1. Your firm is inspecting an existing building located in Minneapolis, MN that was built in 1932 and hadadditions in 1963 and 1996. Heat is provided by a 68% efficient atmospheric natural gas boiler and gas costs $1.25/therm.a. How many degree days were there at base 65°F in Minneapolis from 5/20/2013 thru 5/19/2014?Use the weather station "KMSP: MINNEAPOLIS-ST PAUL INTERNATIONAL, MN, US(93.23W,44.89N)" to derive weather data.Note: http://www.wunderground.com/ is your best source - you do not have to calculate HDD for each day, just find the total HDD for the period noted.
2. The inspector investigates the attic spaces and finds that there is an existing 3" of rock wool insulationabove the main building, which measures 2,843 SF. There are 2 additions, one of which measures 975s.f. and has no insulation (assume a baseline R-value of 2 here attributable to the structural elements ofthe roof assembly). The other has 12" of cellulose and measures 450 s.f. Minnesota State Energy Coderequires R-44 in the attic for new construction. The cost for installing 12" of loose-fill cellulose is $3.50/s.f.Costs for installing lower amounts decrease, but not linearly. Installing 10" is $3.00/s.f., 8" is $2.75/s.f., 6"is $2.50/s.f., 4" is $2.25/s.f. and 2" is $2.00/s.f. Assume R-value of 3.5 per inch for cellulose and for rockwool.a. Where would you call for insulation? How many inches?b. How many therms of gas would the building save as a result of the added insulation? Use theequation U*A*ΔT to derive hourly heat loss of each roof assembly (pre and post retrofit). Toderive ΔT, divide the total number of heating degree days in the year by the number of days inthe heating season. Assume the heating season goes from Oct. 15 through May 15. Rememberthat once you have derived hourly savings, you then need to determine annual input fuel savings.c. What is the simple payback period in years associated with adding insulation in each section tobring the entire roof up to code? (Simple payback = installed cost divided by annual dollarsavings resulting from energy savings.)d. What is the simple payback period in years if the heating is provided by a 78% efficient #2 fuel oilboiler (#2 fuel oil contains 139,000 Btus and costs $3.00/gallon)?
The building has four exhaust fans on the roof, each sized to exhaust 200 CFM continuously. Local codehas changed, allowing you to lower the exhaust rate of each space by 50%. You decide to retrofit the exhaust fans with smaller fans, each sized to provide 100 CFM. You are happy because you can easilyfigure out the electricity savings by looking at the spec sheets on each fan. However, figuring out the savings due to exhausting less air requires math. In fact, it requires the same math as determining savings from air leakage reductions in buildings from air sealing.a. Using the equation CFM*1.1*HDD*24 = BTUs saved, derive the input fuel savings in therms ofgas from the exhaust reduction given the atmospheric boiler.- CFM = delta between pre and post CFM- 1.1 = heat carrying capacity of air- HDD = HDD from 5/20/2013 - 5/19/2014- 24 = hours in a dayb. Now assume that you have a 92% efficient condensing boiler. How much money are you savingby not having to generate those BTUs?