Exterior Surfaces Of Buildings Research Articles

Ethereal material: colour and material surface

This article examines the role of colour as an integral consideration of material selection. It suggests that an understanding of colour, and its potential to alter the general perception of form, space and surface, is as essential as any other material property. Recent developments have led to a period of growth in the use of colour in architectural design, for example through highly pigmented ceramic tiles, back-painted glass facades and pigmented concrete. These offer permanent and durable surfaces. The potential of colour to alter the perception of space and form brings with it a certain anxiety in its use, particularly when embedded on the exterior surfaces of buildings. Yet decisions on colour are often arbitrary and left until late in the design process. The article will consider colour and material surface, colour as conceptual material, the elusive properties of colour, which are entirely contingent on light conditions and context, and colour specification in the design process.

Analysis and Design of Diagrid Structural System for High Rise Steel Buildings

Advances in construction technology, materials, structural systems and analytical methods for analysis and design facilitated the growth of high rise buildings. Structural design of high rise buildings is governed by lateral loads due to wind or earthquake. Lateral load resistance of structure is provided by interior structural system or exterior structural system. Usually shear wall core, braced frame and their combination with frames are interior system, where lateral load is resisted by centrally located elements. While framed tube, braced tube structural system resist lateral loads by elements provided on periphery of structure. It is very important that the selected structural system is such that the structural elements are utilized effectively while satisfying design requirements. Recently diagrid structural system is adopted in tall buildings due to its structural efficiency and flexibility in architectural planning. Compared to closely spaced vertical columns in framed tube, diagrid structure consists of inclined columns on the exterior surface of building. Due to inclined columns lateral loads are resisted by axial action of the diagonal compared to bending of vertical columns in framed tube structure. Diagrid structures generally do not require core because lateral shear can be carried by the diagonals on the periphery of building. Analysis and design of 36 storey diagrid steel building is presented. A regular floor plan of 36 m × 36 m size is considered. ETABS software is used for modeling and analysis of structural members. All structural members are designed as per IS 800:2007 considering all load combinations. Dynamic along wind and across wind are considered for analysis and design of the structure. Load distribution in diagrid system is also studied for 36 storey building. Similarly, analysis and design of 50, 60, 70 and 80 storey diagrid structures is carried out. Comparison of analysis results in terms of time period, top storey displacement and inter-storey drift is presented in this paper.

A comparison of Mediterranean Gecko (Hemidactylus turcicus) populations in two temperate zone urban habitats

Urban ecosystems represent unique habitats that might be more or less suitable than natural systems for many species. The Mediterranean Gecko, Hemidactylus turcicus is a synanthropic species that has successfully colonized many urban and suburban areas outside its natural range. In the United States, H. turcicus has been found predominantly in southern states on exterior surfaces of buildings. We compared population density, demographics, and extent of dispersal of populations of H. turcicus at two anthropogenic sites in a temperate region of the United States. The University of Central Oklahoma (UCO) had higher building density and greater cover by anthropogenic surfaces and the Oklahoma City Zoo (ZOO) had lower building density and greater cover by vegetation. Mark and recapture sampling was conducted at UCO from 2006 to 2007 and during 2008 at ZOO. The sizes of the populations at the two sites were estimated using the Schnabel method and population densities were calculated using those estimates. Age class of captured animals, sex of adults, and gravid status of adult females were determined at both sites. We assumed that greater exterior wall surface area of individual buildings at UCO and greater land cover by anthropogenic surfaces might 1) reduce population density and 2) facilitate dispersal there relative to the ZOO. Population sizes and density in animals per ha of land and building cover and demographics were similar at the two sites. Population density per ha of building exterior wall area was higher at ZOO than at UCO. The higher density of animals on buildings, lower proportion of subadults in the population and lower maximum dispersal distance at ZOO suggest that successful diffusion dispersal might be limited at that site relative to UCO.

