Florida is known throughout the world for its warm, tropical climate, but the consistent heat and humidity of the warmer months, especially in Southern Florida, come at a cost.

“Temperatures affect a lot of our construction work here, whether it be through energy consumption or issues with regards to the quality of construction years down the road. Materials deteriorate faster here than in a climate that is drier with less humidity,” said Jason Brown, Construction Manager for Miami-Dade County Parks, Recreation and Open Spaces.

These concerns for construction maintenance will only get worse as temperatures continue to rise. Miami-Dade County notes on their website that since 1970, the number of days in a year with a high above 90℉ has increased by 49 days, from 84 to 133.

The application process

The building for the Miami-Dade County project is a 2,000 sq ft single-level building. It contains one wall-mount air conditioner. The roof is 8 ft off the ground and surrounded by black concrete with all-day sun exposure. The existing cap sheet was not new, but did meet county requirements for all buildings to have cool roofs. It was cleaned with a blower, and paint was applied over the course of two days, with a primer on the first day and the Pirta paint applied the second day.

The power of passive cooling

The building was not used for about a month after applying Pirta paint to the roof. When Jason and his team returned for a staff meeting, they found that the room was significantly colder than usual. They have since purchased a thermostat to regulate the use of the wall air conditioning unit so that the room doesn’t become too cold.

“The results were huge,” said Jason. “Before, it was always humid in there and uncomfortable, but with Pirta, when we went back in there it was freezing. We had to turn the AC down.”

Jason and his team are excited about the results of this pilot project and hopeful that they will be able to use Pirta on more of their buildings in the future.

Financial analysis

An average wall AC unit uses 900 watts of electricity per hour. The rough cost of energy in Miami-Dade County is 15 ¢/kWh. If the AC unit is usually running for 12 hours a day, Pirta paint could save the county roughly $300 per year if they are able to cut air conditioning use in half for this one 2,000 square foot building.