Building Literacy: Public Library Construction


November 13, 2020 Massachusetts Board of Library Commissioners Construction Team Season 3 Episode 2
Building Literacy: Public Library Construction
Show Notes Transcript

On this episode of Building Literacy: Public Library Construction, we delve into the ducts of HVAC systems. HVAC, as you may know, stands for heating, ventilation and air conditioning, and does include dehumidification as well. Reopening libraries during a pandemic has brought the topic of HVAC out from behind the walls and into the proverbial light. We have read the ASHRAE guidance materials and we don't fully understand them either, so we enlisted the help of two knowledgeable MEP engineers-MEP stands for mechanical, electrical and plumbing- who have worked on a number of libraries in the Commonwealth. Carlos DeSousa and Dominick Puniello from Garcia Galuska DeSousa. While there's more information in the episode, Carlos has graciously shared his answers to our initial questions in written form. And Dom has shared a spreadsheet for determining the amount of cubic feet of a room and therefore the appropriate size of a portable HEPA filter for that room. If you have follow-up questions, send them to, and we will try to include them in a follow up podcast with Carlos and Dom early next year.

Andrea Bunker  0:00 
Welcome to Building Literacy: Public Library Construction, a podcast for librarians, trustees, and local officials who are exploring or undertaking a renovation expansion or new construction project for their library. My name is Andrea Bunker.

Lauren Stara  0:15 
And my name is Lauren Stara. And we are the library building specialists who administer the Massachusetts Public Library Construction Program, a multi-million dollar grant program run by the Massachusetts Board of Library Commissioners, which is the state agency for libraries.

Andrea Bunker  0:34 
While this podcast is Massachusetts-focused, stakeholders in library building projects everywhere may find helpful information within these episodes. From fundraising and advocacy campaigns, to sustainability and resilience, to the planning, design and construction process, there is something for everyone. If there is a public library building project topic we have not covered but that is of interest to you, please email me at

Lauren Stara  1:01 
Or me at

Andrea Bunker  1:05 
On this episode of Building Literacy: Public Library Construction, we delve into the ducts of HVAC systems. HVAC, as you may know, stands for heating, ventilation and air conditioning, and does include dehumidification as well. Reopening libraries during a pandemic has brought the topic of HVAC out from behind the walls and into the proverbial light. We have read the ASHRAE guidance materials and we don't fully understand them either, so we enlisted the help of two knowledgeable MEP engineers-MEP stands for mechanical, electrical and plumbing- who have worked on a number of libraries in the Commonwealth. Carlos DeSousa and Dominick Puniello from Garcia Galuska DeSousa. While there's more information in the episode, Carlos has graciously shared his answers to our initial questions in written form.

And Dom has shared a spreadsheet for determining the amount of cubic feet of a room and therefore the appropriate size of a portable HEPA filter for that room.

And both of these documents are listed in the description notes and at the end of the transcript. If you have follow-up questions, send them to, and we will try to include them in a follow up podcast with Carlos and Dom early next year. All right, let's dive right in.

Carlos DeSousa  2:18  
My name is Carlos DeSousa. I'm a principal and president of Garcia Galuska DeSousa, we're MEP consulting engineers. We've been working on COVID sequences for several towns and cities. Hopefully, you'll get a lot out of this podcast.

Dominick Puniello  2:33  
Hello, my name is Dominick Puniello, principal at Garcia Galuska DeSousa as well. I lead the HVAC department and look forward to providing information regarding covid mitigation on HVAC systems.

Andrea Bunker  2:49  
So we wanted to do this podcast because we are receiving a lot of questions from our librarians and library directors and trustees about their HVAC systems during a pandemic and how they can best upgrade or make modifications so that they can have the cleanest, freshest air. And our libraries really run the gamut, so you have national historic landmarks that haven't really been touched from the early 1900s, all the way up to new builds. So each one is really different. So for instance, we have a smaller rural library that had no ventilation system and mini split heat pumps. And for a situation like that, where you're really starting with bare bones, and a building that might not be as flexible as a newer building in terms of being able to put in ductwork and all of that, what would you recommend for a library like that?

Carlos DeSousa  3:43  
This is really not an uncommon situation. That actually happens not just in libraries but in school buildings as well where there is not a mechanical system. So what's used is operable windows and installation of portable HEPA filters. So we use an air purifying system. That's about the only solution that you can do without installing a mechanical ventilation system.

Andrea Bunker  4:06  
One of our colleagues actually shared with us this hack where they took a box fan and put a filter on it. 

Carlos DeSousa  4:14  

Andrea Bunker  4:15  
Is that something that would be okay to use? Or should you really be buying something that is a portable air filtration unit?

Carlos DeSousa  4:23  
We actually recommended that be used in older buildings. And we recommended that two air changes per hour be provided through that ventilation system in addition to installing the HEPA filter. But the box fan is a good idea. So when you install the box fan, you should make sure that you're at opposite ends of the room so you have the most air circulation possible.

Dominick Puniello  4:46  
However, I don't believe we would recommend just using a box fan, but use it as a supplemental means with a true certified HEPA filter.

Lauren Stara  4:58  
So just to clarify you're saying that a box fan or something equivalent could be used just to create air circulation in the space. And then a separate filtration unit would be used to remove the virus particles from the air.

Carlos DeSousa  5:14  
Yes, yes, because what happens is if you're just using operable windows, which is acceptable by code for fresh air, it does not mean that you're actually getting that fresh air inside that room, well into the room. So that box fan just gives you that air movement. So it's sucking outside air in and discharging it. You also have to be careful not to obviously over-cool the room in the wintertime.

Lauren Stara  5:36  
So would ceiling fans provide something of a similar benefit then?

Carlos DeSousa  5:42  
No, the ceiling fan would just recirculate the air. So it's not the same benefit. But the box fan does, it's connected to the window. So it's drawing air from another window, and then taking that same air and going to the outside. So the make-up air comes in from the window and is exhausted to the outside. So a ceiling fan is going to circulate the air to move it within the space.

Andrea Bunker  6:06  
And we don't want that because of the fact that you could be spreading virus more throughout the space, if you're not having it be a supply and return, right?

Carlos DeSousa  6:17  
Yes, that is why we're recommending the portable HEPA filter in addition to the box fan.

