We are developing an Office Building in Spain. The structure above grade is made with wood (CLT).
We are studying the differences between the GWP impact of that proposed building (CLT structure) with a baseline (reinforced concrete structure). Both, proposed and baseline have similar below grade structure made with reinforced concrete.
We have found that, talking in m3, the amount of CLT and reinforced concrete above grade is similar, in fact we are using more m3 of CLT structure than concrete. We are aware that the kg are higher in the case of reinforced concrete structure.
What surprises us is that 1m3 of CLT can have similar kgCO2/m3 than 1m3 of concrete. ¿why is this possible? We expected to find big differences between CLT and Concrete, no matter the type of CLT or Concrete, but it is not the case.
The program is taking into account same location and same transport for each CLT option. The different CLT options included are from 450 to 550 kg/m3
To sum up: we were expecting that the results of A1-A3 of CLT structure (without biogenic carbon) would be much lower than the results of A1-A3 of Reinforced concrete strcuture, but if we compare both structures with similar m3 of material, results are not reflecting that difference.
One of the reasons we are considering is the election of CLT.
We have found big differences between the CLT options. ¿why is that?
We will start conversations with the 3th party behind the EPDs of CLT to see how the impacts of A1-A3 were calculated.
We don’t think the inclusion of biogenic carbon or not could be the issue.
The transport it is not the issue, neither the location.
Can be the FSC certificate the main reason of the different results?
If it is the main reason, a final conclusion I see is that, not always a CLT structure will have less GWP A1-A3 than a Reinforced Concrete structure. We will have to be sure that the CLT is FSC, if its not, the final GWP could be similar to the reinforced concrete option.
Does anyone have any comments that can bring some light?
thanks a lot!