Ideas to fuel a sustainable built environment

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Creating a Bid Document for a Ventilation VAV Retrofit

Jul 1, 2015 12:00:00 PM

After completion of an ASHRAE Level 2 Energy Audit, a building owner is faced with the question of how to move on to the implementation phase of the identified energy saving opportunities. The audit report provides estimates for annual energy savings for each opportunity, as well as the simple payback to help determine if the measure is financially feasible. However, the audit does not design a measure in enough detail that a contractor can accurately bid or install the measure so that the savings are realized. Therefore we suggest that the building owner hire a technical consultant (designer or commissioning engineer) to develop a bid document that details the design of the measure. This technical consultant must understand the owner’s goals and expectations for the project.

This blog will explore how a suggested measure is moved into the implementation phase with the creation of a full bid document for the building owner. My example is creating a bid document for an office/ multi-family building where the building owner is interested in the replacement of an existing ventilation air handler to operate as a full variable air volume (VAV) system.

VAV Air Handler Schematic VAV Air Handler Schematic

Overview of the Measure

After reviewing the ventilation requirements for both the offices and the multi-family section of the building for our audit, we determined that the office area is over-ventilated and the existing air handler providing the ventilation air is oversized. Having over-ventilation means the unit is using extra fan power and requires more cooling and heating of the outside air. In addition, the multi-family section of the building requires a 24/7 supply of ventilation air, however, the office space does not. This current system does not have the ability to vary the air flow going into these spaces. Therefore, in addition to sizing a smaller unit, the proposed design will allow the variable speed air handler to ramp down during unoccupied periods for the office spaces but keep constant ventilation for the 24/7 multi-family section of the building. In a future blog post, I will discuss this current system and the proposed design in more detail.

Bid Document Process

We were asked by this particular owner to put together a bid document for the design of this ventilation VAV retrofit. We are still in the process of putting together this document, but it will ultimately include the following:

  • Mechanical and electrical coordination with the existing distribution system
  • Specifications for all new equipment (air handler, VAV boxes, controls)
  • Proper installed location of the new equipment
  • Detailed control sequences to program the system properly for comfort as well as energy savings

This bid document will enable accurate pricing to be worked up from a mechanical contractor, electrical contractor, TAB contractor, controls contractor and of course – a commissioning contractor!

A VAV box during installation A VAV box during installation

Why a Complete Bid Document is Important

Having a comprehensive bid document with all necessary information needed for the new system allows the contractors who are bidding the work to fully understand the scope of work without needing to ask a bunch of questions. It will make it easier for the owner to compare the bids equally and fairly, because they are confident that each contractor is pricing the exact same design. And, most importantly, it will ensure the project realizes the intended benefits for the owner.


Written by Katie Mason