Gail Werren: Hello, everyone I am Gail Werren 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 presenters from two Building America teams here today to tell you about Retrofitting Central Space Conditioning Strategies for Multifamily Buildings. Our presenters will discuss hydronic heating methods and the evaluation of thermostatically controlled radiator valves or TRVs. Before we begin I’ll quickly go over some of the webinar features. For audio you have two options, you may either listen to your computer or telephone. If you choose to listen through your computer, please select the mic and speakers option in the audio pane, by doing so we will eliminate the possibility of feedback in echo. If you select the telephone option, a box on the right side will display the telephone number and audio pin you should use to dial in.
Panelists we ask that you please mute your audio device while you are not presenting. If you have technical difficulties with the webinar and you may contact the GoTo webinar’s help desk at 888-259-3826 for assistance. If you would like to ask a question, please use the questions pane to type in your question. If you are having difficulty viewing the material through the webinar portal you may find a PDF copy for the presentations at the website listed here and you may follow along as our speakers present. Today’s webinar is being recorded and the recording will be available on the daily YouTube channel within a few weeks. We have an exciting agenda prepared for you today that will focus on improving the performance of space conditioning systems in multifamily buildings. Before our speakers begin, I will provide a short overview of the Building America program. Following the presentations we will have a question and answer session, closing remarks, and a brief survey.
The U.S. Department of Energy’s Building America program has been a source of innovations and residential building performance, durability, quality, affordability, and comfort for nearly 20 years. This world class research program partners with industry to bring cutting edge innovations and resources to market. Building America is supported by 10 industry research teams and four national labs, each of these teams and labs partner with dozens of industry professionals including builders, remodelers, manufacturers, and utilities. The best and the brightest in the residential buildings industry can be found here. Building America uses applied research to deliver building science solutions using a four-step framework. These innovative solutions are tested in homes to develop proven case studies of success for the market to point to. Building America provides the tools the building industry needs to ensure the innovations are applied correctly, always keeping an eye on energy performance, durability, quality, and affordability.
The final step, infrastructure development is the conduit to getting innovation to the marketplace. Building America research focuses on how the components of new and existing homes work together through system integrations. As the market changes and evolves so has the direction of our research in order to add value, drive changes and performance across the residential building industry. The addition to technical challenges we have been adjusting for decades, there is now a need to understand market transformation issues such as valuation of energy efficiency to our portfolio. In the nearly 20 years of Building America research, we have spearheaded combining ultrahigh efficiency with high performance in those new and existing homes and we are consistently achieving this challenging task. For example, in 1995 a typical home used three times more energy per square foot compared to today and the indoor air quality converts and durability problems were common.
Today a home built to DOE zero energy ready home specifications uses less than half the energy and are comfortable, healthy, and durable. By 2030 Building America will demonstrate that new and existing homes can produce more energy than they use. Do you want to know more about these proven innovations borne out of world-class research? The Building America Solution Center is your one-stop source for expert information on hundreds of high-performance construction topics including air sailing fan insulation, HVAC components, windows, indoor air quality and much more. You can find us by the URL on your screen or by searching on Building America Solution Center.
Now on to today's presentation: today will focus on improving the performance of central space conditioning systems in multifamily buildings. Presenters will discuss hydronic heating strategies and the evaluation of thermostatically controlled radiator valves.
If you would like more detailed information about any of these efforts or if you're interested in collaborating, please feel free to contact any of our presenters. Our first speakers today are Jordan Dentz and Hugh Henderson and represent the Building America team, Advanced Residential Integrated Energy Solutions. Jordan is the Vice President at the Levy Partnership where he develops and manages building science research projects and consults for building owners and operators. Hugh Henderson is the founding principal at CDH Energy where he researches technologies such as combined heat and power, cooling and dehumidification in residential and commercial buildings. Today, Jordan and Hugh will discuss various control strategies to help improve hydronic space heating performance in three low rise multifamily buildings in Cambridge, Massachusetts. In addition, Eric Ansanelli is here to present with Jordan about research results of the effectiveness of thermostatically controlled radiator valves.
Eric is a mechanical engineer at the Levy Partnership where specializes in steam heating systems.
Representing the Building America team Partnership for Advanced Residential Retrofits are Peter Ludwig and Russell Ruch. Peter is Director of Building Retrofits at Elevate Energy in Chicago where he works to develop energy efficient housing for building owners and renters. Russell is the Senior Energy Analyst at Elevate Energy and explores energy efficiency strategies for retrofitting multifamily buildings. Their presentation will focus on three studies that identify those packages, costs, and savings associated with retrofitting, overseeing and hydronics multifamily buildings. They will especially focus on the process of balancing these buildings through increased mainline air venting, increase circulation cost efficiency and upgraded boiler control system. With that I would like to welcome Jordan to start the presentation.
