Building a Hemp House

Case Study

The advantages of a hempcrete are numerous. Hempcrete is a high performance, low carbon, low energy, biocomposite building material. Hempcrete is highly insulating and breathable, and these two properties do reduce the energy required to heat the house. A breathable building allows moisture to move through the walls eliminating damp, condensation and mould problems – there must be nothing in the walls to stop this flow of moisture, in a breathable building you cannot use plastic membranes, vinyl wallpaper or non-breathable paints.

We started our project in January 2013, the old house was demolished and foundations were built to building control requirements and underfloor heating was installed on the ground floor prior to the concrete floors being laid.

The timber frame was built by Turner Timber Frames of Hull and was designed by them specifically for use with hempcrete. The main difference was that they had to omit the vapour barrier to allow the hempcrete to breathe, and the frame also needed horizontal laths for the hempcrete to bind to. This frame was erected in August 2013. First fix electrics and plumbing were then installed.

Hempcrete, using our own HempBuild and a binder, was sprayed directly on to breathable wood wool boards attached to the inside of the timber frame. Spraying hempcrete greatly reduces building times. While the hempcrete was drying, hardwood windows and external doors were installed by a local joiner. Who also built the oak framed entrance porch. The exterior walls were finished using HempBuild-Fine, lime putty, and sand render.

The house is on three levels, the attic is accessed by a small staircase, and includes a large playroom. The “warm roof” is insulated with Thermafleece Natrahemp insulation (made from hemp fibre grown on our farm) and the roof is tiled with recycled rubber “eco-slates”. These give the appearance of slate but are much lighter, so reduce the weight of the roof considerably, are easier to work with and reduce waste. The roof overhangs the walls to give protection from the weather. Internal walls and ceilings were plastered with HempBuild-Fine and lime putty plaster and then decorated with Earthborn Clay Paint to maintain the breathable nature of the walls.

While the hempcrete was drying we installed the windows and external doors. These were made by a local joiner out of hardwood as we liked the look of wood windows.

We built a walk-in fridge, the heat produced by the condenser is used to dry clothes in the utility room. We fitted a mechanical heat recovery and ventilation system (MVHR): which removes moist air from the kitchen, utility, and bathrooms and introduces fresh, filtered, pre-warmed air to the living rooms and bedrooms giving a healthier atmosphere and also eliminates the need for trickle vents in the window frames. We also installed a central vacuum system to help reduce dust; these two systems benefit us all, especially one of our sons who suffers from allergies and asthma.

The house is plastered throughout with a hemp-lime plaster to maintain the breathable nature of the wall and decorated inside with breathable clay paint. We used Earthborn clay paints.

The project itself took us 2 years and we moved in in April 2015. We are extremely pleased with how the house has turned out: it is bright and airy with lots of open space and warm enough for us all.

Please don’t hesitate to contact East Yorkshire Hemp if you are considering your own hempcrete build we will be happy to share our experiences with you.

Hemp lime construct hand casting – www.ukhempcrete.com

Hempcrete spraying – www.hemplimespray.co.uk

Timber frames – www.turnertimber.co.uk