1. Heat Loss HVAC CNST 305 Environmental Systems 1 Dr. Berryman

2. Heating Load Componentsroofexteriorwall glassconduction floor Infiltration and Ventilation partitionwall

3. Design Temperatures Inside Outside

4. Design Weather Data St. Louis, Missouri St. Louis, Missouri DB 99.6% 99% 2°F [-16.7°C] 2°F [-16.7°C] 8°F [-13.4°C] 8°F [-13.4°C] 1997 ASHRAE Handbook–Fundamentals, Chapter 26 St. Louis, Missouri St. Louis, Missouri DBWB 0.4% 1% 2% 95°F [35°C] 95°F [35°C] 76°F [25°C] 76°F [25°C] 93°F [34°C] 93°F [34°C] 75°F [24°C] 75°F [24°C] 90°F [32°C] 90°F [32°C] 74°F [23°C] 74°F [23°C] Summer Winter

5. Conduction Heat Losses BH = U  A  T

6. Rates of Heat Transfer

7. Air Spaces

8. Determining Rates thermal resistance (R) outdoor-air film AL siding (hollow back) 8” LW concrete block R13 insulation board ½”gypsum board indoor-air film Table 2-2 (Toa) Table 2-3 Table 2-4

9. Heat Loss Calculation EXAMPLE Using wall section: Winter Design: 10 o F DB Indoor Design: 75 o F 100’ long; 10’ high Determine Heat Loss

10. Degree Day Heating load is proportional to the temperature difference between 65 o F and the average daily winter outdoor temperature. Example: Omaha, NE 65 o F - -8 o F = 73 degree days Winter Design = -8 o F w/ 6612 degree days* *From ASHRAE Handbook of Fundamentals 6612/73 = 90.6 heating days 90.6 x 24hrs = 2174 heating hours/year

11. Floors – Slab on Grade MildCold Climatic Conditions

12. Basements Heated basements: Unheated basements Use 50 o F for OA design temperature Calculate R-values through floor Note: Any exposed wall above grade has to be calculated a different wall section

13. Pier & Beam (crawl space) Same as wall/roof Use Design OA temperatures Calculate R- values through floor Use OA Design Temperature

14. Other Heat Losses Wall Roof Floor Windows Doors Infiltration Ventilation BTUH Total

15. Sample Heat Load Form

16. Assignment Wall Section Sketch (on graph paper) Show in one section: roof, wall, floor Provide dimensions, material call-outs Determine rates of heat transfer R values of each construction R Total U value Determine indoor/outdoor design temperatures

17. Next Time Heat Transmission Condensation Vapor Barriers