 All right. Well, welcome, everyone. My name is Roxy, and I'm the chair of the Sustainability Committee for AIC, and I'm here with Rachel, who's our vice chair, and Belly, who's our student member. And we're speaking today with Mark Nussbaum, who is a principal engineer at architectural consulting engineers, and Mark has expertise in sustainable systems, specifically for historic buildings, which is really awesome for us. And he is also a project manager and consultant on the NEH project with the Glesner House, where they are installing geothermal systems in that historic building in Chicago. We did part one of that series with Bill Tire, who is also working on the project. And so now we're going to speak with Mark, who has a little bit more technical or a lot more technical expertise in the area of specifically geothermal. So to get us started, Mark, can you just give us a little bit of background about, you know, your training and what made you interested specifically in sustainable systems for historic buildings? Sure. Yeah, go ahead. Yeah, it's kind of an unusual place to find yourself. First up, most engineering firms don't really like to climb into historic properties because it's hard work, it's time consuming, requires a lot of expertise, and usually the budgets just aren't there. There's a lot of times with not-for-profit organizations, and so they just can't afford high consultant fees. So, since I work for myself and I've started my firm with the intention of working in this field, I get a pick and choose the projects I work on, and I've been very fortunate to work on some really cool projects over the years. So, I had a background in my first job in this field. I was an engineer for the city and county of San Francisco, and I did a report for, this is back before the Loma Pre-Earthquake, but I did a report on the upgrades required for the historic Civic Center District, which is seven historic buildings built after the earthquake in 1906. And so that kind of pushed me in really quickly in the historic properties and the working on them and finding out how cool that is. And so then throughout the years I've had opportunities when I worked for other firms to do other historic-based projects and kind of developed that philosophy of trying to integrate modern systems in historic buildings without tearing the building apart as a driving concern. And that was a strongly resonant feeling with the architects that I contacted and ultimately have worked with many of, because I think a lot of engineers are reluctant to do something that's not going to produce the best optimal engineering results. And so I try to take the attitude I'll give you the best engineering solution I can with the minimal damage to the building as possible. And so by taking that approach and offer, I offer both approaches to the client. You know, I'll say, well, I can, I can tear the heck out of your building and get the system just perfect and they'll work great and we'll be very invasive. And if that's what you're looking for, the perfectly operating system, performing system, I can do that. Or I can do it this other way that does as little damage as possible and get you a perfectly adequate system that maybe doesn't achieve everything. And that's, they always take that second choice. And I remind them of that if we have a situation where the system doesn't do exactly what we had hoped it would or if it's, it's just not as optimal. Because you know, you can deliver air into a room from across the room, you know, where you have access to put a duck without compromising, or I can tear up the ceiling and get that air device out there by the outside wall, which will probably perform better. So we, we just, that's our focus is just to try to introduce systems, you know, and that revolves around spending a lot of time on the site, crawling every interstitial space that's available to me. I've been in more addicts and crawl spaces and tunnels and, and really cool spaces in these buildings. And have found rooms that they didn't know existed in ease, you know, large spaces and ease where I've been able to put equipment and, and, and effectively hide it from from not even taking the other precious space because I was able to hide it someplace they didn't even know they had. So, and then over the years I've, I've worked on getting. I started doing geothermal system, the ground source heat pump systems, before I opened my own firm, when I was down in the St. Louis market. And when I moved up here, it wasn't really viable here because of the utility rates were structured and efficiencies weren't as high as they are today. And, but I was, I was asked to put a proposal on a unique temple. Frankly, right. Design building in Oak Park here. And they specifically wanted to look at geothermal. So, and so I ended up getting that commission and in 2004. And then, you know, 11 years later, after the study and a bunch of other work we've done there we actually started the restoration process and completed that in 2017 so using geothermal so. But that reintroduction to geothermal or ground source heat pumps up in this up in this market. And, and so I started looking at that from various projects to see how it could be implemented. And again the technologies have changed a little bit the drilling techniques have changed a little bit to make it more possible on this tight urban sites that we have. That actually transitions brilliantly to my next question. That's so interesting I love the kind of like problem solving obviously we're, we're in the, you know, conservation and preservation field so we love to hear people who are willing to take on these, these projects and figure out how to do it without hurting the building. So that kind of, like I said leads me on to my second question so we're really, I mean, we spoke with Bell but we, none of us were engineers so we kind of didn't get too close to the technical aspects but I wondered if you could give us just a sort of brief. brief lay person's understanding of how geothermal works and, and why it is then appropriate to use for historic buildings. Okay. Well, I'm geothermal systems or grounds or I mean we'll calm, I call it's kind of an interchangeable terminology. Sometimes geothermal gets confused with the deep earth heat type of geothermal where we're using tapping into a hot source down on the ground. Do the proximity to magma, and we can either use steam generated from