GEG and BIM: preparing building data for energy assessment

Agree which geometry is needed

A purpose-built model can provide areas, room heights, openings and component locations. Their suitability for energy calculations depends on modelling rules and the agreed reference. A lettable area is not automatically the correct reference area for an energy calculation.

Before scanning, agree the required geometry with the energy specialists. Include how adjacent unheated areas, concealed construction and inaccessible rooms will be handled.

Recognise what a scan cannot establish

A geometric survey does not verify U-values, hidden insulation layers or actual plant efficiency. Drawings, product records, equipment information or additional investigations are needed. Consumption records require appropriate periods and a traceable allocation.

Keep unknown properties open or label them as documented assumptions. Particularly in older buildings, an honest gap register is more useful than an apparently complete model containing unverified material properties.

Separate the German and Swiss context

For a German project, the consolidated legislation applicable at the time of assessment is decisive. The familiar topic label GEG used here does not replace that check. A BIM model is neither an energy certificate nor statutory proof; calculations, professional eligibility and applicability require specialist assessment.

Gesetze im Internet · konsolidierte Gesetzesfassung / consolidated legislation ↗

Prepare a consistent renovation dataset

Swiss buildings require attention to the applicable cantonal rules. GEAK is a building energy assessment and advisory instrument used across Switzerland. German requirements therefore cannot simply be transferred to a property in Rotkreuz.

Bring together a checked model, source register, plant records and unresolved issues. Compare options on consistent assumptions. After construction, document the actual installed condition and the corresponding product and equipment records.

• Align geometric and energy reference areas.
• Provide sources for construction and plant values.
• Have assumptions approved before calculation.
• Arrange review by qualified specialists.

Swiss Federal Office of Energy · Cantons and municipalities ↗