Healthy Living Spaces


Mold - Why the Concern Now?

Mold has been around since the beginning of time and it has been known that mold is unhealthy. The bible talks about mold and what to do if a house has mold:

And the Lord spoke unto Moses…

And he shall look on the plague, and, behold, if the plague be in the walls of the house with hollow streaks, greenish or reddish…then the priest shall shut up the house seven days. And the priest shall come again the seventh day, and shall look; and, behold, if the plague be spread in the walls of the house. Then the priest shall command that they take out the stones in which the plague is, and cast them into an unclean place without the city.²

Since mold has been around forever, why does it appear that mold has only recently become a concern?

Media Frenzy

Stachybotrys, or “black mold”, became front page news in 1994 when a number of babies in Cleveland, Ohio mysteriously died from bleeding in the lungs. Forty-five babies under six months old were affected; sixteen died. The majority of the babies lived in homes that were water damaged as the result of a recent flood. Since Stachybotrys was identified growing in the homes the infants lived, the Center for Disease Control blamed Stachybotrys for the infant deaths. According to many experts however, the link between Stachybotrys and the infant deaths has not been conclusively proved³.

Modern Building Materials

A significant reason for more mold problems today may be that modern building materials are easier for mold to digest. Stachybotrys, black mold, loves the paper backing of drywall (also known as gypsum board or sheetrock). The interior walls in modern homes and offices are constructed out of drywall. Sometimes buildings are built with sheet rock on the exterior walls also to save money over using plywood. Often when back mold is visible on drywall, it is Stachybotrys.

Drywall gets soggy like a wet towel as soon as it gets wet. Mold will grow immediately on wet drywall. Traditional plaster walls are less prone to mold growth than drywall and quite often mold growth is not fond on the back of water damaged plaster. Unfortunately, newer homes with plaster walls often have the plaster installed on top of drywall.

Another modern building material prone to mold growth is plywood or particle board. Like drywall, these can’t absorb much water before the moisture is available for mold growth.

Solid wood can soak up and store moisture. To a certain point, solid wood can store water and if allowed to dry out before exceeding its storage capacity, will not grow mold. With plywood and drywall being the standard building materials today, there is an increase in the potential for mold problems. Of course mold needs water to grow. Without poor design and faulty workmanship there can be no moisture intrusion and thus no mold growth.

A new product recently came on the market that has a fiberglass based backing instead of paper. Consultants hired to test the product could not get mold to grow on it in Florida over a two month period. A 4x4 panel cost about $4US dollars more than the conventional paper backed panels. This would add approximately $200-300 to the total cost of construction for an average size residential home. Because it cost more Home-Depot, couldn’t sell it, had to mark it down to clearance prices, and has since discontinued it.

Lack of Ventilation

A likely candidate for the increase in mold in recent times is modern buildings are built air-tight to save money on heating bills. As a result when things get wet they can’t dry out fast enough and mold grows. In the old days houses leaked and allowed for an abundant amount of natural ventilation which aided in drying. Fifty years ago commercial building ventilation rates called for 15 cubic feet per minute of outside air per person. In 1973, as a result of the oil embargo, that rate was reduced to only 5 cfm⁴. Now it seems it’s a fad when building houses to cover them with house wrap before putting on the exterior finish. House wrap is a white, Gortex-like material similar to what’s used in some mailing envelopes. It makes the building air-tight.

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Revised: July 05, 2017.
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