Thermal insulation according to Architect Konrad Fisher

logo_smallKonrad Fisher was an herectic against outside thermal insulation on walls with a rendering. According to him, all thermal insulation except (closed cells) cellular glass develops mold and other problems in the rendering, which make look the rendering dirty. The rendering has to be cleaned regularly or to be treated by harmfull and expensive fungicides. Bot operations have a large cost.

konradfischerIn his opinion, cellular glass, due to his closed cell structure is a much better alternative, which does not become wet and will not induce mold on the rendering. He explains everything in a YouTube movie, however in German.

He also mentions the price of cellular glass but he is clearly not aware of the new generation cellular glass from GLAPOR at 250€/m³. In this case, maintenance of the will be much lower, generating a payback for the cellular glass.

mold_rendering                   fisher_schaumglas

Above, you observe a dirty rendering due to mold and on the right the solution according to Konrad Fisher with cellular glass in his hands. These pictures can be found in the YouTube movie.


Stanley Kubrick has known it already a long time …

logo_smallIn 1969, a world famous movie was produced by Stanley Kubrick:   2001: A Space Odyssey. This link on You Tube shows a part of the movie. I give one frame hereunder:


It is clear that Stanley Kubrick predicts the large monolitic  GLAPOR cellular glass boards as the future material (Monoliths) to generate a new evolution step.

In Arthur C. Clarke‘s Space OdysseyMonoliths are machines built by an unseen extraterrestrial species. In the series of novels (and the films based on these), three Monoliths are discovered in the solar system by humans. The response of the characters to their discovery drives the plot of the series. It also influences the fictional history of the series, particularly by encouraging humankind to progress with technological development and space travel.

Indeed today, GLAPOR cellular glass is participating for a future ecological world.

Houses with cellular glass walls

logo_smallIt is already mentioned in this blog that large cellular boards can be used as thermal insulation and also as construction material, giving the stability of the wall. Especially in the passive housing market, this can be important. Today, we have two examples in Europe, where people on their own initiative started to use cellular glass as stability element and thermal insulation.

In this system, cellular glass is used in combination with brick slices by Clean Tech Block.


A passive housing U-value can be reached with normal wall thickness (< 400mm) and cellular glass, directly foamed from recycled glass. In the following system, cellular glass is used in combination with wood by Tebit Oy, Finland.


It is clear that the future is great for not expensive large boards cellular glass like today produced by GLAPOR cellular glass.

Hydroculture with open cell cellular glass

logo_smallBELGLAS is still convinced that there is a market for open cell cellular glass. Acoustic absorption is one application, hydroculture a second like already demonstrated in a post about Growstone.

At GLAPOR, some possibities with open cell cellular glass boards were investigated …


I gTomato isolated on white backgrounduess we eat today the first GLAPOR tomato …. The cellular glass perfectly controls the the stability of the root and the  water and mineral content the plant gets to absorb …

Cellular glass in flat solar collectors

logo_smallFlat solar collectors to heat water have still a large future with an efficiency up to 85% compared with photovoltaic, which is still only 15%. A typical solar collector consists of a glass pane, which allows transmission with minimum refelection of sun radiation on fluid cooled heat exchanger, which is thermally insulated at the backside. This insulation will be mineral because temperatures above the glass temperature of polystyrene (90°C) or another polymer can be expected.

HamSun-Hocheffizienter-Flachkollektor-1-St-202m_b2Cellular glass as thermal insulation was out of the question due to price and dimensions. Indeed, 0.60 x 0.45m boards for solar collectors of 2m x 1m are difficult to use. In the picture, the heat exchanger tube is put on mineral wool in an Al casing for only 245€ VAT included. The efficiency of this cheap solar collector is 75% (cold fluid at entrance) and without fluid flow, the temperature may become up to 208°C. With water, we could attain a pressure of 20 bar in that case, which means we need for example ethyleen glycol (EG) or propyleen glycol (PG) as safe liquid. They have a high boiling point (EG=197°C; PG=188°C) and low freezing point (EG=-12.9°C; PG=-59°C). With a fluid flow rate of 100l/hour, we have a pressure drop of 50 mbar.

