Long-term Indoor Research Articles

A Nonaxial-Type Swirling Cavitating Nozzle for Exploiting Natural Gas Hydrate

Summary Natural gas hydrates (NGHs) have garnered widespread attention in the new energy sector, owing to their efficient and clean combustion properties. NGHs are ice-like substances formed by methane and water under high-pressure and low-temperature conditions, abundantly deposited in seabeds and frozen soil of highlands on Earth. However, the rock shelves of NGH reservoirs are mostly fragile and sparsely colloidal. Traditional mechanical mining methods can easily cause rock-shelf collapses, leading to mining accidents. Long-term indoor experiments and pilot mining projects have shown that cavitating nozzles can provide a feasible solution to the problem of efficient mining of NGHs. To further improve the efficiency of cavitating nozzle mining for NGHs, we have optimized and designed a nonaxial-type swirling cavitating nozzle (NASCN) based on traditional swirling cavitating nozzles (SCNs). Both numerical simulations and indoor experiments have verified the higher mining performance of this nozzle. In the numerical simulation experiments, we analyzed the cavitation performance, erosion performance, and energy consumption characteristics of different cavitating nozzles using the mixture multiphase flow model and the renormalization group (RNG) k-ε turbulence model. In the indoor experiments, we utilized a jet erosion experimental device for NGHs to analyze the erosion effects of different cavitating nozzles on hydrate samples. The results of these experiments indicate that the NASCN reduces energy consumption by 12% compared with traditional nozzles when there is little difference in cavitation performance and erosion performance. Moreover, under similar energy consumption, the NASCN improves erosion efficiency by 35.2% compared with traditional nozzles. These results demonstrate that the NASCN has good application value in the mining engineering of NGHs.

Long-term emission characteristics of VOCs from building materials

Long-term emission behaviors of volatile organic compounds (VOCs) from indoor buildings materials heavily depend on the value of three key parameters (initial concentration C0, diffusion coefficient Dm, partition coefficient K) that govern emissions over time. We made the first attempt to quantitatively explore the variation of parameters through a long-lasting aging test that simulates natural indoor exposure. Over a span of 431 days, we obtained a substantial dataset consisting of ten thousand data points. The parameters of six VOCs (formaldehyde, benzene, toluene, ethylbenzene, o-xylene, p-m-xylene) from three kinds of wood-based boards with different aging intervals were determined. Our findings demonstrate that C0 decreases exponentially with aging time, while Dm and K merely fluctuate with it. With the obtained correlations, ventilation time for renovated house is proposed to meet the WHO standard. These results lay the groundwork for predicting long-term indoor VOC concentrations, which is crucial for indoor air quality pre-evaluation.

Integrating aromatic plants into indoor biophilic environments: Species selection based on psychophysiological effects and bioactive volatile compounds

To explore aromatic plants suitable for indoor biophilic environments and their impact on long-term indoor residents' psychophysiological health, a combined method using subjective ratings, objective electrophysiological signals, and aroma characteristics was employed. The study assessed 12 indoor plants' aromas and analyzed aroma components and their potential to intervene in psychophysiological health. Results showed that different plants had varying effects on psychophysiological health, some (e.g., Vicks Plant, rosemary) showed positive impacts across most measures, while others (e.g., basil, catnip) showed negative impacts. The aroma of false incense showed significant gender differences in its effects. Smelling Vicks Plants for 5 min significantly reduced heart rate (HR), increased heart rate variability (HRV), and enhanced vigor, positively correlated with volatile organic compounds (VOCs) and terpenes like linalool and limonene. Higher VOCs emission was associated with lower HR and reduced anger. Cluster analysis grouped Vicks Plant and rosemary based on aroma composition and effects on psychophysiological responses, providing a basis and framework for subsequent exploration of aromatic plants with psychophysiological regulation capabilities in indoor biophilic environments.

