Responsive building envelopes (RBEs) are central to developing sustainability strategies for zero emission/energy buildings (ZEBs). RBEs are a large group of complex technologies and systems, which is why multi-criteria decision making (MCDM) methods are helpful to navigate sustainability assessments considering various performance indicators. This article first provides a literature review of assessment criteria and key performance indicators for RBEs and an analysis of existing robustness-based MCDM methods. Then, a methodological approach to assess RBE designs in ZEB projects is proposed as an extension of a novel robustness-based MCDM method that normalizes the objective functions according to defined targets and combines them into one comprehensive indicator (MT-KPI), thereby eliminating the need to weight objectives. The proposed methodological approach is finally tested on a case study of a Norwegian ZEB, where five competitive RBE designs (including building integrated photovoltaics, phase change material, and electrochromic windows) and eight occupancy and climate scenarios are investigated considering three main performance areas: energy use, thermal comfort, and load matching. The results in the case study show that with the proposed MCDM approach the different designs have MT-KPI values between 1.4 and 12.8, where a lower value is better. In this specific case, the most robust building RBE alternative was identified as the one with electrochromic windows and a control based on incident solar radiation and indoor air temperature.

Large timber buildings are increasingly used in the Nordic countries because of low greenhouse gas emissions and good access to timber. There is however uncertainty about the airtightness of the envelope of such buildings over time because of the possible timber’s shrinking and swelling, in particular when using cross laminated timber (CLT) in external walls. Therefore, two measures are often suggested to avoid moisture transport from inside to outside due to gaps in the joints of CLT external walls, i.e., a vapour barrier on the outside of the CLT elements and/or a local sealing of the joints. However, the airtightness development over time with only local sealings is uncertain. This paper presents the airtightness and thermographic assessment of a new zero-emission office building, built in 2020 in Norway. This building has a timber load-bearing system, including external timber frame walls and CLT-based walls. The timber frame walls have a vapour barrier on the warm side of the construction, while the CLT-based walls only present local sealing measures. Two thermal imaging and airtightness tests were performed: the first upon construction completion and the second after one year, to investigate possible changes in the airtightness of the building envelope over time. The air leakage results during the two tests performed with one year difference showed comparable building’s air change rate values of 0.46-0.47 h⁻¹ at a pressure difference of 50 Pa. However, the thermographic examination of the envelope from inside the building showed that local sealings had cracked in several places because of the elements’ movement. This will be further investigated as it may affect the hygro-thermal and acoustic performance of the building.

The zero-emission goal and the climate change challenge in the building sector have boosted the interest on roof constructions. As roofs are increasingly used for energy generation via photovoltaic panels and for buffering heavy rain events, the risk of leakages due to building defects is also growing. System and technology development with focus on leakages’ risk assessment through prediction, warning, and damage limitation is therefore essential. To this purpose, the moisture development in the roof represents a key aspect to evaluate. Due to seasonal variations, the moisture level is highest in the outer parts of the roof during the winter months, when condensation might occur; therefore, this might not be a sign of water leakage, but a consequence of normal transiently elevated moisture levels. Sensor technologies to be used in roofs for monitoring moisture conditions are in constant development. However, there is a lack of integrated solutions that are able to distinguish between moisture caused by rain leakages or air leakage from the indoor, and moisture due to the natural redistribution in the roof construction. In this article, typical compact roofs and climatic conditions in Norway were identified. Then, one-dimensional heat and moisture transfer simulations were performed with WUFI Pro software. The results of these simulations were used to develop a semi-quantitative system for assessing the moisture conditions in compact roofs. This system is characterized by tables with the description of expected temperature and relative humidity levels in different roof configurations under various indoor and outdoor environmental conditions. A grading system was also defined to evaluate whether the identified moisture situation is most likely safe, less safe, or unsafe. The assessment system described in this article is meant to be linked to sensor technologies for leakage warning in compact roofs, aiming to reduce false alarms by identifying expected abnormal levels.