An adaptive temperature wall function for mixed convective flows at exterior surfaces of buildings in street canyons

For computational fluid dynamics (CFD) simulations of large urban areas the air flow near surfaces is normally modelled using Wall Functions (WFs). This study aims at improving the accuracy of WFs, in terms of heat transfer predictions. Turbulent boundary layers at heated building surfaces in a street canyon were analysed with low-Reynolds number modelling (LRNM). Buoyancy was accounted for, due to its importance in street canyons e.g. by solar radiation. Two extreme types of normalized temperature profiles could be identified in the thermal boundary layer dependent on the Richardson (Ri) number. One extreme at low Ri number could be attributed to forced convective flow, which is adequately described by existing standard wall functions (SWFs), and the second extreme at Ri>1 to mixed convective flows, where WFs adapted for non-equilibrium flows (NEWFs) are appropriate. Based on these two extremes, an adaptive temperature wall function (AWF) was derived that varies between the two existing WFs dependent on the local Ri. This AWF can account for the co-occurrence of forced and mixed convective flow regimes at a single surface. CFD simulations of street canyon configurations with SWF showed errors in the wall heat fluxes up to 60%, compared to the LRNM results, and up to 30% for NEWFs. With the proposed AWF, these errors were reduced to less than 10% for the majority of the cases studied over the whole range of Ri numbers. We conclude that the proposed AWF allows for more accurate convective heat transfer analysis in urban CFD studies.

Simple Correction Methods of Infrared Thermography for Building Exterior Surfaces

There is a need to improve the accuracy of infrared thermography for measuring the temperature distribution of building exterior surfaces. Thermography is useful for building ventilation and thermal analysis, as well as understanding city ventilation and the urban heat island phenomenon. The key in correcting infrared images is to quantify accurately the reflected infrared contribution of surrounding surfaces as well as that of the atmosphere. Two new methods are proposed here for correcting measured temperature distribution of building exterior surfaces by infrared thermography. The first is a simplified version of the aluminium mirror method first developed by Datcu et al (2005). The second is a temperature-based method using the measured surface temperatures at one or more points on the same surface. We present two series of specially designed experiments to evaluate the two proposed methods and two other commonly used/default methods. The temperature-based method can be used effectively to correct the infrared thermography results for measured surfaces with both specular and diffuse reflection, while the aluminium mirror method can only be used for surfaces with diffuse reflection. A good agreement was observed between the corrected infrared thermography results using the temperature-based method and thermocouple measurements with a mean error ranging between 0.07–0.36oC for concrete surfaces, 0.05–0.11oC for glazing surfaces and 0.17–0.41oC for tile surfaces. The centre location of the target surface can be used as an ideal sampling point for correcting the entire measured surface. The proposed new methods were further verified on a real building external surface. The method is also applicable to measurement of indoor surfaces.

Solar radiation calculation methodology for building exterior surfaces

The present article shows a new methodology of calculation of the direct, diffuse and reflected incident solar radiation, in all type of surfaces, either in open urban environments or inside buildings. This methodology is applicable in problems related to solar access (space heating in buildings, shadowing of open spaces), solar gains (space cooling in buildings), and daylighting. Solar radiation is the most important contribution to the surface and volumetric energy balance during the daytime. Particularly, solar radiation is the main contributor to heat gains in buildings, especially in residential buildings, where internal gains are very low. Utilization of daylight in buildings may result in significant savings in electricity consumption for lighting while creating a higher quality indoor environment. Additional energy savings may also be realized during cooling season, when reduction of internal heat gains due to electric lighting results in a corresponding reduction of cooling energy consumption. The analysis of the existing calculation methods and proposed in the scientific bibliography for the calculation of the solar radiation in problems of solar access in winter, solar gains in summer, and daylighting, takes us to the necessity of outlining a new and complete methodology. This new methodology is applicable to all these problems with a great accuracy and calculation speed.

