This Old Library
Strategies for reducing energy consumption
Strategies for reducing energy consumption
Posted Wed, 03/02/2011 - 14:20
Tools of the library-sustainability trade
Sustainable building construction is the major issue facing the architectural profession in the United States and around the world. Consider the implications of ignoring it: Today, 300 million people living in the United States represent approximately 4.3% of the world’s population, which is now nearing 7 billion. All 300 million of us use 21% of the world’s energy resources every year. Of that 21%, approximately 43% is used to heat, cool, and construct buildings in this country. To continue with the math, the United States annually uses slightly more than 9% of the world’s energy for buildings.
As a nation and as architects, we are constantly developing ways to reduce energy consumption in the new buildings we design and construct. In fact, we are looking for ways to create new buildings that will be energy neutral—that is, they will produce as much energy as they consume. However, if we focus only on new buildings, we will not reduce our consumption; we will only increase it at a slower rate. Thus, the critical problem is to address the sustainable improvements we can make to existing buildings. (Sustainable buildings are designed to take maximum advantage of the natural setting and climate while causing the least possible damage to the environment. As a result, they are efficient in their consumption of energy.) We can reduce energy consumption in the building sector only by dramatically reducing the amount of energy consumed by all the buildings that currently exist.
One of the ironies of “green” or sustainable architecture is that each new green project is advertised as using dramatically less energy than a comparable building of the same size that meets all code requirements. No one ever asks about the intensity of the occupancy of the new building, the number of square feet per person in that new building, or whether the building was even necessary or appropriate. Often, institutions will construct new, energy-efficient buildings, but will continue to heat and cool the older buildings, which may be inefficient and perhaps superfluous. Conversely, choosing to transform an existing building into an energy-efficient, sustainable building would result in true savings in energy consumption.
Why are existing libraries good candidates for transformation to sustainable buildings? Libraries are important community centers visited every day by the public. Library buildings are usually well constructed and intended to have long lives. To preserve their contents, these buildings generally have a stable interior climate, which is compatible with most energy-saving strategies.
Simple sustainable improvements
If a community is contemplating how to transform an existing library building into a more sustainable facility, a number of standard techniques can be considered. Some of these improvements are easy to bring about:
- Most older mechanical systems are relatively inefficient. Replacing major equipment (such as boilers, compressors, and cooling towers) with new equipment can easily increase the energy efficiency of heating and air-conditioning systems by as much as 20%.
- Such improvements probably would be accompanied by a new building management system or new controls for the ventilation system. Since a typical library is unoccupied almost 100 hours a week, energy savings can mount up when the ventilation systems are turned off and heating and cooling setback temperatures are used regularly.
- Electric lighting in library buildings typically consumes about 27% of the energy budget. Older buildings frequently allow plenty of daylight to enter through large window openings; nevertheless, the electric lights are left on all day. Two basic strategies can combat this waste of energy: The first, of course, is to use the most efficient lighting systems; the second is to teach the library staff to switch on the electric lighting only when necessary or, alternatively, to install occupancy sensors and a lighting control system that automatically adjusts the amount of electric light to compensate for ambient daylight.
- Windows typically are early targets in energy conservation. Replacing single-glazed windows with double or triple glazing accounts for major savings and a quick payback. During the energy crisis of the 1970s and early 1980s, it was common practice for libraries and other civic buildings to replace single-glazed wood windows with double-glazed aluminum windows. However, the anticipated improvements were exaggerated because of the inherent flaws in most aluminum replacement windows, which allow excessive infiltration (air leakage into buildings) and conduction of heat out of buildings through the metal frames and sashes.
- Another simple energy improvement is to upgrade the insulation in the exterior skin of a building. The easiest place to make this change is on the roof, which is usually the largest single exterior surface. When the roof is replaced, the added insulation can make the area more resistant to the transfer of heat. Similarly, exterior walls can be improved if significant renovations are undertaken.
More complex sustainable improvements
More ambitious improvements or alterations can further reduce the energy consumption of an existing library building:
- The exterior walls of older libraries often are constructed of masonry with plaster interior surfaces. A significant reconstruction of the exterior walls could result in much greater resistance to heat transfer. For example, the plaster might be removed and insulation installed behind new interior gypsum-board surfaces. Alternatively, the exterior building envelope might be modified from the outside to dramatically increase the resistance of the exterior walls to energy transfer.
- Heat gain through windows may occur during the warm months, straining air-conditioning systems to maintain comfort. This problem can be remedied with appropriately located deciduous trees, exterior sunshade devices, coatings on the exterior glazing, and interior shades. Usually, some combination of these strategies will substantially reduce heat gain.
