A building may contain substantial insulation and high-performance windows while still losing conditioned air through gaps between construction elements. Wall-to-floor junctions, window perimeters, roof connections and service penetrations can collectively undermine the intended performance of the envelope.

Passive House design addresses this by establishing a defined airtight layer around the conditioned building volume. The layer may be formed by membranes, boards, plaster, concrete or other suitable materials, but it must remain continuous across changes in construction.

This article focuses specifically on airtight-envelope design and testing. For the wider standard, five principles, PHPP and Australian climate application, see the Passive House in Australia Knowledge Hub.

A building can begin with a strong performance objective and still change substantially before completion. Window substitutions, revised insulation, modified junctions, altered shading and unrecorded service changes may all affect the final energy balance.

Passive House certification introduces an independent review pathway through those changes. The process connects PHPP modelling with design documentation, selected products, airtightness results, ventilation information and the building that was actually constructed.

This article focuses on how certification can protect long-term energy and operating-cost outcomes. For the complete certification sequence, see the Passive House Certification Process Guide.

Existing homes present conditions that do not arise in the same way on new buildings. Orientation, structural junctions, floor levels, roof geometry, boundaries, heritage fabric and concealed construction may already be fixed before the retrofit begins.

EnerPHit accounts for these constraints while retaining a defined pathway for energy demand, envelope performance, airtightness, ventilation, documentation and construction verification. It should not be used as a general label for any renovation that adds insulation or improves windows.

This guide focuses specifically on the retrofit pathway. For the wider standard, five principles, Australian climate application and PHPP framework, see the Passive House in Australia Knowledge Hub.