Indoor Temperature Variations Research Articles

Experimental study on thermal behavior of a building structure using rubberized exterior-walls

Addition of scrap-tire pieces into cementitious composites improves their thermal insulation performance. Development of such construction materials with lower thermal transmittance reusing these wastes is a challenging issue since it provides a combined solution for today's energy saving and environmental pollution concerns. In favor of this, recent European Union directives have brought quiet strict limits to reduce energy consumption and landfill disposal of solid wastes. A model room whose exteriors are fully made with scrap-tire added concrete is built here to increase its thermal protection. A standard/conventional room at identical dimensions but surrounded by ordinary concretes is also built to examine influence of scrap tire addition on room's thermal protection. Long-term thermal behaviors of these two rooms are investigated and compared under real atmospheric environments. Their indoor temperatures reveal that addition of scrap tire pieces lowers both indoor temperature variations and the effect of outdoor conditions. As an example, mean values of yearly thermal time lag are found to be 3.28 and 2.96 h, respectively for the rooms built with and without using scrap tire pieces, corresponding to nearly 11% improvement in thermal protection. Results in overall verify that scrap tire addition improves thermal protection of the room and it is a cost effective solution for people with low income and/or individuals living in rural areas.

Indoor temperature variations resulting from solar desiccant cooling in a building without thermal backup

The performance of a once-through solar desiccant cooling system, for air-conditioning a commercial office space, was modelled using the TRNSYS computer simulation software package. The study particularly focused on the potential for designing and operating a desiccant cooling system, without any thermal backup provided to mitigate for intermittent solar availability in three Australian cities. Increasing (i) indirect evaporative cooler effectiveness, (ii) air flow to the office space, and (iii) solar collector area were all shown to reduce the frequency of high temperature events inside the building occupied space. In the warm temperate climate of Melbourne (and to a lesser extent Sydney), high ventilation rates enabled comfort conditions to be maintained at or near acceptable levels in the occupied space, without the use of a backup thermal source. The synergy between evaporative cooling and solar desiccant cooling, observed in the warm temperate climates, was not evident in the tropical Darwin climate, suggesting that the selected ventilation desiccant cooling cycle is not appropriate for tropical climates.

THERMAL PERFORMANCE AND ENVIRONMENT EVALUATED FROM THE FLUCTUATION OF INDOOR TEMPERATURE AND HUMIDITY IN WINTER

Heat and insulation capacities were evaluated by a regression analysis between the indoor-outdoor difference of temperature and the coefficient of variation of indoor temperature coupled with the way of living. Airtightness and ventilation were evaluated by a regression analysis between the indoor-outdoor difference of temperature and that of absolute humidity. The thermal performance in 5 houses with patients of atopic dermatitis was compared using the procedures described above. Absolute and relative humilities were extremely low in one patient house that had highfrequency ventilation.

Energy saving strategies in air-conditioning for museums

In the museum environment a strict thermal-hygrometric control is necessary primarily for the correct artwork conservation and then for the visitor thermal comfort. Considering that the air-conditioning system has to operate constantly, suitable techniques permit to obtain useful energy savings, allowing, however, a good dynamic microclimatic control. In this paper a case study is presented about various strategies used to reduce energy requirements for HVAC systems in an exhibition room of a modern museum. Using the dynamic simulation code DOE 2.2 and typical climatic hourly data sets, the annual energy use for an all-air system has been calculated, as well as the savings obtainable using different techniques, such as dehumidification by adsorption (desiccant wheel – saving equal to 15% with respect to a base configuration), total energy recovery from the relief air (passive desiccant – 15%), outdoor airflow rate variation (demand control ventilation – 45%). Moreover, the correspondence has been analyzed between the energy request and the admitted variation of indoor temperature and relative humidity: changing the admitted indoor RH range from 50 ± 2% to 50 ± 10%, energy savings around 40% have been obtained. As regards the thermal-hygrometric performance, an optimal control of temperature has been guaranteed with all the configurations, while the best performance in RH control has been obtained with the desiccant system. Considering a simple payback analysis, if the artworks preserved in a museum are particularly sensitive to indoor humidity variation, a desiccant system should be properly used; on the contrary, when the indoor humidity control is not strongly needed, the use of a HVAC system with demand control ventilation is advisable, because of the lowest payback value. The system with total energy recovery presents intermediate features.