Lauren Stara  6:22  
I'm sorry, are you saying the box fan would be in the window or in front of the window, or?

Carlos DeSousa  6:27  
It would be in the room discharging out through the window? 

Lauren Stara  6:31  
Out the window.

Carlos DeSousa  6:32  
Yes, out the window. So you're drawing in from one window

Lauren Stara  6:36  
So it's an exhaust.

Carlos DeSousa  6:36  
And on the opposite side of the room, you're discharging through another window. If you bring in as an example, 100 CFM of air, you're discharging that hundred CFM of air because the room is always full of air.

Andrea Bunker  6:48  
So when you're thinking about this...My father was actually an HVAC estimator, and we were talking about this the other day. And he was saying how if you have a row of people, and you're moving that air, the supply and return, through that row of people- say it's like a computer lab type setup, and you have rows with chairs, like a classroom- and you're moving that air from one part of the room to the other, you have the HEPA filter in there. Where would you put the HEPA filter so that you wouldn't be moving viral load on to those other rows of people, because I'm thinking about the window placement in libraries, especially in this one library that I'm not even sure that they have operable windows in that library that we were thinking of.

Lauren Stara  7:33  
There are no windows. There are two doors. That's it.

Andrea Bunker  7:36  
So they might have to use the doors to be able to do that. But the fact of the matter is is that it's one room for a library. They're moving all that air across that room. So would the HEPA filter just be capturing all of that, the portable HEPA filter? 

Carlos DeSousa  7:52  

Andrea Bunker  7:53  
Okay, so you wouldn't have to worry about the airflow.

Carlos DeSousa  7:56  
No, and the actual HEPA the filter itself, there should be instructions on it so that depending on the room configuration, it gets put in, you know, either at one end or one corner. So it blows through an area. So there are area limitations. So we'd want to make sure that you size it for two air changes per hour.

Dominick Puniello  8:14  
So a larger space may need multiple portable HEPA filters to get sufficient air movement and filtration.

Carlos DeSousa  8:22  
Correct. But it's really done on a per square foot type basis.

Andrea Bunker  8:26  
So as we're moving into winter, then, and we're in our climate, which is the Northeast, we have the issue of what you were saying before, Carlos, that you don't want to over-cool your building, right? So that you don't want to be changing the comfort level, necessarily in the building for people to be inside of it. But you want to be making sure that you do have ventilation. So you did say that you should be opening those windows for increased outdoor air ventilation. But what considerations and factors during different seasons should librarians be taking into account when they're making these decisions?

Carlos DeSousa  9:06  
Well, that's a very good question. So in the wintertime, obviously, it's just the cold that we worry about. And usually along the outside of the building, there's either you know, some type of steam radiator baseboard radiation to overcome that chill from the window. So that just needs to be on all the time. So when you actually bring fresh air into a building, there's very little difference of just having a window open versus an air handling unit that's bringing in that fresh air and then treats it. We're basically doing the same thing at the window. So in the wintertime, that's what you need to make sure that you have enough capacity in your heating system to overcome that open window so that you don't freeze the space. But in the cooling season, it's a little different because if you have air conditioning in your building and you bring in humid air, then you may have a problem with condensation. Once you have condensation, especially on older buildings, you have to be careful of mold.

Andrea Bunker  10:00  
Also the fact that we're dealing with libraries where paper is throughout. So if you introduce humidity into the collections, there could also be ramifications there for the materials that the library offers.

Carlos DeSousa  10:14  

Lauren Stara  10:15  
But doesn't air conditioning, by definition, have fresh air coming in via the system? I mean, do you have to have the windows open as well?

Carlos DeSousa  10:25  
No, you don't. If you have an air conditioning system, and you don't open the windows, then that's exactly how you should operate it. You should operate it so that you have the most amount of ventilation possible so that if it's a re-circulated air type air handler, and you can isolate it, so it's 100% outside air, and can still maintain the temperature in the space, that would be ideal. But that's why you do it at the air handler, because that's where the condensation occurs on the cooling coil.

Dominick Puniello  10:51  
Air conditioning and ventilation aren't necessarily the same thing. You could add the example that was given before about the mini split system. If you just had operable windows, that's your ventilation system. And the VRF mini split is your air conditioning system. So the two have to be considered together. And regarding Andrea's question earlier, or statement about concerns for humidity in the summertime with collections, there's also concern in the wintertime with low humidity conditions. So increased outdoor air, when it's dry and cold, could present low humidity conditions, which have to be considered as well.

Lauren Stara  11:36  
Do I understand it correctly, that in terms of humidity within reasonable limits, the greatest damage is done, rather than what the actual level is, it's the range? In other words, if it goes way down and way up and way down and way up, that's more damaging than keeping it level at a certain place.

Dominick Puniello  11:58  
That's our understanding as well. When a material goes through extreme humidity conditions, that's when damage could likely occur. The ranges that are typically recommended would be to try to keep within the wintertime 25% and in the summertime, no higher than 60% in terms of thermal comfort. There have been some studies on the CDC recommending higher wintertime relative humidity levels up to 40% due to the covid 19 replication occurring higher at humidity levels that are lower. So again, that presents another challenge to make sure we don't have very low humidity levels within the space. 

Carlos DeSousa  12:43  
So one thing when you talk about humidity you have to look at, it's not just humidity, it's humidity and temperature. So humidity at 60% or 70%, when it's 40 degrees is different than humidity when it's 60% or 70% at 80 or 90 degrees, or even 70 degrees for that matter. So there are two things that you look at: one is the occupant comfort, for humidity and temperature and then you look at the product stability. Well as an example, hardwood floors, if you don't maintain a temperature and humidity for a period of time, even on new floors, what you should do is take the product and you put it into that space, let it stay there for a few days before you actually install it just so it stabilizes to its environment.

Andrea Bunker  13:26  
And I think with materials, our preservation specialist has mentioned that it takes five hours for a material to acclimate to its surroundings. And we do have libraries where they don't have insulated rooms where they have materials. And so you're having that temperature fluctuation occurring with the nighttime temperatures and then the daytime temperatures. But they are not being as strict anymore with materials in terms of temperature. They're changing that and becoming a little bit more flexible with it.

Carlos DeSousa  14:00  
So in the winter time when the humidity levels really drop, and you can have the humidity levels down to 15% rH something like that. It's just very, very dry. So one of the systems I think that you'll be looking at in the future is actually doing some type of humidity control in the winter, so you're somewhere around that 40% rH. So it's just not as dry, 40,45%.

