Gryphon Doors – keep your home warm and tight with mycelium
Gryphon Door in Charlotte, VT. Photo: Ben Graham
By Ben Graham
At the beginning of the last energy efficiency revolution that brought about Passive House, Living Building Challenge, Net Zero and Vermont High Performance Homes, it was widely reported that windows and doors accounted for around one-third of the loss of heat to most homes. Talk about low hanging fruit! Most builders began to learn about making building enclosures tighter and more insulating that included working out better details around places that are typically thermal breaks in the insulation layer such as window and door frames.
There was this issue though that it apparently takes a long time for large industries like window and door companies to respond to this shift in design. So builders who were looking for more insulating window and door products had a hard time sourcing good standardized products and often started looking overseas where they are typically ahead of our curve.
Seeing this opportunity, a small door company was formed to fill this demand specifically for the good old traditional wood door that was designed for the fossil-fuel free, carbon sequestering future.
I want to be clear, while the inspiration for Gryphon Doors is based on the beautiful wood doors we have grown up with, and that develop so much character as they age with the ones they protect, this is not your grandparents’ wood door.
Cutaway of Gryphon Door with standard 3-1/2 in. thickness showing 2 inches of Mycofoam (R7.2) and double gaskets. Photo: Ben Graham
First of all, the standard Gryphon Door is three and a half inches thick. This reflects the shift to more insulation. With all that insulation the structure of the door has changed from a slab of not so insulating material – wood, to a sandwich design with the soft stuff on the inside. As you can imagine, these doors are a bit more substantial and require four solid hinges instead of the typical three.
The insulation used in Gryphon Doors is very important to the overall design, and distinguishes it from all other doors in the market. Not only does it use a lot more of it but it is a natural material that can be grown anywhere and does not require mining, drilling or energy intensive refining. The first insulation material used in the door core was a revolutionary type of material developed by Ecovative Design from the Albany, NY area that involves mycelium. Mycelium-as in “the mass of branched, tubular filaments (hyphae) of fungi”- is grown in agricultural fiber based medium, such as hemp hurd, in a process developed to maximize the qualities for a stable, durable and insulative building panel. They began producing prototypes at their facility to be used in standard construction, and Gryphon Doors was able to support that process and incorporate some of the first Mycofoam panels into its doors. The Mycofoam panels are made by inoculating the hemp hurd with the fungus and storing that in a warm, wet place to grow. The mixture is then broken up and allowed to continue growing a second time to make the root system even stronger. The end of the process includes desiccating the panels to effectively kill the mycelium. The initial testing (ASTM C518) on the Mycofoam panels produced a thermal conductivity value of 0.039 W/mK = R 3.7 which is about as good as we have seen with agricultural fibers. Other testing showed that moisture levels remained stable with environmental fluctuations and tended to balance out at around 12%, and the water vapor permeation (dry cup) at 30, which we like, because it indicated that we will not be trapping moisture in our wood doors.
Two inches of sheep’s wool (R8.6) fills the door core. Photo: Jon Deerfield
Gryphon Doors has also begun using sheep’s wool-another agricultural type of fiber- as insulation. Sheep’s wool is advantageous because of its high insulation value R 4.3(@1.13lbs/cf) as well as its resistance to water and fire, and its durability over time to stay in shape. Sheep’s wool is also very light and complements the heavy wood structure.
The other big difference is how the door closes in order to make not only a tight seal, but one that will last over the lifetime of the door. Again, this issue has been mostly solved with the advent of multipoint hardware and durable gaskets developed in Europe for patio door locks. A good air-sealing multipoint lock utilizes cam rollers to effectively pull the door tight against the seals to not only keep warm air from escaping but also to keep the wood structure in alignment with the seals and from sagging over time on its hinges.
These improvements to the classic wood entry door have brought it into the new millennium without losing the look or feel everyone is accustomed to. In fact, the heft of the 3 ½” insulated door has actually improved the feeling of security and protection you get from using it. This is the explanation of the name: the mythical creature, the Gryphon, who is seen as a protector.
The Northeast now has a supplier of these insulated wood doors that are a perfect fit for our energy-efficient, fossil-fuel-free future.
Ben Graham is a managing partner of New Frameworks Natural Design/Build. Contact Ben at 802-793-8189. Read more at https://www.newframeworks.com/techniques/#doors-section.
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