1. Your exhaust hoods requires 100 cfm (cubic feet per minute) per foot of exhaust hood. Your kitchen has six hoods, each 4 feet long. How much energy (in BTU/hr) will it take to heat the air entering the building to replace the air exhausted by the hoods for each of the three levels of makeup air listed below? The specific heat for air is 0.0175 BTU per cubic feet of air per degree Fahrenheit. The average outside air temperature for the month is 30F and the air is heated to 95F before it enters the room. The equation for calculating the energy needed to warm the outside air is:

Energy (BTU/hr) = Ventilation rate (ft3/hr) * Specific Heat (BTU/(ft3 F) * Temperature Change (F)

Express your answer to nearest whole number and use commas where required. (7 points)

a. 0% Makeup air (you must heat all air exhausted).

Energy =

b. 20% Makeup air (you only need heat 80% of the air exhausted).

Energy =

c. 60% Makeup air (you only need heat 40% of the air exhausted).

Energy =

2. If the gas used to heat the building in Problem 1 costs $1.75 per therm and there are 100,000 BTUs per therm, how much will it cost a month to heat the air entering the building to replace the air exhausted by the hood for each of the options below? Assume your heat plant is 90% efficient and that the hoods run for 18 hours each day. Assume that there are 30 days in a month. Calculate your answer to the nearest dollar and use commas where required. (7 points)

a. 0% Makeup air (you must heat all air exhausted).

Monthly Cost =

b. 20% Makeup air (you only need heat 80% of the air exhausted).

Monthly Cost =

c. 60% Makeup air (you only need heat 40% of the air exhausted).

Monthly Cost =

3. Based on the information from Problem 2, if you can increase the amount of makeup air from 0% to 60%, how much will you save (to the nearest dollar) on your energy cost over the next 20 years? Assume a monthly inflation rate of 0.9950% for gas. Your company has an anticipated monthly return on investment for the same period of time of 1.500%. (6 points)

ieffective = ((1 + inominal) / (1 + Inflation)) 1

PV = FV * (1 + inominal)-n

PV = A * (((1 + ieffective)n - 1) / (ieffective * (1 + ieffective)n))

Monthly savings =

Number of interest periods =

ieffective =

PVenergy savings =