Water is your number one enemy as a home owner, so when you build, it makes sense to go over board with measures to keep your home dry. In addition to structural problems, water helps mold grow. Mold needs 3 things to grow, mold spores (which are everywhere), warm temperature, and water. The only element that you can control is moisture. (Click Here for sites to explore mold issues with new and existing homes.)
In the 1970s homes were built tighter and tighter, and the result was a build-up of moisture in the home, the growth of mold, and thus, the onset of poor indoor air quality and rotting walls. Today, there are viable strategies to defeat mold growth, but the important thing to think about is moisture. We live in Western Washington State where it rains for about 9 months of the year, and mold is something that every builder and homeowner should understand before breaking ground!
Barrett has installed a drainage plane on the outside wall to allow the walls to dry out. (Among the first of its kind in the area.) The 1x4"s will be covered with HardiPlank. A vent is installed at the top and bottom (plastic comb product shown on right) to dry out the wall and prevent mold growth. A vent is placed at the top and bottom of the drainage plane.
Thus, if the wall gets wet, there is an air channel for it to dry. The paper will keep liquid water from entering the side wall, and indoor humidity will be balanced through the home ventilation system, keeping it from moving into the wall.
It is important to understand three principles ... 1) warm air can hold more water than cold air, 2) water will always travel towards an area with less water, and 3) heat travel to cold. Thus, 70% humidity indoor air will hold more moisture than 70% humidity cold outdoor air. The warm interior air will travel to the cold carrying its moisture until it hit a cold outdoor temperature where water will be released/condense. Wet soil around a house will have water travel towards a dry basement. This is the dynamic of water. It is unavoidable, and it will create mold if your wall system is not constructed properly.
For example, a block basement with insulation on the interior of the foundation, allows moisture to move through the block toward the basement as interior air with moisture moves through the insulation toward the block. Between the foundation and the insulation water will condense and those pesky mold spores will start to grow. Message: insulate your basements on the outside of the foundation.
The first line of defense is to made certain that drain tile are installed around the foundation to carry excess water away from the house. In addition, we made certain that our plans called for storm gutters to capture water and take it away from the house as did the landscaping plan. Finally, our architect, Mort James, insisted that our roof have a 3 foot overhang to keep water away from the house, and to the degree possible off the siding.
However, we will have land bermed against 3 walls, and needed to protect these concrete walls from water which will invade concrete through capillary action (minute cracks in the concrete.) The concrete was sealed with sodium silicate ... a crystalline waterproofing solution. The PATH website of the National Association of Home Builders Research Center explains what this does better than me.
"Long available for industrial applications, crystalline waterproofing is now ready for use in residential applications. It consists of a dry powder compound of Portland cement, very fine treated silica sand, and proprietary chemicals. Combining the product with water and applying it to the surface of concrete results in a catalytic reaction that forms several inches of non-soluble crystalline fibers within the pores and capillary tracts of concrete. This seals the concrete against the penetration of water or liquids from all directions. Crystalline waterproofing replaces traditional solvent-based waterproofing on foundation walls. Its most cost effective application is a waterproofing for concrete floor slabs and basement walls of existing homes that are seeping water."
Next, we use a product called SuperSeal. This plastic, dimpled product was pasted between the outside soil and exterior insulation and creates air channels that allow air to dry out the concrete and insulation if water gets into the wall (similar to the drainage plane discussed earlier).
Insulation should always be placed on the outside of a concrete wall. Water vapor that gets into a warm concrete wall will turn to liquid water when it hits a cold area (again warm air holds more water than cold air.) Thus, if the concrete is kept warm, the water vapor will not turn to water and stimulate mold growth inside the home. The SuperSeal further protects the insulation by allowing it to breathe and dry out.
Walls and roofs need to be wrapped on the outside with a water proof wrapping material. Barrett, in keeping with our desire to be green, selected a product called RainDrop which is a GreenGuard certified product. In other words, it has been through a testing program to certify the product for environmental performance, specifically off gassing.
So, now that you know how to prevent mold, I can tell you that all the rain our area had during construction, created mold growth on the inside of the house. Above we discussed the items needed to grow mold, heat, mold spores and water, with the latter being the only one controllable. It is probable that once we finally sealed everything up that the mold that we see in these pictures would not be a problem ... they would lack moisture to continue growing. However, this is a belt and suspenders project so we took the extra step to treat all interior surfaces with a borate solution to kill the mold that was there and frankly provide lifetime peace of mind about mold.
If you are considering cellulose insulation, it is advisable to consider one treated with borax. It kills mold, has no smell and is safe for inhabitants.
Remember a GreenBuilt Home is also Quality Built Home !!
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Sunday December 17, 2006 05:34 PM -0800
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