Living Box – Prefabricated modular wood-house system - Part V - KEP energy Magazine - KEP energy

Living Box – Prefabricated modular wood-house system

English translation from a paper published in 'Bollettino degli Ingegneri n. 6/2016 pp. 3-18'

Living Box environmental performance

The Living Box project can be seen as a paradigm of the sustainable building design concepts. It is addressed towards the achievement of many requirements typical of the sustainable buildings: energy efficiency, materials consumption optimization, low environmental impact from a Lyfe-Cycle point of view, indoor comfort and healthiness, safety during the manutention phase. The one exception to this perspective is the impossibility to customize the relation between the building and its surround, due to the Living Box intrinsic decontextualization.

Most building sustainability requirements can be really achieved regardless the criteria or methodologies used to verify their achievement. As know, indeed, beyond the fundamental principles, the built environmental performances can be assessed through many indices and parameters, also during the design stage, as in the Living Box case.

Overall, the Living Box is able to meet the building sustainability requirements explained in the following paragraphs.

Energy demand minimization during the building lifetime

The energy demand minimization is a fundamental topic in the sustainable buildings field. The main environmental impact of a building, during its lifespan, is due to the energy consumption during the use phase: heating, cooling, Domestic Hot Water (DHW) production, ventilation, illumination, etc. The option of the nZEB concept as project target proves the high energy performance achievable from the Living Box, particularly considering that it is a prefabricated modular wood-house system.

A wood-house system, having the thermal insulation formed by wood too, allows a relevant improvement of the overall building energy performance in hot climates or during the summer time, in comparison to the conventional systems currently used for the temporary housing. Indeed, these systems are characterized by low building envelope mass, that is by low thermal inertia. The building envelope thermal inertia is a relevant requirement in the temporary housing field, because the buildings could be installed also in hot climates. Many worldwide areas in which occur natural disaster, extreme weather events, migrations and urbanization, are characterized from high outdoor temperature and high solar radiation.

The lightness of the building envelope components is suitable to facilitate the carrying and the installation operations. Currently are widespread temporary housing built by metal frames bearing structures, coupled with dry-assembled beared walls. However, it implies a low energy performance from the thermal inertia point of view. The thermal wave delay factor of the conventional systems is approximately 4 hours. Instead the Living Box one is approximately 12 hours (calculated in compliance with the UNI EN ISO 13786:2008 standard). The wood is a material characterized from a high specific heat. Consequently, a thick multilayer panel composed from wood derivatives allows to reach a high building envelope thermal inertia.

Besides the high walls energy performance, also a high windows energy performance has been taken as target in the Living Box design. The design is particularly careful to the solar radiation management. Among the building optional components are included also projections, sunblind, etc. In order to optimize the solar radiation management, the building should be oriented in reference to the specific geographic location, taking in account the latitude and the local South-North direction.

Dry-assembled building components

The use of dry-assembled building components is suitable in order to reach a low environmental impact of the Living Box during its overall Life-Cycle. Only the foundation derogates from this perspective. Indeed, it should be made in reinforced concrete, especially in the locations characterized from a high earthquakes dangerousness. The sustainability of the dry-assembled prefabrication is endorsed from many bibliographic references, which show its environmental impact minimization ability. This topic can be deepened through the following references: Quale et al, Jallion et al, Landolfo e Russo Ermollo, Dattilo et al. Also, reference can be made to the British Society Buildoffsite. These references assess the prefabrication suitability taking in account the energy efficiency, the CO2 emissions, the yard management and the overall building quality.

From one hand, (building cradle) the prefabrication reduces the materials waste and optimizes their costs (in agreement with the TBL concept: environment, economy, society). From the other hand, (building grave) the dry-assembly facilitates the disassembly and the materials reuse or recycle. Particularly, these last option is relevant in the temporary housing field, which is characterized from a basically short lifespan.

Further benefits of the dry-assembled building components are also the installation phase simplicity and the yard phase rapidity. Indeed, the builders safety increases, the installation time decreases as well as the yard fouling. These benefits are common both to Living Box and to others dry-assembled systems, included the “X-lam” typology or the “platform frame” typology wood buildings.

Building materials sustainability

The wood is a low environmental impact building material, also for the energy efficiency that it brings to the building envelope (as explained in the paragraph 3.1). This statement is globally agreeable, despite during the Living Box design stage has not been made an analytical assessment of the wood sustainability. The Living Box thermal insulation layer is formed by wood derivatives. Also, the internal and external surfaces finishes are built in wood-compatible materials. The building envelope components design has been carried out developing for each component typology (e.g. wall, roof, etc.) the layers set able to minimize the materials environmental impact, maintaining unchanged the overall component energy performance.

As positively found in other similar studies and research projects, the developed layers sets are able to minimize the Global Warming Potential (GWP), the Primary Energy Intake (PEI) and the Acidification Potential (AP) indices. These indices have been taken in account individually, without relate the various assessment results to one global index through a normalization procedure.

In this way, it has been possible a compromise between assessment harshness and simplicity, developing a series of building envelope components that are checked as “sustainable” not only from the qualitative point of view but also from the quantitative one.

The materials healthiness performance towards the building users has been verified in compliance with the most rigorous protocols of indoor quality assessment, as GEVEMICODE 1 plus, NaturePlus, Ecolabel, ANABICEA. It, particularly, in reference to the surfaces finishes materials. These protocols are favourable also to achieve the LEED, BREEM, ITACA certifications.

Almost totally building disassembly, as sustainability target

The option of almost complete Living Box disassembly allows to bring back the installation soil to the original engagement, once finished the temporary circumstance to which is due the installation. So, the Living Box lifespan is almost totally reversible, from a soil point of view (and not even from an entropic point of view). This ability facilitates the installation soils detection, even in highly warded contexts, because the building impact on the landscape is minimal.

It is appropriate underline that the soil use, and its permanent or temporary engagement, is a relevant sustainability topic that must be taken in account.

Multi-disciplinary integrated design

Many building eco-labelling schemes, as LEED and BREEAM, boost a multi-disciplinary project vision. The typological, functional, technological, architectural, structural and energy aspects must interact at the same time among them, up to the early design stage. The Living Box originated implementing this project vision, since its design has been the deep analysis of a basic living unit.

The multi-disciplinary integrated design is suitable from the sustainability point of view, because it optimizes the design stage, brings equilibrium, reduces wastes, minimizes the yard variables and risks, and allows a high building affordability and durability.

For these reasons, the Living Box can be considered a sustainable project, despite have not been made specific assessments, as the eco-labelling (although in a preliminary manner). Anyway, the use of low environmental impact building materials and the optimization of the carrying and installation operations, allow to expect a high overall building performance.