Maclay Architects’ Office

Maclay Architects’ Office

Built by Joshua Dartt in the 1850s, the Dartt House and Carriage Barn are located on the Mad River in the historic village center of Waitsfield, Vermont.  In the late 1990s, Bill and Alex Maclay purchased the property for use as Maclay Architects’ architecture office, and the house was left for residential use. The property includes an historic house fronting Main Street and a carriage barn in the rear. The carriage barn was selected for Maclay Architects’ office. Over the past thirteen years, the Maclays have made incremental, strategic energy improvements to the property, and today it is a mixed-use net-zero property that is within walking distance of the town’s shopping districts. This project demonstrates the ability to restore historic structures to net-zero standards, upgrade existing building stock for a mixed-use development, and provide on-site solar that covers the annual energy demands of the 2,500 square foot office in a cold climate. Through the strategic energy improvements that occurred over the span of thirteen years, the completed project minimizes loads by using air source heat pumps, energy recovery ventilation, laptops, and efficient lighting.  This project adds to Vermont’s vibrant, small villages and encourages density, walkability, and engagement with the Mad River. The 19 kW on-site photovoltaic system addresses the challenges of siting PV in historic riverfront properties and provides a creative, elegant solution to meeting the project’s power needs.


Certification Status Net Zero Energy Certified
Version of LBC 3.0
Location Waitsfield, VT, USA
Typology Renovation
Project Area 19,000 SF
Start of Occupancy 1998
Owner Occupied Yes
Occupancy Type Office
Number of Occupants 12


Owner Bill and Alexandra Maclay
Architect Maclay Architects
Contactor Brothers Building
Mechanical Vermont Heating and Ventilation
Electrical Middlesex Electric
Plumbing Lucky's Plumbing
Lighting Design J&M Lighting Design Inc.
Civil McCain Consulting
Landscape Maclay Architects, Cynthia Knauf Landscape Design
Structural Maclay Architects
Interior Design Maclay Architects
Specialty Consultant and Role Energy Balance, Inc. - Energy Consultant
Key Contractors Alteris Renewables, NRG Systems
Photo Courtesy of Willy Osborn Photo Courtesy of Willy Osborn

01. Limits To Growth

This project is an historic renovation of a carriage barn built in the 1850s, located in the village of Waitsfield, Vermont on a riverfront property. Maclay Architects provided and implemented a stream bank stabilization and restoration plan for the site, which optimized solar access and serves as a model for stream bank restoration to support solar energy. This project also promotes wildlife and benefits the ecosystems along the river bank. Site planning included an easement for the Mad River Path, allowing public access along and to the river and linking the village, river front, and valley shopping area to the west.

The 50-foot streambank buffer, restored native vegetation, and public pathway adjacent to the Mad River renders that portion of the lot unbuildable. The project’s solar carport was located set back from Route 100 (Main Street) to minimize the impact on the historic village as well as enable space for a future infill house along Main Street that aligns with the other houses’ fronting.

Photo Courtesy of Maclay Architects Photo Courtesy of Maclay Architects

06. Net Positive Energy

The first step in the process of creating a net zero building is to reduce the loads. In this 1850s building, this provided creative approaches and opportunities. The carriage barn, which was partially renovated by previous owners, was incrementally improved as office space to net-zero-ready standards over thirteen years.  First, in the upstairs, new triple-glazed R-5 fiberglass windows were installed, fiberglass-filled walls were filled with dense-pack cellulose, and loose-fill cellulose was added to the attic.  Three later phases of work included further window upgrades to R-5 units, renovation of walls with composite rigid and cellulose assemblies, improvements to floor insulation, and installation of foundation insulation.  Eventually, the entire building was brought up to the desired R-20 below grade/R-40 walls/R-60 roof/R-5 windows standards.

Additional design features include added windows on the south side of the building to increase passive solar gain and improve daylighting.  Light-guiding blinds improve daylighting in the offices on both levels and reduce glare.  The daylighting, combined with high-efficiency lights throughout, reduces lighting loads.

The office is heated with an air-source heat pump with water distribution. This system replaced the previous gas boiler and allowed for a connection to the existing hydronic heating system with reduced costs. Mini-splits provide air conditioning for the few weeks during the year when it is needed. There are two heat-recovery ventilation systems that provide fresh air to all spaces.

