Two recently completed projects, as well as one currently under design, illustrate some of the challenges encountered and solutions developed when designing hvac systems for arts environments.

Reclaimed attic space was used to house exhaust fans and the AHUs at Fayerweather Hall on the campus of Amherst College. The space is used for both studio art pursuits and art history courses, and good IAQ is important to the health of the artists.

Teaching Environments

Amherst College

An initial challenge was where to locate the myriad of fans needed to meet all the exhaust requirements for the various studios. Ideally, these units are located outdoors on the roof, enabling the discharge to be directed up and away from the building. However, given the prominent location of the building and the roof profile, exposed equipment on the roof was unacceptable.

Therefore, looking under the roof, two new mechanical rooms were carved out of reclaimed attic space to house exhaust fans and makeup AHUs. But how to get the exhaust air out of the building and makeup air into the building in an aesthetically appropriate manner? Multiple exhaust stacks and intake hoods sticking up above the rooflines would ruin the roof profile and appearance of the building.

The solution involved using chimneys and dormers - elements sympathetic to the building's architecture. Existing chimneys, as well as new ones built to match them, were used to conceal vertical exhaust stacks. An additional chimney and a new dormer, built to match existing ones, served as ways to bring makeup air into the building.

Moving air from the attic mechanical rooms to the studios was another challenge. The original use of the building, which was for scientific purposes, helped because some existing vertical chases could be reused with rebuilding and enlarging. But the amount of ductwork that had to be installed far exceeded anything that had previously been used there. As a result, additional chases were created throughout the building.

The college wanted to retain Fayerweather Hall's existing large, wide-open studio spaces. Installing dropped ceilings in the studios would have dramatically altered the feeling of the studios. Instead, the ductwork and other utilities were exposed in the studios to retain a sense of openness. This required extensive coordination to ensure that the utilities were organized and routed in a visually pleasing manner.

In the interest of safety and responding to the college's construction budget, the exhaust and makeup air systems serving the studios are constant-volume systems. To control energy consumption, studio occupancy schedules are entered into the building's ddc system, which in turn controls the hvac systems.

Although an energy penalty is associated with a constant-volume system, the college feels that consistent air balances, airflows, and pressure relationships are a higher priority. Classrooms within the art history portion of the building are served by vav systems, while fancoil units serve faculty offices.

The protean environment at theTang Teaching Museum and Art Gallery on the campus of Skidmore College (Saratoga, NY) required precise control to preserve the rare art there. This was achieved through constant air circulation and good distribution.

Various Exhaust Systems

• Backdraft hoods in any location where aerosolized solvents are used or painting equipment is cleaned, at sinks in the photography studio, and in printmaking areas;
• Conventional lab fume hood for acid etching in printmaking;
• Snorkels for capturing contaminants at the source where welding and cutting take place;
• Dust collection system for woodworking and plaster clay mix areas;
• Commercial paint spray booth;
• Kiln exhaust hood; and
• Minimum air change rates in painting, printmaking, and photography to supplement localized exhaust in these areas were accomplished to provide dilution ventilation of contaminants released away from local exhaust.

Noise Attenuation

It becomes very difficult to balance all the performance requirements necessary to maintain the proper studio environment. Some remedial measures used to reduce objectionable noise were to make small reductions in air quantities exhausted through slot hoods, to enclose some slot hoods, to install isolating material between wall-mounted exhaust hoods and the wall, and to install duct sound attenuators.

Museum Environments

Generally, the environment in most art galleries and museums are geared to the viewing public. However in museums, compromises are necessary in order to balance the atmospheric elements needed to preserve artwork and maintain human comfort, and at the same time, be efficient enough to control initial expenses and operating costs.

Regardless of the exact temperature and rh criteria, one factor necessary for all museum environments is that conditions remain as stable as possible, 24 hours a day, year-round.

Of the two criteria, stable rh is more important. In most cases, fluctuations in temperature can be considered less critical than fluctuations in rh. This is a shift in thinking from most general comfort applications where temperature is the primary criterion. The environment must also be as cleansed of airborne contamination as possible, including both particulate and gaseous contaminants.

