The Challenge
Schools are institutions not just of education but of sustainability practice, exemplified in design. Our client, a mid-size architecture practice, set out to create a primary school that stands as a testament to ecological mindfulness. The aim was a modern, low-energy building conforming to the stringent Passivhaus standards, which necessitates meticulous planning and precise execution.
The challenges were manifold. The primary school design required integrating a wide array of mechanical and architectural components without compromising on spatial aesthetics or comfort. Coordinating between various stakeholders and ensuring compliance to the Passivhaus energy efficiency benchmarks, all while maintaining construction timelines, was paramount.
The Solution
Our team at Adyantrix was enlisted to provide BIM coordination services, leveraging our extensive experience in fostering sustainable construction projects. We meticulously prepared a comprehensive BIM execution plan, focusing on clear communication flows and data integration from the various disciplines involved.
Utilising Revit as our primary tool for family creation and clash detection, we ensured every element of the design aligned with the Passivhaus standards. This required precise modelling of thermal bridges, airtightness, and incorporating high-performance insulation details. By streamlining the data across all phases, including architectural, structural, and MEP designs, we ensured cohesion and automated the resolution of potential clashes.
Beyond this, our simulation-driven approach allowed us to run real-time energy performance evaluations, providing insights into the building's anticipated operational energy usage. This proactive monitoring was crucial in meeting the significant reductions in energy needs as mandated by Passivhaus certification.
Key Results
By the project's conclusion, the primary school met all Passivhaus criteria, becoming a pioneer of sustainable design in the education sector. Our BIM coordination delivered a 30% reduction in projected energy consumption compared to national standards, marking significant savings in operational costs.
Additionally, by managing potential construction issues preemptively, we reduced the construction timeline by 15%, proving the efficacy of BIM-enabled coordination. The clear documentation and visual renderings facilitated seamless stakeholder communication, enhancing decision-making processes throughout the design and construction phases.
Ultimately, our collaboration with the architecture practice not only fulfilled the client's sustainability goals but also set a new benchmark for energy efficiency in educational architectures. The project exemplifies our capability to align advanced BIM technologies with eco-friendly architectural visions, bringing forward actionable results that benefit both the environment and the academic community.
Technical Approach
Passivhaus certification introduces a set of technical requirements that are far more exacting than conventional building regulations — a maximum specific heating demand of 15 kWh/m²/yr, airtightness below 0.6 air changes per hour at 50 Pa pressure differential, and a primary energy demand below 120 kWh/m²/yr. Achieving these targets in a primary school environment, where internal heat gains from occupancy are high and fresh air demand is significant, required BIM and energy modelling to work in continuous dialogue throughout the design process.
The primary BIM authoring tool was Autodesk Revit, and the Passivhaus energy certification calculations were managed in PHPP (Passive House Planning Package) — the standard tool accepted by the Passivhaus Institut for certification. The critical challenge was maintaining consistency between the BIM geometry and the PHPP model: any dimensional discrepancy between the two could result in incorrect U-value area calculations or thermal bridge length misreporting, potentially invalidating the certification submission.
To address this, we established a direct geometry export workflow from Revit to PHPP using the THERM plug-in and structured manual verification checks at each RIBA stage. Key technical decisions included:
- Airtightness detailing in the BIM model — the continuous air barrier was modelled as a distinct layer within the Revit wall, floor, and roof assemblies, with penetrations through the air barrier (service entries, window reveals, structural supports) each modelled individually and cross-referenced against the PHPP junction library
- MVHR system modelling at LOD 350 — the mechanical ventilation with heat recovery (MVHR) duct network was modelled in full three-dimensional detail, with duct lengths, bends, and terminal unit positions captured accurately to enable PHPP duct heat loss calculations to use actual measured values rather than estimated defaults
- Thermal bridge modelling using THERM finite element analysis for all non-repeating junction types — including window-to-wall, wall-to-roof, and wall-to-slab connections — with psi values calculated and imported into PHPP to reflect the project-specific junction geometry rather than generic catalogue values
- Navisworks clash detection run across structural, architectural, and MVHR duct models, with a specific focus on MVHR duct penetrations through the structural frame, where uncoordinated holes could compromise both airtightness continuity and structural integrity
- Revit custom families created for Passivhaus-certified window units, including accurate thermal frame and edge spacer geometry to support precise window U-value and g-value calculations within the model
Implementation Highlights
The coordination programme ran over fourteen months, structured around the RIBA Plan of Work stages. Given that the architecture practice was a mid-size studio without an in-house BIM coordination capability, a significant part of our role was to establish and manage the multi-discipline coordination process on their behalf.
BIM Execution Plan and workflow setup (RIBA Stage 2): At the outset, we produced a BIM execution plan that defined the responsibilities, deliverable formats, and coordination meeting cadence for the structural engineer, MVHR specialist, and civil engineer engaged on the project. Passivhaus-specific requirements — including the need for all Revit assembly types to carry certified U-value data as shared parameters — were written into the BEP as contractual BIM requirements for all contributing parties.
