Saturday, April 25 | 11 am – 5:00 pm
IN PERSON!
Location: Ballard
Site Description
FEATURES: Advanced Building Envelope, DADU or ADU, Design Innovation, Energy Efficient, Energy Star Appliances, Indoor Air Quality, New Construction, Small Square Footage
Abode Builders and Sandpoint Studios are proud to present the Cottage on 28th, a sustainably built accessory dwelling unit on the western edge of Ballard. This compact home reflects a shared commitment to high-performance construction, thoughtful design, and long-term environmental responsibility.
Designed and built as a low-energy, high-comfort home, the Cottage integrates advanced building science with durable, low-impact materials. The result is a healthy indoor environment, reduced operational energy use, and a building designed to perform for decades.
Key Sustainable Features
All-Electric Heating + Hot Water
A Sanden SANCO₂ heat pump provides both domestic hot water and hydronic radiant floor heating. Using CO₂ as a natural refrigerant, the system delivers exceptional efficiency—up to four times that of conventional electric water heaters—while minimizing global warming impact. The system’s high output and durability support both performance and longevity.
High-Performance Windows
Aluprof MB-79 triple-pane windows and doors meet PHIUS performance standards, with a U-factor of 0.14—significantly exceeding code requirements. These assemblies enhance thermal comfort, reduce energy demand, and contribute to a quiet interior environment. The windows were placed to both satisfy life safety requirements, passive ventilation and advanced daylighting.
Balanced Ventilation
A Broan AI Series heat recovery ventilator (HRV) delivers continuous, balanced fresh air while recovering heat from exhaust air. This is essential in an airtight home, maintaining indoor air quality without sacrificing efficiency.
Efficient Heating + Cooling
A Mitsubishi ductless mini-split heat pump provides supplemental heating and cooling, allowing for precise, zone-based comfort with minimal energy use.
High-Performance Building Envelope
The enclosure is designed to manage air, water, and thermal flow with precision:
Pro Clima Mento WRB with fully taped seams for airtightness
2″ STEICO wood fiber insulation for thermal performance, moisture buffering, and carbon sequestration
A 1-1/2″ rainscreen assembly to promote drainage and drying behind the cedar siding
The result is a durable, vapor-open wall system that supports both building longevity and occupant health.
Unvented Roof Assembly
A fully sealed, unvented roof was used to accommodate the home’s shed roof design and vaulted ceilings. Careful air sealing minimizes heat loss and moisture risk, improving overall energy performance.
Low-Impact Insulation
Knauf EcoBatt insulation—formaldehyde-free, GREENGUARD Gold certified, and made with high recycled content—was used throughout the walls and roof assembly.
Airtight Construction
Following the principle “seal it tight and vent it right,” the home is carefully air sealed using tapes, sealants, and targeted spray foam. The project is targeting near Passive House levels of airtightness (<0.8 ACH50), significantly reducing energy loss.
Energy-Efficient Skylights
CrystaLite ES skylights were selected for their advanced thermal performance and thoughtful design. These PVC-free, quad-pane units achieve a U-factor of 0.29 and are engineered to reduce heat loss at the curb—an often overlooked weakness in conventional skylights. Carefully positioned to reflect daylight deeper into the interior, they significantly reduce the need for artificial lighting during daytime hours while enhancing overall comfort and energy efficiency.
Durable, Low-Carbon Materials
Locally sourced cedar siding from responsibly managed forests
FSC-certified wood flooring installed with 0-VOC, GREENGUARD-certified adhesive
LED lighting throughout for reduced energy consumption and long-term efficiency
Efficient Appliances
Miele heat pump dryer reduces energy use by up to 70% and eliminates the need for exterior venting
Miele high-efficiency washer minimizes water and detergent use through smart load sensing and dosing
FSC Certified Flooring
The flooring consists of FSC Certified engineered hardwood, which was secured to the concrete slab using Bona Quantum adhesive. This adhesive is notable for its 0-VOC formulation and GreenGuard certification.
Abode Builders and Sandpoint Studios are both proud members of the Northwest EcoBuilding Guild, an organization dedicated to advancing healthy, energy-efficient, and resource-conscious building practices.
We’re grateful to the skilled craftspeople and collaborators who helped bring this project to life, and we’re honored to share it as part of the 2026 Green Home Tour.
