A theoretical adaptive model of thermal comfort – Adaptive Predicted Mean Vote (aPMV)

This paper presents in detail a theoretical adaptive model of thermal comfort based on the “Black Box” theory, taking into account factors such as culture, climate, social, psychological and behavioural adaptations, which have an impact on the senses used to detect thermal comfort. The model is called the Adaptive Predicted Mean Vote (aPMV) model. The aPMV model explains, by applying the cybernetics concept, the phenomena that the Predicted Mean Vote (PMV) is greater than the Actual Mean Vote (AMV) in free-running buildings, which has been revealed by many researchers in field studies. An Adaptive coefficient (λ) representing the adaptive factors that affect the sense of thermal comfort has been proposed. The empirical coefficients in warm and cool conditions for the Chongqing area in China have been derived by applying the least square method to the monitored onsite environmental data and the thermal comfort survey results.     

A personalized measure of thermal comfort for building controls

A personalized measure for thermal comfort has been applied for use in combination with smart controls for building automation. Using data from a field study, we first show the superiority of personalized measures for thermal comfort compared to standard non-adaptive methods. Based on this knowledge we describe a methodology, using logistic regression techniques, to convert user votes to a probability of comfort. We also describe the interface used to collect the votes. We show that, for a given subject, our thermal profile converges against the probabilities found in the field study. As a case study we implemented the measure in a control algorithm to control the shading devices. The results clarify the mode of action and also show the effectiveness of the method.     

Parametric study on the performance of green residential buildings in China

The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which are compared with simulated results of various scenarios of “energy efficiency” strategy and “healthy housing” environmental control. First, the simulated results show that the adaptive thermal comfort of indoor environment control is actually balanced in terms of occupancy, comfort, and energy efficiency. Second, adaptive thermal comfort control can save more energy for heating or cooling than other current healthy housing environmental controls in China's HSCW zone. Moreover, a large proportion of energy use is based on the subjective thermal comfort demand of occupants in any building type. Third, the building shape coefficient cannot dominate energy savings. The ratio of the superficial area of a building to the actual indoor floor area has a significant positive correlation with and affects the efficiency of building thermal performance.     

On the unification of thermal perception and adaptive actions

Occupants exercise adaptive actions in response to discomforting environmental stimuli in an attempt to restore their comfort. These responses to adaptive actions are either ignored (conventional PMV models) or handled in an aggregated way (adaptive thermal comfort models). Furthermore the availability of adaptive actions and their effectiveness tends to be particular to a given building and climatic context. A good model should predict the probability with which available adaptive actions will be exercised and the feedback to occupants’ perceived comfort from these specific actions. In this paper we introduce a new modelling framework which does just that.     

Adaptive thermal comfort in the residential buildings of north east India—An effect of difference in elevation

Thermal comfort standards are required not only to ensure good indoor climatic condition, but also to optimize the energy used in a building for heating or cooling purposes. Generally, Fanger’s Predicted Mean Vote–Predicted Percentage Dissatisfied (PMV–PPD) model is used by designers and architects to estimate the comfort condition and hence the setpoint temperature inside a building. However, the recent field survey based studies on adaptive thermal comfort suggests that the above used PMV model frequently either underestimates or overestimates the thermal sensation due to the non-inclusion of the adaptive opportunities that a subject may have in maintaining comfortable condition. This leads to often an estimation of higher or lower setpoint temperature than that actually required for maintaining comfort, thereby consuming higher energy. The aim of the research is to study the effect of difference in elevation which is a major factor for temperature difference in hilly terrain, on the thermal comfort of residents. We conducted a field survey in 6 residential buildings at two different elevations in the Darjeeling Himalayan Region of north east India. A total of 1017 questionnaires regarding the indoor occupant thermal comfort were collected from 46 subjects during the monthly survey held in the year 2015. Variations in clothing insulation and other thermal comfort parameters were seen both with difference in elevation and with outdoor environmental conditions.     

