The first passive house with cellular glass walls

logo_smallA typical saying is that passive house walls with cellular glass are becoming too thick due to the moderate thermal conductivity. Like most sayings, the truth is something else, it is founded on conservatism. Indeed, Denmark has its first cellular glass passive house and the next one is underway.

The house is a Clean Tech Block result, which is already mentioned in previous blog. Clean Tech Block is a project from  Gråsten Teglværk, the University of Aalborg and the University of Ljubljana.

Havnevej 60 (u_stillads) 001.jpeg

newspaperThe project is described in a  newspaper, the “Der Nordschleswiger”.  It is real example of durable building and all the typical certificates are granted.

The choice for cellular glass is obvious:

  • air tight (passive house standard)
  • vapour tight and so no risk for humidity accumulation
  • free from rodents, ants and other animals.
  • long if not eternal lifetime
  • ecologic, according to the Swiss even the most ecologic thermal insulation
  • non-combustible
  • self-supporting, no deformation due to mechanical load or temperature
  • almost the same thermal expansions as the other minerals used in the building
  • not expensive if produced by direct foaming of recycled glass.

In our opinion, this is a major step in cellular glass building.

Cellular glass boards as a fire resistant material

logo_smallCellular glass is well known as a non-combustible thermal insulation, which is in Europe expressed as EUROCLASS A1. It says that this material does not contribute to fire at all because the organic content, expressed in %C  is less than 0.1% for cellular glass.

However, this material on his own is not known as a fire resistant material because it cracks due to thermal shock during fire and allow in that way that gases, flames and radiation may pass through the cellular glass board.

GLAPORlogoBut today, FOAMROX announces large fire resistant boards, based on cellular glass. Indeed, the large GLAPOR cellular glass boards seems to have a special coating. I guess a glass fibre mesh is used to take the tensile forces and to keep the board together in case of breakage. This fibre mesh is probably adhered with a mineral adhesive.

The website declares that an EI=60 is reached according to the following ISO-kurve.


This means that the system resists shortly 940°C which is above the foaming temperature of GLAPOR ware. In fact, we have here an intumescent. This is a substance which is swelling due to a temperature rise, which is interesting in case fire resistance is needed.


foamroxThe boards have large dimensions 3.73m x 1.2m and 10.5 cm thickness. The 1.2m is the original GLAPOR dimension.

Which other products do we have with EI=60. Fermacell offers the following system 3S21A1 in the Fermacell-firepanel-A1 leaflet. The weight is 40 kg/m² to be compared with only 17 kg/m² for the FOAMROX board which has the same thickness 105 mm. It is also clear that much more manhour will be involved in the FERMACELL case, while still with a material cost above 20€/m².



Other systems combine lower (fire) quality gypsum boards with mineral wool, which will be much harder to dispose later on.

From the above, it is clear that the FOAMROX boards have a nice future.


Ants like XPS and EPS but hate cellular glass

logo_smallPolystyrene is used in the thermal insualtion world in two versions: XPS (Extruded polystyrene) and EPS (expanded polystyrene). Both are used as thermal insulation in buildings besides cellular glass.

mierAnts are insects which lives in large groups and may destroy some building materials. It has been found in an extensive work of the Norwegian Institute of Public Health that ants are excaviating XPS and EPS in an important way, while leaving cellular glass in peace.

Hereunder, we give a comparison figure, extended with glass wool and mineral wool.


It is clear that cellular glass is not of interest for ants, which is a major advantage of cellular glass compared to the other thermal insulations. Some people should argue that a laboratory experiment is not the real case. The following XPS-boards, found on a jobsite in Germany  in real life says everything.

The damage to the building is clear but these ants do not absorb this polystyrene. It ends as plastic contamination in the soil and is dangerous for the human health. It is amazing that this material is still allowed.