An artist's rendering of the future Katzen Art Center on the campus of American University (Washington). The building will house an academic wing that will include classrooms, art studios, and a photography lab; a performance arts wing, that will house a dance studio, recital hall, and theater; and an art gallery. Because of the mixed use, engineers were concerned with monitoring and controlling air temperature, rh levels, and outside air intake levels.

Skidmore College

A versatile environment is necessary for such a diverse permanent collection. However, the budget did not allow for, nor did it seem practical to install, individual discreet environments for each type of art.

After consultation, the museum director decided the indoor design criteria should have more moderate values of 70 degrees and 35% to 45% rh depending upon the season. The director further stipulated that daily temperature variations (within a 24-hr period) could not exceed plus or minus 2 degrees, and daily rh variations could not exceed plus or minus 2% degrees. The changeover between summer and winter rh values was to occur gradually over a three- to four-week period.

To preserve a collection, the proper museum environment for artwork is more likely to consume energy rather than to conserve energy. Most conservation strategies, including airside economizers, night setback/setup, and demand limiting may conserve energy but do so at the expense of the collection.

The two guiding principles in the hvac system selection and design at Tang were to preserve the artwork regardless of whether it was in storage, on display, or in the preservation-restoration area, and to satisfy the indoor design criteria at all times. Because the indoor environment is so crucial, airflow must clean the environment, maintain rh, and control temperature.

Constant air circulation with good distribution throughout the spaces is the way to ensure this. After taking into account space functions, adjacencies, building shape and orientation, and system capabilities, vav systems were ruled out. It was concluded that a multizone reheat system was the best way to satisfy all these demands on the hvac system.

Central station AHUs are located in mechanical rooms strategically placed and sized to contain all reheat coils and piping within the mechanical rooms. The number and location of mechanical rooms directly correlate to the locations of the two main galleries as well and to the unique shape of the building (it is a star-shaped building with no 90-degree angles, with the interior being a lofty, open space).

To avoid damage from possible leaks, all overhead water or steam piping was prohibited from spaces that contained artwork. AHUs were double-wall constructed to completely enclose the units' insulation to ensure that no fibers or particles could enter the airstream and be deposited on the artwork.

AHUs were also equipped with prefilters and high-efficiency final filters for particulate contaminants. Given the college's rural setting, gaseous contaminants were not a concern. However, future carbon filtration capability was provided by installing the filter section within the AHU. Filter trays were not installed but can be added at any point if gaseous contaminants do pose a risk in the future. Carbon is a good general adsorbent of gaseous contaminants and other chemicals can be added to address specific gaseous contaminants.

To provide the museum with a year-round stable environment as required by the indoor design criteria, a cooling source must be available on demand, and a heating source must be available year-round. The college has an on-campus chilled water system and a campus medium-temperature hot water system, but only the hot water system is available year-round. Therefore, a dedicated chiller was installed to meet the museum's cooling requirements, and sized to handle the full design cooling load of the building.

Tying into the campus chilled water system and using it whenever it was available was considered because this would allow downsizing the chiller to handle only the expected cooling demands for those times when the campus chilled water system was not available. This turned out to be more expensive than the larger chiller and therefore was not implemented. Budget limitations also did not allow for the installation of any backup cooling equipment.

Humidification

A clean steam generator using the on-campus medium-temperature hot water system and potable water provides humidification. Other humidification methods involving direct injection of water to the airstream, such as sprays, atomizers, fog, and ultrasonic, were not considered. These systems may introduce higher amounts of contaminants contained in the water into the environment than systems utilizing clean water boiled to vapor.

Humidifying the entire building created additional design challenges. Humidification requirements impose a performance criterion on the building's envelope that is not found in general comfort environments.

Walls, roofs, and floors must include a vapor barrier, and door and window frames must be thermally broken to avoid condensation forming within or on these components. The responsibility for minimizing vapor formation belongs with the architect, but the understanding of how and why this occurs rests with the engineer.

Thermally broken window and door frames worked successfully to eliminate condensation in all locations. Yet, even after much communication between the engineer and architect concerning thermal isolation, there were a few locations that were missed and found only after the building was completed and condensation had formed on them. These were addressed as they were detected. This emphasized just how diligent an effort is needed to ensure all potential paths of heat transfer are understood so that condensation is avoided.

The Tang Museum's exterior contained large expanses of glass that also posed a condensation concern. The potential for condensation on windows in this climate with an outdoor winter design condition of -7 degrees is very high, even with double glazing.