Jordan Dentz: Thank you Gail, this is Jordan. How about I start by talking about why this topic is important. First of all there’s quite a large number of homes in the U.S. with space heating provided by steam and hot water, approximately 14 million and in many of those homes because they were in the northern climates, space heating is the largest energy use, I want to point out this study pictured on the screen, was published last year and on the Building America website and it documents the extent of overheating in a sample typical New York city apartments. I’m just going to give you one of the results from the study, over 100 apartments in 18 buildings were looked at an extent based on true data was examined. Almost all were overheated most of the winter and this was true for both steam and hot water. While energy management systems reduce the overheating in many of these departments it did not stop overheating in most of the buildings. So this is the presentation we’re going to talk about first is the three buildings in Cambridge that Gail mentioned and I would like to turn it over to Hugh Henderson to discuss the next few slides.
Hugh Henderson: Okay, thanks Jordan. In this field test what we wanted to do was compare traditional boiler controllers and look at the impact of all types of strategies and see how they affected in energy use. So for years people have basically reset the supply temperature per boiler based on outdoor air conditions and so that's one of the things we looked at. There are also new technologies to use things like wireless-based temperature sensors to look at the space temperatures then cut off the boiler based on that. Along with boiler reset strategies, there are also nighttime setback strategies that can be used where the supply water temperatures sent out to the building might be lower at night. So we were looking at all three of these strategies and we're looking at the way they have been done traditionally and how they've gotten better with the newer controllers that have come out and also the newer technologies like wireless.
So the next slide Jordan, our site was a three building complex in Cambridge, Massachusetts, it had hydronic heat. There were three buildings: they were building four, building three, and building 55 and so some were behind the street and some were at the face of street. They had from 9 to 18 apartments in each building. They all had Weil-McLain boilers; each building had two or three boilers. There were TRVs on many of the radiators that they had essentially fell so when they fell they fell open so there's basically no control. They all have some kind of a reset controller though some were very old-fashioned. So what we did is we replace those and we took out the old-fashioned ones and putting better ones and we also put in the wireless sensors and controllers that could take advantage of that, so the next slide Jordan.
I'm going to talk about first site four building and then Jordan's going to talk about three and then will come back to building 55. So the setback strategies at the building originally had, building for had a newer controller and really all we did was change the parameters for the outdoor air research strategy so the blue line shows what the strategy was when we first arrived and the green line shows what we changed it to. So what we essentially did was we lowered the minimum supply water temperature that the boiler could provide. So the supply water temperature had gone up to 180 when it was 10° outdoors and then he decreased to about 130 by the time it was 48° then we never allowed the supply to go below 130. We had essentially the same thing when we installed the new controller but it went down to 110, so next slide Jordan.
So we looked at lots of behavioral things but here is sort of the bottom line look at the monthly gas bill. So we made a very modest change to the setback strategy or to the boiler reset strategy for this building and so you can see the two lines here, what was there before we arrive is the red data, 2010 to 2011 data. So the new controller showed green and so the straight lines are a little misleading and of course most of the difference is in the mild conditions with the setback strategy and so we did see a noticeable change.
On building 55 where not showing that data here. We also saw we had a bigger change in our reset strategy and I needed more savings but this kind of shows you the idea and we set this data to a change point model and in this particular change point model we've taken out the water heating data so the wire set is zero actually but obviously there's always gas use associated in the building with water heating and then gas use is associated with space heating, so the next slide Jordan.
The results are--so we also placed a lot of Hobos in the various apartments in this building in kind of a theme that Jordan mentioned and you're going to see I think in a lot of this is space temperatures and a building from unit to unit can vary on (Audio Stops 14:30)
Jordan Dentz: Hello Gail, should I pickup from here?
Gail Werren: Yes please.
Jordan Dentz: Okay, Hugh must have dropped off or something so I'll pick up from here, this is Jordan again. He was mentioning space temperature varies quite a bit from unit to unit overtime, over the season. It is about seven apartments or seven centers in that building. The bottom line though is that heating energy with a change in the boiler reset control decreased by 10% and indoor temperatures are still well above 70° throughout the season and the actuality is there is room to reduce it even further here as you can see by the temperature data. We do have some data from the other building as well in which case there was an even older original reset controller and a change here produced a more dramatic savings, some of the graphs the reset curve on the left you can see was changed more dramatically. The original loop reset line was quite a bit higher than the other buildings and we brought it down to a level similar to the curve that was in building four, in here we saw a 15-1/2% energy savings.
So now I'm going to move onto building three which is a study of the indoor temperature cut off and in building three we installed the system also, sometimes called an EMS system or Energy Margin System and it cuts off the boiler when the average space temperature exceeds a set point and in this case the set point was 73° in the day and 68° at night. When that set point was not exceeded the outdoor reset control was in effect. We had one temperature sensor and every apartment in this case. We operated the system over the course of 1-1/2 heating seasons alternating periods where the indoor cutoff function operated or it was enabled and periods where it was disabled. We have about six months of data under each case. Six months where it was enabled and six months where it was disabled and during that time we were tracking the boiler run time hourly.
