The Summit at
Drexel University
HVAC System
The 2-story dining space and 25-story residential space basically have their own separate HVAC systems.
Dining Space HVAC System
Heating and Cooling:
The dining space consists of a lower level and a mezzanine level, and is heated by radiant flooring. The floor is heated by a hydronic system where fluid flows in pipes. The piping is secured to a grid and embedded within the poured concrete slab. This is called a poured floor system or a wet system. The photograph above shows piping that is secured to a grid, before concrete is poured overtop. Since the system in the building uses hydronic piping rather than electric heating elements, the system can be used to heat AND cool the building.
The hydronic system uses a mix of water and anti-freeze as a heat transfer fluid in a closed loop that recirculates between the floor and the boiler. The boiler is located on the mechanical mezzanine level. The boiler uses natural gas to heat the water. This is considered the cleanest and most efficient method of heating water. The heat pumps and chillers are powered by electricity or natural gas. An air separator is used to remove air from the flow of fluid through the pipes. There is an expansion tank stores up to 10 gallons of fluid. The riser diagram for the radiant floor heating is shown above.
Condenser System:
The condensation that gathers in the hydronic piping needs to exit the pipes. There are separate condensate pipes that carry water brought in by condensate pumps. There is one condensate pump for each heat pump. The detail above shows a typical drain. The condensation either exits through the condensate piping to the nearest drain or enters the cooling tower. The cooling tower can evaporate the condensation.
Exhaust and Ventilation:
In the dining area, there are vertical exhaust ducts with cleanouts at each floor that exhaust up to the roof. The exhaust ductwork attaches to the kitchen hood and exhausts up to a fan on the roof. The exhaust and flue vent terminate on the mezzanine level. A supply duct travels from the make-up air unit, located on the loading dock roof, for ventilation of the dining area. The ventilation air is distributed by linear slot diffusers that line the walls of the dining space.
Reasons for System Selection in Dining Area:
Radiant floor heating provides a high quality of thermal comfort. This system is unique because it uses radiant exchange from the floor to the air, convection by the floor’s surface onto the air, and convection from the floor to the occupants’ feet.
Radiant floor heating also can have a positive effect on indoor air quality. In construction, flooring such as tile, terrazzo, and concrete are avoided because they a cold. By using radiant floor heating, ceramic tiled flooring could be used, which has very low VOC emissions in comparison to other flooring materials. This type of heating establishes temperature conditions that make it less likely to have mold, bacteria, and viruses. This is very useful in a dining facility, where mold, bacteria, and viruses are common.
In dining spaces, the floors need to be cleaned everyday because of spills or for sanitary purposes. Radiant floors work well under these conditions because they speed up the evaporation of wetted floors.
In addition, the design team may have chose radiant floor heating because it does not take up any wall space. This means that fewer penetrations had to be made in the walls, and fewer problems between the various subcontractors and trades.
Alternative HVAC Systems for Dining Area:
Rather than having a separate system for the dining space, the design team could have treated the building as one space. Instead, water source heat pumps could be used throughout the entire building, rather than having radiant floor heating in the dining area.
Residential Tower HVAC System
Heating and Cooling:
The main component of the HVAC system is the water source heat pump. Each apartment has its own heat pump. Piping connects the heat pumps, boilers, and cooling tower. The pipes carry water to heat the building. A vertical riser is required for each pair of vertically stacked heat pumps. The right picture above shows these risers. There are four boilers on the penthouse that use natural gas to heat the water. There is also a cooling tower on the penthouse roof that cools the water. The cooling tower is photographed in the left picture above. The two heat exchangers on the roof exchange the energy from the water to air, to provide heated air.
This air is distributed through ducts and supplied through supply air registers to each of the apartments. The make-up air-handling units on the roof connect to the ductwork that supplies conditioned air through the apartments and returns air from the apartments back to the MAU. The photograph above shows one of the supply ducts in an apartment that carries air from the MAU to the apartment. Make-up air units supply 100 % outside air and no recirculated air.
Condenser System:
The condenser system works the same in the residential tower as the dining space. The condensation that gathers in the hot water piping needs to exit the pipes. There are separate condensate pipes that carry water brought in by condensate pumps. There is one condensate pump for each heat pump. The condensation either exits through the condensate piping to the nearest drain or enters the cooling tower on the penthouse roof. The cooling tower can evaporate the condensation.
Exhaust and Ventilation:
There are make-up air units that replace exhausted air with outdoor air to ventilate the bathrooms. There are two make-up air units on the penthouse roof that are connected to vertical exhaust ducts that carry exhausted air from the bathrooms. There are separate exhaust fans on the penthouse roof that connect to exhaust ducts that carry exhausted air from the kitchens and dryers.
Reasons for HVAC System Selection in Residential Tower:
The designer decided to have individual heat pumps for each unit because it is a cheap way to heat and cool apartments. Since this is a residential building, the residents will want to control the temperature of their apartment. Having individual heat pumps allows each apartment to be controlled separately.
Alternative HVAC Systems for Residential Tower:
There are other HVAC systems that could have been used in this building. The individual heat pumps installed in each apartment act as small chillers. Rather than having individual heat pumps, the building could have had a central chiller, boiler, and cooling tower. CAV or VAV boxes could then be installed to control the air travelling to each space.
