Floor Heating Research Articles

A Review of the Building Heating System Integrated with the Heat Pipe

The heat pipe (HP) is widely applied in the thermal management field at present. In order to make use of the low-grade and renewable energies to maintain building thermal comfort in the heating season, more and more studies with respect to improving the thermal performance of the building heating system integrated with the HP (BHSIHP), such as the floor heating system integrated with the HP (FHSIHP), the thermal storage wall heating system integrated with the HP (TSWIHP), conventional wall integrated with the HP (WIHP) and radiator heating system integrated with the HP (RHSIHP), are conducted. This paper aims to summarize different types of HPs applied in the building heating system and offers an overview of the thermal performance improvement for the BHSIHP. The thermal response, thermal conductivity, thermal resistance, heat capacity, heat transfer coefficient, temperature distribution, thermal storage and heat release capacity are always selected to investigate characteristics of the BHSIHP. Results show that the thermal performance of the FHSIHP, the TSWIHP, the WIHP and the RHSIHP is more outstanding than that of the conventional heating system. The thermal performance of the BHSIHP is affected by heat source temperature, installation tilt angle, working fluid, and filling ratio of the HP. The heat source temperature, which positively affects the performance of the BHSIHP, is crucial for the selection of the working fluid and filling ratio. However, the performance of the BHSIHP is increased first and then decreased with the increase of the installation tilt angle. The optimal filling ratio of the working fluid has been proven not to be a fixed value.

A new approach on the management of landfill leachate reverse osmosis concentrate: Solar distillation coupled with struvite recovery and biological treatment

The management of reverse osmosis (RO) concentrate remains a challenging task for operators of Landfill Leachates Treatment Plants. In this article we suggest an integrated treatment scheme for RO concentrate that combines solar distillation, struvite precipitation to reduce ammonia content of the distillate and biological treatment of the supernatant either with mixed cultures of bacteria or with microalgae. Experiments in a pilot-scale solar still, equipped with underfloor heating system, showed that the production rate of the distillate ranged up to 3.17 L/d m2. The distillate was characterized by elevated average concentrations of ammonium nitrogen; 2028 mg/L and 1358 mg/L in the two experiments conducted, respectively. A decreasing trend on concentrations of NH4+-N was noticed during these experiments, while the opposite was observed for COD. Struvite recovery experiments showed that the optimum Mg:NH4:PO3 ratio was that of 2:1:5.8. Under these conditions, the NH4+-N removal reached 88%. Further treatment of the process supernatant into a 4-L hybrid sequencing batch reactor with biocarriers and activated sludge achieved NH4+-N removal higher than 98% in Phases C and D, where 450 and 600 mL of supernatant were added, respectively. Similar removal was also observed in a 2-L bioreactor with microalgae Chlorella sorokiniana when 150 mL of struvite supernatant were added (Phase B) while further increase of the amount of added supernatant to 200 mL resulted to a sharp stop of NH4+-N consumption (Phase C). Calculations for a landfill serving 20,000 inhabitants and a daily RO concentrate production of 6 m3/d showed that the required area for the construction of the solar still was 1893 m2 and the volumes of the hybrid and the microalgae reactor were 54 m3 and 60 m3, respectively. The recovered solid material of struvite process, after characterization for heavy metals and organic micropollutants, could be reused to the fertilizers industry.

Numerical study using the finite volume method on the thermal and energy performance of a regulated underfloor heating system incorporating PCM in a ventilated room

A physical model is performed to assess the thermal and energetic advantages of using PCM in controlling and regulating the indoor temperature of a ventilated room with an underfloor heating system incorporating a PCM. The heating source is regulated to keep the cavity air temperature in a small interval assuring a certain level of comfort without wasting too much energy. By contrasting our numerical results with numerical data from the literature, the suggested model was validated. Physical processes are solved numerically using computational fluid dynamics by a detailed 2D transient simulation integrating real climatic data of Agadir, Tangier and Casablanca. The simulations carried out justified the suitability of using the PCM with Agadir and Casablanca climate types by a saving of heating power reaching 18.80 % and 17.33 %, respectively.

