By Solar Costa Rica
As a solar energy company, we hear from a lot of people who want to reduce their energy bills. Some, like us, want to “save the world” by using renewable energy, others want solar or battery backup because of blackouts and excessive power bills. Either way, the first step is to look at how much energy is being consumed in the first place.
Solar energy does not reduce your power consumption. It simply supplies electricity from a different source. The equipment for capturing solar energy is expensive, which means that the first step is to reduce your need for energy, thereby reducing the size—and cost—of the system.
Even if you don’t plan to invest in a solar or battery backup system, taking stock of the construction of your home or business and your energy use patterns is a great idea that may allow you to dramatically reduce your bills and increase your comfort! Humans are very adaptable animals; some simple adaptations to your home and habits could significantly improve your day-to-day experience.
For those who use it, air conditioning is generally responsible for the bulk of a home or business’ electrical consumption. The problem is, few buildings in Costa Rica are built appropriately for A/C. It’s true we don’t have to insulate against the cold here, but trying to air condition a space without adequate insulation to keep the heat on the outside is a recipe for outrageous power bills.
Real life example
Our office is in a warehouse-type space in Santa Ana. With high ceilings, low room dividers and a standard corrugated roof, we knew when we moved in that we were going to have to put some effort into making the space livable! Although we were working to improve our indoor environment without air conditioning, the exact same principles will apply if you are looking to reduce the cost of running an A/C unit.
Many Costa Rican buildings have little or no insulation, and our new office space was no exception. The two most common culprits for heat gain are the roof and the windows. In our case, the roof was our biggest challenge. With only a sheet of corrugated metal between us and the blazing sun, we had our work cut out for us!
Before moving into the space, we installed two skylights (for illumination) and a roof-mounted hot air extractor; the bubble-shaped kind with fins that catch the breeze and draw air up and out. We also installed two ceiling fans inside and, most importantly, insulated the underside of the roof.
Although white Styrofoam (open cell) is popular here and does provide a decent sound barrier, it is actually not very effective against heat. Styrofoam’s R-factor (insulation index) decreases at higher temperatures, and what’s more under a metal roof it will begin to outgas immediately, losing mass and eventually providing just the right amount of space for bats, tree rats and other critters! Instead, we used Prodex, a closed-cell flexible insulation material that comes on a roll. A single or, ideally, double layer of 3mm Prodex (with a little airspace between them) will go a long way toward blocking unwanted solar gain through your roof.
Once the underside of the roof was insulated, we painted the outside. Most painted roofs here are red or green, but white paint will reflect significantly more heat back away from your roof, noticeably reducing the solar gain. All of these measures did help, but we were still uncomfortably hot by mid-afternoon. We put a sprinkler on the roof, turning it on for brief periods as the day grew warmer and this, too, helped somewhat.
What really made the difference was a ceramic paint additive we bought in the U.S. The additive, a “super-reflector” developed by NASA for use on the space shuttles, comes as a powder to stir into standard paint (again, white). The week after we repainted the roof with the additive, one of our regular delivery guys walked into the office and said, “Hey, you got air conditioning!” Now, it’s not as cool as all that, but between the effective insulation and some attention to when we open and close the windows (open overnight to let the cool air in, closed when we arrive in the morning to keep it in), we have achieved a comfortable work environment under the blazing direct Santa Ana sun.