All of the renovations used systems engineering principles to ensure good indoor air quality and longterm durability while providing deep energy reductions. Extensive information on these topics can be found on our company's Web site (www.buildingscience.com).

• drainage plane (water-repellent materials designed to drain water-e.g., housewrap, building paper or taped facing on sheathing);
• air barrier (airtight continuous enclosure around conditioned space);
• thermal barrier/insulation (layer that controls heat flow by conduction between interior and exterior).
• vapor control (materials designed to control the movement of water by vapor diffusion, to prevent accumulation that can result in damage to the building);
• combustion safety (fossil fuel burning appliances using sealed combustion technology);
• air change (provision for dilution of interior air with outside air);
• pollutant removal at source (bath and kitchen exhaust fans).