Using results from field surveys to predict the effect of open windows on thermal comfort and energy use in buildings

Windows are one of the major means by which building occupants control the indoor environment. This research uses results from field surveys to formulate a method for simulation of office buildings to include the effects of window opening behaviour on comfort and energy use. The paper focuses on: (1) what is general window opening behaviour? (2) how can we frame an “adaptive algorithm” to predict whether windows are open? (3) how can the algorithm be used within a simulation to allow the effects of window opening on comfort and energy use to be quantified? We have found that: (1) the proportion of windows open depends on indoor and outdoor conditions, (2) logistic regression analysis can be used to formulate an adaptive algorithm to predict the likelihood that windows are open, (3) the algorithm when embedded in simulation software provides insights not available using more usual simulation methods and allows the quantification of the effect of building design on window opening behaviour, occupant comfort and building energy use.     

A nodal thermal model for photovoltaic systems: Impact on building temperature fields and elements of validation for tropical and humid climatic conditions

This article deals with both an experimental study and a numerical model of the thermal behaviour of a building whose roof is equipped with photovoltaic panels (PV panels). The aim of this study is to show the impact of the PV panels in terms of level of insulation or solar protection for the building. Contrary to existing models, the one presented here will allow us to determine both the temperature field of the building and the electric production of the PV array. Moreover, an experimental study has been conducted in La Reunion Island, where the climate is tropical and humid, with a strong solar radiation. In such conditions, it is important to minimise the thermal load through the roof of the building. The thermal model is integrated in a building simulation code and is able to predict the thermal impact of PV panels installed on buildings in several configurations and also their production of electricity. Basically, the PV panel is considered as a complex wall within which coupled heat transfer occurs. Conduction, convection and radiation heat transfer equations are solved simultaneously to simulate the global thermal behaviour of the building envelope including the PV panels; this is an approach we call ‘integrated modelling’ of PV panels. The experimental study is used to give elements of validation for the numerical model and a sensitivity analysis has been run to put in evidence the governing parameters. It has been shown that the radiative properties of the PV panel have a great impact on the temperature field of the tested building and the determination of these parameters has to be taken with care.     

Thermal comfort and gender: a literature review

This review examines scientific literature on the effect of gender on indoor thermal comfort. Gender differences have been generally considered to be small and insignificant but this review shows that a growing number of studies have found significant differences in thermal comfort between the genders. Clearly more than half of the laboratory and field studies have found that females express more dissatisfaction than males in the same thermal environments. Very few studies have found males to be more dissatisfied than females. A meta-analysis shows that females are more likely than males to express thermal dissatisfaction (ratio: 1.74, 95% confidence interval: 1.61-1.89). However, most studies found no significant difference in neutral temperatures between the genders. Females are more sensitive than males to a deviation from an optimal temperature and express more dissatisfaction, especially in cooler conditions. PRACTICAL IMPLICATIONS: We should no longer neglect the more rigorous requirements that females have for indoor thermal environments. Gender differences indicate that females have, on average, a greater need for individual temperature control and adaptive actions than males. The results of this review suggest that females should primarily be used as subjects when examining indoor thermal comfort requirements, as if females are satisfied it is highly probable that males are also satisfied.     

Comparison of thermal comfort algorithms in naturally ventilated office buildings

With the actual environmental issues of energy savings in buildings, there are more efforts to prevent any increase in energy use associated with installing air-conditioning systems. The actual standard of thermal comfort in buildings ISO 7730 is based on static model that is acceptable in air-conditioned buildings, but unreliable for the case of naturally ventilated buildings. The different field studies have shown that occupants of naturally ventilated buildings accept and prefer a significantly wider range of temperatures compared to occupants of air-conditioned buildings. The results of these field studies have contributed to develop the adaptive approach. Adaptive comfort algorithms have been integrated in EN15251 and ASHRAE standards to take into account the adaptive approach in naturally ventilated buildings. These adaptive algorithms seem to be more efficient for naturally ventilated buildings, but need to be assessed in field studies. This paper evaluates different algorithms from both static and adaptive approach in naturally ventilated buildings across a field survey that has been conducted in France in five naturally ventilated office buildings. The paper presents the methodology guidelines, and the thermal comfort algorithms considered. The results of application of different algorithms are provided with a comparative analysis to assess the applied algorithms.     

