AREN 3050 Environmental Systems for Buildings I Fall 2005 Modified Heating Load Homework Due Thursday, September 29 1. Consider a double glazed operable window with overall dimensions of 3 ft wide by 5 ft high. The window glass is clear and has a ½” air gap. The frame is wood. a. What is the U-value in the center of the glass for a typical window with this construction? b. What is the U-value of the overall assembly for a typical window with this construction? c. What is the rate of heat transfer through the window in units of Btu/hr? d. What is the reduction in heat transfer rate if there were a low-e coating with an emissivity of 0.20 on one of the inner surfaces of the glass assemblies? 2. Consider the corner office on the tenth floor of a 20-story building. The room is 10 ft by 20 ft with a 10-ft high ceiling. Each of the two exposed walls has a 3 ft by 5 ft window with a U-value of 0.5 Btu/hr ft2°F. The exterior walls have an R-value of 10 (hr ft2 F)/Btu. These values are both overall values and include the effects of inside and outside surface resistance. The entire office building, including the corner office, is maintained at 70°F. Assuming no solar heat gain through the windows, what is the steady-state heat loss from the room when the outdoor temperature is 0°F? 10’20’0°F70°F 3. Problem 4.3 in the text.AREN 3050 Environmental Systems for Buildings I Fall 2005 4. Consider a single-family, detached, single-story house located in suburban Long Island. The location has a design outdoor temperature of 13°F and the indoor temperature is typically maintained at 70°F during the heating season. The house is built on a slab-on-grade foundation and has no garage. The house has the following characteristics: General Length 56 ft Width 32 ft Wall height 8 ft Perimeter 176 ft Floor area 1792 ft2 Gross wall area 1408 ft2 Net wall area 1114 ft2 Window area (openings) 252 ft2 Door area (openings) 42 ft2 Roof area 2060 ft2 Gross volume (living area) 14,366 ft3 Construction quality Tight Foundation Slab on grade with 8-in. foundation walls with and vertical board insulation on outside of foundation walls R-value of insulation 5.4 (hr ft2°F)/Btu U-values Walls 0.084 Btu/(hr ft2°F) Windows 0.420 Btu/(hr ft2°F) Doors 0.350 Btu/(hr ft2°F) Roof/ceiling (based on ceiling area) 0.030 Btu/(hr ft2°F) Using the information presented above, perform the following calculations to determine the design heating load for the house. a. What is the design heat loss through the above-grade building envelope (walls, windows, doors, ceiling/roof)? b. What is the design heat loss due to heat transfer through the slab-on-grade floor? c. What is the design heat loss due to infiltration? d. What is the total design heating load for the