- With older library buildings often constructed of masonry, the buildings usually will have high thermal mass (the ability to absorb temperature fluctuations and maintain a stable temperature). Unfortunately, much of this mass can be exposed to harsh exterior weather conditions that prevent the building from stabilizing the interior climate. To rectify this situation, a significant part of the thermal mass can be made to function as part of the building’s interior. Strangely enough, the best strategy might be to cover the exterior masonry with insulation and a new skin against the weather so the masonry walls function as part of the more stable interior climate.
- A dramatic strategy for improving energy efficiency is to install geothermal heating and cooling. The simplest geothermal system, effective in temperate climates, is the closed-loop system, which requires wells drilled into rock. The stability of the ground temperature supplies the building with 55–60 degree fluid in the summer and 50–55 degree fluid in the winter. The heat pumps connected to these systems produce warm water or chilled water at much less cost than heating up air from possibly 15 degrees in the winter or cooling it down from possibly 95 degrees in the summer. Even though these systems are fueled by electricity, potentially they can save 40% of the energy of an up-to-date, energy-efficient, conventional mechanical system.
- Progress is constantly being made to improve the efficiency and reduce the cost of photovoltaic collectors, which generate electricity from the sun’s energy. If the existing library building has extensive areas of flat or south-facing roofs, photovoltaic panels might offer dramatic results.
- Similarly, the technology of windmills and wind turbines is improving rapidly. Many library buildings are situated on open sites that could easily accommodate windmills. In urban settings, wind turbines work well because they are smaller and less conspicuous. The addition of wind energy to the mix of energy sources may provide the opportunity to create an energy-neutral library.
Making library sites sustainable
Library buildings do not exist in isolation. Even in cities, libraries often are located on somewhat open sites, which present opportunities to create more sustainable landscapes that can also generate energy.
- Most current regulations require stormwater runoff to be retained on site. Even on existing sites, runoff usually can be filtered into the ground.
- Typical suburban libraries or academic libraries may have adjacent parking lots that can be resurfaced with more permeable materials to reduce runoff. In addition, the heat island effect of these surfaces can be mitigated with shade trees.
- In many parts of the country, the plantings and lawns surrounding the library require regular irrigation. This would be unnecessary with a switch to native, self-sustaining vegetation.
- The library site can be used to generate energy. The geothermal wells mentioned above typically are drilled into the library site, including paved areas and green space.
- Sunshine that falls on the library’s parking lot can be collected to generate electricity if the parking spaces are covered with trellises of photovoltaic panels. Using this technique, the vehicles parked on the lot are shaded, and the sun’s energy that once overheated them instead generates electricity to run the library building.
- Overall, the strategies for a sustainable site—especially those related to irrigation, plant material, and paving—could create a site that more resembles the natural condition before the site was developed.
Meeting sustainable objectives
Having reviewed strategies for improving library buildings and their sites, we might ask: What are the prospects for the future, and how can libraries plan for sustainability? Here are three increasingly ambitious sets of objectives:
- Reasonable objectives: Reducing energy consumption by 30%–50% is a reachable goal. This can be achieved by transforming the heating and cooling systems, taking advantage of daylighting coupled with electric lighting controls, changing or coating the existing glazing, and adding insulation where it can be installed most easily, probably in the roof.
- Ambitious objectives: Reducing energy consumption by approximately 70%–80% is more ambitious. This can be achieved by adopting all of the strategies mentioned above and, in addition, by adding more significant changes to the building envelope. These changes might include shading devices, increased insulation, and investment in site-generated energy such as wind power or photovoltaic panels.
- Zero-energy buildings and sites: The most ambitious objective is to create an energy-neutral library. All of the strategies described above must be employed. In addition, enough energy must be generated at the site and within the building to meet all the remaining energy needs. A likely solution would include geothermal heating and cooling with electricity generated from photovoltaic panels and wind energy. This objective is achievable and represents the idealized path to the future.
Libraries are solid buildings, constructed for the long term. They are constantly visited by the public and can set an important community example. Library facilities should be community leaders in sustainable practice. This revolutionary transformation can occur incrementally, with quantifiable results that provide an excellent return on the investment.
PETER GISOLFI is senior partner of Peter Gisolfi Associates, a firm of architects and landscape architects in Hastings-on-Hudson, New York, and New Haven, Connecticut. He is chairman of the Spitzer School of Architecture at the City College of New York and is the author of Finding the Place of Architecture in the Landscape. He can be reached at email@example.com/.