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Multifamily Ventilation Strategies and Compartmentalization Requirements
September 24, 2014
Sean Maxwell, Senior Energy Consultant, Steven Winter Associates
Joe Lstiburek, Founding Principal of Building Science Corporation, Adjunct Professor of Building Science at University of Toronto.
Gail: Hello, everyone. I'm Gail Warren with the National Renewable Energy Laboratory and I'd like to welcome you to today's webinar hosted by the Building America Program. We're excited to have Sean Maxwell and Joe Lstiburek joining us today to talk about key challenges in multifamily building ventilation and strategies to address these challenges.
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We have an exciting agenda prepared for you today that will focus on challenges and multifamily building ventilation and strategies to address these challenges. Before our speakers begin, I will provide a short overview of the Building America program. Following the presentation we will have a Q & A session, closing remarks and a brief survey.
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And now, onto today's presentation. Our webinar today will focus on challenges and multifamily building ventilation and strategies to meet those challenges. If you would like more detailed information about any of these efforts or if you were interested in collaborating, please feel free to contact any of our presenters.
Our first speaker today is Sean Maxwell, a senior energy consultant at Steven Winter Associates. Sean is the certified energy manager and works primarily in multifamily buildings. Recently his work is focus on cost-effective retrofits including innovative approaches to repairing central exhaust systems. Today, Sean will discuss a field evaluation of passive vents of a makeup air strategy and offer design guidance to improve their performance.
Next up is Joe Lstiburek, who is the founding principal of Building Science Corporation and an Adjunct Professor of Building Science of University of Toronto. His work at BSC includes providing expert witness testimony, overseeing research and development projects and writing for buildingscience.com. A building science pioneer, particularly in the areas of air barriers, vapor barriers, and vented and unvented assemblies, his work has impacted building code practices throughout the world. Dr. Lstiburek is also a noted educator, and author of the bestselling Builder Guides. Today Joe will present several balance ventilation options that meet the ASHRAE standards 62.2 2013 ventilation requirements and various air ceiling compartmentalization options beneath the current and proposed requirements. With that, I'd like to welcome Sean to start the presentation.
Sean: Hello, everyone. I hope you can hear me okay. So, my name is Sean Maxwell. I'm with Steven Winter Associates and I have to confess that I'm really thrilled to be on this webinar with Joe Lstiburek, who's absolutely one of my heroes for the past ten years. So, it's a real honor. So, I'll go over our research in multifamily ventilation and compartmentalization. So, in the past over the past few years we've been doing research on compartmentalization and ventilation and their interaction. And the main question we've been asking is since in New York City where we mainly work, we have a lot of buildings with exhaust only ventilation or at least exhaust ventilation. We wanna know where's the makeup air for that exhaust coming from? So, a pretty simple example is single family home where you have an exhaust fan that's pulling air out of the home. Where's the air to replace that coming from? We generally assume it's coming from the envelope. And so, that's the basic question we're trying to answer for multifamily buildings. So, we want to know where this makeup supplier is coming from.
So, in some buildings it's pretty easy to tell centrally ducted supply like an ERV; it's easy to measure and verify that there's air coming into the unit. We've also tested buildings with door undercuts as a means of makeup air, corridors’ are pressurized and the units are depressurized and air supposed to make its way under the corridor door. And we've tested a Nova PTAC unit with a fresh air kit and it has a small fan that's supposed to pull air from outside through the unit and deliver indoors. And finally, we spent a lot of time looking at passive vents. So, passive vents include things like trickle vents and air lids and all sorts of other vents that are supposed to work, supposed to draw air into the envelope.
So, what we're trying to do is quantify these air flows. The easiest one to quantify is the exhaust fan so we can measure that and we know that all the air that comes leaves the apartment through the exhaust fan has to be made up from somewhere. So, some sources of makeup air like trickle vents and the exterior envelope we'd probably call those good sources of makeup air. But some of the other sources would be less desirable. So, airflow under the corridor door is not good and airflow through the corridor wall is not good. And also airflow through interior walls, floors and ceilings from your neighbors is not good but all those equal the flow from the fan. So, when we're trying to show what's adequate makeup air; we have to come up with a term to express this and we just called it controlled makeup air fraction, which is the amount of makeup air provided by say a trickle vent which is a known source of fresh air over the air removed by the fan. So, in a balance ventilation system the controlled makeup fraction is one. So, there's for every unit of air that's thrown out there's one that comes back in. So, we don't really have a measure of what's considered good but if just for the purposes of this presentation we called 50% makeup air coming from a known clean source as good; we'll consider that good enough for this presentation at least.
So, typical exhaust only strategies in multifamily buildings rely on having equal pressure in all of the apartments drawing air out of the apartments and air coming in from other places to make up for it. This is a pretty common scheme you'll see in this presentation which is three apartments in a row and the corridor in front and the exterior in the back. So, when you have three apartments and they're all at the same negative pressure you're not going to get air passing between units because your, there's no pressure difference between them. But what we found when we logged pressure in apartments overtime and monitored window opening was when people open windows, the pressure in the middle apartment for example drops to close to zero and you get free exchange of air in and out of the apartment. You also, that when someone opens window in that apartment that affects the pressure in the neighbors and so the pressure, the pressurization in those neighbors decreases.
