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220 CHAPTER 10 1955- Guide#* 'M | * Remedial Measure* Jor Building Construction, by L. V. Teeadale (Report R.171G of U. S. Forest Product* 1kt\ Lab1orMaetotrhyo1d9s4o7)f. Moisture Control and Their Application to Building Construction, by F. B. Rowle. y, Ay B, Algreo and C. E. Lund (University of Minnesota, Engineering Experiment Station Bulletin No. 17). * The Relation of Wall Construction to Moisture Accumulation in Fill-Type Insulation by Henry J. Barre. (Icm State College of Agriculture and Mechanic Arts Agricultural Experiment Station Bulletin No'. 271,1940); Moisture Migration: A Survey of Theory and Existing Knowledge, by-P. F. McDe.rmoti (Refrigerating[ % Engiii>nPeeerrimnge,aAbuilgituysotf1F9a41i,iipi F. i1lm03s). to Moisture, by R. I. Wray and A. R. Van Vorst (Industrial and Engines?', t'nff Chemistry Vol. 25, p. 842, 1933). > " Water Vapor Transmission ofBuilding Materials Using Four Ttifferenl Testing Methods, by R. R. Britton/ and R. C. Reichel, (17. S. Housing and Home Finance Agency Technical Bulletin No. 12, January 1950). r "Water-Vapor Permeability of Building Papers and Other Sheet Materials, by E. R. Bell, M. G. Sefdl,-',T' and N. T. Krueger (A.S.H.V.E. Transactions, Vol. 57, 1951, p. 287). u Value from unpublished tests of Pennsyhxinia Stale College Engineering Experiment Station. i* Condensation Control in Dwelling Constructions (U. S. Housing and Home Finance Agency, 1949). BIBLIOGRAPHY Moisture Condensation in Building Walls, by H. W. Wooley (National Bureau ofStandards, ReportBMS63' DecCeomnbdeern1s4a,t1io9n40o)f. Moisture and Its Relation to Building C,onstruction and Operation, by F. B. Howls,r;//t A. B. Algren and C. E. Lund (A.S.H.VJ2. Transactions, Vol. 45, 1939, p. 231), / A Theory Covering the Transfer cl Vapor Through Materials, by F, B. Rowley (A.S.H.V.E, Transac-H nous, Vol. 45, 1939, p. 545). ^ Simultaneous Heat and Vapor Transfer Characteristics of an Insulating Material*, by F. G. Hechle.t: E. R. McLaughlin and E. R. Queer (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 505). ~L Comparative Resistance to Vapor Transmission of Various Building Materials, by L. V. Teesdale-1' (A.SP.eHrm.Vis.Esi.bTlerRaneslaatcivteionHsu,mViodli.ti4e9s, 1in943H, upm. 1id24if)i.ed Buildings, by Paul D. Close (A.S.H.V.E. Journal* Section, Healing, Piping and Air Condilioning, December, 1939, p. 766). Condensation Within Walb, by P. B. Rowley, A. B. Algren and C. E. Lund (A.S.H.V.E. Transactions,.. Vol.P4h4y,s1ic9s38o, fpC. o9n5)d.ensation in Buildings, by J. D. Babbitt (Bulletin No. 2, National Research Council, of[. CanSWatdouaod)di.eHsaonfdthboeoPkh(yFsoicreasltPProropdeurctitessLoafbHoarartdoerny,edUPniotertdlaSntdatCesemDeepnat rPtmasetentboyfTA.gCri.cuPlotuwreer,s1a9n4d0)T. . L.Browtf? yard (Journal, American Concrete Institute, Vol. 18, No. 8, April 1947, p. 933). .> Experiments on the Freezing of Certain Building Materials by W. N. Thomas (Building Research, Tech- -, nical Paper No. 17, H.M.S.O., London, 1938). V Moisture Migration in a Closed, Guarded Hot Plate by i. A. Paxton and N. B. Hutcheon (A.S.H.V.E. TraMnosvaecmtioennst ,ofvoWl.a5te8r, 1in95S2,opil, D30u1e).to a Temperature Gradient by C. G. Gurr, T. J. Marshall, and 5. T/ Hutton (&otf Science, Vol. 74, No. 5, November, 1952, p. 335). V Fundamental Similarities Between Electro-osmotic and Thermo-osmotic Phenomena by H. F. Winter^ torn (Proceeding* t7th Annual Meeting, Highway Research Board, Vol. 27, 1947, p. 443). ` Performance of Desiccants in the Dry Pan Test for Water Vapor Permeance of Membranes by S. C. Chang ? and N. B. Hutcheon (Canadian Journal of Technology, 31, September, 1953, p. 175-192.) Fundamental Considerations in the Design of Exterior Walls for Buildings by N. B. Hutcheon (Technicd Report No. 13, D.B.R., National Research Council of Canada, 1953). *9 CHAPTER U INFILTRATION AND VENTILATION Causes of Infiltration, Infiltration Due to Wind Pressure, Infiltration Due to Temperature. Difference, Sealing of Vertical Openings, Infiltration Meas urement, Natural Ventilation, Wind Forces, Temperature Difference Forces, Heat Removal, Effect of Unequal Openings, Combined Wind and Temperature Forces, Types of Openings, General Ventilation Rules, Ventilation of Animal Shelters, Garage Ventilation Infiltration is the air leakage through cracks and interstices, around windows and doors, and through floors and walls. Its magnitude depends on the structural design, workmanship, and condition of the building. The rate of infiltration cannot be controlled by the inhabitants of the building to any considerable extent. Natural ventilation is the controlled displace ment of air through openings, such as windows, doors and ventilators as well as through combustion heating devices. CAUSES OF INFILTRATION The air leakage which takes place through various apertures in buildings must be estimated in heating and cooling calculations and enough heating or cooling capacity provided to offset the heat lost or gained by the air leakage. The rate of air flow into and out of a building depends on the magnitude of the pressure difference between the inside and outside of the structure and on the resistances presented to this pressure difference. The pressure difference exerted on the building walls by the air may be caused either by wind or by a difference in density of the air inside and outside the building. The effect of the wind depends on the interrelation of the speed and direction of the wind and the exposure of the building. The effect of the difference in the density of the air depends bn the magnitude of the inside-outside temperature difference, the height of the rooms, the shape of the openings, and their elevation in the room or building. The effect of the difference in density is often referred to as the chimney or stack effect. The pattern of air flow through any part of the structure de pends on both the pressure difference and the openings. In general, when the pressure difference is the result of wind pressure, air will enter the pudding through openings in the windward walls and leave through open ings in the leeward walls or through ventilating ducts in the roof. When the pressure difference is caused by the inside-outside temperature differ ence the flow will be along the path of least resistance from inlets at lower .'els to outlets at higher levels in a heated building or in the opposite direction for an air-conditioned building. . An exact estimate of the amount of infiltration under design conditions Is difficult to make. The complicating factors include (1) variations ln building construction, particularly as to width of crack or size of openings through which air leakage takes place; (2) the variations in "dud velocity and direction; (3) the exposure of the building with respect 411 leakage openings, and with respect to adjoining buildings; (4) the 221