Jeremy Blake, Founder of Jeremy Blake Architects, has over 40 years of experience in design with specialisations in sustainability and hospitality. Building heritage and conservation are primary concerns for Jeremy, demonstrated by his work with BREEAM, “The world’s leading science-based suite of validation and certification systems for a sustainable built environment”. In his experience, Jeremy has noticed architects tend to focus on energy and water conservation over the thermal performance of a building. Hemp stands out as a tool to counter this imbalance in construction.

Jeremy’s presentation went into depth on the incredibly virtuous nature of hemp if used appropriately. However, like Tom Woolley, Jeremy highlighted how this has unfortunately been curbed on many occasions by a lack of belief in hemp’s capacity within construction or sheer ignorance around its application. But Jeremy’s presentation gives a largely positive outlook for hemp’s industrial growth within the UK and beyond.

Hemp Shiv

Jeremy’s introduction emphasised hemp’s unique nature when it comes to crops. A grand opening fact was the speed at which hemp grows, second on the planet only to bamboo (2.00 – 2.07). Hemp can be sown in April and, within 14 weeks, grown 14ft. This growth is due to its enormous taproots. These lead up to the stem of ‘the amazing cellular structure to support this 14ft plant. No plant has a cellular structure like this (2.32 – 2.48). Furthermore, unlike most other crops, you don’t need to nitronate the soil (3.04 – 6). In fact, ‘hemp is the most virtuous of materials because apart from sowing in the ground, the taproot actually self-nitrogenates the soil, which means when the farmer plants winter wheat crop in the same soil in August or September, his yield increases by about 3 to 5%’ (8.30 – 8.52). 

Historic Applications

Jeremy’s presentation also revealed how integral hemp was historically and continues to be in modern systems, from hemp parchment for King James’ Bible to hemp rope used in the construction of Egypt’s pyramids. Hemp was vital, even providing the necessary rope and sail material for Spain’s attempted invasion of England in the 16th century (3.50 – 4.50). 

Modern Applications

Present-day scenarios see hemp use across many industries, including transportation, biofuel, clothing and textiles to construction. Construction was the primary focus of Jeremy’s presentation. However, Jeremy also mentioned the stunting of hemp in modern systems due to powerful bodies, such as Dupont and the steel industry. These companies saw hemp as a primary obstacle to their success. Their influence was so significant that they helped instigate the US government’s implementation of the Marijuana Act in 1937, which included banning hemp products (5.48 – 6.00). 

Why Construction? It is Literally Cradle to Cradle

Jeremy was keen to highlight the circular role hemp can play in human systems, offering us material for construction, the regeneration of farmland and the ecology as a whole. ‘Hemp fibre, once you’ve used it in a building, you can crush the building, scatter it on the field, and sow your hemp seed. It is literally cradle to cradle. So it is the most virtuous building material in that regard.’ (8.53 – 9.30). 

Thermal Efficiency

Drawing on hemp projects with hemp from the early 2000s, Jeremy demonstrated that even then, before the vast data that exists now, hemp and lime combined were proving more than a match for conventional construction in terms of thermal capacities. This project, based in Haverhill, involved a pair of experimental hemp houses built alongside regular terrace homes. A fantastic reveal, captured by thermal imagery, was the difference in thermal retention between the hemp/lime houses and the conventional.

The traditional houses were up to u-value standards, however, the heat loss from these houses was drastic compared to the hemp builds. While the heat was leaching out of the traditional homes, as seen by the intense red-orange from thermal imaging, the hemp houses remained dark, bluish purple on the outside, showing their excellent retention of indoor heat (10.45 – 11.40).

At a later stage, Jeremy mentions the cost of building a hemp/lime home of a similar size, completed much more recently but still several years back. While not considering the foundation and infrastructure, its cost was £40,000 (21.40 – 22.10). 

Large Hemp Builds

Jeremey has worked on several substantial projects, from collaborating on the Adnams Brewery Distribution Centre to The Dorchester Collection’s Country House Hotel and Spa. Both projects were immensely successful and brought hemp’s magnificence into the limelight. 

Adnams Distribution Centre

Initial trouble around construction for Adnams meant the desired hemp, lime and timber materials underwent rigorous testing. But this worked out in Adnams’ and hemp’s favour as the tests, experienced at Bath University and BRE’s Garston facilities, saw hemp and its complementary materials pass with flying colours.

Tests included fire resistance, which proved hemp is incredibly difficult to combust, surpassing the assumptions of those involved in the experiments by at least a day. However, like Tom Woolley, Jeremy highlights the scepticism towards hemp’s ability to perform. As a result, Jeremy and the team involved were to leave space in the facility ‘for retrofit air handling units’ to maintain temperatures should the hemp lime materials fail to mitigate temperatures.

Jeremy informed us that in the 15 years that the facility has been open, this backup system has never been required. He also discussed the vast carbon sequestration success the building had already provided Adnams (12.15 – 21.05). 

Coworth Park

Jeremy expanded on the efficiency of such biobased construction systems with The Dorchester Collection’s Coworth Park Country House Hotel and Spa project. 

A key element was the speed of this project. Planning began just before Christmas; they were on site by March, and the building was complete in time for a wedding by August. This project also brought attention to the benefit of natural builds to our health, particularly respiration. Unlike modern, petro-based materials, which release harmful particles into the air, hemp and lime builds have significantly improved conditions such as asthma (24.010 – 28.00). 

Archive Facilities

A most exciting aspect was the role hemp and lime can play in maintaining optimal archive conditions. Hemp and lime can easily replace and reduce the cost of air filtration systems often used. This strategy is now being implemented nationally in UK-based archives (29.45 – 30.30).

Unfortunate Publicity

In 2013 Kevin McCloud of Grand Designs partook in a hemp lime project. However, this project brought some bad press for hemp for a few reasons:

1. McCloud’s renown and that of Grand Designs meant a lot of media coverage, scrutiny and pressure for this project to succeed.
2. The project’s contractors should have appreciated that if you ‘use hemp in the English climate, it is very susceptible to cold and wet weather. Unfortunately, this project’s construction began during January and February of a particularly harsh UK winter. 

A Fortunate Outcome

The failure of this project led people to investigate offsite construction preparation 28.03 – 29.15). So it has influenced the greater adoption of modular-style building techniques in the UK. The construction of a large M&S in Ellesmere later employed this method with great success. By this stage, designers had discovered the optimal thickness for lime/hemp thermal efficiency, much less than that used at the Adnams facility. (32.29 – 33.40). 

Jeremy’s experience with hemp and his admiration and respect for it as a material shone throughout the presentation, inspiring us all. To see some of the projects that have come to fruition over the years clearly show how hemp is a valid alternative to conventional construction materials. 

If you would like to hear more about our CPD Days in 2023, please do get in touch.