Behavioural adaptation and the use of environmental controls in summer for thermal comfort in apartments in India

Building energy use in India is rising phenomenally. Indian codes prescribe a very narrow comfort temperature range (23-26 °C) for summer. Ventilation controls alone consume 47% of total energy in residences. Thermal comfort field studies in Indian residences were not attempted. The author conducted a field study in apartments in Hyderabad, in summer and monsoon seasons in 2008. This paper presents the occupants’ methods of environmental and behavioural adaptation and impediments in using controls.Only about 40% of the occupants were comfortable in summer due to inadequate adaptive opportunities. The comfort range obtained in this study (26.0-32.5 °C), was way above the standard. Fanger's PMV always overestimated the actual sensation.The occupants used many adaptation methods: the environmental controls, clothing, metabolism and many behavioural actions. Use of fans, air coolers and A/cs increased with temperature, and was impeded by their poor efficacy and noise, occupant's attitudes and economic affordability. A/c and air cooler usage was higher in top floors. Behavioural adaptation was better in summer and was restricted in higher economic groups always. Thermal tolerance was limited in subjects using A/cs and resulted in “thermal indulgence”. This study calls for special adaptation methods for top-floor flats.     

Thermal comfort for naturally ventilated houses in Indonesia

For naturally ventilated buildings (NVB) located in the tropical regions, thermal comfort (TC) prediction based on predicted mean vote (PMV) standard has shown some deviations from the observed results. Hot and humid environmental conditions throughout the year and personal adaptation could have an effect on expectation and perception about TC. Through an extensive field survey conducted in residential buildings in Indonesia, 525 sets of data had been gathered. The data analysis revealed that the PMV equation had predicted warmer thermal perception as compared to what people actually felt. Interestingly, it was observed that under hot and humid tropical climate, people indicated preference to cooler environment as compared to what the neutral temperature has shown. The study also investigated the occupant’s adaptive control preferences in creating a more thermally comfortable living environment. The reciprocal effects of occupant’s thermal perception and behavioural adaptation were explored. In tropical free-running buildings where the air temperature and humidity might not be modified easily without mechanical means, the people seemed to prefer higher wind speed.     

Assessment of Portuguese thermal building legislation in an energetic and environmental perspective

The aim of this study is to assess the consistency of Portuguese thermal building legislation in terms of energy and environmental performance.To illustrate this, a case study has been carried out for different scenarios of a dwelling home located in an extreme climate zone (I3, V1 north) in Portugal with a T3 typology: four occupants and net floor area of 150 m², modelled according to Regulation Thermal Performance Characteristics of Buildings and a Life Cycle Assessment approach.The results show that the Portuguese thermal building legislation can be considered consistent in terms of energy efficiency and environmental performance if we take the damage categories into account - “human health” or “ecosystem quality” or the impact category - “emission into air”. It cannot be considered consistent if we take the damage category into account - “resources” or the impact category - “CO₂ eq” (equivalent carbon dioxide emissions)/“climate change”/“global warming”.     

Inaccuracy in Legionella tests of building water systems due to sample holding time

Most Legionella culture tests are performed on building water samples that have been shipped to analytical laboratories for analysis. Significant (≥1 log₁₀ unit) changes in results were observed in 52% of held samples (6 h or longer, ambient temperature) drawn from building water systems in a 42-sample initial survey. It was not practical to use the spread plate protocol for on-site “t = 0” cultures in a larger, more diverse survey of thousands of building water systems. Two thousand four hundred twenty-one (2421) building water samples were split for on-site analysis using a field culture protocol and then also cultured after overnight shipment to the lab for analysis with the standardized spread plate method. Legionella test results from building water system samples are usually interpreted as ≥a numerical detection or action limit. Therefore, binary statistical analyses were calculated by setting t = 0 culture results to “true”. Overall in this survey, 10.4% of water samples sent to the laboratory for analysis returned either false-positive or false-negative results. The overall positive predictive value of results was poor (36%). Most (83%) false-positive results were returned from utility water systems. Most (74%) false-negative results were returned from potable water systems. These inaccuracies have serious implications in regard to interpretation and use of Legionella test results. The overall negative predictive value of results was excellent (99%) and also it was good (92%) for results from a polymerase chain reaction (PCR) assay that can be therefore used as a negative screening method.     

