9. Energy Efficiency and Solar
Energy efficiency begins with your home’s ability to keep warm air in and cold air out in the winter, and hot air out and cooler air in during the summer. After building a high-performance thermal envelope, you can determine the appropriate solar power system to reduce your electric costs—possibly to near zero—subject to the electricity purchase policy and net-metering rules of your local utility. Start with the Envelope The Frame / Skeleton Begin by constructing an energy-efficient exterior wall assembly. You may choose: • 2 × 4 wall panels (true dimension: 1.5 in. × 3.5 in.) • 2 × 6 wall panels (true dimension: 1.5 in. × 5.5 in.) From an insulation standpoint: • A 5.5-inch wall cavity can hold approximately 57% more insulation than a 3.5-inch wall cavity. • A 2 × 4 wall accommodates only about 66% of the insulation of a 2 × 6 wall. The cost to upgrade from 2 × 4 to 2 × 6 exterior skeleton walls is typically: • ~7% more in skeleton cost • ~2% more in total project cost This upgrade often delivers a strong return in comfort, durability, and long-term energy savings.
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