Andrea Bunker  14:24  
So, is that something that is difficult to achieve with current systems, that humidity control in the winter?

Carlos DeSousa  14:30  
Yeah, well, it's just costly because what you have to do is you have to put moisture into the air. So you either do that through steam or through some ultrasonic process. I don't know, Dom, maybe you can talk about... I know we've done it on other library projects where we definitely do the collections that are either historic type collections or even on new projects where we've used ultrasonic type filtration.

Dominick Puniello  14:53  
Yes, not only there's a high cost of the first installation costs, but the operating costs could be very high. So in the past, and it's still used, a steam generated through an electric humidifier is an option. But as Carlos mentioned, ultrasonic type humidifiers, which use ultrasonic wave lengths

Carlos DeSousa  15:17  
to formulate droplets into the air 

Dominick Puniello  15:19  
Yeah, to energize the water in order to promote water droplets entering the space.

Carlos DeSousa  15:27  
It actually makes the water vibrate. 

Dominick Puniello  15:28  

Carlos DeSousa  15:29  
And then the water becomes airborne. And that's how you have moisture into the stream, you're adding mositure...

Dominick Puniello  15:33  
So it's a much more energy efficient means to provide humidification. They can be done with space type ultrasonic humidifiers or incorporated into air handling equipment, if there's enough room and duct run within the system.

Andrea Bunker  15:50  
And is it that the humidity slows the virus from being able to go throughout the space? Is that what the thought is with the humidity component to it?

Dominick Puniello  16:01  
The CDC papers that have been presented indicate slower growth and regeneration of the COVID-19 virus between 40 and 60% rH levels at thermal comfort temperatures between 70 and 75 degrees. So as Carlos mentioned it's temperature and humidity. And what they found is between 40 and 60% rH and 70 to 75 degrees, those are the ideal temperatures that slow the virus growth.

Andrea Bunker  16:37  
So it's the replication of the virus, the viral load increasing in the space.

Dominick Puniello  16:42  
Correct. It won't eliminate it, but it will slow the growth.

Andrea Bunker  16:47  
And therefore the hope is that whatever filtration system you have can therefore then handle the amount of viral load that might be being produced. That it's not being produced rapidly in the space and then creating more concentrated...

Dominick Puniello  17:00  
Yes, that along with good cleaning of the space.

Lauren Stara  17:05  
You mean surfaces or?

Dominick Puniello  17:08  
Yes, yes, the HVAC distribution, while it's been shown that there's a chance that the COVID-19 virus is airborne and could distribute through HVAC systems, there's not definitive testing to indicate that. There's a likelihood. However, there has been shown that the virus lives on surfaces. So through coughing and sneezing, one's not using a mask, PPE, that would likely fall to a surface because those droplets are heavier and not get airborne. So there's both aspects that need to be considered.

Carlos DeSousa  17:49  
Right, that falls on the cleaning and disinfection.

Andrea Bunker  17:52  
And IMLS has done several studies on different surfaces to see how long the virus lives on different library materials. Right now, we're awaiting the results of their testing on furniture, different types of materials there, and surfaces. So that will be interesting when that comes out. But some of their tests, it will say, you know, we tested for six days- this is through the realm project- and you could still see viral load on some of these surfaces. But we're not sure what the level of viral load is that is on the surfaces, whether or not it's something that could result in contracting covid. They're doing it in isolation, they're looking at these different scenarios. 

Lauren Stara  18:35  
And the biggest problem is that nobody knows yet how much virus produces the disease. That's the big disconnect. We can measure stuff all day long, but they still don't know the mechanism for what causes some people to get sick and others to not get sick or not have symptoms. 

Andrea Bunker  18:55  
Although now they're saying that there's one stream that seems to be more contagious than others. In Texas, they've shown some evidence of that, which is a little bit scary to see as these strains develop. Before we were talking about filtration, and what we've heard in a lot of the webinars we've gone to and when talking to different architects about what they're spec'ing they're looking at MERV 13 or higher filters, but what should libraries look for in terms of MERV 13 filters? What are the ramifications of that that they should think about as well? But then the other component to this is because we heard something on a federal facilities webinar the other day, is that the rush to create LEED compliant MERV 13 filters resulted in filters that lose their electrostatic properties over time, and therefore operate the same as a MERV 8 filter. So what should librarians and library directors and trustees be looking for in terms of filtration, that would be what is deemed to be adequate during this pandemic? 

Carlos DeSousa  20:02  
Well, I think one of the things you need to do is make sure that the maintenance procedures on the filters are done. There's an ASHRAE standard, it's the ASHRAE, standard 180. Year 2018 is the one that we follow. And there are two tables in there, five dash one and five dash two. 

And in those tables, there's a bunch of various maintenance type requirements for air distribution systems, coils, equipment, and so forth. So for a filter, they recommend that you inspect it, not necessarily change it, but inspect it quarterly, right. So, you know, every three months, you should be looking at that filter to make sure that it's working and that one, it's not plugged. A plugged filter will have the same situation happen, where you lose that electrostatic charge on the filter, but you can lose that, you could lose it within just several weeks, so it needs to be checked regularly. That's how you would achieve that. As far as using a MERV 13 and just go to a MERV 8, because you'll end up there anyway, I think the MERV 13, you start at a much higher particulate filtration than a MERV 8. So I wouldn't have to say that I would agree with LEED with using a MERV 13 or higher.

Dominick Puniello  21:13  
I also think it's important when purchasing the filters make sure that the manufacturer is a industry recognized filter manufacturer. There is a jump to the market by some manufacturers that might not have done the certified testing that other reputable filter manufacturers have. So when purchasing filters, it should be recommended that the certification of that filter is reviewed. There are ASHRAE tests. ASHRAE doesn't certify. But ASHRAE does provide testing procedures and criteria that a lot of manufacturers reputable manufacturers will have tested by independent labs, such as ASTM.

Carlos DeSousa  21:59  
Yeah, I would also recommend that a service company actually be hired by the library. They work on a schedule. So if you hire a service company, the work will get done. Now, you'd obviously need to oversee that. But by doing that, I think it will help filter replacements and having the system work more efficiently. Plugged filter, also, you're bringing in less outside air as an example. So it's more than just a filter. And you need to make sure it's clean. If it's plugged, you don't have as much air going through it.

