Unconditioned Buildings Research Articles

Assessment of frost damage risk in a historic masonry wall due to climate change

Abstract. Historic masonry buildings are an integral part of human cultural heritage, and they need to be preserved for future generations. Brick is susceptible to frost damage which is common in regions with cold and humid climates. The frost damage on the masonry walls is accumulated over the years becoming more and more critical for the integrity of the historic buildings and it is also affected by climate change (CC). In the current research, the focus was placed on a coastal region in southern Norway with a significant number of historic masonry buildings. The frost damage risk of the masonry walls was assessed by using data from a climate reanalysis for the present conditions and from a climate model under past, present, and future conditions. Two climate-based (CB) indices accounting for the air temperature and one material response-based (MRB) index considering the temperature and moisture content inside a simulated masonry wall were used for the frost damage risk assessment. The inputs for the MRB index were calculated by heat, air, and moisture (HAM) transfer simulations. Within the HAM simulations, the indoor climate was in one case representative of an unconditioned building with air leakages and many openings, while in the second case it was representative of a small, conditioned room. The overall impact of CC was a decrease in the frost damage risk of the masonry walls. However, an increased frost damage risk was observed from the present to the future conditions according to the MRB index for the walls of small, conditioned rooms with higher driving rain load and lower solar radiation gains. The (i) number of freeze-thaw events, (ii) periods during which freeze-thaw events occur, and (iii) CC-related trends varied based on the considered index with the most explicit risk assessment being the MRB one. Moreover, the freeze-thaw events experienced by the masonry walls of unconditioned, leaky buildings were 20 times more than the ones for the small, conditioned rooms. Significant differences were observed between the results from the climate model and the climate reanalysis which were mainly linked to the underestimation of the air temperature and the overestimation of the precipitation by the climate model. The outputs of the MRB index were translated into certain damage categories while suggestions on improving the limitations of the current research were made.

On the thermal performance of naturally ventilated room with straw insulation retrofitted envelope for different climatic zones of India

The heat insulating potential of straw, an agricultural residue, used as part of the envelope of unconditioned buildings is the focus of the current work. Using a CFD software with experimentally validated boundary conditions, transient thermal analysis is performed on a 3-D model room of dimensions 3 m × 3 m × 2.5 m with vents and heat source representing a naturally ventilated indoor space. The thermal performances of a reference uninsulated concrete envelope and a straw insulation-based envelope are compared in terms of quantitative parameters such as indoor air temperature, decrement factor, and time lag as well as a qualitative discussion on the need for occupant adaptation, namely closing or opening of inlet vent and requirement of additional heating. The assessment and subsequent recommendation of straw insulation utilization is done for representative summer and winter days of the five different climatic zones of India. A maximum reduction of up to 3.5 °C in the peak indoor air temperature is achievable with inlet temporarily closed when straw insulation is included in the envelope in summer conditions. In winter conditions of cold climatic zone, with inlet always closed, use of straw insulation leads to the lessening of additional active heat source requirement by as much as 600 W for the considered model room. Further, the effects of increased straw insulation thickness, removal of heat source, varying inlet air velocity, and changing the position of the straw insulation to the outside are also analyzed for the extreme warm and cold conditions.

The dual influence of the envelope on the thermal performance of conditioned and unconditioned buildings

Cities are progressively widening, incorporating rural and industrial zones and, at the same time, largest cities often need conversion of entire neighbourhoods. The transformation of large areas, through the introduction of energy-efficient buildings, quickly provides economic and social benefits. The current technologies for building energy-saving offer wide technical solutions range mainly developed for residential buildings. Nevertheless, the current literature lacks enough studies on envelope effectiveness in non-residential sectors, where indoor conditions are considerably different from residential.In this context, the paper aims at assessing the influence of five architectural characteristics on the thermal performances in a case study food-processing building. 576 building configurations are analyzed for six different intended use (0–24 °C) in conditioned and unconditioned scenarios. The performances of the different building configurations are expressed in terms of energy need (conditioned scenario) and thermal discomfort (unconditioned scenario). Results reveal that building thermal performance is connected to temperature ranges and the same building envelope characteristic can show positive or negative contribution according to the simulated scenario. Finally, for both scenarios, the most influential architectural characteristics have been identified and evaluated. Moreover, the paper proposes a methodology for building energy assessment for the transformation of existent industrial food-processing buildings in urban and suburban areas.

