Natural ventilation of buildings is the flow generated by temperature differences and by the wind. The governing feature of this flow is the exchange between an interior space and the external ambient. Although the wind may often appear to be the dominant driving mechanism, in many circumstances temperature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns within the space and on the nature of the exchange with the outside. Two forms of ventilation are discussed: mixing ventilation, in which the interior is at an approximately uniform temperature, and displacement ventilation, where there is strong internal stratification. The dynamics of these buoyancy-driven flows are considered, and the effects of wind on them are examined. The aim behind this work is to give designers rules and intuition on how air moves within a building; the research reveals a fascinating branch of fluid mechanics.

The fluid mechanics of natural ventilation

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Influences of agro-wastes on the physico-mechanical and durability properties of unfired clay blocks

Buildings, energy, and the environment are key issues facing construction around the world. The energy efficiency of buildings is a key topic when it comes to reducing the world’s energy consumption, releasing harmful gases, and global climate change, as they consume about 40% of the world’s energy supplies. Heat losses in buildings reduce the energy performance of buildings and are basically important to them. In the paper, the authors focus on the main problems related to heat losses generated by chimney systems, which are inseparable equipment of building structures, resulting in lower energy efficiency and, at the same time, technical efficiency and durability of the building partitions themselves. Authors present thermal imaging with its contribution to the detection of heat losses, thermal bridges, insulation problems, and other performance disturbances, and then verifications using appropriate simulation models. The mathematical apparatus of artificial neural networks was implemented to predict the temperature distributions on the surfaces of prefabricated chimney solutions. In Europe, we can often find a large building substance equipped with traditional chimneys, which disrupts the current trend of striving to reduce energy consumption, especially that derived from fossil fuels. Speaking of energy-efficient buildings, one should not ignore those that, without additional security and modern installations, are constantly used in a very wide range. Therefore, the article deals with an essential problem that is not perceived in design studies and during the operation period as having a basis in incorrect architectural solutions and which can be easily eliminated. It concerns the cooling of internal partitions of buildings on their last storeys, in places where chimneys are located, regardless of their function. The authors of the paper decided to take a closer look at this phenomenon, which may allow the limiting of its effects and at the same time reduce its impact on the energy performance of technologically older buildings.

The Role and Place of Traditional Chimney System Solutions in Environmental Progress and in Reducing Energy Consumption

Development of sustainable alternative materials for the construction of green buildings using agricultural residues: A review

Sawdust and coconut coir dust are agro-wastes/by-products which are suitable for use as raw materials to manufacture unfired clay blocks due to their excellent physical and mechanical properties. A limited number of studies have been conducted on the utilisation of these agro-wastes in clay block production, and they have mostly been devoted to investigating the physicomechanical properties, with less attention given to the thermal properties. Moreover, the majority of the studies have used chemical binders (cement and lime) in combination with agro-waste, thus increasing the carbon footprint and embodied energy of the samples. Furthermore, no research has been performed on the thermal performance of these agro-wastes when incorporated into clay blocks at the wall scale. Therefore, to address these limitations, the present study developed unfired clay blocks incorporating sawdust and coconut coir dust (0, 2.5, 5, and 7.5% by weight), without the use of chemical binders, and evaluated their thermal performance, both at the individual and wall scales. The experiments were divided into two phases. In the first phase, individual sample blocks was tested for basic thermal properties. Based on the results of the first phase, small walls with dimensions of 310 mm × 215 mm × 100 mm were built in the second phase, using the best performing mixture from each waste type, and these were assessed for thermal performance using an adapted hot box method. The thermal performance of the walls was evaluated by measuring the heat transfer rate from hot to cold environments and comparing the results to the reference wall. The results showed that thermal conductivity decreased from 0.36 W/mK for the reference sample, to 0.19 W/mK for the 7.5% coconut coir dust sample, and 0.21 W/mK for the 7.5% sawdust sample, indicating an improvement in thermal insulation. Furthermore, the coconut coir dust and sawdust sample walls showed a thermal resistance improvement of around 48% and 35%, respectively, over the reference sample wall. Consequently, the findings of this study will provide additional essential information that will help in assessing the prospective applications of sawdust and coconut coir dust as the insulating material for manufacturing unfired clay blocks.