that or other things. This is not that. So, what I'm doing is I'm, I'm, I'm drilling into the ground. Anywhere from in this area we drill anywhere from 150 feet down to 500 feet vertically down into the ground. And then we separate those pipes, roughly 15 to 20 feet apart. And then we can, you know, then we put in as many pipes as we need. And we circulate a fluid through that. So it's all water mixture so it's freeze antifreeze. And we circulate that and then we circulate from that field into into a box, and that box is usually inside. And it has a compressor. And, and then depending on how it's being used it might have a fan and be like a furnace, only with the air conditioning part that sits outside and a traditional air conditioning system. And then there's a box and then there's a heat exchanger for the water loop. And so, we leveraged the work of the refrigerant. So, think of a refrigerator that sits in the room that's 70 degrees and somehow I produce, you know, zero degree freezer and 40 degree or 35 degree refrigerator temperatures, but it's sitting in a room of seven degrees and it's using the work of the refrigerant to do that. If I think of an air conditioning system. It's going to have an air conditioning mode, which is what air conditioning does inside it's blowing cold air out of the furnace box. I have a coil in there and then if I go outside to the outside box, it's blowing hot air. And because it's exchanging energy from inside the house it's moving it to the outside, and it can do that up to temperatures of 95 or 100 degrees with still keeping full capacity in the box with a heat pump. I have a coil in that refrigerant loop, which then switches the function of those two coils. And so, in the heating mode it blows cold air outside and blows hot air inside with a geosystem, instead of interacting with the air of an air source heat pump, in the air source cooling unit, I'm interacting with the ground loop, and that deeper temperature varies across the country depending on how far north you are in the Chicago area that's, if I take an average temperature that 500 foot loop in the ground, it's about 52 degrees. And so, instead of, and so we start to push put heat in the ground during air conditioning mode moving it from outside the building into the ground, and slowly start to elevate that temperature in the ground loop. When we go into heating mode, I start to extract that heat back out of the ground, because it's actually kind of like a storage battery. And then, and then, and then over the course of the winter, I bring the temperature down below that average temperature, the average temperature stays about the same it just cycles like a sine curve, it just cycles across the seasons. And because we can control that temperature swing by how much pipe we put in the ground, we can we can keep it at the optimum equipment efficiency range and so a geothermal heat pump system is the most efficient system so it's at the lowest operating costs of any of any system on the market. And so what makes that it does cost more because the ground loop that you got to put in the ground it costs a whole lot more than that box that sits outside in a conventional system. But it allows me to have full capacity year round out of the box, which I don't get in an air source heat pump, I don't have any exterior equipment that that pollutes the site with aesthetic or noise. And then, and then, if I configured correctly on the inside, a really important point on the system is that I can get simultaneous control of temperature humidity, which is ideal for historic projects where we're trying to dampen that dampen that dampen, you know, in historic properties usually the buildings aren't designed for air conditioning and controlling humidity. So I have to do that very carefully, but I can, I can, I can usually take chop off the extremes, highs and low levels, I get very stable temperature control. And then I can, I can, I can achieve a really good acceptable relative humidity control, or at least improve it dramatically, which of course comes to what you guys like which is stable within plus or part emojis. I'm like, yes, please. Yeah, so so that's, I once said on a, I was on a project for the National Trust, and a project got Washington DC, where they were they, they set all the conservators around the table all the different types of conservators, you know, so building conservators the paint and, and paper and, and paintings and, and all these different, you know, cloth cloth and, and they sat around the table and told me all the things that they, that they like to restrict and how do you like to control the environment. And then they turned to me at the end of it and said, okay, fix it. Give us a solution. So you've been the worst of it then. Because of course we can't get, we can't get everything perfect, you know, you know, the buildings are the limitation of what we can do. So if the building can sustain higher winter humidity then we could add humidity improve it. Usually the summer is easier than the winter because we, we, it's easier to shave off humidity in the building in the summer than it is to add humidity in the winter. So it's easy to do, but you, you run the risk of introducing a problem in the building, much more risky in the winter time than it is in the summer. Well, again, this is a good transition. Unfortunately, Rachel said her internet was going in and out so I'm going to ask her question. But hopefully she'll be back and can hear some more of your interesting feedback. So, we were, we were kind of interested in in how you make that transition I mean that seems like certainly the stable humidity is a huge, you know, benefit from our point of view as you will know. But what, when you're working with an older home and I guess it probably depends on, you know, when the building was built. But is there kind of a typical infrastructure that you would be converting from or particular infrastructures that work better to convert to geothermal. So if the museum has gas forced air or say, or I don't know, I mean, you know, more than what the options are, but can you talk us through that process a little bit. Yeah, if the building has currently has forced air, that's perfect. You do have to be a little careful. If it's a heating only system, and I want to introduce cooling, I have to be concerned about the duckwork having insulation. A lot of times residential properties don't