conversion to passive heating begins
The physical processes of refitting a building to enable passive heating begin.
The conversion of a building or structure to passive heating begins when the first physical alterations take place readying it for passive heating. The conversion process typically involves creation of an airtight shell through low u-value windows, a ventilation system with high heat recovery, and highly rated insulation.
The first physical alterations must be directed toward the building's passive-heating conversion. A proposal or a decision to convert is not itself the physical commencement.
An environmental upgrade can improve energy efficiency without achieving passive heating. This conversion has the more specific objective defined for passive heating and ends with the last physical alterations.