Are Cree’s Fire Resistance Certificates valid in my country?
You should check this with your local authorities. Our European test facility has been awarded an official international certificate. The test was run in accordance with European testing standards. The fire rating can also be calculated according to the European classification system.
Are there any particular specifications on insulation?
There are no specific requirements; the insulation complies with normal regulations. Any standard product on the market can be used. We prefer products, which have a low environmental impact, particularly with regard to low VOC emissions.
Can a Cree building be LEED certified?
The LCT ONE is LEED Platinum certified, and also DGNB (the leading European green building certification programme) Platinum certified. The IZM is also DGNB Platinum certified.
Can a Cree building become a Certified Passive House?
The LCT ONE has become a Certified Passive House according to the Passive House Standard of the German Passive House Institute under Dr Feist in Darmstadt. The IZM incorporates the Passive House Standard, but it has not obtained the certification.
Can insects/termites harm the Cree structure?
With regard to decay and harmful insects, thermally treated wood (like the common engineered wood that we use) is resistant to such infestations, except for termites. High risk of termite infestation in any structure requires standard treatment. The fact that we do not cover or clad the wood or add any other layers means that it is easy to detect any potential termite infestation. This is a major advantage of our system compared to other methods of constructing wooden buildings.
Can the Cree system compete with concrete?
The cost of a Cree building is generally similar to the cost of a conventional building when the building is “designed to Cree” and not “designed to concrete”. Total lifecycle costs (including the operation and end of life of a building) are significantly lower for our buildings, as proven by the monitoring and subsequent evaluation of existing Cree buildings.
Can the glulam have different finishes?
The glulam can have different finishes, such as oiling or painting, as long as changing specifications do not contradict technical requirements. The glulam can even be made from hardwood.
Can you also incorporate CLT?
CLT can be an excellent addition for creating core walls (if it complies with local regulations), bracing wall elements, shafts and stairs, and even non load-bearing curtain walls.
Can you include set-backs and balconies using the Cree system?
Set-back storeys are feasible, particularly on the top floor. Balconies are also possible.
Does the Cree system have any defects or drawbacks?
There are no major defects or drawbacks. We incorporate minor changes into every new project, so that we are continuously improving our design and construction systems.
Does the design have an impact on cost?
Traditionally, the main cost driver is the fact that the majority of buildings are “designed to concrete” and not “designed to wood”. This makes them much more expensive if you simply want to transfer their design and construction to Cree’s LCT system. It is not possible to design and construct a building to concrete specifications for the same cost using the Cree system by simply replacing the concrete with wood.
Does the hybrid panel allow for vertical shaft openings, and if so, what size?
Shaft openings are possible between the beams. Their size depends on their location, and is also subject to structural verification.
How are the loads carried?
All gravity loads are carried by the posts/columns and the core. All lateral loads are transferred to the core. Neither the pin connectors (post-slab-post) nor the posts/columns are torque-resistant.
How can architects and planners use the Cree System?
Architects and planners can use BIMobject and the Cree System to create a preliminary draft for a tender or building approval process. After approval has been granted, we can provide you with the necessary detailed technical information through our licensed partners.
How can glulam components be repaired if they are damaged or dirtied during construction?
We usually repair damage and stains simply by sanding. Cree has developed a number of protection strategies, and we are happy to share these with project team members on site. Serious damage is unlikely but can be easily repaired by a skilled carpenter.
How do you adapt to local building regulations?
It is best to involve the local government and the authorities right from the start of a project. It is particularly important to maintain a dialogue with the authorities when exceeding certain restrictions. In terms of approvals, the situation in Austria was very restrictive before 2010 when we launched the LifeCycle Tower and Cree. The first project (LCT ONE) was approved despite the fact that it was double the approved height (8 storeys rather than 4 storeys). Today, just 4 years after the construction of LCT ONE, we are talking to the authorities about buildings as high as 30 storeys.
How do you handle the different compressive deformation of wood compared to concrete?
According to our calculations, no significant difference in shrinkage and creeping is to be expected. We have confirmed this through structural monitoring of LCT ONE over the last 3 years.
How do you meet fire resistance requirements?
Cree has demonstrated the fire resistance of its building components through a number of fire tests conducted according to European fire standards. The main component, the wood-concrete hybrid slab, has a fire resistance rating of at least 2 hours. Some of the geometric and structural properties of Cree’s wood-based building system are very different from those of other timber buildings. Mass timber products are actually very slow to ignite. Wood is only used for posts and beams, so it is difficult for fire to spread from one timber member to the next. We do not cover, clad or add any other layers to the wood that would conceal its surface, so it is easy to inspect and access at all times. The concrete portion of the wood-concrete hybrid slab features continuous non-combustible floor-to-floor compartmentalisation. All steel parts (screws, connectors, etc.) are fully covered by either concrete or wood.
How does air moisture affect the wood?
In Cree buildings, the wood is always enclosed. Its moisture content remains stable because it is never exposed to changing climate conditions.
How does the cost of concrete, steel and whole timber structures compare?
Numerous studies show that the cost of a Cree structure exceeds the cost of a conventional structure by 5-10%, with overall building costs tending to be less than 5% higher. Whole timber structures are usually more expensive because of the greater quantities of wood involved. We have not studied steel structures as they are not common in Europe. We believe the use of steel is even less environmentally friendly than the use of concrete.
How does the Cree system perform in seismic areas?