Performance investigation of a solar-driven cascaded phase change heat storage cross-seasonal heating system for plateau applications

The mismatch between solar radiation resources and building heating demand on a seasonal scale makes cross-seasonal heat storage a crucial technology, especially for plateau areas. Utilizing phase change materials with high energy density and stable heat output effectively improves energy storage efficiency. This study integrates cascaded phase change with a cross-seasonal heat storage system aimed at achieving low-carbon heating. The simulation analyzes heat distribution and temperature changes from the heat storage system to the heating terminal. The results indicate that although the solar collectors operate for 26.3% of the total heat storage and heating period, the cumulative heat stored is 45.4% higher than the total heating load. Heat transferred by the cross-seasonal heat storage system accounts for up to 61.2% of the total heating load. Therefore, the system reduces fuel consumption by 77.6% compared to conventional fossil fuel heating systems. Moreover, radiant floor heating terminals, with a wide range of operating temperatures, match well with cascaded phase change heat storage and can reduce operation time by 19.5% and heat demand by 5.2% compared to conventional radiators. In addition to demonstrating the feasibility of applying cascaded phase change technology in cross-seasonal heat storage heating, this study reveals the lifecycle sustainability due to the shortened heat storage period. The configuration, parameters, and simulation results provide a reference basis for system application and design.

LightGBM-, SHAP-, and Correlation-Matrix-Heatmap-Based Approaches for Analyzing Household Energy Data: Towards Electricity Self-Sufficient Houses

The rapidly growing global energy demand, environmental concerns, and the urgent need to reduce carbon footprints have made sustainable household energy consumption a critical priority. This study aims to analyze household energy data to predict the electricity self-sufficiency rate of households and extract meaningful insights that can enhance it. For this purpose, we use LightGBM (Light Gradient Boosting Machine)-, SHAP (SHapley Additive exPlanations)-, and correlation-heatmap-based approaches to analyze 12 months of energy and questionnaire survey data collected from over 200 smart houses in Kitakyushu, Japan. First, we use LightGBM to predict the ESSR of households and identify the key features that impact the prediction model. By using LightGBM, we demonstrated that the key features are the housing type, average monthly electricity bill, presence of floor heating system, average monthly gas bill, electricity tariff plan, electrical capacity, number of TVs, cooking equipment used, number of washing and drying machines, and the frequency of viewing home energy management systems (HEMSs). Furthermore, we adopted the LightGBM classifier with ℓ1 regularization to extract the most significant features and established a statistical correlation between these features and the electricity self-sufficiency rate. This LightGBM-based model can also predict the electricity self-sufficiency rate of households that did not participate in the questionnaire survey. The LightGBM-based model offers a global view of feature importance but lacks detailed explanations for individual predictions. For this purpose, we used SHAP analysis to identify the impact-wise order of key features that influence the electricity self-sufficiency rate (ESSR) and evaluated the contribution of each feature to the model’s predictions. A heatmap is also used to analyze the correlation among household variables and the ESSR. To evaluate the performance of the classification model, we used a confusion matrix showing a good F1 score of 0.90. The findings discussed in this article offer valuable insights for energy policymakers to achieve the objective of developing energy-self-sufficient houses.

Heating performance of PCM radiant floor coupled with horizontal ground source heat pump for single-family house in cold zones

