Standards, subsidies, and carbon taxes are among the measures often considered to reduce energy consumption and carbon dioxide (CO₂) emissions in the buildings sector. Using a modeling system developed by the U.S. Energy Information Administration, residential and commercial sector standards and subsidies were each modeled with and without a carbon tax to determine if a multipolicy approach would be redundant. A separate case examining a carbon tax was also completed for comparison. Between the two equipment-based policies, subsidies achieved more energy and CO₂ emissions reductions at less cost to consumers, as incremental investment costs were shifted to the government. When either of the equipment-based policies was combined with a carbon tax, their energy-and carbon-reducing effects were more addictive than redundant.