HVAC refers to any equipment associated with the heating, ventilation and air-conditioning systems required and specified in construction. During the design and planning process of a new construction project, a mechanical engineer specifies and designs an HVAC system to best fit the given project. This section of the building construction documents is drawn in great detail and offers a valuable and, in most cases, accurate resource for an HVAC subcontractor to estimate the materials and cost of the project. The process of estimating an HVAC job is a generally straightforward task that can usually be successfully completed by just about anyone with a general understanding of HVAC construction.

Step 1

Locate the scale of the mechanical engineering sheet of the building plans and the corresponding scale factor on the architect scale; the scale of the drawing is most commonly located under the title of the sheet.

Step 2

Measure and mark the total length of mechanical duct lines (refer to the sheets key for line types) and count the total number of turns the duct work makes, as turns in the duct work require the use of either flex duct or angle duct material. Depending on the project, there may be more than one type of duct (width or diameter) used on the project; in this case, make a list of the different duct sizes and mark the total length and number of turns for each. The size of the duct will be noted on the sheet and will be tagged to the specific duct area. Refer to the mechanical engineering sheet for specific product information, if applicable.

Step 3

Make a tallied list of all mechanical equipment; this category applies to fans, air handlers, heating units and air-conditioning units. The specifications for this equipment will be noted clearly either next to the individual units or on the key notes section of the sheet. The size (or capacity), model and manufacturer of the units should be included on the list. Refer to the mechanical engineering sheet for specific product information, if applicable.

Step 4

Make a tallied list of all supplementary mechanical equipment. This category applies to thermostats, vent grills and equipment mounting materials (may differ depending on local building code and specifications). Refer to the mechanical engineering sheet for specific product information, if applicable.

Step 5

Call a local HVAC building supply center and quote the current unit cost of listed items found in Steps 2 through 4.

Step 6

Multiply the current unit cost of each item by the number of items needed to find the total cost of materials for the project. For ventilation ducts, multiply the unit cost per foot by the total number of feet measured in Step 2.