COVID 19 – Indoor Air Quality – Energy EfficiencyArticle | 05.07.2021
Is it one or all three?
The COVID 19 global pandemic has brought increased focus onto the building heating, air conditioning and ventilation (HVAC) systems for all building types. The issue is of particular importance to educational facilities because they are the buildings where our children and young adults spend many hours over the course of their formal educational lives. Fortunately, there are many people who where already focused on indoor air quality including building owner, architects, engineers and state and federal agencies. But what exactly do we mean by indoor air quality or IAQ? If some IAQ is good; doesn’t that mean by definition that some IAQ is bad?
We’ll start with a baseline definition and the key contributing factors and then move forward. Indoor air quality is the nature of the indoor air as it relates to the health, well-being and productivity of a building’s occupants. There are 4 fundamental elements the influence IAQ. Contaminant source control is the first and encompasses all the things we do to prevent contaminants from entering a building and includes everything from walk-off areas at building entries to selecting low emitting paints, furniture, and fixtures to behavioral practices such as covering your mouth when you sneeze and washing hands and finally cleaning practices focused on occupant health outcomes in lieu of appearance. Second is management of indoor humidity. We’ve all heard that too much of a good thing is not longer good. And this applies to humidity at both ends of the spectrum. High indoor humidity (over 60% relative humidity) can create conditions ripe for growth of mold and mildew which exacerbate allergies in in the most extreme cases can cause serious illness. Low indoor humidity (less than 40% relative humidity) creates stress on our respiratory system from nasal passages to our lungs which make it harder for our bodies to fight infections. Viruses and bacteria are much more viable at either end of humidity spectrum than in the sweet spot from 40-60% relative humidity. The 3rd and 4th elements are ventilation or fresh air and filtration. We’ve heard lots I the news about both of these issues with the pandemic. The air moving thru most building HVAC systems is a mixture of recirculated air and fresh ventilation air. We bring ventilation into the system to dilute airborne contaminants produced by the occupants and the building. The engineering society ASHRAE has long studied this practice and publishes standards for minimum system characteristics. Filtration works with ventilation to capture any particulates carried in the air. For ventilation air this is primarily dust but also includes pollen and other particulate pollutants. The filters are frequently placed where they filter the return or recirculated air and the ventilation air at the same location.
As mentioned earlier there are many people working on issues of IAQ all the time and some of them work for federal agencies including the National Institute of Standards and Technology (NIST). Dr. Lisa Ng is a mechanical engineer in the NIST Indoor Air Quality and Ventilation Group and was part of/lead a team that created a new, online assessment tool to help owners, architects and engineers assess the relative reduction in aerosol exposure in educational spaces when characteristics of a learning environments HVAC system were changed as well as including non-HVAC controls. The tool is called FaTIMA and is free to use and can by found at https://www.nist.gov/services-resources/software/fatima along with the full study report. FaTIMA is the output of research and modeling of classroom size space and an assembly sized space and with different age occupants. While the research does not define a direct metric for infection risk, FaTIMA can be used to identify and compare possible control strategies to reduce exposure and that there are multiple paths to reduce exposure across multiple types of HVAC systems available to building owners. As someone working for a university, that is very good news because major changes to building HVAC systems often require capital investment.
Most folks like to open their car windows when the weather is comfortable outside. But for most of the year, we don’t want the same temperatures indoors that are outdoors. Conditioning our indoor air consumes electricity, natural gas and other fuels. Utility costs are typically a schools 2nd largest cost after personnel. We also build, own and operate buildings for a very long time. Many years ago I listed to a school facilities director share the story of how he worked with his school board. He helped them see that 70-80% of the total cost of the building would come after the initial construction. His mantra to the board was “we’re too poor to build cheap” buildings. He helped them understand that constructing buildings that were inefficient with utilities, difficult to clean and maintain and were not designed to support future changes in pedagogy we not a good investment.
For a K-12 school, the HVAC system is typically 66-70% of the total utility load. And conditioning ventilation air is the most expensive air to condition because it is frequently hotter, colder, dryer or more humid than we want the air in the building. Once an HVAC system is selected, high quality maintenance practices are the best approach to keeping that system operating efficiently. Proper filter replacement practices are great place to start. It’s important to select the right filter. A filter saves a few pennies per filter may seem like the right choice when budgets are limited. But using incorrect filters leads to dirty heating and cooling coils which causes the fan and the heating/cooling source to work harder. Without realizing it, your saved pennies on filters are now going out the door in utility and maintenance costs. And please pay attention to equipment access for filters and future equipment replacement when designing a new facility or renovating an existing one. Poor maintenance access will not support quality maintenance practices.
These issues may seem a bit overwhelming, and that’s ok because balancing occupant health, IAQ and energy efficiency is a multi-faceted problem. But it can be done when teams come together with a collaborative attitude, a willing ness to listen and to share their knowledge. At a prior company I had the opportunity to work with a team developing design standards for new school buildings in New Orleans, LA after hurricane Katrina. The district set goals including LEED Silver certification and at least 30% energy cost savings for the new designs. We joined the process after the initial HVAC system selection (centrifugal chillers and large VAV air handling units) met the energy savings (almost 35%) but wasn’t aligning with the historic maintenance experience, knowledge desires of the district. Unfortunately, the designers didn’t offer any alternatives so we put a fresh set of eyes and ears on the issue. The district had some experience with air cooled chillers for chilled water and liked the option of multiple service companies in the city. For locations without chiller water, many of the systems were residential style furnace and cooling coil units or small packaged roof top units. Our final solution included air cooled chillers, high efficiency boilers, chilled water and hot water fan coil units in closets accessible from the hallway to allow filter changes without disrupting class and a dedicated outdoor air system (DOAS) to handle all the ventilation needs. This system provided designers greater flexibility for each site, produced almost 32% energy cost savings and had a lower budget cost.
Any discussion about IAQ in schools would be incomplete without mentioning the US EPA Indoor Environment Division’s Tools for Schools Program. The program includes educational information including live and recorded webinar series, sample checklists for everything from integrated pest management to custodial practices to HVAC inspections, and materials to help you develop your own policies and communication tools. And there is a large network of schools that are happy to share how they worked through hurdles and have developed successful programs. You can start your program by visiting https://www.epa.gov/iaq-schools to learn more.
Final Thoughts on balancing occupant health, energy efficiency and indoor air quality
- Good IAQ practices support the core mission of public schools – educating children
- Academic facilities do impact academic outcomes so they should promote learning
- Owner commitment is the first step
- The O&M staff is a critical link
- Design and build for the long term; schools live a long time
- The school building can teach more than the students and should represent the values of your community