‘Holistic view’ brings hemp’s value proposition into focus

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Ian Pritchett of Greencore Construction.

INTERVIEW: Ian Pritchett

Managing Director/Greencore Construction – UK

Ian Pritchett is managing director at Greencore Construction Ltd. in the UK. A physics graduate from Durham University with over 25 years experience in historic building repair and eco-buildings, he previously was managing director at both IJP Building Conservation, and Lime Technology Ltd. That’s Ian’s hemp home!

HempToday: The Marks & Spencer Cheshire Oaks project was revolutionary in its use of hemp in a large-scale project. What were the lessons learned, and how does the market shape up for the future in this sector?
IP: The project was a great success. It demonstrated that off-site panels are the best way to deliver fast track projects for mainstream clients. The independent post occupancy evaluation (POE) showed that the store used 60% less heating energy than predicted. It is unique to have such a large (positive) performance gap, but we need to find better ways to accurately predict thermal performance in order to convince others of the benefits of hemp construction.

HT: Can you describe the basic value chain through which you get Greencore products and projects into the commercial pipeline. If we start with hemp in the field, how does it get to you and how many steps and parties are involved in getting the product to market? Where do you source your raw hemp material?
IP: We buy our hemp shiv in the UK, mix it with UK produced lime and cast it into our Hempcell panels. We sell these directly to the end user, so it is a pretty short chain. In some projects Greencore Construction is the end user when we are developing sites for sale.

HT: How do you talk about the value proposition of hemp-based projects with your clients? Surely it’s more expensive. Or maybe the question is: what kind of clients are drawn to hemp?
IP: For us, the client is the most important person in any project. We look for discerning clients who take an holistic view of the build cost and will later benefit from the comfort and energy savings. It is more difficult if the client is only interested in the lowest construction cost. Our clients are looking for comfort, health, low energy bills and low embodied carbon.

HT: You have experience in historic building repair. We’ve seen some restoration projects around Europe that employ hemp. This would seem destined to always be a niche market, but how is hemp comparing to use of other materials in such projects?
IP: Hemp-Lime has two important markets in the historic building repair world, where it can demonstrate superior performance. First, infill panels in historic timber framed buildings. It is easier, faster, cheaper and better insulating that the traditional “wattle & daub” of the past. Second, for use as internal wall insulation (IWI) on old masonry buildings. The hygro-thermal properties seem to completely eliminate the risk of interstitial condensation, which is a big risk with other forms of IWI.

HT: Similarly, what about hemp as a material in retro-fit?
IP: Hemp-Lime is less practical as a retro-fit solution for newer buildings, because of the thickness required and slow drying time.

HT: You pioneered the use of lime mortars in the new building sector. What’s the market status of lime mortars among alternatives these days?
IP: Lime mortar in new buildings is still a niche market, but it is a significant niche and it is no longer viewed as unusual. There are now well over 1000 new buildings built with lime mortar in the UK; many bricklayers are familiar with it and it is routinely specified by architects for new masonry buildings.

HT: What’s the status of hemp growing in the UK. The EIHA reported 160 ha. under cannabis sativa in the UK last year, mostly by small farmers. What’s the outlook for expanding hemp agriculture in the UK?
IP: It is a small but growing market. Unfortunately the UK market suffered a significant set-back when Hemp Technology went out of business at the end of 2013. It will take time for the UK to get back to the same area of hemp cultivation.

HT: How do you see the situation with certification for hemp-based building materials? Is there progress at the EU level developing proper standards?
IP: The development of any standard takes many years and costs a lot of money. We will have to be patient about the creation of new standards. In the mean-time we may see some hemp products gain CE marking under current standards. We are in the process of CE marking our Hempcell panels under a standard that will be published soon.

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