As Florida heats up, architects look to ‘passive cooling’ home designs

Jul 23, 2023

Jack Parker, a longtime environmental science professor at Florida International University, built his house from the ground up to use as little electricity as possible and take advantage of South Florida’s natural cooling forces.

The place was angled to catch prevailing breezes and shaded by strategically planted trees. Plentiful windows allowed air flow and vented hot air. It used about one-sixth the power of surrounding homes, saving money and also the family’s sanity after Hurricane Andrew struck in the muggy depths of August 1992 and knocked out power for 11 days.

“We were the only ones in our whole neighborhood that could sleep at night because we could open the windows,” Parker said. “Everybody else was in their homes really sweating and suffering from the heat.”

Parker built that Kendall home way back in 1984, but its “passive cooling” approach never really caught on as South Florida continued to boom. At least until now. As climate change drives temperatures and cooling costs higher, some architects and homebuyers are beginning to employ designs developed long before air conditioning — all the way back to the deep porches of cracker cottages and the elevated chickee huts of South Florida’s first inhabitants.

“There have been more designers willing to reincorporate passive design strategies in their projects,” said Sonia Chao, the associate dean of research at the University of Miami School of Architecture. “I suspect that as climate stressors … continue to impact our communities more consistently, a greater number of clients will demand that their designers incorporate such features, if for no other reason than to reduce their own utility costs.”

Cool building designs can keep people more comfortable during record-breaking summer heatwaves. But they also promise to reduce the amount of electricity homes use for air conditioning while also reducing the carbon emissions that are raising global temperatures.

“If you do this properly, you’re going to end up saving money … and you’re reducing the carbon pollution that goes with that,” Parker said.

Lately, architects designing high-end houses for wealthy, climate-conscious buyers have started working cooling techniques that were once common into their contemporary designs.

Take, for instance, the $15.2 million “Prairie House” on Miami Beach, a three-bedroom 3,200-square-foot luxury home designed by the Miami architect René Gonzalez. The building is designed to be “porous,” full of courtyards, breezeways and open spaces that allow breezes to flow through. The entire structure is elevated 14 feet above the ground, which not only allows the building to dodge floods, but also allows cool air to circulate under the floor.

A single courtyard can lower a building’s energy bill by about 7% on average, according to a 2021 study from Spanish researchers at the universities of Cadiz and Seville.

In addition to the Prairie Residence’s courtyards and breezeways, plants grow on the roof and glass walls retract on cool days and nights to let in the breeze. Gonzalez dotted the property with shade trees and water features to cool off the air as it flows through.

“The effect is not only physical but it’s also psychological,” Gonzalez said. “The idea that you have air flowing around you and you see spaces and you see a water element or a pool also psychologically makes you feel cooler.”

Architects have other cooling tricks up their sleeves. In a house she built for a family in Punta Gorda, Miami architect Suzanne Martinson extended the roof 10 feet beyond the windows and sliding glass doors to shade the interior. The house is only one room wide, with big windows that can be thrown open to let air flow easily across the building.

“We’re unusual because we’re in a tropical environment where the humidity is high,” Martinson said. “In a humid climate, the way to stay cool is to have air moving across your body and your skin, so you’ve got to have moving air.”

Martinson also raised the ceilings up 10 feet and placed ceiling fans in each room to help hot air rise above the heads of the people inside.

Finally, shaded porches — a staple of southern architecture — can be a great way to keep a building cool, according to Chao. In addition to giving people a place to sit in the breeze and cool off, deep porches also shade exterior walls, especially south- or west-facing walls that otherwise bake in the afternoon sun.

“When you have porches on the right side of the building … the sun’s rays never reach the wall that’s protecting the interior room,” Chao said. “That wall is not gaining any heat, which means you need less electricity to cool that space.”

Porches don’t just work for single-family homes. They can also be worked into much larger buildings, like the Perez Art Museum Miami, which has an east wall shaded by a massive porch overlooking Biscayne Bay.

It used to be common to build like this in South Florida. Gonzalez, for instance, takes design inspiration from the region’s earliest inhabitants.

“It’s about building in the same way that the natives have built,” he said. “If you look at chickee huts and early Native American structures, you’ll see that they’re elevated off the ground, they’re very [open] and they’re generally oriented so they allow the southeast breezes we have here in South Florida to flow in and out the other side.”

In Florida’s frontier days, many settlers built their houses using the same ideas. Often, that meant “narrow buildings, preferably oriented along an east/west axis, with deep porches on the southern side of the building or the strategic placement of trees, and finally, tall operable windows lined up across from each other,” Chao said.

“Interior spaces were usually taller and often ceilings were pitched and some had an opening towards the top to let the hot air rise and exit the structure,” she said, adding that many buildings also had crawl spaces that allowed air to circulate beneath the floorboards and louvered shutters that let air flow through while blocking light.

The Barnacle, a historic house built in 1891 in Coconut Grove, used many of these techniques to keep occupants cool before air conditioning.

Cooling techniques became iconic parts of the region’s architectural landscape. Many of the Art Deco buildings that line Miami Beach, for instance, have deep “eyebrow” ledges over their windows that shade the interior in addition to lending the facade an aesthetic flourish.

South Florida’s classic cooling designs slowly began to fade after World War II, when air conditioning gradually became cheaper and more pervasive, according to Chao. “As that started to happen,” she said, “developers started to say, ‘Aha! I no longer need [passive cooling] elements because people can live in the building without the porch, without operable windows, without shutters because the air conditioning is going to make the space comfortable.”

