Building Science Part 7 IEQ

Occupant experience (OX), a concept often overlooked in the buildings of the past, has become an area of focus for the CRE markets. With the growth of sustainability, many factors aimed at improving the health and wellbeing of those inside a building are gaining momentum. In addition to architects, building owners and developers realize that healthier and comfortable building occupants are happier and more productive and increase the demand for their spaces. Many of today’s sustainability & construction approaches need to prioritize the issue of OX.

In this article, we’ll cover a variety of indoor environmental quality (IEQ) areas that contribute to OX including thermal comfort, indoor air quality (IAQ), acoustical comfort, and visual comfort.

A Holistic Approach to OX through IEQ

Thermal Comfort

There are a few standards for thermal comfort in buildings that have been set over the years by building and design industry organizations. These standards present detailed information on why building occupants complain about thermal conditions in a building. Air temperature and humidity, as you might imagine, are high on the list, but there’s a great deal more involved. Radiant temperature surfaces, such as walls and ceilings, cause complaints when they’re either too hot or too cold, and many people are sensitive to floor temperature. Virtually any location in a building may be cause for thermal discomfort. Vertical temperature differences and drafts, causing convective heat transfer, can also be added to the list. Secondary factors include daily and seasonal changes in temperature and humidity, the age of the occupant and the occupant’s adaptability to change.

Basically, it all boils down to the following six factors when performing thermal comfort analysis:

Air temperature
Humidity
Radiant temperature/ temperature of surfaces
The occupants’ personal metabolic rates
The amount of or lack of clothing insulation worn by occupants
The speed of air across body surfaces

Most people are comfortable in winter when the temperature ranges from 68 to 76 degrees Fahrenheit and the relative humidity is between 60 and 30 percent. In summer, people feel comfortable in temperatures ranging between 74 and 80 degrees, and when the relative humidity is between 60 and 30 percent.

Physical activity and corresponding metabolic rates definitely have an impact on comfort depending on activity level and should be considered depending on the purpose and use of the building.

IAQ standards spell out minimum ventilation rates for new construction, as well as information on improving IAQ in existing buildings. They also provide lists of maximum contaminant levels for those spaces to maintain acceptable IAQ, which minimizes the potential for adverse health effects on building occupants.

To maintain healthy IAQ, attached parking garages should limit vehicle exhaust from entering into other occupied spaces in the building. It is recommended that air pressure in the garage be maintained at or below the pressure in adjacent space, so exhaust gases aren’t drawn into the building. Airtight vestibules should be used to separate the garage from the adjacent occupied space.

Airborne Contaminants

Although, it’s often hard to detect, many buildings harbor potentially harmful elements that can contaminate interior air. Here’s a list of some of the most common airborne contaminants:

Viruses are at the forefront of everyone’s concern in the wake of the coronavirus pandemic
Moisture: you may not think of this as a contaminant, but moisture can create an atmosphere for the growth and generation of bio-aerosols, such as bio-organisms and mold
Pollen can be a serious contaminant, especially for occupants with allergies
Gaseous contaminants, which include ammonia, carbon monoxide and carbon dioxide
Volatile organic compounds (VOC), which are organic chemical compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the atmosphere

There are guidelines for environmental emissions offered by the U.S. Environmental Protection Agency (EPA), especially on the subject of air pollution caused by a product’s VOC emissions. GreenGuard Environmental Institute and others certify products for IAQ performance. Look for their certification on components you choose for your buildings.

Many Saint-Gobain & CertainTeed products are certified. For more information on specific items you can start with a resource like https://saintgobain.ecomedes.com/

You will also want to addresses ways to continuously remove such pollutants from the interior air. Here are some methods of airborne contaminant capture and removal:

Remove pathogens and particulate matter through filtration
Incorporate UVC light-based air cleaners
Monitor gas concentration
Clean heat exchanger and finned-tube coil
Manage moisture throughout the HVAC system
Clean dehumidification systems, including drain pans
Clean humidifiers and water spray systems
Employ moisture management techniques in the building envelope, including water-resistive barriers, vapor retarders and air barriers

Impact of Humidity

Humidity has an impact on the design of HVAC systems for cooling. An important factor to consider is the humidity ratio, the mass ratio of water vapor to dry air. It’s also important to remember that location determines the humidity ratio. For example: Miami has a hot and humid environment, with a lot of moisture that needs to be removed from occupied spaces. Now, Phoenix and Miami can have similar air temperatures, but Phoenix has dry heat, with very little humidity. Even cities within the same state can have different climates. For example, in Texas, Amarillo has a similar climate to Phoenix, with the same dry heat. But Houston’s hot and humid climate is the same as Miami’s. HVAC must take the specific climate, not just the region, into consideration.

IAQ

Acoustic control is another method of enhancing occupant comfort that is a major differentiator across CRE markets. There are five goals to providing a superior acoustic environment:

Reduce sound reverberation time (echo factor)
Limit airborne noise (sound transmission from space to space)
Limit sound transmission through common plenums and HVAC
Reduce impact noise
Minimize background noise

Reducing Sound Reverberation

The reduction of sound reverberation time is accomplished by employing sound-absorbing surfaces, such as acoustical ceilings, fabrics and carpeting. The best plan is to configure spaces to reduce, rather than amplify the sound energy.

