EnergyPlus hygrothermal modeling gets dismissed as impractical for serious building envelope analysis. The interface is clunky, the documentation assumes you already know what you're doing, and most practitioners reach for purpose-built software when moisture modeling comes up. But the Heat and Moisture Transfer (HAMT) implementation itself is more capable than its reputation suggests.

The HAMT module solves coupled heat and moisture transport through multi-layer assemblies using finite element methods. It handles temperature gradients, vapor pressure differentials, moisture-dependent material properties, and phase change while staying integrated with the whole-building thermal simulation. That integration matters when moisture behavior affects thermal performance or when you're modeling HVAC strategies that influence both temperature and humidity fields. No manual boundary condition transfers between disconnected tools.

The standard implementation has gaps. It doesn't account for moisture sources from air leakage, which is problematic given that air transport delivers orders of magnitude more moisture than diffusion alone. The vapor transport coefficients don't incorporate driving rain effects, so the model underestimates moisture loading during wind-driven precipitation. These aren't edge cases. They're common failure mechanisms.

With targeted code modifications (adding air leakage moisture source terms and updating vapor coefficients to incorporate driving rain effects) EnergyPlus HAMT produces results comparable to EN 15026 benchmark tests. EN 15026 is the standard validation framework for hygrothermal models in European practice, covering varied climate conditions, assembly configurations, and moisture loading scenarios. Achieving comparable results validates the physics implementation. The modifications don't restructure the governing equations, they just complete the representation of real-world moisture sources.

This presentation demonstrates that EnergyPlus HAMT, properly configured and enhanced, delivers benchmark-validated hygrothermal analysis. You'll see the specific code modifications, the EN 15026 validation results, and examples of when this approach offers capabilities that specialized tools can't match. If you've written off EnergyPlus for moisture modeling based on interface complaints rather than actual performance testing, the validation data presented here suggests that's worth reconsidering.

3D thermal bridging through building façades has long been overlooked or oversimplified in design practice and building energy regulations. At the same time, building enclosures are facing ever-increasing demands in terms of thermal performance. In cold climates, the required overall U-value of façades is often very low. As insulation layers become thicker, the relative impact of thermal bridges increases.

Point thermal bridges, such as façade anchors, result from local penetrations of the insulation layer. More and more, energy regulations require their impact to be explicitly calculated in order to account for the associated heat losses.

The aim of this presentation is twofold. First, using practical case studies, we demonstrate the order of magnitude of the errors that can arise from strongly simplified thermal bridge modelling. Particular attention is given to the differences between 2D and 3D thermal bridge calculation approaches.

In the second part of the presentation, the results of a Belgian research project are presented, in which a new meshing algorithm was developed to efficiently solve complex 3D thermal problems. The adaptive meshing algorithm generates non-conformal meshes, allowing finer meshes in critical regions and coarser meshes elsewhere. This new meshing algorithm has been implemented in an existing 3D thermal bridge tool to investigate its effectiveness. Preliminary results indicate that the adaptive mesh method can reduce the number of calculation nodes by a factor of 2 to 10 compared to previous approaches. The resulting significant reduction in calculation time is demonstrated through a case study involving the computation of the overall U-value of a complex rainscreen cladding façade.

Accurately reproducing zone air temperature dynamics remains difficult even in well-calibrated building energy models, especially when the goal is short-timescale behavior rather than seasonal energy balance. We present a measurement-constrained case study for a model based on a highly instrumented, three-story cross-laminated timber (CLT) building with zone temperature, heat-flux, and electrical submetering, with measurements that include multi-day periods with the HVAC intentionally switched off.

To minimize input uncertainty, we constrain the model with measured weather, operating schedules and control sequences, and internal loads, and we translate an on-site furniture audit into explicit internal thermal mass objects. This reduces reliance on generic occupancy and gain assumptions, enabling remaining temperature mismatches to be interpreted primarily as heat transfer and coupling effects.

We evaluate three common pathways for improving transient agreement with measured temperatures: (1) effective thermal mass multipliers, (2) zone air capacitance multipliers, and (3) interior convection assumptions for walls, floors, ceilings, and internal mass objects. The model is implemented in an OpenStudio/EnergyPlus workflow, with Energy Management System (EMS) used to override interior convection. In our case, adjusting mass and air capacitance meaningfully changes damping and time constants but does not reliably improve agreement across both HVAC-on and HVAC-off periods. In contrast, changes to interior convection formulations produce large shifts in response timing and shape, indicating that convection modeling can dominate how thermal storage couples to zone air.

