A Sustainable Design

The design is a very green, low-carbon building, with an array of active and passive strategies that will allow it to meet the 2010 milestone of the AIA 2030 challenge. This means that it initially must reduce fossil fuel consumption and greenhouse gas (GHG) production to less than 50% of the average building of the same type in this climate (based on 2003 data). We will achieve this benchmark if we can include the 20 kW photovoltaic system. And if we continue to reduce energy consumption 10% every five years, the building will be carbon-neutral by 2030, which meets the AIA 2030 challenge. We feel this standard, which is focused on reducing energy consumption and the carbon footprint to address global warming, is the most appropriate one for this project. We also respect LEED and will track the design against it, but without applying for official certification. (The leadership of the university and college feel that it is more responsible to spend the estimated $100K cost of LEED certification on actually saving energy, i.e. investing the money in the building’s energy efficiency per se, rather than in third party approval.)

As designed, the addition is over 60% more energy efficient than the existing Art and Architecture Building (which we eventually hope to retrofit). How will it achieve this level of performance? It’s a combination of passive architectural strategies that enhance performance. First, the addition is stretched out on the east-west axis, making for a long south façade to collect solar energy. The large south wall is entirely glazed to collect solar energy in winter when the sun is low in the sky. This solar energy not only heats the space and occupants, but some of it is absorbed, stored by the dark-colored concrete floor and re-radiated after the sun sets. In the summer, when the sun is high in the sky, most of the sun’s rays are reflected off the glass. And the exterior movable shades are automatically lowered and their blades tilted to block solar gain when it is unwanted. (The key to this strategy is that over the course of the Ann Arbor heating season, a square foot of south-facing insulated glass gains more heat than it loses. Accordingly, the more south-facing glass the better.)

The narrow cross-section of the addition also enhances natural cross ventilation, with giant rolling doors that open on the south and clerestory windows that open on the north. And skylighting provides 100% daylighting during the day. In short, the plan and section, as well as the orientation of the addition, are ideal. Other energy-saving strategies include triple-glazing on the north façade, highly efficient boilers, solar pre-heating of HVAC make-up air, and heavy insulation of the envelope.

Building Addition Energy Conservation

Energy Conservation Measures	Energy Savings	Payback	Included?
Condensing Boiler	7.5%	4.5	Yes
Improved Envelope Insulation	8.8%	10.8	Yes
Triple Glazing North Windows	6.4%	13.2	Yes
Exterior Shading	2.7%	0	Yes
Ground Source Heat Pump	27.1%	41.9	No
Transpired Air Collector	13.6%	5	Yes

The chart above lists the six major energy conservation measures and their cost-effectiveness. Without the photovoltaics, they add up to a 58% improvement over the existing building. Fortunately, there’s plenty of available roof area, much of it at the ideal orientation and slope, for enough PV panels to eventually meet the AIA 2030 challenge of 100% efficiency and carbon neutrality for the addition. And, as PVs drop in price and rise in efficiency, it becomes more economically feasible.