Andrea Bunker  22:29  
We were in a webinar the other day. And they said that a new filter isn't necessarily better than a filter that's been running already. Can you speak to that? You said before that you don't necessarily want to change them?

Carlos DeSousa  22:41  
Yes, what they're claiming is that as you plug the filter, it actually will capture more particles, because less is going through that filter. But the issue I have with that is that you're also reducing the amount of fresh air that's going through that filter. And the amount of air changes that are being provided. As you create a plugged filter, what's called static pressure in the system builds up, which means that the fans need to work that much more. And of course, the fan doesn't know how much it produces, it turns on and it is what it is. As an example, a fan doesn't know that it produces, you know, as an example, 100 CFM, at a quarter horsepower, as an example. It doesn't know that. So it's based on the static pressure that you design to. If you increase that static pressure, but by their analysis, if you leave a plugged filter in and never change it, that would be ideal in that scenario. And that's just not the case.

Dominick Puniello  23:33  
Means to overcome that, but that would require additional controls that would ramp up a fan by example, like a VFD, where the speed is increased to overcome that additional filter loading. But if a system doesn't have that, as Carlos indicated, the amount of airflow is just going to be reduced.

Carlos DeSousa  23:54  
And you're using more energy as well.

Dominick Puniello  23:56  

Lauren Stara  23:57  
Can you speak to a situation that a lot of our smaller libraries find themselves in and that's that fans in their HVAC systems are not powerful enough to handle a MERV 13 filter? What would you recommend for them? Is there something else they can do? Or do they have to bite the bullet and install a more powerful fan? And can you also speak to the importance of installing these filters correctly?

Dominick Puniello  24:25  
For libraries that don't have air handling equipment that cannot handle higher efficiency filters such as MERV 13, our recommendation would be to supplement with portable HEPA filters within the space.  It's very important to provide filters that are compatible with the currently installed HVAC system because if higher efficiency filters are installed, where the equipment is not designed to overcome the pressure drop of those higher efficiency filters, airflow could be reduced. Air flow reduction could not possibly only cause reduced air flow, but more major problems such as freezing of air handling coils or freeze ups of air conditioning coils within the system.

Carlos DeSousa  25:17  
Yeah, also the way equipment is designed, it's designed for a certain amount of CFM at a certain amount of static pressure. Just simply replacing a fan on a piece of equipment does not necessarily mean you're going to get the right CFM out. It's designed for specific CFM at a certain static pressure.

Andrea Bunker  25:35  
And when you're talking about the portable HEPA filters, are they all similar? Are there ones that library should be looking at over others?

Carlos DeSousa  25:43  
Dom, you should answer this one. You just did a very good analysis over at a very small building. It's a college prep building in Boston, about 20,000 square feet similar to very small libraries and they have a steam system. You may want to just go through what you did for that analysis, Dom.

Dominick Puniello  26:00  
So it's very important that you look for certification of the HEP and make sure that it's truly a HEPA filter, some manufacturers will claim HEPA, but just use that word and not provide the backup. So it'd be important first to make sure that it's truly a certified HEPA filter. And that would be manufacturers would have test data available that can be requested. Secondly, what you see on the market, a lot of times is just manufacturers  indicating a HIPAA filter is good for up to 500 square feet, up to 1000 square feet. However, as Carlos mentioned, it's really about air changes per hour. And that could change from space to space due to different ceiling heights of different buildings and building areas. So you really got to look at the air changes and make sure that the HEPAfilter is sized for those air changes. So in order to do so you've got to get the CFM the cubic feet per minute rating, of those type of filters and not just rely on the manufacturer's suggestion it's good for a certain size room. Once you have the CFM ratings and can determine the room volume, then you could do an air change per hour calculation to make sure that that HEPA filter is properly sized for the space. That's the exercise we went through for the project Carlos mentioned.

Carlos DeSousa  27:33  
We actually made an Excel spreadsheet for that. So that you only have to put in the room parameters in that spreadsheet figures out everything else, and we have it set up so the user can actually do the input, you don't need a consultant to do that. We can share what that spreadsheet is, so that if you put it on your podcast, you'd be able to see the link. It's a fairly simple spreadsheet, we try to make it as simple as possible.

Andrea Bunker  27:59  
Thank you. So if you're listening to this, if you look in the notes or the transcription, you'll see that link to that particular spreadsheet. Let's shift a little bit to other methods of mitigating viral load in your HVAC system. So I'm wondering if we can start off with the germicidal UV light, if you could explain that in as simple terms as possible. And whether or not you would recommend to HVAC systems to incorporate that technology moving forward. And is there a way for existing h vac systems to incorporate that particular germicidal UV light?

Carlos DeSousa  28:36  
I can explain the UVC light, and then Dominick can talk about where you would be able to install these systems. But UVC, that's ultraviolet light and the C is the spectrum of light, you know, we see light that's in the visible range of frequencies in UV we cannot see, but it's a damaging light. It's been used for a long time, it is proven to kill virus and disinfect. It's used mostly in filtration systems such as wastewater systems. Most of the wastewater pump stations have ultraviolet lighting for disinfection. We use it even in rainwater capturing filtration systems. We recently did this at the King Open School in Cambridge, Mass. where we collect rainwater from the roof, and then we store it in tanks and then before we use it to flush toilets, we disinfect the water and that's all done through UVC. So UVC essentially is fluorescent tubes, and it can be installed in an air handling unit or it can be installed in ductwork and Dom will talk about that a little bit more. But the virus kill rate is that 99.99%, and I suspect it's that because you can't say 100% legally, so it's stuck to this 99.99%. The one thing that I think will be coming up this to date, these are fluorescent tubes, which require cleaning quarterly and then replacement every year, so you have the same intensity of light. If you lose the intensity obviously becomes an effective. I do see a future product. And I think it's already being used at the local level, or the point of use level, which is an LED version of it, once you have an LED version of it, then what that would mean is that the life expectancy goes from, you know, 1000 hours to about 8000 or more, and then you only have to worry about the cleaning of it. So I do believe there will be a new technology coming, which will be UVC but LED. And Dominick, if you can talk about where you would install the UVC.