Study on preparation of montmorillonite-based composite phase change materials and their applications in thermal storage building materials

Three composite phase change materials (PCMs) were prepared by blending butyl stearate, dodecanol and RT20 with an organically modified montmorillonite (MMT), respectively. After the three composite PCMs were characterized by DSC, it was indicated that the RT20/MMT composite PCM was a good candidate for building applications due to its large latent heat, suitable phase change temperature and good performance stability. Compared with RT20, the RT20/MMT composite PCM exhibited higher heat transfer efficiency and had good compatibility with gypsum due to the combination with MMT. The composite gypsum boards containing RT20/MMT composite PCM had the function of reducing building energy consumption by reducing the indoor temperature variation, and the function was enhanced with the increase in the mass ratio of the RT20/MMT composite PCM.

Impact of Indoor Heating on Painted Wood - Monitoring the Altarpiece in the Church of Santa Maria Maddalena in Rocca Pietore, Italy

Triangulation laser displacement sensors were applied to the continuous in-situ monitoring of the dimensional response of the wooden altarpiece in the Church of Santa Maria Maddalena in Rocca Pietore, Italy, to variations in indoor temperature and relative humidity (RH) between December 2002 and March 2005. Further, a small inductive sensor was used to monitor the width of a crack in one of the elements. The measurements demonstrated that only the external layer of wood, several millimetres thick, continually absorbs and releases water vapour following external variations in RH. For massive elements, this leads to gradients in the moisture content through the wood, a restraint of the dimensional change and a development of stress, which is the main threat to the integrity of the wood and the decorative layer. Particularly strong RH variations and related high stress levels were produced by the intermittent heating system based on the inflow of warm air. To incorporate requirements for preservation, heating systems must provide a localized comfortable temperature in the area occupied by people without changing the natural climate of the church as a whole.

Estimation of Minimum Ventilation Requirement of Dairy Cattle Barns for Different Outdoor Temperature and its Affects on Indoor Temperature: Bursa Case

In the study, 10 different dairy cattle barns with natural ventilation system were investigated in terms of structural aspects. VENTGRAPH software package was used to estimate minimum ventilation requirements for three different outdoor design temperatures (-3, 0 and 1.7 degrees C). Variation in indoor temperatures was also determined according to the above-mentioned conditions. In the investigated dairy cattle barns, on condition that minimum ventilation requirement to be achieved for -3, 0 and 1.7 degrees C outdoor design temperature and 70, 80% Indoor Relative Humidity (IRH), estimated indoor temperature were ranged from 2.2 to 12.2 degrees C for 70% IRH, 4.3 to 15.0 degrees C for 80% IRH. Barn type, outdoor design temperature and indoor relative humidity significantly (p < 0.01) affect the indoor temperature. The highest ventilation requirement was calculated for straw yard (13879 m3 h(-1)) while the lowest was estimated for tie-stall (6169.20 m3 h(-1)). Estimated minimum ventilation requirements per animal were significantly (p < 0.01) different according to the barn types. Effect of outdoor esign temperatures on minimum ventilation requirements and minimum ventilation requirements per animal was found to be significant (p < 0.05, p < 0.01). Estimated indoor temperatures were in thermoneutral zone (-2 to 20 degrees C). Therefore, one can be said that use of naturally ventilated cold dairy barns in the region will not lead to problems associated with animal comfort in winter.

Determinants of winter indoor temperatures in low income households in England

The objective of this study is to quantify the extent to which variation in heating season indoor temperatures is explained by dwelling and household characteristics and increased by energy efficiency improvements in low income households. A survey of dwellings in the Warm Front home energy efficiency scheme was carried out in five urban areas of England. Half-hourly living room and main bedroom temperatures were recorded for 2–4 weeks over two winters. For each dwelling, regression of indoor on outdoor temperature was used to obtain estimates of daytime living room and night time bedroom temperatures under standardized conditions (outdoor temperature of 5 °C). The results indicate that the median standardized daytime living room temperature was 19.1 °C and the median standardized night time bedroom temperature 17.1 °C. Temperatures were influenced by property characteristics, including its age, construction and thermal efficiency and also by the household number of people and the age of the head of household. Dwellings that received both heating and insulation measures through the Warm Front scheme had daytime living room temperatures 1.6 °C higher than pre-intervention dwellings, night time bedroom temperatures were 2.8 °C higher. Warm Front energy efficiency improvements lead to substantial improvements of both living room and bedroom temperatures which are likely to have benefits in terms of thermal comfort and well-being.

