I have two questions about whole building LCA. I have a client who wants to evaluate the impact of wood vs concrete building construction.
- Just by a quick look at the raw material extraction phase, the impact of concrete construction is higher. On the other hand, by looking at the whole lifecycle assessment from cradle to grave the impact of building with wood might be higher, is this normal? Im keeping the total U value for the building envelope the same in both criteria.
- For the selection of materials, there is a big database available in the software (I’m using Oneclick LCA). The CO2 emissions vary considerably… what is the priority for material selection since we have this huge difference?
- In case of selecting materials from other country, just for calculations, does it really makes sense, since theoretically it is very difficult to get these materials in the country where the project is located…?
Hi Nove. Responding to your points:
- When comparing two different building systems as you are, the assessment should be at least A1-A5 to make a proper comparison. If the timber design is inefficient and using a lot of timber you may find the timber option has a larger carbon impact. It would likely indicate that the timber option needs to be further optimized.
- The selection of data should be based upon project stage. If you are at an early stage of the project (which it sounds like you are), you should use industry-average values regionally relevant to the location of the project.
- See response to #2.
Thank you so much for this repy. Indeed, this is what I also believe and what I did. Yet, my client just believes that wood is the best option ever , whatever the circumstances…Yet, there are various circumstances that should be considered, to make sure both options are equivalent at the first place…
Im loving the discussion about this topic, more discussion is welcomed…
We have been doing this type of comparisons and wood typically is still much better than concrete, regardless because timber wood is a carbon sink, wood has carbon storage properties. OneClick LCA should be giving you a graph result for the biogenic carbon of the building in wood. I’d be interested to know what building type is. Also, you might need to check the weight of the wood that you are using because wood is a lighter material compared to concrete, make sure you are accounting the material correctly.
You should be comparing against national averages. In the US NMRCA national averages. If is an international project depending on the region, for example Latinamerica, wood is limited, and construction is typically concrete, I would recommend using 0% Secondary cementitious materials in the concrete selection, until you can confirm that they will be using SCMs in the concrete mix. They do have Slag or fly ash on cement in Mexico and Brazil for example, but contact the batching facilities to learn about their mixes in the country that the project is located.
I’d be interested to see how this progresses. In the projects that I’ve worked I’ve seen 20-50% carbon reduction including biogenic carbon, depending on how much of the building structure/envelope you build with wood.
Another thing that forgot to mention is that for every material that we have been suggesting that is better in terms of carbon compared to concrete we have been asked to look at the disassembly benefits (D) because wood elements if designed/assembled correctly should be able to be reused multiple times. I do have questions regards to this, because I don’t know to what extent the program and EPDs are considering this. I visited a project totally constructed for disassembly that can be deconstructed and reassembled in another place if needed.
Not sure of the scope of your analysis but you might be seeing a national average for the wood. It is certainly the case that wood is not always grown and harvested sustainably. Look for certifications and don’t forget to research the certifying body as certified wood is a growing field and there are all of the usual players, both good and not quite good, in the game.
Biogenic carbon is an important factor.
Thank you for your reply. Yes indeed, wood alone is a good source. Yet, since we have to care about the building envelope (as the functional unit), we also need to account for the overall U value for all the layers used in case of concrete vs. wood construction. I think this is also important to consider
I would suggest https://tangiblematerials.com/ as a potential source of information on this topic.
I am not affiliated - just sharing a potential resource.
Thanks for sharing!
I already had a look at it.
The problem is I’m working on various projects, most of them are in the Middle East and Africa area where there is no data. Now, I’m using one click LCA and I have the following question regarding the order of materials selection.
- First try to select the material from the same country (which is impossible, since these areas do not have any data)
- Select a material from a nearby country and then add the additional transportation for the emission?
We have already discussed the selection criteria and the order (industry wide average and then material specific), but what if there are no data at all either industry average or manufacturer specific? just count on the localisation method provided by the software and then try to find a material with similar emission from the local industry (as still you cannot get this material as it is far away)
Any idea on this? This is really a big topic
Thank you for the reply. One more question regarding the order of Materials selection, since you are working in Latin America (with limited data as well). I have projects in the middle east and Africa, where there are no data, how would I select my materials? other than industry wide average and manufacturer specific for this country (do not exists), can I select a material from another country and just add the impact of transportation? or just any materials and depend on the localization method of the software and then call the local manufacturer and try to get something similar?
@Neveen - I’ve not heard of a good solution to determining impacts of products in areas without data. I can’t say for certain without seeing the EPD, but industry averages are generally regional, so a north american industry average would be different from a european industry average. If you were to procure the product from another country, yes, your method of using that data and including transportation data would be correct. If you’re procuring it from within the area without data, that solution would not be representative of the product impacts or the transportation impacts.
In a situation where there’s no data, working with the manufacturer to get an EPD would be ideal, but without that, it would be a judgement call off of the data from other areas. How is the manufacturing process in the area (say for steel, are they using blast furnaces - worse - or electric arc furnaces - better)? What about the grid in the region (is the grid clean - may be lower impacts - or dirty - likely higher impacts)? It would be bad data, but it may be better than no data.
If someone has a better solution, I’d love to learn.
@jschwartzhoff indeed I agree with your suggestion. I would also love to hear from others…