As the energy demand for space heating increases, the necessity for innovative and energy-efficient heating technologies has become more urgent. This study proposes and evaluates a heating system that integrates a phase change material radiant floor with a horizontal ground source heat pump (PCM floor-HGSHP, Case 1), intending to maintain indoor comfort temperatures and enhance energy efficiency through the utilization of renewable energy sources. Despite the considerable potential of PCM floors, their combination with HGSHP requires further research to fully unlock their benefits. The study involved simulating the PCM floor using a validated TRNSYS component and developing an advanced rule-based control strategy with time-of-use tariffs as a key input to optimize system operation. To elucidate and quantify the advantages of the PCM floor-HGSHP system and verify its applicability in cold regions of China, a single-family house was used as a case study building, four representative cities were selected, and two comparative simulation cases were defined, along with three key performance indicators. The results indicate that, compared with the radiant floor heating system with HGSHP (RFHS-HGSHP, Case 2), the incorporation of PCM in the floor of Case 1 improves the indoor temperature stability by 8.6 %, enhances the load flexibility by 18.1 %, and reduces the total operating costs by 13.8 %. Furthermore, relative to the PCM floor with air-to-water heat pump system (PCM floor-AWHP, Case 3), the proposed system which substitutes the AWHP with the HGSHP, extends the duration of indoor comfort temperatures by 9.6 % and decreases the system electricity consumption by 33.7 %. The proposed system demonstrates excellent thermal and energy performance across all selected cities, proving to be both technically feasible and significantly beneficial for maintaining indoor comfort temperatures and reducing operational costs. This study offers valuable insights and technical support for designing and optimizing residential heating systems in cold regions, thereby promoting the development and application of renewable energy sources.

Indoor Thermal Environment Improvement Based on Switchable Radiation/Convection-Combined Intermittent Heating: Comparison between Conventional Terminals and Integrated Novel Terminal

Intermittent heating is an energy-saving heating mode, which can save energy in terms of time, and thus is worth promoting, particularly in residential heating scenarios. Conventional radiant heating terminals, that is floor heating, and convective heating terminals, that is fan coils, cannot achieve both intermittent and thermal comfort during intermittent heating. Therefore, this study proposes a switchable convective-radiant heating regulation method for floor heating and fan coils to achieve a comfortable indoor environment with high thermal response speed. Furthermore, a novel combined radiant-convective heating terminal was proposed for a reliable and effective solution. Results showed that the proposed switchable method could increase both intermittence and thermal comfort. In addition, the heating terminal showed better heating performance than the combination of two conventional terminals at the key points of heating capacity, flexibility, and thermal response. It could initially heat up a typical residential space within 20–40 min and then stabilize the room temperature in a comfortable range of 18–22 °C, showing great potential for intermittent heating in room-scale heating conditions. This study provides a reference technique for intermittent heating with reduced system complexity and precise environmental control.

Influence of hot water pipe position on the performance of radiant floor heating systems integrated with PCM

To address the slow heating and low efficiency issues of traditional macro-packed phase change material (PCM) radiant floor heating systems, this study innovatively explores the impact of altering the eccentric positions of hot water pipes within the PCM encasement, based on computational fluid dynamics (CFD) numerical simulations. Starting with a concentric case as a baseline, the investigation extends to six different configurations achieved by displacing the hot water pipes vertically (upward and downward) and horizontally. The analysis encompasses the PCM's thermal state, temperature dynamics, spatial distribution, and heat flux. The results indicate that the arrangement of hot water pipes with upward and horizontal displacements demonstrates a more positive impact on improving the thermal performance of the PCM radiant floor heating system, with the effect becoming more pronounced as the displacement distance increases. Cases with upward eccentric movement of r/4 (where r is the encasement radius) and r/2 reached the optimal floor temperature of 297.15 K faster than the concentric case by 2 h and 3.8 h, respectively, during the heating phase. Cases with horizontal eccentric movement advanced by 0.5 h and 2.5 h, respectively. Cases with horizontal displacements of r/4 and r/2 caused smaller temperature fluctuations and provided greater comfort and energy efficiency than those with upward displacements, with average heat flux values being 4.75 % and 11.82 % lower, respectively. These findings offer theoretical support for the optimization and application of macro-packed PCM floor heating systems.

