If you suspect that opening windows to let in fresh air might be good for you, a new study by scientists at Lawrence Berkeley National Laboratory has confirmed your hunch. Analyzing extensive data on ventilation rates collected, it was found that an investment in more outside air ventilation (offices or schools) pays off with more productivity and less absence showing an 8-1 payoff! A discussion on Linkedin
William Turner, President/CEO at Turner Building Science & Design, LLC, Lewiston/Auburn, Maine Are: Ventilation is important; but over ventilating schools in cold climates in January and routinely producing levels of 10% Relative Humidity (RH) or less is likely to be counter productive leading to eye and nose irritation. Source control, or local source control, is always the first mode of correcting a readily identified source such as excess use of Volatile Organic Compounds (VOC) in art settings or locating and proper removal of materials that smell musty, etc. Unfortunately, at the first sign of a complaint, many schools crank up the ventilation to lower CO2 to 600 Parts Per Million (PPM) or less and make it very dry. It is necessary to provide 15 Cubic Feet per Minute (CFM) during frigid weather and having in place a good cleaning practice. Similar problems occur during humid weather where humidity control is lost. Functioning in an 85oF room at 70% or higher RH is unlikely to be productive for learning. Most of the classroom calculations I have seen have 15 CFM per person with Air Changes per Hour (ACH) at about 0.5.
David Stevens, Independent IAQ specialist and western interface with China, Hong Kong: The problems with increasing ventilation rates are manifold. Overall conditioning of air (temperature and humidity) can result in significant seasonal changes in energy consumption, particularly if heating and / or cooling of the ventilation air is required, quite apart from humidity control.
Outdoor air is often not as “fresh” as we would hope. While CO2 is used as a tracer for Indoor Air Pollution, it is not an indicator for Outdoor Air Pollution. If, by bringing in more outdoor air, we are also bringing in other gaseous pollutants such as NOx, CO, VOCs, etc, then the benefit of increasing “fresh” air ventilation needs to be questioned, particularly if the only measurement of IAQ is CO2 . The level and type of outdoor air pollution needs to be seriously considered when considering increased ventilation.
The context of location needs to be taken into consideration. I live in Hong Kong, where the outdoor air, when used as “fresh air” intake, on some days is considerably polluted. I am not denying that “fresh air” dilutes the CO2 concentration; however in many built-up areas, there is a risk associated with the outdoor air as well. We even have situations here in Hong Kong, where the exhaust air outlet from one building sits adjacent to the “fresh air” intake of another, in which case, elevated CO2 levels don’t get a significant chance to become diluted before being taken into a building as “fresh air”.
Henry Slack, Indoor Air and Green Buildings at U.S. EPA Region 4, Greater Atlanta Area: if a school must install a humidifier to insure winter comfort, it will raise costs and the 1-8- cost-benefit ratio will not apply. But that doesn’t mean that outside air delivery cannot be increased in months when it’s more reasonable and get a great return on the investment.
Increasing ventilation has problems and can cost more in energy. But studies have show that this is an investment that will provide manifold returns. The only problem in using air cleaners or filters instead of outside air is, that CO2 itself may affect as a pollutant; few studies have shown a loss in the ability to make decisions at higher levels of CO2 . It has been found statistically significant decrements in six or seven of nine scales of decision-making performance.
The productivity drain suggests (in schools & work place) an easy sell when it comes to encouraging management to make the decision to purchase more technically advanced ventilation equipment. The “Zone of Occupancy,” is one way manufacturers can best target the use of their investments. A ZOO assessment makes selective and targeted use of resources. “The Zone Of Occupancy refers to the operating area of a facility where the actual ventilation or air replacement is required. By focusing clean air to the specific area required, improved comfort can be achieved at a lower equipment and operational cost, as compared to introducing air into non-critical areas.” The ZOO might include specific areas where dirty air is removed and clean air is supplied in order to provide comfort. On the upside, these targeted approaches keep the clean air where it’s needed most, eliminating costly full-facility usage.
Bill Silva, Owner, SIRP Environmental & Energy Solutions, Indianapolis, Indiana Area: Where does the “fresh air” come from? If it is polluted outside, it is not going to help inside. Pollution includes bacteria, viruses, and mould, as well as particulate. I have seen studies about improving production by creating more negative ions indoors, not just “fresh air”.
Peter Beale, Director International Marketing and Sales at Steril-Aire, Inc.,Greater Los Angeles Area: To get enhanced performance from the children comfortable and quality air is needed. A lot of school funding is related to pupil attendance days, so sickness absenteeism is expensive. If a school has an AC system it will be used for at least a part of the year. With the AC running, windows cannot be open and there is a need to eliminate the virus and bacteria taken into the school by the children and circulated through the AC system. There is also the mycotoxins that come from the mould growing in the coils that is also circulated.
Leslie Chia, Director at LS Engineering & Trading Pte Ltd, Singapore: To address mould problem, you will need very high intensity of Ultraviolet (UVC) and that is not at all energy saving. A Environmental Technology Verification conduct by Research Triangle Institute under a cooperative agreement with US Environmental Protection Agency (EPA)to verify UVC biological Inactivation Efficiency for Heating Ventilation and Air Condition (HVAC) also shows the air temperature after the passing through the UVC lamp increase by 0.7oC.