Experimental and numerical assessment of using coconut oil as a phase‐change material for unconditioned buildings

The efficacy of integrating organic coconut oil (co-oil) phase-change material (PCM) into an unconditioned building with a lightweight envelope is explored experimentally and numerically for heat gain reduction. In what we think is the first test of its kind for co-oil PCM, twin side-by-side single-room buildings (with and without PCM) are constructed and studied experimentally under ambient weather conditions. The effects of the co-oil on the thermal performance of the buildings are investigated with respect to the window orientation (east, west, north and south). Furthermore, numerical simulation of the buildings is carried out to evaluate the contribution of the co-oil to their thermal performance and to determine the effect of the co-oil layer thickness on the heat storage capacity. Moreover, by employing a simplified heat transfer analysis, an approximate relation for the optimal thickness of co-oil PCM layer is developed. Experimental and numerical results show that co-oil PCM can be a promising solution to improve the indoor thermal environment. It is found that with a south-facing window equipped with co-oil PCM, the indoor temperature is lowered by 23.8% compared to the case without PCM, when an optimal PCM layer of ~4 cm in thickness is embedded in the wall.

Energy Efficient Retrofit Model for Unconditioned Buildings Set in the Composite Climatic Region of India

The potential of energy efficient retrofitting of existing unconditioned buildings to save associated building energy consumption makes it an area of great interest. A questionnaire survey conducted amongst the architecture and civil stream students of Indian institute of Technology (IIT) Roorkee, based upon the questions related to high performance buildings parameters revealed that, energy efficiency is one of the areas which needs greatest attention. The outcome of this survey strengthens the need of such research. Therefore, this research intends to convert an existing unconditioned building to an energy efficient building. For doing so, energy savings opportunities in existing unconditioned buildings are identified and devised into a four – fold energy efficient retrofit model. This paper, evaluates the significance of the proposed four- fold energy efficient model using case studies and energy simulation modeling as a tool.

Performance Evaluation of a Guarded Hot Box Test Facility Using Fuzzy Logic Controller for Different Building Material Samples

Abstract In an air-conditioned building located at any climatic region, the energy usage could be conserved by means of reducing the heating or cooling load on the Heating, Ventilation and Air Conditioning (HVAC) system depending upon outdoor climatic conditions. In case of unconditioned building, the temperature variation inside it over a specified time depending upon the outdoor climatic conditions helps one to estimate the duration of uncomfortable periods. By controlling heat gain or loss through building components like walls, roofs, window glazing etc. the overall energy used in both types of buildings could be minimised and for doing so, thermal performance of any building material should be evaluated. The overall heat transfer coefficient, which is measured using the Guarded Hot Box Test Facility, is one of the key measures of evaluating the energy performance of any building material. The lesser this value, the less energy is required to maintain comfortable conditions inside the building. In this paper, the performance evaluation of a fuzzy logic based temperature control strategy in a Guarded Hot Box Test Facility using three types of building materials - a single glazing, a double glazing and a plank of Extruded Polystyrene (XPS) as test specimens has been done and compared.

Retrofit interventions in non-conditioned rooms: calibration of an assessment method on a farm winery

In the Mediterranean area, most wine farms make use of unconditioned above-ground buildings for wine conservation and ageing. Those buildings are usually constructed without a specific temperature control design, therefore indoor temperature distributions and trends can be suboptimal for wine storage. At the same time, various elements (commonly available in farms such as straw bales and climbing plants) could be used to create cheap constructive solutions capable of improving building's thermal behaviour. This study aims to test the effectiveness of different retrofit interventions for thermal behaviour improvement in unconditioned above-ground farm buildings, referring to wine-ageing requirements. The alternative design solutions are evaluated through energy simulations, calibrated and validated on an Italian case study. The results show the importance of roof insulation, and the improved performance of the combination of more retrofit strategies. The proposed approach can be extended to other passive strategies and proves useful to provide information to optimize, or even avoid, conditioning systems.

