Class Definition of an HVAC System:

"An HVAC system is a series of components that work together to condition the 

air to achieve and maintain the desired requirements"

In Macalister Hall the HVAC system is composed of several components, including air handling units, a chiller, a cooling tower, a heat exchanger, piping, ductwork, and heating/cooling coils. These components work together to create comfort in this building, and each component is just as important as the next in the overall comfort picture.

As stated, Macalister Hall was designed in 1969 with a completed construction in 1974. The dominant HVAC system in the facility is a constant volume reheat system that was originally served through five air handling units.

HVAC Systems:

Constant volume reheat systems are good because they provide air movement and humidity control, along with individual temperature control for each reheat coil. On the negative side, a reheat system is highly inefficient because the air is cooled to the lowest possible temperature required to meet loading conditions, and then heated up from that point to provide air for the other spaces. The fact that this building was designed in 1969, just before the energy crisis, is a testament to the installation of a reheat system, when efficiency was not as large as a concern as it is now.

In addition to the reheat system, fan coil units were also installed in select locations to complement the air system. Once again, this is highly inefficient because only one system is required. Since they installed a reheat system, individual temperature control is possible, so the installation of a fan coil unit is excessive. If the engineer was worried about skin losses during heating seasons, the installation of fin tube radiation would have been appropriate.

HVAC Equipment Overview:

The following equipment is located in Macalister Hall or serves Macalister Hall and will be discussed in the following pages:

Mechanical Room Space Allocation:

There are two major mechanical rooms located in Macalister Hall, one in the basement and one on the roof. A breakdown of the spaces follows.

Basement Mechanical Room

The basement mechanical room houses three air handling units, two abandoned chillers, three hot water circulation pumps, a heat exchanger, two hot water storage tanks, and an air compressor for the pneumatic controls. The mechanical room measures approximately 4,400 ft² (shown in green) and there are two outside air intake wells on the north side of the building (shown in pink).

Penthouse Mechanical Room

The penthouse mechanical room is broken into two parts, one room for the elevator machine equipment (shown in blue) and a mechanical room housing two air handling units (shown in green). There is an outside air intake louver on the north side of the penthouse shown in pink. The penthouse is constructed of corrugated metal siding. The "green" mechanical room measures 1,300 ft² .

The mechanical spaces in this building occupy a total of 5,700 ft² , which percentage wise of entire building square footage, the mechanical rooms take up approximately 5% of the total floor space. This number does not include the mechanical shaft which takes up 90 ft² on each floor. This mechanical shaft most likely accommodates piping, ductwork (supply and return), and electrical conduit. The mechanical shaft is shown in green in the following typical floor plan:

Construction Materials:

From a construction standpoint, the main materials are precast concrete, brick, and concrete block in the wall construction. There is very little to no insulation in the walls of this building. Air gaps in the walls range from 1" on the first floor to a varying 6" in the tower. The sixth floor and penthouse have a metal facade. The roof is a standard built up roofing system and the windows are aluminum framed with double panes. The floor to floor heights in the tower are 12'-0" and the heights on the first floor are 15'-0", these values will play an important role in finding volumes of the spaces and areas of the walls.

Directional Facings:

Macalister Hall is located on the corner of 33rd and Chestnut Streets in Philadelphia, PA. The building has four exposures facing in the cardinal directions, as it is built within the grid system of Philadelphia. In the tower, there are larger facings to the east and west as opposed to the north and south in the ratio of 1.25:1. This directional facing is good from an energy standpoint because the south side of the building, with the maximum solar load, has the smaller exposed area.