The Northeast Florida Builders Association and JEA have created Green Built Homes of Florida to help builders and homeowners increase the energy and water efficiency of new homes. A major component of the Green Built Homes of Florida program is meeting Energy Star criteria, and tight construction is crucial to achieving Energy Star compliance. Air leakage is a major problem in both new and existing homes, especially in Florida’s hot and humid climate. Air leakage accounts for 25 percent to 40 percent of the heating and cooling costs in a typical home. Since heating and cooling accounts for nearly half the monthly energy used by the home, a home’s air leakage can have quite an impact on the pocketbook. Building envelope improvements and air sealing play a big role in achieving Energy Star performance standards. By reducing air infiltration through tighter house construction, the following improvements to the home can be achieved:
Improved comfort - reduces drafts, noise, and moisture.
Improved indoor air quality - keeps dust, pollen, car exhaust, and insects out of the home.
Lower costs - reduces escape of conditioned air or infiltration of unconditioned air.
Durability - reduces unwanted moisture, mold and mildew to provide long term performance and durability.
Reducing air leakage effectively requires a continuous air barrier system to create a tight building envelope. Unfortunately, there are hundreds of penetrations through a typical home’s exterior. These gaps and holes are often incurred during framing and from penetrations for wiring, plumbing and ducts. Air sealing the house’s envelope, combined with proper ventilation, can reduce your energy bills and eliminate unwanted drafts and pollutants.
Today, off-the-shelf technologies, such as house wraps, sealants, foams, and tapes, reduce air infiltration. House wraps serve as exterior air barriers and help prevent bulk water penetration. Although house wraps can reduce air leakage, it is not a substitute for the airtight drywall approach, which uses interior wall systems to form a continuous barrier to air penetration. Caulk, gaskets, tape, and weather-stripping need to be used in combination with sheet material such as plywood, house wraps, and drywall, to achieve proper air infiltration values.
Builders should work with their crew and subcontractors to ensure a continuous air barrier is achieved by both the external and internal walls through the proper use of these materials. In energy-efficient homes, builders seal the myriad of cracks and gaps in framing along with hundreds of holes for plumbing, mechanical equipment, sill plates, and electrical wiring. Examples of this include:
• Doing a very good job taping all of the edges of the house wrap.
• Sealing all of the penetrations through both the interior and exterior walls with caulk, foam or tape.
• Ensuring all bypasses that can be hidden from view behind soffits, bath fixtures, cabinets, etc. are sealed.
• Ensuring all penetrations through the top plate are sealed and the bottom plate has a gasket.
• Sealing the electrical boxes.
• Ensuring flue stacks, ceiling fans, and recessed lights are sealed properly.
• Sealing all of the gaps around doors and windows.
• Insulation can also play a factor in tight construction. Proper installation of batt and blown insulation can help prevent air infiltration and also reduce thermal convection and conductance. Newer spray-on insulations can serve as excellent air and thermal barriers to provide the home with the tight construction it needs to be more energy efficient.
Once all of these materials and techniques are implemented, the home can be tested to see if it meets Energy Star standards. Currently, a blower-door test is performed on the home by a Class 1 Certified Energy Rater. This test places a negative pressure inside the home with a blower fan and calculates the amount of air that is allowed to “leak by” all of the penetrations that weren’t sealed properly and enter the conditioned space of the home. This value is then used as part of a whole home formula to determine Energy Star certification. The EPA will be adjusting its Energy Star guidelines near the end of the year and a rater will need to also perform a Thermal Bypass Inspection Checklist to ensure that proper construction practices were performed to achieve a tight home.
For technical assistance on qualifying for an Energy Star home, call David Reed of JEA at 665-6590.