I receive regular calls regarding water intrusion and mold growth in buildings; you cannot have the latter without the former (mold needs water to grow). However, especially this wet La Nina year, I received a number of calls from residents or tenants in older homes where the problem is condensation - not one of the normal water intrusion issues I normally inspect. Typically, this occurs in older homes with uninsulated walls, single-pane wood or aluminium-framed windows with a single source of heat (normally natural gas) in a central location of the dwelling. Normally, the mold is located on exterior walls behind furniture that is close to the wall. Sound familiar?
The last one inspected was a classic example: Eleven-hundred square feet, 5 occupants, mold in two bedrooms off the hallway, single source of gas heat in the hallway, mold on exterior walls behind or next to furniture against exterior walls. This mold is typically cladosporium species, normally found around windows and in bathroom tubs and showers. It is the most common and easily dispersed spore in our atmosphere and requires a relatively high level of water activity to grow.
Here are the important environmental factors in this particular investigation as measured by a thermal hygrometer that calculates the relative humidity, temperature, dew point and specific humidity or Grains Per Pound of air. I will spare you information on the GPP since the entire story is contained in the first three measurements as indicated below:
Bedroom #1: Temperature - 67.5 F, Relative Humidity - 69.6%, Dew Point Temprature - 56.7 F
Bedroom #2: Temperature - 67.2 F, Relative Humidity - 67%, Dew Point Temprature - 56 F
Bathroom: Temperature - 68.3 F, Relative Humidity - 69.6%, Dew Point Temprature - 58 F
The bedroom doors are closed at night and with the cold temperatures we have been experiencing, condensation was occurring where there was little or no air circulation - where there was furniture against the exterior walls. This problem can be further exacerbated by moisture in the crawl space of the structure - a very common problem here in River City (none in this investigation).
The solution is rather straight forward: clean the small amount of mold off the wall with detergent and water (bleach is not necessary!) and leave 4-6" of space between the furniture and the exterior walls. I further recommended that they leave the doors open (just a "crack" will do) and replace the light fixtures with ceiling fans/light fixtures and run the ceiling fans in the appropriate (winter/summer) direction. Air circulation and air space between the walls and furniture is a simple and easy fix. More importantly to both the tenant and the landlord - the accumulation of knowledge of why it happened and how to prevent it in the future.
Contact me if you would like further information on this or other types of water intrusion issues - I'm glad to provide helpful information upon request.
Charles E. Cassani, CR
SOS Consulting
email: ccassani@soshhs.com
phone: (916) 997-3755