have any insulation. So that's something you have to address. You either have to take the sheet metal off and get, get it insulated or, or replace it because if I put really cold air in there and the building is humid. It'll condense the outside and drip drip onto the objects of the building envelope which then can cause mold growth and all that stuff. But it's still usually that means there's space already encumbered with duckwork. And so I can usually get it in and then the equipment just a direct replacement that the equipment, you know, remove the furnace and put in a heat pump. So it's pretty straightforward. I can also make chilled water and hot water from a heat pump. So chill water. So a lot of systems, especially commercial systems, operate with a fan box with a water coil on it. It blows air across the coil. And you run chill water through the coil or hot water through the coil. And in our case we usually run, we have two coils, we have a chill water coil and a hot water coil and sequence. So again I can, so I can make chemical cooling generally removes the humidity from the building. And we just as a course of the, you know, so the air temperature gets brought down below the dew point of the air which causes the moisture to come out. And then and then. But the problem with that is, if it's a, if there's a high humidity level, and not a lot of cooling load in other words, it's maybe spring or fall. And so, or I don't have, it's designed for a large occupancy and they don't have anybody there. I can reach my cooling set point before I reach my relative humidity set point. So then having the coil set up as cooling first and heating second, I can run the cooling side to get down to temperature. When I satisfied my temperature set point I continue to cool, but then I reheat the air coming off the cooling coil back up to room neutral temperature. So I don't continue to cool the space so I can control that temperature, and then I can bring the humidity down. So in even one of those systems, and I can do that with the refrigerant side on the on the heat pump, if I have a forced air heat pump. I can do the same thing I use the warm water in the loop after it's gone through to circle back around and reheat the air when indeed it's called deep humidification mode. A lot of historic buildings don't have a forced air system. You know they have, they have radiators. And, and the, a cast iron radio that's running on steam, which is common is not directly exchangeable with a geosystem. So that's really in a steam boiler or steam boiler is going to give you about 220 degrees steam. It's about five pounds pressure and 212 is boiling point so he's a little higher than that. So the building is designed around steam heat. I actually may or may not be able to get enough heat out of that radiator with a with lower temperature water so you have to look at that. Sometimes you can because we improve the envelope we had insulation when the building was built 100 years ago, it probably didn't have any insulation or minimal insulation. They had leaky windows, you know, filtration air infiltration wise. So we have a lot of extra loads. And they usually over design the radiators because 100 years ago, they were going through the Spanish flu. And, and the health, health design of the day was to introduce lots of fresh air in the building. And, and so they oversized radiators. And so you could open the, you could bring in fresh air and it would rise out and be ventilated up the uproar. So they were dealing with the same exact issues today 100 plus years ago. And that's real common you get these mansions, they'll have floor radiators, box three years to sit at the basement level and open up to a cashier and grow on the floor. And then there's an outside air duct that goes off that box radio in the basement over to a window opening or a louver on the wall, and they bring in fresh air that way. And then they open the windows. So, so anyway, so you can, you can sometimes get by with a lower temperature but usually you can't. What would just heat pump water with no extra boost to it or anything. I can't get enough heat out of that. So I have to rely on a second stage of forced air. If I have it because if they want cooling I have to do forced air. So that's, you know, so I introduce a forced air system on top of a radiation system we usually like to keep three years in place, because they help drive moisture. They sit usually below the windows, and the window is the leaky spot from water infiltration, just by the nature of a big opening in the side of a wall. And so we usually that's where the radio is at. And we like to keep that drying, you know, so it doesn't matter if it's wet, it's fine. We, it should be designed to get wet, but it also be should be designed to dry out, because if it doesn't dry out, it rocks. So, so we, we like to keep the readers in place I do in my designs. And so sometimes we'll still keep natural gas boilers to produce hotter water if we feel like we need hotter water. But I'm working on a project right now. It's a frankly right house. And the owner would like to take it to net zero, which means I produce as much electricity inside as I use on site. And so that doesn't work with natural gas, because I don't produce any natural gas on site. And so, so we have to get rid of all the natural gas sources, and she's got cast on radiators. And so I'm using a two tier heat pump they make a heat pump the normal heat pump gives me about 120 degree water. And so I can put in a special heat pump with a different refrigerant that'll give me up to 160 degree water 160. And so, and so I can produce. I can produce hot enough water to make those radiators work without using gas heat. So, that is really neat. Did I answer your question. Yes, for sure. You're kind of off topic something. Well, I'm fascinated by all of this. So that's all good. So it sounds like there's some their particular systems, it sounds like the force air system is really the easiest. And then you have to kind of just, I imagine it's sort of a case by case basis how you very much. So yeah, I mean, yeah, you know, in a residential application, not historic. We usually, I mean, like I said, you want cooling. I'm going to have to insert duck work. And so a lot of times in a residential application, they don't, you know, even though they might like radiators, they're willing to get radiators, or, you know, it's not a not a big