Thermal performance study and evaluation of comfort temperatures in vernacular buildings of North-East India

Solar passive techniques are being used in vernacular buildings throughout the world. Researchers have done extensive study on thermal performance of vernacular buildings in the different parts of the world. Vernacular architecture of North-Eastern India represents the principle of climate-responsive architecture, which still lacks experimental validation and quantitative analysis. Thermal comfort not only makes the occupants comfortable but also governs energy consumption in the building. Detailed field studies on thermal performances of typical traditional vernacular dwellings in different bioclimatic zones have been undertaken. This field study includes detailed survey of 150 vernacular dwellings, field tests and thermal sensation vote of 300 occupants on ASHRAE thermal sensation scale. Field test includes measurement of temperature, humidity, illumination level and building design parameters. Thermal performances of these vernacular dwellings were evaluated for winter, pre-summer, summer/monsoon and pre-winter months of the year 2008. This evaluation is based on ‘adaptive approach’, which is the outcome of the field studies and is now part of ASHRAE standard 55/2004 for predicting comfortable temperature of naturally ventilated buildings. This study also tried to find out the range of comfort temperature in these vernacular buildings for different season of the year. It has been found that these vernacular dwellings perform quite satisfactorily except in the winter months and the occupants feel comfortable in a wider range of temperature.     

An investigation into thermal comfort in the summer season of Ghadames,Libya

This paper reviews the results from a field survey of thermal comfort within two types of buildings; old (traditional) and new (contemporary), in Ghadames oasis in Libya. The survey was undertaken in the summer seasons 1997 and 1998, which were typical of the hot–dry climate of North Africa. It shows how the 237 residents responded to the environmental conditions. Questionnaires were collected from the residents of 51 buildings: 24 old buildings that employ natural ventilation systems with courtyards and 27 new buildings that employ air-conditioning systems. In addition the environmental parameters were measured in 11 buildings (5 old, 6 new) representing 50 subjects, to calculate the predicted mean vote value of the subject using Fanger’s model as presented in ISO 7730 standard 1995. The survey has shown that the measurements of predicted mean vote (PMV) in new air-conditioned buildings provide satisfactory comfort conditions according to ISO 7730 and the occupants agree by indicating a satisfactory actual mean vote (AMV). The equivalent measurements and survey results in old traditional buildings indicated that although the PMV, based on measurements and ISO 7730, implied discomfort (hot), the occupants expressed their thermal satisfaction with the indoor comfort conditions. The field study also investigated occupants’ overall impression of the indoor thermal environments; the results suggest that people have an overall impression of higher standard of thermal comfort in old buildings than in new buildings.     

Thermal comfort in naturally ventilated buildings: revisions to ASHRAE Standard 55

Recently accepted revisions to ASHRAE Standard 55—thermal environmental conditions for human occupancy, include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings during summer and in warmer climate zones. The ACS is based on the analysis of 21,000 sets of raw data compiled from field studies in 160 buildings located on four continents in varied climatic zones. This paper summarizes this earlier adaptive comfort research, presents some of its findings for naturally ventilated buildings, and discusses the process of getting the ACS incorporated into Standard 55. We suggest ways the ACS could be used for the design, operation, or evaluation of buildings, and for research applications. We also use GIS mapping techniques to examine the energy-savings potential of the ACS on a regional scale across the US. Finally, we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.     

A new and innovative look at anti-insulation behaviour in building energy consumption

This paper presents the findings of a case study with building simulation using EnergyPlus dynamic thermal simulation software, in which wall insulation was varied together with cooling set-point temperature in a hot and dry climate of Botswana. Against the established norm that adding wall insulation reduces annual fuel consumption, it is shown in this paper that this is not always the case: there are instances where adding wall insulation directly increases annual fuel consumption. Initial cost of insulation aside, as the cooling set-point temperature is gradually increased, the building switches from an “insulation reduces cooling load” to an “insulation increases cooling load” behaviour. In other words, the well established knowledge that “the lower the u-value the better” gets overridden by “the higher the u-value the better”. We termed this a “point of thermal inflexion”. Simple graphical demonstration of the existence of this point is presented in the paper. According to the findings, design engineers and building economics related professionals who quantify investment on insulation can get disastrous results if they assume that all buildings behave pro-insulation since a building may behave anti-insulation.     