Development for cool roof calculator for India

In tropical countries such as India, increasing the roof albedo helps to reduce the heat ingress through the roof. This further reduces air-conditioning energy consumption in conditioned buildings and increases comfort in unconditioned buildings. In order to help users determine the benefits of high albedo roofs under varying conditions, a simple calculator has been developed. Parameters such as location, building type, roof area, and surface properties of the roof are taken as inputs. Annual EnergyPlus simulations are performed for the given parameters and the results are displayed in both graphical and tabular formats. It also calculates the simple payback by comparing a given base case roof albedo with the proposed roof albedo. The calculator can perform comfort simulations for unconditioned buildings and simulates measures including a radiant barrier system and under deck roof insulation. The calculator also runs a parametric simulation between insulation thickness and roof albedo to find an optimum roof insulation thickness based on incremental internal rate of return. This paper presents the features of the cool roof calculator and the type of analysis that can be performed using the cached results.

Energy-efficient retrofit of an unconditioned institute building

The purpose of this study is to demonstrate the energy-efficient retrofitting of an existing unconditioned academic department building in the campus of the Indian Institute of Technology, Roorkee, India. It is achieved with the use of energy simulation modelling to examine the energy-saving benefits of power-consuming equipments, power generation through renewable sources improving thermal comfort through Energy Conservation and Building Code India's compliance and motivating the buildings’ occupants for energy-responsive behaviours. These strategies, when applied together, lead to an overall reduction of 40.4% in the total energy consumption. It was observed that the energy units saved for an unconditioned building are significantly lower than that of a conditioned building, but the percentage changes are comparable for both the types. The heat gain results from simulation software also show that in such buildings external windows account for most of the heat gain within the building, whereas uninsulated walls result in heat loss throughout the year. Changes in the operative temperature of the order of 0.5–4.0°C are observed by proposing a green roof, false ceiling, wall insulation and high performance glass. If the same retrofits are applied to all other academic buildings, huge energy savings and cost benefits can be obtained.

Global cooling updates: Reflective roofs and pavements

With increasing the solar reflectance of urban surfaces, the outflow of short-wave solar radiation increases, less solar heat energy is absorbed leading to lower surface temperatures and reduced outflow of thermal radiation into the atmosphere. This process of “negative radiative forcing” effectively counters global warming. Cool roofs also reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win–win–win activity that can be undertaken immediately, outside of international negotiations to cap CO2 emissions. We review the status of cool roof and cool pavements technologies, policies, and programs in the U.S., Europe, and Asia. We propose an international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions.

Effects of soiling and cleaning on the reflectance and solar heat gain of a light-colored roofing membrane

A roof with high solar reflectance and high thermal emittance (e.g., a white roof) stays cool in the sun, reducing cooling power demand in a conditioned building and increasing summertime comfort in an unconditioned building. The high initial solar reflectance of a white membrane roof (circa 0.8) can be lowered by deposition of soot, dust, and/or biomass (e.g., fungi or algae) to about 0.6; degraded solar reflectances range from 0.3 to 0.8, depending on exposure. We investigate the effects of soiling and cleaning on the solar spectral reflectances and solar absorptances of 15 initially white or light-gray polyvinyl chloride membrane samples taken from roofs across the United States. Black carbon and organic carbon were the two identifiable strongly absorbing contaminants on the membranes. Wiping was effective at removing black carbon, and less so at removing organic carbon. Rinsing and/or washing removed nearly all of the remaining soil layer, with the exception of (a) thin layers of organic carbon and (b) isolated dark spots of biomass. Bleach was required to clear these last two features. At the most soiled location on each membrane, the ratio of solar reflectance to unsoiled solar reflectance (a measure of cleanliness) ranged from 0.41 to 0.89 for the soiled samples; 0.53 to 0.95 for the wiped samples; 0.74 to 0.98 for the rinsed samples; 0.79 to 1.00 for the washed samples; and 0.94 to 1.02 for the bleached samples. However, the influences of membrane soiling and cleaning on roof heat gain are better gauged by fractional variations in solar absorptance. Solar absorptance ratios (indicating solar heat gain relative to that of an unsoiled membrane) ranged from 1.4 to 3.5 for the soiled samples; 1.1 to 3.1 for the wiped samples; 1.0 to 2.0 for the rinsed samples; 1.0 to 1.9 for the washed samples; and 0.9 to 1.3 for the bleached samples.

