Respuesta :
The question is incomplete, I came across the same question and here is the complete one:
Mary is considering upgrading the insulation in her house. Contractor suggests upgrading the insulation of her roof from R-16 to R-28. The estimate for this job from the contractor is $800. Her house is located in Pittsburgh, PA (HDD = 6,000) with a roof area of 1926 ft2. Mary’s home is heated with natural gas. Last year, the average price she paid for natural gas was $9.9/MCF. Assuming an AFUE of 81.2%, how long will it take Mary to recover her investment (in years)?
The answer is 8.83 years.
Mary is considering upgrading the insulation in her house. Contractor suggests upgrading the insulation of her roof from R-16 to R-28. The estimate for this job from the contractor is $800. Her house is located in Pittsburgh, PA (HDD = 6,000) with a roof area of 1926 ft2. Mary’s home is heated with natural gas. Last year, the average price she paid for natural gas was $9.9/MCF. Assuming an AFUE of 81.2%, how long will it take Mary to recover her investment (in years)?
The answer is 8.83 years.
Price of insulation = 800 / 1926 = 0.4153 $/sq.ft Cost of energy = 9.9 / 1,000,000 = 0.0000099 $/BTU Duration to recover investment = (0.4153 x 16 x 28 x 0.812) / (0.0000099 x (28 - 16) x 6000 x 24) = 8.83 yrs