deal. But yeah, you, it's a force air system either either if it's already existing, or if they want cooling, we're going to add a force air system. It's the least expensive and simplest to control and, and because I also if I want to introduce unity in the space, usually I'm going to do that through the force air system, and then removing community through the force air system. And while there's other ways to do it, that's the simplest way to do it. And so, yeah, I think that's really good for people to know if they're thinking, you know, at my institution, this is something that would be feasible or my. I am smart building or that is the is the process I mean you've kind of already answered this but how extensive and it's sort of invasive is the process. Like you said it's a case by case basis but it sounds like you're able to kind of use some tricks to make it not too invasive, but are there kind of interesting examples of ways in which you can do that that you could share. So, let's just, let's just think about a typical two story house with an attic in a basement. That's about as easy as it gets for an installation because I can service the first floor in the basement from the basement usually it's utility space and so it's okay to have exposed duck worker. You know, you usually have more utilitarian uses called secondary or tertiary spaces in the historic places off tour. The attic gives me the same thing with a caveat. I want to see them insulate the roof deck. That's at the slope drawer for the flat roof I want to see the installation up in the roof rafters. So that my attic space is a semi conditioned space because the equipment we're going to put up there is going to perform better have a longer life and have less problems. It doesn't need to be a semi tempered space it doesn't need to be room temperature, but it shouldn't be, you know, zero degrees in the winter time and 120 degrees in the summertime it should be, you know, so you insulate up at that roof line. And then you take the installation out there's installation in the ceiling, which there often is, even in older buildings, you take that out so that that he could get up there, the cool. That's really straightforward than I'm, you know, I'm turning usually for girls from the basement level, and then ceiling girls from the level, you know, and you have to think through the process of against the house on tour. Usually, you know, we had that conversation with the, with the, with the client to say, you know, we can get third examples of forced air grills in the house. And it's got a particular pattern a lot of cast iron grills are very elaborate and stuff like that. We can recreate that in a custom grill. And so we keep that same basic pattern so it looks like it was maybe always there. If there was never forced air in the building or there aren't any examples of grills in the house that we can, we can buy off on. Then, then we would, we have to make the decision do we try to hide them hide the grills. So they're less obvious, or we just put in modern grills and and then interpret it as part of this is our modern system, you know, and and you don't try to hide that's a kind of a client decision and kind of a, again, there might be easy ways to hide it and it might be hard ways to hide it. So, so we kind of talk through that with the client. When you get into a three story house, where I've got a basement below first second third floor and then an attic. The second floor becomes a problem because I don't have utility space above or below it. I've got finished space above or below. So now, so now you have to start looking for opportunities to hide equipment on that floor. So a lot of old houses have decent closets. And so I can maybe put a small unit. It's easier to piping through the building without turning the building up than ductwork. And so I'll put a fan box in there and this is where it will often make a decision to go to a chilled hot water system versus a direct geo system, still serve by geothermal equipment but you know the add the complexity of the pipes and the because I've got spaces I don't want equipment in. I don't want geothermal equipment because there's a compressor in there and while it's fairly quiet, it's not as quiet as just a fan box. And so, so you'll put a fan box fan Chloe and there's what we call it up in the, in the usually at the ceiling on the closet. And then we'll create a grill, maybe on the sidewall, just above the door game, just above the trim. So it's linear like the trim, and maybe, you know, disappears a little bit. And then you turn the room and return into that space. So you start looking for those opportunities or other utility spaces on that floor. Sometimes, you know, you might have a setup where they're willing to drop the ceiling in the hallway, for instance, you know, you know, it's maybe a 10 foot hallway ceiling, or maybe even more sometimes, you know, have very generous hallways. And so you can, you can put equipment in, put duck work at the ceiling, drop it new ceiling below, keeping you moving the code molding or whatever it's elaborate. And then you go sidewall off, you go to side grills in the rooms off of that type of a system. So those are another method to use a fully ducted system if you've got a place to bring the duct up and hide the equipment. But yeah, the those types of spaces with that third floor finished third floor generally create a much more challenging, trying to figure out. It sounds like the biggest. Oh, sorry. I was going to say that I actually had projects where they didn't want to do that. So we condition the third form of condition the first floor, and let the second floor kind of it's semi condition is, it is condition there that find this way just not as effective. So, so you follow up. Yeah, yeah, so the, so the limitation is really that sort of hiding space for lack of a better word. Yes, kind of the biggest. Okay, that's really good to know. I have no idea. We've done projects where we've, you know, if they have radiators, and we can put a fan cool unit, a vertical fan cool unit that hides in, you know, if a radiator maybe with a radiator, a wooden grill in front of it or casing around it, we can actually put a piece of equipment to replace that heating cool unit, the self continued right there. So I'm just going to introduce more noise in the space because I've got now I've got a fan powered unit inside the room, just hidden by