During 2010 and 2011, a 17.55 kW solar carport was added near the rear of the property. The carport and a previously installed 2 kW tracker make the office net zero energy.

This site, located on the Mad River in a historic village, presented multiple challenges in providing renewable power using PV. The historic buildings have no south-facing rooflines, making roof-mounted PV a poor investment.  While there is open land on the property adjacent to the road, there is public objection to solar collectors along scenic roads in general, and particularly so on historic properties.


The adjacent Dartt house has two rental apartments and is also net-zero with an off-site community solar share located half a mile away. It has a single ducted heat pump that supplies heating and cooling to the two apartments. The cost of heating and cooling is included in the rental agreement and is connected to the office utility meter. This enables the owner/landlord to provide two electric meters – one for each apartment – and invoice the tenants for their other utilities based on their actual use. The goal is to incentivize the tenants to minimize energy use with items they control. In order to track the tenant heating/cooling use, an economical kWh counter was installed, and hand recorded readings were made.  Over the last 6 years the heating/cooling average has been 6,500 kWh/season. This amount is subtracted from the office utility bills in order to determine the office energy use. The office also has a kWh reader on the office heat pump circuit as a cost effective way to monitor the heating load for that building.

Photo Courtesy of Maclay Architects Photo Courtesy of Maclay Architects

19. Beauty + Spirit

Beauty emerges from our experiences in life and creating inspiring experiences in our built environment. A New England village acts like a living organism and/or ecosystem generating rich experiences for village residents and visitors. The goal of this project was to demonstrate that historic buildings in historic villages can be made to be net zero energy, thereby maintaining and enhancing the vibrancy and vitality of village life. From a lifestyle as well as a building and community energy perspective this is very important. We must eventually get all buildings to be net zero or net zero ready as well as preserving healthier and less carbon-intensive town settlement patterns.

This project restores historic structures and meets net zero standards. Upgrading existing building stock thereby maintains the beauty of the historic New England village where this project is located. This deep energy net zero retrofit adds to our vibrant small village and encourages density, walkability, and engagement with natural features. The net zero office comfortably sits within the context of Waitsfield Village. The public pathway easement on the property along the river provides a wooded walkway that many locals and visitors use to explore our historic village and river front as well as swim in the river with access across the property.

Other design goals included a model healthy workplace. On the inside of the building, healthy materials were selected include no-VOC paints, formaldehyde-free wheat board, and medite particle board. Cherry harvested from the Maclay’s home property and locally harvested maple are used throughout the building.  Building product samples are artfully arranged in the new entry slab and create patterns of interest. The rich warmth of cherry is used for finely detailed trim and built-ins.

Beauty is enhanced in the interior space by adding windows on the south side of the building. This increases passive solar gain, provides daylight for occupants and increases views to the river and fields beyond.  The new deep windowsills made of local cherry wood enables locations for many indoor potted plants to thrive throughout the year.

Light-guiding blinds improve daylighting in the offices on both levels, and reduce glare at workstations. On the second floor, shades that reduce glare in the workspaces also allow occupants to see outside to the river. Open trusses surprise and delight visitors and provide a partially vaulted ceiling and expansive feel to the upper level.

Photo Courtesy of Maclay Architects Photo Courtesy of Maclay Architects

20. Inspiration + Education

Maclay Architects hosts numerous tours of the building throughout the year. Visitors include contractors, clients, potential clients, students, and community members.  Tours and events have also been organized through the Vermont Businesses for Social Responsibility, Northeast Sustainable Energy Association, Yestermorrow Design/Build School, and Renewable Energy Vermont.

This project is featured as a case study in Bill Maclay and Maclay Architects’ book The New Net Zero: Leading-Edge Design and Construction of Homes and Buildings for a Renewable Energy Future.  Bill Maclay has spoken about this project and the incremental renovation to net zero in an historic building at numerous conferences including Renewable Energy Vermont, Living Future unConference, and NESEA, and has presented the story of the building renovation and addition of solar for the students of the annual Yestermorrow Net Zero Home Design course and University of Vermont students. Maclay Architects continuously showcases the building by hosting client and consultant meetings, and the firm is able to use the building to demonstrate that net zero energy buildings are comfortable, beautiful, healthy, and achievable today and can help support the vitality and energy of villages and village life.

Annual tour information:

In conjunction with Renewable Energy Vermont – Celebrate Solar statewide tours in the summer.

Project Website: