Wood Fiber Modular Retrofit System
Residential energy use accounts for 20 percent of energy-related CO₂e (Carbon Dioxide equivalent) emissions in the U.S., more than 1 billion metric tons annually, an amount comparable to the total emissions of Brazil, and exceeding those of Germany. Addressing the climate crisis requires that we significantly reduce the carbon footprint of the residential buildings we design and construct.
But new buildings represent only the tip of the iceberg. The 1.35 million housing units built in the U.S. each year join an existing stock of more than 139 million houses and apartments, 38 percent of which were built before 1970. The benefits to be realized by reducing the carbon footprint of these buildings–most of which are poorly insulated or uninsulated–are enormous. Upgrading the wall and attic insulation in existing residential buildings alone would reduce CO₂e emissions by 575 million metric tons annually, cutting housing’s share of total U.S. emissions in half.
President Biden has recognized the importance of seizing this opportunity, proposing a clean energy plan that would cut the carbon footprint of America’s buildings in half by 2035, in part by investing $10 billion in residential energy efficiency upgrades.
To make good on the promise of the Biden plan, the construction industry will need scalable, cost-effective renovation solutions that reduce energy consumption and carbon emissions. Any truly practical system must work with a broad range of building types, minimize disruption to occupants’ lives, and–crucially–employ materials with a negative carbon footprint, so that we don’t make the problem worse before we make it better.
OPAL and Timber HP developed the Wood Fiber Modular Retrofit System as a flexible, cost-effective, carbon-sequestering system for improving the energy efficiency of existing wood frame buildings to net-zero levels while also securing their long-term durability, upgrading their aesthetics, and dramatically improving indoor air quality and occupant comfort. Employing factory-fabricated component assemblies, readily available residential mechanical equipment, and conventional building trades, Wood Fiber Modular Encapsulation accomplishes these crucial goals almost entirely from the outside of the building—with minimal disturbance to the structure, site, and occupants—and in compliance with local building codes.
The core of the system is a highly adaptable kit of standardized parts:
- Pre-cut exterior-insulation modules incorporating Timber HP’s renewable, carbon-sequestering wood fiber insulation
- Prefabricated window modules incorporating high-performance triple-glazed windows, that can be installed from outside the building
- Off-the-shelf heat pumps for heating and cooling
- A centralized HRV system
- A roof-mounted photovoltaic array sized to offset all of the building’s energy requirements for heating, cooling, and plug loads
Combined with standard-practice blown insulation of the existing exterior wall and first-floor cavities with wood fiber insulation, these components yield a super-insulated, air-sealed, optimally ventilated building shell while preserving the building’s structure and interior finishes. Wood Fiber Retrofit System is readily adaptable to a wide range of building configurations and styles and is cost-effective at scales ranging from a single building to an entire neighborhood. Most importantly, because it employs carbon-storing wood fiber insulation and other wood-based construction materials, the system delivers climate benefits from day one, without the lengthy carbon-debt payback period that conventional materials entail.
The potential positive impact is huge. The National Renewable Energy Laboratory estimates that upgrading all U.S. housing in this way would reduce residential CO₂e emissions by 291 million metric tons annually, or more than 4 percent of total U.S. emissions.
But the choice of insulating material is crucial. Renovating 1 percent of existing U.S. housing stock per year to net-zero energy performance would avoid 98 million tons of operational CO₂e emissions over 10 years. If the work were done with conventional materials (loose-fill fiberglass, spray foam, and EPS boards), however, those operational savings would take 9 years to offset the CO₂ embodied in the insulation alone.
Using wood fiber instead yields a dramatically better outcome. In the project illustrated here, wood fiber insulation and other wood components sequester 16,271 kgCO₂e for the life of the building. This carbon surplus more than offsets the carbon debt of other materials used in the project, yielding a net global warming potential (GWP) of -7,277 kgCO₂e. As a result, all of the operational savings the project achieves begin to accrue immediately as a measurable reduction in carbon emissions.