new construction, and they say, “Well, this house, it was built to code, so why am I having all these issues?” Right?

RA: Yeah, and code does a really nice job of addressing safety and fire. They do not as good of an issue of addressing energy efficiency and comfort. Comfort is not even in the code. They really don’t care if you’re comfortable or not, it’s more or less that… That would be something the builder and the HVAC contractor need to talk about.

TM: Building performance does not equate to passing code.

RA: No, and code really is… It’s just passing, right? And we talk about it all the time, but you don’t want the doctor that has the just-passing grade, and code is just passing. There’s quite a bit, there’s quite a few things out there they could do it way above code and make your home really awesome, but because people don’t ask for them or because they’re expensive, they just don’t happen.

BO: Wow. Okay, I have to jump in, ’cause I feel like we’re just scratching the surface on this whole thing. But, Ross, we gotta wrap up for today, or for now. Can you please plug your website again, plug MBPA again, and where can everybody find this great information that they probably wanna know?

RA: Yeah, so I think the best place is the MBPA, which is the Minnesota Building Performance Association, our non-profit, which is, that’s the best, it’s just a conglomerate of really good information from the Department of Energy, University of Minnesota, a lot of good building science resources. And then my company is The Energy Network Worldwide, and we do new home energy testing, we work with a lot of new construction builders, so that’s really our main go-to.

BO: Outstanding. Well, you’ve been listening to Structure Talk, a Structure Tech presentation. Ross, I can’t thank you enough. This is fantastic information. And thanks everybody for listening. We’ll catch you next time.