Heating Losses- Infiltration and Ventilation

1. Heating Losses-Infiltration and Ventilation ARCH-432

2. Attendance • Which civilization made it a point to layout whole cities to take advantage of passive heating? In what direction did the city streets run? • Greece • Rome • Egypt • Persia • Babylonia

4. Attendance The ancient Greeks did this. What was shown is Priene (Priēnē); (5th Century B.C.), which had all of the streets laid out in an East-West fashion, thus allowing all homes to point South.

5. Attendance “Only primitives and barbarians lacked knowledge of houses turned to face the winter sun, dwelling beneath the ground like swarming ants in sunless caves.” Aeschylus

6. Greetings Capt. Kirk Aeschylus

7. Attendance Aeschylus pronounced Ess ca less One of the earliest writer of Greek tragedy – before him plays had single actors who could only respond to a chorus (group of people). Aeschylus increase the tragedy to two actors with dialog.

8. roof Infiltration and Ventilation Glass conduction Exterior wall Floor Big Picture Moment Ceiling Partition

9. roof Infiltration and Ventilation Glass conduction Exterior wall Floor Five main types of heat loss 1. Transmission (conduction) 2. Infiltration (convection) 3. Ventilation (convection) 4. Radiation (radiation) 5. Moisture migration Ceiling

10. Summary of Heat Losses • Wall • Roof • Floor • Windows • Doors • Infiltration • Ventilation Envelope Losses

11. What You Need To Know • The difference between ventilation and infiltration • Calculation methods for both ventilation and infiltration

12. What You Need To Be Able To Do • Calculate infiltration/ventilation loads • Be able to reduce/mitigate infiltration and ventilation loads • Employ techniques for increasing ventilation effectiveness

13. Terms • Infiltration • Exfiltration • Ventilation • Direct Outside Air System (DOAS)

14. Infiltration “The uncontrolled introduction of outside air into a building.”

15. Infiltration The uncontrolled introduction of fresh air into a building. 1. Most subjective of all losses 2. Oftentimes the largest of all heat losses. Sometimes comprises up to 30% of the total heating load. 3. Ends up being an “educated guess”

16. Why Is This Important? • All buildings leak • A tight building will leak .5 AC/H • A leaky building can leak 3 AC/H • Regardless of climate, air leaking into walls causes problems

17. Ventilation • The mechanical introduction of outside air (OA) to: • Replace Oxygen • Dilute contaminants • Pressurize the building

18. Moisture Load

19. Infiltration Calculation Methods • Crack method • Air Change Method • ‘Averaging’ method (‘I don’t know so I’m going to throw a dart’ method)

20. Crack Method • Presumes that an accurate estimate can be obtained by estimating the rate of infiltration per foot of crack for doors and windows CFM = Ft. of Crack x Infiltration Rate QS = 1.1 x CFM x (T2 – T1) in BTU/HR

21. Add Infiltration Through Open Door • Determine Door Usage • ת = Number of People per Minute • Determine CFM per person (D) CFM = ת x D LEED-NC Credit EQ 5 for providing vestibules.

22. Infiltration by Crack Method • Add CFM from Crack losses to CFM for Open Door losses

23. Mitigate These Losses • How do you reduce or mitigate these losses? (Review)

24. Mitigation Strategies • Pressurization QS = 1.1 x CFM x (T2 – T1) Vs. QS = 1.1 x (CFH/ft of crack x ft of crack)/60 x ΔT You own the variables!

25. Infiltration Variables Review • Wind velocity and direction • Stack effects • Corner rooms • Exhaust fans on or off • Pressure zoning • Frequency of use • Maintenance

26. Stack Effect Review

27. Air Change Method • Often used in residential construction and in large warehouses and similar buildings CFM = A.C.H. x Volume (ft3)/60 or CFM = Volume (ft3)/Frequency (minutes)

28. Qsens =1.1 x CFM x T Air Change Method • Uses same formula for sensible • Equals one room change • Designer will use 0.3 to 2.0 air changes per hour (ACH) • Occupancy • Climatic condition (i.e. winter vs. summer) • Construction (tight or loose) • Least accurate of the three methods

29. Table 2-8

30. Heat Loss Due to Infiltration Infiltration Btu H = (.018) x (ACH) x V x (Ti – To) ACH = air exchanges per hour V = volume Ti = inside temperature To = outside temperature

31. Heat Loss Due to Infiltration OR

32. Heat Loss Due to Infiltration Infiltration Btu H = 1.1 x CFM x (Ti – To) CFM = (ACH x volume) / 60 min per hour

33. Heat Loss Due to Infiltration Infiltration Please Note: For tight construction use 0.5 for ACH. For medium construction use .85 for ACH. For loose construction use 1.3 for ACH. For really bad construction use 2.0 for ACH For the summer months (cooling) use 70% of the winter values.

34. Infiltration & Ventilation

35. Heat Gains Due to Infiltration Latent Load BtuH = 4500 x (air exchanges x (volume) /60) x (W Final – W Initial) (W Final – W Initial) = Difference Ratio Pounds of Moisture per dry air

36. Heat Loss Due to Ventilation Ventilation Btu H = 1.1 x [(Ra x square feet of building ) + (number of people in the building x Rp )] x (Ti – To)

37. Heat Loss Due to Ventilation

38. Heat Loss Due to Ventilation Ventilation Ra = Area Outdoor Air Rate Rp = People Outdoor Air Rate Example: Pharmacy Ra = .18 Rp = 5

39. Heat Loss Due to Ventilation Ventilation Btu H = 1.1 x [ (.18 x 3,632) + (30 x 5)] x 76o = 67,214

40. Ventilation and / or Infiltration