ACHRNEWS

To zone or not to zone? That is the question

April 28, 2000
In years past, the best way to achieve efficient temperature control in larger homes was with dual heating and cooling systems. However, in many homes, modern zoning systems not only provide better temperature control, they also may be more profitable to install.

That may be something of a surprise to contractors who have avoided specifying zoning in the belief that it would price their bids above competitors’ two-system bids. A cost analysis of the alternatives shows that zoning could actually provide a competitive advantage.

You might say the basis for that analysis is economies of scale — a single large system tends to be less expensive to buy and install than two smaller systems. Even with the cost of a zone control system and dampers, the overall cost of a zoned system comes out considerably less than two independent systems.

Cost breakdown

A typical two-zone, 5-ton system would cost the contractor $2,385 for equipment only. This reflects average or typical costs; regional variations, volume discounts, or promotional offers are not considered in this model.

Using the same model, two 2.5-ton independent systems would cost $2,925 to purchase. The zoned system in the first example is $540 less, even with the $345 additional cost of the two-zone control system cited.

The biggest saving comes from the furnace. The average cost of two 60,000-Btu, 80% AFUE furnaces is $480 each, or $960 for both. A single 120,000-Btu furnace in the example costs only $539, a saving of $421.

Buying one 5-ton condensing unit and evaporative coil saves $230 over the cost of two 2.5-ton units and coils.

Of course, there’s more to installing a system than the cost of hardware. Labor costs are the second largest contributor to the total system cost. It takes considerably less time to install a single zoned system than it does to install two independent systems.

Of course, actual labor costs vary considerably from region to region and from contractor to contractor. We will assume an average cost of labor (wages, benefits and allocated overhead) of $30/hr. Based on that assumption, the cost of a two-person crew comes to $60/hr.

If the zoned single-unit system takes 2 hrs less to install, then the labor cost is $120 less than that for a two-unit system. In that example, then, the zoned system costs the contractor $540 less in materials and $120 less in labor, for total savings of $660.

Staff skills

In the past, some contractors worried that training staff to specify and install zoned systems would increase the time required and therefore increase costs. But as the popularity of zoning has increased, new system designs have made it more simple as well as affordable.

A few homes demand a complex zone system because of dramatic shifts in thermal loads, unusual floor plans, or special uses. But in the majority of cases, a two-zone system is sufficient.

Many manufacturers have also made specifying easier with manuals that simplify the complicated calculations of the job.

In the majority of cases, ease of installation and the lower cost of equipment and labor have made zoning an easy choice. The hard decision is whether to use the savings to lower your bid or to increase your profit.