That is my limited understanding as well. Then again you need to use more of it, transport it farther, and still use steel and concrete in the connections and foundations.
Oct 19, 22 3:05 pm ·
·
natematt
Even with transport, the carbon footprint is much lower than concrete
The limited research I've done shows CLT is about half the carbon footprint of concrete.
1 cf of concrete = 2.06 lbs of CO2
1 cf of CLT = 0.9 lbs of CO2
Obviously this isn't taking into account any additives or reinforcing needed in concrete. Nor is this taking into account steel connections need in CLT. Also transportation isn't taken into account for either material.
I have looked at it a couple of times but it doesn't seem to pencil out from a cost standpoint unless you are comparing it to a fully concrete building, maybe tilt up. In multifamily at least, it is still way cheaper to do IIIA or VA over IA podiums.
Proto is right though its a sub for concrete or steel. The problem is that as far as I know, you can't do a lighter construction on top of it. Section 510 horizontal building separation is limited to only IA on the bottom. This in my opinion is where CLT is going to really shine, but the code has to catch up. Once you get over 6 stories though, you are back in competition with concrete or steel, maybe, but it's a large unknown at that scale for a lot of trades and gets priced accordingly. There have been a few mid/highrises that have managed to do it. Portland has a couple I think.
Chad, not directly, although I have looked into it a bit. I know of someone who might have valuable information on the subject and worked with it as an architect. I won't post the person's name publically here.
I have not personally worked on one. I think as a profession that uses so much materials it is nice to be an advocate for good environmental stewardship. I guess in the Midwest we did not have much access to GC's and the know how prowess to have a real go at it except very small projects. Usually a big developer would laugh you out of the room for suggesting a CLT mid rise or appreciate the effort but know it won't be worth the headache to push through the board review and get all trades on board.
I'm sure in areas like BC and Seattle it is much easier since the experience has a few years head start. Firms like LEVER and Michael Green obviously are getting some good projects in (wood core testing currently YIKES, but very exciting).
Have you DL'd a copy of the case for tall wood buildings by MGA? It is an interesting read and nice to see some creative connection types and research.
Here's to hoping for more carbon neutral (and sequestering) future.
My company has done a moderate amount, mostly other offices though. Local office had one big one where we recently had to switch systems for practicality reasons…. Bummer, but it was ultimately the smart choice.
Personally, I worked on one where we used CLT as a flooring system for small structures. It was effective and let us do something structural that would have been hard to do elsewise.
Panelized construction can be really great for time, staging, precision ( key words... can be).
It is likely going to be way more sustainable than other options when you run it though current carbon calculation programs.
It can actually be a cost effective option. One thing in particular is if you’re going for a wood finish, you can potentially integrate multiple parts of your assemblies.....
… which leads you to the fact that it’s attractive as a finish which is it's own benefit, but it also has potential for space savings as a structural component, and can be useful for fire rating in appropriate building types.
From what I studied of CLT can be cost-effective but I would reason that CLT is most viable on projects where the budget is a minimum of 7 digits left of the decimal point. Best for new construction projects and additions.
For the kinds of projects that the firm Chad works at, CLT can be a viable option as long as the logistics pans out. Availability, locality of CLT manufacturing and supply.
Oct 20, 22 1:41 am ·
·
natematt
Unless you’re working on TI or single family residential, you’re probably not spending under a million dollars. And if you are working on those, it’s probably not pragmatic to use anyway since its value is most easily found when you’re using it in a more intensive structural capacity.
natematt, I agree. Additionally, some small commercial buildings fit into the category but there is logistical challenges. I would agree that the higher-end SFR may be viable projects for CLT to be used but smaller budget projects might not be cost-effective for CLT at this time and those projects are less common.
Jumping on the thread, since I've been trying to bring this up more in my office ... any good book/resource recommendations on the basics, especially for what needs to be thoroughly considered vs more "legacy" building systems?
Personally I would absolutely love to work on one.
I think he meant more conventional/traditional and other building systems that have been around for a longer period. We could just view that inquiry from a comparative/contrast analysis between CLT and other building systems.
Just completed at 60,000SF single story K12 school in Washington using glulam columns and beams and a 3 ply CLT roof. Exterior walls were SIPs (structurally insulated panels) and it went up incredibly fast. We never compared the cost to more traditional methods unfortunately. The client and environment/location drove us to this system. We have looked at other projects conceptually and usually mass timber doesn't pencil. Additionally, the more regular (rectilinear) the floor plate is, the better mass timber works.
A good resource: Solid Wood: Case Studies in Mass Timber Architecture, Technology and Design
We're wrapping up a large ($60m+) CLT project. I haven't been directly involved in that one but in terms of design, it's not unlike precast concrete - most penetrations and unique intersections (etc) need to be 100% figured out prior to construction. It went up very fast.
We've also got two others on the drawing board. It's been an incredibly easy sell in our market lately, especially because everyone's still scared of steel prices. In a few days we're adopting a newer National code which allows it up to 6 storeys (instead of 4 currently) which will also help with the financial part
Where do I start ? been working on a couple of projects ( combined GFA is around 25,000 SQM ) in the past 4 years. We had 4 on the drawing board, 2 are on hold due to Covid.
I still got a trauma from an early DD which we had potential GC on board to finalise the design and lock in the supplier Europe. At the time , timber price was fluctuate weekly if not daily. All the details had to be worked out / penetration were the big one. Later on we learnt had the span of some of the beams been shorter in order to fit in standard size shipping container , we would have save ten of thousands of dollars.
Great experience though / timber is a wonderful structure.
Cross Laminated Timber (CLT)
Who here has had experience with CLT?
I've been seeing it's use more and more in mid rise projects. I myself have not done a project with it (yet) and wanted to get others opinions on it.