Model predictive controls for residential buildings with heat pumps: Experimentally validated archetypes to simplify the large-scale application

Exploiting the energy flexibility resulting from thermal loads management in buildings is one of the most promising solutions to contribute to the energy transition targets. To offer energy flexibility to the grid, the building should meet the requirements: (i) it needs electrically powered generation (e.g., through Heat Pumps) and (ii) advanced control techniques (e.g., Model Predictive Controls) must be implemented. In recent years, the scientific community has produced many studies demonstrating the potential of Model Predictive Controls combined with Heat Pumps to exploit energy flexibility in buildings. However, a large-scale deployment of such control techniques is still far off, both because of the not yet widespread use of Heat Pumps and the computational challenges involved in implementing them. The aim of this study is to contribute to the deployment of advanced control techniques for Heat Pumps systems in buildings by simplifying their implementation. At this aim, validated archetypes of Model Predictive Controls for Heat Pumps in residential buildings are proposed. The availability of archetypes can greatly facilitate the practical application of Model Predictive Control. In fact, they are adaptable to the characteristics of different buildings and Heat Pump installations and their structure is designed to have an acceptable trade-off between calculation time and prediction reliability. The archetypes cover three different types of heating systems: low temperature radiators without (i) and with (ii) integrated heat storage devices and (iii) underfloor heating system. All archetypes are applied to a real Heat Pump and validated through experimental campaigns. During the experimental test all the archetypes proved to be effective in controlling the real system and the results showed good reliability of the prediction model in the control (for all archetypes a Root Mean Square Error lower than 0.44 °C was obtained) and an optimizer success rate in Model Predictive Controls greater than 91 %. The archetypes proposed are provided as open-source tools that can be reused for similar cases to facilitate Model Predictive Controls implementation in heat pump systems.

Solar energy utilization for underfloor heating system in residential buildings

In this paper, the thermal performance of a solar energy system for heating a residential building is experimentally investigated. In this system, the solar thermal energy is supplied via a flat plate solar collector that provides the heated water into a small-scale chamber, that represents the residential building. The experimental setup is installed in Jouf University campus (Latitude: 29° 47′ 1.9” N, Longitude: 40° 2′ 42.2” E) located at Al-Jouf Province, Saudi Arabia. In this experiment, the hot water supplied from solar collector is mixed with water in the storage tank, then extracted from bottom of the tank to be circulated in a copper tube loop located underneath the floor tiles of the chamber and hence increases the chamber’s air temperature. Two circulation pumps are installed in the system, one to circulate the water between solar collector and storage tank and the other to circulate the water between storage tank and chamber. Measurements of several parameters were conducted to evaluate the overall thermal efficiency of the system. The experimental results showed an average efficiency of 51 %, when operating the system for eight-hours duration in the winter season. Additionally, an economic assessment was carried out to confirm the system’s feasibility. This assessment demonstrated that the constructed system is economically feasible, with an estimated benefit-cost ratio of 1.42.

Smart electroactive self-repairable coating involving end-of-life aircraft prepregs by mechanical recycling

The environmental impact of the Carbon Fiber Reinforced Polymers (CFRPs) industry, particularly due to waste generation during manufacturing and end-of-life phases, is compelling major industrial entities to reconsider a circular economy approach for their materials and to comply with emerging regulations. This study explores the potential of recycled carbon fibers (rCFs) derived from the mechanical recycling of prepreg waste. Mechanical recycling was selected for its cost-effectiveness and moderate environmental impact, recovering short rCFs with lengths below 200 μm. These rCFs, which retain excellent electrical properties, are incorporated into an epoxy matrix with Polycaprolactone (PCL) to create a multifunctional coating with self-healing capabilities. The resulting composite material exhibited significant improvements in electrical conductivity, achieving up to 16.50 S/m, and demonstrated effective Joule effect heating, exceeding 200 °C with 20 V applied for a composite containing 15 wt% rCF. The self-healing efficiency for surface cracks, activated by the Joule effect, reached 80–90 %, resulting in a 99 % reduction in energy consumption compared to conventional oven heating. Notably, the self-healing mechanism was characterized in real-time within a scanning electron microscope for the first time, providing a comprehensive evaluation of the process. This innovative coating offers promising applications in aviation for anti-icing, deicing, and maintenance reduction, as well as in residential settings as an energy-efficient floor heating solution. This research underscores the potential of mechanically recycled CFRPs to produce high-value, sustainable materials, promoting a circular economy and reducing the environmental footprint of the aeronautical sector.

