ModCell Schools: Construction & Performance


ModCell Renewable Schools is a fast, affordable, turn-key solution, providing sustainable teaching space within existing school grounds. 

The product is a prefabricated straw bale construction system that uses renewable materials and local labour to deliver a high quality, modern method of construction (MMC). 

ModCell Renewable Schools are particularly well-suited to helping education authorities and school governing bodies meet the shortage of teaching spaces and need a rapid, cost-effectively and sustainable solution. It provides a high quality alternative for needs that are often assumed can only be met by temporary classrooms.


ModCell panels can be used to create a load bearing structure up to three floors high. Alternatively the panels can be used as infill panels with timber, steel and concrete frames. Several different panel sizes and finishes are available. The ModCell wall is either plastered using a protective lime render, or clad with timber. ModCell is designed for use in offices, schools, housing and commercial buildings.


Resource efficiency

Materials wastage 

• Factory cut waste is minimal as each panel is precision cut from larger sheets. 

• Straw bales trimmings are either composted, used as bedding for farm animals, or used as biomass fuel in the factory’s biomass boiler. 

• Virtually no onsite waste is produced. 

• Lime render is spray-applied with almost no waste. 

Embodied carbon 

• The straw crop absorbs CO2 as it grows. 

• A single ModCell panel (W 3190, H 3040, D 480) contains the equivalent of 1,400kg of atmospheric CO2. This carbon is locked away for the full lifespan of the panel. 

• Embodied carbon in the use of steel has been reduced. Timber is used instead of steel rebar to pin the bales. Threaded steel rods and bolts are used to brace the frame and retain the bales in place. Sole plates and base rails are used instead of brackets. 

• Transport CO2 is kept to a minimum by manufacturing the panels as close as possible to the construction site. 

Water use 

• ModCell assembly is a dry construction method requiring no water use onsite. 

Life span (e.g. durability) 

• Life expectancy is the same as traditionally constructed buildings. (There are thousands of straw bale buildings across the world; some over 120 years old.) 

End of life (e.g. reuse; recyclability) 

• ModCell lends itself to flexible layouts that can easily be modified or expanded by adding or removing panel sections. 

• Panels can be disassembled and all elements re-used, used as biomass fuel or safely composted. 

Resource scarcity and security 

• Panel frames are made from off cuts from the timber industry. 

• Straw is an annual 3 million tonne waste by-product of the agricultural industry. ModCell works with local farmers to identify sources of waste straw and locations to assemble ModCell panels. ModCell reduces the cost to farmers of straw waste and provides an additional income. 



• Rapid construction: building is a process of assembly rather than construction. 

• High thermal efficiency: ModCell walls are free from thermal bridging and can achieve u-values between 0.13 and 0.19 W/m2/K. 

• Acoustic performance: the panels produce a reduction of up to 50db. 

• Fire resistance: lime rendered panels have a 2 hour fire rating

• Flexibility: buildings can be adapted and extended by adding or removing panel sections. 


Two schools:

Castle Park Primary School Learning Plaza


The Learning Plaza is a flexible and technologically-rich learning environment for a combined group of Year 5 and 6 children at Castle Park Primary School. In addition to being flexible, the open plan nature of the Plaza also increases the school's ability to adapt this space in the longer term to the requirements of new national strategies as they come on-stream. The Plaza also adapts well to new approaches to learning and teaching as they are developed by the local authority and school.

The building design adopts a 'passive first' approach to sustainability. In essence, the building fabric acts as a moderator of the external climate, whilst the heating, ventilation and lighting installations deal with the reduced demands of the moderated internal climate. The building is highly insulated, with 26 ModCell panels; selected for its insulation values and airtightness properties.

As the Plaza is next to the existing school, with classrooms in operation just a couple of metres away from the new Plaza location, ModCell has the added advantage of the quick erection time on site, reducing disturbance to the school. The panels will took only 1 week to erect during the February half term 2011. The panels were constructed at the flying factory less than 5 miles away from the school, using Monmouthshire straw.


Holme Lacy Student Campus


New student facilities for Herefordshire College of Technology

Designed by Hewitt Studios with Integral Engineering Design for the College's campus at Holme Lacy, the 100- seat cafe uses ModCell straw bale panels and features a 'green' sedum wall and terrace seating area. Local students helped to construct the pre-fabricated timber frame.

Local materials were an important part of the low environmental impact design. Nearby Pound Farm provided 60 straw bales, while timber came from Western Red Cedar trees growing in the college's 150 acres of forest and woodland. The building is self-sufficient, providing its own on-site energy generation through solar and wind power. Other environmental features such as super-insulation and passive environmental controls also help to minimise embodied energy.

Rob Dunne, Assistant Principal, said the project was a great success: "This is all home-grown stuff - it's not only reducing the building's carbon footprint but also connecting the structure to its local environment."

Providing a welcome hub for both socialising and learning, the café is designed to be dismantled after 15 to 20 years and all components can be re-used or re-cycled. Postgraduate students at Nottingham University plan to use the building as a research model to test new environmental technologies.

The extension was conceived as a College learning aid in low-impact environmental design with the following features:

• Prefabricated Construction: The building structure was prefabricated in order to minimise environmentally disruptive on-site works. It was assembled by a workforce comprising of 4 Nottingham University postgraduate students.

• Demountable: The building is designed to be dismantled at the end of its 15 year design life and most components can be re-used or re-cycled.

• Energy efficient: The building requires very little heating/cooling as the straw bale insulation is approximately 3 times better than current Building Regulations require. The building is naturally ventilated and makes use of natural daylight where possible. All artificial lights are on motion / daylight sensors.

• On-site energy generation: The building generates up to 6kW of green electricity from a combination of photovoltaic panels and wind turbine.

• Local Materials: The cedar cladding/boarding and organic straw insulation come from the college estate. Varieties for the green planted wall were sourced from local nurseries.

Text and images supplied by Hewitt Studios LLP