THE ANALYSIS OF SPEED AND PRESSURE OF WIND IN RAINY WEATHER/VĖJO SLĖGIO IR JO GREIČIO KITIMO LYJANT ANALIZĖ

It is not enough to investigate only the effect of wind on buildings, because deterioration of exterior surfaces of buildings is caused by wind and moisture together. A considerable part of rain gets into the exterior surface of enclosure, penetrates deep down and destroys the material of surface layer. The rain passes through enclosure construction and its surface layer due to wind pressure, through joints of the elements and cracks caused by improper transportation as well as by an inaccurate assembling. At present, new multilayer constructional elements are used for building envelope having numerous assembling seams, therefore, the combined influence of rain and wind becomes rather dangerous. It was established that the wind velocity during the rain is one of the main reasons predetermining moisture penetration into protective-decorative walls made of sand-lime brick with split surface, on concrete-lime mortar, according to the analysis of combined influence of the climate by research data [4]. The total effect of rain and wind on the humidity condition of exterior layers is described. Distribution of real wind velocity was estimated according to the data of the last 10 years. It was found that in Kaunas the average wind velocity increases from 3,4 m/s when the rain is absent up to 4,3 m/s and in Vilnius—the average wind velocity increases from 2,9 m/s when the rain is absent up to 3,7 m/s with an increase of approximately 26%, while in Klaipeda the average wind velocity increases from 3,6 m/s when the rain is absent up to 5,1 m/s with an increase of approximately 42%. On the base of the investigations carried out the suggestion is proposed to use the maximum and mean wind velocity values at the rain for estimating the effect of wind to the moisture behaviour in building elements.

THE ANALYSIS OF SPEED AND PRESSURE OF WIND IN RAINY WEATHER

Summary It is not enough to investigate only the effect of wind on buildings, because deterioration of exterior surfaces of buildings is caused by wind and moisture together. A considerable part of rain gets into the exterior surface of enclosure, penetrates deep down and destroys the material of surface layer. The rain passes through enclosure construction and its surface layer due to wind pressure, through joints of the elements and cracks caused by improper transportation as well as by an inaccurate assembling. At present, new multilayer constructional elements are used for building envelope having numerous assembling seams, therefore, the combined influence of rain and wind becomes rather dangerous. It was established that the wind velocity during the rain is one of the main reasons predetermining moisture penetration into protective-decorative walls made of sand-lime brick with split surface, on concrete-lime mortar, according to the analysis of combined influence of the climate by research data [4]....

Analysis of the sensible heat flux from the exterior surface of buildings using time sequential thermography

In this study, the distribution of surface temperature on the surface of two buildings having different characteristics was measured using a thermal infrared camera. Measurements were made in the summer, the period in Japan during which heat flux from buildings is of major interest, and again in the winter for comparison purposes. The heat characteristics of each building were obtained throughout the day by time-sequential thermography (TST), and the surface temperature of each physical element was classified according to temperature, shape, material and position. When the temperature of a surface could not be determined by an infrared camera mounted on the top of a building or a pole, temperature measurements were made using a hand-held IR camera. In addition, the sensible heat flux from each surface was calculated using TST and the surface area of each element as calculated from blueprints of the buildings.

Building energy efficiency and fire safety aspects of reflective coatings

Radiant energy exchange between the exterior surfaces of buildings and the environment has a significant impact on both the energy requirements for cooling and heating, and on fire safety. These issues of energy efficiency and fire safety are usually examined separately, but in this paper the interaction between these issues is discussed, with emphasis on reflective coatings. The important spectral ranges for radiant control are, in micrometers (μm), 0.3–2.5 (sunlight), 4–40 (300 K environmental thermal radiation) and 1–10 (fire). Benefits can be obtained from the development of improved coatings which reflect adverse energy flows and absorb (and emit) favorable energy flows. As a specific important example, white coatings with high solar reflectivity and high IR emissivity can significantly reduce energy use for cooling. Another benefit of high IR reflectivity in the 1–10 μm wavelength range is enhanced fire safety due to the reflection of IR radiation emitted by fire. Due to overlap of the fire spectrum with both the solar and 300 K thermal spectra, fire retardant coatings can either enhance or impair energy performance. From a research and development point of view there is considerable synergism between coatings for improved energy efficiency and fire safety. Technology developed for improved energy efficiency can be adapted (transferred) to coatings for reflecting fire radiation, and vice versa.