To eliminate condensation, fin tube radiation was located at the base of all these exterior glass areas, many of which went from floor to ceiling, leaving no space for wall-mounted radiation. Floor-mounted, pedestal-type radiation was unacceptable to the architect for aesthetic reasons.

As a result, fin radiation was located below the floor within trenches at the base of the glass. This proved to be a successful method of eliminating condensation.

The main gallery, which is the larger of two in the building, is the one that will typically display featured artwork. This gallery is a large, wide-open space with a soaring ceiling that starts at 13 ft at one end of the room and ascends to 33 ft at the other. The gallery has three exterior walls and a roof exposure; therefore conditioning the room from the overhead air supply would be fine during the cooling season but heating the room from overhead would not result in comfortable conditions at the floor level. This space could be likened to heating a gymnasium.

A radiant floor system was installed to supplement the overhead air supply in the main gallery. Because of the tight temperature tolerances, the radiant floor could not be relied on to meet the entire heating load.

Doing so could risk having space temperatures go out of tolerance during changeover from heating to cooling seasons because of the thermal mass of the floor and the inherent time delay associated with cooling down the floor mass. Therefore, the floor slab is kept at 70 degrees to 72 degrees, meeting indoor design criteria.

All hvac systems, including the chilled water and heating hot water systems that serve the gallery spaces, are on emergency power to again ensure as stable an indoor environment as possible, even during power interruptions.

Combination Teaching and Museum Environments

The Katzen Art Center is a 324,000-sq-ft school of arts building at American University (Washington). Currently under design, the building will be located in a highly visible and prominent location approximately two miles from the Vice President's official residence at the Naval Observatory, and Embassy Row on Massachusetts Avenue.

The building program identified three separate areas that had distinct functional requirements. These include an academic wing, a performance arts wing, and an art gallery. The following goals and design objectives were identified: design a highly energy-efficient building that exceeds recommended IAQ standards, achieves sustainable design criteria with state-of-the-art system controls, and provides flexible system operations.

Academic and Performance Wings

The primary engineering concerns were IAQ and energy efficiency as, in some of these areas, artists are using material with volatile and odorous gases. By using space air pressure differential and outside air dilution and exhaust, we are able to contain gaseous odors from spreading to other areas in the building.

Since the building requires a large volume of outside air, the use of heat recovery systems between outside air intake and the exhaust air were a very cost-effective option. Also by using state-of-the-art ddc, we are able to achieve the desired environmental requirements of the different spaces.

The performance wing includes a dance studio, 210-seat recital hall, 150-seat black box theater, and backstage areas. In the hall and theater, the primary concerns are strict acoustical requirements (NC 25), IAQ, and space load fluctuation. By working closely with an acoustical consultant, the desired design objectives were achieved.

Despite wide load (numbers of users) fluctuations, varied comfort levels were achieved in each area by monitoring and controlling air temperature, humidity levels, and the amount of outside air entering the space.

Gallery Space

Additionally, due to the building's urban setting, excessive gaseous pollutants could cause deterioration and degradation of the art collection. This is due to the acidic and oxidizing characteristic of the contaminants including ozone, sulfur dioxide, UV exposure, and nitrogen dioxide, which cause chemical reaction with metal and organic materials such as oil paintings, paper, canvas, etc.

Control of these pollutants is very critical in the conservation of this rare-art collection. The use of a combination of activated carbon and activated alumina will neutralize most of the dissolved gases in the air.

Several types of humidification systems were evaluated and it was decided to use an atomizing-type humidifier with RO water purification system to collect most of the dissolved solids in the water to improve required IAQ requirements for the space and reduce maintenance.

The solution uses the most advanced technology, reduces building energy usage, and protects IAQ. The net outcome will be a new generation of art school facilities that will be efficient, comfortable, and simpler to operate and maintain, while meeting specific enduser needs.

Maintaining indoor environmental conditions is one of the most serious issues facing engineers designing hvac systems in today's art-focused buildings. The greatest adversary of artwork is changing environmental conditions, such as fluctuating temperatures, poor air quality, and inconsistent humidity levels. Designing the most conducive environment for humans and artwork requires as much ingenuity as the creation of the artwork itself. ES