Q. What does it mean to “design for healthier indoor spaces”?
A. Before the COVID-19 pandemic, we were focused on thermal comfort, specifically helping to ensure systems are designed and sized to maintain a space dry-bulb temperature. But with the pandemic, emphasis has been placed on helping to ensure adequate space humidity and delivering cleaner air in addition to space temperature control. It’s important for building designers to understand what owners desire when they ask for healthier spaces. In addition to this, owners may have specific acoustical and lighting requests. Designing for healthier spaces is more holistic, meaning everything from temperature, humidity, air cleanliness, acoustics, and lighting, are considered.
For air cleaning, it might have been common practice to simply design HVAC systems to use MERV 8 filtration, but this should now be compared against the owner’s expectations. In addition, other air cleaning devices may need to be considered where MERV 13 filtration cannot be used.
In many cases, acoustics might be ignored unless there is a problem. A healthy space should include considerations to help ensure sound targets are met in the space. This may require some acoustical modeling, but it’s often easier and less expensive to design for acoustics rather than address issues after installation.
Q. What kinds of things are important to consider when designing for healthier spaces?
A. I believe building owners’ expectations have evolved since the start of the pandemic. Today, owners may want building systems to be capable of handling epidemic conditions, while continuing to maintain adequate space temperature, humidity, lighting, and acoustical comfort.
To address immediate needs, we may have temporarily operated buildings with 100% outdoor air, regardless of outdoor air conditions and the ability to utilize airside economizing. In the long term, this practice of simply providing 100% outdoor air is not practical to ensure adequate space temperature and humidity with existing systems. But for new systems, separate and unique pandemic operation may be a design consideration. The scope of what that includes may vary from system to system, however. For example, some systems might be designed to handle filtration with higher MERV ratings but be incapable of providing 100% outdoor air. Conversely, some systems might be designed with a combination of filtration and other air cleaners to achieve an equivalent high-MERV rating.
It’s also important to remember that air cleaning devices have different advantages and drawbacks. There is, unfortunately, no “silver bullet.” Each device type should be evaluated for the given application to make the best choice.
Engineers need to find ways to provide good indoor environmental quality design while also meeting or surpassing energy consumption and decarbonization goals.
Q. Why is asking “what one technology or practice has the most potential impact” the wrong question?
A. Every building is unique with its own set of considerations based upon a variety of factors, such as building construction, size, shape, and purpose. It’s important for engineers to understand owner’s expectations up front and design to meet those needs.
With respect to air cleaning, the latest ASHRAE® and CDC pandemic guidance is to install and operate equipment with MERV 13 filtration or equivalent. But that may not be possible for some products which do not have the physical space to install such a filter. In addition, some units may not have fans capable of operating with the higher static pressure drop imposed by a higher-MERV filter. As a result, designers need to evaluate each system to determine whether it has the capability to operate with an upgraded filter. So, a combination of technologies may be needed to meet project IAQ goals.
As another example, with acoustics, we can use modeling software to predict space sound pressure and model what-if scenarios to help ensure the owner’s sound target is met. And like energy modeling is used to design the best system for the building, all of this can be done during design.
Q. What are the right IEQ-related questions to ask before designing a project?
A. It’s important to understand the owner’s expectations for temperature, humidity, air cleaning, acoustics, and lighting. And some of these expectations may have changed since the pandemic started. While some owners might know exactly what they want, I expect many will leave the details to the consulting engineer. So, it’s important to establish exactly what the owner hopes to achieve, while also having an understanding of applicable solutions.
- How do you expect this building to operate if there is an epidemic or another pandemic? Understanding whether systems need to be capable of operating at 100% outdoor air, maintaining 40% relative humidity, and other pandemic operation considerations will inform decisions related to system selection, load design and coil selection, the need for dehumidification and humidification, and air cleaning device selection.
- What temperature and humidity conditions do you expect in your spaces? I don’t believe owner’s thermal comfort expectations have changed, however there may be new considerations if systems are expected to operate in a “pandemic mode” where they can supply more outdoor air while maintaining temperature and humidity.
- What do you expect for air cleaning? While owners might not specify filtration MERV ratings and air cleaning technologies, how they respond to this question may be useful to make informed air cleaning decisions.
- What are your sound targets? Understanding whether the owner has sound targets, such as A-weighted sound pressure or a noise criterion (NC) value, will help with system selection, acoustical modeling, and decisions related to sound attenuation devices. It’s almost always less expensive and easier to address acoustics up front, before commissioning and occupancy. When addressed later, there are generally fewer attenuation options and field-installed options tend to be costlier. I would suggest understanding acoustical requirements early in the design, so they can be accommodated throughout the process.
- Do you want to monitor and/or display temperature, humidity, and air quality information? For some owners, it may be important to monitor, analyze, and share indoor environmental quality. As a result, a monitoring system and display dashboards may be important.
Q. What are good conversation starters for engineers to have with builders or facility managers?
A. The world has completely changed and our expectations for buildings have changed accordingly. I would start by asking how their building requirements have changed.