Title: Occurrence of mold in a two-story wood-frame house operated at design indoor humidity levels
Author: Clausen, Carol A.; Glaeser, Jessie A.; Glass, Samuel V.; Carll, Charles
Source: General Technical Report FPL-GTR-186. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 12 pages.
Mold growth was observed in limited areas in a two-story contemporary wood-frame house during the seventh heating season of operation at or near design indoor humidity levels. The house was in a cold climate (Madison, Wisconsin). Humidity levels were estimated as being exceeded in one of 10 homes at this location. Moderate amounts of window condensation were observed during each of the seven heating seasons. Areas of observed mold growth were limited to the lower extremities of windows (near the lower edge of glass panes) and the edges of lower panels of a wood panel entry door that was not equipped with a storm door. Mold growth was also present in sprayed-on cellulose insulation in close proximity to the rim joist (board) in the basement, although this mold was not visible unless the insulation was disturbed and was probably present during previous heating seasons. Mold from these locations was cultured, isolated, and identified morphologically or by DNA sequence. Seven genera of common ascomycetes and deuteromycetes were detected, all of which are commonly associated with indoor air. Penicillium was the most common genus, with at least six different species. The greatest variety of genera (five) occurred in samples taken from interior wood millwork (the edges of panels in the entry door and from a wood window sash). Only two genera were found in a sample taken from the interface between the rim joist board and cellulose insulation. Total spore counts taken in April revealed that on the first and second stories, mold spores were less prevalent than in outdoor air but that mold spores were more prevalent in the basement than in outdoor air.
Keywords: Wooden-frame houses, health aspects, molds, wooden buildings, indoor air pollution, spores, indoor air quality, relative humidity, humidity, condensation
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Clausen, Carol A.; Glaeser, Jessie A.; Glass, Samuel V.; Carll, Charles 2009. Occurrence of mold in a two-story wood-frame house operated at design indoor humidity levels. Gen. Tech. Rept. FPL-GTR-186. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 12 p.
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