Avoid oversizing mechanical equipment. Oversized equipment will often increase operating costs and reduce operational efficiency. The correct equipment size will depend on a number of factors, including local climate, total building area, insulation levels, air filtration medium, number of windows and doors, and occupant comfort preferences.

Implement energy recovery systems, economizers, low-pressure-drop design, and efficient fans as appropriate to support ventilation rates meeting or exceeding the referenced ASHRAE standard without compromising energy performance.

Wait until receiving bids to decide whether or not to pursue EAc3: Enhanced Commissioning. If you request two different fees for the two scopes, you can easily assess the cost and benefits of Enhanced Commissioning.

The mechanical engineer continues running ventilation rate calculations during the mechanical design process to confirm compliance with this credit and to inform the design. The ventilation rate procedure is explained in section 6 of ASHRAE 62.1-2007.

Case 1 – Mechanical Ventilation

Include commissioning costs during initial project budgeting to avoid later surprises.

An independent consultant, as compared to one from the same firm as the design team, is in the best position to truly represent the owner’s interests during design and construction, including installation of key systems. As commissioning agents are often experienced mechanical engineers, they can provide input into the project design and any recommendations on improved project efficiency.

Continuing to use an integrated design approach among the mechanical engineer, architects, owners and end users will facilitate design decisions that impact the mechanical design. For example, space planning decisions will impact the architectural programming of the space as well as access to natural ventilation. 

Early hiring and meeting attendance by the CxA during Enhanced Commissioning may be perceived as high cost, but should allow reduced on-site presence during construction and reduced errors during design and installation. It facilitates a preventive rather than reactive involvement.

At the first integrated design meeting during schematic design, develop a detailed natural ventilation strategy that includes goals for windows, building orientation, space planning and other sources of natural ventilation. In larger buildings, consider using an atrium to use the “stack effect”—allowing air to enter the building through exterior windows, cycle through the building into the atrium space and out through the top of atrium, using the natural buoyancy of warm air. Fans can be added, if necessary, to assist with stack-effect exhaust.