The Elephant in the Room
September 01, 2009
A version of this article appears in the September/October 2009 issue of Home Energy Magazine.
|David Butler has practiced as a building systems engineer for more than two decades. During this time he has consulted with multinational manufacturers, energy utilities, and land developers on a variety of R&D projects focused on energy efficiency. During the 1990s, Butler produced the weekly column At Home with Technology, which appeared in newspapers nationwide. Butler currently resides in the high desert of southeast Arizona, where he spends most of his time performing load calculations for high- performance homes. He is an associate member of ASHRAE and sits on the review committee responsible for ACCA’s widely referenced residential design manuals.|
Purpose-built high-performance homes, once a niche market, have moved into the mainstream. Although many factors contributed to this market transformation, none is more important moving forward than verification and certification. Without an independent set of eyes on a project, home buyers have no idea what level of performance they’re getting.
Trust, but Verify
Virtually all builders and real estate professionals understand that green and energy efficient are desirable attributes in today’s market. Many builders jump on the green bandwagon for competitive reasons, often without professional guidance. This often leads to unwise choices when it comes to energy efficiency.
When selecting efficiency measures, builders tend to rely on recommendations from suppliers, trade magazines, and worst of all, hearsay. Unsubstantiated claims are rampant, especially claims involving energy efficiency and potential energy savings. The basics often get overlooked in favor of more tangible (but often inappropriate) efficiency upgrades.
Home buyers are even less qualified to separate the wheat from the chaff. And those who make a serious effort to self-educate often make poor choices because much of the available information is overgeneralized, misguided, or taken out of context. When it comes to home energy efficiency, myths abound and conventional wisdom often lets us down.
Most builders don’t realize that achieving energy efficiency is as much about quality assurance and construction techniques as it is about choosing the right building components. Indeed, much of what makes a home efficient is either invisible or hidden behind the walls. For this reason, an effective energy efficiency program must include on-site inspections and diagnostic testing by an independent specialist, thus allowing the home to be certified as having met specific performance requirements.
|For all the training and experience in envelope design, advanced framing, and whole-house diagnostics, the home performance industry is largely unprepared to provide HVAC guidance.|
Verification and certification represents the lowest of the low-hanging fruit. It not only ensures that the basics have been met, but provides an objective yardstick for evaluating the cumulative effects of potential improvements. Trying to build an efficient home without verification and certification is like trying to treat a serious disease without a medical exam. Either way, the odds are against a positive outcome.
The Energy Star-Certified Homes program deserves much of the credit for bringing high performance to the mass market. Aside from being a widely recognized and respected brand, Energy Star accomplished that which previously eluded industry pioneers by creating a uniform verification and certification procedure that could be replicated in mass at a reasonable cost.
The number of Energy Star-certified homes will soon pass the one million mark, through its network of over 5,500 participating builders. Indeed, entire communities of high- performance homes are being built in large and small markets across the country. Moreover, serious inroads are being made toward achieving net zero energy communities at reasonable price points.
The Elephant in the Room
Progress on this scale couldn’t happen without significant collaboration between builders and home performance professionals. By participating in a verified efficiency program, the builder gains a knowledgeable partner—an expert who can assist with design and construction details, and work on the front lines to help retrain key trades—especially framers, insulators, and HVAC subcontractors.
However, for all the training and experience in envelope design, advanced framing, and whole-house diagnostics, the home performance industry is largely unprepared to provide HVAC guidance. This is incredibly ironic, considering that HVAC is by far the largest energy user in the home. When it comes to high-performance homes, HVAC is the elephant in the room. To understand how this happened, one need only consider the origins of the energy conservation movement. Many industry pioneers came out of the utility- and government-funded weatherization programs of the late 1970s and early 1980s. Others cut their teeth on solar water heaters, newly energized by the 1978 federal tax credit. And then there were the generalists, deeply rooted in self-sufficiency and ecology. For the most part, HVAC expertise was nowhere to be found.
Early conservation efforts targeted windows and insulation. Rightly so. At the time, many homes still had leaky single-pane windows and little or no insulation. Although heating and cooling energy use benefited from shell improvements, little attention was given to the HVAC system itself.
That changed in 1992 with the introduction of federal efficiency standards for furnaces, boilers, and air conditioners. This emphasis on source equipment (”box”) efficiency ignores the even larger impact of poor design and installation practice. Indeed, as the building envelope and source equipment have become more efficient, HVAC design and installation quality remains mired in mediocrity, until now it has become the Achilles’ heel of home performance.
Field studies have consistently shown that design and installation issues have a far greater impact on overall system efficiency than box efficiency ratings. SEER, annual fuel utilization efficiency (AFUE), and heating seasonal performance factor (HSPF) are theoretical ratings based on standard operating conditions. The efficiencies signified by these ratings can be approached only when equipment is sized correctly and delivery system losses are ignored.
In the real world, poor HVAC design and installation practice (arguably) accounts for more energy waste in new homes than any other single factor. Unfortunately, in the real world it’s easier to sell high-efficiency boxes than high-efficiency systems, a distinction invariably lost in a competitive marketplace. As a result, HVAC remains the weakest link in most high-performance homes.
