Chapter 6B: INFILTRATION CALCULATION Agami Reddy (rev Dec 2017) Component models for air infiltration - residential doors and windows, - closed swinging doors - opening of doors - curtain wall 2. Empirical methods - Air change method (for residences and small commercial) 3. Basic LBNL model for one-zone buildings Multi-zone network models Natural ventilation due to opening and closing of windows Natural ventilation through large openings Measuring air infiltration HCB-3: Chap 6B Infiltration Calculation

Component Models for Air Infiltration Previous set of slides allowed pressure difference across building envelopes to be determined. Now, let us look at how infiltration can be determined. Leakage Thru identifiable Components: Based on field tests on Actual Buildings: Residential windows and doors Commercial swinging doors when closed Opening of commercial swinging doors 2) Background leakage Curtain walls for commercial buildings Use Table 6.2 HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Background Leakage 6.20 HCB-3: Chap 6B Infiltration Calculation

Identifiable Components: Residential Windows and doors Figure 6.15 Window and residential-type door air infiltration per perimeter length lp. The curves correspond to Equation 6.21, with n = 0.65 and coefficient k [(L/s · Pa0.5), (ft3/min ∙ inWG0.65)] according to construction type, as shown in the following table: HCB-3: Chap 6B Infiltration Calculation

Infiltration for commercial-type swinging doors when CLOSED because gaps are larger Figure 6.16 Infiltration through closed swinging door cracks, per perimeter length lp. The curves correspond to Equation 6.21, with n = 0.5 and coefficient k [(L/s · Pa0.5), (ft3/min ∙ inWG0.5)]. HCB-3: Chap 6B Infiltration Calculation

Infiltration through opening of doors due to traffic Figure 6.17 Figure 6.17 Infiltration due to door openings as a function of traffic rate: (a) infiltration (with n = 0.5) and (b) coefficient C [(L/s · Pa0.5), (ft3/min ∙ inWG0.5)]. Similar plots are available for revolving doors and automatic doors HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Curtain wall Figure 6.18 Infiltration per area of curtain wall for one room or one floor. The curves correspond to Equation 6.23, with coefficient K [(L/s · m2 · Pa0.65), (ft3/min · ft2 · inWG0.65)] according to construction type. HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation due to windows + door perimeter + door opening + curtain wall HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Empirical Methods Air change method: for residences and small commercial assumes that a portion of the air in the building is replaced with outdoor air which must be heated/cooled. Number of air changes per hour (ACH): 1 ACH is equal to a flow rate equal to one volume of the house per hour Range of ACH: 0.5 - 1.5 tight loose Air infiltration volume = (ACH) x (room volume) / 60 min/hr Tables in next slide allow determination of ACH for summer and winter conditions HCB-3: Chap 6B Infiltration Calculation

Method used by some professionals because of its simplicity HCB-3: Chap 6B Infiltration Calculation

Basic LBNL Model for Air leakage Applicable for 1-zone small buildings WITHOUT mechanical ventilation: 6.25 Effective leakage area (ELA) is the equivalent amount of free open area of an orifice that allows the same volume of air by infiltration as the actual building (Eqn can be used for specific days as well as seasonal averages depending on how the temperatures and wind velocity values are selected) HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Table 6.2 HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Figure 6.19 Sketch of the building used for many of the examples in this chapter. HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation 6.25 HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Multizone Models It is important to accurately predict inter- zonal flow interactions for: (i) larger buildings or for buildings with multiple thermal zones to predict envelope leakage over specific portions of bldg Set up and solve a set of simultaneous non-linear equations for each flow element (doors, windows, assuming fully mixed compartments Figure 6.20 Illustration of multizone flow paths HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Multizone Models Figure 6.21 Flow networks for a multizone building: (a) leakage paths in series and (b) leakage paths in parallel HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Opening of Windows and Doors Figure 6.22 Measured ventilation rates, as a function of wind speed, in a two-story house with windows open on lower floor - Difficult to predict accurately - Opening of windows led to large changes in ACH ( 1 to 20 per hr) HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Natural Ventilation Air Flow through Large Openings due to wind: Eq. 6.28 If the openings are not of the same size, the correction curve should be used: Figure 6.24 Increase in flow caused by excess area of one opening over the other HCB-3: Chap 6B Infiltration Calculation

Lab Testing for Airtightness of a Component Controlled tests are done in the lab without the influence of climatic parameters. A static pressure difference (about 200 Pa) is created across the test specimen from which the ELA can be deduced. Often results are presented in terms of - Flow per hour per area - Flow per hour per unit crack length Figure 6.26 Airtightness test arrangement of a building component HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Blower Door Tests Blower door tests are done to estimate aggregate envelope leakage and to locate and fix leaks: Device consists of a door-insert with rubber edge. Variable speed fan and measurements for flow and pressure difference Tests conducted till fairly high pressures (about 50 Pa) in 10 Pa incremental steps Done in smaller buildings Tracer gas tests used for larger bldgs Figure 6.25 Photo of a blower door test rig HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Presentation and Analysis of Test Data of Blower Door Tests HCB-3: Chap 6B Infiltration Calculation

HCB-3: Chap 6B Infiltration Calculation Outcomes Be able to apply models for estimating leakage through various types of envelope components Understanding of the simple air change method Be able to use the LBNL model to solve simple problems Familiarity of the ELA concept and lookup tables Understanding scope and analysis approach of multi-zone modeling methods Understanding how opening windows and doors can lead to large variations in natural ventilation Familiarity of how to deduce natural ventilation flow thru large openings Familiarity with how components are tested in the lab Understanding of the working principle of the blower door test and how to deduce whole house ELA HCB-3: Chap 6B Infiltration Calculation