You can see on the right here of the table showing the average space temperature, during the heating season and it decreased by about half a degree when the indoor cutoff was enabled so not a huge impact on indoor temperature at neither day or night on an average basis. However we did find that at night with the indoor cutoff enabled the boiler hardly ran at all and this is the load line showing the weekly periods using nighttime data only, green is with the indoor cutoff active so quite a bit lower boiler run time. As a matter of fact 71% lower during the night, so during the day the indoor cutoff produced boiler on time by 1% but at night it reduced by 71% an overall reduction that's 28%. These numbers mirror closely at the percent of time that the indoor cutoff mold was active that is when the boiler was overridden.
Our conclusion from this are that number one that outdoor reset which probably is set reasonably well for daytime because the temperature was not exceeded, did not exceed the set point often. Also the indoor cutoff was effective at night time however it's possible that readjusting the curve downward for nighttime might have achieved similar savings without indoor cutoff. That we have not attempted. I'm going to turn it back over to Hugh who I think is back on to discuss the nighttime setback results. Hugh, are you back with us again?
Hugh Henderson: Yes I am, yes thanks. We also looked at the concepts of nighttime setbacks so that's basically taking the outdoor air reset strategy and having it all drop by 5° at night so the graph actually shows the blue line shows the nighttime setback and actually do lines should not go below 100 but we basically shift to the right so the blue line is shifting to the right of the green line and we tried this with a 10° drive at night and then we had some service that might be affecting the comfort of the occupants so we changed it eventually to a 2 and 5° setback at night. Can we go to the next slide Jordan?
We toggle back and forth and try these strategies and you can see the schedule of what we did here throughout 2012-2013, go on to the next one Jordan. What we saw a really was nighttime setback really did not have much impact so we couldn't discern an impact or difference in gas use so we are kind of a believer that the-- and we're also concerned about the nighttime setback.
It's an apartment; people have different schedules in the building so it probably is better to kind of have strategies that don't change in terms of time to do things in terms of temperature in the space and outdoors is the kind that Jordan has talked about, so the next slide Jordan.
Yes oh, kind of take away that Jordan and I can do this so basically we found that the outdoor reset has been around for a while and the parameters matter and one kind of practical thing we found is that you know these controllers get installed but often the parameters they get put in there are somewhat arbitrary and can be disabled across time and so it's really important to have these outdoor reset curves set to kind of a reasonable level. As Jordan has shown the indoor cutoff or to take information on space temperatures with the wireless sensors can be a pretty effective strategy. Nighttime setback we weren't as impressed with the impact that we saw with that he really didn't seem to be really effective. Do you want to say anything else Jordan?
Jordan Dentz: No I think that covers it, thank you.
Hugh Henderson: Okay.
Gail Werren: Next up is Peter and Russell.
Russell Ruch: Hi this is Russell Ruch and Peter Ludwig.
Peter Ludwig: For Elevate Energy.
Russell Ruch: Yeah, just want to thank Gail and Heather for setting this up. So we both work for a nonprofit program called Elevate Energy based out of Chicago and our buildings program is focused around being sort of a one-stop shop for building owners that are interested in doing energy efficiency retrofit, sort of guide them through the process of energy audits to presenting them with a rapport with cost-effective recommendations, helping them with financing, construction oversight, and then ongoing savings monitoring and reporting each retrofitting over 17,000 at this point. We are one of the organizations that are working with GTI on PARR the Partnership for Advanced Residential Retrofits and were going to be talking about a couple of the studies we've done as part of our work with Building America.
Peter Ludwig: To sort of set the stage over half of cold climate multifamily units are a unit by Central Steamer Hydronic Systems and around Chicago at least two thirds of the residential units were built before 1980 so they're rarely designed for energy efficiency and in our cornerstone heat and energy counts for majority of residential energy use so many questions are how to cost effectively retrofit and optimized use and they are seen in hydronic systems so they use less heating fuel.
It's going to be helpful to sort of go through a bit of a primer on how steam works before telling us how we can optimize these systems when they go into homes. Being with the best options for buildings constructed around 1900-1930 and there’s a lot of buildings in Chicago at least from that era that still have steam systems that have been converted in cold and natural gas and they have their boilers replaced but their distribution systems are largely saying they may not present for efficiencies. Basically the way they work is the control calls for heat, the boiler kicks on, heats water, generates steam. The steam moves through the main line pipes which are initially filled with air being the metal, the radiators, and pushing air out through vents from the mainline to the radiators and then demonstrating other steam defenses and releases its heat around more steam to enter as the building is heated according to the set point temperature where it shuts off, the radiator’s cool, the air vents open and allow air to reenter the system. Having those vents on the radiators and the main lines open and able to allow air in and out the system is very important for allowing steam to flow through the building. Here's just some pictures of how that looks in the boiler room and you can see basically the boiler coming on, starts out cool and then about a half an hour the steam has reached the mainline vent and heated up and that's how this looks in the radiator. You can see the steam sort of traveling through the radiator over time and again it's crucial that the vents be opened for that to work.
Here are some common scenarios we see in these older multifamily buildings that are preventing steam getting to the system easily. You'll see painted over radiator vents, rusted mainline air vents or rusted or blocked, and then often times the boiler will just be run on a timer which tells the boiler basically to come on during certain parts of the day but isn’t controlled necessarily by the outdoor/indoor temperatures suggesting these things are going to be a big part of what we (Inaudible 27:06).
As Jordan and Hugh touched on a lot of these buildings are overheated, usually what's going on in some units are under heated for various reasons and then the set points for the timer to set so that the boiler is heating the entire building hot enough so just those units are satisfied but that constantly causes a lot of other units to be overheated which obviously costs a lot heating and fueling it and costs money. It also is a big cause of tenant discomfort so basically what were looking at for utility savings and tenant comfort issues and were talking about balance.
Unfortunately there are some market barriers, this is a thing that we have to address and that sort of what our study was originally written to identify and address--there's really a lack of knowledge about how these things work in the marketplace. Often not offered as a service by contractors or recommended as a measure. A lot of utilities don't recognize it as something which saves energy. It is not really a very easy plug-and-play sort of retrofit. You have to spend some time looking at the steam loops, timing them and seeing where the issues are, sort of considering the configuration of the building and the loops throughout the building.
All those reasons it can be difficult to convince of the value of doing it; separate issue from boiler replacement and then of course if there’s a perennial problem with natural gas that it's relatively cheap so it’s not always considered worth time, or effort. So this is our study we want to figure out how steam balancing measures would affect temperatures in units, how the boiler cycle and the overall gas consumption of the building and we did that by installing hobo loggers in 10 steam buildings and then taking a look at their performance before and after retrofit.
On average we found about 10% savings off the heating load from doing steam balancing measures at an average cost was about $9800 with the payback of 5.1 years and the measures we were especially looking at were replacing radiator vents, adding or improving the mainline air venting and then improving the controls so we would be replacing timers on boiler systems with those indoor averaging tools that ideally had sensors in about a quarter of the units or more. And here you can see the results from that study and natural gas use for the 10 buildings. Eight of the ten buildings natural gas use dropped as a result of the measures. You can see the spread of temperatures really decreasing after retrofit and basically we had sort of three big conclusions in general that's steam balancing. One it is an iterative, multistage process. You really have to have a conversation with the building manager and the tenants and really take a close look at temperature data before you start swapping out vents or—yeah or, considering resizing risers or header piping. It’s really important to consider the building layout, the piping configuration, and the location of the units which are over or under heated, and again, the cooperation of tenants and building managers is really crucial. It’s really important to explain to tenants how impacts of using space heaters will drive up temperatures of their units, and interfere with the indoor temperature averaging systems which control the building and of course, building managers should be properly instructed on how to use those controls once you put them in because they are a bit more complicated than just the timers. Also in our steam balancing study we tried to do a similar approach with hydronic buildings and we could see how much of an issue imbalance was in hydronic was and what sort of measures we could use to address that. So we wanted to take a look at the temperatures both in the units and across the building and think about what sort of cost effective balancing strategies we could have.
Part of the study was surveying the literature and then we chose two test buildings where we installed hobo loggers added pump capacity other buildings. We found really astounding results in one building where there was an instantaneous temperature spread of 48° and we were able to produce the average spread in the building over the heating season by 6 ½ degrees. Just to give you sort of a sense of the balancing issues in the building here this is test building A. The boiler is right in the middle there and there are two loops going into the West and East portions of the building. This was originally a steam building that was converted to hydronic in the 1990s when they did the project they unfortunately undersize the pipes so there was really a chronic under heating issue in those west units, 56-57 down to 56-53 and our retrofit was to increase the pump capacity and see if that would improve the under heating and those units.
There was already a temperature averaging control system that had I think eight sensors throughout the building but unfortunately because some of the units were under heated, tenants were resorting to supplemental heating sources which again was interfering with controls and causing the boiler to kick on and off less than it needed to. Here's the temperature data we collected with the hobo loggers. It was some really extreme temperature peaks and we believe that those occurred because of supplemental heating sources like oven ranges in those units and while that wasn't eliminated entirely after installing the pump you do see those go down and the average spread also decreased. Here is an example unit you can see some of the extreme temperature spikes before retrofit and then the last one in afterwards despite – sorry, the top line is the indoor temperature and the bottom line is that outdoor temperature. We really saw improvement in the balance of temperatures before and after retrofit.
