Document 4JzxpnX5a0Z4026zmmK2q0JaQ

American Society of Heating and Ventilating Engineers Guide, I935U A complete study of all of the factors involved in air movement thri building constructions would be very complex. Some of the comp factors are: the variations in wind velocity and direction; the exposures the building with respect to air leakage openings and with respect to adjoining buildings; the variations in outside temperatures as influencin. the chimney effect; the relative area and resistance of openings on tb windward and leeward sides and on the lower floors and on the upp^ floors; the influence of a planned air supply and the related outlet ventsand the variation from the average of individual building units. A study! of infiltration points to the need for care in the obtaining of good buildi ' construction, or unnecessarily, large heat losses will result. AIR LEAKAGE THROUGH WALLS Table l1 gives data on infiltration through brick and frame walls. Tin 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-linn mortar does not exceed one-third the values given. These tests indicate that plastering reduces the leakage by about 96 per cent;.a heavy coato( 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 pier 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. Table 1. Infiltration through Walls Expressed in cubic feet per square foot per hour* Ttpe op Wall Wind Velocitt. Miles peb Hotm IS5 10 2Q 25 30 Chapter 6--Air Leakage Fig. 1. Infiltration through Various Types of Shingle Construction 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. 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. 8Hin. Brick Wall...... 1.75 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 plaster1* 0.03 0.07 0.13 0.18 0.23 0.26 oThe values in this table are 20 per cent less than test values to allow for building up of pressure in room and are based on test data reported in A.S.H.V.E. research papers entitled Air Infiltration Through Variou Types of Brick Wall Construction, and Air Infiltration Through Various Types of Wood Frame Con struction. (See References on pages 128 and 129). bWall construction: Bevel siding painted or cedar shingles, sheathing, building paper, wood lath and 3 coats gypsum plaster. Air Infiltration through Various Types of Brick Wall Construction, by Larson, Kelson and Braat> A.S.H.V.E. Transactions; Vol. 36, 1930). 120 Fig. 2. Infiltration through Single Surface Walls Used in Farm and Other Shelter Buildings 121