The selection of the correct thermal insulation system in the conditioned areas means obtaining significant energy savings. by Alfredo Sotolongo
The most economical energy to produce is the one that is saved! As I have always emphasized in these articles, the first step is to minimize energy waste through an effective maintenance program and avoid leaks and infiltrations to and from the conditioned areas. We achieve this through the use of the right materials, especially thermal insulation. ASHRAE adopts several climatological zones depending on latitude, for example: approximately north of the 26° parallel Zone 2 begins and from there to the north, the ASHRAE 90.1-2007 standard requires that all roofs of buildings have thermal insulation with R-20 resistance. While south of that parallel is Zone 1 which includes South Florida, the Caribbean islands and most of our countries between the Tropics of Cancer and Capricorn. In Zone 1 ASHRAE 90.1-2007 requires that the minimum thermal resistance is R13 on the roofs and also that the building envelope is properly sealed. Like the building, the air conditioning units, located on the roof, must observe that requirement. In the case of Zone 1 the thermal resistance of both the roof and the unit must be R13 to avoid wasting energy through the unit cabinet. Most conventional air conditioning units located on the roof use the cabinet with fiberglass insulation with metal only on the outer side, which represents thermal insulation of resistance R2. This means that, although the rest of the roof has R13, a significant energy leakage occurs through the units. Fortunately, most serious and responsible manufacturers offer the option of supplying such units with R13 resistance insulation for an additional cost. However, AAON is the only manufacturer that offers as standard insulation with thermal resistance R13 in the cabinet, using expanded polyurethane inside the double metal wall. Energy analyses prove that in Zone 1, depending on the cost of electricity in each of our countries, when using insulation with R13 resistance, savings in electricity consumption can represent between US$1,500 and US$6,000 per year for a 20-ton unit installed abroad. ASHRAE created the 90.1-2007 standard to contribute to energy savings and mainly protect the environment. But in our countries it represents much more than just the protection of the environment. Because the higher electricity consumption is represented by the air conditioning system and the increasing cost of electricity, any unit that is installed on the roof or outside of a building with thermal resistance R13 in its cabinet, contributes considerably to the conservation of energy. In my opinion, using units on the roof or outside of buildings with R13 insulation not only satisfies ASHRAE standards but is beneficial to the country's economy by helping to minimize oil consumption, especially if imported. If you need more information on any of the topics covered in this column, please contact me at the email [email protected] * President of Protec, Inc., is certified as a professional engineer in Puerto Rico and the state of Florida; he has more than 40 years of experience in the application and sale of systems and equipment for energy conservation. He is a member of ASME (American Society of Mechanical Engineers), AEE (Association of Energy Engineers), ASHRAE and was president of the Miami chapter of that association.