Research on Best Solution for Improving Indoor Air Quality and Reducing Energy Consumption in a High-Risk Radon Dwelling from Romania

Abstract

The purpose of this article is the assessment of energy efficiency and indoor air quality for a single-family house located in Cluj-Napoca County, Romania. The studied house is meant to be an energy-efficient building with thermal insulation, low U-value windows, and a high efficiency boiler. Increasing the energy efficiency of the house leads to lower indoor air quality, due to lack of natural ventilation. As the experimental campaign regarding indoor air quality revealed, there is a need to find a balance between energy consumption and the quality of the indoor air. To achieve superior indoor air quality, the proposed mitigation systems (decentralized mechanical ventilation with heat recovery combined with a minimally invasive active sub-slab depressurization) have been installed to reduce the high radon level in the dwelling, achieving an energy reduction loss of up to 86%, compared to the traditional natural ventilation of the house. The sub-slab depressurization system was installed in the room with the highest radon level, while the local ventilation system with heat recovery has been installed in the exterior walls of the house. The results have shown significant improvement in the level of radon decreasing the average concentration from 425 to 70 Bq/m3, respectively the carbon dioxide average of the measurements being around 760 ppm. The thermal comfort improves significantly also, by stabilizing the indoor temperature at 21 °C, without any important fluctuations. The installation of this system has led to higher indoor air quality, with low energy costs and significant energy savings compared to conventional ventilation (by opening windows).

The Relationship between Radon and Geology: Sources, Transport and Indoor Accumulation

“…To accomplish this, pipes and fans are installed beneath the foundation slab to extract the radioactive gas from the soil and release it outside the building. In addition to reducing radon exposure, a sub-slab radon mitigation system can also have additional benefits, such as improving indoor air quality and reducing moisture in the soil, which can prevent health and structural problems [203]. However, installing this system can be a complex and expensive process, depending on the characteristics of the building and soil.…”

Natural and Mechanical Ventilation Concepts for Indoor Comfort and Well-Being with a Sustainable Design Perspective: A Systematic Review

“…Improvement of thermal comfort or temperature control conditions when using MV or HV, especially when hotter or colder outdoor conditions are present [87][88][89][90][91][92][93] Good or better performance of NV in terms of thermal comfort [94,95] Thermal comfort is one of the main drivers of occupants' behavior associated with NV, with the air change rate and windows opening being dependent on outdoor temperature [88,96,97] Necessity of proper design of buildings where NV is planned to be exploited for thermal comfort (architectural elements, windows, openings, orientation, control, etc.) [98][99][100][101] In a Chinese students' dormitory during winter, temperature and humidity decreased to values under 20 • C and 30% after 4 h of night ventilation with ventilation rates of 0.050 m 3 /s and 0.036 m 3 /s, respectively [100] Too low or too high building tightness is associated with condensation risks [96] Too low or too high building tightness is associated with draughts or fluctuating temperature [101] In a temperate continental city of China, humidification was seen as an issue with both NV and MV, and occupants perceived drier conditions with MV [95] In developing countries, comfort range with NV might be larger (14.6-26.3 • C of comfort range found in an Ethiopian case study), allowing to satisfactorily exploit this ventilation technique [94] Thermal comfort, health, and energy savings are the three drivers of ventilation behavior [97] Visual comfort…”

“…Even though their priority is thermal comfort, occupants seem to be more inclined to spend more on energy if healthier environments can be provided [97] The use of MV is associated with better air quality or sweeping effect [87,88,101,103] MV can mitigate air-tightness issues (lowering the radon concentration from 412 Bq/m 3 to 70 Bq/m 3 , and the CO 2 concentration to an average around 760 ppm in a Romanian case study) [87] Table 1. Cont.…”

“…MV can allow for reduction in consumption, due to less windows openings [96] MV can allow for reduction in consumption, due to the use of heat recovery (86% reduction found with respect to NV) [87] NV allows for less demand of energy [91,93,95] NV can be exploited with not extreme temperatures or not too high outdoor PM 2.5 concentration [95] Increase in energy consumption up to 20% found with MV in simulative study performed in Mediterranean climate: NV with night cooling suggested for smaller residential buildings, and MV or HV for larger residential or commercial ones [91] NV can allow for large energy savings in developing countries (wide comfort range in a field study in Ethiopia). Further research suggested to confirm this conclusion [94] Thermal comfort, health, and energy savings are the three drivers of ventilation behavior [97] Feasibility, safety, and life cycle costs need to be preliminary analyzed in the design process [91] Computational Fluid Dynamics (CFDs) simulations used or encouraged by a significant amount of studies, in order to study air movement and comfort induced by NV or HV [89,90,98,99]…”