Energy Conservation Through Building Automation Systems

(excerpt from Condo Business Magazine's Green Issue, April 2012)

With a growing demand for energy conservation and a reduction in operating costs, condominiums are always searching for energy saving methods. Energy efficiency in high-rise multi-residential buildings can be achieved through a variety of retrofits including lighting, variable frequency drives, carbon monoxide monitoring systems, and occupancy sensors. However, one method that is often overlooked is the use of an Energy Management System (EMS) or Building Automation System (BAS) – these are systems that can improve energy efficiency within the building’s mechanical plant.

What is a building automation system?

A mechanical plant is a complex system of boilers, chillers, pumps, valves, and fans that provides heating, cooling, ventilation, and water throughout the building. When the building systems are functioning properly, residents won’t notice them, but when they're not, they can cause a lot of complaints – just imagine the last time there was no hot water in the building.

A building automation system allows for control and integration of the building plant. By scheduling, adjusting, and monitoring the major mechanical plant equipment, the system will become more efficient, reduce energy consumption, and reduce operating costs all without sacrificing resident comfort. The mechanical systems are generally set to meet the highest demand expected for a given season and not necessarily the actual demand at a given time. Essentially, the different elements of mechanical equipment are designed to run at full speed and power at all times which can result in wasted energy consumption. Although most building automation systems are designed primarily for HVAC (heating, ventilation, air condition) control, many systems can also incorporate additional functions, such as lighting control, computerized maintenance scheduling, life-safety functions, and security access control.

The biggest benefit of a building automation system is energy savings. Most engineering sources estimate that the total energy savings to between 5-15% of the building’s annual energy consumption. This means thousands of dollars in annual savings.

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Make Up Air Units and Variable Frequency Drives

Corridor Fresh Air Units or Make-Up Air Units (MUA) are found in virtually all High Rise Multi-Residential Buildings. Older buildings, including rental properties, often have these units with no heating or air conditioning of the air introduced into the building. In newer buildings and in virtually all condominiums, these units do provide heating and cooling of the fresh air.

The purpose of the MUA units is threefold. First, the units slightly pressurize the building in order to prevent infiltration of outdoor air through the building envelope. Second, the units provide, as the name implies, ‘make up air’, to replace air that has been exhausted from the building by in suite exhaust fans. The third purpose is to provide for ‘air changes’, or fresh air for comfort and respiration.

The Canadian Mortgage and Housing Corporation (CMHC) have done numerous studies on make up air units, and have found some very interesting results. One of the things that were found was that this air often leaks through the building envelope in unintended ways.Air can leak through door openings, envelope penetrations, elevator shafts, stairwells, and other places where the air can find its way directly to the outside. The result is that Fresh Air Units can be tremendous energy ‘wasters’. When fans are sized during the construction phase, they are often sized using the assumption that a certain number of exhaust fans will be running at the same time. This is referred to as the diversity factor. Clearly, at night and at other off-peak times, the actual use of exhaust fans will be well below the diversity factor used to size the fans.

One excellent solution is the use of Variable Frequency Drives (VFD). The fan can be operated on a time of day schedule, speeding up and slowing down as needed. Variable Frequency Drives today are much more reliable than they have been in the past and their increased use has driven installation costs down. Provident Energy has supplied and installed hundreds of VFDs and we highly recommend their use in a wide range of applications.

For more information regarding VFD applications for your building or to arrange a free energy assessment, please contact the sales department at Provident Energy at 416-736-0630, extension 5.