There were, 17% of the time the building had attempted spread of over 30° for retrofit. That decrease greatly down to about 1% and about 25% of the time before retrofit the building spread was under 15° but increased greatly to 52% after retrofit. The other building we looked at as part of the hydronic project was 1960s two-story building that had under floor radiant heating and each unit is zoned with a thermostat. That was interesting to see that there was an overheating issue on the first floor despite there being unit zone controls; some of the units weren't able to really bring the temperatures down in their units despite having their temperature set at say 65°, the beginning temperatures at 75. Here is a table that sort of summarizes that you can see for example in unit four which is on the first floor they had their set point when we came at 60° and the actual temperature reported was 83° so this was just really interesting to us in terms of collecting very high quality, high resolution data with HOBO Loggers that sort of showed a real balance issue in hydronic buildings.
There's something we knew about with steam buildings but it wasn't so well-documented in hydronics. So again our conclusion sometimes study sort of in general where that hydronic building can be extremely imbalanced, unit temperature can range by as much as 40°. That can be cause by open windows or intermittent supplemental heating sources and again as a steam when there are zones serving multiple units you know not zone by unit there is bound to be significant variation in temperatures throughout the building.
Even in buildings where essentially there's zone control for each unit as a second building we looked at you can add variations from the set point better pretty considerable. Causes of imbalance in hydronic are a lot more diverse than steam and have issues with undersized piping, undersize circulators, zone valves that aren’t functioning, damaged heat emitters, balancing valves that aren't configured properly but still many of the same lessons from steam balancing applies so it's really an interactive process where you have to consider carefully the loop configuration from the layout of the building and again communication with the tenants and the building owner is really crucial. Being able to have active cooperation you need to balance building and, that’s it.
Gail Werren: Thank you Peter and Russell and Jordan and Eric will be up next.
Jordan Dentz: Alright thank you this is Jordan again. This presentation is on the thermostatic radiator valves evaluation study and were going to review briefly some past research on TRV effectiveness and talk about how TRV's work and present the results of the field test and evaluate the effectiveness of TRV's on a steam heating building with contractors and then also discuss the impact on heating energy use for building that underwent a TRV retrofits. So some background, as we’ve been discussing many central units, steam and hot water buildings there is imperfect distribution resulting in wide temperature variations in some apartments. The heating systems force to supply a minimum amount of heat or temperature to the coolest apartments and other apartments become overheated. So thermostatic radiator valves or TRV’s offer a possible solution by controlling heat admitted from radiators based on the temperature in the room however, in our experience in research implementation of TRV’s and existing multifamily buildings is somewhat spotty because of cost and also lack of confidence among some and their ability to deliver energy savings.
Published independent studies demonstrating their effectiveness is not wide spread with at least one notable exception I’ll discuss. But first here’s a TRV its for a one pipe steam system which is what was used in our study, consists of a valve body, a thermostatic operator that senses the temperature of the room and an air vent. With the TRV in place, when the room reaches set point the valve closes, preventing air from escaping through the vent and thereby preventing new steam from entering the radiator. Eric will talk a bit later about the implications of this cycle with convectors. So as I mentioned we only found a few studies, field work and field evaluations of TRV’s even though TRV’s have been around for many years, 50-60 years or longer, some are surprised at this. This is a list of the studies that we were able to locate, the most notable was an extensive 1995 study sponsored by the New York State Energy Research and Development Authority or, NYSRDA, in which TRV’s were installed in a number of buildings using one pipe steam primarily and most of those we had standing radiators.
Our study determined that they were saving about 15% of energy after preventing (Inaudible 42:00) measures. Most of these other studies are either modeling or not specific to one set point pipe steam implementation. Despite that one research study there’s a range of opinions in the market in our experience and so we decided to talk to a number of people in the industry about their perception of TRV’s and found a wide range of opinions so everything from we swear by them to we don’t believe they work by steam and this was from engineers and others who were active in the industry. Some other common themes included the perception that steam cycles caused TRV seals to fail early and that apartment level control provides basically a psychological boost but there’s not much change in temperature with TRV’s. So the next step that we decided to undertake was a small field test to look at some of these issues in the real world. So I’m going to turn the presentation over now to Eric and he’s going to discuss this field test.
Eric Ansanelli: Thank you Jordan. So the main objective for the experiment was to get detailed space temperature and radiator temperature data at the apartment level both before and after TRV installation and from this determined if the TRV's would operate as expected and if they were controlled space temperature well. A second objective was to test old TRV’s alongside new ones and see if there’s a performance difference. On this case the valve bodies that we use for the older TRV's had already been in service for a number of years and is different installations and the sensor and thermostatic operators were previously unused. They were older and they've been moving parts that while on the packaging still the most subject to normal space temperature fluctuations. The apartments that we experimented with had singular layouts orientation, size, distribution systems as I said is one pipe steam with convector and the TRV had been installed over the preceding summers throughout the building but these two apartments received their TRV's in mid-January so we did collect pre and post installation data.
