Review all construction documentation before proceeding with the estimate for HVAC. It is not unusual to find items on the plans, but not in the specifications; or they may be in the specifications but not on the drawings. Also check any and all communications; the owner may have requested a change or expressed a concern or a specific need, and not have had it included in your drawings or specifications.

Review All Drawing Divisions
It is important to review all of the drawings available to ensure that the systems called for will physically fit where they are supposed to. Sometimes the architect subcontracts out the HVAC design function. If the drawings are not carefully coordinated, a conflict may result, such as inadequate space under deep trusses where main ductwork was supposed to be installed and a required finished ceiling height maintained.

Check Drawing Scales
When utilizing drawings from different sections of the plans, always check to see if the drawing scales are the same. It has happened that an estimator has ended up with twice the length of piping needed (or worse, half) because he/she was not aware that the drawing scales varied from structural to mechanical.

Document All Inconsistencies
All inconsistencies with standard practice, conflicts, omissions, and other concerns should be addressed before the final estimate is resolved. Do not rely on memory, which can become quickly overloaded in a rush situation.

Temperature Control System
When estimating the cost of an HVAC system, check to see who is responsible for providing and installing the temperature control wiring system. In many cases, this item is overlooked, as it was assumed that it would be included in the electrical estimate. This can be a costly assumption.

Non-Listed Items
It is important to include items that are not shown on the plans, but must be priced. These items include, but are not limited to, roof penetrations and pitchpots, dust protection, coring floors and walls, testing and balancing HVAC systems, cleaning piping, cleanup, and final adjustments.

Cutting and Patching
Not all projects will be done under ideal conditions, that is, wide open spaces with no interferences. Many times the mechanical contractor will have to run duct or piping through pre-existing partitions or partitions that have been recently installed. Allowances must be made for cutting into the partition and the ensuing patching. Otherwise, a statement must be included with the estimate that all cutting and patching will be the responsibility of others.

Electrical Connections
Clarify who is responsible for connecting the electrical wiring to mechanical items. It has been argued that the electrician is responsible only for bringing the wiring to the unit, while others maintain that it is the electrician’s job to connect the wiring.