The variable refrigerant flow air-conditioning system is an HVAC system that can perform at a high capacity with low consumption thanks to its variable-speed compressor. The paper introduces a TRNSYS model to build a simulation model to calculate the energy performance of an existing variable refrigerant flow system and to build a model that can be used as a reference when a VRF system is proposed to a certain situation. The TRNSYS model was compared with the actual energy consumption to see the data agreement between the two models. Temperature, Relative Humidity, and energy consumption were metered using proper instruments, and it was compared with the obtained simulation results. The validation of the simulation model showed close values to the actual system, as the obtained Normalized Mean Bias Error (NMBE) between the simulation and measured values for temperature and relative humidity was 4.3 and 7.6%, respectively. While it was around 7.8% for the total energy consumption. Besides, the paper proposed an Energy Recovery Ventilation to be simulated with the existing TRNSYS model to compare it with the same system without ventilation to see if it is feasible to add an Energy Recovery Ventilation unit to the existing system. It shows a worthy reason to be used, as it saves 18.8% annually of the energy consumption of the system.

The usage of energy recovery ventilation units was extended in European countries. Air-to-air heat and energy recovery is an effective procedure to reduce energy consumption of the ventilation air. However, the material of the core significantly influences the performance of the exchangers, which is becoming an extremely important aspect to meet the energy requirements of nearly zero-energy buildings. In this study, the performance of two counter-flow heat/enthalpy energy exchangers are experimentally tested under different operating conditions, and the values of the sensible, latent, and total effectiveness are presented. Moreover, the effects of the material of two exchangers (polystyrene for the sensible heat exchanger and polymer membrane for the energy exchanger) on the energy consumption of ventilation in European cities with three different climates (in Reykjavík in Iceland as a cold climate, in Budapest in Hungary as a temperate climate, and in Rome in Italy as a warm climate) are evaluated. The results show that the energy recovery of ventilation air with a polymer membrane material-based counter-flow energy exchanger performs better than using a polystyrene sensible heat recovery unit.

Reducing energy usage to save the environment is one of the main goals for the future. The energy losses in ventilation have a huge impact on energy consumption in buildings. In this work, the energy performance of a heat recovery wheel system equipped in an air handling unit was tested year-round, and the results compared with the simulation output for the system using TRNSYS software. The selected conditioned space was the staff offices of an H&M fashion shop, located in Eger, Hungary. Temperature, relative humidity, and air velocity sensors were placed at the wheel inlet and outlet sections to record data and determine the annual energy saving. The results revealed a good agreement between the measured and simulated results.

Transpired solar collectors (TSCs) preheat ventilation air and reduce conductive heat loss through the building envelope, thereby acting as dynamic insulation. Direct outdoor comparisons of glazed and unglazed TSC modules operating under identical conditions remain limited. A systematic experimental study was conducted on two façade-mounted modules with the same perforated galvanised-steel absorber and 110 mm plenum: an unglazed TSC (UTSC) and a glazed TSC (GTSC) fitted with 4 mm low-iron tempered glass. The system was tested outdoors in Amman, Jordan, under clear-sky conditions (January-March 2025) at specific airflow rates of 18–144 m ³ /(h·m ² ) and solar irradiance of 200–1000 W/m ² . Passive natural-convection operation of the GTSC was also evaluated at several cavity heights. Performance was quantified using physically bounded metrics covering thermal performance, heat exchange, exergy, wall heat-loss recapture, ventilation load reduction, and economic return. Across the tested range, the GTSC achieved thermal efficiency of 48–75% and exergy efficiency up to 12%, outperforming the UTSC (42–65%) by 6–9% points. The UTSC wall heat-loss recapture index decreased from 93% at low irradiance to 63% at peak irradiance, consistent with dynamic-insulation behaviour, while GTSC ventilation load reduction increased monotonically from 60% to 90%. Under passive operation, the GTSC reached 55% efficiency at 3.0 m cavity height without fan energy. Economic assessment using Jordanian energy prices indicated payback periods of 4.4 years (UTSC) and 5.2 years (GTSC). The results provide experimentally grounded guidance on when glazing is justified for sustainable ventilation preheating in buildings.