Thermal and Airflow Modelling of Mediterranean Buildings: Application to Thermal Comfort in Summer

The assessment of building thermal comfort quality in the Mediterranean context necessitates an accurate knowledge of air temperature and velocity fields inside the space. Also, these thermal and airflow aspects must be considered in combination because of their very strong interdependence. In this particular context, a three-dimensional calculation model of coupled heat transfer and airflow calculation has been developed, which enables the evaluation of temperature field and airflow pattern inside unconditioned buildings under transient conditions, taking into account external conditions. This approach is based on a temperature and pressure driven zonal airflow model, coupled with a thermal model founded on the coupling of reduced-order state models. By combining this with a thermal comfort model it is possible to evaluate the thermal quality of buildings by the prediction of a comfort vote. This paper presents an application of the coupled simulation tool dealing with the influence of a night natural cross-ventilation strategy upon the summer thermal comfort of a Tunisian building.

ZAER: A Zonal Model for Heat Transfer and Air Flow in Unconditioned Buildings. - An Experimental Validation

This paper presents a three-dimensional zonal model, ZAER, for heat transfer and air flow calculations. It is based on an intermediate approach between single-air-node and CFD models. The indoor air volume is divided into macroscopic homogeneous zones. Heat and mass balance equations are written for each zone, while the mass flow rates across the interfaces are calculated by power pressure laws. The simulation tool ZAER allows the determination of temperature fields and air flow distributions inside unconditioned buildings, taking into account external boundary conditions. We also present an experimental validation of the model by comparing its predictions with experimental data obtained from measurements on the experimental cell Minibat (CETHIL, INSA Lyon Laboratory), for different configurations. The results obtained are in good agreement with experimental data, and suggest that the ZAER model is an appropriate tool to assess satisfactorily temperature heterogeneity and air movement within a room.

Comfort, climate analysis and building design guidelines

The paper discusses issues of thermal comfort standards, including the ASHRAE comfort zone, techniques of graphical climate data analysis, as well as the uses of building bioclimatic charts in the formulation of building design guidelines, especially for hot climates. The problematics of applying the Olgyay bioclimatic charts and the ASHRAE comfort standards for unconditioned buildings, especially in developing hot countries, are discussed. Revised building bioclimatic charts are described for the first time in this paper. The boundaries of applicability of various building design strategies and passive cooling systems in different climates are discussed. These strategies are based on the expected indoor temperatures achievable with the different strategies and include daytime ‘comfort” ventilation, the utilization of the structural mass for thermal storage in conjunction with nocturnal ventilation, and direct and indirect evaporative cooling.

Work-related illness in offices: A proposed model of the ‘sick building syndrome’

Abstract A nationwide survey of 4 373 office workers at 47 office sites was conducted to assess the prevalence of the sick building syndrome and to investigate associated factors. The office buildings sampled included those ventilated by either natural, mechanical, or forced air, or by air conditioning or some form of comfort cooling, including fan-coil, induction, and constant or variable air volume systems. Results showed a higher prevalence of reports of work-related symptoms of dry eyes, dry throut, stuffy/congested nose, itchy/watery eyes, runny nose, lethargy/tiredness, and headache in air conditioned buildings than in unconditioned buildings. Symptom prevalence was higher in buildings ventilated with water-based cooling systems, e.g., fan-coil or induction systems, than in buildings with all-air systems. A significant relationship was found between the type of humidification used in air-conditioned buildings (none, evaporative/spray, or steam) and the prevalence of itchy eyes, stuffy nose, lethargy, breathing difficulty, and chest tightness. Results also suggest that the “sick building syndrome” is associated with a variety of individual characteristics (sex, age), occupational factors (job type, length of video display unit use, occupancy duration in building, job stress), architectural features (type of office, type of building ventilation system), and psychological processes (perceived environmental control, perceived ambient conditions, perceived environmental satisfaction). A path analytic model is presented that suggests that psychological processes mediate the association between individual, occupational, and environmental characteristics and reports of the “sick building syndrome”.

