Ventilation in Adaptive Reuse : Reducing uncertainty in concept-stage decisions

Decarbonisation of the built environment requires alternatives to the prevailing practice of demolition followed by new construction. The new production of buildings adds upfront embodied emissions, while much of the non-residential stock remains underutilised, and housing demand remains high. Adaptive reuse, the practice of converting existing buildings for new functions, preserves the building's envelope and structural frame, and may retain its building services, thereby avoiding embodied emissions and capital costs. Ventilation equipment can be reused or adapted; however, concept-stage planning often defaults to full replacement of it. Early design decisions, therefore, determine whether reuse is seen as viable and what material and cost consequences follow.This thesis develops a framework for retaining or adapting ventilation in conversion projects, providing structured decision support to reduce uncertainty at the conceptual stage. The thesis comprises three strands. First, a building stock strand reconstructs pre- and post-conversion building pairs from national Energy Performance Certificates (EPCs). This is done to identify conversion pathways and describe the dominant ventilation concept, as well as the declared airflow. Second, a feasibility strand compares ventilation requirements from earlier and current Swedish building regulations. This strand also uses interview data to capture practitioners’ perspectives on when reuse is acceptable and how responsibilities are allocated. Third, a design-science strand develops a ventilation-aligned, low-intervention design (VALID) sequence that screens functional programme-layout compatibility, aligns high-demand rooms with existing supply terminals, and assesses consequences through scenario-based LCC and LCA limited to stages A1–A5.Three results follow. Stock-scale conversions concentrate on office-to-residential and retail-linked pathways. Within these, EPCs tend to indicate retention of the ventilation concept, and where paired changes in declared airflow are detectable, reductions dominate. The feasibility strand suggests that office-to-apartment, school-to-apartment, and school-to-office pairs may meet contemporary outdoor air requirements without altering the ventilation concept. Practitioners state that reuse is acceptable when performance, cleanliness, airtightness, origin and documentation of the ventilation systems can be verified. Applying the screen-align-appraise method to an office-to-residential case enables a large portion of the existing ventilation system to be retained, resulting in reductions in carbon emissions (stages A1–A5) and construction costs compared to full replacement. A workshop-based screening of a pre-school-to-elderly care case led to rejecting the conversion because the required functional divisions and adjacencies could not be accommodated within the as-found layout.The primary contribution of this thesis is the reduction of concept-stage uncertainty in adaptive reuse projects with a focus on ventilation. This is achieved by establishing a national baseline for conversion pathways and ventilation characteristics within these pathways, developing a feasibility framework that translates regulations and acceptance procedures into project-level conditions for reuse, and conceptualising a low-intervention conversion method that focuses on preserving existing supply-air systems and reporting ranges of environmental and cost outcomes. This approach can support lower-intervention conversions where hygiene, airtightness and documentation requirements are met.