Experimental and Numerical Study of Newly Assembled Lightweight Radiant Floor Heating System

In this study, the heating capacity of a new prefabricated assembled hot water radiant modular heating system made from a recycled waste building masonry structure is investigated through experimental and numerical simulation methods. The heating capacity of the system in different working conditions (a water supply temperature of 48 °C, 51 °C, 56 °C, and 61 °C; a flow rate of 0.49 m3/h, 0.35 m3/h, and 0.21 m3/h) is analyzed and verified. A three-dimensional steady-state heat transfer numerical model of the floor heat transfer of the module is established, and the accuracy of the model is verified through the measured results to investigate the heating capacity of this system under different water supply temperatures, flow rates and coil spacings. The results show that the new prefabricated hot water radiant module heating system has a 0.9 °C higher air temperature and 2.1 °C higher average floor surface temperature than the traditional wet floor radiant heating system under the same experimental conditions, and the response time is 44% shorter. The water supply temperature can significantly change the heating capacity of the system, while the water supply flow rate has little effect on the system. The established three-dimensional steady-state numerical model can be in good agreement with the measured results. This study can provide an experimental and theoretical basis for the design and application of such systems.

Analysis of the non-uniform thermal environment of local floor and ceiling radiant heating: Numerical simulation and thermal comfort experiment

Local radiant heating is a crucial method for avoiding inefficient heating and reducing energy consumption in buildings. To supplement existing research, which primarily focuses on local vertical-wall radiant heating, this paper investigates the non-uniform thermal environment of local floor and ceiling radiant heating rooms under various radiant positions, areas, and temperatures. The study utilizes numerical analysis by Ansys Fluent and thermal comfort experiments in Xi'an, China, which has a Dwa Köppen climate classification. When the local heating zone is located near windows and doors, the radiant film preferentially exchanges heat with them, resulting in a decrease in air temperature and mean radiant temperature. In such cases, it is recommended to increase the radiant temperature or area. With a radiant area of 5 m2 and a radiant temperature of 25 °C, expanding the radiant area to 15 m2 increases the average air temperature in the local heating zone by 5.0 °C, while raising the radiant temperature to 29 °C increases it by 1.4 °C. Moreover, enlarging the radiant area can effectively improve occupants' skin temperature, thermal sensation, and overall thermal comfort. When the radiant area and temperature are determined, priority should be given to local floor radiant heating over local ceiling radiant heating due to its lower air temperature, larger temperature gradients, and smaller mean radiant temperatures. This study aims to provide references for proposing refined design and regulation parameters of local floor and ceiling radiant heating systems in the future.

A method for setting room temperature of district heating in northern China based on local thermal comfort

Currently, the district heating system in northern China primarily employs two types of terminals, namely radiators and radiant floors. The heating design temperature is set for the center of the room without considering local thermal comfort for individuals. As the real thermal environment within buildings is non-uniform, variations in thermal sensation across different parts of the body will affect whole-body thermal comfort. Therefore, it is crucial to prioritize local thermal comfort when setting room temperatures for heating purposes. In this study, we analyzed the data from the chamber experiments and Chinese Thermal Comfort Database, focusing on the district heating environments of residences, office buildings, and university classrooms in severe cold and cold zones. We developed a thermal sensation evaluation model for analyzing the most uncomfortable body part, investigated the lower limit of acceptable air temperature for this specific body part and inferred appropriate setpoint based on both this limit and head-ankle temperature difference. The results indicate that ankles are the most uncomfortable part with an estimated lower limit of acceptable air temperature at approximately 18 °C. Consequently, we recommend setting room temperatures of 20 °C for radiator heating (RH) and 19 °C for floor heating (FH) to ensure ankle thermal comfort. The findings of this study can provide theoretical basis for reasonable settings of heating room temperature for the aforementioned three types of buildings in northern China, thereby further achieving energy conservation.

