Building Ventilation Research Articles

Optimizing hybrid ventilation and daylight-linked dimming control for carbon reduction and thermal comfort in a subtropical high-rise office building

The dominant contributors to electricity consumption in existing buildings are air-conditioning and lighting systems. This study aims to optimize hybrid ventilation and daylight-linked dimming control in a subtropical high-rise office building. The objective is to reduce carbon emissions while ensuring thermal and visual comfort. These two strategies can be retrofitted in a typical curtain wall system with vertical windows without encountering any technical limitations. EnergyPlus is used to analyze the impact of these strategies on enhancing thermal comfort and illuminance while achieving electricity savings in the high-rise office building. Based on the typical meteorological year of Hong Kong, using natural ventilation in perimeter zones can reduce the energy use intensity (EUI) by 2.6 to 3.41 % for 30.09 to 34.97 % of total operating hours, depending on window-to-wall ratios (WWRs). Furthermore, daylight-linked dimming control in perimeter zones can reduce EUI by 18.91 % to 21.9 % in the HVAC portion and 8.09 % to 12.25 % in the lighting portion during 91.39 % to 98.28 % of total operating hours. Using daylighting with a high WWR helps reduce 6.31 to 9.21 % in total greenhouse gas emissions. The study also develops a logistic regression model using three climatic variables to predict the natural ventilation status. Overall, the use of daylighting greatly improves the percentage of acceptable predicted mean vote (PMV), with the greatest improvements observed in perimeter zones facing east and west on the middle floors. However, the combined application of both strategies results in a tempered improvement. The novelty of this study lies in providing guidance on suitable WWRs for implementing both strategies to achieve carbon reduction. Moreover, the significance lies in providing a quantitative assessment of how enhanced ventilation and lighting controls contribute to lower carbon emissions while improving thermal comfort.

The Numerical Simulation Study of Pumping Airflow Driven by Wind Pressure for Single- and Multi-Room Buildings

Pumping airflow occurs in single-sided natural ventilation buildings when the openings are located on the leeward side; the direction of airflow through the building then changes periodicity. In order to propose a calculation method of the ventilation rates for single-room buildings and analyze the pumping ventilation for multi-room buildings, the CFD method with an SST k-ω turbulence model was used to conduct numerical simulation in this study, which is verified by other experimental results. Firstly, the qualitative and quantitative characteristics of pumping ventilation were investigated for a single-room building with two openings. The results show that the steady-state method underestimates the ventilation flow rates, and the unsteady-state method captures the microstructures of the flow better. Secondly, the vortex-shedding and indoor airflow oscillation frequencies were analyzed based on transient simulation for a single-room building. It was found that both of them increase with air speed. Then, the factors affecting ventilation flow rates were analyzed. A calculation method for dimensionless ventilation rates is proposed. Finally, the pumping ventilation for a multi-room building was numerically simulated. The ventilation rate for a middle room is greater than that for a corner room, and the ventilation rate for any room in a multi-room building is greater than the single-room building given the same room size and the same incoming wind speed. The findings of this paper are helpful for the design and evaluation of natural ventilation.

Analysis of the benefits of adopting roof sandwich panels integrated with PCM versus PUR to mitigate energy costs and carbon dioxide emissions

The construction industry's thirst for power has skyrocketed on a global scale. A significant amount of this power is used for buildings' heating, ventilation, and air-conditioning needs (HVAC systems), which in turn ensure occupants' comfort. A sustainable future requires more zero-energy or green buildings to meet the massive global energy demand. This study explores the possibility of reducing air conditioning expenses while taking into account various roof systems referring to sheet panels integrated with thermal insulation or a phase change material. Within the context of the current investigation, four sheet panels made of acrylic, aluminium, galvanized iron, and polycarbonate were examined. In addition, aforementioned sheet panels were filled with either polyurethane (PUR) foam insulation or a form-stable phase change material of FS29, an organic and inorganic mixture. In order to ascertain the thermo-physical properties of FS29 PCM (in both its solid and liquid phases), as well as its latent heat, experiments were carried out. According to the findings, the roof with the acrylic PCM integrated roof (ACPIR) succeeds in the best annual air conditioning or energy cost savings (7.90 and 8.18 $/m2/year), the highest carbon emission mitigations (144.15 and 156.44 kg-CO2/year) and the shortest payback period (9 and 8.7 years), for India's composite and warm-humid climatic conditions.