Peter Beale: This is contrary to our 18 years of experience where typically 1ft UVC Emitter ™ tube is covering 2ft of coil area and may use about 20 watts with the typical volume of air travelling though the coil at 55F, the increase in temperature is not measurable. Maintenance is once a year changing the tube which is much easier than cleaning a coil. Obviously it is part of the coil’s function to reduce the moisture and the resulting condensate allows the mold to grow in the coil, drain pan and ducts.
David Stevens: If Ultraviolet Germicidal Irradiation (UVGI) is applied to coils and drain pans etc., it will reduce the incidence of microbial contamination of those items. However the point is that despite a reduction in levels of contamination of the cooling coils etc it did not translate to a significant reduction in airborne pathogens at the workstation in this study, nor did it contribute to an improved perception of Indoor Air Quality by the participants. In fact, in two of the periods, the perception by participants was that the Indoor Air Quality was worse when the UVGI was on, compared to when it was off. For the other two periods, there was no perceptible change. For the study, the UVGI bulbs had a coating of Titanium dioxide (TiO2) to prevent the creation of ozone. Airborne Bacteria is only one of 9 identified Indoor Air Pollutants. The others are Respiratory Suspended Particulate (RSP), CO2, CO, NO2, Formaldehyde (HCHO), Total Volatile Organic Compounds (TVOCs), O3 and Radon.
Leslie Chia: The air temperature passing through the UVC system rises between 0.2 to 0.9oC. UVGI lamp using only 254nm wavelength will not create ozone. Installing UVGI lamp on the cooling coil with help reduce the microbial contamination in the area but you will need to install a system at the on coil and another at the off coil side for it to be effective.
With the RH at 80% and room temperature at 25oC show a 65% reduction in airborne mould contamination. The technology of the system is using photocatalytic. OH radical half-life is only a few nano second and it will not even get to pass our breathing system and can not have any harmful effect on human occupants. I do have reservations about some of the Photocatalytic Oxidation (PCO) manufacturers in the market as I’m not sure if the catalytic reactor is coated with the right compound and amount of TiO to make it work, as there’s a large complex reaction and inter-reaction of the oxidants generated.
David Stevens: A half-life of a few nano seconds doesn’t make a lot of sense, since for the oxidants to interact with pollutant molecules (which are dispersed throughout an occupied space), they will need to rely upon dispersion through Brownian motion, and that will take far longer than a few nano seconds. Oxidants are certainly small enough to enter our breathing system. Installation needs to be done correctly; otherwise there may be a risk of some long-term degradation of the system which could contribute to unwanted by-products. If the maintenance is performed as per recommendations, no such unwanted by-products would be produced, however, it is difficult to be certain on the level of maintenance.
Charles Waddell, President & GM, Roanoke, Virginia Area: Cold plasma technology installations give energy savings through outside air reduction using ASHRAE Standard 62 IAQP. Unlike UVC, cold plasma can kill pathogens in the space and on surfaces that are not in line of sight. It does not generate ozone. It does not use PCO technology that contains titanium dioxide to create hydroxyl radicals. It has been recently stated in the “Current Intelligence Bulletin 63” that titanium dioxide (Ti02) is now a cancer risk if inhaled, especially the nano-size particles. That should cause concern for any manufacturer, client/end user using PCO technology since the UV light can break down the binder holding the Ti02 to the substrate and release Ti02 particles down the duct into an occupied space.
The installations were designed at 5 CFM per person (and sometimes less) and were primarily school applications. A recent study at Valencia College in Orlando where the building was designed at 5 CFM per person, concluded the air quality in the building was much better than the outside air quality. The study included readings in multiple classrooms, the library and a book store. The readings included TVOC’s, particulates, ammonia, ozone, formaldehyde, bacteria and mould spore counting, etc. The testing company also took swab samples throughout the cooling coils to prove the cold plasma systems mounted to the air entering side of the coils sanitized the coils as claimed. The results showed 0 bacteria and 0 fungi on both sides of the coil, not just the leaving side like a UVC system. With such great IAQ and poor outdoor air quality, why would one want to use more outside air?
In conclusion, over ventilation is expensive and under ventilation can be expensive, if pressurization is lost then mould forms inside the building envelope. By reducing ventilation air and paying attention to pressure, combined with the right air cleaning provides with the most cost effective design approach to indoor air quality. CO2 is a great way to watch occupancy, but not to view overall IAQ. A TVOC sensor is best utilized to confirm the actual gas content and COC’s in the space. GPS provides multiple TVOC sensors and can show the effectiveness per pass of the cold plasma system as well as the space TVOC level with room mounted sensors in real time. A study conducted for the Navy by the National Research Council, proved that submarines operating at 8,000 PPM of CO2 24/7 had no affect on the occupants since air cleaning was employed removing the Certificate Of Conformity.
While much content has been provided in this post, everything covered is supported by recognized, industry leading, 3rd party agencies to prove there is good science behind what has been traditionally seen as smoke and mirrors. The days of the air purification companies telling clients to “trust us” are long gone!