Cree has already successfully explored these issues for a pilot project in the San Francisco area, and the results have been reviewed by several expert peer groups. One expert stated: “While we construct more and more high-rise concrete, and while building codes ensure these buildings will not necessarily collapse in a major seismic event, will they be habitable after an earthquake? … Certainly wood framed buildings can be habitable post-earthquake. So can wood be built higher than 6 storeys? Yes, and mass wood leads the way.” Cree also analysed laterally induced displacements, such as strong winds and seismic events, as part of its original LifeCycle Tower research project. The results showed that the Cree LCT system performs even better than concrete structures.
How does wood resist consistently high levels of humidity?
Like clay, wood is able to balance humidity if indoor conditions are consistently damp. We do not cover, clad or add any other layers to the wood, so standing water cannot gather on its surface. This is a major advantage compared to other timber building methods.
How is the basement joined to the wooden posts/columns?
The posts/columns stand on metal plates, which are screwed into the concrete basement. At the upper levels, the posts/columns also stand on metal plates and are connected by pins and tubes. All load transfer happens through grouting.
How long does it take to go from the skeleton frame to finishing?
Depending on the specifications for the interior and the manpower available, finishing takes up to one week per floor. It happens in a weather-sealed environment, so not in the skeleton state but in completely enclosed indoor conditions.
How much can you save on building the basement because of the more lightweight structure?
Our existing Cree buildings reduced the cost of groundwork, foundations and basement by 30-50%.
Is there a patent on Cree’s hybrid panel?
The international patent is pending. Patents in the EU, U.S. and Canada are in force.
What are licensed partners?
Cree’s system processes and physical components are made available only through our licensed partners. Licensed partners are general contractors or developers.
What are the basic design rules?
The posts/columns stand 2.70 m on centre, but variations are possible. The slab spans 8.10 m, which is the fire-tested span. Shorter spans would be covered by the Fire Rating Certificate, but longer spans are possible. The size of the core area depends on its bracing requirements. A typical core uses less than 20% of the footprint.
What does your system cost?
If you just take the load-bearing timber-hybrid structure (including timber-concrete hybrid slabs, resting on posts/columns or similar bearing points), the cost in our market (Austria) would be around 250 EUR/m2 (of system-covered floor area). If you also include the timber frame and non-load-bearing exterior wall elements, we would calculate about 350 EUR/m2 (of system-covered floor area). In this case, you would get a fully enclosed building volume.
What happens if a water pipe bursts or sprinklers go off?
The concrete portion of the wood-concrete hybrid slab protects all timber elements from water in the event of burst pipes or sprinklers discharging. We do not cover, clad or add any other layers to the wood, so standing water cannot gather on its surface. This is a major advantage compared to other timber building methods.
What happens if it rains during construction?
During assembly, contact with water should not exceed a certain limit but, even in the event of heavy rainfall, engineered wood is not very sensitive. It can withstand a great deal of moisture as long as it is subsequently dried out.
What if there is a shortage of local expertise in timber design and construction?
We have set up a training and development programme to introduce you to all the relevant technology, processes, design tools, databases and other necessary information. You will receive our full support throughout your first local project. After that, a central support team will be on hand to solve any unexpected problems, but we are confident that all the members of the project team will quickly become familiar with the Cree system and our design and construction methods.
What initial support can Cree give me?
As part of the Master License process, Cree provides extensive training (four phases) and full support in your interactions with peer reviewers and authorities. Our training and development programme will introduce you to all the relevant technology, processes, design tools, databases and other necessary information. You will receive our full support throughout your first local project.
What is the connection between timber-hybrid building, BIM and IOT?
Our holistic approach is not limited to timber-based construction but also includes the inherent relation between building with wood, lifecycle design, prefabrication, BIM (Building Information Modelling) and the IOT (Internet of Things).
What is the glulam made of?
The glulam for the existing Cree buildings was made from spruce. Fir and pine (softwood) are also common in Europe. We don’t need to use particular tree species, we just use the most common varieties.
What is the heat transfer coefficient of the walls, as a sign of their degree of insulation?
This depends on building physics calculations in accordance with local building regulations. Any heat transfer coefficient can be chosen.
What is the maximum height of a Cree building?
At the moment, we are in discussions with the authorities on buildings up to 30 storeys, or 100 m, high. In theory, there is no technical height limit for timber-concrete hybrid buildings.
What is the sound insulation performance of a hybrid deck?
The sound insulation performance of a hybrid floor panel, if there is no additional build-up or flooring, is 50 dB airborne sound reduction and 80 dB impact sound level.
What kind of chemicals do you use for treatment?
The glulam for the existing Cree buildings has not been treated. This is not required for fire resistance or any other purpose.
What kind of diaphragm connectors do you use in seismic areas?
In the past, we have used threaded couplers and welded plates for seismic connections. In the meantime, we have had some very good experiences with looped steel rope connectors.
What kind of insulation materials do you use, and what size?
We use mineral wool from renewable sources, due to fire resistance requirements. Its thickness depends on building physics calculations in accordance with local building regulations. The existing Cree buildings use mineral wool up to 320 mm thick (2 layers at 160 mm), but any size can be chosen.
Where can the Cree system be viewed online?
BIMobject provides a simplified illustration so that you can view the Cree System and create a preliminary design for a tender or building approval process.
Where do you place the insulation material in the wall?
The exterior walls may be timber-framed and filled with insulation, but other exterior wall systems can also be used. The insulation layer and vapour barrier run continuously in front of the posts/columns and slab edges.
Why does the Cree system use glulam?
Glulam provides the best price/performance ratio to achieve the lowest possible material input, provide the longest spans, and hence create the most flexible space.
Would the hybrid floor panels be produced locally?
The floor slabs would be produced locally. Cree would accompany and coordinate the process for the prototype project only.