Effect of Roof Design Configurations onNatural Ventilation with an Obstacle Inside the Building Model

Roof shape, roof angle, and internal obstacle are some of the factors that have a substantial impact on building's ventilation performance.However, previous roof ventilation studies havenot considered the influence of internal obstacle which canaffectthe overallbuilding’sventilation performance.Forthis study,CFD was used to studythe effect of roof design configurations on natural ventilation with an obstacle inside the building model. The numerical simulation was carried outbyusing steady RANS equation specifically the Standard k-ε with enhanced wall treatment. A total of 40simulationcases were carried out. The study considered two roof shapes mainly the sawtooth roof and the saltbox roof with varyingroof angle which were 10º, 20º,30º,and 40º. Internal obstacles with various height were further added into the simulation cases. Next, grid sensitivity analysis was carried out using Grid Convergence Index (GCI) and Factor of two of observations (FAC2) analysis was carried outas model verification methodto ensure a reliablesimulationresult. Based on the results, it is found that airflow characteristics such as wind speed, distributionof pressurecoefficient, and flowrate of an isolated building are strongly dependenton the roof shape and roof angle. Next, the dimensionless flowrate(DFR)is measured to be highest with largest roof angle while lowest with smaller roof angle. Furthermore, the DFR of a building with internal obstacle is lower than that without aninternal obstacledue to blockage of incoming air. Moreover, the results showthat the sawtooth roof outperforms the saltbox roof in terms of measured parameter.Finally, the study concluded that an isolated building with higher roof angle and without an internal obstacle leadsto the best dimensionless flowrate throughout the building.

Influence of cross-ventilation cooling potential on thermal comfort in high-rise buildings in a hot and humid climate

The rising cooling energy demand, caused by the increase in global average temperature and the frequency of heat waves, is currently leading to a significant increase in global electricity consumption. Passive cooling strategies, such as ventilative cooling, can provide acceptable indoor thermal comfort with no or minimal energy consumption, offering an alternative to air conditioning systems in buildings. This paper investigates the effectiveness of natural ventilation in an iconic post-modernist high-rise building in India: Charles Correa's Kanchanjunga Apartments. The research, employing CFD simulation paired with building energy simulation, demonstrates how cross-ventilation can improve the ventilative cooling efficiency in buildings, ensuring affordable indoor thermal conditions even in adverse climatic conditions like the Indian one. Thanks to night-time structural cooling, a maximum reduction in the operative temperature of up to 5.3 °C was achieved compared to the scenario without natural ventilation and up to 6.4 °C compared to the outdoor temperature peak on the hottest day. Consistently with the Indian Model for Adaptive Comfort, cross-ventilation ensures a reduction in discomfort hours of up to 58 % on the hottest day and a total reduction in discomfort hours on a typical monsoon and winter day. The paper aims to assist architects and policymakers in quantifying the cooling potential of natural ventilation in high-rise buildings, suggesting passive solutions for cooling energy saving.

Design and analysis of earth-air heat exchanger integrated into the building ventilation system

This experimental study intent to design and to analyse the passive cooling effect of an Earth-Air Heat Exchanger (EAHE) integrated into the building ventilation system. For hot climate regions, ground thermal inertia can be used as a passive cooling strategy in the building ventilation where the air supply comes from outside with hot temperature. The proposed EAHE device consists of two main-components; a water tank and a PVC hose as a heat-exchanger between air and water in the tank. Fresh air from outside with a flow rate of 5.63 kg. min-1 is blown through a 2 ½-inch PVC hose, and cooled by the low water-soil temperature before being distributed into the room. To analyze the effectiveness of the passive cooling effect, measurements are performed for several parameters; inlet and outlet air temperature of ventilation ducts and indoor-outdoor air temperature using a multichannel thermocouple data logger for 48 hours of measurement time. The results present that the EAHE device can reduce the air temperature to a maximum of 10.6 °C. This proposed EAHE device presents good performance as a passive cooling technique for a building ventilation system, especially during the day.