a wooden screen or something like that so tends to bring in a little more noise but that's, we do that as well we've done that as well. Belly I'll toss it over to you to ask a couple questions, because I think we've got through most of mine. Okay. So you've touched a little bit on a couple different projects that you've worked on, all of which sound fascinating. I was wondering if you could speak specifically to your work with the Glesner house. Sure. I've been involved with Glesner house for a long time, well before two or three executive directors before bill so bill tire. So done various projects there but we had done a, he was intrigued by the geothermal concept and they had us look at it do a feasibility study. And it came out that, you know, was a little more cost than what they could afford at the time. And then, and then he got a donation. And we were able to this back of 2015, I think 2014 2015 where I got a donation to do a partial system of the design the whole building, and they had, they had replaced, and I want to say it was done 70s or 80s they replaced the original system that was there. And I'm honestly not I think it was just a radiation based system. I'm not 100% sure that because it wasn't a lot of evidence and there were no drawings. But so but there was a four sear system that was in place there and it was. Most areas are just heated, no cooling, a couple rooms had cooling in them. And it wasn't a house museum I think when they did the project it was just offices, an event space. So anyway, we so we looked at areas that we could reuse the duck runs the duct equipment ducted equipment. And then, and then areas where we couldn't and then we designed a system and it consisted of, I want to say they had nine or 10 systems, or maybe even 11 systems now throughout the building. So we replaced that with a design with 10 system to replacing. And the equipment's located where the other equipment was generally. So we're just taking a box out put the box in. In most cases were providing new duck work because again it's not insulated. And we are trying to reuse all the existing floor and ceiling openings that we can. Because you know that way we're not making new openings through historic going. And then there was two spaces that the co-tiles for the garage, if you will, that space sits at one end of the building. And that had a air conditioning system because they use it for events. And, and then the second floor above that was an unfinished space that they were hoping to finish into a gallery type space. So, we designed for all the areas in the building, sized up a loop field that was based on four, 500 foot deep, Rygan pipes, which is a traditional geo system uses just a pipe that goes to the bottom of the hole and comes back up. This is a specialty system that when you have limited space you pay more for the product but you get more capacity on the loop field so it was worth it since the side yard there the courtyard is very limited in space. So we needed to get the well field in. So we designed the system and we bid it out, and they could afford one. We afford half the well field two holes, and then one system inside. And so we replaced that in like 2015. And that's been operating then Bill applied for the grant. And when he got it then we're going to, you know, we're massaging the plans to update them for current technologies and model numbers of equipment. And we're going to remove the heat pump from the unfinished space above the carriage house, because we're pretty confident we won't have the budget for that. And then we're going to add the additional well field. And then, and then slowly sequence and replacing the systems over the course of the grant type table. And that's, it's getting tricky because we were, we're trying to get the drilling done, we were trying to get the joint done this fall. So you could get his grass sod and his side installed before the winter. I'm sure we mentioned that. But we've run into an obstacle with the city of Chicago where they require what's called a board of underground review which if you go deeper than 10 feet below ground. You have to go through this air, this review process with all these agencies around the city to make sure that we're not getting into any of the underground infrastructure that supports the city like subways and things like that. Now, ironically, when we drilled the well field four years ago, or five years ago, we didn't have to go through that review so I don't know something changed or whatever but we're, we're going through it right now. And so we still think we can get the drilling and the drillers said he can drill down to about when it's 25 degrees Fahrenheit. Below that it gets to be a problem because we're circulating water. It's really cold for his crew. So, we hopefully will get be able to drill over the winter so that we can start installing systems. After the eating season. So, yeah, that would be that would be great I was fascinated when we spoke to Bill, or I guess, just really impressed by how you all have been able to make this work within such a small system I guess such a small footprint. That was that was really wonderful. And we're hoping that this series will inspire other institutions to also adapt to your thermal. But we do understand that a lot of institutions see making the change from gas to a more sustainable energy source as financially not feasible and you've spoken to some of those challenges. And what advice would you give to those who are thinking about both short term and long term financial benefits and restraints to this change. Sure. Geothermal system will pay for itself and we'll just say that I mean it's, it's, it's kind of all based on on a lot of factors and we run an energy model for the building so we, we look at, you know, how the envelope performs and then how much energy it takes to operate the systems against the system in a geothermal system. We, that's usually one of the things we, when you got a client that's on the fence about going conventional versus geothermal. Almost always the geothermal system operates with less energy, you just say it that way there's, but the cost of energy is different depending on its gas or electric. Sometimes just because of nature of the utility rates, it might, you know, be a 15 or 20 year payback efficiency, you know, less operating costs, but to cover the differential and cost between, between the conventional and