Maine's First Net Positive Passive House - Falmouth, Maine
TideSmart Global is an experiential marketing company in Falmouth, Maine that is committed to investing in the future of its employees, its community, and the sustainability of the natural environment. When it came time to replace a small residential structure on their campus, they wanted a new building that would meet the highest of energy efficiency standards (Passive House) and serve as an example for the building industry in Maine and beyond.
The result is a certified Passive House that generates far more than twice the energy it consumes, making it significantly net positive with zero emissions. This is achieved by dramatically reducing the building’s energy demand and installing copious amounts of renewable energy in the form of a 19.4 kW solar array that occupies the entire roof. This “extra” power is used to power a vehicle charging station (that is free for public use) and to offset power consumed by other existing buildings on TideSmart’s campus.
Viridescent’s design is founded on passive solar design principles, orienting the building and configuring the fenestration to maximize solar heat gain in the winter and minimize it in the summer. It features a highly insulated and tightly-sealed exterior thermal envelope consisting of vapor-open Larsen truss walls (20” thick filled with dense-packed cellulose), a frost protected slab (8” of polished concrete over 10” of EPS insulation), European triple pane tilt turn windows, and detailed connections that are tenaciously sealed and thermally isolated from the exterior. It also features resource efficient, highly durable, low emitting materials, LED lighting, water efficient fixtures, an energy monitoring system.
Being located in a commercial zone, it was also important for this “home” to be flexible enough to be used as an office. It is currently occupied by Tidesmart as an office, but with a few small modifications, it can easily be used as a two bedroom house.
Office / Single-Family Residence
Basis of Performance Claim
Modeled, Zero Energy Program
Conditioned Floor Area
1,388 sq ft
Total Cost of Project
Energy Data Type
Modeled, Zero Energy Program
Renewable Energy System Type(s)
DOE ZERH (Department of Energy Zero Energy Ready Home)
PHIUS + (Certified Passive House with renewables)
Annual renewable energy generated
Envelope and Mechanicals
Frost protected slab comprised of 8" of type 9 RPS rigid foam. A CAD file was sent to Avilite Corp of New Hampshire with the profiles of the frost protected slab insulation/formwork. Once installed, an 8" reinforced concrete slab was poured over a reinforced polyethelene vapor barrier, over the 10" thick EPS insulation. The slab edge is protected behind 8" of EPS. A tapered horizontal bib extends 3'-0" beyond the footprint of the building protecting the sub soils from frost.
Foundation wall assembly
Above grade wall assembly
Vapor-Open Larsen Truss walls: The walls are first constructed as simple 2x4 stud walls with Zip System sheathing. The sheathing becomes both the primary air sealing layer and the vapor control layer (class II vapor retarder). Then 11 7/8” wood I-joists are fastened on the outside vertically and wrapped with a WRB that acts as the building’s secondary air control layer. The I joist cavity is filled with dense-packed cellulose (high recycled content, low embodied energy, low global warming impact, low emittance). Then a ventilation rain screen is installed followed by siding.
Sheathing layers (air sealing and vapor control layers) are on the warm side of the assembly eliminating the risk of condensation and mildew for the life of the building.
Same as windows. Above values are for glazing. Uframe = 0.167