Impact of dataset sampling period on building thermal models used for flexibility activation

Buildings could help solve the supply and demand mismatch of electricity by providing energy flexibility to the grid. Thermal models of a dwelling are required to properly exploit their flexibility. The first step in developing such models is gathering on-site measurements. The quality of these measurements impacts the performance of the resulting models and, in turn, the harnessed flexibility. This research aims to evaluate the effect of the measurement sampling period on the achieved flexibility in a dwelling. In this paper, flexibility is realized through passive heat storage in the building by using model predictive control. The effect of the dataset sampling period on modeling accuracy and flexibility is evaluated. To assess the impact of the sampling period, four types of modeling techniques are trained by datasets with different sampling periods. The performance of these models for flexibility activation is assessed in two case studies. These case studies have similar structures with the main difference being their heating system. One building is equipped with electric heaters while the other uses underfloor heating. The findings show that decreasing the sampling period below 1 h does not lead to noticeable improvements in energy flexibility. On the other hand, deploying a sampling period larger than 1-h leads to a controller that underperforms. Using a sampling period of 2 h could sabotage the harnessed flexibility up to 51 %.

Assessment of the impact of setting the heating curve on reducing gas consumption in a residential building while ensuring thermal comfort

Due to the large share of the residential building sector in CO2 emissions, it is necessary to look for quick-to-implement and cost-free solutions for heating systems aimed at increasing their efficiency and reducing fuel consumption. The aim of the study is a multi-aspect assessment of the proper setting of the heating curve in the weather controller of a low-temperature floor heating system with a condensing gas boiler, and an analysis of the impact of the heating curve slope on the natural gas consumption, the emission of gaseous and dust pollutants and on maintaining appropriate indoor air parameters: air temperature, operative temperature and PMV and PPD. A wide range of simulation tests were carried out using the TRNSYS software for an existing energy-efficient single-family residential building, with mechanical ventilation with heat recovery, located in north-eastern Poland in Bialystok. Changing the heating curve slope by 0.1 can reduce gas consumption and pollutant emissions by 1.6–10.3 %. Low heating curve slopes may result in failure to reach the temperature set by users (difference between the set and achieved indoor temperature up to 1.9 K), while maintaining standard thermal comfort parameters (−0.5<PMV<+0.5; PPD<10 %). Reducing the indoor air temperature by 2 K can contribute to reducing gas consumption by 11 % while maintaining standard thermal comfort parameters. Changing the heating curve slope is one of the effective methods of reducing fuel consumption in the building. Results are useful for users of buildings equipped with low-temperature heating systems with floor heating and installers of these systems.

Development of a vibration-damping, sound-insulating, and heat-insulating porous sphere foam system and its application in green buildings

With the development of green buildings, people pay more attention to the quality of the indoor sound environment. The air sound insulation performance of floors and exterior walls plays a key role in today's green buildings. The thermal performance of the enclosure structure's floor and exterior wall heat transfer resistance is an important factor in reducing building carbon emissions in green buildings. The aim of this paper is to study the efficiency of the acoustic and thermal insulation of a foaming system with porous carbon balls and the combination of different structural ways of construction boards and external walls. The acoustic and thermal parameters of different sound insulation and thermal insulation systems designed with porous carbon sphere foam and inserted into the floors and exterior walls are compared to highlight the optimal structure. The theoretical and experimental tests showed that to improve the sound insulation performance of the floor, a sound insulation system needs to be placed on the surface of the floor in contact with the impact object and inlaid in the vertical gap in contact with the floor and the wall. Furthermore, it has been determined that the surface of the foam particle acoustic ball with micropores has good sound absorption performance. Finally, the high-quality building thermal insulation material with low thermal conductivity in any combination with the floor slabs and the external wall structure improves the thermal insulation performance.

