Date: Fri, 03 Apr 1998 16:49:29 -0800
Reply-To: tphillip@arb.ca.gov
Sender: owner-greenbuilding@crest.org
Terrry: you asked about moisture models. I recently did a quick reviewof moisture IAQ impact assessment. Here is info on a model at thestate-of-the-art end of the spectrum:
The TENWOLDE model can estimate the quantities and frequencies ofsurface condensation in homes. It was used by Canada Mortgage andHousing in their Wallaceburg Phase II study of moldy homes. Condensation or standing water should be eliminated from homes.
(TenWolde, A., 1994. FPLRH, Version 6 model, modified 1994, PC based. Forest Product Laboratory, U.S. Department of Ag. Forest Service. Program described in: "Ventilation, humidity, condensation inmanufactured houses during winter," ASHRAE Transactions, 1994, vol. 100;and "A mathematical model for indoor humidity in houses during winter,"Proc. Symposium on Air Infiltration, Ventilation and Moisture Transfer,BTEC, Washington, DC.)
Based on Lstiburek's recommended humidity goals, the model should use atarget level of 25-35% RH in heating climates, and 35-45% RH in mixedheating and cooling climates, at 75 degrees F in order to limit relativehumidities at surfaces to 70% RH, thereby preventing mold growth. Condensation and standing water are not acceptable conditions inbuildings occupied by humans.
(Lstiburek, J.W., 1994. Mold, Moisture, & Indoor Air Quality. A Guidefor Designers, Builders, and Building Owners. Building ScienceCorporation, Chestnut Hill, MA.)
Parts of a building can have condensation or high RH, e.g., cold walls,carpets on slab foundations, even though the average RH is not thathigh. Several homes in the 1993 Synertech study for NYSERDA hadhumidity levels near or above 60% RH, and some had obvious moistureproblems and noticeable health symptoms.
(Strunk, P.R., 1993. Air Leakage and the Effects of MechanicalVentilation: Measurements in Fifty Newer Homes in New York State. SYNTR 93-516. Syracuse, NY. Prepared for NYSERDA, Albany, NY.).
Hope this helps, in case you haven't already run across this or talkedwith Jim White, CMHC. Sebastian Moffet at Sheltair (Vancouver, BC)might also be a good contact.