As Jordan mentioned specifically with one pipe TRV’s there's a key difference in the application versus the two pipe steam system. With two pipes steam the TRV can go at the radiator inward and has allows it to block the steam entirely from entering the radiator when the TRV is closed. But with a one pipe TRV application the TRVs are installed with a vent inside the radiator partially because of debris and clogging issues at the inlet and also because of lower costs associated with smaller fittings and easier access at the vent end. So a one pipe TRV in this position can work in either of two ways, one if the space temperature has already satisfied the sensor and the TRV is closed before steam cycle begins, it can prevent the entire volume of air in the radiator from exiting the radiator body the cycle runs and no heat is going to be added to the space or two if the TRV is opened up at the beginning of the steam cycle it closes when the air has only been partly displaced from the radiator body in this way they can effectively limit the volume of that body that received steam over the duration of the cycle.
You can think of it effectively as a smaller radiator. So the factors listed here on the slide govern those two competing time frames that have to overlap in order for a TRV to limit heat added to the space in the second scenario. Once the steam cycle begins the TRV sensor has to actually develop in a shorter time span than that in which the air is displaced with a large cast iron radiator that can take 8 to 10 minutes for it to fill completely with steam. With convectors as we have in this building they're going to fill in two minutes or less so the manufacturer of the TRVs recommend venting the steam mains and rises aggressively and using small air vents on the radiators themselves so that the fill time can be extended to as long as possible giving TRV more time to respond to the space temperature and the pressure at which this steam is also going to effect that fill time a little bit so the TRV has to have in less than 10 minutes for a cast iron radiator and less than 2 minutes for convectors. So this is sort of a toughest case scenario that were using TRV's on one pipe steam and with convectors and just going back to that last point of the TRV reaction center depends a little bit on the rate of route expansion of the sensor material but even more on the establishment of the convection current and where the sensor is when it gets in that current. Lastly the set point, the TRV might well be a little different from your desired space temperature.
So this graph shows the data that we collect to just give you an idea of what we’re looking at, this is for all six sensor channels over a two-day period in January. The blue one at the bottom is the outdoor temperature and you can see that bottom trough in the far right that's the polar vortex that we experienced this winter space temperatures is the orange line that extends approximately this kind of mid-60s or mid70s in the apartment for the time. The blue, red, and green lines respectively, those are indicating the temperatures of the radiator inlet, midpoint, and valve end.
So from left to right you can see how during that evening of the sixth, the boiler doesn't run and then there’s a regular hourly cycle for the course of the next day. At the beginning of the seventh there's a long morning boost cycle that you're looking at a thing you see this cycles are a little bit--they are a little. They are a little you know the bands are thicker so the cycles are longer on the seventh because it's a much colder day which is what we use that. The purple line lastly that's been near window temperature so you can see what looks like a window opening event where it drops suddenly it's erratic. They are on the sixth and the shorter one on the seventh. So let's take a look at the results.
Here you have space temperature averages for each room in two apartments both before and after TRV's are installed and there are a few things worth noting here. One, note is desirable to consider space temperatures for this when the tenant have their windows closed so we filtered out the data where the near window temperature was below 55°. In apartment 1F actually noticed that the tenants were opening the windows much more frequently and that might have mitigated the impact of the TRVs there somewhat. Also the kitchen, they are weighted equally here with the rooms even though they have much higher internal loads and relatively small square footage. And lastly, the apartments they weren’t incredibly overheated before hand, and this raises the question , are TRVs meant to achieve temperature control down to one or two degrees, or are they are better used in applications where the goal to limit more severe overheating. The next few slides I want to show you, other aspects of the heating system performance that we kind of kind of uncovered through the data that may also affect the results.
These temperatures show average post TRV installations based temperatures that occurred when outdoor temperatures were relatively mild and that between 35 and 50° here and when they were severe which was between 10 and 25°F alongside standard deviation for each of those subsets.
What you were looking for was to see perhaps if space temperature swing will be greater in one case of other and that would be due to the TRV performance but what we saw and what we might be seen here is that it might be that the slope of the outdoor reset boiler controller wasn't matching the rate of heat that was expanded by the building in mild atmosphere, cold. The couple that sleeps in the master bedroom in apartment 1F they complain specifically that both before and after the TRV's were installed on very cold outdoor days they were cold in their bedroom.
Furthermore, you noticed that the space temperature swings kind of represented by the deviations were nearly constant within the apartment from mild to severe cold outdoor conditions but they vary between the two apartments and again that might have to do with the tendency of tenants in one else to open their windows more often. Next slide.
This graph shows the data for one room, the living room in apartment 1F for few days immediately before and after TRV installation and you can see in the days leading up and this is the case for the entire heating season before we install the TRV in this apartment, in this unit, in this room that the radiator never really got hot, where as soon as it was installed you can see consistent heating cycles and this could very well have to do with the replacement of the air vent that happened at the same time the TRV was installed. It may be that this apartment, this room wasn't getting heat until it happened indicating some imbalance.
