Calculators · Consulting
Treated floor area (TFA)
PHPP usage factors · room by room
The TFA is the denominator behind every kWh/m²a a Passivhaus is judged on, and getting it wrong moves the whole result. Apply the PHPP usage factors room by room, the way a certifier will check it.
Room schedule
Net internal area per room, with its PHPP factor.
Indicative. The certifier confirms the TFA against drawings and the PHPP TFA worksheet; sloped ceilings, stairs and shared areas have specific rules a quick total can miss.
The PHPP factors
- Living space, habitable rooms, kitchen, bath, circulation:
100%. - Service / ancillary, utility, store, plant, not part of the living area:
60%. - Low height 1.0–2.0 m, under a slope:
50%. - Under 1.0 m:
0%, not counted.
TFA = Σ (room area × factor). Specific demand = annual demand ÷ TFA, judged against the Passivhaus 15 kWh/m²a heating limit.
Why trust it: these are the PHPP usage-factor rules, and every model we certify is checked by one of our 7 accredited Passivhaus certifiers.
Take it further
Want the TFA and the full PHPP done right?
The TFA sets the denominator; the model sets the result. Send us the room schedule and drawings and we will build and certify it.