The association between cumulative exposure to PM2.5 and DNA methylation measured using methyl-capture sequencing among COPD patients

BackgroundParticulate matter with a diameter of < 2.5 μm (PM2.5) influences gene regulation via DNA methylation; however, its precise mechanism of action remains unclear. Thus, this study aimed to examine the connection between personal PM2.5 exposure and DNA methylation in CpG islands as well as explore the associated gene pathways.MethodsA total of 95 male patients with chronic obstructive pulmonary disease (COPD) were enrolled in this study. PM2.5 concentrations were measured for 12 months, with individual exposure recorded for 24 h every 3 months. Mean indoor and estimated individual PM2.5 exposure levels were calculated for short-term (7 days), mid-term (35 days), and long-term (90 days). DNA methylation analysis was performed on the blood samples, which, after PCR amplification and hybridization, were finally sequenced using an Illumina NovaSeq 6000 system. Correlation between PM2.5 exposure and CpG methylation sites was confirmed via a mixed-effects model. Functional enrichment analysis was performed on unique CpG methylation sites associated with PM2.5 exposure to identify the relevant biological functions or pathways.ResultsThe number of CpG sites showing differential methylation was 36, 381, and 182 for the short-, mid-, and long-term indoor models, respectively, and 3, 98, and 28 for the short-, mid-, and long-term estimated exposure models, respectively. The representative genes were TMTC2 (p = 1.63 × 10-3, R2 = 0.656), GLRX3 (p = 1.46 × 10-3, R2 = 0.623), DCAF15 (p = 2.43 × 10-4, R2 = 0.623), CNOT6L (p = 1.46 × 10-4, R2 = 0.609), BSN (p = 2.21 × 10-5, R2 = 0.606), and SENP6 (p = 1.59 × 10-4, R2 = 0.604). Functional enrichment analysis demonstrated that the related genes were mostly associated with pathways related to synaptic transmission in neurodegenerative diseases and cancer.ConclusionA significant association was observed between PM2.5 exposure and DNA methylation upon short-term exposure, and the extent of DNA methylation was the highest upon mid-term exposure. Additionally, various pathways related to neurodegenerative diseases and cancer were associated with patients with COPD.ClinicalTrials.gov identifierNCT04878367.

The hidden acceleration pump uncovers the role of shellfish in oceanic carbon sequestration

Whether shellfish mariculture should be included in the blue carbon profile as a strategy to combat climate change has been controversial. It is highly demanding not only to provide calibration quantitation, but also to provide an ecosystem-based mechanism. In this study, we chose mussel farms as a case study to evaluate their contributions to carbon sinks and their responses to sedimentary carbon fixation and sequestration. First, we quantified the air–sea CO2 flux in the mussel aquacultural zone and observed a weak carbon sink (−0.15 ± 0.07 mmol·m−2·d−1) during spring. Next, by analyzing the carbon composition in the sediment, we recorded a noticeable and unexpected increase in the sedimentary recalcitrant carbon (RC) content in the mussel farming case. To address this surprising sedimentary phenomenon, a long-term indoor experimental test was conducted to distinguish the consequences of mussel engagement with sedimentary RC. Our observational data support the idea that mussel engagement promotes accumulation of RC in sediments by 2.5-fold. Furthermore, the relative intensity of carboxylic-rich alicyclic molecule (CRAM)-like compounds (recalcitrant dissolved organic matter (RDOM)) increased by 451.4 % in the mussel-engaged sedimentary dissolved organic matter (DOM) in comparison to the initial state. Mussel engagement had a significantly positive effect on the abundance of sedimentary carbon-fixing genes. Therefore, we definitively conclude that mussel farming is blue carbon positive and propose a new alternative theory that mussel farming areas may have high carbon sequestration potential via an ecologically integrated “3 M” (microalgae–mussel–microbiota) consortium. The “mussel pump” accelerates carbon sequestration and enhances climate-related ecosystem services.

