Infiltration
Infiltration is from combined effect of buoyancy and wind. Infiltration rate: O
Where Q = infiltration rate (L/s)
L = effective leakage area (cm2)
Cs = stack coefficient (L2 s’2 cm’4 K’1)
AT = average indoor-outdoor temperature difference (K)
Cw = wind coefficient (L2 s’4 cm’4 K’1 m’2)
V = average wind speed measured at local weather station (m/s)
|
Table 7 Local Shielding Classes Description |
|
Table 5 Example of Calculation of Building Effective Air Leakage Area Based on Component Leakage Areas |
|
Class |
|
Size or x Al Description Number per unit |
|
1 No obstructions or local shielding 2 Light local shielding; few obstructions, few trees, or small shed 3 Moderate local shielding; some obstructions within two house heights, thick hedge, solid fence, or one neighboring house 4 Heavy shielding; obstructions around most of perimeter, buildings or trees within 10 m in most directions; typical suburban shielding 5 Very heavy shielding; large obstructions surrounding perimeter within two house heights; typical downtown shielding |
|
2 Cm |
|
Component |
|
4.0 cm2/m 0.5 cm2 ea 4.0 cm2/m2 1.7 crrr/m2 7.7 cm2/m2 1.7 cm2/m2 350 cm2 ea 6.0 cm2 ea 144 cm2 ea |
|
173 10 75 54 350 42 144 |
|
Uncaulked Sliding Single Without damper Pipes Ducts untaped. |
|
43.2 m 20 13.1m2 13.1m2 5.7 m2 5.7 m2 1 7 1 |
|
Sills Electrical outlets Windows Framing Exterior doors Framing Fireplace Penetrations Heating ducts |
|
|
Table 8 Wind Coefficient C*, |
|
,. … House Height (Stories) |
 |
|
|
O
Air change rate = 284 / 340 = 0.84 ACH.
|
0.1 ACH (air change rate per hour) 0.5 ACH 1 ACH 2 ACH 3 ACH |
Extremely low low normal high
Extremely high Crack method:
Q = A C Apn
Where A = effective leakage area of cracks (m2)
C = flow coefficient
Ap = pressure difference between outdoor and indoor (Pa)
Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning