Why Mold and Why Now?
We are especially interested in one presenter’s comments during the public ASHRAE session. Joseph Lstiburek, Ph.D., P.Eng., of Building Science Corp., Westford, Mass., has entitled his presentation, “What Happened? Why Mold and Why Now?”
As quoted elsewhere in this issue, Lstiburek says that “mold has been around a long time; what is the big deal now? We’ve always had roof leaks, plumbing leaks, window leaks, and rain during construction. Buildings don’t dry as quickly as they used to. The materials we build out of are much more moisture sensitive. They can’t take the moisture ‘events’ the way the old materials did.”
Lstiburek is a forensic engineer who investigates building failures and is internationally recognized as an authority on moisture-related building problems and indoor air quality.
Despite, or in addition to, these impressive credentials, Lstiburek is also the source of much common sense wisdom on matters such as moisture and mold. Consider, for example, “Joe’s Top Ten Rules of Wood Durability,” (It is also telling, and very non-engineering of him, that “Joe” has thirteen items on his top 10 list.) Here are the rules:
- Buildings should be suited to their environment.
- The laws of physics must be followed.
- Three things destroy materials in general and in particular: water, heat and ultraviolet radiation.
- Of these three, water is the most important by an order of magnitude.
- Critters love wet materials.
- No wet materials, no critters.
- Things get wet let them dry.
- Things get wet from the inside, the outside, and they start out wet.
- When the rate of wetting exceeds the rate of drying, accumulation occurs. When the quantity of accumulated moisture exceeds the storage capacity of the material, problems occur.
- The storage capacity of a material depends on time and temperature.
- The drying potential of an assembly decreases with the level of insulation and increases with the rate of airflow.
- As such, energy conservation has the potential to destroy more buildings than architects.
- Don’t let biologists and wood scientists design real buildings.