Some thermal comfort issues can be addressed with simple fixes, while others require more time and investment. Here’s what you need to know.
Featured Editorial on FacilitiesNet.com By Patricia Kaufmann and Samantha Longshore
A statistic from the U.S. Environmental Protection Agency’s 1989 Report to Congress on Indoor Air Quality is making the rounds again. Americans spend 90 percent of their time indoors. Think about your average day, a majority of which may be spent at the office, and not a lot seems to have changed since this report was issued. However, we do see a movement toward wellness, trying to ensure that occupants are healthier and happier in their built environments. With employee attraction and retention of key interest to companies, an issue at the forefront for facility managers is providing a comfortable working environment. The number one complaint reported in offices is being too hot or too cold, but occupant thermal comfort can be difficult to tackle. Every building and every employee occupying that building is unique. But there are common thermal comfort issues found in many buildings. Some can be addressed with simple fixes; others require more time and investment.
Small fixes may solve problems or simply help cross possible issues off the list. Here are some places to begin.
This step seems simple, but simple is the best place to start. To function at its best, equipment should be kept clean. Key points to review include the following:
- Add reheat coil and cooling coil cleaning to an in-house maintenance program
- Ensure that filters are replaced regularly. An air filter that’s overloaded with particulates increases resistance and reduces airflow. This may hinder the system’s ability to provide conditioned air to tenant spaces.
- Ensure that air terminal box flow sensors are free of dust and debris for accurate readings. The following section on inspection has more below another check on this equipment.
With cleaning tasks complete, continue with a visual review of the following items to hone in on thermal comfort problems:
- Check air terminal box and fan-powered box flow sensors. Depending on the type of air sensor, the flow cross is not bent and should be replaced.
- Check the wiring from the air terminal box to the thermostat. Make sure they are connected to each other.
- Ensure that fire, smoke, and combination fire-smoke dampers are not closed and are not blocking air flow through the duct system.
- Review ductwork insulation to see if any is missing or needs repair.
- Review duct access doors to ensure that they are in place and have been installed with no gaps.
- Check for leaks in air handling unit casing and ductwork. If the AHU is losing air to the ceiling space, it will not provide the proper air need to cool or heat.
- If exterior doors are difficult to push open because the outside air wants to rush inside, this is an indication that the building is negatively pressurized. With negative pressure, the building is likely to pull outside air in from cracks, leading to increased humidity in warm weather and chilly drafts during cold. A little positive pressure creates a barrier from the exterior, allowing for more control over interior conditions.
Inspections, Education, Adjustments Can Help Solve Office Temperature Complaints
These three best practices can improve occupant thermal comfort and satisfaction in office space.
Location, location, location: When it comes to addressing thermal comfort issues, the next group of items involve location-based visual inspections (and as you can see, they are many):
- Ensure that outdoor/ambient temperature sensors are not located in areas that receive intense sun or full shade. This may lead to inaccurately higher or lower readings, engaging heating or cooling coils when not necessary.
- Review locations of supply diffusers and grilles. Review outlet air pattern (if adjustable) to ensure that they are pointing in the correct (most comfortable) direction.
- Review locations of return air grilles, transfer grilles, and transfer duct assemblies. Transfer duct assemblies could be short supplied air flow if a supply air diffuser is too close. The return air path wants low resistance, which would have minimal pressure drops back to the central AHU.
- Ensure that interior thermostats are located efficiently. Move them out of direct sunlight (just like the outdoor sensor). Keep thermostats away from exterior walls, where the temperature can be at its highest or lowest, depending on the temperature outside. It’s also important to ensure that thermostats are not in a direct line of supply airflow paths, pushing the warmest and coolest air right onto the sensor and creating falsely high or low readings before air is distributed through the space.
Locate thermostats near the return grille (which should be near a room’s exit door), to provide accurate readings from the mixed air leaving the space. But do not locate thermostats in typically unoccupied spaces. If you’ve recently gone through a remodel, for example, you might have one thermostat that now controls one regularly occupied office and one conference room. If the thermostat is in the conference room, it’s likely unable to moderate the temperature needs of the office next door and will lead to unhappy campers for most of the day. A private office may also have distinctly different heating and cooling needs compared to a densely occupied conference room during meetings.
Talking with tenants and asking for compromise isn’t always easy. However, with education and discussion (especially on the front end of a move-in), it’s possible to prevent some thermal comfort issues before they materialize. Sometimes the best solution is to relocate employees away from hot or cold spots in the office. Windows are a big example. Consider this. Locations near the windows are sometimes the most highly coveted spots in the office. If employees can be educated on why glazing just doesn’t provide as much thermal insulation as typical walls, it may help them decide on whether that location will work for them or not. If they decide they can handle a little heat gain in the afternoons or cooler temperatures in the winter, they may be more inclined to prepare themselves to accept those conditions in exchange for the magnificent view.
Make Some Adjustments
Once you’ve cleaned equipment, performed inspections, and talked with tenants, a few adjustments may aid occupant thermal comfort.
- As noted above, a slightly positive pressure helps to create a buffer from the exterior. Specifically looking at lobbies, the addition of a cabinet unit heater in a vestibule may help that buffer in cold climates.
- If you’ve got a strong winter wind, we may want to talk relocation again. Locating a reception area to the side of a main entrance, rather than directly in front of doors, will help shield occupants who are closest to the exterior environment from extreme weather conditions, be it heat or cold.
- Relocate occupants who may be situated near a thermal bridge (in the exterior wall) where they experience thermal discomfort due to the difference in temperature.
- Review HVAC operating hours and set points. Ensuring that buildings start up and shut down at appropriate times can help with temperature control. However, consider these adjustments cautiously. Starting and stopping the building way before necessary may stop calls from coming in, but can cause extreme waste and high energy bills. Move start and stop times closer to occupancy by 15-minute increments. If you don’t receive hot or cold calls, try another 15 minutes until you’ve found the pain threshold. This ensures that you achieve a balance of comfort and efficiency.
Finding the Right Resources to Solve Too Hot/Too Cold Problems
If simple fixes don’t do the trick, it may be time to call in reinforcements. Here are some tips on how to get the best help.
What happens if simple fixes for too hot/too cold complaints don’t solve the problem? For example, those visual inspections may have identified bigger problems that just can’t be handled in-house. Or maybe you couldn’t find anything at all. Now it’s time to consider bigger fixes.
Call for Reinforcements
While visual inspections and regular maintenance can help ensure system efficiency and functionality, some issues may require assistance from third parties. Here are examples of items that are not easily reviewed on-site due to inaccessibility or lack of visual cues, and larger system issues that may require rebalancing or resizing.
Test and Balance Contractors
Consider contacting a test and balance contractor to help review the following plausible causes of thermal discomfort.
- If you have specific individuals who report that are always too hot in their space, you may have a hot water valve in the terminal box or baseboard heating system that is stuck open. Similarly, if a handful of individuals report always being cold, the valve may be stuck shut.
- A test and balance contractor can also help determine if the water/hydronic system needs rebalancing. If tenants located furthest from the mechanical rooms often report that they are too cold, this is a good indication that the hot water system is not recirculating properly or the hot water pump may be undersized to meet the needs of tenants furthest away.
- A balancer may also be able to determine if supply fans are undersized or simply not pulling enough air for distribution to tenants spaces.
If supply fans are undersized or pulling too little air, it may be time to talk with a mechanical contractor.
- Mechanical contractors can assist with both adjusting supply fans to bring in appropriate amounts of outside air and with the installation of new supply fans if those on-site are found to be undersized for the areas they serve.
- A mechanical contractor can also help you review booster reheat coils in terminal boxes. Booster reheat coils could be under-sized or over-sized (leading to inefficiencies); mechanical contractors can help you determine if additional installations should occur to help provide more heat. If a supply fan is underpowered, ask the mechanical contractor to review the fan or duct pressure system to see if it can be increased or lowered. Installing booster electric coils in a hot water reheat system could substitute for replacing the underpowered fan.
- The contractor may recommend relocating duct static pressure sensors to ensure optimal location. We recommend three-quarters of the way down a ductwork run. If a sensor is installed just halfway down a run, it may not measure enough duct static pressure to communicate appropriate needs to the supply fan.
Building Automation System and Temperature Controls Contractors
A BAS or temperature controls contractor can help you dig into building settings for problem areas.
- Thermostat deadband setpoints are sometimes field-adjustable from the BAS, allowing your on-site team to review and adjust as necessary. If the setpoints are not field-adjustable, a BAS or temperature controls contractor can assist. Having narrow temperature deadbands can cause heating and cooling systems to fight throughout the day and night. The building’s cooling and heating temperature set points should be around five to eight degrees apart, ensuring that heating systems don’t kick on as soon as cooling turns off.
Whether a simple clean, a visual inspection, a relocation, or system overhaul is needed, this list can promote thermal comfort for occupants and identify issues along the way.
Patricia Kaufmann (firstname.lastname@example.org), LEED AP BD+C, CxT, and Samantha Longshore (email@example.com), LEED AP O+M, BD+C, are senior solutions consultants for Rivion. The firm offers energy and sustainability solutions to improve building performance, reduce operating costs, increase asset value, and create healthy environments.