Build ‘em efficient

Our newest blog comes from Dr Veronica Ferrandiz a Marie Sklodowska-Curie Fellow in the Department of Civil and Environmental Engineering here at Imperial College London. Her work focuses on improving building materials and infrastructure.

Increasing the energy efficiency of buildings can play a key role in reducing our carbon footprint. It has been estimated that buildings in Europe are responsible for more than 40% of total energy consumption and 25% of carbon emissions. This is mainly because of the large number of old residential buildings which are very poorly insulated. In turn it is crucial that new buildings are constructed in a way which reduces the amount of energy they require for both heating and cooling purposes. In fact new EU targets require that by the end of 2020 all new buildings will be nearly zero-energy and highly material efficient. The concept of a “nearly zero-energy building” (NZEB) represents an ambitious target that is best approached in a multidisciplinary fashion.
Since August of this year I have been working as a Marie Sklodowska-Curie Individual Fellow (funded by the EU) on a project which aims to make progress on reaching this target. I am working with Professor Chris Cheeseman in the Department of Civil and Environmental Engineering. The approach we are taking is to engineer eco-lightweight granules (eco-LWG) which can be used as part of construction materials. These will have both high strength and high water absorption and be made from widely available waste materials: recycled mixed coloured glass, clay and limestone.

The granules will then be used as a carrier for phase change materials, which use chemical bonds to store and release heat as they melt or solidify respectively. Various phase change materials are available and they all have a high heat of fusion, which means they are able to either absorb or release a relatively large amount of energy as they change phase. The idea behind using granules containing phase change materials is that, depending on the ambient temperature, they will either release or absorb heat, leading to better control of temperature fluctuations inside the building and reduced energy consumption for heating and cooling.

The high water absorption of the eco-lightweight granules makes possible another application which I am exploring, using the eco-LWG in green roofs. Green roofs, or more generally green infrastructure, in our cities are now attracting lots of attention as a method to reduce the energy used by cool buildings, urban heat island effects and urban pollution.

Green Roof at the Virginia Living Museum in Newport News, Virginia by Ryan Somma
Green Roof at the Virginia Living Museum in Newport News, Virginia by Ryan Somma

The commonest substrates used are porous stone materials, e.g. expanded clays or natural pozzolanic stone. However, their extraction has a negative environmental impact. Hence it is interesting to replace them by more environmentally-sustainable substrates, which can also reduce the weight of green roofs and improve water absorbency. The properties of the granules I will make, light and high absorbent, means they will be able to first absorb and then slowly release water and nutrients to the surrounding plants, at the same time that they will reduce the total weight of the green infrastructure.

The common thread between this project and my previous research experience is that both are concerned with the reuse of waste in construction materials. This is beneficial in various ways. Not only can a waste material which might otherwise end up on a landfill be reused, but selecting a suitable waste type means the physical and/or chemical properties of the construction material can be modified in a beneficial way. For example, including waste glass in the eco-lightweight granules decreases their density and increases their thermal insulation. Previously I have researched the influence of the addition of industrial waste, in particular expanded polystyrene and paper sludge ash, on the properties of cement mortars.

Before starting the Marie Curie fellowship I worked at Imperial College on two industrial partnerships, funded by Bob Martin (UK) Ltd and Plaxica Ltd. Prior to moving to the UK I did a PhD at Alicante University, which was about designing cement mortars containing waste expanded polystyrene, to improve thermal insulation in building.

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