Full tea waste-based photothermal aerogel with vertical water transport channels for steady solar desalination

Interfacial solar desalination technology holds immense promise in combatting global freshwater scarcity. However, salt accumulation on solar evaporators poses a significant hurdle in sustaining desalination performance. Therefore, the development of salt-resistance solar evaporators remains a formidable challenge. Herein, we have exploited a full tea waste-based photothermal aerogel (TWPA) to achieve steady desalination performance. This TWPA is fabricated with carbonized tea waste (TWC) and tea waste fiber (TWF) with a simple crosslinking method and liquid nitrogen freeze-drying. The TWPA efficiently absorbs 97% of sunlight, which results in an exceptional evaporation rate of 1.63 kg m–2 h–1 under 1-solar intensity. Moreover, the vertical water transport channels and large pore structure within TWPA expedite solution transport and salt ion backflow diffusion, ensuring stable desalination of 10 wt% brine at a rate of 1.37 kg m–2 h–1. Long-term indoor and outdoor experiments demonstrate that TWPA is durable. Notably, a 1 m2 TWPA can generate about 6.34 kg freshwater per day from 10 wt% brine. This simple waste-to-treasure approach not only demonstrates a sustainable solution but also promises to drive the development of waste-based solar evaporators, addressing freshwater scarcity while mitigating environmental pollution.

Effects of long-term indoor air purification intervention on cardiovascular health in elderly: a parallel, double-blinded randomized controlled trial in Hong Kong

Ambient fine particulate matter (PM2.5) is a leading environmental risk factor globally, and over half of the associated disease burden are caused by cardiovascular disease. Numerous randomized controlled trials (RCT) have investigated the short-term cardiovascular benefits of indoor air purifiers (IAPs), but major knowledge gaps remain on their longer-term benefits. In this 1-year, randomized, double-blinded, parallel controlled trial of 47 elderly (ntrue-purification = 24; nsham-purification = 23) aged ≥70 years, true-purification reduced household PM2.5 levels by 28% and maintained lower exposure throughout the year compared to the sham-purification group. After 12 months of intervention, a significant reduction of diastolic blood pressure was found in the true-purification versus sham-purification group (-4.62 [95% CI: -7.28, -1.96] mmHg) compared to baseline measurement prior to the intervention, whereas systolic blood pressure showed directionally consistent but statistically non-significant effect (-2.49 [95% CI: -9.25, 4.28] mmHg). Qualitatively similar patterns of associations were observed for pulse pressure (-2.30 [95% CI: -6.57, 1.96] mmHg) and carotid intima-media thickness (-10.0% [95% CI: -24.8%, 4.7%]), but these were not statistically significant. Overall, we found suggestive evidence of cardiovascular benefits of long-term IAPs use, particularly on diastolic blood pressure. Evidence on other longer-term cardiovascular traits is less clear. Further trials with larger sample sizes and long-term follow-up are needed across diverse populations to evaluate the cardiovascular benefits of IAPs.

Composition of indoor organic surface films in residences: simulating the influence of sources, partitioning, particle deposition, and air exchange.

Indoor surfaces are coated with organic films that modulate thermodynamic interactions between the surfaces and room air. Recently published models can simulate film formation and growth via gas-surface partitioning, but none have statistically investigated film composition. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) was used here to simulate ten years of nonreactive film growth upon impervious indoor surfaces within a Monte Carlo procedure representing a sub-set of North American residential buildings. Film composition was resolved into categories reflecting indoor aerosol (gas + particle phases) factors from three sources: outdoor-originating, indoor-emitted, and indoor-generated secondary organic material. In addition to gas-to-film partitioning, particle deposition was modeled as a vector for organics to enter films, and it was responsible for a majority of the film mass after ∼1000 days of growth for the median simulation and is likely the main source of LVOCs within films. Therefore, the organic aerosol factor possessing the most SVOCs contributes most strongly to the composition of early films, but as the film ages, films become more dominated by the factor with the highest particle concentration. Indoor-emitted organics (e.g. from cooking) often constituted at least a plurality of the simulated mass in developed films, but indoor environments are diverse enough that any major organic material source could be the majority contributor to film mass, depending on building characteristics and indoor activities. A sensitivity analysis suggests that rapid film growth is most likely in both newer, more air-tight homes and older homes near primary pollution sources.

