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A Facilities Managers Guide to Achieving Adaptive Thermal Comfort for Occupants

by Tod Althoff | Feb 14, 2019 | HVAC, Facility Maintenance, Facility Manager, HVAC Maintenance, Ventilation, Mechanical Ventilation, ASHRAE, Commercial Building, Air Quality | 0 Comments

facility managers guide to thermal comfort

How comfortable is your Chicago building? According to ASHRAE, a building has achieved optimal thermal comfort when a minimum of 80 percent of the occupants are satisfied with the indoor environmental conditions, but how do you determine if 80 percent of the individuals in your building are comfortable? This can be a tough question to answer. Thankfully, there are factors you can consider when it comes to improving the indoor comfort of your building.

Understanding Thermal Comfort

The term thermal comfort refers to how comfortable the individuals in your Chicago building are on a daily basis. Unfortunately, individual comfort is not easily defined because perceived comfort is different for everyone. This may be why ASHRAE expects that 20 percent of the individuals who enter your building will not be entirely comfortable all of the time.

6 Factors That Affect Comfort

There are several factors that affect thermal comfort, and your building’s HVAC system and ventilation equipment is only part of that equation. Since physical comfort is subjective, according to the individual’s perceptions, it is important to take into consideration as many factors as possible, including an individual’s ability to control the environment, physical activity levels and layers of clothing as well as the HVAC system itself.

1. Physical Activity Levels

The employees in your building who move more are going to feel hotter. For example, when a person is sitting still, he or she puts off less heat than if they were running on a treadmill. From a perception level, the individual running on the treadmill may perceive the indoor temperature as hotter than the thermostat setting, but the individual who is sitting may perceive the room as cooler than the thermostat setting or actual indoor air temperature. For this reason, you may choose to keep temperatures lower in areas where employees are most active, like warehouses and manufacturing floors.

2. Amount of Clothing

This may seem like common sense, but the amount of clothing an individual wears into the building and while they are in the building can contribute to their thermal comfort. For example, wearing shorts outside on a hot day makes sense, but once the individual walks into an air-conditioned room, the shorts may not feel adequate for the lower temperature. Instead, they may wish the indoor air temperature were hotter or that they had worn pants. Encouraging employees to be prepared with additional clothing options may help them stay comfortable throughout the day.

3. Relative Humidity Levels

Relative humidity is the amount of moisture present in the air as it relates to the temperature of the air. For example, cooler air holds less moisture than hotter air. This is why the air feels drier in the winter than in the summer. Our perception of comfort also relies on relative humidity levels. This is because our natural cooling system, perspiration, relies on relative humidity. When the relative humidity is low, the perspiration on our skin evaporates faster, which helps us feel cool. When relative humidity is high, especially in the summer, individuals tend to feel hotter. HVAC systems can be equipped with humidifiers and dehumidifiers in order to maintain constant humidity levels throughout the year.

4. Amount of Ventilation

The airflow within the interior spaces has a direct effect on indoor comfort. When the air is stagnant, it can trap humidity and heat, making spaces feel hot and muggy or stale. Increasing air flow, but adding additional mechanical ventilation or providing ceiling and desk fans can increase indoor comfort levels.

5. Surface Temperatures of Materials

The temperature of the surrounding surfaces can affect an individual’s perception of the comfort of the building. For example, metal or stone surfaces are going to be cooler than wood or upholstered surfaces, which means that someone working on a metal table may perceive their immediate environment as being cooler than someone who is working on a wooden surface. Knowing this information can help you choose the right types of furniture for your indoor spaces, like offices, lobbies, waiting rooms and dining rooms.

6. Heat Output of Electrical and Mechanical Equipment

Some objects within a building put off more heat than others. For example, stoves and ovens in breakrooms and kitchens. Additional items that can put off heat include computers, printing equipment, electrical components and even certain types of light bulbs. For this reason, mechanical rooms and kitchens may need to be put on their own HVAC zones.

Achieving Thermal Comfort Through Building Design and Adaptation

While it may seem difficult to account for every factor that contributes to thermal comfort, it is possible to configure a building and its systems to account for most of the factors that affect human comfort in both new buildings and existing buildings.

New Buildings

New buildings can be designed with features that take thermal comfort into consideration. For example, the building envelop can be tightened with energy efficient doors and windows, advanced insulation can be installed in the exterior walls and in the attic or under the roof. The HVAC system can be designed with CO2 and occupancy sensors and a BAS system can be installed to manage all the primary functions of the building, including heating, cooling and lighting.

Existing Buildings

Existing buildings can be retrofitted to achieve optimal occupant comfort levels. To start the process, it may be prudent to send out a survey to all the residents and/or employees in order to determine if your building is achieving the optimal 80 percent comfort level satisfaction prior to implementing any upgrades. Asking the right questions can help you determine which system to upgrade first. For example, if your employees frequently complain about drafts, it may be prudent to start by sealing any leaks in your air ducts and sealing your building envelope.

Adaptive HVAC System

Modern HVAC systems have the ability to be extremely adaptive with the right types of technology. Thankfully, most of the new technology can be retrofitted to existing buildings. For example, occupancy sensors can help keep certain rooms cool when they near their max capacity. CO2 sensors can open dampeners, allowing fresh air into the building, and a BAS system can help you program temperatures, according to the day of the week and time of day.

Eliminate Building Envelope Leakage

Your building’s envelop consists of the exterior walls, roof, doors, windows and foundation. If your building is more than a few years old, it may leak. Eliminating air leaks by adding insulation and installing energy efficient doors and windows can help keep your climate controlled air inside, and the outdoor air outside.

Consider Individual Comfort Controls

The perception of comfort can be just as important as the mechanical systems you employ to keep your indoor air at a consistent temperature and well-ventilated. To help employees and residents perceive the indoor air as comfortable, consider allowing office windows to open and letting employees have personal fans and space heaters.

Adapt for Seasonal Temperature Changes

Advanced HVAC systems can monitor the indoor and outdoor air temperatures and adjust airflow, warm and cool air as needed. Providing window blinds can allow employees to close them during the hottest parts of the day to help reduce thermal heating in the summer. Advanced window blinds can actually raise and lower themselves according to the amount of sunlight entering through the windows.

Achieving 80 Percent Thermal Comfort

In order to determine if you’ve achieved desirable indoor conditions for your existing building, you can check maintenance complaints and send out a second set of surveys a few weeks after the upgrades have been completed to determine if most of the people residing and working in your building are comfortable. Ideally, only a maximum of two out of 10 individuals will find the indoor conditions mildly uncomfortable.

Advanced Heating and Cooling with Althoff

Here at Althoff, we can evaluate and inspect your current HVAC system, air ducts and ventilation equipment in order to determine if it is performing within the manufacturer's recommended guidelines, and we can listen to your concerns when it comes to improving your indoor air quality and comfort levels. Once we have all the available information, our HVAC heating and cooling design teams can recommend upgrades to your HVAC and ventilation systems that will improve the thermal comfort of your building and save you money on your monthly utility bills. We even install and upgrade BAS systems.

To learn more about our HVAC services and to schedule an inspection or maintenance on your current HVAC system or for estimates on a new HVAC system with adaptive and responsive controls, call us at 800-225-2443.

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