Design and Development of IoT-based Temperature and Humidity Monitoring System for Thermal Comfort Evaluation in Classrooms

In the learning process in the classroom thermal comfort greatly affects the attitude and performance of students who are doing learning. However, in fact, when students are carrying out the learning process experience some obstacles that make them not feel comfortable in the classroom such as feeling the room temperature is too hot or the room temperature is too cold. Indonesian National Standard sets the air temperature for thermal comfort of the tropics which can be divided into (1) Cool comfort, between the effective temperature of 20.5 ° C - 22.8 ° C, (2) Optimal comfort, between the effective temperature of 22.8° C - 25.8 ° C, (3). Comfortably warm, between an effective temperature of 25.8°C - 27.1°C. While the relative air humidity that is comfortable for humans ranges from 30%60%. The purpose of the temperature and humidity monitoring system is to monitor temperature and humidity conditions that can be used to determine whether the room is in a comfortable condition or not. In this study, the reference used is the 2001 Indonesian National Standard on Procedures for Designing Ventilation and Air Conditioning Systems in Buildings.

Building Ventilation Optimization Through Occupant-Centered Computer Vision Analysis

Abstract Buildings consume about 40 % of all energy. Ventilation plays a significant role in both the energy consumption of buildings and the comfort of occupants. To achieve energy efficiency and comfort, smarter ventilation control algorithms can be employed, such as those with feedback based on CO2 levels. Furthermore, by knowing the current number of people in a space, ventilation can theoretically be adjusted to maintain a constant CO2 level without wasting energy when people are not present. An additional benefit of such control could arise due to occupants’ habits. For example, if a person senses elevated CO2 levels, even if the ventilation system has started operating more intense, they might choose to open a window, potentially compromising energy efficiency. Therefore, if the control algorithm were to maintain a constant CO2 level, occupants may be less likely to open windows. In our work, we explore a model in combination with a custom monitoring system based on computer vision to implement such control. The monitoring system combines outside and inside CO2 sensors with precise people counting based on computer vision to provide data to the model. The model relies on the mass balance equation for CO2 and considers the historical data of the number of occupants and their activities to estimate the overall CO2 generation in indoor spaces. The results suggest that the model can effectively forecast CO2 dynamics with an absolute deviation of 40 ppm. However, it was observed that the analysis of the actual air exchange level could be compromised by several factors.

In-use conditions of air-tightening materials applied in the air gap of ventilated building envelope constructions: A parametric study for different European climates

Materials used in the building envelope have to withstand a wide range of varying and harsh conditions over their life cycle. Particular relevance falls upon the materials used for tightening buildings, such as wind barriers and tapes, as air infiltration was found to be responsible for between 10 and 30 % of heat losses of different national building stocks in Europe. However, there is large uncertainty about the conditions a material is exposed to over a building’s service life. A validated, hygrothermal model of a zero emission office building in Trondheim, Norway was simulated with 10-year climate files from different European locations: Bergen (NO), Berlin (DE), Oslo (NO), Paris (FR), Rome (IT), Tromsø (NO), and Trondheim (NO). This was done to investigate the temperature and humidity conditions in the ventilated air gap. The results show the total and median values for temperature in the ventilated air gaps of the simulated building’s walls and roof for the investigated locations. Moreover, the maximum change compared to the previous hour and the distribution of hours in 5 °C temperature and 10 % relative humidity intervals of the roofing underlay and wall to the west are reported.

Exploring the Implementation Path of Passive Heat-Protection Design Heritage in Lingnan Buildings

To achieve indoor thermal comfort via natural ventilation, traditional buildings in South China’s Lingnan region have evolved distinct features tailored to the hot and humid climate conditions, involving site planning, function layout, and construction techniques. This study delves into the influences of these features on aspects such as sun-shading, ventilation, and heat insulation. By analyzing over ten Lingnan buildings in both the traditional and modern forms, several representative standardized models have been developed. Through a hybrid approach of combining qualitative and quantitative methodologies, including simulations, quantifications, and comparisons, several passive heat-protection measures commonly employed in Lingnan buildings were examined and evaluated. The effectiveness of shading, ventilation, and heat insulation in both traditional and modern buildings was assessed, resulting in the compilation of design principles for passive heat protection in buildings located in similar climatic zones. Key findings include (1) Shading: traditional methods reduce sunlight by 54.55%, while modern buildings enhance shading by applying new materials; (2) ventilation: traditional design achieves an outdoor wind speed of 1.5 m/s, improving thermal comfort, while modern Lingnan buildings optimize these principles; (3) insulation: traditional techniques maintain indoor temperatures below 26.0 °C, and modern buildings introduce innovation solutions for improved thermal insulation. In summary, traditional Lingnan design effectively addresses the challenges of the hot and humid climate by employing passive strategies for thermal comfort. Modern Lingnan buildings, in turn, preserve these principles while introducing innovative approaches.

A hybrid control strategy for frequency regulation with variable refrigerant flow air conditioning system

Heating, ventilation and air conditioning (HVAC) systems of buildings are abundant sources for the Frequency Regulation (FR) ancillary service, whose actuating devices are controlled to follow the real-time power reference signals with the contractual capacity. For HVAC practice, model-based FR controls are hindered by expensive model acquisition. This paper presents a two-layer control strategy for HVAC systems to perform energy efficient FR service, with a rather low model requirement. At the lower level, the FR operation with a selected actuator is realized with a sliding mode control which is robust to power map variation. At the higher level, system efficiency is optimized in real time via a model-free constrained extremum seeking control (CESC). A conceptual variable refrigerant flow (VRF) system is used as the illustrative application, for which the outdoor unit fan offers the FR power reference tracking with SMC. At the outer loop, the compressor discharge pressure is adjusted by a CESC to minimize the total power consumption while the zonal temperature regulation is reinforced as equality constraint. The proposed strategy is evaluated with simulations on a Modelica simulation, and the results validate its effectiveness. The Net Energy Cost can reduce by 15% to 23% under different load levels.

Health care support systems for informal settlement rental housing during the COVID-19 season: landlord’s perspective

PurposeThis paper aims to examine landlords’ health support systems to tenants to control COVID-19 in selected informal settlement rental housing (ISRH) in Ghana, dwelling on landlords’ views.Design/methodology/approachThe paper used the concurrent imbedded mixed-methods approach and grounded the findings in the socio-ecological theory. The authors collected both qualitative and quantitative data from 242 landlords in 13 informal settlements across Ghana using quotas. The authors undertook semi-structured face-to-face and telephone interviews. The authors conducted content and thematic qualitative data analysis and used simple descriptive statistical data analysis.FindingsThe paper discovered that tenants had limited knowledge on the transmission of the pandemic, forcing landlords to regulate their building services usage, ventilation and thermal control, entertainment, common areas and rent advancement for tenants to control the pandemic. Also, tenants found it difficult to comply with the rules on ventilation for fear of criminal attacks, while high social connection and interaction among renters and inadequate enforcement caused the non-adherence by renters to social gathering. Again, landlords had difficulty in contract-tracing visitors suspected to be infected with the virus.Originality/valueThe use of concurrent and imbedded mixed methods to investigate landlords’ viewpoints on their support in health needs of their tenants to regulate COVID-19. The prescriptions from the study provide practical applications to formulate a mix of housing and health policies to formalize the support of landlords to their tenants in ISRH in Ghana.

Calibrating subjective data biases and model predictive uncertainties in machine learning-based thermal perception predictions

Heating, Ventilation, and Air Conditioning (HVAC) systems in large-scale buildings often struggle to ensure satisfactory thermal comfort for diverse occupants while minimizing energy waste. Achieving this goal requires developing reliable prediction models that capture the changing and varied occupant thermal perceptions in different spaces. Despite their widespread use, many machine learning (ML) based prediction models suffer from subjective data biases and model predictive uncertainties, causing inaccurate estimation for occupant needs and leading to suboptimal building controls. The authors propose a data-model integration method that identifies and calibrates the inherent uncertainties of existing ML models in both data and model dimensions, ensuring reliable thermal perception predictions. This method introduces the Multidimensional Association Rule Mining (M-ARM) algorithm to identify biased human responses by exploring interrelationships among four perception metrics: thermal sensation, comfort, acceptability, and preference. Our method reveals significant performance enhancements in seven ML models, enhancing the F1-score by up to 5.53%. By leveraging reliability diagrams and Expected Calibration Error (ECE) scores, we also expose the models’ vulnerability to miscalibration and the need for calibrated predictions. We further evaluate six calibration techniques (e.g., Platt Scaling and Isotonic Calibration) on these models and uncover their potential to enhance prediction reliability performance, highlighting a reduction of up to 80.66% in ECE scores. The authors also investigated the impacts of dataset sizes, classifiers, and calibration methods on the proposed method. Our research offers insight into creating robust data-driven strategies for thermal perception predictions, ultimately contributing to optimized occupant comfort and energy efficiency in buildings.