So, what happens if someone burns a grilled cheese sandwich? That pollution that comes from that apartment, this middle apartment is now at zero Pascal and the other apartments are negatively pressurized with respect to that one and so as the corridor. And what we found was air was flowing out of this apartment with the open window, down the corridor and into the apartments with there was still negative pressurized. So, this is obviously not a good situation if someone generates pollutants in their apartment; they try to ventilate and it ends up going into everyone else's apartment. It's not good, but unfortunately this is a pretty common phenomenon. So, the idea with trickle vents and passive vents is to provide a known source of makeup air. There's pictures here of trickle vents and then on the right is an air lid. Both of these go next to your envelope and draw air straight from outside.
So, we tested passive vents both air lids and trickle vents. Here you can see me expertly taping this cardboard box around the trickle vent. But we're depressurizing trickle vent and monitoring the flow and the pressure at the same time. And so, the idea is to get performance curve for trickle vent as it's installed.
So, this is data from one building; five trickle vents, the blue line shows performance from these five trickle vents at various pressures and then the line above it is the same model of trickle vent done in a laboratory. So, ours differ from the lab results probably for a few reasons. Maybe my cardboard box isn't completely air tight but there's probably also some other factors that are contributing to this.
In some buildings, we find that performance of the trickle vent is actually affected by the way it's installed. So, in case you don't know much about trickle vents many of them actually come in two parts; you have an inside part and an outside part. The outside part is more like a rain hood and a screen and the inside part is a little operable vent that you can open and close. And the outside hood goes on the outside of the window frame and the inside goes on the inside of the window frame. And the trickle vent manufacturer sends this assembly to the window manufacturer and the window manufacturer cuts a hole through the window frame and attaches the two charts of the trickle vent to the inside and outside. So, there supposed to be a clear hole between inside and outside but you can see from these pictures that there's obviously not a clear hole between inside and outside. You can see light through some of these drill holes but obviously there's a lot of fiber glass here in a way of airflow. So, some of the trickle vents we test performed nowhere near their specification. So, we're often asked by architects how do you specify passive vent? And it's kind of a tricky question because you need to know a lot of things. You need to know how tight the apartment is going to be; how well where the strip the door is gonna be and how airtight it is. You need to know the flow rate of the exhaust not just how much is on the plans but how much is actually going to be withdrawn from the apartment. And then you need to have a good idea of the trickle vent at this expected pressure it's gonna develop in this building that's not built yet. So, it's a pretty difficult thing to specify a trickle vent when the building is not build yet. So, the standard procedure is to put one trickle vent in every room. So, common trickle vents are about, they can range in size but we see a lot of them that are about four square inches nominal opening per vent. And if you compare that to a common apartment blower door test from a common one bedroom apartment. It could have as much as 70 square inches of total leakage not including the trickle vents or the door leakage. So, that's by comparison the amount of leakage, the amount of free area from a trickle vent is a lot less than a free area from the rest of the envelope. And so, if you're depressurizing the envelope with the hopes that air will come through only the trickle vents you've really got to reduce your leakage in order to make sure that it comes from the trickle vent and not from other places that you don't want. So, we tested the performance of passive vents in two buildings and then monitored pressure over a couple of weeks. And we also did some other measurements at each building. So, two example buildings; the first one was trickle vents and the second one was air lids; the first one had fairly airtight apartments, 2.5 ach50. And the other building had much leakier apartments in average of 6.7 ach50. So, much, much leakier.
The exhaust rates were fairly similar per apartment; the average of 41 or 53 CFM. But you can see that the tighter apartment, the performance from the passive vents is a lot better from the building with airtight apartments than it is from the leaky apartments. So, obviously air tightness has some effect on the building for passive vents to draw fresh air. So, we tried to do this again in a building with trickle vents but some super tight apartments. So, this chart here shows the results from nine blower door test; these apartments are all near each other. This, the bottom row is the second floor apartments 201, 202 and 203 and on top we have 401, 402, 403. So, four out of nine of these nine apartments received enhance air ceiling and the numbers are really a lot, a lot lower than the unsealed apartments. You could see in terms of CFM 50 per square foot all below .1 CFM 50 per square foot which is a lot lower than many apartments can achieve. So, putting this in perspective for a lot of blower door test; we've done many, many compartmentalization test over the years. Compartmentalization test is a single blower door in a single apartment and depressurizing only that apartment and the doors and what is to the neighbors are open during this test. So, it's single apartment test. So, we've done a lots and lots of this for various green building and utility programs such as LEED for homes.
So, this is a histogram of some of the results. So, you can see that the great majority of them thankfully fall below the thresholds required for Energy Star for multifamily high rise and LEED for homes that's the threshold they need to meet in order to qualify for the programs. LEED NC has a much tighter threshold but still a good number of apartments can meet that as well. This is approximation. But the apartments in our study some of them are very, very tight and the rest of them are pretty standard air tightness. So, what does that air tightness gets us? Well, in terms of operating pressures the sealed apartments are generally a lot more able to draw air to depressurize the apartment and keeps them depressurize. The apartments in red, these are the operating pressures we just sampled on a random day.
We sampled these apartments on a single day and I honestly can explain what this and why one of these apartments is negative 4 while this unsealed apartment is in negative 12. But generally the, when we did the single point test the sealed apartments were able to develop a much stronger negative pressure than the unsealed apartments. So, when we do this test the trickle vents are open, the bat fan is running; exhausting air and the apartment door is closed tightly and so are the windows. So, this picture on the right shows a data logger that we use to monitor these pressures over couple weeks’ time. So, hopefully we'll get some more data here to confirm this suspicion that tight apartments can hold pressure better than leaky apartments.