Revealing Long-Term Indoor Air Quality Prediction: An Intelligent Informer-Based Approach.

Indoor air pollution is an urgent issue, posing a significant threat to the health of indoor workers and residents. Individuals engaged in indoor occupations typically spend an average of around 21 h per day in enclosed spaces, while residents spend approximately 13 h indoors on average. Accurately predicting indoor air quality is crucial for the well-being of indoor workers and frequent home dwellers. Despite the development of numerous methods for indoor air quality prediction, the task remains challenging, especially under constraints of limited air quality data collection points. To address this issue, we propose a neural network capable of capturing time dependencies and correlations among data indicators, which integrates the informer model with a data-correlation feature extractor based on MLP. In the experiments of this study, we employ the Informer model to predict indoor air quality in an industrial park in Changsha, Hunan Province, China. The model utilizes indoor and outdoor temperature, humidity, and outdoor particulate matter (PM) values to forecast future indoor particle levels. Experimental results demonstrate the superiority of the Informer model over other methods for both long-term and short-term indoor air quality predictions. The model we propose holds significant implications for safeguarding personal health and well-being, as well as advancing indoor air quality management practices.

Polyester fiber bundle-based solar evaporator manufactured by dyeing for efficient desalination and zero liquid discharge

Interfacial solar desalination is a promising technology to address global freshwater scarcity. However, low evaporation rates, complex manufacturing processes, and poor salt resistance have hindered the practical application of solar evaporators. In this study, a three-dimensional (3D) solar evaporator named DB-PFB was developed by dyeing industrial dispersion black (DB) onto polyester fiber bundle (PFB). Vertical channels in the PFB rapidly transport water from the bottom to the top through the wicking effect. This, together with hydrophobic polyester fibers, prevents salt accumulation, ensures stable desalination performance and achieves zero liquid discharge. The 3D DB-PFB can utilize ambient energy and has a stable evaporation rate of about 2.60 kg m–2h−1 for desalination of 20 wt% brine at 1-solar intensity. Continuous evaporation allows the collection of salt crystals and dye wastes in the distillation tank. Long-term indoor and outdoor desalination experiments (about 150 h each) have proven the durability of the DB-PFB. 1 m2 DB-PFB can produce approximately 18 kg of freshwater per day from 20 wt% brine, meeting the daily drinking water needs of six adults. This efficient, easy-to-manufacture, and salt-resistant solar evaporator offers a feasible solution to alleviate global freshwater scarcity.

Performance of a low-cost sensor (LCS) network for long-term indoor and outdoor PM2.5 measurements at rural communities in Beijing, China

Performance of a low-cost sensor (LCS) network for long-term indoor and outdoor PM2.5 measurements at rural communities in Beijing, China

Preliminary Population Exposure to Indoor Radon and Thoron in Dhaka City, Bangladesh

Radon, an element of natural radiation, is considered one of the leading causes of lung cancer worldwide. In Bangladesh, radon has been clarified as a foremost source of radiation exposure. Potential natural-radiation-induced elevated cancer risks were estimated in Bangladesh previously for the population. In this survey, as a very preliminary study in the country, comparative indoor radon (222Rn, Rn) and thoron (220Rn, Tn) concentration/population exposure was determined for the multistoried dwellings of south-western areas of Dhaka city. RADUET was used to assess annual Rn and Tn concentrations in determining the primary inhalation dose for the population. The annual effective dose of Rn and Tn was evaluated in this study for dwellings at 0.3 mSvy−1, constituting a Tn dose contribution of an average of 40% with a dwelling-based wide range of 10–96%. Thus, Tn should not be neglected for Bangladesh while estimating radiological inhalation dose from the indoor environment. Again, the equilibrium factors, F of Rn and Tn, were determined by short-term measurement at averages of 0.6 and 0.02, respectively. Furthermore, using questionnaire estimation by principal component analysis, PCA following the dwelling characteristics, human lifestyles, and estimated long-term indoor Rn and Tn concentrations, this paper discussed indoor atmospheric/Rn factors for the investigated multistoried dwellings in Dhaka city.

