By Jeffrey C. May –
You may expect a new property or a recently renovated property to be clean, and the air to be free of contaminants. That’s often far from the case, however. I’ve seen newly constructed and renovated homes that had mold and other indoor air quality problems.
Mold Growth
In one high-end construction project at a waterfront lot, the house had been under construction for over a year. I was at the house in the early spring. The weather was hazy and cool; it had rained the day before. The house was still not weather tight; door openings and many window openings were plugged with plywood and plastic, and all the wood framing indoors was still exposed. Workers were sawing wood in the basement, and since the different levels of the house were still open to each other, biodegradable sawdust had spread to all levels.
Certain species of mold – including species of the highly friable and allergenic Aspergillus mold – can grow when the relative humidity (RH) is over 80%. The RH in the house was 85%. In addition, the moisture content of the wood was over 20% – high enough for mold growth to occur. My tape samples from multiple surfaces contained minor mold growth that was not visible to the naked eye.
Surfaces had to be cleaned and sealed, and the house made weather tight. The general contractor also had to have some sort of dust collection or ventilation system in place, and insist that workers saw wood only in those areas, or do this work outdoors.
These weren’t the only indoor-air-quality issues in the house. In order to keep the carpenters comfortable, the heating system had been run in the winter, and the cooling system had been run the summer before. The filters in the HVAC system were of high quality, but were sitting next to the air handlers rather than being installed within the filter slots. For some reason, the Developer had removed the filters in an effort to keep them clean. In so doing, he had paved the way for dust and mold contamination within the entire HVAC system.
Mechanical systems (for heating and/or cooling) can be contaminated with mold growth before a new owner even takes possession, as was the case with this property. All the air handlers and ducts (where metal) had to be professionally cleaned.
Flexible ducts (made of plastic with spiral-wire “skeletons”), where accessible, had to be replaced, because such ducts cannot be easily cleaned. And I recommended that any “panned bays” (“ducts” made by putting metal sheeting at the bottom between two joists, so the “ducts” consists of metal at the bottom and wood at the sides and top) be opened and lined with smooth material.
Read the full article in the January issue of Healthy Indoors Magazine HERE
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