Dominick Puniello  30:34  
Yeah, so in terms of HVAC equipment and UVC technology integration, really, I would say four different types or options. One would be within the air handling unit itself. If the air handling unit has sufficient room to accommodate the UVC emitter and bulbs, it's often a good place for them, because it's hopefully somewhere ready to be serviced. It also has another benefit of keeping the internal components such as a cooling coil if it's installed via the cooling coil, keeping that clean and disinfected, which could actually also improve the efficiency of the system. However, there's often not enough space within the air handling units. And then that may lead to consideration to install the UVC within the ductwork of the HVAC distribution system. Another good option, however, you just really have to make sure there's sufficient room for access to properly service the UVC. The other two options are within the space. So there's terminal type units with UVC that can be installed. However, these should be installed high within the space, just so that UVC is not a factor in terms of occupant health and safety. So they would have to be high within the space. These units have a recirculating fan. So they would disinfect the air through recirculation and UVC disinfect it. And then the last option that we're seeing is going back to the conversation about ceiling type paddle destratification fans. There's a number of manufacturers that are now incorporating UVC within those types of fans. So where we said just straight stratification fans might be problematic in terms of spreading the virus, by incorporating this technology within the stratification fan could actually help to kill the virus. So those are the four options that we see most readily available in terms of incorporating into HVAC systems.

Andrea Bunker  32:54  
And when you say stratification fan, you mean a ceiling fan?

Dominick Puniello  32:57  
A ceiling paddle fan, correct.

Carlos DeSousa  33:00  
Yes. So UVC, you don't want to see it because it's still harmful. So when the room is occupied, you don't want people to be able to look at it or it's exposed to people.

Lauren Stara  33:09  
So you said you can have it in the space if it's high in the space or on a ceiling fan. But does that mean that you turn it off when it's occupied, and it's on when it's not occupied, or how does that work?

Carlos DeSousa  33:20  
The UVC light would be concealed. When Dominick talks about having it in the room, it's actually you know, as an example would be after a VAV box either in duct work, or it would be in the room in a register that you can't see. But all the lights contained within the compartment that it's in.

Dominick Puniello  33:37  
It would be certified, constructed units, certainly not a hack or a make shift ad of a UV to a fan. But these would have to be tested and certified. And that's one of the good things about the UVC technology. It has been around for over 30 years. There is a ASHRAE standard for UVC testing requirements where some of these other technologies don't have that.

Lauren Stara  34:05  
I just want to talk about terminology for a minute because we hear a lot about UVG or ultraviolet germicidal irradiation, but that is actually using the UVC. spectrum of light.

Carlos DeSousa  34:19  

Lauren Stara  34:19  
Is that correct? So we're talking about the same

Carlos DeSousa  34:21  
We're talking about the same thing. Yeah, so the C is just that the light spectrum is what that means, but the normal version of it is that UVGI that you list germicidal, UV germicidal. Now one thing I should mention is that the UVC technology is expensive to purchase and expensive to maintain.

Andrea Bunker  34:41  
We've also heard about ionization.

Carlos DeSousa  34:43  
Yes, as part of the process that we went through on COVID mitigation for public buildings, we did look into that. So one of the ionization strategies that we looked at was needlepoint ionization, and the only issue with it is we could not find a recent independent test results of the claims of the manufacturer that for virus kill. So because of that we did not recommend using that product. I believe the information we received was just from the manufacturer specific data. They had hired a testing laboratory, but we couldn't determine if it was an independent testing laboratory. To me if you're paid to review a product, it's really not independent.

Andrea Bunker  35:24  
Do you think those tests are forthcoming for that technology? Or is that something that hasn't been discussed or been seen in your realm?

Carlos DeSousa  35:32  
We are not seeing that as a dominant player in the strategies to mitigate Coronavirus, but there are places using it. I just don't like to recommend a product that there isn't, you know, real data, recent data that it actually works.

Andrea Bunker  35:47  
We appreciate that. Are there any other technologies that you see coming down the pipeline because of COVID?

Carlos DeSousa  35:56  
Well, I think one of the, I mean, the technology is already here, but I think that the hva systems themselves are going to be quite different in the sense that more dedicated outside air systems without any types of mixing during occupied modes is probably going to be more the way to go. Systems that next air do not make sense. And I think also filtrations of the systems. Presently, we filter outside air, and that's basically it. But we end up with systems that have energy recovery components. So what could happen is you supply air into the space, the air comes back through a recovery wheel. Now we, even though the airs don't mix in the system, the wheel portion of it does, so that could be a problem. So I think you'll see more filtration in equipment as well. So I think there'll be more outside air, more ventilation, and more filtration.

Andrea Bunker  36:43  
And are moves toward that usually fast in the industry, or is this something that will take years to develop?

Carlos DeSousa  36:49  
I think it's moving fast. And even the strategies of control systems are being changed  right now. On our projects, we're actually putting in a coronavirus mode, so that basically the HVAC controls person or technician or supervisor can essentially click an icon and put the building into that mode.

Andrea Bunker  37:09  
So you're overriding the CO2 controls? All of that?

Carlos DeSousa  37:13  
We're overriding the CO2, so we have the most amount of fresh air coming in, and we put the building into an occupied mode.

Andrea Bunker  37:21  
Now every library has a different type of energy source. So we have libraries that are running on oil, natural gas, propane, VRF, other all-electric systems. I put in hydrogen fuel cell too, because I know that's happening in Europe for some systems. But I don't think it's made its way here yet completely. But do you approach your measures for COVID differently depending on the HVAC system in place and what type of fuel it uses? 

Carlos DeSousa  37:51  
Well, I'm not sure that the type of fuel makes a big difference on this. But the type of system that you use and its effectiveness for ventilation is important. One of the systems that we have been using, and we have used in libraries, in fact, Walpole, the Walpole library is an example, I don't know if you've been there or not. But typical HVAC systems, you supply air overhead, and then you return overhead. So you have the situation where air comes down goes back up, and then it's exhausted. Sometimes it doesn't come all the way down, it's just exhausted. So ASHRAE has what's called ventilation effectiveness. Walpole library has what's called displacement ventilation, which means that the air is actually supplied low at the breathing level. So from finished floor to six feet above finish floor is all that we look at. And then we return the air high in the space. So the ventilation effectiveness by ASHRAE in a system like that can be 1.2 times that of an overhead system that has a supply high and a return low. And a system that supplies high returns high has about a point eight ventilation effectiveness. So those are strategies that we're looking at, and that we are using and have used but not so much for smaller buildings, such as libraries, but I believe you're going to see these systems for smaller buildings such as libraries.

