This article was originally published in the January/February 1996 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online January/February 1996
Michael Uniacke is the owner of Residential Energy Consulting in Prescott, Arizona, which specializes in educating builders, architects, HVAC contractors, and consumers on quality construction.
Twenty-five years after the first energy crisis, most newly constructed homes still lack the most basic energy conservation details.
A visit to homes under construction will reveal that builders are rarely utilizing the most basic energy-efficient building and design principles. Construction supervision on a custom or tract subdivision is an appearance- and schedule-driven process, and details such as the quality of the trim work, gypsum board finish, paint, cabinets, and final cleanup most often indicate a quality job to both the construction supervisor and the consumer.
The housing industry needs to redefine a quality job to include a high quality insulation system, airtight ducts, energy-efficient framing, and simple solar control strategies--benefits that the home buyer doesn't see until the utility bills come in.
Elements of Quality Construction
The general contractor also needs to give subcontractors clear information well before the job begins. For instance, a framer needs to know details during the bidding, not during wall erection. When clear construction details and expectations are coupled with informed supervision, many energy-efficient elements can be incorporated into the building process at little or no additional expense and only minor disruption of the construction process. Other energy-efficient practices and materials do cost builders more, but also provide large paybacks in reduced energy bills and increased comfort.
FramingSome carpenters are still framing buildings with conventional channels at exterior corners and at the intersection of interior and exterior walls. There are framing techniques that reduce the amount of lumber used in a house and permit insulators to do a better job. Twenty-four-inch on-center framing, three-stud corners, two-stud corners with drywall clips, ladder-back blocking, and insulated headers are a few approaches that can save money and significantly increase the effectiveness of the insulation system (see Figure 1).
Figure 1. Many contractors still use conventional construction procedures to provide nailing surfaces for drywall at intersections. These methods create gaps that cannot be insulated (see figures to left.) The figures to the right illustrate ways to avoid such gaps and allow complete insulation.
Airtight DuctworkIn the last 150 new homes I inspected, all of the duct systems leaked, and about one in four had catastrophic duct leakage. One local builder who specified an airtight duct system, but didn't test it, received a complaint from the homeowner about high utility bills. The builder then tested the ducts and found major return leaks in the crawlspace. The lesson the builder learned was that if he doesn't test, he may not be getting what he pays for from the contractor.
The HVAC contractor is responsible for the airtightness of the entire air distribution system. This includes framed cavities, such as platform return plenums and panned joists. A duct airtightness test can often be performed prior to installing gypsum board. This allows the installer to seal any discovered leaks. A test just before occupancy will not allow as much sealing, but can help to maintain quality control.
The North Carolina Alternative Energy Corporation has developed a standard target for duct leakage in new construction. The limit is determined in cubic feet per minute at 25 Pascals test pressure (CFM25). It can be calculated for each house by multiplying the livable floor area by 3%. For example, a 2,000 square feet home should have no more than 60 CFM25 of leakage in the air distribution system (2,000 x .03 = 60).
Telling someone to seal up a duct system is entirely different from training them to do the job correctly and following up with a test. HVAC contractors need numbers generated by a blower door or duct tester that give them feedback on how well they are doing.
A thorough inspection involves a complete visual examination of all attic spaces, walls, and crawlspaces. Inspectors must climb into the attic and through the crawlspace. Simply lifting the access hatch and peering into the attic does not constitute an inspection. The harder it is to inspect a space, the greater the likelihood of insulation problems.
Basic Air SealingAir sealing efforts should focus on getting the big leaks and controlling pressure differences in the house (see Air Sealing in Occupied Homes, HE Nov/Dec '95, p. 33). Pressure differences can occur due to duct leaks and an inadequate number of returns. Sealing the ducts and air handler, providing enough returns or pressure relief (transfer grilles) for closed-off rooms, and correctly sizing the ducts will help keep the house operating at a neutral pressure (see Duct Improvement in the Northwest, p. 21).
A blower door test provides vital information to both the general contractor and the technicians doing the air sealing work. The test does not take long to perform, and the feedback that the test provides to workers is invaluable. Simple air sealing techniques, coupled with insulation that assists in air sealing, should easily reduce leakage in a new house to less than 3 air changes per hour at 50 Pascals (ACH50).
Effective air sealing will only occur on a widespread basis if the process is simplified. Subcontractors make money by doing the same thing day in and day out. Every time a step is added to the process there is a greater risk that something will be missed.
The construction process can be simplified by using materials with inherent quality control, such as cellulose, blown-in fiberglass blankets or sprayed-in foam insulation. The performance of fiberglass batts depends too much on the quality of the installation. Batts can be installed in such a way that their rated R-value is compromised by as much as 30%-60%.
Wet-spray cellulose, spray foam, or alternate wall systems combine air sealing with insulation. These systems should be coupled with sill sealing and applying an expansive foam around windows and plumbing and electrical penetrations in top plates (see Urethane Foams and Air Leakage Control, HE July/Aug '95, p. 25).
If lights are to be recessed, insulation contact airtight (ICAT) recessed cans help to maintain an airtight shell and should be used. Insulation can be safely blown over these recessed cans.
Sealed combustion appliances eliminate the possibility of backdrafting, regardless of pressure imbalances in the house. Thus they provide inherent safety for the occupants.
By specifying materials like these, the builder can be more certain that the result will be a quality job.
