Homes and buildings are very similar to ecosystems. Just as we have learned that one change to an ecosystem (e.g. the introduction of a new plant or insect) causes ripple effects to all the species in that system, changes to one aspect of a building (e.g. plumbing) has implications for the way the whole house operates to support or interfere with good health.

Understanding a building as a system is critical to avoiding inadvertent health hazards and to fixing hazards. While exhaust fans to remove excess humidity and vent cooking exhaust can promote indoor air quality, they can sometimes draw so much air out of the house that they cause backdrafting in the furnace flue, drawing unhealthy air (containing carbon monoxide and other combustion by-products) into the home. Thus, the size and placement of exhaust fans need to take into account the patterns of air flow and pressure throughout the structure.

Similarly, taking a holistic approach can yield multiple health benefits and reduce overall costs. Efforts to improve the energy efficiency of a home or multi-unit building can incorporate some simple, low-cost actions that improve the health of residents and the durability of the building. For example, when installing new windows to reduce air leakage, it is easy and cheap to add pan flashing—simple materials that force water to drain outside the building. When sealing holes to reduce energy waste, it is a simple matter to use methods and materials that will also prevent access to rodents and other pests.

Addressing housing-related health hazards individually—by separate teams of specialists trained only in a single hazard—is inherently inefficient. Past policies have individually and serially abated asbestos, mitigated radon, and controlled lead-based paint hazards. Ensuring healthy housing conditions requires policies and practices that acknowledge and address the interconnections. This type of comprehensive and house-as-a-system approach is also flexible. As new housing-based health conditions emerge, the infrastructure will be in place to address such hazards.