Grantee Research Project Results
Final Report: Carbon Storing Straw Structural Insulated Panel (S-SIP) for Wide Scale Application
EPA Contract Number: 68HERC21C0031Title: Carbon Storing Straw Structural Insulated Panel (S-SIP) for Wide Scale Application
Investigators: Dente, Anthony
Small Business: Verdant Structural Engineers
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2021 through August 31, 2021
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2021) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR)
Description:
Our Team: Verdant Structural Engineers (VSE) performs structural engineering services for clients in the residential and commercial building industry. The company has three principals and twelve full-time employees, and provides structural services that reduce a building’s carbon impacts while maintaining structural integrity and safety. In pursuit of deep green design solutions, VSE regularly engages in research and code development alongside design work.
Our Product: VSE’s Straw-Structural Insulated Panel (S-SIP) is a building wall-system product for applications in the residential and commercial construction sectors. S-SIPs perform the same basic functions as stick frame walls, but are prefabricated with built-in biogenic insulation, and can be manufactured off-site.
The panels accommodate thickness, weight, construction method, cost, performance and code compliance needs. They both remove the carbon footprint of conventional insulative products and finishes, and store carbon—reducing the impact of the building and making the building itself a carbon sink. Over a five-year span, it is projected that the cumulative production of VSE S-SIPs could store 9,257,500 kg of C02, the equivalent of the amount of carbon sequestered by 11,342 acres of U.S. Forest in one year (or alternatively offsetting the equivalent of 3.7 million gallons of gasoline).
Graph 1. Above: Total Cumulative Carbon Storage over projected first 5 years. These are based on the S-SIP’s home growth projection by Fred Rogers (Rogers, Carbon Storing Straw Structural Insulated Panel (SIP) for Wide Scale Commercialization Readiness Assessment Report, 2021). The chart assumes a storage of 7 kg C02 per 4x8 panel and an average of 50 panels per completed home. Over a five-year span, it is projected that the VSE S-SIP could store 9,257,500 kg of C02, the equivalent of the amount of carbon sequestered by 11,342 acres of U.S. Forest in one year (or alternatively offsetting the equivalent of 3.7 million gallons of gasoline)
Summary/Accomplishments (Outputs/Outcomes):
This work was supported by the EPA SBIR Program under contract number 68HERC21C0031. VSE structured its Phase 1 work into the following major categories for the research and design development of the S-SIP:
- Moisture and Permeability
- Fire Codes and Considerations
- Utilities
- Weights
- Environmental Contribution
- Prior Arts: Existing S-SIP Walls
- Insulation and Thermal
- Carbon Offsets
- Supply Chain and Manufacturing
- Structure
These categories were chosen as the main drivers of the S-SIP design because they were the most relevant and wide reaching, and had the most potential to reveal major limitations and/or findings necessary to move the product into eventual wide-scale commercial application.
Here’s a high-level overview of what our team discovered:
- Moisture and Permeability: Straw insulated walls require breathability. Unlike conventional walls, which utilize vapor barriers to keep moisture out, strawbale systems are vapor open, which allows moisture to easily move through the wall. Straw bales are currently in use in residential construction and have been the source for our current codes relating to straw construction. This direct use of straw in bale form has provided the foundation for best practices in utilizing straw in walls. Additionally, our team will focus on material perm ratings and rain screen techniques to take advantage of the natural moisture flow while avoiding potential for rot or decay. The design will also be in compliance with current straw bale building codes in the US.
- Fire Codes and Considerations: The S-SIP product is applicable to low-rise residential and many mid-rise mixed-use construction projects. S-SIPs will be permitted in all circumstances allowing Type-V construction, similar to most conventionally framed wood systems.
- Utilities: VSE’s S-SIP product is intended for exterior walls and therefore will focus on electrical utility. Plumbing lines are assumed to be routed through the interior or to transition to conventional framing in an isolated plumbing region. There are many strategies for routing utilities through prefabricated wall systems. The VSE S-SIP will use horizontal wood battens which separate the interior sheathing and finish, creating a gap between the layers for services to easily route through.
- Weights: Since straw has a heavier density than foam or fiberglass, our S-SIP product weighs approximately 5 lbs/ft2, while conventional SIPS weigh 3.3lbs/ft2. While our S-SIP product is heavier than a conventional SIP, the panels can still be carried around on site by two people and with a reach lift similar to conventional SIPs.
- Environmental Contribution: Straw is the collective term for the stalks of grain. It is primarily composed of atmospheric carbon that has been converted by the process of photosynthesis into a solid form. After straw has been separated from the grain, it is typically used as animal bedding or left to decompose. At this point, the carbon stored in the stalk is re-released into the atmosphere within a year. Conversely, when straw is used as insulation in the walls of a building, it does not decompose, and the carbon which was absorbed by the grain plant is not re-released. This process of storing atmospheric carbon is called negative carbon emissions and complements more common building approaches which attempt to design with materials that emit less carbon from fossil fuel sources. In addition to carbon reductions, these biogenic materials provide a non-toxic and biodegradable option for builders.
