I was impressed by Henry Gifford’s presentation at the BSC Summer Camp this past summer (yes, the Henry Gifford who sued the USGBC). In it he lays out simple strategies for ensuring happy occupants (comfortable with their own thermal control) via low-maintenance HVAC systems that are energy efficient. He measures energy. He tracks energy use. It makes sense. He led the following chant to a room full of adoring building scientists: give me some H (H!), give me some V (V!), and give me some AC (AC!) – but don’t do HVAC to me! His point was that heating, ventilation and air-conditioning should be decoupled (context: Mr. Gifford owns multi-unit residential buildings in NYC). Integrated systems can lead to unnecessary complication, can be difficult to commission and therefore don’t work as intended and are rarely maintained as they should. Simpler systems work better because, well, they’re simple and can deliver results.

Shortly after meeting Mr. Gifford I met Jeffrey Inhnen of Michaels Energy. He presented at the ACEEE Summer Study where he also made the case for simpler HVAC systems. This is from his white paper:

Central air handling systems have evolved over a century starting when energy was very inexpensive.  As energy costs have risen, the central system has been modified into an overly complex variable air volume system that almost always permits excessive simultaneous heating and cooling, and fan and pumping energy.  In fact, in some applications “excessive” simultaneous heating and cooling cannot be avoided.

Wasted energy from simultaneous heating and cooling, pumping, and fan energy have been witnessed at many facilities investigated by Michaels Energy.  These include facilities that were built through the process of new construction programs and LEED®; facilities that use substantially more than median energy consumption reported by Building Energy Consumption Survey 2003.  Why?  Not because their energy models and design intents aren’t good necessarily, but because the systems are overly complex, poorly understood by key stakeholders, and rarely commissioned with functional testing of systems to ensure design intent integrity.

One way to avoid this inherent propensity for waste is to use dedicated outdoor air systems that decouple ventilation heating and cooling from zone heating and cooling needs.  This avoids the vast majority of potential simultaneous heating and cooling.  Compared to conventional HVAC (variable air volume) systems, these systems:

• Are no more complicated to design.
• Can be cost competitive with less ductwork, no variable air volume boxes, smaller fans, and less complex controls.
• Provide better comfort for occupants.
• Save energy and have a lower life cycle cost for owners presenting a competitive edge for contractors. (needs further study)

When it comes to technology, we need to keep the users in mind. We need to keep it simple. Do we really need those latest technologies in all cases? Do we need more complicated buildings?