geothermal system. It might take 15 or 20 years or sometimes longer to pay it back and usually if you're doing more than 10 years, people get nervous because they, you know, the equipment life is about 20 years. You know, it's, it's hard to make pull a trigger to when you're going to, you're going to about the time you need to replace the equipment you're finally paying back. But most equipment lasts for 20 years so your conventional systems probably being replaced at about that same time cycle, maybe less because in the case of Geo, all my equipment's indoors where they're conditioning systems are sitting with equipment outside and thus fire equipment has heat exchangers in it that sometimes will burn up the heat exchanger and have to be replaced sooner. So, so my general comment is, if you can afford the long horizon of payback, and sometimes it's less than 10 years, just depending on the area of the country, and the type of systems you're comparing against but if you can afford the horizon, and you can come up with the general cost up front, which there are grants to help with often and state rebates or utility rebates and things like that. You can usually get better control with less operating costs and long term savings if you go with the geothermal. It's easier to configure a geothermal system to provide that simultaneous temperature humidity control, for instance, much harder to do with a conventional system because I don't, you know, I, in one case I have a box that's designed to do both and so I can move things around to make that work. If I, if I go with if I want to do it in a conventional system, I'm kind of often forced into the chill water hot water model which costs more to install. In some cases geothermal is actually less costly than in the alternative system that will give you will give you the same performance and so if that's the case then it's a zero year payback and you know I don't usually have a trouble selling that project. But there are ways to do it and and the challenges with historic properties is they usually struggle, they can often get the money to do the project through grants and people who are really interested in sustainable practices will fund a project like that. But there's maintenance involved and and maintainability, and it's usually a little more complex control wise than a conventional system or can be. And so, and so you have to be prepared to for the ongoing cost of operation in addition to. I will say that again geothermal should be less expensive to maintain because it actually has fewer components and doesn't have that outside piece and stuff like that. And the geothermal loop itself is kind of a forever piece of equipment so once you've installed it, you don't have to replace it when the equipment fails you just replace the equipment. So, once the geothermal, I mean the piping has a 50 plus year warranty, of course, doesn't help you but it's 500 foot in the ground years, you know they'll give you the piping that's not the expensive part. But we don't see a lot of system failures loop failures I mean that's there's, you know, a backhoe tears up a loop, but really not much else to normal operation because it looked to fail. The trickiest part of a project is getting it inserted into the building. And again, I have to do that with any system I'm going to put in. So if I'm going to put a conventional system in the dark work. I still have to insert it into the building and do it in a way that's and then always that always almost always costs more than than just a house somebody's house we're installing a system. So, what they have to look at is what is the best. What, what are they ultimately looking for as far as climate control and then and then and then they should do a study. We always recommend a front end study. We usually assess the systems are in place assess the feasibility of putting in a geothermal system do they have the land available to put the field in, do they have the place inside the equipment. And that's you know again we look at usually look at geothermal and a couple of different iterations of conventional systems, and then try to come up with recommendation on on on efficiency and long term operating costs we look at a 20 year life cycle. So we try to bring all the costs in there and then decide what the payback is so. But ultimately it's what are the goals of the institution and the organization and the people running the building. Again, if temperature and humidity control is involved. Your system is going to get more complicated. The least complicated system to do that is a geothermal heat pump with a with a four stair system with a standard heat pump installed geothermal heat pump, you know so as I introduce chill hot water as a source, which works good, and it's, and it works in either conventional or geo that that solution is going to be more complex controls are going to be harder. So the controls are always tricky part. We, we did a blank in here. Oh, we put in the geothermal system at unity temple, as I mentioned earlier, and, and that system. We was very costly to maintain, and the reason it was costly to maintain as I had, I had 20 area units in the building life, eight fan cool units. I had almost 20. I have 10 air handling units and I had a area or band called units, and each of those has be controlled on all that stuff and I was, I was questioned about it by the by the organization that funded the project, or helped us fund the project. And they were Christian why is your geothermal system so expensive to maintain is it is not it's it's it the parts of the system that are hard to maintain or expensive to maintain would be there in a conventional system or geothermal system it's not. The only thing that makes that a geothermal system is a loop field, instead of a cooling tower. And that cooling tower would be more to maintain more expensive to maintain than the loop which has no maintenance required. So, you just have to look at it holistically and sometimes it's hard to convince people. A lot of these old buildings aren't air conditioned. And so when I, I have to speculate I have to, I have to design in my head I have to design a conventional system that would do it, and a geothermal system would do it when I'm doing this modeling this energy modeling. And, and the, when they see the cost of operating the utility cost they go that does that's not right we didn't cost us anywhere near to operate a