Assessing the impact of the dataset’s size and quality on building thermal models for energy flexibility

The demand side is required to increase its energy flexibility to tackle the demand–supply mismatch caused by integration of renewable energy sources into the energy mix. Model Predictive Control (MPC) is one of the promising measures for achieving this goal. MPC requires operational data from the building to train its predictive model. The quality of this data affects the performance of MPC. This paper aims to analyze the impact of a dataset’s size and excitation method on flexibility harnessed by MPC. Five datasets have been generated that differ in their size and excitation method. They are used to train three modeling algorithms on two buildings. Next, generated predictive models are integrated into an MPC framework, to assess the impact of datasets on the performance of MPCs for activating the energy flexibility of a building. The case studies are two similar dwellings where one is equipped with Electric Heaters (EH), and the other uses an UnderFloor Heating (UFH) system. Results show that the flexibility of the EH case is more sensitive to the size of the dataset. Furthermore, it is shown that the suitability of the excitation signal for flexibility activation depends on the modeling algorithm. The results show that choosing an ill-suited dataset might cost the MPC 35 % and 20 % of the potential flexibility for EH and UFH cases, respectively.

Investigation of the influence of different room geometries and wall thermal transmittances on the heat transfer in rooms with floor heating

Heat transfer analysis is crucial for precise energy performance estimates in buildings with floor heating systems. However, existing models for predicting heat transfer at wall surfaces often lack accuracy, overlooking realistic room conditions such as corners, edges, thermal bridges, and inhomogeneous wall temperatures, thus compromising energy performance prediction. This research develops more comprehensive correlation models for heat transfer coefficients that incorporate a broader range of realistic room configurations, including room volume, floor aspect ratio, and thermal transmittance of exterior walls—factors rarely explored collectively. This study conducts computational fluid dynamics simulations to analyse the radiative and convective heat transfer and applies thermal boundary layer theory to enhance the understanding of the convective heat transfer at room edges. Results indicate that the convective heat transfer is heavily influenced by changes in thermal boundary layer structures at room edges and depends greatly on the hydraulic diameter assumed for the walls. For the radiative heat transfer, the floor aspect ratio proved crucial. The newly developed models reveal deviations up to 96.5 % from existing ones, highlighting the limited applicability of the existing models. The developed models can enhance the accuracy in predicting the energy performance of buildings with floor heating systems.

Ambient PM2.5, household environment and preterm birth: A birth cohort study in Shandong, China

BackgroundThe associations between fine particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) and risk of preterm birth (PTB) are inconsistent, and the effect of household environment on PTB is largely unclear. AimTo investigate the association of ambient PM2.5 throughout pregnancy, household environmental factors and PTB, with further exploration of their potential interaction and joint effect on PTB. MethodsThe study included 5888 pregnant women between 2018 and 2021 in Weifang Maternal and Child Health hospital of Shandong, China. Maternal exposure to PM2.5 was extracted from ChinaHighAirPollutants datasets according to individual home address. Household environmental information including residential floor level, double-glazed window, heating fuel, cooking, smoking and window ventilation was collected by questionnaires at enrollment. PTB was defined as a birth before 37 completed weeks of gestation. General additive models were applied to examine the associations of PM2.5 exposure, household environment and PTB. ResultsOne-unit increase of PM2.5 throughout pregnancy was associated with significantly increased risk of PTB (OR = 1.069, 95% CI: 1.037, 1.103). In contrast, installation of double-glazed windows (OR = 0.763, 95% CI: 0.589, 0.990) and residential floor level of the 5th floor or above (OR = 0.746, 95% CI: 0.583, 0.955) were found to be associated with significantly reduced risk of PTB. The stratified analyses demonstrated that the protective associations remained among those with high PM2.5 exposure, urban residence, middle SES level and cesarean delivery. A negative interaction between residential floor level and PM2.5 exposure on PTB, and joint effect of installation of double-glazed windows plus residential floor level of the 5th floor or above on PTB were observed. ConclusionsThis study found the adverse effect of PM2.5 during the pregnancy on PTB, and identified protective associations between installing double-glazed windows, living on the 5th floor or above and PTB in relatively polluted regions.