Project Overview 
Thornton Creek Commons is a one-of-a-kind, Built Green 5-Star Certified fenced pocket neighborhood in North Seattle, containing nine single family homes and a built-in 1.5-acre natural area which includes the creek, mature trees, a fire pit, fenced off-leash dog park, and meditation garden. Another benefit of this development is its walkability to retail, restaurants, bus and light rail public transportation, and other amenities. The homes and garages are stick-built, which enables high, vaulted ceilings and the feeling of openness and space.

One way these homes shine is in the success of The Cottage Company’s efforts to salvage materials that were already on-site and incorporate them into each light and bright, intentionally designed home. The previous building on the land, St. George Episcopal Church, was painstakingly deconstructed so that many of the materials could be re-used in the creation of the new cottages. 

Materials Reuse

These homes are unique for the amount of material re-used from the old Episcopal church deconstruction, including most of the wood flooring. The church structure contained a great deal of “car decking” – a heavy, wide and thick double tongue and groove fir decking material. Harvested locally about 75 years ago, this wood is generally higher quality than the lumber available today because the trees in the old forests had to compete for limited sun and water, resulting in slower growth and denser, harder wood.

The car decking was milled into 6000 square feet of ¾ inch fir tongue and groove flooring which was not quite enough to finish all the homes. The Cottage Company supplemented the recovered flooring with Douglas fir from Sustainable Lumber Company of Missoula which offers reclaimed fallen timber from the high Montana forests. With the highest strength to weight ratio of any wood species, Douglas fir is renowned for durability, strength, and natural beauty. The floors are finished with hand rubbed penetrating oil and multiple layers of low VOC water-based catalyzed protective topcoat

Energy Performance

Achieving Built Green 5-Star certification required pre-planning and collaboration with the project’s third-party verifier to get the energy model dialed in and ensure maximized energy performance. Energy Recovery Ventilator (ERV) systems and a tight building envelope were key components of that performance. Sealing was tested and re-tested until the desired rates were achieved using Aero Barrier, an aerosol sealant that is forced by air pressure generated by the blower door into gaps and cracks as fine as a human hair or as large as ½ inch. The pressure carries a non-toxic, water-based formula throughout the home and effectively seals any leak by using the very air that is leaking out of the home, thereby finding even invisible leak points. The building code required an air exchange score of three or less, and the Thornton Creek Commons homes achieved a score of less than one, demonstrating significantly lower energy consumption, lower heating/cooling costs, quieter homes, and less opportunity for water intrusion.

Interior Sound Minimization

As Thornton Creek Commons is in an urban area with the ambient noise that comes along with that, measures were taken to maintain quiet inside the homes. An acoustic drywall with two layers of gypsum wallboard separated by an interior layer of acoustic caulk – specifically developed to prevent sound energy from entering a home – was installed. Floors and ceilings were insulated using rockwool to prevent sound energy from entering, or to absorb sound if already present.

To avoid sound coming into the house via the studs and attached wallboard, the builder used a double row of studs, to reduce the potential transfer of sound energy into the drywall. A traditional wall would have the drywall attached directly to studs on both sides of the wall, which would readily transfer sound, much like a drum. The Cottage Company insulated between the studs as well as floor/ceiling, to absorb sound that would otherwise easily pass through the air pockets between. They used soft, pliable materials that absorb sound; such as fiberglass, rock wool batts, or blown in cellulose to fill the cavities. This reduces the sound level an additional five to eight decibels.

Insulation

The insulation strategy (for homes built on a slab on grade foundation) at Thornton Creek Commons begins with a double layer of rigid foam insulation under the concrete slab and at the edges of the stem walls to avoid thermal bridging. This is twice the under-slab insulation required by code – four inches versus two inches – and helps keep the slab near room temperature. Houses on a crawl space foundation are insulated with fiberglass batts to a value of R38. Exterior walls on the north side are insulated with the Blown in Blanket System (BIBS) to the full depth of the 2x6 studs.

Stormwater

Stormwater runoff from the roof of each building is collected through rain gutters and downspouts and directed into footing drains at each structure. The runoff is then piped to a large underground detention vault which acts as a buffer to temporarily hold stormwater runoff until it can be released into the city drains at a manageable rate, so the city’s system won’t be overwhelmed in the case of a severed storm.

Land Conservation

While the land needed a lot of remediation work to remove invasive vegetation, a large portion of the property stayed undeveloped and is open grounds for the residents. The green space park has been declared an environmentally critical area and can never be developed. It will be preserved as a private park for the nine Thornton Creek Commons homeowners, FOREVER.

Homeowner’s Manual and Property Guide

The Cottage Company provides each homeowner an easy-to-read manual with “concise, focused descriptions of the homes’ systems, operations, controls, and important maintenance actions.” This document ensures residents have the information they need to keep their home at its most comfortable and efficient.

In addition, homeowners are given a property guide which provides the history of the land, the building process, and the vendors and contractors who contributed over the course of the build. The time and care put into this guide make it an interesting read, and a unique offering of The Cottage Company.