Our Panel Calculation: How Many Trees Does Plantd Save Per Single-Family House?
To make products like Oriented Strand Board (OSB) for residential construction, building materials manufacturers use trees like loblolly pine that are grown on managed timberlands. This lumber is called pulpwood and is composed of either the waste material of large trees or the whole material of smaller trees.
Loblolly pine is commonly harvested on managed timberlands across the Southeast region of the United States. According to the United States Department of Agriculture, loblolly pine grows to a diameter between 4-13 inches. These trees are typically harvested 10-15 years after planting and range between 30-70 feet tall at harvest.
This post shows the math we use to calculate how many trees our grass panels replace in the construction of an average-sized single-family house.
Tree calculations are complicated by the fact that trees are not of uniform size and height. So we make a few assumptions along the way.
This is the framework we follow:
Step 1: Calculate the volume and mass of a loblolly pine tree grown for OSB production.
Step 2: Calculate the amount of wood in one sheet of OSB.
Step 3: Divide Step 1 by Step 2 to determine the number of OSB panels one tree can produce.
Step 4: Determine the number of OSB sheets used in an average-sized single-family house in the U.S.
Step 5: Divide Step 4 by Step 3 to determine how many trees our grass panels will replace.
The answer is approximately 16-17 trees saved per house by using Plantd perennial grass structural panels instead of tree-based OSB for wall sheathing and roof decking.
Read on for how we arrived at this number.
Let's start with Step 1: Volume, Density, and Mass
A. Calculate the volume of harvestable wood in a tree
Fact: Loblolly pine trees average 12 inches wide at breast height with a tapering diameter at the top of the tree.
Assumption: The average tree is 50 feet tall.
Assumption: The average tree cylindrical volume is 8.5 inches in diameter.
Assumption: The average tree llife span is 12.5 years.
Conclusion: The estimated volume of a tree is 34,030 cubic inches. This is equates to approximately 20 cubic feet and .56 cubic meters.
B. Calculate the density and mass of harvestable wood in a tree
Fact: Chapters 5-7 of the USDA Wood Handbook states that freshly cut loblolly pine has roughly 12% moisture content and a specific gravity of .51.
Calculation: Multiplying a .51 specific gravity times 1000 equates to a material density of 510 kg/cubic meter.
Calculation: Multiplying a .51 specific gravity times 1000 times a volume of .56 cubic meters equates to a tree mass of approximately 284 kg, or 626 pounds.
Knockdowns: According to an OSB Life Cycle Analysis from the University of Tennessee, the production process for turning trees into Oriented Strand Board panels is only 75% efficient. 25% of the tree is wasted during the production process. For our math, that equates to 156 pounds of the 626-pound tree.
Conclusion: The usable wood from a single loblolly pine tree weighs 470 pounds.
Step 2: Amount of Wood in an OSB Sheet
Fact: The U.S. Department of Commerce National Institute of Standards and Technology states that the average mass of a sheet of commodity OSB is 1.46 pounds per square foot, of which 1.38 pounds is wood.
Fact: A standard sheet of OSB is 4 feet by 8 feet, which equals 32 square feet.
Calculation: Multiplying 1.38 pounds of wood biomass times 32 square feet per sheet of OSB equals 44 pounds of wood.
Conclusion: The wood in one sheet of OSB weighs about 44 pounds.
Step 3: How Many OSB Panels in a Tree
Calculation: 470 pounds of usable wood in a tree divided by 44 pounds of wood in an OSB sheet equals about 10.7 OSB panels per tree.
Step 4: Number of OSB sheets used in an average-sized single-family house for wall sheathing and roof decking
It's surprisingly challenging to identify a public data source for the average number of sheets used for wall sheathing and roof decking in a typical single-family home. Below is the data we rely upon to contextualize and calculate an answer.
Fact: According to the 2022 Builder Practices Survey conducted by Home Innovation Research Labs and referenced by the National Association of Homebuilders (NAHB), the average single-family home in the U.S. uses over 6800 square feet of OSB.
Fact: Based on data we've received from customers, we know that a 2200 square foot home can use 175 sheets of OSB for wall sheathing and roof decking, which is 5600 square feet of OSB. We will use this data for our final calculation.
Step 5: Number of trees our grass panels replace
Calculation: 175 sheets of OSB per house divided by 10.7 sheets of OSB per tree equals approximately 16-17 trees per house replaced by Plantd's perennial grass structural panels for walls and roofs.
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