For architects, windows have always been a trade-off: they make a building more aesthetically pleasant, but they also leave it colder in the winter and hotter in the summer. Now that highly insulating, energy-efficient windows are available off the shelf from companies such as Serious Materials, however, it’s not necessary to make that trade-off anymore. The technologies involved have been around for a while, but in the past these highly insulating windows were custom items. Serious Materials’ innovation was to mass-produce and mass-market them.

Retrofitting commercial buildings with highly insulating windows is an investment that can pay off in five years.  Since commercial spaces vary widely in terms of square footage, orientation to the sun, local climate, and many other factors, not all savings will be the same. But in one prominent example, Serious Materials upgraded the windows in the Empire State Building in New York City last year. The entire upgrade of the building, which included other measures, cost $20 million and will save an estimated $4.4 million per year on electricity costs. The window upgrades will account for $412,000 of those annual savings, according to an analysis commissioned by the building’s owner. (Serious Materials won’t disclose how much it was paid.)

“If you are already retrofitting, putting in high-efficiency windows is a no-brainer,” says Alan Meier, a senior scientist in the energy analysis department at the Lawrence Berkeley National Laboratory. Meier estimates that installing better windows alone will lead to maximum energy savings of about 10 percent. But if the window upgrades are happening at the same time as an upgrade of the building’s heating and cooling systems, they can pay for themselves immediately. One reason is that a building that has better windows might need a smaller, less expensive air-conditioner.

Brian Sipes, a principal at the architecture firm Zehren and Associates in Avon, Colorado, incorporated Serious Materials’ windows into designs for a building that he hopes will get the highest certification possible from the U.S. Green Building Council, whose set of standards, called LEED, is used to rank buildings according to their energy consumption and use of resources. Sipes says his firm chose the windows because they provided better insulation than anything else on the market. Fifteen or 20 years ago, he notes, there were hardly any green building products readily available to builders. “Now there are so many choices, and they’re choices that don’t force you to sacrifice between aesthetics and amazing energy efficiency,” he says.

Improving a building’s energy efficiency takes not just money but time. There are companies, such as Chevron Energy Solutions, that will put up the capital for basic efficiency upgrades, then split the return on the investment with building owners. However, says Meier, these types of evaluations often don’t go very far. Putting in the effort to identify less obvious sources of energy savings ultimately pays off.

Stephen Selkowitz, head of the building technologies program at Lawrence Berkeley, notes another benefit to upgrading buildings for efficiency: it can increase the value of the property. New laws in several states, including California, Massachusetts, and New York, require anyone selling a building to disclose what infrastructure is in place for energy efficiency and how high the energy bills are.