In a recent blog posting I described the WUFI Moisture Migration software and what it does for looking at long term conditions of moisture within a construction. Moisture is to be expected, but at certain levels and conditions it can become a problem. Predicting if the conditions will exist to promote mold growth in a construction has been made easier with the development of a WUFI feature called WUFI BIO.
WUFI BIO looks at the moisture levels, the class of materials used, and the temperature conditions to predict if the circumstances for mold will persist for a period that would allow mold growth. Until recently WUFI BIO could only predict the opportunity for mold growth on the interior surface of a wall. Now the potential for looking at different places within a construction exists, giving designers and architects yet one more way to test their design prior to the start of construction.
Why is this so important? Water can cause a tremendous amount of destruction within a construction if it were to be present in enough quantity and at certain temperatures. A lot of water in freezing conditions can cause damage from swelling when the water turns into ice but not mold growth since mold is generally dormant in temperatures below freezing. The presence of moisture above freezing can cause fungal growth in wood that will in turn become dry rot, or it can cause mold growth on other building products, such as paper faced sheet rock or wallpaper. Mold is more than just unsightly, it can also be a serious health concern.
It makes sense to design a construction to be as dry as possible so that water does not have the opportunity to wreak havoc, but sometimes the water accumulation is not simply standing water, like flood damage, or puddled water from a heavy rain, it can also be high moisture levels from materials and methods that do not allow the proper migration of moisture through its components. Using WUFI to see how the moisture will move within a construction and then running those results through WUFI BIO can take those results to another level – answering the question “Do the conditions exist for mold to grow?” It’s better to know before construction starts that there is a potential problem than after someone has lived there and been exposed to a problem.
Sometimes it is the manner in which a construction is used that was not anticipated that can cause a problem. Perhaps the original owner of a house, a single person accustomed to taking quick showers sold the house to a family of 5 that each take long, steamy showers every day in the only bathroom of the house whose exterior wall happens to be north facing, with no sun, and gets a lot of driving rain. That exterior wall will have water coming at it from both the inside and outside. While it is hard to predict the way a construction will be used in the future, there are options within WUFI to take some of these circumstances into consideration now. If you are designing a 3 bedroom house for 1 guy, test to see what would happen if the water use increased should additional people live there.
The WUFI instructors in the classes I took also recommended placing a small leak within your construction test cases to see how it would fair under less than favorable conditions. While it is impossible to predict all manner of scenarios that could exist that would allow moisture intrusion into a construction, it is reasonable to assume that something will happen to allow a leak at some point. If your design is so close to already being a problem that a minor leak allows major damage, it is best to re-examine your design before construction starts.
One thing to understand about WUFI BIO – while it is very technical in its approach to looking at the potential for mold to form, the results do not necessarily mean mold will form, just that the simulations have found that the potential exists. Why is this? The models are based on historical information. There is no way to know that next year will be the wettest on record with temperatures hovering for months in the “sweet spot” that mold likes to grow. Conversely, next year could also be the driest on record, etc. Materials are judged in classes rather than independent materials for ease of modeling. The exact conditions and makeup of your construction will vary from another. Plan conservatively and allow for those conditions that are less than stellar. Keep your construction Dry and Spry instead of Gooey and New-y and you won’t end up with a Moldy Oldy.
For additional information on WUFI & WUFI BIO, visit: http://www.hoki.ibp.fhg.de/wufi/wufibioinfo_e.html