A building envelope includes exterior components, such as the roof, walls, foundation and windows. A high-performance envelope is the most effective opportunity for achieving decarbonization of a building through passive strategies.

Optimization of the envelope can significantly reduce heating and cooling Requirements in the building, thus reducing energy consumption and electrical demand as well as decreasing the size and costs of mechanical equipment.

Lower cost measures might include resealing, replacing broken windows, adding shading to sunny areas or similar strategies. At a minimum, air leakage should be addressed.

If budgeting and renewal cycles permit, it is ideal to undertake a deep green envelope upgrade before HVAC systems are retrofitted to optimize mechanical system design.