Builders often justify the cost of energy design improvements in terms of lower energy bills over time (see "Energy Upgrades: Cash Flow vs. Payback," Focus on Energy, 4/96). But people sometimes don't realize that energy-efficient design can also have an immediate payback. In cooling climates, for example, design and construction details can reduce peak cooling loads. This allows the builder to reduce construction costs for air conditioning by installing smaller equipment, smaller ductwork, and smaller electrical service. For 20 years or more, contractors have sized cooling equipment by a simple, traditional formula: one ton per 600 square feet of floor area, plus half a ton. But if you build a house to the standards specified in the Model Energy