- Prior Arts: Existing S-SIP Walls: A handful of domestic and international S-SIP companies exist. This indicates existing consumer and builder exposure to this type of building product. VSE is exploring ways to create an industry association to unite the existing S-SIP companies and similar natural building product manufacturers to build brand awareness and consumer confidence. Because S-SIPs are new to the domestic building industry market, we are confident that we can engage with a significant market share and establish ourselves as a dominant player in the industry.
- Insulation and Thermal: Through material manipulation and implementation techniques, we believe R-values of 3 to 4 per inch are feasible. These values are similar to many conventional insulations and significantly higher than the 1.55 to 1.85 per inch for which most straw buildings are currently credited. We anticipate innovation with this product that will provide insulative capacities not currently available to the domestic straw building industry. With this increase in straw insulative capacit, the VSE S-SIP will be able to supply thinner code-compliant walls than both typical S-SIPs and straw bale systems. At 5 ½” and 7 ¼” thick before finishes, the VSE S-SIP will be equivalent to 2x6 and 2x8 conventionally framed wall construction.
- Carbon Offsets: Aereus Earth is a company that is helping forge a new market for stored carbon (carbon that is not fully sequestered) by providing financial incentive to build with carbon-storing materials through carbon offsets, a depreciable asset that is tied to the structure throughout its lifespan. VSE met with one of the founders and co-owner, Wil Srubar, and discussed how the S-SIP product fits into the Aureus Earth carbon offset requirements. VSE is excited to work with Aureus Earth, as both companies grow to help provide our clients with a great opportunity to offset the cost of switching to a more sustainable product.
- Supply Chain and Manufacturing: Straw is abundant and available throughout the US, and will be utilized for our purposes easily and without disrupting other essential markets. Processes to de-seed, collect, chop, clean, and compress straw as well as assemble custom prefabricated wall panel assembly lines already exist on the market and are available to purchase. Additionally, the prefabrication and standardization will reduce waste, provide easy installation for customers, and be cost competitive with conventional building materials.
- Structure: The S-SIP product maintains structural efficiency and ease of field connection, while minimizing the thermal bridging hurdles of framing members. The ability to blend with conventional framing systems enables easy retrofitting options of existing buildings as well as custom design features. The S-SIP will be fully code compliant with structural testing required by the International Code Council (ICC) and other relevant agencies.
Conclusions:
In addition to the ten topic areas discussed above, VSE identified four major commercialization topics for focus in Phase 1:
- Surveys: Distributed questionnaires to a selected group of our client network of builders, architects, developers, and engineers to better understand their needs. We plan to survey a broader network nationwide as well as homeowners in the next round. Results validated the value propositions associated with the product and confirmed that the early adopter market is eager to work with this product.
- Board of Advisors: Compiled a list of architectural, building science, and business industry experts who are potential advisor candidates for the S-SIP product.
- Legal/Intellectual Property: Found and cataloged active patents in the modular wall systems arena. Most are international patents or patents that pertain to different technology.
- Price Point: Determined competitor pricing to help establish ideal S-SIP market-entry price point.
All of our Phase 1 results, including the four topics mentioned above, show us that the S-SIP product is ready to move into the prototyping phase of development. Throughout the next steps of development, our team will continue to be on the cutting edge of building science to ensure that the product can be fully commercialized over the course of the next two years. We are confident that a thin panel that is cost competitive and replaces toxic materials with carbon storing non-toxic agricultural byproducts will be a huge boon to the building industry and lead to eventual widespread adoption of this easy-to-use product nationwide.
VSE’s S-SIP product is a critical solution to combat the climate crisis. The building industry accounts for 39% of global CO2 emissions with 11% of these emissions resulting from sourcing, manufacturing, and implementation of materials. Right now, many industry solutions propose to use less of the same construction materials—a solution that will not result in the kind of long-term impact necessary to significantly lessen emissions. And while deep green building solutions exist, they are on-site labor intensive and custom (expensive), therefore unappealing to the mass market.
If we are going to reach global climate initiatives and mandates (SE2050, Architecture 2030 and others), new products must enter the market quickly. Our S-SIP product uses agricultural byproducts (rice, wheat, and barley straw), cutting edge building science, and structural design to store carbon as insulation for the lifespan of the building—resulting in net negative carbon emissions and going well beyond simply reducing a building’s carbon footprint.
SBIR Phase II:
Carbon Storing Straw Structural Insulated Panel (S-SIP) for Wide-Scale Application | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.