=95. Heating and ventilating work= should be estimated as indicated in
the following paragraphs:
Estimate all pipes and fittings the same as for plumbing. Sum up all
standard radiators, and the price per square foot of radiation. Figure
special radiators separately.
Itemize all valves, air vents, hangers, etc.
Estimate on pipe coverings by linear foot.
Estimate sheet-metal, indirect-radiator casings in pounds.
Estimate sheet-metal flues and smoke pipes by the linear foot; but
estimate elbows and dampers separately.
Estimate register boxes, registers, and borders separately.
Make separate items of expansion tanks, hot-water damper regulators,
and furnace regulators.
Figure heaters, steam boilers, and furnaces from manufacturers’
catalogs.
In estimating on heating by furnace, the average cost of labor is about
one-third that of materials. For steam and hot-water heating, the ratio
is about one-fifth.
The cost of a hot-air installation is approximately 6 per cent. of the
cost of the building; for steam heating, 8 per cent.; and for hot-water
heating, 10 per cent.