Dominick Puniello  39:03  
Just to add to the discussion on the Walpole library. You know, the displacement system is great. However, we were only able to incorporate it into the new construction area; that was a renovation addition. So for the renovation system, we didn't have the luxury of as high floor to floor areas that we had existing structure and architectural features to work around. So there we use what's called a chill beam or induction system for the renovation area with a dedicated outdoor air system that Carlos described before, which is 100% outside air and supplying overhead. So while displacements great it might not fit in all areas. I do see it becoming more and more popular because of its increased ventilation effectiveness.

Carlos DeSousa  39:57  
And there's also no mixed air.

Lauren Stara  39:59  
Can I just ask... In a library that I was director in, not in Massachusetts, we had a raised floor system and the heat supply was in the floor, and then the exhaust was in the ceiling. Do you recommend that kind of airflow?

Dominick Puniello  40:15  
That's almost a hybrid of the two. An under floor and distribute distribution system has properties of both displacement and mixing. So it is, I would think, a good system, that it's got some of the displacement features, but it does have some mixed air action. But overall, it would depend upon your air handling unit level and how much fresh air you're bringing in. If you're bringing in a lot of fresh air within that system through an underfloor distribution system, it'll be highly effective. The under floor air distribution is really kind of a strategy with integration to not only just HVAC but electrical concerns for running electrical utilities, maybe trying to maintain higher ceiling elevations. So the idea being you have reduced ceiling plenum space, because you're running a lot of utilities through an underfloor air distribution system. The other thing it does is it gives flexibility in that the floor registers could possibly be moved. If there was an idea that a renovation would likely occur, you could just move registers from one spot to another spot in order to accommodate different places of occupancy and ideal distribution of the airflow.

Carlos DeSousa  41:38  
The floor itself, that can be a source to provide displacement ventilation. It's possible that you would have that in that library. I don't know how old it is.

Lauren Stara  41:47  

Carlos DeSousa  41:48  
2008? And what state was it in?

Lauren Stara  41:51  
It's in British Columbia,

Carlos DeSousa  41:52  
Ah, I see.

Lauren Stara  41:53  
Because it was a geothermal heat source.

Carlos DeSousa  41:57  
It is possible that they used a form of displacement ventilation.

Dominick Puniello  42:01  
Yeah, often why I say it's hybrid is because a lot of times it's just a small diffuser. And with a true displacement system, it requires a larger diffuser that has, you know, all these perforated openings, whereas a floor diffuser on an underfloor air distribution system, it will use some of the displacement properties in terms of displacing the airflow upward. However, it's typically a smaller diffuser. And right when it distributes out of that diffuser, it actually has some mixed air flow properties. It's actually inducing some of the air in order to get that plume going.

Andrea Bunker  42:45  
I'm wondering if there's anything else that you would recommend libraries consider as they're trying to deal with this pandemic? 

Carlos DeSousa  42:53  
You had one question regarding a fuel cell, correct?

Andrea Bunker  42:57  
Yes, I did. 

Carlos DeSousa  42:58  
Right. At present the fuel cells for commercial buildings, they use natural gas for the stack. So they operate, they basically take some sort of methane and they convert it to hydrogen. So it's a hydrogen fuel cell, but the fuel cell itself, and we've actually done a project in Woburn where United Technologies was the fuel cell vendor, it did not get installed, but it was prepped for it. But what you get out of the fuel cell, you get electricity, which is what you commonly know, right? But you also have hot water, very high hot wire, like 200 degree hot water. So with the hot water, you can create now a heating system, right. And you can also create a cooling system. I don't know if you knew that or not. But you can use what's called a hot water absorber. So the hot water absorber will work in the summertime. So the fuel cell would do this. It would provide you with electricity, and then provide you with hot water, and then provide you with a heating system and then provide you with cooling for your building. I've gone to Mohegan Sun in Connecticut, they have a fuel cell that's there. And I looked at their operation. They use all of those items that I just spoke about. There's also Cape Cod Community College. I went there, it's probably about 10 years ago or so, and they had a fuel cell there as well. The Department of Energy, it was actually the Department of Defense, had incentives to install fuel cells. I'm surprised we're not talking about fuel cells more. They're just, there's so much. When you actually look at the fuel cell from an efficiency standpoint, the fact that you're producing electricity, you're producing hot water, you're producing cooling, it's almost 100% efficient. I'm still surprised that it's not being used more.

Andrea Bunker  44:34  
And I know that it's widespread in Europe. I was hoping it would be here in time for my building project, a more residential application, but it just doesn't seem to be as available.

Carlos DeSousa  44:45  
Well, in residential applications. I only know this because I'm a sailor so I have a sailboat. I do have a friend of mine who is also a sailor and he installed a fuel cell on his boat and removed his generator. So on a small scale up to about five kilowatts, you can actually get a fuel cell. It doesn't not need to be propane or natural gas to fuel it. There's other fuels that you can use. 

Andrea Bunker  45:06  
What do you think is holding it up in the US that we're not talking about it more?

Carlos DeSousa  45:10  
Because we do things in life cycles. We don't necessarily look things on, you know, this is the right thing to do. So, we look at paybacks on systems. And so if a payback is more than, say, on a public job, if the payback is more than 10 years, a lot of people get antsy and not do it. Now, geothermal systems as an example comes to that. But if you have other goals, such as, you know, fossil fuel free buildings, well, then you may want to look at a fuel cell, if that's where you start from. It's cost is what it comes down to.

Andrea Bunker  45:40  
If there was more implementation of it, then the cost would be driven down, so it's kind of this circular issue.

Carlos DeSousa  45:47  
Right. It's a circular issue. However, it's similar to geothermal systems. Geothermal systems to date, which have just been so expensive, typical payback is 15 to 20 years, so you never achieve it. But the cost of the wells products, and there's a product called Rygan, for wells, which is, you know, a great product and developed for the oil industry, believe it or not, and that has reduced the cost of the wells. It's really the cost of the well. If you can get by the cost of the well, the system makes perfect sense. It's energy efficient. It's a water source system used summer and winter, you don't have to worry about the outside temperature at all, because you're using your own closed system inside the building. There's no exterior equipment. So all the equipment that normally fails is outside. All that is now brought inside. Yeah, it's simple paybacks is why some of these new technologies just take so long to get.

