Document 8OBKqqNzgZ6KGe4m2ob5Qxj5d

ISO. __________________CHAPTER 8. 1948 Guide -Infiltration Through Walls Data on infiltration through brick and frame walls are given in Table 1 *. The brick walls listed in this table are walls which show poor workman ship and which are constructed of porous brick and lime mortar. For good workmanship, the leakage through hard brick walls with cementlime unortar does not exceed one-third the values given. These tests indicate that plastering reduces the leakage by about 96 per cent; a heavy coat of cold water paint, 50 per cent; and 3 coats of oil paint carefully applied, 28 per cent. The infiltration through walls ranges from 6 to. 25 per cent of that through windows and doors in a 10-story office building, with imperfect sealing of plaster at the baseboards of the rooms. With perfect sealing the range is from 0.5 to 2.7 per cent or a practically negligible quantity, which indicates the importance of good workmanship in proper sealing at the baseboard. It will be noted from Table 1, that the infiltration through properly plastered walls can be .neglected. The value of building paper when applied between sheathing and Table 1. Infiltration Through Walls3 Expressed in cubic feet per square foot per hour Type of Wall Wind Velocity, Miles per Hour 5 10 15 20 . 25 30 8)4 in. Brick Wallb,, JPlain......... 2 J Plasteredc___ 0.02 40.04 8 12 19 23 0.07 0.11 0.16 0.24 f Plain________ 13 in. Brick Wallb_ . 7 Plastered3___ (.Plastered1*___ 1 0.01 0.03 4 0.01 0.10 7 0.03 0.21 12 0.04 0.36 16 0.07 0.53 21 0.10 0.72 Frame Wall, with lath and plaster3.. 0.03 0.07 0.13 0.18 0.23 0.26 *Tbe values given in this table are 20 per cent less than test values to allow for building ur of pressure in rooms and are based on test data reported in the papers listed in chapter footnotes. ^Constructed of porous brick and lime mortar--workmanship poor. Two coats prepared gypsum plaster on brick. dFurring, lath, and two coats prepared gypsum plaster on brick. Wall construction: Bevel siding painted or cedar shingles, sheathing, building paper, wood lath and three coats gypsum plaster. .shingles is indicated by Fig. 1, which represents the effect on outside construction only, without lath and plaster.. The effectiveness of plaster properly applied is no justification for the use of low grade building paper or of the poor construction of the wall containing it. Not only is it difficult to secure and maintain the full effectiveness of the plaster but also it is highly desirable to have two points of high resistance to air flow with an air space between them. The infiltration indicated in Fig. 1 is that determined in the laboratory and should be multiplied by the factor 0.80 to give proper working values. Window and Door Leakage There are two methods of estimating air leakage through window and door cracks, namely, (1) the crack method and (2) the air change method. The crack method is generally regarded as being more accurate than the purely arbitrary air change method, provided the variables such as crack width and clearance, can be properly evaluated. Air Leakage 151 Crack Method The crack method is based on known air leakage factors for various types of windows and widths of crack and clearance. The wind velocity and length of crack are alsQ considered when the crack method is employed. The amount of infiltration for various types of windows is given in Table 2 !. The fit of double-hung wood windows is determined by crack and clearance. Crack thickness is equivalent to one-half the difference between the inside window frame dimension and the outside sash width. The difference between the width of the window frame guide and the sash thickness is considered as the clearance; The length of the perimeter opening or crack for a double-hung window is equal to three times the width plus two times the height, or in other.words, it is the outer sash Rerimeter length plus the meeting rail length. Not all the window crack in any given room is necessarily used in estimating the infiltration heat Fig. 1. Infiltration Through Various Types of Shingle Construction loss by the crack method. The length of crack to be selected in any given case depends on the number of exposed sides as explained in Chapter;14i Values of leakage shown in Table 2 for the average double-hung wood window were determined by using,, on nine windows tested in the labo ratory, the average measured crack and clearance of a large number of windows found in a field survey. In addition, the table gives figures for a poorly fitted window. All of the figures for double-hung wood windows are for the unlocked condition. Just how a window is closed, or fits when it is closed, has considerable influence on the leakage. The leakage will be high if the sash are short, if the meeting rail members are warped, or if the frame and sash are not fitted squarely to each other. It is possible to have a window with approximately the average crack and clearance that will have a leakage at least double that of the figures shown. Values for the average double-hung wood window in Table 2 are considered to be easily obtainable figures provided the workmanship on the window is good. Should it be known that the windows under consideration are poorly fitted, the larger leakage values should be used. Locking a window