The influence of the zone's indoor temperature settings on the cooling/heating loads for fixed and controlled ventilation

In this study, the thermal performance and the energy requirements of a building single-zone are investigated for both the cooling and heating seasons by employing a thermal-network model. The model has six primary heat-flow paths, in order to take into account the position of insulation in the building envelope, and two secondary paths for the ventilation and the cooling/heating unit. The desired indoor temperature of the zone is defined by a pair of preset points of a thermostat. The energy demands and the resulting indoor temperature variations are determined for fixed ventilation as well as for temperature-controlled ventilation. Computer results for both seasons show how the combined influence of slab structure formations, the desired indoor temperature and ventilation control affect the cooling and heating loads.

Contribution of indoor exposed massive wood to a good indoor climate: in situ measurement campaign

An indoor climate is mainly influenced by factors including heating, ventilation and air-conditioning, building envelope and materials, occupants, furniture, and service life of the building components. These last few years, the usual porous medium provided in wall and flooring constructions have been pointed out as possible passive systems capable of buffering the indoor climate variations in terms of temperature and humidity. The objective for the ongoing project is, therefore, to evaluate the possibility of ensuring an indoor climate within an acceptable range making use of large exposed massive wood surfaces. An experimental study, being performed in four occupied apartments of a multi-storey residential building in Sweden, is described in this paper. A brief analysis of the in situ recordings is also included. The temperature and relative humidity recordings show fairly well-agreement with the ASHRAE recommended values for a good indoor climate excepted during the cold periods revealing low indoor relative humidity. The first results show evidences that a large area of exposed massive wood contributes to buffer the indoor temperature variations. Furthermore, this far it does not shows evidences that a large area of exposed massive wood is able to damp the daily fluctuations in relative humidity.

Weather, clothing and thermal adaptation to indoor climate

The adaptive thermal comfort model links indoor comfort temperatures to prevailing weather outdoors, shifting them higher in warm weather and lower in cool weather. Adaptive com- fort engineering standards hold the potential to conserve energy, but for them to work effectively it is essential that building occupants are free to adapt themselves, primarily through clothing adjust- ment, to the variable indoor climatic regimes prevailing inside such buildings. This paper examines clothing behaviour and its relationship with thermal environments in 2 different indoor settings located in Sydney, Australia. The first was in a suburban shopping mall, and the second in a call- centre office. The company operating the call-centre had a strict business attire dress-code in force Mondays through Thursdays, but on Fridays employees were free to wear casual clothes. Indoor tem- peratures throughout both studies were relatively static despite significant weather and seasonal trends operating in the outdoor atmospheric environment. Clothing insulation values of garments worn inside the shopping mall showed significant day-to-day variation, with the standard deviation representing about 34% of the mean clo (1 clo = 0.155 m 2 K W −1 ) value during the study period. Typ- ical shopping mall clo values during summer were more than 0.6 clo lighter than those worn in win- ter, and a regression model of daily average clo on daily mean outdoor temperature explained 52% of the variance in clo values. Clothing insulation levels worn on 'strict business attire' days in the call- centre study were relatively static, regardless of weather or season, and they showed only a weak sta- tistical relationship with indoor temperature variations (R 2 = 20%). In contrast, the much more vari- able clo values worn by the office workers on 'casual' days, showed a significant correlation with outdoor temperatures (R 2 = 44%). Based on these relationships, an adaptive comfort model for use in hybrid ventilation buildings is proposed.

Cooperative consumers in a deregulated electricity market — dynamic consumption strategies and price coordination

As the trend in electricity markets is strongly towards deregulation, new players, new rules and new behaviors will continue to emerge. One of the new developments on the demand side is purchases made by a coalition of consumers. It seems indeed likely that in the future this will be more common, and that coalitions of consumers will emerge when they are worthwhile. The aim of this paper is to study how such an organization of consumers can be set up in a hierarchical framework. This new approach has not been described before in the deregulated electricity markets but is clearly an important research topic. We focus our interest on electric space heating, which is an energy need especially important in the Nordic countries such as Finland. We examine the consumption strategies of individual electricity buyers within a coalition. The decision problem all consumers face is to find the optimal use of their space heating system with respect to changes in electricity prices and to their tolerance to indoor temperature variation. A mathematical model for this problem is defined. Physical parameters of sample houses were gathered from an experimental field test conducted in Helsinki during the winter of 1996. The coalition buys in the market at marginal cost. However, as marginal cost pricing may not always fulfill metering and communication needs of the members of the coalition, we consider Time-Of-Use (TOU) pricing within the coalition. Different groups of consumer behavior are constructed to simulate this coalition. The optimal marginal price is used as a reference point to estimate the nearest TOU price within the coalition.

