By Jeremy Shannon

What does it take to build a treehouse? Well, that depends on whether it's a typical backyard kids' treehouse or an all-season retreat designed using Passive House techniques and capable of accommodating up to eight people. Add to these considerations the requirement that the treehouse had to be all-electric and the project specifications for what became Little Birds Treehouse quickly outpaced those of your average tree structure. 

When our family moved out of New York City in 2016 and built our Passive House farmhouse on a 120-acre property near Port Jervis, NY, I promised my wife I’d build a treehouse for our kids as soon as I finished the main house. Fast forward seven years, and although we've been living in our house for six of those years, the exterior stone façade and some finishing touches remain incomplete. With our kids growing older and one heading off to college soon, the urgency to fulfill my treehouse promise grew. Thus, I was convinced to finally make good on it.

As an architect with a bit of a whimsical streak, my mind quickly conjured up a fantastic, multi-level design reminiscent of the Swiss Family Robinson’s. Using Sketchup, I transformed this vision into a treehouse I could build, although it would require five trees to support it. I even had the perfect place for it, just beyond the wood line next to our back fields. The chosen site was sheltered from view but still accessible—approximately 700 feet from our house and driveway.

However, I soon realized that what I had envisioned was far grander and more expensive than what I could justify for our kids' enjoyment alone, and indeed would be an experience that ought to be shared with short-term paying guests. After all, what better way could there be to introduce vacationers to the many benefits of Passive House, and to the flexibility of this approach, than with a whimsical treehouse.

Key to the Little Birds Treehouse design was ensuring year-round comfort for guests, which we achieved by using Passive House techniques to both maximize comfort and minimize energy consumption. We opted for an all-electric design powered by our solar photovoltaic house energy supply. While on-site solar wasn't feasible due to the treehouse's location in the woods, we plan to expand our home’s solar array to cover the additional load.

High-performance features of the treehouse include 9 inches of hemp and mineral wool insulation in the floor, walls, and roof, creating a continuous thermal barrier. The insulation is complemented by an Intello Plus membrane air barrier, sealed with Pro Clima tapes, provided by 475.Supply. Interior and exterior rough sawn wood adds further insulation, resulting in an overall R-38 wrapping the treehouse.

Though we couldn't justify triple-glazed windows, we installed aluminum-clad wood windows filled with argon, boasting a U-Value of 0.28—better than code and avoiding UPVC for environmental reasons. A Lunos ERV system, perfect for the 12-foot x 12-foot spaces, provides 24-hour fresh air while recovering more than 80% of the energy from outgoing air. Heating needs are met by small wall-hung electric radiators, with guests reporting sufficient warmth even in temperatures below 10°F. Hot water for the outdoor shower and indoor kitchen faucet comes from separate 2.5-gallon instant electric water heaters, reducing energy consumption and peak electrical usage.

The treehouse design includes deep porches and overhangs, reducing the need for cooling. Ceiling fans and operable windows provide a refreshing cross breeze, keeping guests comfortable in summer without additional energy demands.

While discussing embodied carbon may seem trivial for a whimsical structure like this treehouse, my hope is that it sparks conversations about using high-performance passive measures in necessary buildings. By employing locally milled, rough-sawn wood, on-site pine trees for railings, hemp insulation, and wood finishes without polymer coatings, the treehouse showcases thoughtful, sustainable design. The surprise of our fall and winter guests at how a small wall-mounted electric radiator can keep the entire building warm near 0°F makes me hope the ecological impact of building our fantastical treehouse is justified, as it seeks to educate others beyond the Passive House community.

Architect Jeremy Shannon is a longtime Passive House enthusiast and Director of Climate Action at Gensler. Stays at the Little Birds Treehouse can be booked here.