So, this is, here are some test over about ten minute period in two different apartments in among this group. And to explain the chart a little bit what we did was we stood in the apartment with data loggers and turned the, manipulated different systems in the apartment and watch what happened. So, in the first condition we turned the exhaust fan off and just logs, having pressure in the apartment with nothing going on. Then we turned the exhaust fan on but closed the trickle vents, closed the door, closed the windows. And this is for the maximum pressure that you would see in this apartment under any conditions. Next we opened the trickle vents and that relieve some of the pressure generally. And then we also cracked open the front door, to the apartment the corridor door. And the reason we did this is that sometimes, since we're logging in a building in which people are still working sometimes they enter the apartments and forget to close the door tightly. So, we wanna know what is it look like when this door is just cracked. And then we close the door again, trickle vents are open, exhaust fans on that's state number five. And then number six is we turned the fans off again. So, in the standard apartment you can see that, you can see a couple of things. First the pressure across the trickle vents which is the exterior pressure; this blue line in the graph, on the top is pretty much close to zero all the time which tells us that there's pretty much no airflow coming from the trickle vents at any time. By contrast if you look at the apartment below the heavy sealed apartment; if you do anything in that apartment the pressure changes. So, look what happens when you turn the fans on and close the trickle vents; the pressure goes all the way to negative 15 but when you open the trickle vents it drops to, raise it to negative 12 and that's the normal operating pressure of this apartment. So, negative 12 means you're gonna get 12 Pascal across that trickle vent and that's pulling air in from the trickle vent pretty much all the time. Even when you have the door to the apartment cracked open you're getting pressure across the corridor door and across the envelope. So, it's still drawing air from the trickle vents. So, it's pretty clear that in this one building you compare one standard apartment that's sealed to say, EnergyStar standards and then you compare to this super sealed apartment. This, there's the pressure response of these two apartments is totally different.
So, what we're trying to do is quantify these airflows. So, we're using an energy conservatory flow blaster for fan flow measurements from the exhaust fan. We're using pressure measurements for the trickle vents and the same for the door and measure the door leakage as well. And then we use data loggers to watch this pressure over time and see how this building reacts over the long term. So, I wanna make a distinction here about the different kinds of leakage that we're, that we're talking about. We have blower door test that pretty much, a blower door test will give you leakage from the exterior envelope, interior envelope and the corridor wall. But it won't give you leakage; the leakage value of the corridor floor or the trickle vents. So, that's one number. Then when this building is put into real operation those pressures go away and you have prevailing building pressures which for some of the, if everything is working as it should and your target apartment is at negative five for example like we had an example before and your neighbors are all at negative 5. Some of the leakage between those apartments will be eliminated because there's no pressure difference between those apartments. So, some of the leakage that is kind of for in a blower door test is not actually functioning as a leak in normal operation. So, really functional leakage is relative to those surfaces that have pressure difference during normal building operation. So, how does this whole translate to airflow in these target apartments. The, our research is still ongoing. We still have data loggers in this building. So, we don't have all the data to show you what a natural apartment is.
But this is an ideal apartment and if we just divvy up these leakages we can see how they amount to airflow through the exhaust fan. So, blower door test numbers, the total of all these leakages here is 110 CFM and however, so this is the only number you get from your blower door test, 110. But that number is divvied up between several surfaces. So, exterior envelope these are just perpetrated designations but maybe a good guess is about how much of a blower door number comes from each surface. So, the exterior leakage might be 20% of the total blower door number and the corridor wall might be 20% of the total. But the interior, two interior walls and the floor and ceiling might amount to 60% of the total leakage. So, that's how these are divvied up for this example. And the reason is as important as that some of these leaks are functional and some of them aren't in normal building operation. So, the exterior those do have a pressure difference across them during normal building operations. So, that is a functional leak but the interior walls hopefully should not have pressure differences between apartments. So those are not functional leaks. So we have to test the door leakage separately, but when we do, we find for a very tight apartment -- very tight door you can get those down to about 20CFM50. Typical on weather strip doors might be well over 150CFM50. Trickle vents if you really do have close to 8 inches of free area, you could expect maybe 65CFM from that trickle vent. This is using that chart from the manufacturer that we looked at before. So, about 65CFM coming from the trickle vents. At a normal building pressure 10 Pascal, these flows at 50 Pascal dropped considerably. So, the total of the functional leaks has a total of the exhaust -- the controlled makeup air fraction if got the amount coming from trickle vents is 29CFM out of a total from the fan of 58CFM and that controlled makeup air fraction is in 50 percent.