Envelope performance coordination (RIBA Stage 3): The most technically demanding coordination task at Stage 3 was reconciling the structural engineer's concrete upstand details with the Passivhaus thermal bridge requirements at the wall-to-floor junction. The structural engineer's initial detail created a significant thermal bridge that, when analysed in THERM, added 0.12 W/mK to the linear thermal transmittance of the perimeter — enough to push the PHPP space heating calculation above the 15 kWh/m²/yr threshold. Four iterations of the junction detail were modelled in THERM and cross-referenced against structural adequacy before a thermally broken upstand solution was finalised.
MVHR coordination and clash resolution (RIBA Stage 4): The MVHR duct network, serving classrooms across two storeys, presented the densest coordination challenge. Supply and extract ducts running in parallel, combined with structural beam penetration requirements, generated 47 hard clashes in the first federated model run. These were resolved over six weeks through a combination of duct rerouting, structural opening repositioning, and beam depth adjustments. All resolved details were documented with before-and-after clash screenshots in the BIM 360 issue log, providing a clear audit trail for the contractor's site team.
Pre-construction airtightness risk review: In the final stage before construction documentation was issued, we conducted a complete review of the BIM model specifically from an airtightness perspective — tracing the air barrier line through every junction in the model and identifying seven locations where the continuity of the barrier had been inadvertently broken in the architectural detail. These were corrected in the model and reflected in updated construction drawings, preventing what would otherwise have been costly on-site remediation during the airtightness test.
Measurable Outcomes
- Passivhaus certification achieved at first submission, with the PHPP calculations verified by the certifier against the BIM-derived geometry data — no dimensional discrepancies were identified
- Projected energy consumption 30% below national baseline, validated through PHPP modelling and corroborated by the building's energy monitoring system in the first academic year of operation
- Construction programme reduced by 15% compared to the architecture practice's previous comparable school project, attributed to the elimination of on-site coordination issues through BIM pre-construction clash resolution
- MVHR commissioning completed without any duct rerouting required on site — all 47 clashes identified in the BIM coordination process had been fully resolved before construction began
- Airtightness test result of 0.42 ACH at 50 Pa — comfortably below the 0.6 ACH Passivhaus threshold — achieved on the first test attempt, reflecting the quality of the airtightness detailing carried through from the BIM model to the construction drawings
- Operational energy costs in the first year of operation were 28% lower than those of a comparable school built to current Part L standards in the same local authority area, providing a tangible financial benefit to the school's annual budget
Lessons Learned
Delivering Passivhaus-standard BIM coordination for an education project produced insights specific to the intersection of certification-standard energy performance and multi-discipline construction coordination.
PHPP and Revit must be treated as a linked pair, not parallel workstreams. On projects where energy modelling and BIM modelling are managed by different parties without a structured geometry synchronisation protocol, it is common for discrepancies to accumulate — a wall assembly revised in Revit for structural reasons, for example, may not be reflected in PHPP for weeks. On this project, a formal geometry check was performed at each RIBA stage gate, comparing the BIM model dimensions against PHPP inputs. This took approximately half a day per gate but prevented the certification risk that discrepancies would otherwise have created.
Thermal bridge resolution is a multi-discipline challenge. The instinct of structural engineers is to detail for structural adequacy; the instinct of architects is to detail for aesthetic continuity. Thermal performance is often treated as the thermal engineer's problem. On Passivhaus projects, thermal bridge performance at junctions directly affects the certification outcome and must be treated as a shared multi-discipline responsibility from Stage 2 onwards. Establishing this expectation clearly in the BIM execution plan — and backing it with THERM analysis at every key junction — is the most effective way to prevent thermal bridge issues from emerging late in the design process.
Airtightness is a construction process challenge as much as a design challenge. Even with perfectly detailed airtightness junctions in the BIM model, the achieved airtightness depends on the construction team's understanding and execution of the air barrier continuity on site. We recommend that BIM airtightness trace diagrams — visual plan and section drawings showing the air barrier path highlighted in the model — are included as a specific construction drawing type in the information release. On this project, the contractor's site foreman credited these diagrams as the clearest guidance they had received on any Passivhaus project, reducing the number of clarification requests during construction considerably.
Speak with our BIM Consulting team at Adyantrix to find out how we can support your next project.
Work with Adyantrix
If you are looking to tackle a similar challenge, Adyantrix has the expertise to help across the full project lifecycle. Our BIM consulting practice covers BEP authoring, ISO 19650 strategy, and CDE implementation. Our architectural BIM practice covers Revit modelling from concept through construction documentation. Our clash detection & coordination practice covers multidisciplinary coordination and conflict resolution. Our Revit family creation practice covers parametric Revit content built to project and manufacturer standards. Get in touch to discuss your requirements — no commitment required.
