The energy required for the heating and cooling of buildings is strongly dependant on the thermal properties of the construction material. Cement mortar is a common construction material that is widely used in buildings. The main aim of this study is to assess the thermal properties of cement mortar in terms of its ther­mal conductivity, heat capacity and thermal diffusivity in a wide range of grades (cement: sand ratio between 1:2 and 1:8). As there is insufficient information to predict the thermal conductivity and diffusivity of a cement mortar from its physical and mechanical properties, the relationships between thermal conductivity and diffu­sivity and density, compressive strength, water absorption and porosity are also discussed. Our results indicate that, for a cement mortar with a 28-day compressive strength in the range of 6–60 MPa, thermal conductivity, specific heat and thermal diffusivity are in the range of 1.5–2.7 W/(m.K), 0.87–1.04 kJ/kg.K and 0.89–1.26 (x10^-6 m²/s), respectively. The scanning electron microscope (SEM) images showed that pore size varied from 18 μm to 946 μm for samples with different cement-to-sand ratios. The porosity of cement mortar has a signifi­cant effect on its thermal and physical properties. For this reason, thermal conductivity and thermal diffusivity was greater in cement mortar samples with a higher density and compressive strength.

It is widely recognised that the carbon dioxide (CO₂) concentration level inside a building is a reflection of the indoor air quality in that building. In most buildings, occupants are a major source of CO₂ through exhalation. It is generally accepted that the concentration of CO₂ varies with location (horizontal and vertical) within an enclosed space and this can impact on the variation of indoor air quality within the space. Hence, measurement errors related to CO₂ sampling strategies in a space are important as they can lead to uncertainties in the mean concentration for the space. The aim of this paper is to investigate existing measurement practices and sampling locations and how these influence the CO₂ concentrations monitored in buildings. To identify the work done in CO₂ measurement practice and determine the current limitations in establishing representative locations for CO₂ concentration in buildings, two main approaches were used: (i) an extensive literature review of existing knowledge from peer reviewed articles and other relevant documents (database); (ii) the use of questionnaires to identify reported measurements with CO₂ sensors as representation of research methods applied by professionals and research organisations. The findings show that most researchers (based on the database and questionnaires analysed) prefer heights between 1.0 m to 1.2 m in the middle of an occupied zone as a representative location. This compares to the recognised breathing zone height of between 0.75 m to 1.8 given in the literature surveyed.

In most buildings, occupants are the main source of indoor carbon dioxide (CO₂) due to exhalation. Although CO₂ is not considered to pose serious health risks to occupants, elevated levels of CO₂ may serve as an indicator of insufficient ventilation. This study examines how CO₂ is distributed within a complex indoor environment of a classroom and how this distribution is affected by different parameters. Measuring CO₂ concentrations at a single location or height may not act as a true representation of an entire space, unless it is measured in a very small confined space. In this study, it was observed that higher CO₂ concentration values can be found at higher levels in a room and not only at a height between 1 m and 1.2 m as claimed by many researchers. Therefore, if CO₂ concentration levels vary significantly, deviations from the average measured values could become large. It was also found that the CO₂ concentration reflects the dynamic relationship among the occupants, their activity levels and occupancy periods. The findings present a useful contribution for future researchers to efficiently and strategically design experimental set ups with well-organised positioning of sensors for CO₂ monitoring purposes.