Case Study: Concrete Soffit Insulation

The Box Project | Plymouth

Concrete Soffit Insulation Overview

The Box Project is a major new museum, art gallery and archive for Plymouth and the South West. Find out how ThermoFoam delivered a concrete soffit insulation project for Willmott Dixon.

ThermoFoam were delighted to be appointed by the main contractor, Willmott Dixon, to install concrete soffit insulation to the archives floor during the construction of The Box Project in Plymouth. The opening of The Box Project was one of the most significant cultural events in the UK in 2020. Plymouth’s former Museum and Art Gallery, Central Library and St Luke’s church buildings have been completely transformed with new galleries and exhibition spaces. The Box Project also features a striking elevated ‘archive in the sky’ with research and learning facilities, food, drink and retail spaces. It has also created a principal new public square for performances, events, and artistic responses.


Wilmott Dixon



Project Type

New Build Development

Product Used

Nexseal 2.0 LE

Install Date

October 2018

Install Size


Install Duration

3 Days

The Project

Concrete Soffit Insulation Brief

The main contractor, Wilmott Dixon, was appointed to deliver the construction work for this £46 Million project. With a 700m2 external soffit to insulate, the Wilmott Dixon team needed a solution that was quick to install and compliant with modern building regulations. Keen to see what spray foam insulation could do for the project, the team contacted ThermoFoam for our expert advice and specifications. Our brief was to install a compliant solution using eco-friendly products, installed rapidly without any mess or impact on the surrounding building whilst adhering to strict site health and safety regulations. The archive room at The Box Project contains a wide range of historical artefacts, and our brief was to provide an airtight thermal solution that could help to manage the environmental conditions to preserve these valuable assets.

Concrete Soffit Insulation Solution

Nexseal High Lift closed cell foam was the order of the day for this project. It’s high tensile strength and ability to bond to the concrete soffit substrate makes it the perfect antidote for the building envelope. Combine the exceptional thermal performance and the speed of install thanks to the low exothermic properties, the entire 787m2 surface was fully insulated to airtight standards within 3 days. The Box Project had the environment in mind when selecting construction materials and Nexseal LE helped score points towards this low carbon construction thanks to its low global warming potential and HFO Blowing Agent. Even though the project required working at height from a scissor lift, the versatility of spray foam insulation helps to make for an easier and safer application.

Concrete Soffit Insulation Warranty

Nexseal Closed Cell spray foam offers such a strong cohesive bond to the surface onto which it is applied and it will not shrink, diminish or reduce in performance over time. We offer a 25-year product guarantee with an expected product life well above this timescale. When applied by a ThermoFoam-approved contractor, a 25-year installation warranty is also applicable. Find out more about some of the other projects that the main contractor, Willmott Dixon, undertakes throughout the UK here:

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