So, this is a theoretical apartment still at this point. We do not actually have an apartment that is this tight. We have some of these apartments that we sealed tighter got close to 110CFM50, but they did not get totally there. So, the tightest one was 127CFM, I think. So, we are still not there but this is the amount of air tightness that might be possible; that might be required to make trickle vents work like they should. And how do we get them that tight? Basically, we cheated. So, we collaborated with UC Davis who Mark Madeira and Curtis Harrington at UC Davis are developing an aerosol process similar to Aerosol that uses atomized building sealants. You can see in this picture in the middle you have got a mist spraying into the apartment. It is actually water in that picture, but it looks similar when this is going on. So, you out the blower door in the apartment door and you pressurize the apartment to, up to a hundred pascal, and then you put these injectors in the apartment and spray this mist into the air and the mist finds its way towards the leaks and it sticks on the corners of the leaks and eventually clogs them up. So, you can see it is pretty effective. So, although it took us quite a bit of time to setup and setup or data loggers and everything which would not normally be done, we still averaged 75 percent leakage reduction in these apartments over an hour and a half. So, it is pretty dramatic. So, we started with the same types of apartments that we had in the rest of the building and you can see on the chart below that leakage just drops and drops and drops and drops until it approaches a sort of a minimum -- a minimum leakage. And so this is pretty, pretty exciting. So, this aerosol sealing does really well when compartmentalizing each individual unit, but it also seems to have an impact on the neighbors. So, the middle apartment and the lower right apartment were also seem to be benefiting from the aerosol sealing of their neighbors. So, this is a pretty cool technology and you help to work more on this in the future with UC Davis, but is this available to the greater market? Not really. Let us look at this graph again. We think that the air leakage, the air tightness necessary for passive vents to work at somewhere around, around here where, close to where we are right now with this aerosol sealed apartments. But not sure that this is something realistic for the industry at large. So, conclusions that we draw from this is that from the air pressure monitoring that we did and I think all of you will agree compartmentalization is beneficial for the operation of the building overall. And if you have ever tried to specify or test the trickle vent, it is, you realize that getting actual infield performance of this is very important, but difficult to do. So, we think that passive vents can function if you put them in extremely tight apartments, but is this something that we want to be recommending for the industry at large. I think we will leave that for a group discussion and I am sure Joe had some comments on whether this level of air tightness is achievable on a wide scale or whether it is even advisable. So -- and that is -- that is it for me.
Joseph: Hello, everybody. Sean, thank you for those nice words at the beginning of your presentation and thank you for sharing what I think is some pretty fabulous, fabulous work. I am going to be presenting from a slightly different perspective. I do not believe that if we have reasonable compartmentalization that any form of exhaust on the ventilation is, is possible or practical or functional. Next slide.
I love the phrase, "Build Tight - Ventilate Right" this comes from Jim White almost 35 years ago. Next slide. The question is this, "How tight and what is right?" from Sean's work as well as other work in -- that we have done, well, a lot of work has been done by Canada Mortgage and Housing Corporation. Duncan Hill's work and some of the RDH work in Vancouver were pretty clear that the 0.3CFM per square foot at 50 pascals is a reasonable, achievable metric that results in significant tightening of buildings that 0.3 is very close to three yard changes per hour at 50 pascals for a typical of -- a typical compartment. The 0.3 is also now the ASHRAE standard 62.2 compartmentalization number. So, I think we are pretty close to deciding how tight is practically achievable. The question of what is right, now needs to be addressed. Next.
We cannot rely on infiltration in a compartmentalized apartment. We have an essence a six-sided cube and for all intents and purposes, is the only side that we can rely on for that air is the external surface. This is a staggeringly difficult problem to resolve with exhaust systems. Next. These are the metrics that have been bandied about for many years, 0.02 for materials, 0.2 for assemblies and 2.0 for enclosures. The 2.0 for enclosures is -- as I have mentioned is it is pretty much where, where we have settled or where I see the consensus appearing and that -- again, that is around 0.3CFM per -- at per square foot at 50 Pascal and that correspond very nicely with Sean's Instagram and the results that we are seeing from other parts of the country. Next. To put this in the perspective, 3 ACH as getting rid of big holes; 1.5 ACH is very difficult, but it means it is getting rid of small holes and the 0.6 is unbelievably difficult to achieve and it’s the German Passive House number. I think that is neat if you are wanting to be the member of a select club of people who like to make things incredibly tight, but it is not -- it is not a reasonable number from an industry perspective. Next. So, build as tight as possible with balanced ventilation. That is where the engineering side of me or the engineering side of our firm is -- in our experience is -- has ended up as tight as possible from a practical perspective. It seems to be the three yard changes per hour at 50 Pascal, the 0.3. Now, the boxes or the cubes; the compartments are so tight that the only system that we are finding at actually works and this one that is balanced. The amount of air that is being brought in is balanced by the amount of air that is being extracted and this is done with interlock fans or mechanical ventilation. This is especially the case now that ASHRAE standard 62.2 has significantly increased the ventilation rates since -- well, in the last four years which resulted in the net doubling of the ventilation flow. So we are talking about 50 to 60 CFM of continuous air change and that, that flows at those flow rates at three yard changes per hour at 50 Pascal or the compartmentalization number. We are talking about 20 Pascal to 30 Pascal continuous negative pressures if we are talking exhaust ventilation. With balanced ventilation, of course, we do not have the negative pressure. So, we know that we are going to go to a highly negative condition if do not have balanced ventilation. The question is, is a highly negative pressure desirable or acceptable? There recent consensus on this, I, I think that we have some serious issues with those kinds of high -- high pressures or high negative pressures. I have decided to abandon that approach from an engineering perspective. So, balanced ventilation is the place to go with some form of distribution or mixing within the compartment or within the building. And coupled with a source control, spot exhaust ventilation, advanced filtration or enhanced filtration and materials that do not give off bad stuff and the very end of this, balanced ventilation makes energy recovery possible. That is not the most important thing and the most important is the balanced ventilation with the distribution coupled with a source control, but it is nice that with the balanced systems and recovery is possible. Next.
