Green Design Economics - the Passive Bonus
Jun 6th, 2007 by urbane5
GREEN DESIGN ECONOMICS - THE PASSIVE BONUS
Free lunch, no such thing. Free energy - yes there is. And even the most ardent architectural technophiles should want it. The Sun - as solar heat, light and wind energy - is the ultimate environmental “freeware”. And we can harness it - without the expensive tackle usually associated with energy production. The key grips:
- positioning our buildings in strategic relation to the sun and wind
- incorporating passive thermal structural features
It really is that simple. Planetary physics + strategic architectural geometry = free energy.
COST OF CONSUMPTION - SAVING IT
Buildings are estimated to consume 39-48% of all energy used in the U.S. today. Electrical lighting and HVAC equipment used to condition indoor space account for more than half of this total. We can reduce this energy expense - and the associated depletion of resources - 50-75% using passive mechanical strategies. Imagine it - or better yet, let’s design to make it happen. Incorporating ”systemic” energy into our buildings can deliver dramatic returns: cut fossil fuels use by half, cut carbon release by half, cut the usual money spent by half. Now that’s comfort. The passive bonus is more like a bonanza.
PASSIVE STRATEGIES - THE SPECIFICS
Most of us are familiar with passive thermal strategies by other names: super-insulation, solar orientation, natural ventilation. Maybe information overload is what really comes to mind. But bear with me. Consider the following list of optimizing passive features for buildings in the northern hemisphere with “hot summer, cold winter” climates, such as we enjoy in Albuquerque, New Mexico:
- building shape and orientation optimized for most direct intersection with diurnal path
- year-round daylighting and winter solar heat premium within 15 degrees of south - low U-value, double or triple pane, low-e glazing in all windows and glass doors
- majority of window area on south and east walls
- maximum glass area 7-12% of building floor area - exterior and interior shading/insulating devices for all sunlit glass
- overhangs, deciduous shade trees, blinds, drapes - highly insulated, well-sealed building envelopes - R-30+ walls, R-50+ roofs, R-7+ foundations
- venting of interior at minimum 0.35 air changes per hour from outdoor source - interior thermal mass structures - concrete, earth, water, stone
- exposed to winter sunlight and open to cooler night air in summer via windows, doors, vents
- low gloss, medium dark colors for efficient solar absorption - fresh air inlets low on shaded exterior walls - via windows, doors, vents
- fresh air outlets - 50-100% larger than inlets for most efficient exhaust
- openings high on leeward (downwind) side of room, stairwell, or cooling tower - plantings for summertime shading of building and grounds
- native or acclimatized species for little or no need for irrigation - high reflectance roofing materials and exterior wall finishes
BUILDING NEW
Though most of us know about these “natural energy” strategies, we don’t live in buildings which employ them. Designing passive thermal geometries and materials into new construction is particularly simple and “cost neutral”. Selection of a designer whose esthetic and expertise extend to such whole-system planning is critical. Search for one through your local solar industry professionals directories, such as www.NMSEA.org here in New Mexico or your local chapter of the National Association of Home Builders. Any building style, traditional to ultra contemporary, can be designed to harvest the sun and wind.
REMODELING
If building a new home is not a current option,there is still good news: even when remodeling to incorporate passive energy features, the gains are immediate - and compound as fossil fuel costs rise. No energy source other than the sun is required to generate the light, heat, ventilation and cooling produced by passive thermal systems. And all the materials involved are conventional construction elements, though of higher performance grades for greatest benefit. If money matters, designing to harvest passive energy is in our interest.
BEYOND MONEY
For those fortunate enough not to be concerned about cost, there’s the other balance worth caring about: atmospheric carbon. Environmental benefit is a reason beyond economics to incorporate natural energy systems into our buildings. Passive energy systems are capable of reducing the fossil fuel heating and cooling energy load - the “carbon footprint” - of a median-sized home by as much 50%. And even greater “greenhouse gas credits” are realized if a solar water heating system is used for both space heating and domestic hot water. A home that optimizes the capture of natural energy sources is a gift to the future - to the next generation and beyond, our legacy as a society, and the ecology of the Earth itself. Green energy is an environmental form of the “common good”.
THE NET
Passive solar building strategies are cost-neutral mechanisms of free energy capture. It makes sense - and saves dollars - to connect our buildings to everything good about the sun - the wind, the trees - and even the cool of the night. All are passive solar benefits. And all are free. Life is good. Let’s design to enjoy it.
Copyright © Erica Enyart
About the Author:
Erica Enyart, CEO and general contractor of Entrada Builders Co. from 1977 to 2005 is now Director and senior designer of the UrbanEcos design group in Albuquerque, New Mexico - http://www.UrbanEcos.com. Contact for building design and sustainable technologies: enyart@urbanecos.com.
You have permission to publish this article electronically, in print, in your ebook or on your web site, free of charge, as long as the author bylines are included.
