221HEATING, VENTILATING,
AND AIR-CONDITIONING
CHAPTERNINETEEN
Estimators need a general knowledge of heating, venti-
lating, and air-conditioning to understand the equipment
involved. Figure 19.1 contains commonly used HVAC sym-
bols and abbreviations. There are many different systems
that could be used on a building. If the estimator is unfamil-
iar with a system, it is wise to call the manufacturer’s repre-
sentative to get a full explanation. In this way, the estimator
will understand what is required of the general contractor
and the subcontractor to guarantee a successful installation.
Estimators check the specifications carefully to be sure
that the materials they (or their subcontractor) bid are those
specified. To improve accuracy from job to job, good estima-
tors keep a complete file of all costs and a breakdown of costs
from subcontractors—and they check job against job. It is
suggested that they go through the specifications item by
item to be sure that all are included in the takeoff.
Another method used for approximate estimates is the
use of square feet of building. Also, prices per btu, cfm, and
tons of air-conditioning are sometimes quoted. If used with
caution, these procedures may be effectively employed for
comparison of prices.19–3 Separate Contracts
The same general conditions prevail with HVAC work under
separate contracts as when the electrical and plumbing are
bid as separate contracts. Estimators must understand the
mutual responsibilities involved and what the coordination
requirements are. The work still must be integrated into the
building construction. They will review the drawings and
check that there is space for the ducts, pipes, and other
mechanical lines.19–4 Coordination Requirements
Listed in Figure 19.2 are the major areas of coordination
required between the HVAC and general contractors.19–1 HVAC WORK (HEATING,
VENTILATING, AND
AIR-CONDITIONING)
As in electrical and plumbing work, this portion of the work
may be bid under single or separate contracts. Bidding under
separate contracts for HVAC work is similar to bidding
under separate contracts for electrical and plumbing work.
Understanding the mutual responsibilities and coordination
required is a must (Section 19–4).
Like all work, this portion must be designed and
installed in accordance with all federal, state, and local codes.
Many different codes may have control, depending on the
types of systems used.
Again, the field experience, understanding of design
principles, and ability to understand drawings and specifica-
tions are key points. There is a tremendous variety of instal-
lations that may be used in this portion in dealing with
electrical heat, ventilating ceilings, and various methods and
fuels used for heating and air-conditioning.
19–2 Single Contracts
Subcontractors who specialize in this type of work will be
submitting bids to estimators, so your area of responsibil-
ity falls within the preparation of an approximate bid for
comparison.
Referring to the working drawings and specifications, esti-
mators prepare a complete list of major items required. They
determine exactly where the responsibility for each portion
rests. If responsibility boundaries are unclear, estimators should
request that the architect/engineer clarify them, as it is unwise to
make assumptions about this or any portion of the project.
The takeoff includes piping, ductwork, drains, equip-
ment, fixtures, and accessories. The specifications will state
who is responsible for trenching, both from the road to the
building and within the building. The takeoff list should
include all equipment separately as to types and sizes.