This is a classic HRV. We do not see a lot of these in multi-family construction. I think we are going to be seeing a lot of these in multi-family construction. The current problem with the industry is just that the systems are much larger than they need to be. We are talking 150 to 200 CFM systems where we really want 50 to 75 CFM systems or even -- or even smaller. Next. A more brutal way of doing it not as selling it would be to have outside air coupled to the return side of the air handler where the air handler is always operating at a fixed speed, and that is coupled with exhaust fans that are also continuously operating. So, you in essence have, say, two bathroom fans operating each at 25 CFM continuous, coupled with outside air being brought in at 50 CFM and you have a fully-balanced -- a fully-balanced system. Then, this is not as elegant as a balanced HRV or ERV, but it certainly -- it certainly works. The energy handling, of course is you want to have them highly efficient blow in order to do this, ECM motors of course, we have. And one of the advantages of this is that we can have very high filtration; went to central air handler and that has some very nice advantages. Next. Architects hate this image. We are basically poking lots of holes in the facade. Each compartment needs an air inlet and an air exhaust from a decentralized mechanical system approach. Next. I do not view this as horribly aesthetically bad, but apparently, I have no taste and I just do not understand aesthetics. The engineering maybe is this is something beautiful, I guess this is why as if perhaps explains the historic problem between engineers and architects getting along. These balanced systems came out of necessity in extreme climates such as hot, humid places such as the coast of Florida with a condominium construction, and that was the only way to handle the humidity issues in each apartment. A compartment also had to have supplemental dehumidification. Next.
Here is our attempt in minimizing the number of holes gaining a number of exhausts in one particular hood. Next. Effective low-cost and not particularly elegant way of providing supplemental dehumidification. It has been to locate a standard off of the shelf dehumidifier inside the return closet. Well, it is cheap; it works; what could be possibly bad with it? Well, it is not ducted in a number of programs such as LEED, discourage this. Next. It is possible to have such a system, you know, with a ducted -- fully-ducted returns opposed to return closet. You are just basically going to be extracting air from the closet through your return system. So you know, the approach can be made to work without an awful lot of cost. Next. This is not a beautiful looking thing [Laughs] in fact, this is so unbeautiful-looking that a lot of project the contractors actually put the chintzy cheap-looking dehumidifier in a sheet metal box to make it look industrial. And apparently, it is not exactly Intel inside; it is the humidifier inside. Next. When you do not have -- if distribution system is not unusual that the humidifier is located in -- for example, a linen closet with a louver door as amazing as this seems it, it has been proven to be effective. Now -- and it is based on we are going back 20 years where we are attempting -- where we have been called upon to handle low humidity problems and in a small condominium and apartments units in Florida and in Texas. Next.
Washers and dryers; I do not think people understand that you cannot put a 200 CFM exhaust dryer in one of these apartments. These apartment units that are at three yard changes per hour at 50 pascals or 0.3 CFM per square foot at 50 pascals. They go to 50 to 60 pascals negative. Basically, exhaust dryers do not work if you compartmentalize in these -- in these particular apartments. And so, the only technology available -- well, there are two. One is practical and the other is yet to be figured out practically. One is a condensing dryer that there is not a vent to the outside. The other is providing a dedicated interlock makeup air fan into the room or the face that the dryers -- the exhaust dryer is functioning. Easy to say, not easy to do. Next. That brings us to one of my all-time favorite controversial subjects. You cannot put a kitchen hood that is extracting at 1 to 200 CFM into one of these apartments without providing interlock makeup air which is why most apartment units do not have kitchen exhaust hoods. They have re-circulating hoods and that be a re-circulating hoods similar to a toilet that never flushes and just swirls the affluent around and around and around. If we are going to want exhaust hoods over cooking surfaces which, for the record, I believe are desirable than necessary especially, if we are dealing with the PM 2.5 issue. All right, I plead LBL's work on -- in this regard. We are going to want high capture efficiency. We are going to need flow rates that are probably between 1 and 200 CFM and that is going to require interlock makeup air. If you're going to do interlock makeup air, makeup air needs to be introduced at the bottom of the cooking surface. You have to have a hood that is wider than the cooking surface and deeper than the cooking surface. We know how to do this from the experience in restaurants. What we are in essence doing is simply downsizing the standard practices in a well-designed commercial kitchen. Next. From an engineering perspective, making the hood bigger and deeper and introducing the makeup air is fundamentally straightforward. It is not the easiest thing to incorporate from an aesthetic perspective and a practical perspective in a small apartment that does not have the space available. You cannot have 100 percent of the makeup air delivered under the unit. You are required to have a zone of negative pressure to cooking surface. So, you tend to provide 70 percent of the makeup air under the unit and then the remaining 30 goes into the general space. So, when we design these systems with an interlocked fan that is bringing air in from the outside, let us say that the exhaust flow at the hood is 100 CFM or providing a 100 CFM of makeup air. We would deliver 70 CFM underneath the unit and then 30 CFM of that 100 into the general space. Next.
In a house, it is fairly straightforward to do, you know, you introduce it through the floor; that is not a practical technology in apartments. Next. Just to demonstrate how much of a hypocrite that I am, this is the exhaust hood at -- at my house. It is very, very attractive and totally non-functional, because it does not have enough of the capture efficiency, but it does look good. Next. This is my proposed retrofit. I am having a great deal of difficulty selling this concept to the architect at record who I share this space with. Next. So, what are we faced with? The bare minimum that we are seeing that actually functions is outside air to the return side of the air handler that is interlocked with continuous exhaust at the bathroom and the re-circulating kitchen hood, which again for the record, I dislike contently but this is what we are likely to see with three yard changes per hour at 50 pascals with the ASHRAE standard 62.2 ventilation rates. Next. South of the Mason-Dixon line we are going to end up having to add supplemental dehumidification, and the reason is, is that the loads are so low in these units and the outside air change rate is so high; the latent load is at the point where at no typical coil design or air conditioning system is capable of handling. So we are going to -- we are seeing and have been seeing for many years now the need for the supplemental dehumidification system, but it is not elegant, but this is the least expensive approach that apparently are seeming to us as working. Next. The idea of having a kitchen exhaust hood to the outside is a non-starter with the tightness that we are seeing. Next. A dehumidifier does not help us. Next.
