A lot of hemp – little CO2 emission

Housing Estate Clay Fields – Riches Hawly Mikhails Architects

Suffolk, England

Social Housing in Suffolk, England constructed using Hemcrete

There are many ‘green’ construction principles being passed around these days as magic solutions for the impending climate chaos, but very few are actual solutions, more seem like commercially labeled alternatives to the same old products and techniques. Few designers venture into the practicalities of achieving real success through careful green thinking and the very skilful marriage of sustainably sourced and efficient products with good eco-friendly design. In a world of fake sustainability and eco-credential madness, Riches Hawly Mikhails Architects are a deep breath of fresh ‘green’ air. Clay Field’s in Suffolk, their recent low-cost housing scheme is a perfect example of what sustainable architecture should be like today (not in the future!).

Their aim was to design a low-cost, locally inspired housing in the context of an existing village and develop exemplary new approaches to sustainability. The completed scheme is closer to zero carbon than any other multi-unit residential project built I have seen in the UK. The Architects used ‘Passivhaus’ principles, biomass communal heating and the innovative hemp-insulated airtight construction.

{ Basic Passivhaus Principles }
- very good levels of insulation with minimal thermal bridges
- well thought out use of solar and internal gains
- excellent level of air tightness

(More on passivhaus projects here)

Clay Field achieves a 60% reduction in embodied and lifetime energy use over other typical housing schemes (based on current building regulations).

The site was organized so that all the houses face south giving them very good passive solar gain (free heating essentially). The 26 affordable homes (nine three bedroom houses, 13 two bedroom houses and four flats)are also arranged so that the row of houses all get equal uninterrupted views and daylight. South facades have 50% glazing which increases the solar gain needed. Any excess heat, gets redistributed through a heat recovery unit which either extracts it, cooling the interiors, or is used to heat incoming fresh air.

The construction uses sustainably sourced timber frames lined internally with a breathable gypsum board. The boards are not only breathable, but provide the much needed racking strength of the otherwise ‘toothpick’ timber frame. The walls are then built and insulated with Hemcrete, a mix of coarsely cut hemp and hydrated lime, with a cement additive to accelerate the curing process . This is the real secret of the project and the basis for this simplest of green solutions. The Hemcrete acts as the building material, insulation, breathing membrane, and waterproof layer. Sprayed over the frame, Hemcrete sets to form a solid wall without air gaps that would have compromised the efficiency of the incorporated system of whole-house ventilation. The outside of the hemcrete is finished in 20mm Lime render which protects the walls and suits the breathability of the hemcrete.

Hemcrete being sprayed

At the same time because it is made from Hemp, the walls have captured CO2 wich combined with the timber structure (also a renewable source) makes this a truly environmentally friendly housing marvel that is effectively carbon negative. (More on the wonderful properties of Hemcrete here and here)

Images © Riches Hawley Mikhail Architects

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