Determination of strategic adaptation actions for public housing in Singapore

Although building adaptation finds it significant in combating building deterioration and delivering building sustainability, what level of adaptation a building shall receive always seems puzzling to property portfolio managers. This research aims to provide policy makers with a theoretical approach to choose strategically desired adaptation actions for buildings. Personal interviews with policy makers in Singapore public housing sector gave rise to the construction of an Attribute-Action database; this database was used to derive an Attribute-Action Matrix, which consists of a set of preference values for each adaptation action (i.e. retaining, renovating and rebuilding). This approach was then applied to a real public residential building in Singapore. The results show that the total preference values for the actions of retaining, renovating and rebuilding are 157.849, 111.609, and 90.575, respectively; the action of retaining with minor maintenance of building facades is found to be the most desired adaptation strategy for the case building, because compared with the other two, retaining has the maximum total preference value. The presented approach would therefore extend the understanding of how strategic adaptation actions can be made for existing buildings that require adaptation. Lessons learnt in Singapore public housing context may be useful for many other cities in face of similar problems.     

In situ measuring and evaluating the thermal resistance of building construction

This paper introduces an in situ measuring method for the thermal resistance of buildings, including the test chamber, measuring points’ arrangement, and measurement results, in Nanjing during 2000 and 2001. Three methods for the analysis of in situ data are also presented to determine the thermal resistance of buildings although the R-values evaluated by these methods have smaller values than those of design due to the limitation of field conditions. The synthetic temperature method only requires measuring the heat flow rate on the inside surface of the building construction and both the synthetic indoor and outdoor temperatures. And the surface temperature method just requires testing the heat flow rate on the inside surface of building envelopes and both the inside and outside surface temperatures of building construction. However, the frequency response method introduced in this paper only relates to the mean synthetic indoor and outdoor temperatures and the average inside surface temperatures of the building envelopes. In other words, it is not involved with the heat flow rate, which is difficult to measure. Thus, on this point, the frequency response method is better than the other two methods to evaluate the in situ R-value of buildings.     

Wind tunnel experiments modelling the thermal effects within the vicinity of a single block building with leeward wall heating

A wind tunnel model aiming to simulate the thermal effects within the vicinity of a building with leeward wall heating was set up. The work was conducted within the scope of the European ATREUS project (http://aix.meng.auth.gr/atreus) in which micro-scale numerical models were used to obtain data concerning the microclimatic conditions within the vicinity of buildings [A.M. Papadopoulos, N. Moussiopoulos, Towards an holistic approach for the urban environment and its impact on energy utilization in buildings: the ATREUS project, J. Environ. Monit. 6 (2004) 841-848]. This data was then used as input data for generating typical weather data required as input for building and heating, ventilation and air-conditioning (HVAC) system models in order to study the energy budgets of buildings and assess the performance of air-conditioning (A/C) systems. However, it was first necessary to validate these microscale numerical models for a simplified case under different thermal conditions. A series of wind tunnel experiments were conducted in which the mean velocity and temperature field within the vicinity of a single block building (a cube) with leeward wall heating were measured. The ratio of Grashof number to the square of Reynolds number, Gr/Re² was used to model thermal effects within the vicinity of the model, but some compromises were needed in order to obtain a practical model while at the same time fulfilling the objectives of the task set. Conditions representative of mixed and forced convection were modelled. Results showed some degree of flow modification within the recirculation region of the model for both Gr/Re²∼0.9 and 1.6, the recirculation length in both cases being shortened when compared to the non-heated case. The velocity field influenced the temperature distribution within the recirculation region. There was a rapid temperature drop away from the surface, with the temperature distribution reaching near ambient conditions within one model height downstream of the heated face for Gr/Re²∼1.6. In spite of the restrictions applied to the physical model, the technique applied showed very good stability and repeatability during the entire measurement campaign producing a reliable data set for the validation of the microscale numerical models.