Dominick Puniello  46:39  
Yeah. And related to that, when we say lifecycle, it's not just first cost you're weighing. You weigh the first costs, the operating costs, and the ongoing maintenance costs. In terms of the operating costs, if there's relatively low gas or oil costs, those might look more attractive, maybe right now. But in the future, if those costs get escalated, in conjunction with a greater push and supply of alternative technologies, such as fuel cells or more people drilling wells, hopefully those prices come down. And if fossil fuel costs such as oil and gas rise, these alternative technologies will look much more attractive, and you'll have much quicker paybacks. That's really the hope.

Lauren Stara  47:30  
Can I go back to the question about emerging technologies for a second? This might not be specifically HVAC related, but I've heard a lot about far UV. Do you know anything about that technology and its potential? So it's a UV technology that's disinfecting a part of the spectrum, but is not dangerous to humans.

Carlos DeSousa  47:54  
I'm not familiar with that technology. The only thing I know is that they do have different levels of potency on the UVC. And the further you get away from that light spectrum, the less effective it is.

Dominick Puniello  48:06  
The far UVC, I believe is just a wavelength where it's less harmful to humans. So I think it really comes down to, when choosing a UVC manufacturer that they're certified, and any UVC that's output is enclosed within that device, so it doesn't certainly come into contact with humans.

Andrea Bunker  48:31  
So to wrap up, are there any other considerations that our libraries should be thinking about as they approach this particular topic,

Carlos DeSousa  48:41  
An existing building or new building?

Andrea Bunker  48:43  
It can be either,

Dominick Puniello  48:44  
In some of the topics we discussed, it's not, unfortunately, a one size fits all. You've got to really pair the best mitigation strategy for the actual building and its characteristics, especially in terms of older buildings with natural ventilation systems might be more limited into what they can incorporate. Whereas if a building system does have some type of HVAC duct distribution system, there's probably more options. However, you've really got to factor in where, say, potentially UVC can be installed, what's the highest level of efficiency filter that can be installed without negatively affecting the room comfort temperatures as well, and keeping an eye towards avoiding maybe really excessive energy bills. It's a balance between incorporating these technologies and keeping good thermal comfort conditions. And as we talked about earlier, the space conditions for preservation of materials, too.

Carlos DeSousa  49:53  
Right. One of the things that I would do either existing building on new is that any building that needs to use natural ventilation to meet building code requirements for ventilationshould stop doing that. They should have a mechanical ventilation system that no matter what gives you the ventilation that you need mechanically. I'm not saying to eliminate operable windows at all, I love operable windows, and they should keep them. But design those systems and do not count on that 4% of operable area of a window compared to the square foot in the space, because it's an old strategy. But you can't always use the operable windows as an example in the winter or even in the summer. So when you have a pandemic like this, you want to provide ventilation rates very high and you should do it mechanically so that you can control it. When you open a window, what you lose is the control. 

Dominick Puniello  50:42  
You know, that's one of the technologies that has been advancing throughout the years is energy recovery ventilation. So by using energy recovery on the cold winter days, we're not just introducing that cold weather temperature within the space, we're using the space temperature that has already been heated to pre-condition the incoming outdoor air. So that's helpful in terms of energy efficiency. A lot of older spaces don't have ceiling heights for full ducted HVAC systems. However, possibly smaller energy recovery type systems, where it's based upon just the ventilation required might be able to be incorporated. And again, it's unfortunately not a one size fits all. Some might be installed within say basement areas, others might be installed with attics. And unfortunately, some areas you might have to have installed exposed ductwork as part of that ventilation system. There are some ways that that can be designed and incorporated within the architecture so that it's not overly objectionable aesthetically. If you use some nice round ductwork that's painted could possibly be an add to the space characteristics. But there's a lot to factor in, and, in particular, another one is noise. We certainly don't want to have objectionable noise within a library. So there's a lot to that ductwork design, that has to be factored.

Andrea Bunker  52:18  
And I like what you said about the fact that energy efficiency and dealing with COVID in terms of HVAC systems don't have to be opposed to one another or working against one another. That it can actually be very beneficial to have that tight envelope. And to have that air coming through your system and being filtered.

Carlos DeSousa  52:39  
Yep. And actually a tight envelope is something that we recommend whether it's a LEED project or not, because it's one of those few things that there's no maintenance to it, and you actually pay for something that saves energy, and you don't have to do anything to it for the life of the building. There aren't many systems that can actually do that. So that's ideal. The other thing is the energy recovery systems have become so energy efficient. A typical system that uses a wheel is about 70 to 80% efficient. We typically specify system about 70%. What that means is that if you're outside air is say 30 degrees, right, coming in, and you're discharging the temperature at 70 degrees back to the outside, it means that the difference between the 70 and the 30 is 40, and 70% of that is 28. That means we're going to increase the temperature after that wheel from 30 degrees by 28 degrees. So it goes from 30 degrees to 58 degrees on just wasted energy, you're not combining air. So automatically, you're starting at 60 degrees only to ramp it up to whatever to 70, 80 degrees, 90 degrees to heat the space in the winter time. So that alone is just a huge savings. And there are even other types that are even more efficient than that for dedicated outside air systems.

Lauren Stara  53:53  
I know that after listening to this, a lot of librarians are going to have questions about the UVC, adding a UVC disinfection component to their HVAC. And I'm wondering if you can just give a very general ballpark figure for say a 20,000 square foot library. How much would it cost to add that kind of equipment?

Carlos DeSousa  54:17  
Hold on one sec. I actually have some pricing that's fairly recent. Pricing per unit is about $1,895.

Lauren Stara  54:27  
That's for the hardware.

Carlos DeSousa  54:28  
That's for the unit itself. Yes.

Dominick Puniello  54:31  
What size unit, though?

Carlos DeSousa  54:33  
Let me just see what this is based on this. I'm going to say it's about 900 square feet is what it would handle.

Lauren Stara  54:42  
And what about installation of a unit like that?

Dominick Puniello  54:45  
Well, it would vary depending upon your the four different options I talked about, whether it was installed within the unit, the ductwork, just a space terminal unit.

