Document om4EKje1Bk7BNnK8mOD26eKDr

Heating Ventilating Air Conditioning Guide 1939 A complete study of all of the factors involved in air movement through building constructions would be very complex. Some of the complicating factors are: the variations in wind velocity and direction; the exposure of the building with respect to air leakage openings and with respect to adjoining buildings; the variations in outside temperatures as influencing the chimney effect; the relative area and resistance of openings on the windward and leeward sides and on the lower floors and on the upper floors; the influence of a planned air supply and the related outlet vents; and the variation from the average of individual building units. A study of infiltration points to the need for care in the obtaining of good building construction, or unnecessarily large heat losses will result. INFILTRATION THROUGH WALLS Table 1 gives data on infiltration through brick and frame walls. The brick walls listed in this table are walls which show poor workmanship and which are constructed of porous brick and lime mortar. For good workmanship, the leakage through hard brick walls with cement-lime mortar 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 in filtration through properly plastered walls can be neglected. ' The value of building paper when applied between sheathing and 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 Table 1. Infiltration through Walls3 Expressed in cubic feet per square foot per hour Ttpb op Wall 5\ Worn Velocity, Miles per Hour 10 15 20 25 30 *" Brick Wall {plastered"" 1.7S 4.20 7.85 12.2 18.6 22.9 .0.017 0.037 0.066 0.107 0.161 0.236 13 in. Brick Wall.------- 1.44 3.92 7.48 11.6 16.3 21.2 0.005 0.013 0.025 0.043 0.067 0.097 Frame Wall, with lath and piaster1*. 0.03 0.07 0.13 0.18 0.23 0.26 The values given in this-table are 20 per cent less than test values to allow for building up of pressure in rooms and are based on test-data reported in the papers listed at the end of this chapter. bWall construction: Bevel siding painted or cedar shingles, sheathing, building paper, wood lath and 3 coats gypsum plaster. 120 Chapter 6. Air Leakage Fig. 1. Infiltration through Various Types of Shingle Construction 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 amount of infiltration that may be expected through single walls used in farm and other shelter buildings, is shown in Fig. 2. The infil tration indicated in Figs. 1 and 2 is that determined in the laboratory and should be multiplied by the factor 0.80 to give proper working values. Fig. 2. Infiltration through Single Surface Walls Used in Farm and Other Shelter Buildings 121