In the next slide were going to look at the gap heating bills for property for the entire building over the past two winters to get an idea of how the building lacked TRV installation affected fuel consumption. So this graph shows terms of space heating per day against average outdoor temperatures for the corresponding bill periods. Orange represents the winter before the TRV's were installed and the blue is that first winter with the TRV's in each apartment. Basic load usage were approximated by non-heating season use and then subtracted out to just yield heating fuel consumption here and you can see that the data points are very close and it doesn't really indicate from this that they are using less fuel.
So our conclusions are at the building wide level we’re not seen a very measurable fuel savings at the apartment space temperature level it's somewhat ambiguous with 1A gaining a few degrees, lowering a few degrees of space temperature and 1F seeing the opposite. The possible reasons for this might include that the distribution venting may need balancing or the venting may be inadequate and that was not done before the studies was implemented. The boiler outdoor reset curve on the heat timer that controls the boiler for this building was setup ‘I’ for and after the TRV's were installed so that wasn’t adjusted and maybe that needed to come down while the TRV's were installed and the tenants are still--the behavior hasn't caught up and they are still opening windows very regularly.
Also not listed here but we talked a little bit before about -- with one pipe steam and with convectors especially the TRV's have a very limited window of time in which they can respond to space temperatures. That's a tougher scenario for them to perform. That's our results. We will be holding a one-day meeting in New York City later this year to present and discuss findings from this and other related research on multifamily central system retrofit. Please contact us if you're interested in attending in person or on the web and thank you.
Gail Werren: Thank you to the panelists for those outstanding 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 through the questions pane on your screen. The speakers will answer as many as time allows so we have a few questions targeted to Jordan and Hugh’s presentation. The first one is, could the nighttime setback have been made effective if it was set more aggressively?
Hugh Henderson: Yeah so this is Hugh, I guess I’ll take that one. Yeah so we did try a ten degree reset back for a while and we –hello everybody can still hear me? So we did try a bigger setback and we were concerned in that building there was some tenants that worked the night shift or had an offset schedule so they were up at night and we had a little bit of feedback that there might have been a problem so that’s why we had backed off on that. Jordan do you have anything to add?
Jordan Dentz: No that I think covers it.
Gail Werren: Okay and then the next questions for you two is, are the boilers in building four condensing or non-condensing? This audience member was worried about a non-condensing boiler operating with return temperatures lower than 130°.
Hugh Henderson: Yeah so it turns out that in building 55 they were both non-condensing. In building 55 they did have a bypass valves that held the temperature higher. On building four we were also concerned about that and after kind of monitoring things and working with the onsite contractor who was in charge of the building. We kind of came to a mutual conclusion that we were going to be okay and (Inaudible 56:4) but that is a concern that a non-condensing boiler you shouldn’t go below 130. Jordan you have anything else to add to that?
Jordan Dentz: The only other point is that the boilers did have condensed A drains so that there was some anticipation by the manufacturer that they would experience some condensation.
Hugh Henderson: Yeah and I don’t believe we ever saw any evidence that there was consistent condensation so those drains of course are for startup but yeah we didn’t see any evidence that had been continuously a problem when we had it under ten.
Gail Werren: Okay thank you and then we have a couple of questions for Peter and Russell. Can you provide a bit more information about the logistics of steam loop timing?
Russell Ruch: Sure, let me pull up the slide here real quick. Can you kick the screen over to us?
Gail Werren: I’m sorry was that Russell?
Russell Ruch: Sorry can you have my screen be showing?
Gail Werren: Yes is that Russell or Jordan, I’m sorry?
Russell Ruch: Sorry this is Russell.
Gail Werren: Okay thank you, one moment please.
Russell Ruch: Thank you.
Gail Werren: There you go its coming back, thanks.
Russell Ruch: Great, thank you. So yes it’s time steam loops in which you would do in order to figure out which loops in the building are getting heated faster than other ones. The goal being to even them out so that the loops are more or less getting heated at the same time so that the loops that are getting heated more quickly are not overheating and the loops that are taking longer are not under heating. To do that you would need IR cameras, photographic cameras, stop watches, like a sketch pad for diagramming and then usually you’d want to do it having multiple auditors taking a look at multiple steam loops at once, assuming that you can’t do it all yourself in the boiler room so that would be in a case where the mainline vents are distributed around the basement and are not just all contained in one room.
Basically the procedure would be to have the building owner shut off the boiler before you get there and then walk around and diagram the loops and vents. Then you would have yourself or you and however many other assistants you have with you. Turn your IR cameras onto the mainline vents and taking photos as you turn on the boiler and sort of watch to see the temperatures increase and then you just basically use a stopwatch and time it until they reach 200°. Record the times for each and then compare, its a good diagnostics for figuring out which loops need more venting whether its placing the vent, increasing the size of the vent, or repositioning it and that’s basically your starting point for steam balancing. You have anything to add Peter?
