At the heart of today’s most successful and innovative companies is design. It’s a discipline that has the power to improve every aspect of our lives.

A well-designed office is a happy office. As facilities managers strive to save space and cash, they’re reshuffling desks and fiddling with temperature gauges. All of which has an impact on workers’ performance. Open-plan offices may make some kinds of collaboration easier, but are they more conducive to productivity? What’s the most irritating workplace distraction? And are those state-of-the-art workstations actually more comfortable? Here’s the Quartz complete guide to open-plan offices:

Nearly three quarters of Americans work in open-plan offices

According to the International Management Facility Association, 70% of American employees work in open-plan offices.

The world’s largest open-plan office

Mark Zuckerberg hired Frank Gehry to design Facebook’s office expansion in Menlo Park in California. Once completed—its planning application has been approved and work is set to start imminently—the social network’s new digs will be the world’s largest open-plan office.

Workers in open-plan offices get sick more often

Workers who share an office take more sick days than those who work in their own closed spaces. A study in the Scandinavian Journal of Work, Environment and Health found that open office setups reported 62% more sick days on average than one-occupant layouts. It was the first national population study conducted in Denmark to find such a linkage. One suggested explanation, unsurprisingly, was that viruses and bacteria spread more easily in open offices. Another was that open offices are more stressful to work in because of the lack of privacy, and that the stress makes sickness more likely.

Workers don’t like noise

Researchers from the Hong Kong Polytechnic University wanted to study which aspects of office design had the biggest impact on workers’ productivity. CK Mak and YP Lui questioned 259 office workers about the importance of sound, temperature, office layout, air quality and lighting for productivity; they found that sound and temperature mattered the most. The most irritating noises were conversations, ringing phones and machines.

Older workers really don’t like noise

Mak and Lui also found that the environment mattered least to the younger participants in their study. Those over 45 were more sensitive to it, and factors like noise and temperature had a bigger effect on their productivity.

Open-plan offices are less productive

In a literature review of studies on open-plan offices, researchers from Virginia State University and North Carolina State University found evidence to suggest that they’re linked to lower productivity. Scanning work from the Journal of Human Ecology, Academy of Management Journal and Administrative Science Quarterly, Tonya Smith-Jackson and Katherine Klein identified reduced motivation, decreased job satisfaction and lower perceived privacy as factors negatively affecting productivity in open-plan environments. Similar to Mak and Lui findings, the resounding message in the research is that overhearing conversations in the office is very intrusive and distracting for workers.

Making offices open-plan isn’t a popular move

People work less well when they move from a personal office to an open-plan layout, according to a longitudinal study carried out by Calgary University. Writing in the Journal of Environment and Behavior, Aoife Brennan, Jasdeep Chugh and Theresa Kline found that such workers reported more stress, less satisfaction with their environment and less productivity. Brennan et al went back to survey the participants six months after the move and found not only that they were still unhappy with their new office, but that their team relations had broken down even further.

Fancy workstations don’t make much difference

Cornell researcher Alan Hedge wanted to find out what happened if offices provided employees with smaller, ergonomically designed desks. He concluded that they couldn’t be relied on as a space-saver because the workers couldn’t figure how to use them. Workers in the study were split down the middle as to whether the specially designed workstations were more comfortable and easier to work at than traditional (and larger) alternatives. Hedge did find that the employees who had been trained to use their equipment were more comfortable and productive than those who hadn’t. Turns out “ergonomic” doesn’t equate to “intuitive”.

Bad office conditions cost employers two and a half days a year

Writing in the Journal of Facilities Management, Dutch researcher Paul Roelofsen examined the effect of comfort levels in offices on productivity. Roelofsen knew from previous research that poor office conditions were causing absenteeism among Dutch employees. A survey of 7,000 Dutch workers found that they were absent for 2.5 days a year on average because of complaints about their office environment, most commonly related to temperature. Roelofsen also noted in his work that even among the workers who are present, if the environment isn’t ideal for them they won’t work as hard. He estimated that quality improvements yield between a 5% and 15% increase in productivity.