Some features of air pollution monitoring as a component of the microclimate of the premises

The quality of living space largely depends on the quality of indoor air. The physical and chemical properties of the air people breathe can affect their health and comfort. Indoor air pollution in residential and workplace environments can occur due to various activities of occupants or employees, such as cooking, smoking, and using electronic devices, as well as emissions of pollutants from building materials and the use of certain products. Pollutants that can be present indoors include carbon monoxide, formaldehyde, volatile organic compounds, particulate matter, aerosols, biological contaminants, and more. To effectively monitor the quality of atmospheric air, it is necessary to determine the main sources of air pollution, which is the purpose of this study. Naturally, the quality of indoor air cannot be clearly separated from the ambient air quality. The first factor affecting the microclimate is the level of air pollution near the building. Air from the street enters the room through windows, doors, or the building's ventilation system. If the state of the surrounding environment is unfavorable, the concentration of harmful substances indoors may also exceed the norm. However, indoor sources of air pollution in any building can have a much greater impact on the health and comfort of the people inside it. Materials used in construction, such as concrete or mineral insulation, may contain ammonia, formaldehyde, and other substances that are released from building structures over time and deteriorate indoor air quality. Ensuring control and monitoring of indoor air quality is an extremely important task. This includes measuring concentrations of pollutants and identifying their sources. It is also important to adhere to standards and recommendations developed by health and environmental organizations to ensure safety and comfort indoors. To reduce indoor air pollution, various measures can be implemented, such as selecting appropriate building materials, and ventilation, installing purification systems, controlling sources of pollution, and limiting the impact of human activity. Keywords: air pollution, microclimate parameters, air quality monitoring, harmful substances.

Energy consumption behaviors and the potential of natural ventilation emission reduction in residential building

ABSTRACT China is the largest Carbon Emissions country in the world. The data analysis and simulation of the sampled residential buildings reveals that there exists a large gap between the monitoring data and energy simulation. Based on the thermal comfort theory, we further explored the relationship between the energy consumption behaviors of residents and building ventilation emission reduction. This study constructed a questionnaire to analyze the use habits of existing residential buildings and equipment. The results show the range of suitable outside temps. In this paper, the findings of the survey were combined with the probability of summer outside temp range profiles to derive the thermal comfort satisfaction of the sample population. In the summer high temperature environment, natural ventilation can help to reduce indoor temperature and reduce the concentration of pollutants in the indoor air, thereby improving indoor air quality and reducing energy consumption. The findings can evaluate the emission reduction potential of natural ventilation. The study provided directions for the implementation of low carbon natural ventilation in residential buildings: natural ventilation can be used to reduce residential energy consumption and carbon emissions, reducing the need for mechanical ventilation. This enables environmentally friendly and sustainable buildings and uses renewable energy sources such as solar and geothermal energy as an energy supply. In addition, the study examined the emission reduction potential of natural ventilation measures in the summer temperature range of 26°C to 28°C, which could reduce carbon dioxide emissions by 1.61 kg per square meter.

Investigation of the effectiveness of top-down natural ventilation of a poultry building in a hot-summer mediterranean climate

In this study, computational fluid dynamics (CFD) was used to examine the efficiency of ventilation and airflow patterns in a multi-level layer hen house. The utilization of windcatchers as a natural ventilation system was the main area of focus. By comparing CFD simulations with experimental data using ANSYS Fluent, the results were validated. The findings showed good agreement in airflow velocity within the windcatchers and throughout the entire building between the CFD calculations and the experimental tests, resulting in uniform airflow distribution and the absence of turbulence in the area where the chickens were kept. This setup provided the layer hens with an acceptable level of comfort by maintaining a consistent and steady temperature profile. The windcatcher-based model demonstrated better temperature uniformity than mechanical window ventilation. The study also emphasized the importance of maintaining appropriate humidity levels throughout the building to ensure the comfort and productivity of layer hens. The advantages of the windcatcher-based system in terms of temperature distribution and airflow control were highlighted by comparison with an alternative ventilation model. These results underscore the importance of using natural ventilation systems, such as windcatchers, to create optimal ventilation conditions and provide layer hens with a comfortable and productive environment (resulting in a temperature reduction from 29°C to 19.85°C with a low and uniform air velocity ranging from 0 m/s to 0.7 m/s at cage level). Practical application An effective and eco-friendly approach to enhance animal health and productivity in poultry farms is to install a natural ventilation system with wind collectors. This setup creates optimal conditions for the animals by improving air quality, regulating temperature, and fine-tuning ventilation. Additionally, it promotes overall sustainability in poultry facilities by lowering energy costs and advocating for environmentally friendly management, aligning agricultural practices with stringent environmental standards.

