Conversion factors for area measurement estimations
In order to support all reporting use cases in BuildingMinds Platform, the area measurement service will estimate some key area measurements based on the below conversion factors. The area measurements that can be estimated for a site/building/floor/space are: Gross floor area (GFA), Gross internal area (GIA), Net room area (NRA), Rentable area (RA) and Energy reference area (ERA).
For each estimation, we consider the primary building type or the primary site type and the provided area measurement data for the site/building/floor/space (GFA, GIA, NRA, ERA, RA).
Area type | Definition | Conversion factor |
|---|---|---|
Gross floor area (GFA) | Entire floor area, including external and internal walls. | GFA = GIA / 0.95 (Industrial)(1) GFA = GIA / 0.9 (all other building types)(1) GFA = NRA / 0.85 (residential)(3) GFA = NRA / 0.87 (non-residential)(2) GFA = ERA / 0.85 (non-residential)(4) GFA = RA / 0.545 (residential)(3) |
Gross internal area (GIA) | Entire floor area, including internal walls, but excluding external walls. | GIA = GFA x 0.95 (industrial)(1) GIA = GFA x 0.9 (all other building types)(1) GIA = RA / 0.85 (office)(1) GIA = RA / 0.95 (all other building types)(1) |
Net room area (NRA) | Only empty spaces on a floor. Excluding internal and external walls. | NRA = GFA x 0.85 (residential)(2) NRA = GFA x 0.87 (non-residential)(2) |
Rentable area (RA) | Area specified in the rental contract. | RA = GIA x 0.85 (office) (1) RA = GIA x 0.95 (all other building types) (1) RA = GFA x 0.545 (residential) (3) ERA = 1.2 x RA (5) |
Energy reference area (ERA) | Heated and/or cooled area. | ERA = 0.85 x GFA (non-residential) (4) ERA = 1.2 / RA (5) |
Sources:
(1) Development appraisal methodology, city of London LINK: attachment_6.3_-_development_appraisal_methodology.pdf (london.gov.uk)
(2) IFBOR: Flächen- und Raumkennzahlen Flächen- und Raumkennzahlen / fl-228-chen-und-raumkennzahlen.pdf / PDF4PRO
(3) Kalusche (2011): Grundflächen und Planungskennwerte von Wohngebäuden Grundflächen und Planungskennwerte von Wohngebäuden - PDF Free Download (docplayer.org)
(4) Bundesministerium für Wirtschaft und Energie, Bundesministerium des Innern, für Bau und Heimat: Bekanntmachung der Regeln für Energieverbrauchswerte und der Vergleichswerte im Nichtwohngebäudebestand. 2021. GEGPortal - Homepage - Bekanntmachung der Regeln für Energieverbrauchswerte und der Vergleichswerte im Nichtwohngebäudebestand (bund.de)
(5) Suchergebnis – Bundesanzeiger
(6) Baukosteninformationszentrum Deutscher Architektenkammern GmbH (Hrsg.): BKI Baukosten 2010. Teil 1: Statistische Kennwerte für Gebäude. BKI Verlag, Stuttgart 2010