Why Passive Performance?

The best energy management approach to homes and buildings is the one that results in the least energy consumption and the lowest numbers of special energy conversion equipment. This "passive building performance" approach typically results in the lowest long-term energy system and operation expenses and pollution. Don't confuse this passive design approach with ones that ignores site, construction and design issues, instead focusing just on efficiency prescriptions like R-values and improvements in HVAC, lights and equipment. Optimally, passive high performance comes first, such that R-values and equipment needs, from size to count, are minimized. This also makes those material and equipment first-costs lower.

Alternative energy opportunities like solar, wind, conservation and efficiency are usually cheap, renewable and plentiful. The easiest and least-cost approach to alternate energies prioritizes their passive use and minimizes energy demand before specifying active alternate energy conversion hardware, like active solar collectors, wind generators and batteries. In structures, passive alternate energy building features like south-facing glass, minimized exterior surface areas which are superinsulated and airtight, window layouts for natural ventilation, and optimized overhangs and building geometry are not only relatively easy, reliable, and less expensive than mechanical heating and ventilation strategies, but they are permanent, outlasting equipment. Conversely, not taking passive advantage of passive performance in a design results in:

much larger purchases of energy

much more reliance on energy conversion hardware like power generators, ACs and furnaces

much more pollution

much more repeating equipment expenses

Structures can be designed and built to minimize energy consumption before any energy conversion equipment like furnaces and solar panels are added. Occupants can also be taught to demand less energy to accomplish their desired or required tasks. I've documented this in home design as well as in solar electric system design. In building design, by selectively controlling the sizes, shapes and performance characteristics of exterior surfaces, as much as 50% to 75% of heating, cooling, ventilation and lighting energy needs can sometimes be eliminated. Similarly, teaching occupants to tolerate somewhat lower indoor temperatures and temperature swings inside their conditioned spaces during the heating season can permit more passive performance, as might be expected by intermittent solar heating. Also similar, by minimizing electrical loads and consumption inside our conditioned spaces, sometimes just by changing occupant energy preferences or upgrading efficiency factors, not only can we reduce the amount of heat that must be tolerated or offset by AC during cooling season, but also we substantially reduce needed AC and electrical generation capacity, solar or otherwise. In other words, achieving best passive high performance can mean both structural and ecological design considerations as well as occupant education and training.

Consider just the issue of passive high-performance heating in smaller Midwest USA structures like houses. Their insulation levels must be high and exposed exterior surface areas small. South-facing glass areas must be high enough and distributed properly, possibly relative to thermal storage masses. Non-south glass areas must be small. Unintended air leakage through exterior surfaces must be minimized. Solar glass area, thermal storage, summer shading and natural ventilation must be optimized relative to local climate and the building's expected occupancy patterns.   Indoor air quality is most easily and inexpensively improved by using fewer toxic (outgassing) and allergenic materials inside the living spaces. These are all first steps to designing and achieving thermally efficient, well daylit, less polluting structures with simpler energy supply decisions and better overall ecology. Demand for power and generation equipment on or offsite is minimized. Since energy needs are lower, the potential for achieving a greater fraction of required energy supply from onsite sources like solar is increased.

The most recognized example of design for passive high performance is "passive solar design". During a power outage or furnace breakdown in winter, a well-designed passive solar structure stays warm because of its passive ability to retain heat and collect solar energy. It stays cooler in summer even without air conditioning because of airtightness, shading, better glass orientation and less use of electric lamps during midday. There is a similar analogy for people interested in reliance on off-the-grid solar electricity. During cloudy Midwest USA winters, it's often lower electrical consumption which allows an off-grid solar electric supply to be sufficient rather than more solar power.   Having an off-grid solar-powered office, I state this from personal experience.

Contrast this with typical structures and power consumption habits. Our conventional buildings and homes are responsible for excessive energy use and pollution over their lifetimes because these kinds of choices and decisions are ignored or avoided during their design and construction. These structures can become rapidly unlivable during long power outages and furnace or air conditioner breakdowns. Our conventional energy-usage in residential as well as commercial buildings is typically always rising, demanding more and more energy for more tasks, constantly increasing reliance on electricity supplies.

If you're looking for optimized passive high performance from your next home or office, contact me. Not only do I have lots of experience with several specialty software tools for hour-by-hour thermal simulation and electrical load detailing, but I also have lots of experience educating and training clients to achieve these kinds of goals.

John F. Robbins, CEM CSDP

3519 Moffett Road

Morningview, KY 41063-8748

Phone: (859) 363-0376

E-mail: johnfrobbins@insightbb.com