• Durable
• Sustainable
• Comfortable.

Water is not only the most important factor affecting a home's durability, it is also the most important factor affecting the home's maintenance costs and sustainability.

Jim Sargent, chosen by the U.S. Department of Energy as the Builder of the Year for his energy-efficient homes, tells his green building classes, "Homes last longer in dry areas. Moisture is the enemy. In fact, the biggest enemy your house has is moisture. If a builder has a problem with the house, 99% of the time it is going to be water or water vapor related. If a builder needs to be an expert on anything, it is water control."

Homes get wet during construction, during renovation or with age. The problem, though, is not that homes get wet but the solutions for moisture control. Homes need a good drying system in place and it is important that they are dried as quickly as possible.  

The concept of drying and the design of homes to dry is part of moisture control. Moisture and its movement must be controlled from the beginning of the build job to the end of the home's life.

There are several sources of moisture in the home. The most important to control are below. 

• Rain.
• Plumbing.
• Ground water.

Sargent says, "Controlling rain is the single most important factor in the design and construction of durable buildings and in the control of mold."

Building physicist Joe Lstiburek takes it one step further and declares, "If you can't control rain and ground water, it is senseless to go further in building a structure."

Sargent continues, "Homes must be designed with rain control for the location's climate in mind. For example, we get an average of 39 inches of rain a year in the Dallas-Fort Worth area. However, it does not come one inch here and one inch there. We get most of the rain in short periods of time in the spring and the fall. Homes should be designed like we get 120 inches of rain a year instead of 39 inches."

Other sources of water that need to be kept under control are:

• Moisture from human & animal bodies.
• Moisture from human activities such as cooking, bathing, or washing dishes and  clothes.  
• Exterior moisture and water vapor
• Construction moisture--from building materials.
• Surface water
• Snow and ice damming (not a DFW problem).

These sources might have different significance in different climates (such as snow in Dallas or snow in Minneapolis). The moisture sources and their climate significance must be considered when choosing materials for the construction of a home. 

Climate significance must also be addressed when allocating resources for moisture control. For example, Minneapolis needs resources allocated for snow and ice damming control; North Central Texas does not.

Moisture moves by a number of means: capillary flow, vapor flow, air convection, and gravity flow. Each of these mechanisms is driven by different forces and moves at vastly different rates through different materials. This also determines the choice of building materials for home construction.

Often walls get wet during the home's construction from rain or other precipitation. Even if they don't get wet then, they will get wet later from other means--often from both the outside and the inside of the wall. Consequently, all walls should be designed to dry, preferably from both sides but definitely from at least one side.

There are two other aspects of water that must be considered in a green home.

1. Water conservation.
2. Conservation of energy when heating water.