What we need is an interlocked makeup air system with the -- with the kitchen hood. We know how to do this, but this adds another hole in the wall. I think -- I think that was a Pink Floyd song well, mentioning the fact of makeup air. With this approach, you are going to have the outside air to the return side of the air handler. The air handler is operating continuously. This basically operating in conjunction with continuous bathroom exhaust. This is what I would view as the minimal acceptable approach and then you have basically condensing dryers. Next. You had the dehumidifier south of the Mason-Dixon Line. Next. This is a much more elegant approach that provides heat recovery. We are now, in essence, not relying on the air handling unit itself to do this air change. What is nice is that you can get rid of the furnace air conditioner completely and go with radiant heating or packaged terminal heat pump and the general system works the same. Next. Even with an ERV, a dehumidifier is going to be necessary because the ERV does not dehumidify. It maintains humidity but does not create the dry conditions. So, the air conditioner provides the cool but the dehumidifier provides the dry and the ERV maintains those conditions. There is a lot of misunderstanding of what an ERV is capable of doing versus not doing. Next. We see a lot of these in the Pacific Northwest. The nub is that we -- this would not work with the kitchen exhaust without having an interlocked makeup air system. Next. As we go down the coasts, we are finding that people are adding packaged terminal heat pumps that provides both the heating and the cooling; HRV, ERV; pretty slick system but the problem child is still the kitchen.
Next. I don’t know of any way of getting around the interlock makeup air for the kitchen exhaust. You sure as heck don’t wanna run it through your HRV or your ERV. Next. And man, south of the Mason-Dixon Line in east of interstate 35 in Texas that whole miserable region of the country is gonna need supplemental dehumidification at the flow rates we are talking about, under ASHRAE and under LEED. We’re just gonna have to suck it up and accept that or we’re gonna have to lower the rates. Good luck with that approach.
Next. Get used to condensing dryers. 200 CFM of exhaust for a standard dryer isn’t in the cards anymore. And I have yet to see a practical makeup air system that’s interlocked with, a standard dryer. Next. Once we achieve the compartmentalize in the units, we have the corridors in the hallways and the elevators to deal with as well. This is- the implications of these are multi-faceted. It’s not just the compartment. Next. It’s nice to have the elevator under a slight negative pressure, you’re gonna need to provide some form of makeup air. That makeup air is gonna typically introduce into the- into the corridors. This air is generally not gonna be conditioned and it really doesn’t have to be because the flow rates are exceptionally low. We’re talking of maybe 15 or 20 CFM per one of these long corridors - and what’s nice about that is you can just simply using- use dilution mixing in the air and the space to partially temper this air.
Next. There’s a 3% leakage requirement at the top of the- of the shaft for elevator car. This goes back a century with respect to smoke and fire control. That hole defeats the entire purpose of control and the only solution just to have, an interlock motorized damper that’s controlled- that’s connected to the fire control systems. So you get rid of the big passive hole at the top of your elevator shaft with the motorized damper that’s, always closed when the power is energized when there’s a power outage, the damper opens or when there is a call for fire or fire call, the damper opens. This is separate from an exhaust system that constantly creates this slight negative pressure. The airflow regulator is necessary because of the stack effect the flow rates are gonna vary seasonally and with the height of the building.
Next. This is what they looked like. This is now common practice in Florida particularly because it has been a major problem for unconditioned humid air from the mold perspective. Next. As strange as it seems, some people are determined to over-ventilate the corridors and over-pressurize the corridors. And that’s gonna require pre-conditioning in the air because that’s almost a 100% latent load and there’s no sensible load in these corridors cause they’re not usually seeing any exterior walls. This is not an easy answer.
Next. Trash chutes, they got to be negative. Gotta suck. Next. I’ve seen in the hotel industry being interlocked of you know, basically air from the rooftop, supply to corridors with smoke dampers at each floor, balance with exhaustion in the elevator shaft. This is sometimes coupled with energy recovery as well. Next. There is the energy recovery. This is for a premium building. I, see this rarely and when I do a little tear forms in the corner of my eye as I’m so excited to see something like this. Good luck. Next. This is a Florida solution, pre-conditioning the air.
Next. We often see ceiling-mounted systems that have no outside air, we don’t introduce any outside air. All they’re doing is providing some modern tempering or conditioning in extreme climates. Next. Here is the trash chute. We have to have that at a fairly high negative pressure for obvious reasons and the trash room itself has to be even more negative unless requires compartmentalization. And life’s one- and one of life’s ironies is the highest negative pressure is in the tightest compartments need to be around our- our trash.
Next. It was a dream of a number of us over the last 30 years to be able to put our elevators in vestibules. Whenever we put them in vestibules to compartmentalize the building from a stack effect perspective, I can just tend to defeat the best engineer by leaving the doors or trying the doors open. I’ve come to accept the fact that this will probably not occur in my lifetime. And so, from an engineering perspective, it’s a desirable thing to have but from a constructability and occupant perspective, occupants don’t like it.
Heather: That’s the last slide in Jo.
Joseph: Well apparently, I’m done.
