Indoor Air Quality

Make-Up Air Units

In most cases, the need for ventilation air is achieved by the addition of a make-up air unit(s). These units are essential to a building's mechanical operation and to the health and comfort of its occupants. By providing a controlled quantity of clean, conditioned ventilation air to common areas of the building, they:

• Reduce drafts, dust and dirt entering the building;

• Replace air exhausted by equipment such as kitchen or bathroom fans or process or industrial exhaust fans;

• Reduce odours.

A make-up air unit consists of a fan and a heat-exchanger component as well as filters and dampers. Gas-fired units are available in many sizes to meet building ventilation needs and are supplemented by a variety of control components (both temperature and air quality) and operating strategies. Control systems are important as they can be designed to handle 100% outdoor air or to mix outdoor air with re-circulated indoor air. Mixed air systems can be electronically controlled. Heating can be provided at fixed or variable heating rates and control strategies for these systems can also vary from simple manual systems to computerized options.

Depending on the application, make-up air units can be installed either on rooftops or indoors. High-rise buildings generally install their units on rooftops, where they are mounted on either a curb or metal roof frame, then connected with the building's electrical and ductwork system. In walk-up apartments, units are often installed in utility or attic rooms and conventionally ducted to feed air to the corridors and common areas.

A variety of features are available that will enhance the performance of make-up air units, including:

• Heat reclaim coils or heat wheels, to recover waste heat;

• High efficiency filtration to maintain air quality and automated controls governing both temperature and air quality to minimize energy consumption - including capacity control utilizing two-stage or modulating gas valves that will match the unit's output with your building's needs.

Electric make-up air heaters can also be converted to natural gas by installing a heating coil in the duct, which is heated by hot water that is supplied by a gas-fired boiler.

Contact a contractor for more information on make-up air units.

Heat Recovery Ventilators (HRVs)

Heat recovery ventilators (HRVs) are devices that recover heat from building exhaust air and transfer it to supply/fresh air entering the building via an air-to-air heat exchanger. The unit also captures coolness of exhaust air in summer thereby reducing air conditioning energy costs. Typical unit payback from energy savings alone is 2.5 years and potentially less if there are capital cost savings associated with reducing HVAC heating equipment size by 25% (more or less depending on occupant load and facility type).

Energy Recovery Ventilators (ERVs)

Energy recovery ventilators (ERVs) are even more energy efficient, exchanging both heat and moisture (sensible and latent energy) via a desiccant enthalpy wheel or other moisture transfer technology. This reduces the latent load on the air conditioner, enabling it to control humidity more effectively, while lowering operating costs.

When an ERV system is integrated with HVAC systems, the resulting conditioning and/or heat recovery allows for reduction of the size of HVAC systems. This provides savings in both capital investments and operating costs.

Contact a contractor for more information on HRV systems.

Contact a contractor for more information on ERV systems.