Re-Making History

Peabody Mansion, in Chicago’s west suburbs, can accurately be described as an atypical single-family suburban domicile. This sprawling 30,000-sq.-ft. former residence on 90 acres was designed in the early 20th century by renowned architect Benjamin H. Marshall as a testimonial to the power of energy. It’s opulence was indeed bought with the wealth accrued by its original owner, Francis S. Peabody, who made his fortune in the coal industry—the once dominant heating fuel source in this country.

However, as times change, so do energy sources, as the mansion’s current owner—the DuPage County Forest Preserve District—found out. The local government agency acquired the mansion in the mid-1990s, along with a 65,000-sq.-ft. retreat building which was added in the 1950s, when it was taken over by the Franciscan religious order. The Forest Preserve District eventually decided to completely restore the buildings on the estate, which meant all new HVAC, life-safety, electrical and fire-protection systems.

With its Marshall pedigree, however, the mansion earned a spot on the National Historic Register, meaning systems retrofits would be much more challenging than first appeared, especially since the Forest Preserve District desired to essentially make the home a museum, preserving its heritage for another generation.

At the end of the day hard work paid off, as this 80-plus-year-old building runs with an energy operating cost equivalent to that of a new, well-insulated building. So much so that the engineering team was awarded a first place distinction from the Illinois ASHRAE chapter for excellence in engineering, and a second place award in ASHRAE’s regional finals.

From the beginning…

The HVAC scheme for the historic Francis S. Peabody mansion in Hinsdale, Ill., was driven in large part by the decision of its owner, the DuPage County Forest Preserve District, to operate the former residence for tours and high-occupancy meetings. In other words, both residential and multi-purpose occupancy requirements would have to be satisfied, as the proposed usage bridged two code ventilation design requirements. The new HVAC system would require a sufficient amount of outdoor air for every multi-purpose room. However, with primarily 8-in. ceiling spaces, duct space in the existing structure was at a premium. Further, the interior appearance of the mansion could not be changed and mechanical designers also had to deal with the challenge of working around newly installed sprinkler systems extruding from the low ceilings.

With all these limitations, low-velocity, constant-volume and variable-air-volume systems with perimeter baseboard heat were not viable options. Keep in mind the mansion originally had no air conditioning and its heating system consisted of a low-pressure steam boiler with cast-iron radiators located in highly decorative wood window enclosures throughout the perimeter of the residence. Unfortunately, the existing steam piping and equipment had asbestos insulation that was buried in the walls and exposed on the equipment.

The asbestos had to be removed, but the good news was that the existing routing from the old steam piping could be used for a new system. Additional routing was also implemented, but in a way as not to alter the appearance of the structure. Designers also made efforts to discretely hide new heating/cooling equipment within the historic enclosures.

Preservation pointers

The existing enclosures were carefully taken apart, digitally photographed, recorded and reassembled after all of the piping and ductwork was installed and operating. The engineering team then recommended a central two-pipe heating/cooling fan-coil system with a minimum code supply air-handling unit (AHU) for each of the two buildings. This system approach was chosen as it would minimize ductwork in both buildings and provide excellent energy operating advantages.

The new fan-coil system was installed with a built-in direct-digital-control board. Consequently, the computerized fan coil is controlled by a DDC room sensor integrated into the main building automation system for temperature monitoring, maintenance and control. The sensor varies fan speed, even shutting it off to maintain room temperature. This should result in considerable electric fan power and gas energy savings for both boilers and chillers.

Altogether, 45 DDC fan-coil units were installed throughout the mansion. This, of course, allowed for room temperature control and a way to provide readout, filter maintenance and a drain pan overflow alarm.

For the adjacent retreat building, which is presently designed only for freeze protection and minimum heating, 60 DDC fan-coil units were connected to the network with the same operating and maintenance monitoring capabilities. The retreat building is slated to be fully developed into a multi-use and office facility in the project’s second phase (see sidebar “On the Boards,” opposite page).

