I’ve attended technical presentations by William Lull before and came away having learned something I didn’t know about a familiar topic, so I was interested to see how this course would unfold. Mr. Lull opened the session by asking the attendees, a group with a wide degree of knowledge and experience, sitting around the conference table what they expected to get out of the session. Personally, I hoped to get a refresher on HVAC technology particularly any way the equipment could be used more efficiently while creating a preservation environment. Museum environmental standards have become a hot issue in the last year with several articles devoted to the topic. It has long been understood that maintaining the historical conservation set points takes intensive HVAC capabilities and in the current global economy is increasingly expensive. I think that makes the course poignant regardless of where the growing debate on museum environmental set points finally pins them.
A quick flip through the provided slide printout let me know that I would probably have my expectations met. It was full of technical diagrams, flow charts, and even a few equations (only a bit of algebra folks, nothing to freak out over). Mr. Lull started out emphasizing that the focus of the course would be about maximizing the efficiency of existing HVAC equipment not about building a system from scratch as a retrofit. I felt that this was a very smart and well conceived approach, particularly given the reality that few conservators working in existing institutions would have the opportunity to change to entirely new systems. Mr. Lull focused on one simple term to characterize why HVAC systems operate and use energy, they are responding to a LOAD (internal, envelope, or outside air) and the primary LOAD on the system is the expectation WE have for the environmental conditions of a space and the buildings capacity to retain those environmental conditions. I appreciated that Mr. Lull repeatedly drove the point home that a system’s energy use is directly related to LOAD demand which is directly related to OUR expectations. I should also point out that Mr. Lull changed his mind on actually making the class do calculations in favor of a more general and practical overview, a wise decision I think.
After a brief side discussion about the variability of energy production methods; steam vs. hydro vs. wind and the problems of energy storage we turned to how that energy is used. In order to have everyone on even footing Mr. Lull introduced the components of a modern HVAC system, what components used energy, what type of energy, and why they needed energy. He then launched into a more in-depth overview of the energy consuming components of HVAC. These components include; boilers, chillers, pumps, and fans. This review of the basics made his discussion of the work conducted to increase the energy efficiency of the system at the Harvard Depository easy to follow. Energy efficiency hinges on better use of certain components of the HVAC system and how Newtonian physics, an action and reaction systemic response of the system, governs the adjustable variables and their end effects.
The crux of increasing energy efficiency is actually better management of the systems response to human occupancy of a space and reducing all other unnecessary loads. Mr. Lull highlighted the often conflicting demands of museum HVAC for exothermic control from human occupancy and humidity control for object stability. One major aspect of dealing with human occupancy is CO2 mitigation in occupied space. The need for outside air that must be conditioned is directly related to diluting the CO2 generated by human respiration. The conditioning of outside air ends up being really expensive since it requires the use of the system energy hog, chillers. Chillers get rid of heat and humidity gobbling up lots of energy in the process.
The up side of HVAC energy use, the savings, is that it is possible to use existing equipment more efficiently. Mr. Lull indicated two areas of focus that allow for significant gains; using VFDs (Variable Frequency Drives) with fans and pumps and a time investment to program as many climactic variables and set points as possible into the HVAC control system. The use of VFDs allows for energy reduction by slowing fan and pump rotation without a loss of performance over time. Providing the HVAC control system a greater number of scenarios and set points allow it to respond in a more nuanced manner to both changes of inside and outside air rather then simply a full capacity response to all demands.
In short, the course was well worth the time and cost. The topic’s presentation was informative and relevant for conservators that find themselves in institutions where knowing how the HVAC system operates and the proper terminology will aid in clear communication with HVAC engineers equaling a higher success rate in creating a sustainable preservation environment. As a matter of fact you might want to send your HVAC engineer to the course. The only aspect I might change for a future workshop would be to give the topic more time with an extra half day or day to pick apart case studies.
The supplemental course folder provided; a complete PowerPoint slide list, enlarged diagrams, & resource sheet with helpful equations.