This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
49. Heating and ventilating work should be estimated as indicated in the following paragraphs.
Itemize all valves, air vents, hangers, etc.
Estimate on pipe coverings by lineal foot.
Estimate sheet-metal indirect-radiator casings in pounds.
Estimate sheet-metal flues and smoke pipes by the lineal foot; but elbows and dampers separately.
Figure heaters, steam boilers, and furnaces from manufacturer's catalogues.
The cost of a hot-air installation is approximately 5 per cent. of the cost of the building; for steam heating, 8 per cent.; and for hot-water heating, 10 per cent.