Optimizing indoor air quality: CFD simulation and novel air cleaning methods for effective aerosol particle inhibition in public spaces.

In contemporary building ventilation, displacement and mixing ventilation demand high air volumes for rapid virus elimination, resulting in elevated energy consumption. To minimize the spread of viruses and decrease energy consumption for ventilation, this study employed CFD to explore the efficacy of a downward uniform flow field in impeding the transmission of aerosol particles in a high-traffic public facility, like a supermarket. The findings indicate that the downward uniform flow field proves insufficient when individuals remain static for extended periods. A wind speed of 0.1 m/s or higher becomes essential to overpower the stationary thermal plume, which disrupts this flow field. In areas with human presence, however, this technique is found to be particularly efficient since mobile heat sources do not generate a fixed thermal plume. A 0.05 m/s downward uniform flow field can settle 90% of particles within just 22 s. This flow pattern contributes to the swift settling of aerosol particles and effectively diminishes their dispersion. Employing this flow pattern in public places with increased foot traffic, like supermarkets, can lower the risk of contracting novel coronavirus without augmenting energy consumption. In order to implement the flow field in a part of the domain, a new air purification device is proposed in this study. The device combined with shelves can optimize the flow field uniformity through the MLA (PSO-SVR) algorithm and alteration of the air distribution structure. The uniformity of the final flow field increased to 0.925. The combination of data-driven MLA with CFD showed good performance in predicting the flow field uniformity. These findings offer valuable insights and practical applications for the prevention and control of respiratory diseases, particularly in post-epidemic scenarios.

Hybrid ventilation in residential and office buildings

This project is focused on hybrid ventilation systems, a combination of natural and mechanical ventilation in residential and office buildings. Especially in dwellings hybrid ventilation systems are quite common. For instance, this can be the frequently occurring combination of exhaust fans in bathroom and toilet and / or a range hood in the kitchen with window ventilation in the other rooms. Currently, these systems are part of the planning reality, however, there are neither planning aids nor focused building standards available. A recently completed research project documents the state of the scientific knowledge, identifies most common planning challenges, and thus provides the basis for future planning aids for hybrid ventilation. This paper sets out to define the term “hybrid ventilation”, presents the most common hybrid ventilation systems in Switzerland and gives planning guidelines for current components of hybrid ventilation systems.

Impact of architectural design strategies on the indoor natural ventilation of public residential buildings in Singapore

The architectural design pattern of the public residential buildings developed by Housing and Development Board (HDB) of Singapore has evolved gradually throughout the past decades. However, the fact is that although the new generations of HDB blocks built in recent years are designed to be modernized, the usage of air-conditioning has been increasing in comparison with the old generations. This study aims to investigate the ventilation performance of HDB blocks built in different generations from a historical view. By conducting computational fluid dynamics (CFD) simulations on five typical blocks built in different generations, the area-weighted wind velocities in various rooms of the target units were obtained. The effects of design factors on wind velocity ratio (VR) in corresponding spaces were analyzed and compared. The results show that the old generations with parallel plan layouts generally facilitate cross-ventilation while the new generations with centralized plan layouts usually generate single-sided ventilation which is more sensitive to incoming wind direction. Meanwhile, the window-to-wall ratio and shading depth of the studied facades were validated to have positive and negative relations to the VRs respectively. Though the correlations are insignificant, they show significant disparities between the scenarios under different incoming winds.

Indoor air temperature and relative humidity measurements in Finnish schools and day-care centres

Indoor air temperature and relative humidity measurements of schools and day-care centres in two research projects on indoor air conditions in municipal buildings with mechanical ventilation in Finland were combined for a large sample of occupied spaces with typical conditions experienced by users of the buildings. In addition to user experience, the occupied spaces represented the spaces with determining air humidity load when assessing moisture performance of envelope structures. Indoor air temperature was stable excluding extreme external conditions that caused crossings of limit values. Permanence within limit values of the Finnish Classification of Indoor Environment was inadequate leaving all buildings in the lowest classification level S3. Mechanical ventilation in municipal buildings is designed to keep pollutants at moderate level during high occupancy which results in non-existent indoor air moisture excess, which during winter leads to low indoor air relative humidity. Although dry indoor air provides safety of envelope structures, the drawback is poor performance with regards to the recommended range. Dry indoor air has negative effects on the indoor air quality experienced by the users, causing skin and eye irritation.