Heinrich Wolff, the architect behind the 'Hemp Hotel building in Cape Town, South Africa, has now been named the world's tallest building constructed of Hemp.

A hotel made of hempcrete blocks and hemp building materials. But what is that?

The current building we are working on has a concrete structure (floor slabs, columns, beams, and lift cores) with hemp blocks used as the infill between the structure.The advantages of using Hemp are that they are lighter in weight, have superior thermal and acoustic performance, and have excellent fire resistance compared to standard block work.In addition to this, they have the benefit of being able to absorb CO2.

Is the usual stuff we know, mud, steel, clay bricks, never used?

No. We still go with concrete and steel. We have mitigated the use of concrete in our building by including TABS (a thermally activated building system).These are embedded pipes in the concrete slabs that heat and cool the slab, effectively using the concrete as a thermal battery. This eliminates the need for mechanical heating and cooling.

But are the hemp blocks carbon neutral?The calculations: 1m3 of

Hempcrete typically sequesters between 300 and 500 Kg of greenhouse gas emissions. When the CO2 footprint of the block is less than neutral, the block has the net effect of removing CO2 from the atmosphere rather than contributing to it.

A hemp-built hotel; this seems like a try and error in South Africa, is it?

There are other buildings made of Hemp in South Africa. Ours is the first one with three stories out of Hemp in South Africa. We have built eight so far. Three more are under consideration.What motivated you to say, "I want to do this in Cape Town," out of all the places in the world? The primary inspiration for creating the "Hemp Hotel" is our client Duncan Parker, the owner of Hemporium, who has been pioneering the industrialization of Hemp in South Africa for the last 25 years. Further, we have been inspired by the work done by hemp pioneers like Tom Wooley, Steve Allen, Ralph Carpenter, and Iso-Hemp, who have been working with Hemp as a construction material in Europe and England. On our side, we have been designing hemp structures for the past 14 years to stimulate the eminent hemp industry in South Africa. We believe that the future of construction will be bio-based and that there are great opportunities.

Is the building now working?

It'll be finalized in the coming months.

Is this way of civil construction cheaper than the usual clay bricks, wood, and steel stuff we know?

It costs more, in the beginning, to build a house with Hemp. But you save money in the long run because of its superior thermal performance. And in massive amounts, Hemp quashes CO2emissions.

Written and Published by Ray Mwareya in Weed World Magazine Issue 160

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