passive hemp house self-build


New Build – Hempcrete Extension to a Semi Detached House.

Project Details

Location: Belgium.
Project Type: 50 sq.m. extension to lower level of a semi detached two storey residence.
Project Duration: 6 weeks.
ProjectSummary: A single storey extension to side featuring large bay window clad with 120mm Hempbuild Isohemp hempcrete blocks.

Methods of construction specific to this project

The extension was added to the rear of the building, the load was taken by steel beams and a wooden load bearing framework. The foundation is a reinforced concrete strip around the perimeter of the extension, which is raised 150mm above the finished ground level. The 120 mm Hempbuild Isohemp hempcrete blocks were then laid on a DPC membrane which provides a damp proof barrier between the foundation and the hempcrete blocks. Isohemp adhesive was used in the hempcrete block construction and the blocks were tied to the structure using stainless steel ties. Gas and electric services to the rear were piped directly through the blocks and windows and doors were sealed at the edges with expanding foam. The final Interior was finished with Isohemp PCS plaster and the exterior with lime plaster.

Materials used

  • Hempbuild 120 mm Isohemp Hempcrete Blocks
  • Supporting Angle Brackets
  • Stainless Steel Wall Ties
  • Isohemp Mortar Adhesive
  • Reinforced Mesh – Weather Frame Seals – Angle Beads
  • Lime Exterior Plaster
  • PCS Interior Plaster
  • Tools & Accessories

Additional construction methods available on this type of project

One possibility is to use a larger hempcrete block which would increase the thermal mass of the structure and provide greater warmth and comfort whilst reducing energy usage. This would be something to consider in cooler climates.

A range of plasters and finishes could be used on the exterior facade. Traditional sand and lime mixes may be used. Clay based plasters and paints maybe used or external wood cladding may be used, all depending on the specification from the client and architect.

120 mm Hempcrete Block Advantages

  • Quick and easy implementation, lightweight, yet solid with good thermal mass.
  • Easy and problem free to fix items directly to the wall, gutters, lights, etc.
  • Thermal regulation: The  hempcrete block naturally stores and dissipates accumulated heat, which helps to keep the living space cool in summer and warm in winter.
  • Natural humidity regulation: Thanks to its high permeability to water vapour, the hemp block acts as a moisture buffer. Deals well with moisture and dampness in old walls.
  • Mold resistant: Hemp has a strong natural resistance to mold and bacteria.
  • Environmentally friendly: Our hempblocks are carbon negative and contain no VOC’s or harmful toxins for inhabitants.
  • Fire resistant: It is inflammable and does not release toxic gases during its combustion.
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