Every room in the mansion has a thermostat to control the fan coils in the summer and winter months. The DDC room thermostats themselves all run from a network control loop either in the basement or attic, and are fed, as required, through existing walls.

Not every space, however, could employ the “radiator replacement” scheme. In some of the second-floor bedrooms, for example, vertical-type fan-coil units were used, as they could be concealed in closets adjacent to the room. But some of the disconnected steam radiators were kept in place for visual effect.

Bathrooms also proved tricky, requiring yet another alternative plan. Because these rooms were difficult to access with new piping, the team, instead, decided to use small electric heaters with built-in thermostats. These units were then concealed within existing enclosures already under the windows.

Once again, the plan allowed for the reuse of existing enclosures, but also with modification for easy removal for maintenance.

Lastly, the mansion’s multi-purpose rooms also required a slightly different HVAC system. Instead of the predominant unit, these areas feature suspended DDC fan coils with an outdoor air intake duct connected to the return side of the unit.

As for the major HVAC equipment, two gas-fired atmospheric hot-water boilers were installed in the basement and an 80-ton chiller was located on grade adjacent to the residence. The chiller has a separate pump, while a remote panel, located in the boiler room, generates data on chiller operation and status. The main fan-coil pump—also located in the basement—circulates a glycol and water solution for both heating and chilled water to the fan-coil units and the AHU. An additional benefit of the glycol solution is that it prevents freezing in the fan coils and provides protection for the chiller, which is more damage-prone due to its outdoor location.

The retreat building, on the other hand, has two gas-fired hot water boilers with a primary-secondary pumping system between the boilers and chillers. The control system is located in its boiler room but controls all of the equipment within and in the historic residence.

Structural bear

On a final note, duct and pipe penetrations proved a barrier. In many historic restorations, gentility is the key, and the team was certainly sensitive to the historic finishes. Yet it had a real fight on its hands when it came to duct and pipe penetrations, as structurally, the residence was built like a fort with 12-in. thick concrete floors.

This meant structural modification to accommodate the new mechanical and electrical infrastructure. Thus, the existing plastered and cemented walls were opened to remove the asbestos-laden steam piping, and the opened walls were then used for new piping. It was then plastered to match the existing finish. Electrical distribution ran from sources in the attic and the basement.

Ready for another century

At present, the new HVAC systems have been operating successfully and providing comfort to tourists. The revived residence also regularly hosts a number of private events, accommodating several hundred people per occasion, giving new life and purpose to Marshall’s gem, while providing the county’s citizens with a great place to meet, entertain or just be.

On the Boards

The restoration of the heating and cooling system in the mansion is really just the start of the project. Its owner, DuPage County, has plans to further renovate the estate’s adjacent retreat building. On the boards is the conversion of a 5,000-sq.-ft. chapel into a 350-seat fine arts theater. The space, which features large stained-glass windows and a 35-ft.-high ceiling, will also serve as a reception hall.

Elsewhere, 5,000 sq. ft. will be remodeled into a multi-purpose room for lectures, banquets and other activities. A separate air-handling unit with filters, coils and ductwork will be provided for each space.

Currently, the retreat building is heated with two gas-fired hot water boilers installed in the first phase of the project. There are also two new pipe VAV direct-digital-control fan coils located around the building periphery. The second phase will include installation of additional VAV DDC fan coils under each window around the building perimeter to satisfy the final floor layout. This system approach will maintain the very low ceilings throughout the building.

Finally, a new 100% outdoor-air AHU—required by code because the building has multi-purpose occupancy functions—will be located in the attic and ducted down vertically through corridor walls. This unit will supply a small amount of air to each occupied space and provide corridor cooling throughout the building.

The AHU itself will include 80% filters, heating and cooling coils and a variable-frequency drive to save energy based on a carbon-dioxide room-sensing control scheme.

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