Work-related illness in offices: A proposed model of the “sick building syndrome”

A nationwide survey of 4 373 office workers at 47 office sites was conducted to assess the prevalence of the sick building syndrome and to investigate associated factors. The office buildings sampled included those ventilated by either natural, mechanical, or forced air, or by air conditioning or some form of comfort cooling, including fan-coil, induction, and constant or variable air volume systems. Results showed a higher prevalence of reports of work-related symptoms of dry eyes, dry throut, stuffy/congested nose, itchy/watery eyes, runny nose, lethargy/tiredness, and headache in air conditioned buildings than in unconditioned buildings. Symptom prevalence was higher in buildings ventilated with water-based cooling systems, e.g., fan-coil or induction systems, than in buildings with all-air systems. A significant relationship was found between the type of humidification used in air-conditioned buildings (none, evaporative/spray, or steam) and the prevalence of itchy eyes, stuffy nose, lethargy, breathing difficulty, and chest tightness. Results also suggest that the “sick building syndrome” is associated with a variety of individual characteristics (sex, age), occupational factors (job type, length of video display unit use, occupancy duration in building, job stress), architectural features (type of office, type of building ventilation system), and psychological processes (perceived environmental control, perceived ambient conditions, perceived environmental satisfaction). A path analytic model is presented that suggests that psychological processes mediate the association between individual, occupational, and environmental characteristics and reports of the “sick building syndrome”.

Thermal performance and energy requirements of buildings

The need for simple yet accurate techniques for assessing the thermal performances of buildings is discussed, particularly in relation to residential buildings in Australia. A method is presented for calculating heating or cooling load requirements in terms of indoor temperatures in totally unconditioned (i.e. free-running) buildings. The method accounts for thermal capacitance in the building fabric and intermittent heating or cooling. It can also allow for climatic variability from day to day. The method is a generalization of the variable base degree-day technique which has recently achieved prominence in the United States of America.

Thermal modeling of integrated roof air heater for passive solar space heating of a non-air-conditioned building

This communication presents the periodic heat transfer analysis for solar space heating of an unconditioned building with an integrated roof air heater. The system consists of an air duct within the roof such that the air is continuously or intermittently forced to circulate the cooler room air through the inlet of the air duct. Time dependence of the air flow is represented by a step function of time for daily operation and, hence, has been expressed as a Fourier series in time. The analysis takes into account air ventilation, ground heat conduction and furnishings. The effects of depth of the air duct from the outer surface of the roof and the magnitude and duration of air flow rate on indoor air temperature have been studied for a typical cold winter day in Delhi. It is seen that a time dependent air flow through the duct is desirable from the point of view of increasing the indoor air temperature in the case of a bare roof. However, in the case of a blackened and glazed roof, continuous air flow is needed for increasing the room air temperature. The results are desirable from the point of view of efficient space heating of solar passive buildings.

Room response according to CIBS Guide procedures

This paper starts by amplifying the discussion of the procedures for determining the steady-cyclic thermal response of rooms presented in Section A5 of the CIBS Guide 1979. Section A5 presents the basic considerations underlying this approach to the problem but their implications are worked out only for a few specific applications. It lacks a method for determining heating plant requirements net of gains and ventilation is assumed constant except for the case of unconditioned buildings. In addition some formulae presented are justified only by cross-reference to earlier published analyses based on rather different assumptions. The second part of this paper takes the basic discussion of Section A5 as a starting point and develops a general algorithm for determining the room response for an arbitrary type of heating or cooling system (radiation, convection), arbitrary gains and arbitrary variations of ventilation rate. This can provide the basis for a general-purpose computer program implementing the Section A5 model or for deriving formulae appropriate to specific applications. The final section presents such formulae for intermittent heating requirements net of gains, including consideration of excess gain conditions. Variable ventilation is allowed for on the basis of constant ‘day’ and ‘night’ rates coinciding with the heating cycle. Substantiation of the Section A5 formula for intermittent operation of cooling plant and a more manageable version of its formula for summertime temperatures are also provided.

The functional aspects of building design in warm climates with particular reference to thermal and ventilation considerations

The functional design of buildings is discussed with particular reference to thermal and ventilation considerations. Brief reference is made to indoor environmental conditions in both conditioned and unconditioned buildings. The lack of useful information with respect to the effects of directional radiation in warm climates is emphasized. A method is outlined for a more rational assessment of outdoor meteorological conditions in terms of the probability of joint occurrence of various combinations of meteorological elements. The influence of structural design on the thermal performance of buildings is discussed in terms of the diurnal variation of outdoor air temperature and solar radiation fluxes. The need of ceiling insulation is specifically stressed.