Holz100 Is a Cross Laminated Timber Held Together With Dowels

Touring the exhibits at the Wood Solutions Fair, I saw this: a block of wood held together with dowels. I called out “Brettstapel!”, the name of a clever method of building with wood that we have covered in TreeHugger, where the wood is held together with very dry dowels; when they absorb moisture from the surrounding wood they expand and lock the assembly together. (It is also now called DLT or Dowel Laminated Timber.)

In fact, the people in the Holz100 Canada booth were showing a different product, Holz100, invented and patented in 1998 by treehugging engineer Dr. Edwin Thoma. Brettstapel is made by stacking wood planks. This is much more like cross-laminated timber with dowels instead of glue:

Timber boards are layered vertically, horizontally and diagonally into compact assembly parts. Dust-dry beech wood dowels are driven through the layers to connect them. In place the dowels absorb residual moisture from the layers and swell up to connect permanently to the surrounding wood, like branches and their tree. These dowels powerfully connect single layers of wood into one massive thick block.

I believe that dowel laminated timber is one of the most interesting ideas in wood, primarily because it is just that, solid wood with no chemicals, no glues. The Thoma design as a few additional benefits; being a CLT it is probably stronger and more stable. It uses a lot of wood but Holz100 is made from totally sustainable sources. There are other pluses, including energy efficiency, a healthy, biophilic environment:

Comfortable and cozy living in 100% pure natural wood—no off-gassing from glues, wood ‘preservatives’ or other artificial materials. Many research studies in various countries have shown that living in solid wood brings about harmony and relaxation, slows down the heart rate and boosts our immune system and provides restorative sleep at its best.

Building with solid wood also controls humidity naturally. “There is no necessity for vapour barriers. The wood breathes by itself and naturally controls the indoor climate. The air tightness ensures no unnecessary heat loss.” Such thick wood walls also provide great soundproofing.

It's all cut to order in the factory with efficient tools:

Walls, ceilings and roofs can be made in thicknesses from 12 to 40cm. Production drawings are created according to customised individual plans and client requirements. This makes a high level of prefabrication possible. Grooves and cut-outs for electric wiring, windows, doors and other construction details become part of the prefabricated blocks. This minimises the efforts needed on site and helps save money and time in raising. The speed of construction is a huge benefit in wet and cold climates.

I am skeptical about some of the claims made for the product, such as “Holz100 almost entirely shields against high frequency radiation (eg, emitted from mobile telephone masts) whilst not interfering with the earth’s magnetic field,” and also about the benefits of "moon" timber, "harvested during the waning moon when the sap in the trees are at its lowest."

But there is a lot to love about a pure wood environment. The Holz100 appears to cross the structural benefits of Cross Laminated Timber with the glue-free solid wood virtues of brettstapel, which makes a very interesting product.