It may be the middle of summer, but you'd never know from looking around offices, where, on the hottest days of the year, it's not uncommon to see workers wrapped up in sweaters at their desks. As temperatures outside rise, most corporate office buildings become hermetically sealed, air-conditioned ice cubes, forcing workers everywhere to grab a Snuggie. In a study of government office buildings, for instance, 60% of workers complained of thermal stress–that they're too hot or too cold in their workplace. Why can't we manage to keep offices at a comfortable temperature? 

Several things could be causing your building to turn into a frigid tundra every summer, ranging from not enough thermostats to an oversized cooling system to miscalculations about how many people will be in a room (and what they'll be wearing) at any given time. Luckily, there are solutions that don't involve buying a personal space heater.

The more thermostats you have, the more you can control temperature variations throughout a building–someone sitting in direct sunlight has different air conditioning needs than a colleague sitting across the room on a shadier side of the building. But more control comes at a price. "Giving a thermostat to each office requires more wiring," says Georg Reichard, an associate professor of building construction at Virginia Tech. If you're looking to cut costs during the design phase of a new building, that's one of the first things to go. By skimping on the density of thermostats placed throughout the building, developers get a lower price tag, but occupants later pay the price in discomfort and inefficiency.

The HVAC (heating, ventilation, and air conditioning) system may not be designed for the right conditions, either. Electronics are a major source of heat in offices, and air conditioning systems are designed to offset this. In newer office buildings, switching to LED lighting (or LED computer monitors) can lead to cooler temps, because LEDs don't get as hot as other types of lighting, like CFLs. But most buildings don't account for the difference in their estimations of how much a room should be cooled. HVAC systems designed for offices with older lighting technology–regardless of the facility's latest upgrade–are compensating for extra heat that isn't actually being generated, so they end up being much colder than intended.

The speed of the fan pushing air into the room matters, too. "When the flow rate is increased, you perceive the air temperature as much lower," says Joon-Ho Choi, an assistant professor of building science at the University of Southern California. That's why even a bit of a breeze feels so refreshing. But if you're sitting by a vent that's constantly blowing air across your desk, you'll feel colder, even if the air isn't necessarily uncomfortably cold.

Usually, though, the air coming out of the vent is 10 to 15 degrees colder than the room's target temperature–since that flow of air warms up the farther it travels through the warm building. So someone sitting right next to an air conditioning vent might be shopping for a space heater while a few rows away, another employee is sweating.

Of course, personal preferences play a role. Various studies indicate that women may be less tolerant of cold temperatures than men, for one thing. Dress codes make a difference, too. Men who wear full suits to work need the office to be a bit chillier to stay comfortable than women who wear sleeveless dresses. 

The industry mainstay as to what is a comfortable temperature may, in fact, be skewed toward the former demographic. ASHRAE Standard 55 is a widely used building code developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers to standardize temperatures of large buildings. Its mathematical model of comfort is calculated according to factors like air temperature, humidity, activity level, and clothing insulation. But often, building temperatures are set using men in suits as the standard occupants, leaving women–and anyone else who wears summer-appropriate attire–out in the cold.

Designers are figuring out ways to make buildings more comfortable in the summer, though. One method is simple: Let people open the windows. When you put people in an enclosed space with only artificial air, they tend to expect for it to feel perfectly comfortable. "When you introduce choice–allow for personalization and control–clients are willing to accept a greater range of temperatures," says Ryan Mullenix, a partner at global architecture firm NBBJ. The firm has used operable windows in several of its commercial projects, including in its Seattle headquarters. To discourage people from opening windows at inopportune times, like during a rainstorm, there's a light system installed in the wall. Based on humidity and air quality, the lights flash green to indicate it's a good time for fresh air, and yellow to indicate that the window should stay closed.

For employees who don't have access to an open window, an app and software system called Comfy aims to make it easier to control the office climate. Once hooked up to a building's HVAC system, Comfy acts as kind of a personal thermostat, allowing people to request warmer or cooler air to their zone of the office via smartphone. A pilot program over several seasons at a corporate office in Milwaukee resulted in 23% less energy usage by the HVAC system, according to one of Comfy's designers.

Freezing offices have costs beyond making employees uncomfortable. Blasting the A/C increases a building's operating expenses. The General Services Administration estimates that raising the temperature in federal buildings just 2 degrees in the summer would save the government $1.87 million per year. The cold also makes workers less productive. In 2004, a Cornell University study found that increasing office temperatures from 68 degrees Fahrenheit to 77 degrees Fahrenheit led workers to type more and make fewer errors in typing. The optimal temperature range for workplaces during the summer is between 74 and 76 degrees Fahrenheit, according to study author Alan Hedge.

So if you're feeling a little unproductive this summer, don't blame those summer Fridays. Blame your building's crappy HVAC system.