Cornerspring
Montessori

Middle School Building Annex

Case Study  ·  Institutional / Educational  ·  CLT Prefab  ·  High-Performance

A High-performance CLT school assembled in three days

Cornerspring Montessori School had a clear goal: extend Montessori education to middle school-age students in the midcoast Maine community. What they needed was a building that could match that ambition — high-performance, sustainable, and completed without disrupting the existing school campus.

The result is a freestanding 1,000-square-foot building fabricated offsite at the NotchSB facility in Madison, Maine and assembled on Cornerspring's 35-acre Belfast campus in just 3 days. Structural panels arrived by truck and were craned into place by NotchSB's in-house installation crew — a construction timeline that would be impossible with conventional stick-frame methods.

Four children studying at two black-topped tables in a Montessori classroom with CLT wooden walls, large triple-pane window showing the outdoors, and microscopes on the tables.

Project Data

Client Cornerspring Montessori School
Location Belfast, Maine
Design Team OPAL Architecture
Builder / Fabricator NotchSB
Year Delivered 2021
Size 1,000 square feet
3 Days to install
50+ Building envelope sensors
All Wood
Construction

The NotchSB prefab panel system: structure, insulation, and finish in one assembly

The building employs the NotchSB all-wood prefabricated panel system — a construction approach that combines cross-laminated timber and wood fiber insulation in a single integrated assembly. Each panel provides structure, thermal insulation, and interior finish simultaneously, eliminating the layered coordination complexity of conventional construction.

Wood fiber insulation, such as TimberBoard from TimberHP, delivers high thermal performance and vapor management alongside the CLT structure. The result is a building envelope that outperforms stick-frame construction on airtightness, thermal bridging, and embodied carbon, while reducing total on-site construction time, site disturbance, and project carbon footprint.

Panel System

CLT structure + wood fiber insulation combined in prefabricated all-wood panels. Each panel delivers structure, thermal envelope, and interior finish in a single integrated assembly — eliminating the layered coordination of conventional construction.

Insulation Rigid Wood Fiber Insulation
Roof: R70
Wall: R40
Fabrication Offsite at NotchSB facility
Shell Installation Three-day onsite assembly
Biogenic Carbon Stored
(in CLT & Insulation)		 57.8 metric tons CO₂e stored
(approx. 12 passenger vehicles' annual emissions)
Biogenic Carbon Stored
(in CLT & Insulation)		 57.8 metric tons CO₂e stored
(approx. 12 passenger vehicles' annual emissions)

The Carbon Advantage

Loreum Ipsum

Carbon Advantage

Mass timber sequesters biogenic carbon. Wood fiber insulation adds further embodied carbon savings. Together they produce a building envelope with a significantly lower carbon footprint than steel or concrete alternatives.

From design spec to verified performance:

The Data Behind the Build

In partnership with building science researchers at the University of Maine, NotchSB instrumented the Cornerspring building envelope with more than 50 sensors tracking moisture and temperature performance through real Maine seasons.

The result: a long-term, real-world performance record that confirms the assembly performs as designed — turning engineering assumptions into verified data, and giving architects and developers a credible evidence base for evaluating mass timber construction.

The Results: High Performance, Low Risk. Learn more about our findings here [blog post].

50+ Building envelope sensors
A cozy Montessori wooden CLT classroom with large triple-pane windows, two children reading, a girl pointing at a map, a guitar on the floor, and various books and toys scattered around.
Modern CLT Montessori school building with wooden accents and large windows in a snowy landscape, with three people walking nearby.
A modern CLT Montessori wooden school building with a sloped roof, set in snowy landscape with a forest in the background, and a group of people walking nearby.
Four children in a classroom, two sitting at a desk on the left and two at a desk on the right with microscopes, facing a large window showing a snowy landscape outside.
A construction site shows a crane lifting a prefabricated roof panel to the top of a wooden CLT structure under construction.
Interior of a CLT house or classroom under construction with wooden walls and ceiling, temporary supports, a ladder, and construction tools.
Construction site with prefabricated wooden CLT panels being installed on site, with scaffolding, bright blue sky in the background.
Wooden CLT wall framing of a building under construction, with a window opening and a partial roof overhang, against a blue sky.
Construction worker sitting on a wooden CLT panel at a construction site, wearing a safety helmet and vest, using a mobile device, with a crane lifting a large structure against a clear blue sky.
A construction crane lifting a large pre-fabricated wooden CLT panel onto a building under construction in a grassy area with trees in the background.
Partial view of a building under construction with wooden CLT wall panels and wood fiber insulation on the right, blue sky, and green trees in the background.
Construction workers building a CLT wooden wall with wood fiber insulation on a construction site outdoors, with tree-lined background and blue sky.
Construction workers assembling a pre-fabricated CLT wooden structure outdoors, with a crane lifting a beam overhead, and ladders and tools around.
A flatbed trailer carrying pre-fabricated CLT roof and wall panels, lumber and construction materials parked on a road. A large crane is lifting a section of a building under construction, with several workers nearby.
materials on a flatbed truck including pre-fabricated CLT roof and wall panels with window openings and wooden frames
Inside a manufacturing or construction warehouse with workers and equipment. A crane lifts large CLT pre-fabricated panels while workers guide and position them. The area features metal beams, workbenches, and construction materials.