building like that. I'm going to air conditioned the building and, and if you do it convincing it's going to cost you more to operate than it does to do and that's the point of the survey is the study is to do that so it's, but you have to look holistically at it you have to look. And, and don't be scared off of the pricing, I mean it's, it certainly is going to be more cost to install a geothermal system but you will recover it if you're a long term ownership of the building, even better, you know, the hardest cells I have on geothermal systems are developers, because they want to turn around their, their money in a hurry so and they want to get their whatever they spent on it on the other side. And so it's it's very very hard, even with very quick paybacks they're not interested usually. But, you know, historic building owners, governmental agencies, churches people are going to own their property for a long long time. Homeowners. Those are absolutely perfect candidates for geothermal because it will it will pay itself back, and it stabilizes out that utility cost across the year. That's really good to know actually I think that's a really important thing for cultural institutions to mind. One thing that you mentioned that I would love to just get a little bit more clarity on I guess or just a little expand on a little bit, something that we conservators as I've mentioned love to talk about is temperature and humidity controls. And as you know folks who are concerned about sustainability in this realm one of the things that we've really pushed for is for a model of seasonal drift where we've, you know, as a as a profession have studied how these fluctuations impact objects and found that over time a slow drift is definitely, you know, preferable to sharp up and down. So I'm curious, obviously geothermal is much less you know much more energy efficient and much better for the world. But is there a sense that you can keep a tighter control is that what you're suggesting. Or is that not necessarily the case. Well it's, it's, it's not necessarily you can get very tight control you can get just as tight to control with a conventional system and you can with the geothermal system. It's usually easier to do with some geothermal systems because, again, that self contained unit with got the compressor and the fan and just blowing cold air or hot air can be configured so that it's, it's more or less automated you have a thermostat on the wall that has a relative humidity sensor in it. And it's as simple a system as you can get and almost always operates better than most and I can get, I can get pretty decent multi community control again it's that idea that not overcooling the space. Well I'm trying to bring community down that's the trick. And in order to do that, you know, if it's conventional system without that feature without the use of the coil placement, you know, chill coil first hot coil second. And when this temperature satisfies the system shuts down. And, and so it's just harder to do, and again I can do it show out what our system with geo, and I can do a, just a forced your system with self contained equipment with geo. And the comparison that on the, on the, on the, you know, it compares with residential site type systems in the sense of usually it's a gas fired furnace and, and then a coolant coil. And because of that configuration, I don't get that reheat function on the other side of the coolant coil coolant coil sits downstream of the heat of the gas heat exchanger. So I can't pre cool the air and then warm it back up with the gas fired heat exchanger that doesn't work so then I have to introduce another piece, either hot water coil or electric coil which costs a lot to operate. I have to introduce that piece downstream of the coolant coil. So it's just a little trickier. You can do it. Sometimes what we'll do is we'll, we will work on some 1840s. houses restoration in Nabu, Illinois. And, and we did geothermal but we had no place to put duck work and so we had to use what's called a refrigerant variable refrigerant flow system which is a fancy fancy box it's a box in the basement and refrigerant line sets run up to to you and sit in the attic. So I only have to find room for that refrigerant line set, but I can't get any reheat control on those. So I have to introduce reheat on the other side. And it's, it's a smaller system and humidification is trickier because it's usually a small ducted systems. So it's just gets harder. It's certainly doable. But, but, and then to really get really good control of that seasonal drift, then you really need a building automation system where I can put in different thresholds for, you know, because, because that because what what happens is I'm sure you know is that it's, we usually will have a lower humidity in the winter outside the space, because we can only achieve so much before the building starts to basically say I'm done. You know, we get conversation windows. If you're getting conversation windows you like to get a conversation inside the walls. And so you have to be really careful about. So there's usually a maximum humidity that's outside the range and historic building is often outside the range of what you'd like to see, but it's better than it would be if you didn't do anything. And then on the other side, it's pretty easy to get the humidity out again with the system concept. But, you know, you, a building automation system can do a little bit better job of adjusting that set point to what's reasonable at the various times of the year, whether it's winter, spring, summer, fall. But the simple thermostat does a pretty good job on the on the self contained heat. And, and we, again, we're trying to shave the peaks off that the high. I can get rocks out of temperature control, at least at the thermostat location so if it's if if I'm if I got a simple system and it's one box and one geo heat pump or furnace air conditioning, I can I can I can wear that thermostat that it's going to be within a half a degree of set point almost all the time outside that range. The relative humidity is extraordinarily challenge, because it's influenced by outside it's it's influenced dramatically by how much infiltration I have into the building. So an outside air, it comes in. And, and so one of the things we we we recommend is usually on historic properties we usually recommend. To create a temperature humidity campaign be introduced before