Gail: Ok. Thank you. Ok, we’d like to thank our presenters for those great presentations and we have time now for a few questions. We already have some great questions from the audience and you may submit additional questions to the questions pane on your screen. The speakers will answer as many questions as time allows. So, the first question is, for Sean. Why is the manufacturer’s data for trickle vent somewhat different than yours?
Sean: Well I tried to show that there’s often differences between the installation in the laboratory and then the installation in the field. We- we’re gonna be doing more trickle vent and test on this- this current study building where we’re gonna test the airflow through the trickle vent and then compare it to the manufacturer’s data. But we’re also gonna take it apart a little bit and see how well it’s been constructed through the window frame. So I think that has a big impact on how well they function, how much- The trickle vent might be nominally 4- 4 inches of leakage but if the window manufacturer didn’t cut the holes exactly right through the window frame, you might have less- less than that. So, that could be- could be one reason why the data is different. We are also gonna try a different method which is a method we were using to test the trickle vents was basically putting a suction on the trickle vent itself and measuring using a low flow plate, on the duct blaster so down to 1.4 CFM but we’re probably going to do a pressure-equalized method. So the measurement instrument whatever measurement instrument we use is not gonna be affecting the measurement. So I think we’re hoping to get even more exact numbers so we can confirm that it’s not, confirm whether the field installation equals the laboratory results.
Gail: Ok, and then there was another question about trickle vents we have heard that tenants do not like the trickle vents especially in cold climates such as Chicago and they will cover them up. Have you encountered this?
Sean: In many, many apartments that we’ve gone into people have no idea what those things are. And they’re usually closed, they are usually closed and then people often open the windows regardless. So, I would say that the tenants need to be educated on what they are for but it’s also possible that it’s just not providing enough fresh air. So, I haven’t heard so much that people close trickle vents because they don’t like them but I think, they just -- a lot of times don’t know what there for. I have, it is definitely possible that trickle vents and other passive vents like air lids if you don’t install them according to the manufacturer instructions. That is, we have been in some buildings where they put the air lids near the floor for architectural reasons the manufacturer instructions call for them high up on the wall so that a draft isn’t drifting over people’s feet but in some buildings they put them low and then people complain about cold drafts and that is just because there’s cold air we can right near your feet. So, that’s another reason people would close them up just because of comfort problems.
Gail: And here is another question for Sean. Do you think that the super sealed apartment will be stuffy?
Sean: Don’t know yet. I were gonna hopefully conduct some humidity monitoring but yeah it’s possible that with the super sealed apartment state it could be stuffier especially if the trickle vents aren’t pulling enough fresh air.
Gail: And another question regarding ASHRAE 62.2 and its adoption by the IBC. Should the requirements bury by climate region across the country? So, for what’s needed in New York, Anchorage, Vegas and Taos would differ?
Joseph: Sure, give me the easy one. Yeah, no, then the logic for that makes no sense but this is in response to what I view as an over ventilation number to begin with. There’s push back because of comfort issues and humidity control issues and the cold climates and the hot human climates and that simply tells us for my perspective, that these flow rates are not achievable for dilution perspective, without some kind of a comfort or energy penalty and so the idea is that, “Well Gee!” Let’s reduce the rates because we created a problem with an excessive rate in a cold climate and excessive rate in a hot human climate. Well you have to ask yourself, where did the rates come from in the first darn place? I thought it was the control contaminants and that’s how the rate was established. So, if we can we can reduce the rates in the hot and the cold climates why can’t we reduce them everywhere? Interesting philosophical question. In the past the argument was, you know we could reduce the fan rates in cold climates because the stack effect in the winter time compensated for that, and that was actually a reasonable way of looking at it. Except now we’re in closures are so tight that the infiltration performing to the stack effect does not compensate for that. So, I tell the committee that they can’t have it both ways and that’s not exactly a popular position at this particular point. In terms of whether or not the codes are gonna accepts this. There’s no possibility that the IRC is going to accept ASHRAE standards 62.2 in its current form because of all of the problems with part low humidity and ove dryness and actual practical issues of providing this flow rates. There is gonna have to be significant change if you’re gonna see coded option by the IRC. Having said that, that doesn’t mean that ASHRAE 62 can’t become basically the standard in certain states, it’s already been adopted, for example in California which, by the way is paradise from mechanical engineering perspective and construction perspective. I don’t see it being adopted in Illinois and it’s certainly not gonna be adopted in Florida but that doesn’t mean that your also can -- can’t have programs adopting it. Such as LEED or EnergyStar. I think that there’s gonna have to be some movement on all people’s parts on all sides in order to see that standard move forward and see more wider acceptance. But to change the rates based on climate conditions is a band aid for a standard that isn’t workable at this point in time.
Gail: Thank you. Here’s another question for Sean, where the tracer gas test conducted to determine the -- those air flow patterns from apartment to hallways to neighbors?
Sean: Well, they weren’t tracer gas test they were – we just measured pressure differences over time so we use data loggers measured pascal differences between – between the different zones so each department had a pressure sensor across the exterior window and then one across the corridor door. And we did this in several buildings so if you just do some addition you know that the pressure in the corridor is basically the same length of the corridor so if it’s a plus 5 in 1 apartment, and with respect to the corridor and its plus 4 in another apartment, with respect to the corridor then you know there’s a pressure difference between apartment A and B of one pascal. So that’s how we make those measurements.
Gail: Okay Sean can you talk a little bit more about the aerosol process. How long does it take or how much does it cost?