Long reverberation times, especially in the workplace, can have a substantial negative effect on comfort. Sound that bounces off walls, floors and ceilings can create an environment with poor communication and hard-to-understand speech. This can lead to increased stress levels, limited concentration, fatigue and an increase in mistakes. So, it’s wise to increase comfort by reducing reverberation times with sound absorbing materials. Ultimately it can make your investments more attractive and valuable by creating a healthier working environment with spaces where workers are more efficient and want to be.

The factors that influence reverberation time are room volume, shape and surface absorption. All three are strongly influenced by the number of people and objects in the room — people make excellent sound baffles. Reverberation time should be less than one second, in most circumstances, for good speech intelligibility.

Limit Airborne Noise

When we consider ways to limit airborne noise, one important
consideration is to design high sound transmission class
(STC) assemblies. Also, try to enclose or separate spaces
with group activities that may create chatter from common
areas, using acoustically efficient walls.

Limit Sound Transmission Through Common
Ceiling Plenums

Limiting sound transmission through suspended ceilings
usually means limiting crosstalk or machine noise. You can
limit airborne noise transmission through ceilings by
designing high ceiling attenuation class (CAC) assemblies.
And, you can extend partition heights through the ceiling
plenum to the deck above to provide additional noise isolation.

Reduce Impact Noise

To limit the transmission of impact noise, you can design
high-impact insulation class (IIC) assemblies. Isolate
finished floors and ceilings by installing resilient
underlayments, by using sound-absorptive floor
coverings (carpets and carpet pads) and by using resilient ceiling suspension systems.

Minimize Background Noise

Design your HVAC systems to absorb energy and reduce background noise so airborne noise isn’t transmitted through the ductwork. Mechanical equipment should be isolated using vibration dampening techniques and high sound transmission reduction enclosures. One other tactic is to actually raise the level of background noise in the space with masking sound. Sound masking involves adding white noise to the space which is most effective after employing the above approaches.

Acoustical Comfort

More in this Series:

Leveraging Occupant Experience to Increase Value

Improving Occupant Experience with Thermal Control

Keeping the Good Air In and the Bad Air Out

Protect Your Investment with Moisture Control

Don't Hope for Good Acoustics

Building Sustainable Investments

An Occupant Experience Focus Leads to Healthier, More Productive Spaces

Open plan office spaces should be designed for both privacy and for intelligibility. Speech intelligibility is mainly dependent on three factors: background noise, reverberation time and the shape of the space. Speech privacy is the degree to which speech is unintelligible. Sometimes, you want speech to be unintelligible — such as in an office setting where intruding speech should be made less intelligible, or in a doctor’s office where voice transmission between examining rooms is undesirable — and sometimes, a high degree of intelligibility is important, such as in a training room.

Be sure to make clear the purpose of your spaces and the occupants’ primary use to direct the best acoustic control methods.

Schools, in particular, have very specific acoustical performance requirements and can be good guidance for conference and training rooms. These criteria discuss controlling reverberation with sound-absorbing materials and gives recommendations for noise isolation between interior spaces, in open-plan classrooms, outdoor-to-indoor and other topics to maximize engagement and learning potential.

“Intelligent” Acoustic Comfort

Want complimentary building science expertise and insight? Solving issues before they become problems is just one area in which Saint-Gobain Commercial Solution’s building scientists deliver value. By helping our strategic owner and developer partners discover the pitfalls and unintended consequences of projects, they can avoid the need for costly change orders or post-occupancy renovations and deliver a more profitable result.

We are passionate about great occupant experiences and helping clients understand what they are really going to get for their investment. We take great pride in providing our clients more confidence in the construction decisions that they are making. It is just one way we achieve our vision of making the world a better home.

For Your Success

Visual comfort is part practical and part aesthetic and it employs such strategies as artificial lighting, day lighting and creating visually interesting environments.

Lighting Strategies

There are a number of lighting strategies that you can employ to create a high-quality visual environment. Some recommendations are:

Provide automated lighting controls that optimize the balance between day lighting and artificial lighting
Increase the perceived space brightness by lighting vertical surfaces — this can be accomplished through the use of sconces
Balance the quantity of light with the quality of light in all work areas by carefully planning the placement of lighting fixtures
Control glare
Provide user-controlled task lighting at workstations.

Remember, optimal lighting needs change over the course of a day and year, so it’s important to select lighting with flexibility in mind.

Whenever possible, integrate natural lighting into your plans. Studies have shown that natural lighting affects people’s mood and comfort levels, so allow as much daylight as possible into the building. At the same time, though, it is important to avoid excessive heat loss and gain by demanding windows with low e coatings. Passive shading will make the interior spaces more thermally comfortable. It’s also possible to control window glare with proven innovations like electrochromic glazing solutions that smartly control glare and solar heat gain automatically without impeding the very views that increase comfort and productivity.

Occupant Visual Interest

Overlaying all of these principles is the need for aesthetics, or visual interest. So, whenever possible, provide a view of outdoors and access to outdoors. Try to include natural environments between the interior and exterior and bring a little nature inside. Employing biophilic design and balancing the use of such elements as scale, color, texture and pattern, as well as artwork and plants, to create visual interest. Conversely, don’t be boring. Avoid uniformity and visual chaos — keep designs clean and simple.

For more on the value of achieving maximum visual appeal: https://www.sageglass.com/en/visionary-insights/quantifying-real-estate-value

Visual Comfort

A Comfortable Conclusion

By following the guidelines above, you should have a good understanding of what to consider to build spaces that will increase the overall comfort and health of building occupants and help them to be happier and more productive. OX makes a big difference in the livelihood of a company and the value of your CRE investment.