Modular wooden structures for zero-energy buildings represent the future of sustainable construction, combining high energy efficiency with minimal environmental impact. As part of the project “Zero-Energy Building in Modular Construction,” co-financed by the European Regional Development Fund under the Podlaskie Voivodeship Regional Operational Programme for 2014–2020, wall panels were designed for timber frame construction in various geometric and structural configurations. Acoustic and thermal-moisture performance tests were conducted for the proposed solution. This article presents the test results and the conclusions drawn from them.

Acoustic Performance in Zero-Energy Buildings

Acoustic performance is a key aspect of comfort in zero-energy buildings. Acoustic analysis was carried out using the Insul software to determine whether the designed partitions meet the standard requirements. It is worth noting that the program tends to overestimate results; however, if the partition analysis indicates a significant surplus in insulation performance, it can be assumed that it meets acoustic standards.

Acoustic performance tests were conducted on a completed building. The analyzed partitions included inter-story floors, walls between apartments, acoustic walls, exterior walls, and terraces.

Acoustic Test Results and Conclusions

The study showed that most partitions met the applicable standards. The only issue was with a linoleum-covered floor that lacked acoustic layers. Based on these findings, it can be concluded that the building was acoustically well-designed. The use of wood in the construction did not negatively impact the building's sound insulation, highlighting the potential of this material for creating comfortable living spaces.

Thermal-Moisture Analyses of Zero-Energy Building Envelopes

Modular wood constructions use an organic material that is sensitive to moisture combined with high temperatures. Prolonged exposure to such conditions can result in mold growth and decay, potentially leading to the loss of structural integrity in extreme cases. Moreover, mold poses health risks to humans. The more energy-efficient the partition, the higher the risk of such issues, making thermal-moisture analyses essential to ensure the safety of the planned structure.

Thermal-moisture analyses were conducted for all planned building envelope elements, including:

• Exterior wall type A,
• Exterior wall type B,
• Exterior wall with an extension,
• Ground floor in the bathroom,
• Ground floor in the living room,
• Floor on reinforced concrete in the bathroom,
• Floor on reinforced concrete in the living room,
• Two-way ventilated roof,
• One-way ventilated roof,
• Unventilated roof.

The analyses were performed using the specialized WUFI software, which conducts transient calculations of heat and moisture transport in porous materials.

Thermal-Moisture Test Results and Conclusions

The calculations confirmed favorable thermal-moisture conditions for exterior wall type B, the ground floor in the living room, and the reinforced concrete floor in the bathroom. However, the analyses also highlighted areas requiring observation during the building's usage.

• For exterior wall type A, the exterior wall with an extension, and the ground floor in the bathroom, the possibility of unfavorable moisture accumulation at the outer base of the I-beam post was identified.
• For the reinforced concrete floor in the living room, condensation at the interface between mineral wool and polyurethane foam in the underfloor space was noted.
• For the two-way and one-way ventilated roofs, excessive moisture in the plywood under the roof membrane was detected.
• For the unventilated roof, degradation of the sheathing due to decay processes under unfavorable thermal-moisture conditions was indicated.

Real-Time Thermal-Moisture Conditions in the Building Envelope

Thermal-moisture conditions in the building envelope are also monitored in real time. During the construction phase, moisture and temperature sensors were installed in the partitions. Data is continuously recorded in a dedicated system, allowing constant observation of the conditions in the elements and verification of their behavior. Monthly and annual graphs provide comprehensive data on the thermal-moisture conditions across the building. During the first two years, the building envelope tends to reach a dynamic equilibrium, requiring observation over a minimum of five years to validate results.

The building is also equipped with an energy measurement system. Recorded data revealed inefficiencies in the electric heating solutions used and demonstrated the advantages of renewable energy sources—in this case, heat pumps. The data also pointed to a downside of the building, specifically its tendency to overheat during summer months. The low thermal transmittance of the building envelope and good air tightness, combined with the low thermal inertia of the timber frame construction, cause the building to heat up quickly and release heat too slowly. Therefore, the use of zero-energy heat pumps with cooling functions is recommended for future buildings.

Development Prospects for Zero-Energy Buildings

The findings emphasize the importance of integrating renewable technologies into zero-energy buildings. Using heat pumps in modular timber frame constructions will result in energy savings and improved user comfort.

Modular zero-energy buildings require further research to enhance thermal-moisture efficiency, with a particular focus on implementing effective ventilation technologies to reduce the risk of condensation. The conducted analyses underline the immense potential of wood as a primary construction material.