To support systematic exploration, the convection override is exposed through an OpenStudio measure that parameterizes the interior convection relationship (temperature-difference coefficient and exponent) with separate inputs for HVAC-on vs HVAC-off periods, enabling straightforward sweeps and future calibration workflows. The presentation compares these levers side-by-side against field data to quantify how sensitive simulated zone temperature trajectories are to mass, air capacitance, and convection choices under varying operational conditions.

The talk closes with a comparative evaluation of these levers that clarifies which assumptions most strongly shape transient temperature response (timing and damping) under different operating conditions, offering transferable insight for diagnosing dynamics mismatches in other models.

Adaptive kinetic façades (AKFs) with three-dimensional, shape-changing geometries can dynamically modulate solar gains and daylight, yet standard building performance simulation (BPS) tools cannot directly resolve their complex optical behavior. This study proposes a schedule-based surrogate workflow that couples Radiance ray-tracing with EnergyPlus to enable whole-building energy simulation of geometrically complex AKFs. High-fidelity optical outputs (transmitted solar radiation and workplane illuminance) are mapped into time-varying transmittance and lighting control schedules that drive a planar surrogate façade in EnergyPlus. The workflow is first verified against a venetian blind benchmark, achieving annual transmitted solar radiation agreement within 0.2% normalized mean bias error. It is then applied to a kirigami-inspired façades across 20 actuation states and four orientations, revealing orientation-dependent optima and quantifying up to 20% additional energy savings through adaptive control. Comparison with native EnergyPlus blind proxies shows that geometric simplification introduces end-use prediction errors and leads to suboptimal design selections.

Thermal bridging in building envelopes is increasingly recognized as a critical factor in achieving high-performance, energy-efficient buildings. As codes and standards evolve, ASHRAE Standard 90.1-2022 and the Energy Codes in Canada (NECB) now require more rigorous accounting and mitigation of thermal bridges in compliance modeling, design, and construction. This session provides a foundational overview of thermal bridging modeling, focusing on heat transfer calculations and code requirements for envelope assemblies.

Participants will learn the distinctions between clear field, linear, and point thermal bridges, and how each impacts overall building envelope performance. Clear field assemblies represent uniformly distributed thermal bridges, such as framing and ties, while linear and point bridges occur at interface details—slab edges, parapets, window transitions, and penetrations—that can significantly increase heat flow and undermine insulation effectiveness.

The presentation will demystify the calculation methodologies now embedded in ASHRAE Standard 90.1 and Canadian Codes. Attendees will be introduced to the area-weighted and linear transmittance approaches, including the use of Psi (Ψ) and Chi (χ) factors for quantifying heat flow through linear and point bridges, respectively. Practical examples will illustrate how to perform length and area takeoffs from architectural drawings, assign transmittance values from catalogues or modeling, and aggregate results to determine overall U-values for compliance.

ASHRAE Standard 90.1-2022 introduces prescriptive and performance paths for thermal bridging mitigation, with Section 5.5.5 detailing requirements for common interfaces—roof/wall intersections, floor edges, cladding supports, window-to-wall transitions, and miscellaneous penetrations. The Standard provides default values and modeling protocols, allowing users to demonstrate compliance via prescriptive insulation increases, trade-off calculations, or whole-building energy simulations. Canadian Codes similarly integrates thermal bridging into its compliance framework, emphasizing the need for accurate modeling and reporting of Psi and Chi values.

The session will also address practical challenges in modeling, such as dimensional conventions (internal vs. external plane), software implementation, and the integration of thermal bridging data into energy models. Attendees will gain actionable knowledge for selecting appropriate modeling methods, interpreting code requirements, and leveraging catalogued data to streamline compliance and optimize envelope design.

By the end of this session, participants will be equipped to confidently model thermal bridging in accordance with ASHRAE Standard 90.1 and NECB, ensuring their projects meet evolving energy performance standards and contribute to a more sustainable built environment.