For those who've used it why do you think CLT is becoming more prevalent in building design?
i haven't used it, but the word I hear is: sustainability profile vs steel & conc
That is my limited understanding as well. Then again you need to use more of it, transport it farther, and still use steel and concrete in the connections and foundations.
Even with transport, the carbon footprint is much lower than concrete
The limited research I've done shows CLT is about half the carbon footprint of concrete.
1 cf of concrete = 2.06 lbs of CO2
1 cf of CLT = 0.9 lbs of CO2
Obviously this isn't taking into account any additives or reinforcing needed in concrete. Nor is this taking into account steel connections need in CLT. Also transportation isn't taken into account for either material.
CLT is also renewable.
I have looked at it a couple of times but it doesn't seem to pencil out from a cost standpoint unless you are comparing it to a fully concrete building, maybe tilt up. In multifamily at least, it is still way cheaper to do IIIA or VA over IA podiums.
Proto is right though its a sub for concrete or steel. The problem is that as far as I know, you can't do a lighter construction on top of it. Section 510 horizontal building separation is limited to only IA on the bottom. This in my opinion is where CLT is going to really shine, but the code has to catch up. Once you get over 6 stories though, you are back in competition with concrete or steel, maybe, but it's a large unknown at that scale for a lot of trades and gets priced accordingly. There have been a few mid/highrises that have managed to do it. Portland has a couple I think.
Chad, not directly, although I have looked into it a bit. I know of someone who might have valuable information on the subject and worked with it as an architect. I won't post the person's name publically here.
Thanks for the info!
I have not personally worked on one. I think as a profession that uses so much materials it is nice to be an advocate for good environmental stewardship. I guess in the Midwest we did not have much access to GC's and the know how prowess to have a real go at it except very small projects. Usually a big developer would laugh you out of the room for suggesting a CLT mid rise or appreciate the effort but know it won't be worth the headache to push through the board review and get all trades on board.
I'm sure in areas like BC and Seattle it is much easier since the experience has a few years head start. Firms like LEVER and Michael Green obviously are getting some good projects in (wood core testing currently YIKES, but very exciting).
Have you DL'd a copy of the case for tall wood buildings by MGA? It is an interesting read and nice to see some creative connection types and research.
Here's to hoping for more carbon neutral (and sequestering) future.
Thanks for resource!
A few thoughts.
My company has done a moderate amount, mostly other offices though. Local office had one big one where we recently had to switch systems for practicality reasons…. Bummer, but it was ultimately the smart choice.
Personally, I worked on one where we used CLT as a flooring system for small structures. It was effective and let us do something structural that would have been hard to do elsewise.
From what I studied of CLT can be cost-effective but I would reason that CLT is most viable on projects where the budget is a minimum of 7 digits left of the decimal point. Best for new construction projects and additions.
For the kinds of projects that the firm Chad works at, CLT can be a viable option as long as the logistics pans out. Availability, locality of CLT manufacturing and supply.
Unless you’re working on TI or single family residential, you’re probably not spending under a million dollars. And if you are working on those, it’s probably not pragmatic to use anyway since its value is most easily found when you’re using it in a more intensive structural capacity.
natematt, I agree. Additionally, some small commercial buildings fit into the category but there is logistical challenges. I would agree that the higher-end SFR may be viable projects for CLT to be used but smaller budget projects might not be cost-effective for CLT at this time and those projects are less common.
Jumping on the thread, since I've been trying to bring this up more in my office ... any good book/resource recommendations on the basics, especially for what needs to be thoroughly considered vs more "legacy" building systems?
Personally I would absolutely love to work on one.
What would you consider a 'legacy' building system?
I know for CLT you need to consider/:
Shorter spans than steel / conc
Lower number and smaller size penetrations that steel / conc
Unique lateral stability requirements / solutions
I think he meant more conventional/traditional and other building systems that have been around for a longer period. We could just view that inquiry from a comparative/contrast analysis between CLT and other building systems.
Just completed at 60,000SF single story K12 school in Washington using glulam columns and beams and a 3 ply CLT roof. Exterior walls were SIPs (structurally insulated panels) and it went up incredibly fast. We never compared the cost to more traditional methods unfortunately. The client and environment/location drove us to this system. We have looked at other projects conceptually and usually mass timber doesn't pencil. Additionally, the more regular (rectilinear) the floor plate is, the better mass timber works.
A good resource:
Solid Wood: Case Studies in Mass Timber Architecture, Technology and Design
It's often best to work the design in geometrical units of the building material/assembly to minimize waste.
RMI institute in Basalt is built with all CLT, I had a guided visit during construction. It's a nice building. https://rmi.org/our-work/build...
We're wrapping up a large ($60m+) CLT project. I haven't been directly involved in that one but in terms of design, it's not unlike precast concrete - most penetrations and unique intersections (etc) need to be 100% figured out prior to construction. It went up very fast.
We've also got two others on the drawing board. It's been an incredibly easy sell in our market lately, especially because everyone's still scared of steel prices. In a few days we're adopting a newer National code which allows it up to 6 storeys (instead of 4 currently) which will also help with the financial part
Where do I start ? been working on a couple of projects ( combined GFA is around 25,000 SQM ) in the past 4 years. We had 4 on the drawing board, 2 are on hold due to Covid.
I still got a trauma from an early DD which we had potential GC on board to finalise the design and lock in the supplier Europe. At the time , timber price was fluctuate weekly if not daily. All the details had to be worked out / penetration were the big one. Later on we learnt had the span of some of the beams been shorter in order to fit in standard size shipping container , we would have save ten of thousands of dollars.
Great experience though / timber is a wonderful structure.
i was typing from a phone, ignore my bad spelling/ grammar.
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