Wooden ventilated pitched roofs represent a widely spread construction solution in Nordic countries. They have several benefits, including the drainage of excessive moisture from the construction and the reduction of the surface temperature to prevent snow melting and thus icing at the eaves and gutters. Modelling ventilated components is complex and requires a thorough understanding of the phenomena occurring in the air cavity, where convection plays a central role in the heat transfer process. The approach and the assumptions adopted for the roof model are therefore crucial to investigate the thermo-fluid dynamics in the air cavity. A literature review showed the need for comprehensive numerical and experimental research focusing on ventilated roof constructions, especially for Nordic climates. This article presents the thermo-fluid dynamic modelling of a ventilated pitched roof, which belongs to a full-scale experimental building located in Trondheim (Norway), the ZEB Test Cell Laboratory. A model of the roof was created using the finite element method-based software COMSOL Multiphysics. Transient simulations were performed in different climate conditions and the results of temperature and air flow speed along the cross section of the roof were compared with measurement data for validation. The simulation results show a good agreement with measurement data for both air speed and temperature in the air cavity, particularly in the summer day. The deviations in the numerical results will be object of study in future research, where the modelling approach will be further explored by testing different inputs, including boundary conditions and turbulence models.

As climate change leads to increasing temperatures and precipitation, building envelopes must adapt to ensure durability. Meanwhile, improving energy efficiency requires integrating new technologies directly into the building envelope. In this context, building-integrated photovoltaics (BIPV) are increasingly being adopted. However, the hygrothermal performance of BIPV components in cold, humid Nordic climates remains insufficiently characterised. This study develops and validates a computational model of the ventilated roof with BIPV at the Zero Emission Building Laboratory, a full-scale office laboratory in Trondheim, Norway. The model is implemented in COMSOL Multiphysics and simulates coupled heat and moisture transport in the ventilated air cavity, accounting for turbulent airflow, surface-to-surface radiation, moisture transport in air, and heat transfer in both solids and fluids. Boundary conditions are defined through available in situ measurements. Model validation uses temperature and relative humidity data from two sensors located near the inlet and outlet of the air cavity during two representative periods with different climatic conditions. Temperature predictions show CV(RMSE) values of approximately 6–16% and NMBE between -10% and +8%. Relative humidity predictions show CV(RMSE) values of about 8–9% at the inlet and 20–24% at the outlet, with NMBE ranging from -13% to +8%. Pearson correlation coefficients range from 0.85 to 0.99, indicating generally good agreement in the temporal evolution of the variables. The results provide insights into the coupled thermal and moisture behaviour of ventilated BIPV roofs in cold climates and support the design of climate-resilient and energy-efficient building envelopes for Nordic conditions.

Evaluating neighborhood performance is crucial for achieving long-term zero-carbon goals, enabling efficient energy, cost, and resource sharing among buildings. This task requires balancing multiple criteria and managing uncertainties, emphasizing the importance of performance robustness alongside high performance. This article introduces a flexible multi-criteria approach for evaluating neighborhood performance, focusing on greenhouse gas (GHG) emissions and energy use across different life cycle stages. Flytårnet, a Norwegian neighborhood with zero-emission ambitions, serves as a case study. The methodology incorporates the T-robust method, an established robustness-based approach, to select high-performance, resilient neighborhood designs under various uncertainties. Results indicate that when assessing buildings as key components and considering energy delivered during the operational phase, including photovoltaic generation, the supplied energy ranges from 25 to 80 kWh/m²/year. Over a 60-year period, life cycle GHG emissions span from 4 to 12 kg CO₂-eq./m²/year, accounting for uncertainties and encompassing material production and replacement, as well as energy consumption and generation. However, the optimal design choice varies based on whether life cycle stages beyond the use stage are considered. This research provides valuable insights for decision-makers and designers seeking effective neighborhood designs in early-stage planning, considering diverse and conflicting performance criteria to achieve zero-emission goals.