Despite every effort at proper siting, layout, and planning, modern libraries are highly dependent on engineered mechanical, electrical, plumbing, water, and telecommunications systems. These systems account for up to 50 percent of the cost of construction of a library and also for a large portion of ongoing main- tenance costs and user complaints.
Over the last century, engineered systems have gone from relatively simple heating systems, with some mechanical ventilation and a small amount of elec- tric incandescent light, to complex systems creating a totally controlled envi- ronment. One of the greatest potential benefits of a sustainable approach to
library design is lessened dependence on these systems and their high-energy, high-cost strictures. The sustainable building interacts in concert with the cli- mate. To achieve this end, it may be necessary to relax temperature and humid- ity restrictions that are written into building programs. In the case of one recently completed main library, the relative humidity range allowed was so re- strictive that both the heating and cooling systems were required to run year- round to achieve the required humidity levels. Restrictive lighting requirements significantly drive up both construction and operating costs. Recommended illu- mination levels in libraries have increased significantly over the last 75 years. Although adequate levels of temperature, humidity, and lighting control must be maintained, thoughtful consideration should be given to what is truly needed and what it will ultimately cost to maintain the systems in a regime of high en- ergy and associated costs.
Lighting
Proper lighting is crucial for libraries. Lighting design begins with an under- standing that different uses in a building have different lighting needs. Stack lights, lighting for book reading, lighting for computer use, auditorium lights, and task lighting for work areas all have unique characteristics and requirements. There is nothing more pleasant than daylight for reading and writing; the glare of direct sunlight can present problems for computer users, however, and unfiltered sunlight can be detrimental to paper collections. High-efficiency T-5 or T-8 fluo- rescent lights represent the most efficient appropriate fixtures for libraries. High- intensity-discharge lamps, which are sometimes specified as energy-efficient, are inappropriate for library use due to the harsh and unwelcoming quality of light they provide. Indirect sources of light, which provide ceilings and walls with an even level of illumination, can be very effective in large open areas. Low-level task lighting, such as traditional reading lamps, is most appropriate for work and reading areas, as well as in creating a warm and inviting sense of place.
Lighting controls can help to make systems more efficient. Light control by photoelectric sensors causes the artificial lighting to automatically switch off when the light level from natural daylight is above a specified threshold. Sensors can also be integrated with dimmers so that there is a smooth gradation between natu- ral daylight and artificial light. Lighting should be controlled to automatically shut off at times when the library is not occupied, except as required for safety.
Energy Use and HVAC Systems
There are three main ways to increase the energy efficiency of a library. The first method is to decrease the demand for energy, the second is to meet the de- mand with energy sources available on-site, and the third is to improve the effi- ciency of systems requiring external inputs of fuel. Careful consideration of lighting requirements, temperature, and humidity ranges in the building can lower energy use. Proper orientation of the building and use of light courts and
other methods that reduce the amount of artificial lighting will result in de- creased energy use, as will the damping of temperature swings by using the ther- mal mass of construction materials. Geothermal exchange and precooling of intake ventilation take advantage of the fact that the earth’s temperature re- mains constant, by using it to heat or cool the water that circulates through me- chanical systems. Solar and wind energy, used either to generate electricity or to heat air and water, can reduce energy requirements. Wind can also be used to naturally ventilate libraries. In hot, arid climates, desiccant cooling occurs when hot intake air is sprayed with a fine water mist, which in turn is used to cool and humidify interior spaces. Mechanical systems are incrementally being improved to create higher resource efficiencies; high-performance motors, fans, and heat exchangers should be specified. Control systems that monitor temperature and humidity at many points in the building, coupled with variable-speed fans and remotely adjustable volume dampers, vary the output of the air-conditioning system to meet user requirements while minimizing energy consumption.
Many office buildings have recently been built with under-floor mechanical distribution rather than the more standard distribution in a ceiling plenum. The advantage of this approach is that air travels at slower speed through the system, and large fans are not required to blow cool air down from the ceiling. The cool air is distributed at floor level, where people are working, then slowly rises as it warms in the space. In an office environment, the raised floor offers flexibility, be- cause under-floor utilities can be reconfigured should the interior layout change. One concern in adapting this system to libraries is the weight of library shelving above raised floors; the system has been used successfully at the Vancouver Public Library, however. Low-velocity air systems reduce frictional drag on air moving through the duct wall, as does the use of spiral or cylindrical ductwork.
Proper testing and balancing of systems is of crucial importance, because me- chanical systems often do not perform correctly when first installed. One method now acquiring wide support is the hiring of an independent commis- sioning agent. The commissioning agent may be hired during the design phase to check the engineers’ performance, criteria, and design methods. The agent is then retained to rigorously test the mechanical system installed by the contrac- tor to verify that it satisfies the design criteria. These reviews are more thorough than those that have traditionally been provided by design engineers, who check the work for general conformance to the design intent.
Training of the owner’s staff in the use of the mechanical equipment is also crucial, as is the provision of a full set of maintenance manuals and warranties. The owner’s representatives should be involved throughout the design and con- struction of the project.
Water Conservation
Water use is an increasing concern in libraries and other buildings. Polluted runoff into storm-water systems and eventually into watersheds is regulated in many areas. Plants and a reduction in the quantity of nonpermeable surfaces re-
duce runoff, as does the construction of artificial wetlands, which use biological methods to purify groundwater. Rainwater can be harvested in cisterns for a va- riety of nonpotable uses, as can recycled groundwater. The use of sprinklers to ir- rigate library sites is unsustainable and should be discouraged or replaced by drip irrigation. In dry areas, drought-tolerant plants should be specified.
Inside the library, low-flow toilet fixtures should be specified. Some builders have gone further, specifying composting toilets, which significantly lower both wa- ter use and wastewater treatment requirements. Localized wastewater treatment, either through constructed wetlands or other methods, should be investigated.