Peter Ludwig: No.
Gail Werren: Okay thank you. There was another question for you two. Any use of buffer tanks in the hydronic based heating systems that were noted have lower temps?
Russell Ruch: I’m sorry was that question for us at Elevate?
Gail Werren: Yes, um-hmm.
Russell Ruch: Could you repeat it please?
Gail Werren: The question is any use of buffer tanks in the hydronic based heating systems that were noted to have lower temps?
Russell Ruch: I’m not sure exactly what they mean by buffer tanks, could you clarify? You mean an expansion tank for air?
Gail Werren: Yes.
Russell Ruch: Yeah the question is whether we replace the air tank? We did not, there was sufficient –the air tank was sized appropriately and was working in the hydronic building that we retrofitted with the new pump.
Gail Werren: Okay and then there’s a question for Jordan and Eric about the TRV and that is, how is the building performing before the TRV’s were installed compared to similar properties? Was it especially inefficient in terms of heating?
Jordan Dentz: Well we looked at for both before and after the average BTU’s per square foot for heating everyday and that was about ten BTU’s per square foot of heating per HDD which is not excellent so maybe you know average performing, a little bit lower than that and we don’t have building wide space temperatures, just for those two apartments but you know the overheating wasn’t egregious, but certainly present.
Gail Werren: Then there was another question for Jordan and Eric. Are there any research results on limit point landlord TRV savings?
Jordan Dentz: The TRV’s in this building were effectively limited because the controller was inside the radiator enclosure so its unlikely tenants were going in there to adjust that but they weren’t physically limited. If you wanted to you can go in and change that and I’m not aware of any research on savings as a result of specifically that. TRV’s that we installed in apartments 1A and 1F were locked to 3-1/3 on valves which is on the dial which correlates with about 70°. Don’t you want to add to that Eric?
Eric Ansanelli: No.
Gail Werren: Okay and then there was another question regarding TRV’s. Are there faster responding thermostat valves that would work better?
Eric Ansanelli: The variables that we were able to consider that I’m aware of include the sensor fill, you know what goes in like a pillar or two whether it’s a wax that changes phase or some kind of liquid or a gas; I think gas is the fastest and the response time is something I think in a second or something like that. You know the other variable is where the sensor is placed and the manufacturer recommended in this case that we put it at the bottom of the convector where it would be that incoming convection current and what actually happened in the building was the plumber installed for the other apartments that were not part of our specific test installed that sensor next to the radiator which may have –it might of experienced slightly cooler or warmer temperatures since they were a little bit higher up on the wall. That might have more of an effect than the response time of the sensor itself which is on the order of a second. That convection current might take a couple minutes to establish. I think that’s the place to look for you know if, we were going to do it again or try to improve this instillation as where the sensor goes in a room.
Gail Werren: Okay and another question for the TRV study, what pressure was the boiler running at? Is it possible that TRV’s were overwhelmed by pressure most are limited to systems with two PSI or less?
Jordan Dentz: A couple weeks ago I believe there were set, I’m pretty sure they were somewhere between two and four PSI and that is greater than what you’re saying at two. I don’t have a definitive answer, I think they were –I’m pretty sure they were higher than two PS –the boiler was set as higher than two PSI, that’s a good question.
Gail Werren: Okay thank you everyone and panelists before we take our survey do you have any additional or closing remarks you’d like to make?
Peter Ludwig: Well this is Peter and Russ, we just wanted to thank you again for organizing it and certainly if folks would like to talk more offline we’d be more than happy to do that and also just thank the folks from Levy Partnership and you for you know doing the presentation with us.
Jordan Dentz: This is Jordan, likewise, thank you for organizing it and it’s been a pleasure to be a part of the webinar.
Hugh Henderson: This is Hugh Henderson at CDH, we’re happy to be involved too, thanks.
Gail Werren: Well thank you for your participation and now we’d like to ask our audience to answer three short questions about today’s webinar. Your feedback will help us to know what we’re doing well and where we can improve. Heather will you please show the first question, okay. The first question asks whether the webinar content was useful and informative, to answer you can click on the radio button, right, and then go to webinar panel.
Okay, thank you. The next question asks about the effectiveness of the presenters.
The next question asks whether the webinar met your expectations.
Thank you for taking our survey. Stay tuned for the next Building America webinar on August 13th at 3 p.m. Eastern. This webinar continues our series on high performance building enclosures and it focuses on effective strategies to adjust moisture and thermal needs of building envelopes. On behalf of the Building America program I’d like to thank all of our expert panelists for their time today and to our attendees for participating in today’s webinar. We had a terrific audience and we very much appreciate your time. Please visit the Building America website to download a copy of the slides, 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 events. This concludes our webinar.