1)Does ECJ have a larger heating or cooling load? A.Heating B.Cooling

Objectives Calculate building heating and cooling loads Ventilation and infiltration (sensible and latent) Ground contact (F-value) Increased conduction through opaque surfaces Glazing (conduction and radiation) Internal gains (sensible and latent)

Heating and Cooling Load Procedures Handout Calculate heating load Add additional calculations for cooling load Internal gains Solar gain Increased gain through opaque surfaces Need also to calculate latent cooling load

Weather Data Chapter 27 of ASHRAE Fundamentals For heating use the 99% DB value 99% of hours during the winter it will be warmer than this Design Temperature Elevation, latitude, longitude Heating dry-bulb –99.6% and 99% values

For cooling use the 1% DB and coincident WB for load calculations 1% of hours during the summer will be warmer than this Design Temperature Use the 1% design WB for specification of equipment Facing page 0.4%, 1%, 2% cooling DB and MWB 0.4%, 1%, 2% cooling WB and MDB

2) What is the heating ΔT for Austin? A.25 °F B.30 °F C.30 D.30 °C E.40 °F

Heating and cooling loads Everything gets converted to a “UA” Except Solar gain through glazing Internal gains Multiply it by the design temperature difference Add solar gains, internal gains

Solar Gain Increased conduction because outside surfaces got hot Use q = UAΔT 1.Replace ΔT with TETD Tables 2-11 – 2-13 in Tao and Janis (2001) 4 pm for a dark colored surface 2.Replace ΔT with CLTD (Tables 1 and 2 Chapter 28 of ASHRAE Fundamentals) For residential buildings only 3.Sol-air temperature Table 29-15

Glazing q = UAΔT+A×SC×SHGF Calculate conduction normally q = UAΔT Use U-values from NFRC Certified Products Directory ALREADY INCLUDES AIRFILMS Use the U-value for the actual window that you are going to use Only use default values if absolutely necessary (Tables 4 and 15, Chapter 30 ASHRAE Fundamentals) ALREADY INCLUDES AIRFILMS

Solar Gain Through Windows Add to conduction A× SHGF × SC SHGF = solar heat gain factor Measure of how much energy comes through an average “perfect” window Depends on –Latitude –Orientation –Time of Day –Time of Year Tabulated in ASHRAE Fundamentals 1997 Chapter 29 Table 15 Tao and Janis Table 2-15 for 40° latitude (July 8 am)

Shading Coefficient Ratio of how much sunlight passes through relative to a clean 1/8” thick piece of glass Depends on Window coatings Frame shading, dirt, etc. Use the SHGC value from NFRC for a particular window Default values in ASHRAE Fundamentals Table Lower it further for dirt, blinds, awnings, shading

More about Windows Spectral coatings (low-e) Allows visible energy to pass, but limits infrared radiation Particularly short wave Can see it with a match/lighter in older windows Tints Polyester films Gas fills All improve (lower) the U-value

Low-  coatings

What is the total cooling load in Austin associated with the following window? 10 ft 2, south facing, aluminum framed (no TB), double glazed, no coatings

Internal gains What contributes to internal gains? How much? What about latent internal gains? ASHRAE Fundamentals ch. 29 Table 1 – people Table 2 – lighting, Table 3 – motors Table 5 – cooking appliances Table Medical, laboratory, office

5) The latent load of a building is needed to calculate __________. A)Heating only B)Cooling only C)Heating and cooling

Conclusions Conduction and convection principles can be used to calculate heat loss for individual components Convection principles used to account for infiltration and ventilation Radiation for solar gain and increased conduction Include sensible and internal gains