you make an intervention, and then keep it going, and then, and then continue monitoring then after you've made your intervention. It gives you the ability to tweak your set points and things like that and gives you the documentation you might need to prove that you've improved the situation. And, and when we do that, we still see, you know, because it's still driven very much by outside conditions. So the less the better I can do about infiltration control arrow infiltration control. And if I can avoid having to bring in outside air into the system, then the better control I get. But it's interesting, I did a study a long term two year study, another NIH grant at Naper settlement in Naperville here in the Chicago area. And it's a cluster of historic buildings that have been brought to this estate site so the original buildings as beautiful brick mansion. And then they have all these, these, you know, things you typically find in the village, you know, that generally been existing buildings have been brought there sometimes replicas but so you got the lawyer's office is this brick house that you stand inside, and you can literally see to the outside through the clabbered site. It's that bad. And then we have a majoring house it's two stories. And it's, it's, it's pretty well put together, and but they're both about the same age. So we did it blower door tests on those so we try to figure out how how much infiltration we get. The house did pretty good, almost a modern standards acceptable which is not uncommon because the only place it's going to leak out is around the windows and doors. And the mace and that frame house was had about four or five times the recommended level of infiltration. And then we had two, two modern buildings in their campus that were designed to house artifacts. The systems were never really designed to house artifacts. And so the worst system we had in the entire complex with the warehouse designed for artifacts. The best system we had in the summer was the house that had so much infiltration, because the system was constantly on and so it was constantly removing humidity. And so I was, I was flatlined on the humidity, it had better performance less time out of range than any other building on the campus. In the wintertime, of course, it was just the opposite was this driest could be because I had all that air. So the recommendation was take it offline in the wintertime with the temperature drop to 40 degrees and do, you know, humid static control, which you let the temperature drop and the relative unity comes up. It comes within range and you just take it offline as far as tours go. So, so we weren't able to do minimal recommendation that required minimal intervention to the building and still get decent control when they needed it. So it's, again, it's that approach of sometimes some every building is unique and different, but you really have to look at it and you have to study it to spend time at the building. And you have to, you know, data is a powerful thing so before and after. Well, I love to end on a sort of energizing inspiration note. I know you're more of a like, you know, engineer type but I'm curious if you have any thoughts on just how you know how the like preservation and, and cultural institutions can can lead in sustainability is there sort of an area where you can really, yeah, innovate and I think as a, as an example to the general population, because let's face it, you know, the majority of housing stock in the, or building stock in the country is old. And it's maybe not 120 years old or 100 years old. Maybe it's only 50 or 60 years old but usually it's still built, like, you know, not well as far as insulation and current sustainability practices. So as an example to a community. It's, it can be very beneficial to show them how you can integrate modern systems into historic buildings without destroying the integrity of the building. And, and it can be done a way that's not offensive it can be done in a way that's maybe even aesthetically pleasing if you do it right. You know, very little aesthetic impact. You can improve, you know, a lot of these sides are gorgeous, you know, in the summertime people like to wander around the gardens that are there. And then I got to be convincing that they're making this horrible noise. And so you can get rid of all that. As an example, people can enjoy their outdoor spaces and still have conditioned indoor spaces and that's true whether you only give your deck or your patio out there, or whether your cultural institution where people enjoying the grounds. I think primarily as it because also you're, you're serving a public and you have an educational component to most of these historic properties. And, and so, so again as an example to you can be an example to the community of a way to be sustainable even in an old building and take the steps and the best projects I think are the ones that integrate that component, because it's not just putting in the system, but putting in the system correctly. Because if you do it wrong, you can do more on any good. So it's really important to do it correctly so you can be a cultural institutions or stroke properties can be a real community asset and demonstrating and educating the general population on what you can do. Super inspiring to me. I can do it on their budgets, the good stewards of their buildings and sustainable practices. That's the best example you could hope for. My gosh, well on that note, I feel my heart is warmed. I so appreciate you taking the time to speak with us this is absolutely mind blowing I like have to process and probably rewatch this just. Yeah, sure. If you got follow up questions please come has a date to reach out. It's important to me to help inform and educate. Because, you know, there's way more buildings and I could ever possibly work on out there and helping prevent mistakes being made, because you just got to find the right people to do it and there's people like that in most communities. I mean, not as many engineers but a lot of these contractors really know their stuff. And so, although you hit stroke buildings tend to be special so you're trying to make sure you do it right. Well we thank you very much for your commitment to this work because it's really great to have, you know, people like you as a resource so thanks again for speaking with us and I'm sure I'll let you know when this is up and everything. Yeah.