For background details regarding this teleconference, and access to other segments, click here.

Presenters: Joshua Gassman and Jim Nicolow, Lord Aeck & Sargent


click to enlarge

Site design concept. Images courtesy of Lord, Aeck & Sargent
Gassman: Lord, Aeck & Sargent is designing a net zero energy Marine Research and Education Center (MREC) at the Salt River Bay National Historic Park and Ecological Preserve on the island of St. Croix. The MREC will support the mission of the National Park Service and its partner the Joint Institute for Caribbean Marine Studies, a consortium of four research universities with marine-focused programs, to study the park’s resources and educate the public about the region’s marine ecosystems.

The 60,000-ft2 project will include marine research labs and support spaces, which represent approximately one-quarter of the program, plus interpretive and educational functions, administrative offices, and accommodations for visiting students and researchers. It is envisioned to serve as a demonstration of regionally appropriate sustainable design and construction.

As one of the U.S. Virgin Islands, St. Croix is located at about 17.5 north latitude and as such has a tropical climate. The master planning phase began with analysis of the local climate as well as the local environmental challenges. Surprisingly, air quality was one of the environmental challenges ranked highest by island residents. St. Croix is home to one of the world's largest oil refineries, and the island also burns oil to generate electricity.

Sewage discharge is another critical local issue. Several highly publicized discharges from the municipal system have caused fish kills and beach closures, and most residences rely on septic systems, many of which are failing and pose a risk to the sensitive reefs that are immediately offshore. Erosion and sedimentation are also significant issues on St. Croix, and water supplies are extremely limited. The Virgin Islands have no permanent bodies of fresh water, so all the water that is consumed on the island must be either desalinized ocean water or collected rainwater.

Finally, the municipal electricity supply is not only dirty, but unreliable and plagued by frequent outages. This is a serious challenge for a lab, which requires a continuous and reliable source of power to support sensitive research.


click to enlarge

Laboratory mechanical system schematic diagram. Image courtesy of Integral Group

The local climate has a relatively constant temperature through both the annual and diurnal cycles consistent with a tropical location. The high humidity is a challenge along with solar shading to control building solar loads.

Based upon the local environmental challenges, the local climatic conditions, and the program requirements of the MREC, the following key regionally-appropriate sustainable design strategies were identified:

  • Passive solar cooling load avoidance.
  • Natural ventilation/multiple conditioning zones.
  • Natural daylighting.
  • On-site water collection and storage.
  • On-site renewable energy generation and storage.
  • Solar hot water.
  • On-site wastewater and stormwater treatment.
  • Use of historic vernacular design solutions (such as breaking up the building volumes to increase opportunities for natural ventilation; the use of open porches, screened areas and courtyards; the use of deep overhangs and colonnades; and hurricane control that can also become solar control).

In evaluating the planned marine research activities and developing the initial program, the team concluded that the program wouldn’t necessarily require traditional laboratory environments.

For example, working with the researchers, the architects learned that single-pass air was not required. Taken in conjunction with traditional building precedents in St. Croix and a local culture where natural ventilation dominates, reducing the amount of conventionally conditioned space required offered a significant opportunity to reduce the facility's energy usage.

Three distinct "project conditioning zones" were developed. Zone M, which stands for "museum," requires tight temperature and humidity controls but represents only a very small percentage of the overall project. It is dedicated to museum collections and archival object storage. A vast majority of the project is in the other two conditioning zones, Zone A and Zone C.

Zone A represents the labs and some support spaces. It is the next most stringent zone and relies on the adaptive comfort model, allowing temperature to reach ambient on the low side and to go as high as 80 F as an upper limit, while keeping humidity to a maximum of 60%. This is a marine lab and there will be saltwater tanks in portions of the labs, so the humidity control becomes important both due to the outside conditions as well as the humidity introduced within the lab.


click to enlarge

Desiccant wheel dehumidification air handler schematic. Image courtesy of Integral Group

Finally, Zone C, which represents the majority of the project square footage, will be fully passively conditioned, with shading and screening, and supplemented with solar chimneys and/or ceiling fans as needed.

These tiered project conditioning zones dramatically reduce the project energy requirements and costs and are an important initial strategy in the pursuit of net zero energy.

Nicolow: The project will pursue LEED-Platinum and a minimum of three Petals under the Living Building Challenge, with a stretch goal of full Living Building Challenge certification.

The Living Building Challenge includes not only net zero energy, but also net zero water. The team found that these absolute requirements provided a certain clarity to the design process: the project must make do with the rainfall that falls on the site and treat all wastewater on site. It changed the discussion from the typical LEED project, where at the discussion is often about a percentage reduction below conventional practice. Instead, 100% of water use must be collected from rain water and 100% of wastewater must be treated on site, thereby protecting the fragile marine ecosystems which are the focus of the research.