Climatic variations in comfortable temperatures: the Pakistan projects

Two thermal comfort surveys in Pakistan are described. One was longitudinal conducted in summer and winter, the other was transverse with monthly surveys over a whole year. The surveys were conducted in five cities each representing a particular climatic region. The use of building controls and clothing is analysed. There is close agreement between the findings of the two surveys despite differences in methodology. The surveys show that there is a definite relationship between indoor comfort and outdoor conditions in line with an adaptive approach to thermal comfort. The current International Standard does not accurately reflect these. Because of the large variations in indoor temperature in many Pakistani buildings, the surveys also indicate the limits of people's ability to adapt to indoor temperatures.

Analytical solution of the inverse unsteady wall heat conduction problem and experimental application

Based on the analytical solution of the unsteady heat conduction differential equation, a solution procedure is presented for the inverse unsteady wall heat conduction problem, i.e. for the calculation of the thermal properties of structural elements of existing buildings under real transient conditions, using on-site temperature measurements. Previous procedures, which were based on the finite-difference method, required a considerable number of temperature measurements in space and time within the wall. The advantage of the present analytical procedure is that it requires only two temperature measurements, apart from some information on the outdoor and indoor temperature variations. The two temperature measurements may be taken on the outdoor and indoor wall surfaces at the same time level, or on one of these surfaces at two different time levels. The proposed analytical procedure provides the values of the thermal conductivity and heat capacity of structural elements, and therefore it may be used in practice for ex post checking of the materials used by the constructor, or for load calculation when heating or cooling systems are to be installed in old buildings of unknown wall properties. Experimental examples are presented which show that the proposed analytical procedure may be applied in practice with very good accuracy.

Finite-difference prediction of transient indoor temperature and related correlation based on the building time constant

A numerical procedure for the calculation of the transient indoor temperature in buildings is developed. The procedure is based on an implicit finite-difference solution of a closed set of differential equations, which express the indoor energy balance and the transient heat conduction in all elements of the building envelope. Using the above procedure, calculations are carried out for 21 types of buildings with 18 and 10 different kinds of wall and roof constructions, respectively, i.e. the total number of building cases examined is 21 x 18 x 10 = 3780 with floor areas ranging from 30 m 2 to 3000 m 2 . It is found that buildings of different construction characteristics and sizes but with the same time constant, respond in a similar way under the same outdoor temperature variation. Based on this similarity, a correlation is developed which expresses, under periodic conditions, the indoor temperature variation in terms of the building time constant and the outdoor temperature characteristics. The correlation contains nine coefficients, the values of which are different for different ranges of the building time constant.

Pioneering new indoor temperature standards: the Pakistan project

Field surveys of thermal comfort have been conducted summer and winter in the five climatic regions of Pakistan to help the Pakistani Government to replace existing inappropriate indoor temperature standards. Results are presented which show large variations in desired indoor temperature with climate and season. The reasons for the differences are explored and an indication of the way in which responsive indoor temperature standards, which encourage the use of passive architecture and save energy in air-conditioned buildings, might be framed is presented.

Simulation of the full and part load energy consumption of HVAC system of building

A model based on dynamic heat transfers through the building envelope and between the contents inside the building is developed. This model has been incorporated into the Computer Aided Building Airconditioning Requirement and Environmental Temperature Simulation (CABARETS) program. The model takes into account the interaction between the external excitation, building envelope, contents inside the building, air handling systems and the mechanical equipment. An iterative numerical procedure has been implemented to solve the simultaneous heat transfer equations for the various components of the system. The indoor temperature and humidity variations with or without the operation of the HVAC system are established, and the energy requirements for maintaining the controlled environment are computed. The electrical power requirement for operating the HVAC mechanical equipment is estimated by the model, and the values are compared with the observed electricity consumption for the mechanical services.