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Show materials and $ 1.80 is for labor. Labor costs may seem high, but if the pipe is to be completely insulated with no thermal breaks, installation will require careful placement of lines and insulation, and larger holes thru studs, beams, and walls to accommodate the insulation. Careful attention to bends, corners, tees and crosses with extra time and material to properly insulate these difficult areas will require increased labor costs. Current trends in residential construction point to more master bedrooms and guest quarters. These areas tend to be isolated from the kitchen and living areas and require longer pipe runs. Typical new construction may have up to 400 feet of hot water lines to various points in the house. Hot water line runs of 100 feet from a hot water heater to a shower are not unusual and they are assumed for this analysis. Based on the aforementioned typical residential construction, initial installation of insulation on all hot water pipes is estimated to be $ 800. If only lines to shower and or tub/ showers are insulated, the cost is $ 400 ( based on a master bathroom in addition to the regular bathroom). Benefits included in the analysis include reduced water bills and lower energy use. If water rates are assumed at $ 1.00 per thousand gallons, water savings benefits are estimated at $ 2.50 per year for the average household in Utah. Using equations developed to calculate energy savings based on number of gallons saved, and assuming water temperature will be raised 42 degrees for delivery at the showerhead, energy savings for hot water heating are estimated at 1.11 Million British Thermal Units ( MBTUs) per year per household. Because most water heating in Utah is by natural gas, and assuming a natural gas cost of $ 4.85 per MBTU, energy savings are estimated at $ 5.40 per year for water saved in showers. The net present value ( using the current state discount rate of 4.13 percent) of $ 2.50 per year for water savings and $ 5.40 per year for energy over 30 years is $ 43 and $ 92 respectively. Subtracting these benefits from the cost of insulating all hot water pipes in new residential construction leaves a cost of $ 665 ($ 800 - $ 92 - $ 43) for 0.23 acre- feet of water conserved. This is equivalent to $ 2,890 per acre- foot of water conserved. If comparisons are made strictly for water conservation, the cost per acre- foot is high, estimated in excess of $ 2,500 per acre- foot compared to other alternatives. If only those water lines to showers and tub/ showers are considered, then the net cost is $ 265 ($ 400 - $ 92- $ 43) per 0.23 acre- feet or $ 1,150 per acre- foot. The foregoing calculations assume that water in insulated pipes will not lose heat during transit. However in the situation of water standing overnight in small diameter water lines typical of residential construction, there is significant heat loss. Thermodynamic calculations for static hot water in an insulated copper hot water line of 3/ 4 inch diameter indicate a temperature decrease from 120 degrees F. to 60 degrees, or ambient temperature, within six hours. As a result no water is conserved on the first use in the morning. • 68 |