How to Build with Zero-Kilometer Wood? The Experience of The Voxel in Barcelona

Written by Fabian Dejtiar | Translated by Nicolás Valencia
Published on August 13, 2021

Zero kilometer materials can be purchased locally, do not need to be transformed by large stages of industrial processing or toxic treatments and, at the end of their service life, they can be returned to the environment.

For example, wood from a nearby forest eliminates the need for long transfers, valuing local resources, and allowing architecture to lessen its environmental impact while committed to the landscape and context.

So, the question has to be asked: What does it mean to build with zero-kilometer wood?

A great example is The Voxel, a quarantine cabin in the Collserola Park (Barcelona) built by students, professionals, and experts of the Master in Advanced Ecological Buildings and Biocities (MAEBB) of the Institute of Advanced Architecture of Catalonia (IAAC) at Valldaura Labs.

The Voxel, or volumetric pixel, is a 12-square-meter (129 square feet) cross-laminated timber (CLT) structure made of Aleppo Pine (Pinus halepensis) that was milled, dried, processed, and pressed on-site at Valldaura. All timber used in the project was harvested within a radius of less than 1 kilometer (0.6 miles) from the construction site.

As the authors describe, it is first necessary to know the forest cycle. In this case, based on a sustainable forest management plan approved in Collserola, a certain forest volume can be obtained each year to encourage the growth of smaller trees and biodiversity, because forest biomass grows by 3% each year and growing trees absorb more CO2.

To supply the raw materials of the project, 40 pine trees were harvested and cut into 3cm boards, and stacked to dry for three months.

After they reached the proper humidity level, each board was taken into the Valldaura Labs carpentry to be processed into hundreds of pine lamellas. Each lamella was then encoded into a specific sequence, tagged, and pressed into more than 30 structural CLT panels which were assembled into a 3.6x3.6m cube.

How to Build with Zero-Kilometer Wood? The Experience of The Voxel in Barcelona - Image 3 of 8 — Cortesía de Valldaura Labs

Each sheet was encoded in a specific sequence, labeled and pressed into more than 30 CLT structural panels that were assembled into a 3.6x3.6m cube. Each sheet of each panel was tracked and located, ensuring that each wooden element in the house can be accurately traced to the point of knowing which exact tree it came from.

The panels were held together metal-free with lap joints and wooden dowels, inspired by a commitment to use less carbon-intensive materials. The structure was then wrapped in a layer of cork insulation and mounted with an innovative series of rain-screen panels made from waste material created during the CLT production process.

Cork insulation was placed over the wooden panels, and a burnt wooden skin was placed over it, using the Japanese Shou Sugi Ban technique, which protects the building from rain.

While processing raw pine boards to get perfectly rectangular lamella, the organic edge of the board usually goes to waste. However, these off-cuts were turned into a facade that showcases the organic complexity of the tree that is usually hidden in most wooden constructions.

This article is part of the ArchDaily Topic: Local Materials. Every month we explore a topic in-depth through articles, interviews, news, and projects. Learn more about our monthly topics. As always, at ArchDaily we welcome the contributions of our readers; if you want to submit an article or project, contact us.