The biggest impact approach to reducing embodied carbon (EC) in every building is optimizing the structural framing as discussed in our article on How to approach embodied carbon reduction on your project. Calculating the effective embodied carbon for walls may seem difficult at first, but we've broken it down into just a few steps to help during the design process. The area-based embodied carbon method below is to quickly estimate the initial embodied carbon of metal or wood-framed building during the design process.
Why include framing for embodied carbon reduction?
Framing in cove.tool is associated with the Wall Insulation engineering input. The assumptions for cove.tool are based on code minimums and PNNL prototype building definitions as described in our article on Walls. The embodied carbon value provided is for the wall insulation only. To study the effective impact of different framing options users can type in a custom wall type that takes into account the specific framing material and dimension.
Use the "+" sign to the right to add a new product and fill in the information, or you can use an existing insulation product and change the name. Note that the effective R-Value may need to be recalculated if you are using wood framing on mid-rise or high-rise buildings, or steel on low-rise buildings. Be sure to know your own design.
Area-based embodied carbon method
The embodied carbon of a wall assembly is the summation of all layers included in the wall assembly, but the embodied carbon is dominated by the insulation and framing. Therefore, the embodied carbon value for insulation and framing should be entered. Interior covering is part of the Interior Finishes tab and not included here. Exterior cladding is not as significant for embodied carbon as framing or insulation but can be added to the result of this calculation if desired.
Wall embodied carbon (kgCO2e/ft^2)
= Insulation (kgCO2e/ft^2) + Framing (kgCO2e/ft^2)
We need to find the amount of embodied carbon per square foot (kgCO2e/ft^2) for both insulation and framing. A list of ranges and suggestions are provided in our article on How to Approach Embodied Carbon Reduction and can be referenced for embodied carbon values.
For insulation, this value is already provided as kgCO2e/ft^2.
For framing, it needs a little math to get to the same unit of kgCO2e/ft^2. Once the framing calculation is done it only needs to be added to the insulation embodied carbon value.
Below are methods for the estimated embodied carbon calculation for metal and wood framing.
Framing with Metal Studs
Formula:
Example:
1. Start with your known values...
Spacing: 16" = .75 studs per linear foot (24" = .5 studs per linear foot)
Weight (lbs): A 5.5" sheet metal stud = 1.44 lbs / ft. (you can look up this value by manufacture. Here is one option.)
Wall Connections & Waste Factor: A percentage factor estimating the number of connections between walls, floors, openings, and an average amount of wasted material. This can typically range from 15% - 20%.
Embodied carbon value: From the EC3 database the median conservative value for steel is 3.265 kgCO2e/lbs.
2. Multiply these values together to get the amount of kgCO2e/ft^2 of your walls...
0.75 x 1.44 lbs/ft x (18%+100%) x 3.265 kgCO2e/lbs = 4.1609 kgCO2e/ft^2
3. Add this value to your Insulation embodied carbon value and type the result into cove.tool selecting area as the multiplier.
Framing with Wood Studs
Formula:
Example:
1. Start with your known values...
Spacing: 16" = .75 studs per linear foot (24" = .5 studs per linear foot)
Cubic Yards per Stud Foot: A nominal 6" wood stud = 0.04 ft3 (this online tool can help with the conversion.)
Wall Connections & Waste Factor: A percentage factor estimating the number of connections between walls, floors, openings, and an average amount of wasted material. This can typically range from 15% - 20%.
Embodied carbon value: From the EC3 database the median conservative value for steel is 103.4 kgCO2/ft3.
2. Multiply these values together to get the amount of kgCO2/ft2 of your wall...
.75 x 1.44 lbs/ft x (15%+100%) x 103.4 kgCO2/lbs = 3.5673 kgCO2/ft2
3. Add this value to your Insulation embodied carbon value and type the result into cove.tool selecting area as the multiplier.