The solution must begin with an educated builder. The home performance industry has successfully used this strategy to help transform other key trades, such as framing and insulation. But with virtually no training in duct design or equipment sizing and selection, most home performance practitioners are ill prepared to take on HVAC, the most technically demanding of all trades.
Today, the home performance industry is beginning to pay more attention to the HVAC system. Energy Star took a step forward by requiring duct tests. But with leakage limits based on conditioned floor area (as opposed to nominal fan flow), the test becomes meaningless when applied to high-performance homes with downsized HVAC systems.
(My previous home in Charlotte, North Carolina, illustrates how Energy Star’s 6% duct leakage requirement is useless when applied to a moderately high-performance home. The home had only 2 tons of cooling capacity for 3,200 square feet. This means a Duct Blaster reading of 192 CFM25 would pass muster, even though that represents nearly 25% of the system’s nominal fan flow of 800 CFM!)
Moreover, sealing leaky ducts can actually reduce cooling system efficiency and even cause the coils to freeze up if the ducts are undersized to begin with. Very little in building science operates in isolation. The systems approach is always the best approach.
Taming the Elephant: Education Is the Key
For the vast majority of new homes, the builder is ultimately responsible for making the decisions that determine the home’s energy performance. As a result of Energy Star and other verified energy efficiency programs, builders are increasingly looking to home performance professionals for guidance. We must continue to educate ourselves so that we can live up to this challenge.
|Unfortunately, in the real world it’s easier to sell high-efficiency boxes than high-efficiency systems, a distinction invariably lost in a competitive marketplace.|
Heating and air conditioning account for the lion’s share of home energy use, so it stands to reason that a major part of our efforts should be directed toward helping builders make better decisions when it comes to spending their HVAC dollars. Given the history of the home performance industry and the complexities of the HVAC trade, this has proven to be exceptionally difficult to achieve.
Further exacerbating the problem is the current state of the HVAC industry, especially the new-construction end of the business. It’s no overstatement to say that the residential HVAC industry is broken. Market pressures tend to drive down technician skill levels to the lowest common denominator, and penalize contractors who aspire to do things right. There’s little incentive to do better when the market doesn’t place value on careful design and quality workmanship.
Moreover, the HVAC industry has failed to address the unique design challenges associated with high-performance homes, leaving tradesmen mostly to fend for themselves. On the other hand, the home performance industry offers little more than a duct leakage test, lip service for rightsizing, and a prescription for high-efficiency equipment. Good design practice is usually taken for granted.
Energy Star 3, with its increased emphasis on best-practice HVAC installation, will soon put an exclamation point on the need for more rigorous HVAC training for raters and providers. It’s time for RESNET to give serious consideration to advanced certification for HVAC competency.
Home performance professionals who endeavor to learn essential HVAC skills can make a real difference, in terms of both comfort and energy efficiency. And while it’s not necessary to become a proficient HVAC designer or refrigeration technician, it’s important to understand the overall design process and pitfalls, especially the nuances of high-performance homes. Familiarity with the procedures outlined in ACCA Manuals J, D, S, and RS would be a good start.
We must gain the respect of HVAC contractors by demonstrating our ability to deal with them on their level. This takes knowledge, experience, confidence, and above all, a spirit of teamwork. Nothing positive comes out of an adversarial relationship.
Conscientious HVAC contractors with strong design skills and well-trained crews will appreciate having an advocate for high-quality design and installation practice. They may be less thrilled when their new friend recommends against their most profitable high-end equipment. Be prepared to defend your recommendations with sound analysis.
HVAC contractors need more training in the use of computer modeling tools such as REM:Rate. These tools have become increasingly versatile and accurate, allowing the skilled user to quickly evaluate competing efficiency improvements. But the most egregious misapplications of resources in terms of cost-benefit can be evaluated on the back of a napkin. All that’s required is a good sense of the relative contributions to the energy pie, a handle on local energy costs, and the formula to convert between kWh and Btu. This can and should be taught as well.
Payback analysis is only one dimension of the building science puzzle. Design decisions must also be evaluated against sometimes competing objectives of comfort, structural durability, and safety. Moreover, home performance practitioners are increasingly being asked to consider the environmental impact of their work. Fortunately, a properly designed and installed HVAC system will simultaneously excel in all of these areas. On the other hand, a poorly done system can drain a bank account, cause chronic discomfort, rot a home’s structure, kill the occupants, and contribute to global warming!
Finally, education does not end with the builder. Home performance professionals must help builders and HVAC contractors educate the homeowners. We should provide builders with written materials. For example, if homeowners were to understand the many downsides of oversized HVAC equipment, they would be more willing to tolerate an air conditioner that falls a little short on an exceptionally hot day.
>> For more information:
To learn more about independent load calculation and HVAC design go to www.acrightsize.com.
- FIRST PAGE
- PREVIOUS PAGE
© Home Energy Magazine 2018, all rights reserved. For permission to reprint, please send an e-mail to firstname.lastname@example.org.
Enter your comments in the box below:
(Please note that all comments are subject to review prior to posting.)
While we will do our best to monitor all comments and blog posts for accuracy and relevancy, Home Energy is not responsible for content posted by our readers or third parties. Home Energy reserves the right to edit or remove comments or blog posts that do not meet our community guidelines.