Evaluation of ventilation in Australian school classrooms using long-term indoor CO2 concentration measurements

School classrooms are often reported as having insufficient ventilation with elevated indoor CO2 concentrations. This paper reports on pre-pandemic field measurements of CO2 concentration levels conducted for an academic year in 10 classrooms from four primary and a secondary school in Victoria, Australia. Measured CO2 concentrations across the 10 classrooms which were operated with a mix of intermittent natural ventilation and air-conditioning for cooling or heating, on average ranged between 657 ppm and 2235 ppm during school hours with median over 1000 ppm in 70% of classrooms. All 10 classrooms in the study exceeded the Australian recommended limit of 850 ppm. Using average peak CO2 concentrations from year-long measurements, estimated ventilation rate (VR) of 4.08 Ls-1 per person show under-performing classrooms where 60% had VRs 35–40% lower than the 10-12 Ls−1 per person Australian recommendation. Estimated VR range of 1.24–2.07 Ls-1 per person using peak maximum CO2 levels were 19–30% lower than ASHRAE recommendation of 6.7 Ls-1 per person. These VRs translate to a range of air change rates on average between 0.52 and 0.88 h−1 ± 0.26–0.59, well below the 6.0 h−1 recommendation for good indoor ventilation by the World Health Organisation in the context of COVID-19 pandemic. Characterisation of ventilation and indoor air quality in current Australian classroom stock is critical for the improvement of classroom design, induction on room operating practices, understanding of the school community on the relevance of building ventilation on school performance and health, and development of appropriate ventilation and indoor air quality guidelines for schools.

Effect of infrasound on the detectability of amplitude-modulated tonal noise

This study investigated aural detectability of wind farm infrasound and its effects on higher frequency audible tonal noise via creating a sensation of amplitude modulation. The study focused on infrasound pulses with a fundamental frequency at 0.8 Hz and 46 Hz tone which was amplitude modulated at 0.8 Hz. That tone had an amplitude modulation depth between 2 and 12 dB and tonal audibility between 5 and 17 dB. The wind farm noise (WFN) samples were selected from long-term indoor measurement data and were played at an average of 30 dBA or 62 dBG. Forty-eight participants were recruited from four different demographic groups among which some were sleep disturbed by WFN. Participants did not detect the infrasonic content of wind turbine noise above chance, either when analysed in separate groups or overall and this is consistent with previous research. Infrasound reduced the probability of amplitude modulation detection by 2.8% (95% confidence interval 0.2 to 6.1), indicating that inaudible infrasound has a small effect on the audibility of low frequency tonal noise.

Climate chamber investigation of the effect of indoor thermal histories on thermal adaptation in different seasons

The indoor thermal history of residents in the hot summer and cold winter climate zone in China have undergone a significant change in recent years, which also changes their seasonal thermal adaptations and this has formed feed-back effects to the increasing usage of air conditioning units in this area. To study the seasonal variations of thermal adaptation, the thermal comfort experiments were conducted on two groups of participants. Each groups included 20 participants who had indoor history mainly with natural ventilation (NV group) and air-conditioning (AC group), respectively. The results demonstrated that the thermal sensation vote (TSV) in warm environments did not differ between AC and NV subjects in summer. However, the TSV of AC subjects were much lower than that of NV subjects in the same standard effective temperature and skin temperature in a cold environment in winter. Overall, the participants who spent most of their time in AC space in winter showed a low level of thermal adaptation with a narrower acceptable skin temperature range of 32.6 – 33.5 °C. Thus, this study presents the basic information regarding the seasonal effects on human thermal adaptation due to different long-term indoor thermal histories.

Long-term vs. short-term measurements in indoor Rn concentration monitoring: Establishing a procedure for assessing exposure potential (RnEP)

Radon (Rn-222 or Rn) is a naturally occurring chemical element that belongs to the progeny of U-238 released from soil and rocks into the atmosphere, whose impact on organisms is not negligible when it occurs inside confined spaces, such as mine shafts or low-ventilated buildings. The current methodologies for indoor radon assessment are based on passive and active detection. If passive detectors are mainly designed for long-term assessment, active detectors are electronic equipment that can allow on-time visualization of results and, therefore, faster decision-making on risk mitigation measures implementation. However, despite offering a prompt and informed decision, the uncertainty associated with active detector results may cast doubt on the quality of the measurements, which especially arises from the duration of the monitoring campaign. Since radon emanation from soils and rocks depends on a set of variables related to meteorological parameters and soil structure, the seasonal variation of these parameters impacts indoor radon concentration assessment, both on short-term and long-term measurements. Therefore, short-term monitoring campaigns lasting a month, a week, or a day may not produce a statistically representative description of indoor radon exposure for the monitored building. Accordingly, the study compares the reliability of short-term and long-term indoor radon measurements. It proposes a procedure for assessing the indoor Radon Exposure Potential (RnEP) based on in situ measurements through the analysis of the frequency of occurrence of results divided into three classes of potential exposure (low, moderate and high) to reduce occupants' radon risk exposure.

Modelling of Lemna minor L. growth as influenced by nutrient supply, supplemental light, CO2 and harvest intervals for a continuous indoor cultivation

Given the proper conditions, Lemna spp. rapidly produce a high amount of valuable biomass which is considered as an alternative source for feed and food. For a continuous and long-term indoor production under controlled conditions, environmental and harvest parameters have to be optimized to suppress algal growth and constantly yield a high-quality product. Experimentally assessing the effect of a larger number of parameters on the growth rate ri is impossible due to the theoretically high number of parameter combinations. Thus, a SIMILE® - based model has been developed. This enables production parameters to be assessed individually for its effect on the growth rate ri by a differential equation. Start values for numerical integration were taken from measured data and analytical solutions of the differential growth equation. At 400 ppm CO2, the regrowth rate ri in an optimized laboratory set-up amounted to 216 g FM·m−2d−1, harvesting one third of the biomass at intervals of 5 days. In up-scaled set-ups, lower regrowth rates ri of about 173 g FM·m−2d−1 (Kalkar) and 190 g FM·m−2d−1 (Berlin) were obtained, because temperature and light conditions were below optimum. At 3,500 ppm CO2, the regrowth rate ri in laboratory set-up increased to 323 g FM·m−2d−1 by shortening the harvest interval to three days. Maximum growth rates ri were obtained with an NH4+/NO3- ratio of 1/9 at 1.14 mM total N concentration. The results indicate how to optimize culture conditions and harvest intervals. Model runs closely match the experimental data taken from the three different approaches and thus confirm the validity of the model.

Thermal adaptation of different set point temperature modes and energy saving potential in split air-conditioned office buildings during summer

The Chinese government issued a regulation that the cooling set point temperature (SPT) in office buildings cannot be lower than 26 °C. Therefore, SPTs were divided into different modes: SPT≥26 °C and SPT<26 °C. To study the human thermal adaptation of different SPT modes and determine the comfort and energy saving of the policy, a field test and subjective questionnaires were conducted in 21 split air-conditioned (SAC) office buildings during the warm season in the cold zone of China. We measured the environmental parameters and subjects' skin temperatures, and the subjective thermal responses were also investigated. The results showed that 45% of the air conditioner SPTs were less than 26 °C. In the high SPT mode, people's physiological adaptability to the warm environment was stronger, and subjects were more active in reducing clothes and increasing air velocity to improve thermal discomfort. Because the two modes had similar thermal histories and the same perceptual control, in the same SET ranges, no significant differences were found in thermal sensation, acceptability and comfort between the two SPT modes. The effects of long-term indoor thermal history on human thermal adaptation varied with the thermal exposure type, mode and intensity. From the analysis of thermal adaptation, the rationality of the policy was fully proved, and it was determined that SAC office buildings could save 26.4–35.2% of power energy consumption by reasonably increasing SPT in the cold zone. The results can enrich the thermal adaptation theory and provide a theoretical basis for the government's energy-saving policies in SAC office buildings.

Feasibility of low-cost particle sensor types in long-term indoor air pollution health studies after repeated calibration, 2019–2021

Previous studies have explored using calibrated low-cost particulate matter (PM) sensors, but important research gaps remain regarding long-term performance and reliability. Evaluate longitudinal performance of low-cost particle sensors by measuring sensor performance changes over 2 years of use. 51 low-cost particle sensors (Airbeam 1 N = 29; Airbeam 2 N = 22) were calibrated four times over a 2-year timeframe between 2019 and 2021. Cigarette smoke-specific calibration curves for Airbeam 1 and 2 PM sensors were created by directly comparing simultaneous 1-min readings of a Thermo Scientific Personal DataRAM PDR-1500 unit with a 2.5 µm inlet. Inter-sensor variability in calibration coefficient was high, particularly in Airbeam 1 sensors at study initiation. Calibration coefficients for both sensor types trended downwards over time to < 1 at final calibration timepoint [Airbeam 1 Mean (SD) = 0.87 (0.20); Airbeam 2 Mean (SD) = 0.96 (0.27)]. We lost more Airbeam 1 sensors (N = 27 out of 56, failure rate 48.2%) than Airbeam 2 (N = 2 out of 24, failure rate 8.3%) due to electronics, battery, or data output issues. Evidence suggests degradation over time might depend more on particle sensor type, rather than individual usage. Repeated calibrations of low-cost particle sensors may increase confidence in reported PM levels in longitudinal indoor air pollution studies.

Multi-objective integrated BES-CFD co-simulation approach towards pandemic proof buildings

COVID-19 has posed an extraordinary burden to those professionals responsible for properly operating and safely maintaining facilities throughout this disaster. Considering this global pandemic, the common spaces in buildings must be reconsidered to accommodate a future in-presence existence. Governments address human health and safety as the most vital considerations worldwide; thus, Heating, Ventilation, and Air Conditioning (HVAC) designs, airflow patterns, and temperature distribution must all be reconsidered to achieve such healthy circumstances. Based on this, a Building Energy Simulation-Computational Fluid Dynamics (BES-CFD) validated model has been analysed in terms of various HVAC designs. The simulations assessed the proposed solutions in terms of energy-saving, operational CO2 emissions, thermal comfort enhancement, and infection control. The results were closely examined and showed that the Underfloor Air Distribution (UFAD) system generates approximately laminar vertical airflow, reducing the likelihood of indoor infections and viral transmission. Supply air is delivered to the inhabitants’ zone without sacrificing mixing efficiency, ensuring long-term indoor environmental quality. Moreover, the UFAD model proved to be more cost-efficient compared to the Conventional Overhead Distribution (COHD) and has a lower carbon footprint and energy consumption. In terms of thermal comfort, the dynamic simulations showed a noticeable enhancement in PMV. Additionally, the UFAD provides a vertical temperature gradient profile that is sufficiently uniform. Moreover, the integrated DOAS-UFAD systems’ effectiveness was proved through a techno-economic analysis with a Return on Investment of 8.25% and a Payback period of 7.3 years.