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Thermophysical Properties of Sawdust and Coconut Coir Dust Incorporated Unfired Clay Blocks

This paper evaluates, via a laboratory assessment, the physical properties (BS EN 323:1993, BS EN 324) and mechanical performance (BS EN 310:1993) of hybrid particleboards using agricultural wastes, namely coconut fibre and sawdust. The process begins with the preparation of the materials where they are sieved and retained with the 5-mm sieve and then oven-dried. The hybrid particleboard mixed with the addition of resin (urea formaldehyde) was sprayed and hot pressed. The hot press temperature was set at 180 °C, with the resin content of 8 wt.% and the design density of 650 kg/m3 used in producing the particleboard. The percentage/ratio of the composition of sawdust (SD) to coconut fibre (CF) varied ranging from 100SD:0CF to 70SD:30CF, 50SD:50CF, 30SD:70CF, and 0SD:100CF. Meanwhile, as for the thickness of the boards, it was categorised into three groups which are 16 mm, 20 mm, and 32 mm. The particleboards were conditioned to the room temperature for seven days before being tested for physical properties and mechanical performances. The results show that the most optimum composition of sawdust to coconut fibre is 0% sawdust to 100% coconut fibre (0SD:100CF) and the optimum thickness is 20 mm, where its density is 761.99 kg/m3, swelling thickness is 11.98%, and water absorption at 37.64%. With the modulus of elasticity of 1510 N/mm2, the modulus of rupture of 17.8 N/mm2, and the internal bonding of 1.08 N/mm2, they satisfied the universal standard of Particleboard Type P3 of BS EN 312:2010.

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Coconut Fibre and Sawdust as Green Building Materials: A Laboratory Assessment on Physical and Mechanical Properties of Particleboards

The provision requirement of 10% openings of the total floor area stated in the Uniform Building By-Law 1984 Malaysia is essential for natural lighting and ventilation purposes. However, focusing on natural ventilation, the effectiveness of thermal performance in landed residential buildings has never been empirically measured and proven, as most of the research emphasized simulation modeling lacking sufficient empirical validation. Therefore, this paper drawing on field measurement investigates natural ventilation performance in terraced housing with an air-well system. The key concern as to what extent the current air-well system serving as a ventilator is effective to provide better thermal performance is to be addressed. By adopting an existing single-story air-welled terrace house, indoor environmental conditions and thermal performance were monitored and measured using HOBO U12 air temperature and humidity, the HOBO U12 anemometer, and the Delta Ohm HD32.3 Wet Bulb Globe Temperature meter for a six-month duration. The results show that the air temperature of the air well ranged from 27.48 °C to 30.92 °C, with a mean relative humidity of 72.67% to 79.25%. The mean air temperature for a test room (single-sided ventilation room) ranged from 28.04 °C to 30.92 °C, with a relative humidity of 70.16% to 76.00%. These empirical findings are of importance, offering novel policy insights and suggestions. Since the minimum provision of 10% openings has been revealed to be less effective to provide desirable thermal performance and comfort, mandatory compliance with and the necessity of the bylaw requirement should be revisited.

https://www.mdpi.com/2071-1050/13/1/201/pdf

Thermal Performance of Single-Story Air-Welled Terraced House in Malaysia: A Field Measurement Approach

Energy consumption has shown that residential building is among the main contributors of energy demand. Besides, the harsh climatic conditions have causes substantial amount of energy which contributes indirectly towards the impact on carbon emission to the nations. Hence, this research utilised the potential agricultural wastes materials that is potential for insulate the thermal building performance. The outer and inner surface temperature has been measured on selected seven (7) type of wastes material from agricultural and processing sector every 30 minutes from 0900hr to 1800hr for a day in order to determine the decrement factors (DF), average daily time-lag for heat transfer as one of the thermal insulation properties. Results on the time-lag for all selected potential waste materials as thermal insulation whereas sugarcane bagasse is the lowest 107.5 minutes, followed by both coffee grounds and coconut husk with 130 minutes and wood wool with 132.5 minutes. Meanwhile, empty fruit bunch, coconut fibre and pineapple leave with time-lag of 140 minutes, 142.5 minutes and 145 minutes respectively are the highest time-lag occurred. Generally, the lowest Tis is the better the thermal performance therefore, coconut fibre with smaller DF, larger LT but slightly higher Tis than EFB (32°C) which is 32.2 °C might be the suitable material use as thermal insulation.

Dg Normaswanna Tawasil

Papers

Coconut Fibre and Sawdust as Green Building Materials: A Laboratory Assessment on Physical and Mechanical Properties of Particleboards

Thermal Performance of Single-Story Air-Welled Terraced House in Malaysia: A Field Measurement Approach

Time-lag Analysis of Potential Waste Materials as Thermal Insulation in Tropical Climate: A Preliminary Investigation

Effects of Hot-Press Temperature and Mix Proportions on Mechanical Behaviours of Hybrid Coconut Fibre Particleboard