If a contractor performs a heating and cooling load analysis on a house using the Air Conditioning Contractors of America's (ACCA) Manual J, the importance of controlling solar gain becomes very obvious. The rate of summer heat gain through an R-19 wall in Prescott, Arizona, is 0.9 Btuh/square foot, but it is 72 Btuh/square foot for east- and west-facing glazing. This means that 80 times more energy flows through a square foot of glazing than through a square foot of insulated wall area.
In climates with more heating load than cooling load, suntempering (increasing south-facing glazing up to 7% of the floor area) is a wonderful strategy to produce a more comfortable and energy-efficient home. A designer simply has to know how to orient the house correctly.
Properly Sized EquipmentMost air conditioners are oversized. A properly sized air conditioning system can help offset the cost of duct sealing and duct airtightness tests. Not only does oversized equipment hide problems with the building shell and ducts, but it is also less efficient due to short cycling. The HVAC contractor should perform a Manual J thermal analysis and use Manual D to size the ductwork (see Bigger Is Not Better--Sizing Air Conditioners Properly, HE May/June '95, p. 19).
How Can We Make Quality Happen?Improving the quality and efficiency of new construction requires the cooperation of all of the people involved in the process of building and buying a home. The elements and value of energy efficiency need to be understood by architects, builders, contractors, subcontractors, and consumers. A comprehensive effort at technology transfer is needed to build an effective information loop for all of these participants. This effort should focus on getting the basics right in all new building stock, not on expensive and complex methods to build superefficient houses.
The way to accomplish this is through high-quality training and education. Technology transfer needs to reach architects, builders, contractors, home buyers, and realtors.
Colleges and UniversitiesUniversities and community colleges should teach building science courses, particularly for students who are entering the building fields. Some universities are already doing this. For instance, within Portland State University's mechanical engineering department students can choose an emphasis on building science. These students take courses in HVAC design, commercial and residential building analysis, and fundamentals of building science. The courses bring students out in the field to apply what they learn in lectures to actual buildings.
Community colleges are another important setting for teaching students about energy use in buildings. Many students go to community colleges for two years to become technicians in the building and HVAC trades. Lane Community College in Eugene, Oregon, offers courses in building technology, which incorporate hands-on training in diagnostic tools and skills.
Programs like these are still much too rare, even though there is clearly a great need for them. They should be encouraged and funded at other schools.
UtilitiesUtilities have been in the energy efficiency business for many years and can play an important role in increasing efficiency in new construction. The problem with many utilities' traditional approach is that the battle is often waged in offices and not in the field.
Many utilities depend too much upon prescriptive programs, demonstration houses, and thermal analyses. Reality is what happens in the field, not in a software run; the job site and a computer simulation should never be confused.
Some utility rebate programs encourage investment in high-efficiency equipment as a stand-alone program, without any performance testing on the air distribution system. This is a prime example of the failure of technology transfer. It leads the homeowner to think that the equipment is all there is to it, and forces contractors to compete on that level. But if the ducts are very leaky, an investment in an air conditioner with a high Seasonal Energy Efficiency Ratio (SEER) or a furnace with a high Annual Fuel Utilization Efficiency (AFUE) will produce minimal savings.
Recently, one utility spent $800,000 on a demonstration house, filled with expensive state-of-the-art technology. That budget could pay for a lot of training for builders, HVAC contractors, architects, realtors, and homeowners. Utilities should make training programs, like the Energy Crafted Home program in New England, a larger part of their conservation efforts in residential new construction.
The most successful training programs make a strong connection to the job site. The more time spent teaching professionals to think independently, the greater the likelihood of success. Recently at a construction site, I pressurized a duct system with a Duct Blaster and then filled it with smoke from a theatrical machine. Seeing the smoke blow through the cracks and leaks in a supposedly airtight duct system created a paradigm shift--the duct installation crew suddenly understood what the builder was after.
Trainers must understand the design and construction process, and they must also empathize with their audience. Trainers should subject their own work to performance tests. If a training is successful, the participants should change their practices in the field.
MarketingConsumers will pay for superior systems only if they can see the benefits. Marketing training helps builders to feel confident that they will get a return on their investment in quality.
More progressive builders already incorporate insulation inspections, leakage standards and testing for duct systems, air sealing, efficient framing details, and controlled ventilation--and then capitalize on the fact that their competitors are deficient in these areas.
For marketing to work, potential home buyers need to be educated about the benefits of high quality efficient construction. Government, utilities, nonprofit organizations, and industry groups can all help to educate consumers.
Builders also have a role in educating consumers. Some builders hold workshops for people who are planning to have a home built, to inform them about what makes a quality job. A customer who is educated about energy, health, and safety issues will be the best customer for a quality builder. This customer will understand that a lower bid offered by a competitor is for a different job.
Quality HVAC contractors are also beginning to hold workshops for their clients-the builders. It is vital that participants in different parts of the building process educate one another about the definition of quality work.
Is the Key The bottom line is that the people who really need the information about quality building are often not getting it. Quality will be built consistently into homes only when we acknowledge the difficulties and obstacles in the construction process and begin to show more empathy with the mainstream builder. The building science community should be championing products that are easy to install and inherently efficient. The real challenge is not to squeeze more efficiency out of an energy-efficient home, but to transfer our current understanding of home performance to the mainstream building community.
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