Posted on June 27, 2014
Making the commitment to seal and insulate your home may not generate as much buzz in the neighborhood as installing a solar array on your roof or upgrading to the latest high-tech air conditioning system. Caulking and fiberglass batts aren’t just low-tech; they’re no-tech. Nevertheless, few other measures will result in more immediate bottom-line savings on your utility bills than the undramatic act of sealing air leaks and insulating to reduce heat gain and loss. In addition, a lot of the work required to adequately seal and insulate your home is perfectly suited to the average DIY-inclined homeowner with a weekend to spare.
It's Not Rocket ScienceWhen good houses go bad due to poor efficiency and inconsistent comfort control, homeowners frequently over-think the issue. It’s tempting to gravitate toward complex causes and solutions – and even enduring energy myths – rather than the simple no-brainer option to seal and insulate your home. But the fact is, the most common causes for high energy costs and low comfort today are the same issues that homeowners have faced for generations: air leakage and heat transfer. Air leakage usually is driven by pressure differentials. When the air pressure indoors is greater or less than the outdoor air pressure, air currents seep out or in through myriad minute cracks and gaps in the home’s structural envelope. Heat and coolness move in and out and moisture can infiltrate to stay. Sealing these openings with caulking or weatherstripping stops air leakage and can result in immediate energy savings of 5 to 10 percent. Simple physics dictates that heat moves from a hotter zone to a cooler zone. Unfortunately, that motion is usually in the opposite direction of efficiency and comfort. During winter, precious warmth is trying to get out of the house, and during summer, uncomfortable heat is trying to invade. Heat transfers through ceilings and walls mainly by conduction and radiation. Insulation retards heat transfer and improves efficiency and comfort. If your home was built in the 20th century, it’s probably under-insulated by 21st century standards. Expected energy savings from upgrading insulation to the most current U.S. Department of Energy recommendations can be up to 10 percent.
Seal And SaveIn a typical home, the cumulative linear length of every crack, gap and crevice in the home’s structural envelope can add up to as much as 2,000 feet. This dismal status quo isn’t because you've neglected to seal and insulate your home. Many of these leaks were actually built in during the construction process – particularly if the house was built more than 20 years ago when energy conservation was a lower priority than construction costs. Others are the natural result of the aging process of building materials and years of normal wear and tear. The most immediate way to quantify the extent of leakage and the location of leaks is to start with an energy audit performed by an HVAC professional. A technician will peform a blower door test to calculate the total amount of air leakage. Technology such as a thermographic camera or a simple smoke pen also can be utilized by the auditor to image the movement of hot and cold air currents, and pinpoint and mark the location of leaks for later sealing by the homeowner. Simpler do-it-yourself methods also can be used to detect the location of air leaks. Hold a lighted stick of incense up to the margins of doors and windows and observe the smoke stream for signs of deflection due to air currents. For other leaks, turn on the lights in every room and walk the perimeter of the home after dark looking for light leaks that indicate cracks or gaps in the structural envelope. You’ll discover soon after beginning the process to seal and insulate your home that leaks tend to occur in predictable locations:
- Along the joints between floor and wall, as well as wall-to-wall joints in the interior and exterior.
- Around door frames and windows that open and close.
- At the intersection between the foundation and exterior wall siding.
- Around the penetration points where pipes and electrical conduits pass into the home.
- Along the chimney where it enters the attic.
- Where plumbing vent stacks pass through the ceiling and into the attic.
- In gaps around recessed ceiling light fixtures.
- Around attic hatchways and doors that lead to basement stairs.
Halting Heat TransferInsulation inhibits the movement of heat through solid materials but has little or no effect on air leakage. Installing new insulation may actually conceal air leaks, making them harder to detect. Make sure to seal and insulate your home in that order: seal first, then insulate. Home insulation interferes with the conduction and radiation of heat because the insulating material incorporates millions of pockets of trapped air. That’s the reason home insulation looks light and fluffy; it’s mostly air pockets. Air is a very poor conductor of heat energy so any air-filled material placed between a hot zone and a cold zone slows down the movement of heat. Two common types of insulation – fiberglass batts and loose-fill cellulose – are installed in the attic, the most common target for home insulation upgrades since heat rises into the attic during winter and conducts and radiates down into living spaces during summer. It’s also the most accessible area in the house to add insulation to existing layers. You can even mix different types of insulation on top of each other to reach the recommended depth.
- Fiberglass batts are roll-out insulation blankets sized for the openings between ceiling joists in the attic or the space between studs inside walls. You’ve probably seen the blankets that look like rolls of pink cotton candy stacked up in your local home center.
- Cellulose is a loose-fill product blown into your attic or wall voids through large hoses under air pressure. It’s composed of pulverized bits of paper – usually recycled newsprint – treated with fire retardant. Cellulose effectively fills all small openings and odd-sized spaces in the attic, resulting in superior coverage, but must usually be installed by professionals with air blowing equipment.
- For standard fiberglass batts in an uninsulated attic, the depth should be 10 inches to 19 inches. High density fiberglass can be 8 inches to 15 inches. To upgrade existing insulation, 8 inches to 12 inches and 6 inches to 9 inches, respectively, meet DOE requirements.
- Cellulose insulation in new attics should be 8 inches to 16 inches and 6 to 10 inches for upgrades.