Sean: Sure. Well we spent a lot of time trying to figure out how much cost and we still don’t know it’s – I’ll have to actually defer to Mark Madera and Curtis Harington at UC Davis for more info, its really their projects were just lucky to get them to come out here and try it on one of our buildings. We hope to collaborate in the future but, it is just we just did 4 apartments with them so those 4 apartments it took us sometime to set-up especially our data loggers and then our tests we did sound transmission measurements between apartments and lots of pressure test and diagnostic. So it’s a very, very cool process and very interesting for a research tool actually. But as it is right now it takes a while to set-up so you have to – you need an air compressor, you need a pump for pumping the sealant, you need hoses, compressed air hoses, you need nozzles after close up the entire apartment protect surfaces – we did this in very rough stage construction apartments so those air flow rates were they got down to less than 0.1 CFM 50/ft2 when there was – it was just dry wall and there was no outlets, no baseboard, no floors, no nothing basically. So this is done in a very early stage of construction when it doesn’t matter if you get this sealant dust on the floor which is kind of sticky. So it’s very cool process right now it takes a while to set-up and I think part of their ongoing research is to refine how they do the process so its gets faster and faster. And the idea is to be able to use something like this as a contractor since it takes some set-up time you could maybe set-up in one apartment and do 4 or 5 other apartments just do them 1 by 1, one day so maybe it would take, we were estimating something like 4 man hours per apartment. But if you consider that from a very basic level of air ceiling which gets you just under 0.3 CFM 50/ft2 to very compartmentalize apartments, 4 man hours is quite a bargain. So were excited about it and we hope that we get to collaborate with them in the future.
Gail: Thank you. And now I have a few questions for Joe, can a balance system operate intermittently and still be effective or compatible with multi-family buildings?
Joseph: Yes. What’s nice about balanced systems is this since they don’t affect the pressure in their individual compartment, they won’t affect the pressures in the neighboring compartments it’s as if the compartments don’t know that they’re beside one another. And so intermittent balance ventilation certainly is compatible, the question is, is what’s the off on time sequence because at some point you’re gonna have to increase your intermittent flow rate in terms of the contaminant capture and removal. ASHRAE 62 has got a nice way of dealing with that and so there’s a technical way to allow that or accept that, quite frankly that’s -- right now with an HRV and ERV that’s the only way that we can really do it simply because the units are so large, they’re providing way more flow and then you actually would need in most of these apartments so half- time operation or 30% operation or 20% duty cycle is not unusual for these types of systems.
Gail: And one of the attendees had a question on slide 11, the image of the building with inlets and outlets. Those are close to the windows, how do we avoid exhausted air coming back through an open window?
Joseph: We don’t, there will always be some entrainment but it’s not particularly significant. That’s been shown with trace gas or by lots of folks unfortunately, I can’t think of any reference at this point and so those folks are gonna be irritated in need for not remembering but, yes there will be some re-entrainment but in the grand scheme of things it’s minor compared to all of the other issues that were struggling with.
Gail: Okay, why is it that the kitchen needs 75% make up the air from below and 25% from general space. What’s standards specified that?
Joseph: Well there’s no standard it’s basically engineering experience and judgment. The rational is to have a region of negative pressure at the cooking surface, if you just have a complete balance you’re not gonna have this zone of negative pressure. The physics of this, the practice of this is explained in ASHRAE applications so the ASHRAE applications handbook shows this; it’s not a standard it’s just -- there it is, there’s the testing that was done. This is done I believe by the California Energy Commission and it’s a fabulous piece of work, I urge people to read that section on commercial kitchen, demolition design and then downsize the thinking for residentially. And its somewhere between 60 and 70%, this seems to be working from the smoke tests that we’ve been doing and some of the custom home designs, that when we get the chance to actually have a unlimited amount of money and we actually get to control or have some impact on the aesthetics and systems in these high end houses.
Gail: Okay and then a final question, if I have no choice on how to run my exhaust up to the roof, how can I minimize the issues? In the same vein, can I bring my supply down from the roof? What do I have to consider when I do this?
Joseph: If the duct work is ultra-tight and the connections are all in it where ducts penetrate the floors are also ultra-tight you can get very, very good control. This was shown I guess with a lot of the compartmentalization were contesting that I think Sean’s group talked about or are already has done. So it’s more difficult to do but it’s achievable and you basically wanna have very high precious in the ducts to provide control, because you’re fighting the stack effect seasonally.
Gail: Okay, that’s about all the time we have for questions today. Panelists before we take our quick survey, do you have any additional or closing remarks you’d like to make before we close the webinar?
Sean: This was great.
Joseph: Thank you and thank you for allowing us to participate.
Gail: Well, thank you again to the panelists and now we’d like to ask our audience’s answer 3 short questions about today’s webinar. Your feedback will help us to know what we are doing well and where we can improve. The first question asks whether the webinar content was useful or informative. To answer click on the radio button right and there go to webinar panel. And the 2nd question asked about the effectiveness of the presenters. And the next question, asked whether the webinar met your expectations. Thanks for taking our survey. Stay tuned for the next Building America webinar on October 23rd which will begin our series on high performance space conditioning system. There is a meeting page on the Building America website to register. On behalf of the Building America program I’d like to thank all of our expert panels today for their time today and our attendees for participating in today’s webinar. We’d had a terrific audience; we very much appreciate your time. Please visit the Building America website to download the copy of this and to learn more about the program. We also invite you to inform your colleagues about Building America resources and services. Have a great rest of your day and we hope to see you again at future Building America webinars. This concludes our webinar today.