A Sustainable Revolution in Museum Preservation
How a simple mixture of hemp, lime, and water is redefining the environmental future of museums
Imagine a storage facility that actively helps preserve priceless historical artifacts, not with energy-guzzling machines, but through the very walls it is made of. This is the reality for the Science Museum Group in the UK, which pioneered the use of hempcrete, an innovative bio-material, to construct a new collections store 4 8 .
Confronting the dual challenges of reducing carbon emissions and ensuring optimal preservation conditions, the museum turned to a material that is as ancient as it is futuristic. This case study explores how a simple mixture of hemp, lime, and water is revolutionizing sustainable construction and redefining the environmental future of museums, one breathable wall at a time.
The Science Museum Group's hempcrete store demonstrates that the most advanced solution for preserving our past can be found in natural, low-tech materials.
Hempcrete, also known as hemplime, is a bio-composite building material made from the inner woody core of the industrial hemp plant (called the "shiv" or "hurd") mixed with a lime-based binder and water 4 8 . Unlike traditional concrete, it is not used for load-bearing structures but serves as an insulating infill for walls, roofs, and floors 1 8 .
Its key lies in its porous structure, which grants it a unique set of properties essential for both sustainable construction and delicate preservation environments.
Hempcrete stores more carbon than is emitted during its production, making it a carbon sink that actively fights climate change.
The Science Museum Group's storage site at Wroughton faced a significant dilemma. Its existing hangars were uninsulated, damp, and environmentally unstable, with relative humidity (RH) levels fluctuating between 65–100%, mirroring the external conditions 2 . These conditions are hazardous to delicate historical objects.
The traditional solution would involve energy-intensive heating, ventilation, and air conditioning (HVAC) systems, which conflict with sustainability goals and are costly to run 2 . The museum needed a low-energy, passive solution to provide stable, protective storage.
Research suggested that using construction materials with high moisture absorption capability could significantly enhance the stability of indoor temperature and RH 2 . The hypothesis was that a building made from hygroscopic hempcrete could passively buffer humidity fluctuations, reducing reliance on mechanical systems and creating a superior preservation environment.
The project served as a live experiment, with its performance monitored as part of a PhD project. The methodology can be broken down into several key stages:
The primary building material chosen was hemp-lime concrete (hempcrete). Its excellent sustainable credentials and significant hygroscopic capability were the central factors 2 .
The hempcrete was likely mixed on-site and cast into temporary formwork around the structural frame—a method known as cast-in-place 4 . After an initial set, the formwork was removed.
The design paired the passive buffering of the hempcrete with a small, complementary air-handling system to ensure environmental control could be maintained with minimal energy input 2 .
Unstable environmental conditions in existing storage facilities threatened artifact preservation.
Study of hygroscopic materials suggested hempcrete could provide passive humidity control.
Development of hybrid system combining hempcrete walls with minimal mechanical systems.
Building of the hempcrete store using cast-in-place methods with timber structural frame.
Continuous assessment of environmental conditions to validate performance.
The hempcrete store performed as anticipated. Despite some initial construction challenges and mechanical system malfunctions, the building successfully demonstrated its core premise 2 .
The hempcrete walls provided excellent thermal insulation and, crucially, used their hygroscopic properties to buffer fluctuations in relative humidity. By absorbing excess moisture when humidity was high and releasing it when the air was dry, the building itself helped maintain a stable environment.
This passive regulation drastically reduced the energy required by the mechanical systems to achieve the strict RH levels necessary for preserving the museum's diverse collections, which include everything from large industrial machinery to fine art and archival materials 2 .
This case study proved that a hybrid approach—combining the passive, dynamic buffering of natural materials with minimal mechanical systems—could achieve preservation-grade environmental control sustainably.
The hempcrete store successfully maintained stable preservation conditions while significantly reducing energy consumption compared to traditional HVAC solutions.
To understand why the museum store performed so well, it helps to examine the scientific data behind hempcrete's properties.
| Property | Typical Range | Significance |
|---|---|---|
| Density 6 8 | 200 - 600 kg/m³ | A lightweight material, reducing structural loads. |
| Total Porosity 6 8 | 70% - 85% | High porosity is the source of its insulating and moisture-buffering abilities. |
| Thermal Conductivity 6 8 | 0.06 - 0.14 W/(m·K) | Indicates strong insulation performance (lower values are better). |
| Specific Heat Capacity 8 | 1000 - 1700 J/(kg·K) | High heat storage capacity contributes to thermal mass, stabilizing temperatures. |
| Vapor Permeability 8 | High | Allows water vapor to pass through, making the wall assembly "breathable". |
| Metric | Value | Explanation |
|---|---|---|
| Moisture Buffering Value (MBV) | 2 - 4.3 g/(m²·%RH) 8 | Classifies hempcrete as an "excellent" moisture regulator. It can absorb and release significant moisture to moderate indoor humidity swings. |
This data from a North American study highlights hempcrete's primary environmental advantage. The values represent the global warming potential (in kg of COâ‚‚ equivalent) to produce enough material for an R-10 wall assembly.
| Material | Embodied Carbon (kgCO₂e/m²) |
|---|---|
| Hempcrete 3 | -11 to -17 |
| Hemp Fiber Batt 3 | -0.25 to -1 |
| Fiberglass Batt 3 | 1.2 |
| Polyisocyanurate Foam 3 | 7.2 |
| Extruded Polystyrene (XPS) 3 | 8.6 |
Passive regulation reduces mechanical system dependency
Actively removes COâ‚‚ from the atmosphere
Prevents moisture accumulation and mold growth
Cannot be used as a load-bearing material
Understanding hempcrete requires familiarity with its simple yet precise recipe. The following table details the essential "research reagents" used to create this innovative material.
| Component | Function | Key Details |
|---|---|---|
| Hemp Shiv (Hurd) | The plant-based aggregate that provides the porous structure. | The woody inner core of the hemp stalk 4 8 . Its porosity is responsible for insulation and moisture buffering. |
| Lime-Based Binder | The matrix that binds the hemp shiv and gives the wall its cohesion. | Typically hydrated lime or natural hydraulic lime 4 8 . It carbonates over time, absorbing COâ‚‚ and contributing to the carbon-negative footprint. |
| Water | The activating agent for the chemical reaction in the binder. | Used to mix the hemp and lime into a workable paste. The mixture sets and hardens as it dries and the lime begins to carbonate 4 . |
| Pozzolanic Additives | (Optional) Accelerate the setting time and can enhance strength. | Materials like metakaolin or volcanic pumice are sometimes added to the lime binder to speed up the hardening process 4 6 . |
| Structural Frame | Provides the load-bearing strength the hempcrete lacks. | A frame of timber, metal, or concrete is always used in conjunction with hempcrete walls to support the building's loads 2 8 . |
The woody core of industrial hemp provides the porous structure that gives hempcrete its unique properties.
The lime matrix binds the hemp particles and continues to absorb COâ‚‚ as it cures, contributing to carbon negativity.
Activates the chemical reaction in the lime binder and creates a workable mixture for construction.
The Science Museum Group's hempcrete store is more than just a warehouse; it is a testament to a new paradigm in sustainable construction. It powerfully demonstrates that the most advanced solution for preserving our past can be found in natural, low-tech materials. By choosing hempcrete, the museum not only protects its collections but also actively fights climate change by locking away carbon dioxide.
The success of this prototype provides a scalable blueprint for museums, galleries, and indeed any building project seeking to balance operational excellence with environmental responsibility. As research continues to optimize hempcrete mixtures and building codes increasingly embrace bio-based materials, this ancient plant is poised to play a vital role in building a more sustainable future.