All of this coverage springs from a study published Aug. 3 in the journal Nature Climate Change. The study found that women have slightly lower resting metabolic rates than men, further arguing that current standards for designing office air conditioning systems are flawed, since they’re based on men’s metabolic rates and fail to factor in that metabolic difference.

While the narrative of “sexist” building standards conspiring to freeze women is undeniably compelling, I think it’s also extremely simplistic and misleading.

Many people are genuinely chilly at work, and that discomfort has almost nothing to do with building standards. Conversely, it has everything to do with the actual HVAC (heating, ventilating, and air conditioning) system installed at the office, the maintenance of that system, and the person behind the controls.

Getting technical

As the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) pointed out in response to Nature Climate Change’s study, ASHRAE’s Standard 55—Thermal Environmental Conditions for Human Occupancy—is actually based on research into “comfort criteria for the indoor environment … with more than 1,000 subjects with equal amount of women and men.”

ASHRAE’s building standards are based on many different factors, and merely accounting for higher metabolic variation wouldn’t significantly change the model of heating/cooling standards.

That doesn’t mean individuals (both men and women) aren’t cold at work, though. Crucially, there are often no standards controlling who sets the thermostat, or how they set it.

According to Science News Magazine, previous studies have shown that indoor air temperature in office buildings is, on average, much cooler than what ASHRAE recommends. Whether over-cooling to reduce humidity, as a sign of power or prestige, or because energy is comparatively cheap in the U.S., American thermostat-handlers are making buildings unnecessarily frigid.

In my opinion, an overlooked factor in this arena is the HVAC system itself. Regardless of building standards or calculations, occupant comfort is fundamentally a result of that HVAC system selection, design, layout and subsequent maintenance. Low “first cost” systems with direct expansion (DX) coils and standard heat pumps are cheap, but they have limited controls for comfort and may deliver blasts of hot or cold air—hence creating uncomfortable occupants.

In buildings with such systems, occupants may feel a draft from an ill-placed supply grille. Perhaps the occupant is sitting next to a window and feels the heat or the radiated cold through the window. All of these elements contribute to whether occupants feel hot or cold in a space, but none of these factors are a result of an outdated or “sexist” building standard.

In comparison, properly-designed, complex hydronic HVAC systems—which use water or another liquid as a heat-transfer medium—are much better-suited to optimize occupant comfort. So are HVAC systems with variable speed compressors, which save more energy and deliver more constant air pressure than cheaper alternatives. These types of dynamic HVAC systems are often pushed aside for lower “first cost” options, to the detriment of occupant comfort.

The human element

Regardless of system choice, the system also has to be correctly designed and installed in order to operate properly. Poorly-maintained HVAC systems will not operate properly, doubtlessly contributing to comfort issues. When it comes to maintenance, I have a motto: “Fix broken stuff first.” Before blaming building standards, we need to make sure our equipment is in working order. If it’s broken, it won’t work.

In the larger scheme of things, there’s unfortunately no “magic bullet” solution for engineers that would ensure perfect thermal comfort for every occupant. For the 80 percent of men and women who are comfortable, there will always be 20 percent who are uncomfortable.

Before blaming dubiously “sexist” building standards and continuing to freeze, people should know there are actionable ways to achieve thermal comfort: Maintaining and optimizing their existing HVAC system, adjusting the thermostat, or—easiest of all—adding or subtracting a layer of clothing.

Kristina Sing, PE, is the Seattle-based engineering manager of McKinstry’s energy team. She can be reached at kristinas@mckinstry.com.

Comments

Great article Kristina,
Low “first cost” systems:
(DX) coils and standard heat pumps are cheap, but they have limited controls for comfort .
Proven advances to the low first cost system are usually modified as a down the road improvement after the occupants threshold for discomfort is realized.
Economizers on heat pumps , well commissioned controls, and Hydronic based systems are the answer to many uncomfortable indoor climate issues Chilled beams and radiant hydronic panels are also meeting challenging temperature and design issues.
Contractors, designers and engineers must continue to “beat the drum” to have the decision makers carefully weigh the difference between Low first cost, work place comfort and the total cost of comfort.