A sustainable hybrid building system using wood and concrete that is based on the Life Cycle Assessment of buildings and their products from resource extraction to demolition and re-usage.

About this project

LCT ONE, an eight story wood office building, is a prototype, a proof of concept that demonstrates an innovative process and product. It is based on CREE's LifeCycle Tower system design which has the potential to reach thirty stories. LCT ONE focuses on reducing the negative impact of buildings on the environment, while improving the comfort and indoor air quality for the occupants.

CREE's LifeCycle Tower system was conceived as a way of constructing with the least impact on scarce resources, as well as the lowest emissions of waste and CO2, and has been nominated for the Austrian Federal Ministry of Economy, Family and Youth's National Award for Innovation.

Since then, further projects have been built and are currently under construction, including residential and public buildings.

Watch the timelapse for LCT One construction here

An LCA based approach

A sustainable building strategy considers the entire Life Cycle of buildings and their products. This includes resource extraction, material production, construction, operation, demolition and re-usage. LCT ONE began as a R&D project based on the Life Cycle Assessment of buildings. The motivation was to find a substitute for traditional construction which plays a major role in causing our climate crisis. Our population is growing and the trends are shifting. People are moving from rural to urban areas. Cities must find new ways to grow, around transit systems with sustainable developments that don’t deplete our resources and harm our environment. Therefore cities must readapt to the current changes. We can no longer afford to build our cities using materials based on fossil fuels such as concrete and steel, using archaic methods resulting in long construction schedules and cost overruns. LCT ONE is a prototype solution that presents an alternative, a concept to introduce a Natural Change in Urban Architecture, which is based on a renewable resource, wood.

The LifeCycle Tower (LCT) R&D project resulted in a process; a system and a product culminating in the design and construction of LCT ONE. The result was a sustainable shell-and-core wood-concrete-hybrid system for mid-rise and tall buildings that can go up to 100 meters and 30 stories and meet local building code prescriptions.

Key considerations in this process were:

Forestry Carbon Cycle

Wood is a renewable resource that grows from the sun. It is the ultimate solar product. Forests and their trees absorb carbon while giving us oxygen. Modern, timber based products, such as engineered lumber, are available worldwide. Heavy timber glulam members are stable, will not shrink and twist, and by using modern industrial methods, it is possible to pre-cut and prefabricate components to exact tolerances, which are air-tight, resulting in saved energy. At the end of a buildings’ life, the wood can be re-used for other purposes and later turned into fuel and energy. The use of wood is carbon neutral.

Ecological Backpack

The selection of building materials must be linked to the use of natural resources, including raw materials (renewable and non-renewable), energy, water and land. To specify products for the LCT system, data was collected and calculations performed to measure the total amount of natural resources required to produce a certain product or building. Because trees grow above the ground, it is resource and energy efficient to extract and produce wood as a building product. Wood has a much lower ecological backpack than traditional materials such as concrete and steel.

Prefabricated Construction Process

Europe has a long history of prefabricating high performance building components out of wood. The process begins with CAD software used to cut lumber using CNC machinery. The members are assembled in a carpentry shop, under a controlled environment where windows, insulation, sheathing, vapour barriers and finishes were installed. The components are made to very tight tolerances and can be quickly assembled on-site and meet the most stringent blower door test prescriptions. Modern timber technology is available and can deliver high-performance buildings using renewable resources.

Operation and Maintenance

Existing buildings consume too much energy during their operational life. To reduce consumption, the LCT system was developed according to the Passive House Standard introduced in Germany. It is one of the most stringent energy standards in the world. The strategy is to drastically reduce consumption before relying on renewables. This is the surest path to reach Zero Net Energy. Highly efficient solar and mechanical equipment have an ecological backpack, therefore “less is more”, no need to heat and cool is more sustainable than heating and cooling with renewables or high efficiency equipment. To guarantee maintenance and durability, a building science consultant is part of the integrated planning team and advises on the permeability and diffusion of the entire building enclosure. The most important aspect is air-tightness which prevents air and moisture from entering the building envelope. Additionally, the exterior finish material of the building is always installed on a rain screen, creating a ventilation layer behind it and allowing any water penetration to drain before it reaches the building envelope.

Urban Mining

All building products originated from mining the earth. At the end of their lives, buildings are typically added to landfills and new materials are mined. The LifeCycle Tower R&D project strived to develop a solution where, at the end of the life of a building, re-usable materials are saved from landfills. Urban Mining conserves our natural resources, eliminates potential energy costs and greenhouse gas emissions. When a building has reached its full useful life, urban mining of the LCT system can be activated, extracting materials to re-use, recycle and convert into bioenergy, thus protecting landfills from unnecessary waste.

Further information

Images: Norman A. Mueller and Zumtobel Lighting

Project details

LCT residential projects


Key contacts

Client / Contractor

CREE by Rhomberg


Architekten Hermann Kaufmann ZT

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