Humidity levels in buildings with variable moisture sources,ventilation rates and environmental conditions

Abstract

The paper outlines a derivation of a fundamental equation of humidity for any enclosed space or set of spaces exchanging air with each other and with the external environment. The solution enables the humidity levels to be predicted for any arbitrarily changing set of conditions. A number of simpler solutions for room humidity levels are given and discussed. A program to allow users to evaluate different hypothetical effects in the general case easily is cited. A brief discussion, using some specific examples, is made of the various factors contributing to the resultant room humidity and the effectiveness of ventilation. The analytical form of the solution given to the equations allows a user to assemble a model of the humidity response of a building to any degree of complexity using simple calculations.

Get full access to this article

View all access options for this article.

References

Approved document to the Building Regulations Part F ( London: HMSO) (1995)

Cibse Guide Section A1 Environmental criteria for design (London:Chartered Institution of Building Services Engineers) (1986)

Loudon A.G. and Hendry W.L. Ventilation and condensation control in Condensation in Buildings p 44 ed. Croome D J and Sherratt A F C ( Applied Science Publishers) ( 1972)

Cibse Guide Sections C1 and C2 Propenies of Humid Air, Water and Steam (London: Chartered Institution of Building Services Engineers) ( 1975)

Morse P.M. and Feshbach H. Methods of Theorerical Physics Part 1 (McGraw-Hill ) (1953) pp 527

Jones W.P. Air Conditioning Engineering 2nd edn p488 (London : Edward Arnold)

McIntosh G.D. , Bragg G.M. and Siurna D.L. Transient Model of Indoor Air Quality Trans. Indoor Air Quality in cold Climates ed. Walkingshaw D S (1985 )

Sandberg M.

Ventilation Efficiency as a Guide to Design

ASHRAE Trans. 89 455-479

Wadden R.A. and Scheff P.A. Air Quality Models in Indoor Air Pollution ch. 6 p105

10.

BS 5250:1989 Code of practice for control of condensation in buildings (London: British Standards Institution) (1989)

11.

Ralston A.A. First course in numerical analysis p118 (New York: McGraw-Hill) ( 1965)

12.

Taylor B.E. Visual BASIC listing suitable for use with Microsoft Excel 5 spreadsheet to evaluate the furtdamental equation of humidity (Garston , UK: British Board of Agrement) ( 1997)

13.

Person R. Using Excel 5.0 for Windows (Que Corporation)