“By the 1970s, unfortunately, most buildings were put together in completely different way,” she said.

With some exceptions, many newer houses were built with windows that didn’t open, without porches, overhangs or shade trees on the lot. With A/C ducts snaking from room to room, buildings weren’t designed for cross-ventilation. Despite the increasing temperatures, that remains the dominant design. Just consider the trendy modern “sugar cube” mansions going up across South Florida.

“Today, it is common for us to find the same cookie-cutter design in South Florida as in Alaska,” Chao said. “Unfortunately, South Florida homes are no longer built with climate zone considerations and we have mechanical air conditioning to thank for that.”

Cooler building designs have dual benefits. They offer a way to lower energy bills — and carbon emissions — by reducing the amount of energy people need to use to keep their homes and businesses comfortable throughout the year. Cooling alone typically represents about 60% of Floridians’ power bills, according to FPL.

Of course, that doesn’t mean people need to live without air conditioning on the hottest days of summer.

“It’s not a matter of suggesting that you’re going to always live here with your doors open,” Gonzalez said. “The heat here, as is getting to be the case everywhere in the world, is extreme during the summer months. But during the winter months, we have very nice weather and we have many days on which you have the ability to open up.”

But you can only “open up” to the breeze if your home has windows that open and a layout that allows air to flow through. Some modern houses are now built with fixed windows that can’t open, according to Martinson.

“Developers and clients are doing that because an operable window costs more and it’s a savings, but it’s a shame that they can’t open them to enjoy the breeze when there is one or the nice weather in the winter,” she said.

READ MORE: A battle over the soul of Miami Beach: Will developers destroy or save Art Deco?

The other challenge, Martinson said, is South Florida’s cool winter days are becoming a rarity. “It has gotten so much hotter,” she said. “I’ve been here since the ‘50s when my family moved here and you could be outside in the summer. There was more of a canopy in Miami and you could be in the shade and be totally comfortable. But that isn’t the case now.”

Recent studies verify that. In the 1960s, daily temperatures hit 90 degrees for about a quarter of the year. Now, 90-degree days account for a third of the year. By 2050, scientists expect South Floridians to sweat through 90-degree days for more than half the year.

In the meantime, Miami’s rapid development has replaced trees and plants with concrete and asphalt, contributing to the “urban heat island effect.” Miami has become one of the hottest concrete jungles in the country, according to a recent report from the nonprofit research group Climate Central.

Miami’s warming trend makes it all the more urgent to start designing buildings to be more resilient to extreme heat, according to Chao — particularly for the less-affluent.

“In particular we should be thoughtful about how poorer community members are impacted by extreme heat, because they may not be able to afford to run that air conditioning system 24/7,” she said. “That’s why it’s particularly important to start to build immediately in this more thoughtful, planet-savvy manner when we’re doing so for affordable or workforce housing.”

“We’re talking not only about how much energy they consume, but we’re actually talking about their health and safety and welfare,” Chao said.

Designing cooler buildings doesn’t have to break the bank. Gonzalez knows most people could never afford to live in a home as luxe has his Prairie House. “This is not a cheap house,” he said. “But some of the strategies we used here are inexpensive and easy to apply.”

Planting shade trees on the property, using breezeways or courtyards to let air flow through a building and installing windows that can open to let in a breeze are all relatively affordable design techniques — even if the Prairie House’s rooftop jacuzzis and 10-foot elevation are not.

“Passive design is not a matter of style nor is it complicated nor more expensive necessarily in the hands of an expert,” Chao said.

A prime early example: Parker and his wife Janat, an FIU psychology professor, were both on academic salaries when they built their energy efficient home almost 40 years ago.

The two-story house in The Crossings has 37 windows with ceilings designed to capture hot air as it rises indoors and vent it through a set of windows high in the second floor walls. Parker even oriented the house at a slight angle from the street so that it would face South Florida’s prevailing southeasterly breezes.

For the dog days of summer, when mere breezes wouldn’t cut it, Parker bought the most efficient air conditioner he could find and set it up to just cool the bedrooms on the second floor. Then he strategically planted 50 trees on his quarter-acre lot to offer maximum shade to the A/C condenser in his yard and the south-facing wall and windows.

All that — land, house, high-efficiency appliances — cost him roughly $367,000 in today’s dollars. Before building his house, Parker had toured other ultra-efficient model homes designed to use little energy. “But they were all super expensive, basically for millionaires, so I didn’t want that,” Parker said. “I wanted to have one that was going to be reasonably cost-effective.”

Parker finally left his beloved home in 2019 to move to a retirement community in Asheville, North Carolina. There, he can’t control the landscaping or install ultra-efficient appliances. But he has been circulating newsletters to his neighbors to urge them to use less electricity by raising thermostats, using fans to circulate air and making sure doors and windows are snugly sealed when the air conditioner is running.

“Every house has to contribute to the solution to this,” he said, “so anything that each one of us can do, I think that’s important.” This climate report is funded by Florida International University and the David and Christina Martin Family Foundation in partnership with Journalism Funding Partners. The Miami Herald retains editorial control of all content.

This climate report is funded by Florida International University and the David and Christina Martin Family Foundation in partnership with Journalism Funding Partners. The Miami Herald retains editorial control of all content.

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