Carlos DeSousa  54:56  
This is a space terminal unit after the air handler unit. Essentially you take your diffuser out, and you'd put this unit in. So the actual unit cost is $1895. So if you took this and you, you know, take 50% of that as labor, so probably about $2500, in that range.

Lauren Stara  55:15  
And that's for 800 square feet.

Carlos DeSousa  55:17  
Yeah, it's about 900. I'm looking at the size that the unit can handle.

Lauren Stara  55:22  
But what does that translate into for cubic feet? You were talking about the difference between cubic and...

Dominick Puniello  55:27  
Well, that was with the HEPA filters, the cubic, air changes per hour, and the cubic feet are factors. With the UV, they're going to have airflow moving through it. So we talk about CFM, when we're looking at the UV, so it's much more easily to translate, you know, with the square footage.

Carlos DeSousa  55:48  
So basically, what this unit does, it treats up to 1000 square feet, and then it says that it'll clean the entire volume of the room in 20 minutes.

Andrea Bunker  55:57  
So you're essentially saying that for the UV, the ceiling height does not matter. But for the HEPA filter, it does. Just in layman's terms. 

Carlos DeSousa  56:06  
Yeah, the UV is actually looking at the CFM tthrough the ductwork. 

Dominick Puniello  56:10  
Yes on that ducted type unit.

Carlos DeSousa  56:12  
Yes, you're correct. So the CFM, while it's related to the space that it's serving, but its size based upon the CFM, and the duct size that it's treating.

Dominick Puniello  56:23  
Unfortunately, there's not an easy answer, as far as, you know, like $1 per square foot, it really you know, is going to rely upon the, you know, technology that you use, and the square footage of the building. The larger the building, that dollar per square foot will go down, whereas the smaller the building, the dollar per square foot value is certainly going to be higher.

Carlos DeSousa  56:46  
Yeah, so just on this example, it would be about $2 dollars and 50 cents a square foot,

Dominick Puniello  56:51  
I've done exercises for 100,000 square foot school, and it's around just over $1 a square foot.

Carlos DeSousa  56:59  
Yep. So this is based on one unit.

Lauren Stara  57:02  
Right, but then you also have to think about the maintenance cost and the increased..

Dominick Puniello  57:07  

Carlos DeSousa  57:07  
The maintenance cost is the filters, the actual bulbs are $80 times two. So two bulbs is $80, so there $40 each is what I had for parts that need to be replaced annually, and then just cleaning quarterly.

Dominick Puniello  57:20  
So again, on larger scales, those bulbs are going to cost more though. Typically, they have on the larger scale UV, you know, say for instance, the ones installed within larger air handling units, those are going to have runtime operation of around 9000 hours of life. So if it was run 24 seven throughout the whole year, it'll last for just over a year. And what we recommend is on that type of scale, integrating it into the automatic temperature control system or the building management system, so that the UVC could run when it's most beneficial. For instance, if you're running 100%, outside air through a system and you've got say MERV 13 filters already, you might not want to run the UVC at those times. However, at nighttime, when people have left, and you shut the ventilation system off, that would be a great time to run the UVC, just in a recirculation mode and kind of disinfect the air within the space. Which brings me to another point of that whole COVID sequence of operation recommendations. Another thing we're really recommending is at least two hours before and two hours after occupancy, the system should really run in the occupied mode, so that we're getting additional fresh air ahead of time and then additional fresh air and exhaust air afterwards, as well.

Andrea Bunker  58:54  
This is so very helpful. And I think it's helped us work through things in our brains in terms of how we better assist our libraries when they have specific questions. And, you know, when we look at the ASHRAE, it's hard for us to interpret. So for you to provide that information in terms we can understand is invaluable. So thank you so much.

Carlos DeSousa  59:16  
Unfortunately, ASHRAE is a technical manual. It's not meant for every day person to just look at and understand. I wish they had something simple. But if you do look at those two tables that I mentioned, that's a fairly simple table.

Andrea Bunker  59:29  
Again, probably a lot of this depends upon how long we're dealing with the pandemic. The longer that goes, the more testing that will be occurring. And I think the better manufacturing systems will help to mitigate the virus once more is known about it.

Carlos DeSousa  59:49  
On the UVC, that's actually split, so that there are HVAC equipment manufacturers that are installing this product as part of HVAC equipment. Then there are lighting fixture manufacturers that are providing this product within the space with the same claim. So one of them is at the user level in the space, and the other is a centralized solution. So I should note that the CDC on the last recommendations that I read a few weeks ago, they were not sure that the virus is actually being circulated back to the air handling equipment to be filtered out or treated.

Andrea Bunker  1:00:27  
But for the lighting, is that safe?

Lauren Stara  1:00:29  
Yeah, that was my question.

Carlos DeSousa  1:00:31  
Again, if you don't see it, UV is just like any other type of light, so it reflects. It can be contained within a box. It's how you use it in the space. You obviously want to have the UV light on in the filtration happening or disinfection happening when you're in the space, having it on when it's unoccupied makes no sense. They are being done so that they're on when the spaces are occupied, but you can't see it and you're protected from the radiation.

Dominick Puniello  1:00:57  
I think, too, this is where that you know, far UVC was going to come into it. Based upon what I read about it just safer than just the pure UV germicidal UVC. So that might be incorporated as well into future technology.

Carlos DeSousa  1:01:15  
I think it's going to be safe, and it's going to be effective. Those two things have to happen.

Dominick Puniello  1:01:20  
Right. I think we're going to see more testing, you know, from these manufacturers that backup claims through independent third party testing. I think that's really a key to ensure a level playing field by manufacturers.

Andrea Bunker  1:01:35  
This was so helpful. I can't thank you enough for all of your time to provide us with this information. Thank you.

Thank you, Andrea. Thank you, Lauren. Pleasure talking to you.

And thank you to all of you for listening. We hope this episode demystified HVAC in relation to COVID-19 and provided you with a course of action in attempting to create the safest environment possible for you, your staff, and your public. Remember to send to any questions you may have to We hope to follow up with Carlos and Dom early next year and get an update on the latest information, technology, and tactics in the fight we are all waging in this pandemic. Until next time, and be well.

Carlos's Answers to Interview Questions:
Dom's HEPA Spreadsheet:

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