The days of discouraging 'high-risk' behavior by system designers must end
If a building owner has enough money for renewable-energy systems and the space to install them, any designer can achieve net-zero performance. Achieving net-zero performance economically, however, is a different matter.
Although the concept of "net-zero energy" has been with us since the energy crisis of the 1970s, the HVAC design industry still relies almost exclusively on fundamentally flawed, overly complex, mass-produced solutions that cannot be made to function properly. To achieve net-zero designs, we need to get back to engineering basics and practice fundamentally efficient design. We need custom solutions, and we need the skills to correctly evaluate and holistically apply strategies to meet a facility’s particular needs.
It is not a lack of technologies or barriers imposed by the laws of thermodynamics that impede our progress. It is our unwillingness to expand our horizons, analyze opportunities, develop application-specific solutions, and adopt appropriate techniques.
The real barriers to technological progress are those we impose on ourselves; it is our failure to use our skills and imagination that limit our ability to understand and properly analyze the opportunities and technological misconceptions that inhibit us from considering the technologies most necessary to practical solutions.
At this point, I think some important observations need to be shared:
Conventional HVAC systems throw away as much as 85 to 95 percent of the energy expended in buildings. However, with innovation and careful engineering, most of that waste can be eliminated or recycled. This was demonstrated at Wausau West High School where air-quality problems in an existing and uninsulated building were eliminated using 100-percent outdoor air, and total energy usage was cut 70 percent. This in spite of the fact the facility had previously been through a major energy-conservation project (see "Regenerative Dual Duct: A Case Study," HPAC Engineering, January 2009, or visit http://bit.ly/dualduct).
Similar results can be realized routinely. But this means building HVAC systems around different technologies to achieve different design objectives. It means applying a different system-design paradigm through which energy is recovered and/or transformed and new energy expenditures are avoided. The fact it has been accomplished defeats all arguments to the contrary.
Where We Need to Improve
The lack of an unambiguous, absolute, and universally accepted definition of a "high-performance" HVAC system is a huge problem. Similarly, when it comes to predicting building energy performance, one can argue there are "lies, damn lies, and computer simulations."
Computer simulations are complex and expensive. The budget model against which a proposed model is compared is not an efficient solution, but the most inefficient possible. Then, how does one predict the performance of an innovative system for which no computer model exists? Currently, under the requirements of ANSI/ASHRAE/IESNA Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, the analyst is required to game the simulation because the algorithms in existing simulation programs may not be able to model innovative systems. This permits false claims of performance.
Two things are needed. One is a design process that leads to the best solution every time. The second is a simple scalar mechanism to measure HVAC-system efficiency, similar to EER or SEER. Such comparisons should be made against a hypothetical best possible outcome, not the worst. Designers need a clear outcome for which to strive.
Characteristics of High-Performance Systems
High-performance HVAC systems share certain characteristics:
In addition, ventilation subsystems not only must efficiently process outdoor air, but should be able to manage it down to the individual-room level. This is simply, easily, and economically done using 100-percent outdoor air.
Achieving the highest-performing systems will involve the aggressive use of the following technologies, in addition to renewable-energy systems:
The Jury is Out
Are cost-effective, net-zero energy building designs possible? For certain types of facilities, yes. For others, the jury still is out.
HVAC systems will never get to net-zero by themselves, but they can be made significantly more efficient. However, getting there cost-effectively means eliminating designed-in waste and integrating building systems to retain previously expended assets for future use.
We cannot get to net-zero with the strategies, systems, and solutions of the past. The HVAC design community ultimately will need to abandon those strategies and learn not only how to design fundamentally efficient solutions, but how to apply the principles of high-performance design. We must move away from strategies designed to expend new energy assets, relegating that option to the resource of last resort. We must learn to operate on what nature gives us for free and what can be recycled whenever possible. For these reasons, the routine application of high-performance design principles will not come as an evolution of existing HVAC design practices, but through a technological revolution in the way we design buildings.
Progress can only come one step at a time and will be built on past progress. Design firms that fail to make adequate progress will wither and die in the coming market. Those who do will survive and prosper. Furthermore, “faking it” will not be an option, and those currently engaging in the practice should expect litigation. Those who choose that path should expect to be held accountable.
1) Lentz, M.S. (2009, January). Regenerative Dual Duct: A case study. HPAC Engineering, pp. 20-26.
Mark S. Lentz, PE, is president of Lentz Engineering Associates and a member of HPAC Engineering’s Editorial Advisory Board. He has received numerous national engineering awards, including a Distinguished Service Award from the American Society of Heating, Refrigerating, and Air-Conditioning Engineers.