Moving on to the mechanical systems, this diagram illustrates the proposed mechanical system for the labs.


click to enlarge

Conceptual master plan.

There are four major strategies employed to reduce energy use. The first is the use of the project conditioning zones previously described.

By passively conditioning a majority of the spaces, a large portion of the energy demand is eliminated, and tighter control is required only for the museum space and the laboratory spaces. The museum storage space is very small and will use a conventional mechanical system to maintain tight humidity and temperature controls.

For the laboratory, the primary driver is humidity. One of the key strategies is using the building itself as a duct. The site has strong prevailing easterly winds much of the year, so the goal is to design the building to channel the prevailing winds to assist the fans and reduce fan power requirements, with the fans ramping up dynamically as needed when the wind alone is not sufficient to achieve the required air flow.

The humidity control and temperature control are decoupled and treated independently. Integral Group, the project’s mechanical engineer, has proposed a system which utilizes evacuated solar tubes to recharge a desiccant wheel that dehumidifies the incoming air stream. So dehumidification is provided without conventional compressors, instead harnessing the abundant solar resource. Radiant cooling is then provided from the slab to control temperature. The labs will also have a chilled water loop utility that will allow for spot cooling at the site of any unanticipated high research equipment loads, via portable plug-and-play water-to-water heat pumps.

Gassman: Because this is a marine research lab, one of the project's central utilities is a seawater system. Water is being drawn from out in the bay and then circulated through the lab. By using that seawater system not only to support the research, but to reject heat from the slab, the building will take advantage of the system that's already in the research program to provide an additional cooling benefit.

Nicolow: The seawater system also becomes an open loop ground source system for the research which allows for the rejection of heat to the returning stream for cooling.


click to enlarge

Site concept sections.

Returning to the dehumidification system, there is also a thermal storage tank for nighttime recharge of the desiccant dehumidification system, which will store daytime solar energy in order to provide dehumidification around the clock. This detail of the enthalpy wheel system illustrates that it is designed as a reverse energy recovery system: The system uses ambient hot air to recharge the desiccant.

The MREC has several non-traditional energy loads, including a SCUBA air compressor which has a fairly large demand, electric vehicle recharging, the pumping energy required for the seawater system, and the lab equipment loads. Based upon the preliminary analysis, it is anticipated that about half of the load will come from the laboratory equipment, so controlling plug loads is a key driver on this net zero energy project.

Based on the initial equipment lists, a lab equipment load of approximately 1.5W/ft2 was estimated. In true engineering fashion, that estimate was doubled and a safety factor added to arrive at 3.5W/ft2 for the equipment loads in the preliminary analysis; still well below the rule-of-thumb of 10W/ft2 often encountered in laboratory design.

An annual demand of about 767,000 kWh, was projected which can be met with approximately 30,000 ft2 of photovoltaic panels, representing about half of the roof area. With municipal electricity on the island almost $0.50/kWh, the payback is dramatically different than what might be seen in the Southeast United States, where electricity is as low as $0.07/kWh. The high conventional energy costs result in a rapid payback for solar power in addition to the added benefit of a more reliable power supply than the municipal system.

Gassman: The buildings will be sited to take advantage of the positive climatic attributes discussed. Solar orientation is designed to allow for proper passive solar shading and to ensure the thermal comfort of occupants. Orientation is also important to allow even daylighting of spaces while avoiding glare. Since the domestic hot water and on-site power generation systems are solar-based, their orientation and location must also be integrated in the final design solution.

The project massing will allow for cross ventilation from the easterly winds. One of the siting challenges is that the optimal orientation for solar and wind are contradictory; however, it was determined that the solar issue should take precedence in the site design, as other architectural design options are available to channel the prevailing winds and natural ventilation. These opportunities include solar chimneys to take advantage of stack effects, proper cross ventilation to draw air across spaces, and wind catchers to help direct the wind and open pavilions.

The buildings will be sited to take advantage of the topography as well. Building on the more moderate sloping portions of the site allows for views as buildings step gradually up the hill. In addition, the selected locations for most of the facilities will allow for foundation cisterns. This is the traditional location for rain water storage in St. Croix due to its steep terrain and severe fresh water shortages. Keeping with this tradition allows the cisterns to be constructed first so they can collect water during the balance of the construction phase so that, upon completion, the cisterns will be full.

Phil Wirdzek, I2SL/Labs21: I would like to share with the group that this project is also being used as the subject of an international student design competition, being run by I2SL in conjunction with the Department of Interior, the National Park Services, and four university partners. The competition is being promoted through the Association of Collegiate Schools of Architecture. If anyone is interested in that program, feel free to give me a call or check the Website.