Reference 1

Reference 1 gives cooling load temperature differences (CLTD) for several latitudes, months, time of day, and building wall orientations.  These CLTD values are based on 78F indoors and 95F maximum outdoor temperatures.
In the heating degree day (DD) method, a no load outside temperature (65F)  is used as a base at which no heating or cooling is required.  At any outside temperature below 65F, a building will need heating and the number of degree days is the difference between 65F and the outside temperature.  For example, in November, if the outside average temperature is 50F, there are 15 degree days for that day.  For 30 days at 50F, there 450 DD.  The DD for the entire heating season September through May are given for various cities in Reference 4. Course Summary
© Gary D. Beckfeld  Page 16 of 21
This course has presented the basic methods of evaluating building heat gains or losses for air conditioning or heating.  Heat conductivity and thermal resistance were reviewed. A numerical example of heat loads to a building was described including external and internal heat sources.  Both sensible heat and latent heat loads were discussed.  The air conditioning process including ventilation was presented in a diagram of a psychrometric chart.  Cooling load tonnage was found and air handler flow and pressures discussed.  An air distribution duct sizing method was detailed. Finally, the methods of cooling load temperature difference and heating degree days were reviewed.