Preventing overheating in offices through thermal inertial properties of compressed earth bricks: A study on a real scale prototype

Arianna Brambilla, Thomas Bernard Paul Jusselme
Elsevier, 2017
Article

Résumé

Buildings are increasingly required to be efficient not just in their operation, but from construction to demolition. Thus, interest in natural construction materials with low embodied environmental impacts has increased, (re)inventing materials and components from vernacular architecture. Compressed Earth Bricks (CEBs) are an example of this kind of component. They are flexible in a wide range of applications and their natural features favour their usage as thermally massive elements to increase a building’s thermal inertia (TI). The ability to store heat during the day and release it later helps buildings in dampening thermal swings, making TI a good strategy for preventing overheating in offices usually characterized by critical internal loads. Previous studies highlighted the difference between the thermal behaviour results obtained with tests on the materials, like experiments in controlled climatic chambers and real-world applications. In this study, an application of CEBs is taken as a case-study to analyse the thermal behaviour of an earthen wall and the potential of coupling night ventilation to stabilize temperatures and increase indoor comfort. Comparing the results obtained in two different rooms, representative of lightweight and heavyweight earthen construction, it was possible to quantify the contribution of CEBs walls to the passive cooling strategy in office buildings, according to different ventilation profiles/scenarios.

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https://infoscience.epfl.ch/record/231719?ln=fr

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Arianna Brambilla, Thomas Bernard Paul Jusselme
Elsevier, 2017
Article

Résumé

Official source

https://infoscience.epfl.ch/record/231719?ln=fr

À propos de ce résultat

Concepts associés (14)

Concepts associés

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Publications associées (4)

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Effect of dimensions on embodied environmental impact of buildings

Endrit Hoxha

Designers are faced with many options on material and technical solutions during the design phase of the building. Different studies proposing solutions and guidelines are presented in the literature. They help to guide the building project toward low CO2-eq solutions. Despite all these studies, the influence of building dimensions on embodied environmental impacts hasn’t been treated. The dimensions are the first parameters to be defined in the early design phase and can have significant influence in building’s impacts. In this study, we aim to introduce the relationship between the dimensions of the building and their influence in its embodied environmental impacts. Here we limit our study in the case of buildings with structure in cementitious materials, to derive some general principles for design. To do so first, we have assessed the environmental impacts of a single room by progressing its span. Secondly, the impacts have been assessed by multiplying the room in length, width and then in height, by transforming it into a building. Thirdly, we addressed the problem of defining optimal dimensions of a building and construction from an environmental point of view. Finally, the environmental impacts of two different structures, reinforced concrete beam-columns and shear-walls have been compared. According to the type of construction considered, earthquake forces and dimensions in plan and height the study identified the progression of the environmental impacts and the definition of optimal dimensions of the buildings. A good definition of dimensions can reduce significantly the embodied impacts of the buildings. However, further work is necessary for better identifying the optimal dimensions of building by adding to this work the impacts of operation phase.

2017

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Free cooling strategies are gaining importance in design practice due to the increased risk of overheating in well-insulated buildings with high internal loads such as offices. The state of the art highlights that the most efficient passive solution for indoor temperature stabilization and control is the integration of thermal mass with an optimized ventilative cooling profile to enhance the thermal cycle of heat storage. Due to its cyclical behavior, thermal mass effects are difficult to predict and quantify with the traditional steady-state approach to building thermal performance. Dynamic thermal simulations help to assess a building’s behavior under transient situations, including the thermal mass influence. However, building codes usually include thermal simulations based on standard assumptions: typical meteorological year (TMY), standard occupancy, standard daily-based lighting and appliances profiles, and standard weekly-based occupancy. Thus, when assumptions change, the actual behavior of the building may vary consistently from the predicted conditions. In this paper, we focused on the ability of thermal mass to contrast the influence of variations from the standard assumptions, especially in relation to climate and ventilation profiles. The results show the necessity of encompassing different risk scenarios when evaluating a free cooling solution performance. Among the different scenarios simulated, natural ventilation misuse shows greater influence on the thermal indoor environment, especially if coupled with low thermal mass.

2018

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Can timber lower the environmental impact of tall buildings?

Catherine Elvire L. De Wolf, Corentin Jean Dominique Fivet

The building sector is responsible for 30% of anthropogenic greenhouse gas (GHG) emissions (UNEP, 2009). Recent energy efficiency measures have helped reduce the operational carbon related to the use phase of the building, but a lack of industry attention hinders the reduction of embodied carbon related to the rest of its lifecycle: material extraction, transport, construction and demolition. Tall buildings are an evident solution to fight urban sprawl and hence reduce transportation emissions. In addition, the volume-to-surface ratio lowers the need for heating and thus reduces the use of operational energy. However, the challenge with current tall buildings is their inherent need for more structural materials. Research is needed to achieve structural efficiency in tall buildings by reducing the material quantities and choosing low carbon materials. For example, we can use mass timber to achieve skyscrapers that sequester carbon. Major engineering companies have studied the possibility of constructing timber skyscrapers. A new timber tower construction technique was recently validated, using reinforced concrete only for the connections. In composite structures, materials are used where they are most needed by combining their best qualities such as fire safety, high strength, and low density. This allows structural engineers to design using less material. This paper makes two contributions: it discusses the challenges of assessing the embodied carbon of timber materials and it characterizes the specificities of tall timber systems with built case studies.

Taylor & Francis Group2019

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