For that reason, we could consider to replace the mineral wool with meander tube by a large GLAPOR cellular glass board with the meander channel, milled directly into the cellular glass. The glass cover (eventual a double pane) closes the channel at the top. In this case, the radiation is absorbed directly into the water reducing the temperature gradient between solar radiation aborber and water. This means that the water will be warmer in winter reducing the need for extra heating.

However, this idea is not new. Patent DE102014007805A1 from end 2015 describes exactly the above.


However, an earlier PatentanmeldungWO2012093062A2 (2011) describes also such a system based on foamed glass from recycling glass.


CGcellThis patent was based on research, sponsord by the German government and performed at the Univerity of Freiberg. This is the second time we met this university in the cellular glass world. It was  first with vacuum cellular glass and now with a solar collector.

A solar collector based on large cellular glass boards with the above structure should be much cheaper than the standard equipment, which is today used with a higher efficiency. Cellular glass is heat absorber, thermal insulation and casing at the same time. The difficult problem will be the connection of these cellular glass channels to metal tubes to be able to connect the solar collector on the system. But this problem can be solved with one of the many adhesives on the market. The major problem, the avialability of large cellular glass boards 2.8 x 1.2m is already solved by GLAPOR cellular glass.

Palletizing of cellular glass boards

logo_smallThis topic is maybe not the most challenging, but it is very important. According to the Swiss ECO-scarcity method (UBP), the transport of raw materials and cellular glass is responsible for  20 % of the total damage to the environment due to production, transport and installation of the cellular glass. In other words, 20% of the UBP is caused by transport. It is clear that efficient packing becomes very important.

Forty years back, 40mm cellular glass boards were the standard while today 140mm is the most popular thickness. Transporting 40 mm boards horizontally is a risky operation while this seems logic for 140mm boards. As a consequence, the cellular glass world started to transport vertically. The internal trailer height is maximum 3m with 2.45m internal width to be used with exchangeable EUR-pallets or thinner single use versions. A typical trailer has a floor for 33 pallets, which can be double stapled in the case of cellular glass.


epal-europaletteIn case of vertical stacking, the boards have a width of 450mm (height when stacked) and 600 mm length (half pallet length). Six parcels have than a total height of 2.70m which should become 2, 984m  theoretical total height with two EUR-pallets (144mm height)  to be installed in trucks with internal height between 2.85 and 3m. This is not possible and for that reason thinner and weaker pallets are used for this application to gain about 10 cm tolerance. However, these pallets cannot be exchanged because they are not designed to carry 1500 kg. In case of horizontal stacking, exchangeable EUR-pallets can be used because height is not critical anymore. Two pallets stacked  have to respect a 2.80 m limit to allow loading the trailer. This means that a trailer can be maximally loaded with 79m³ cellular glass.

In case of vertical transport, the pallets have a fixed height  with thinner pallets and I assume that slightly more cellular glass can be loaded, improving the UBP-score due to transport with I guess 4%. But using single use pallets instead of exchangeable EUR-pallets is responsible for an increase of 3.5% UBP. On the other hand, a width of 450 mm (vertical transport) instead of 800mm induces more  joints  after installation and so a decreased thermal resistance. Joints between 0.6 x 0.45m boards are responsible for 5% heat leak , which means that 0.8 x 0.6m boards should leak 3% in the joints.

At the end, vertically stacked or horizontally stacked boards are nearly equivalent if we speak about ecology. The choice depends on the requested dimensions and it looks that larger dimensions (thickness and length) are becoming more popular. Therefore, I guess that horizontal transport with EUR-pallets will be the future on the condition that the EUR-pallets are not covered by hot bitumen on the roof.


ECOINVENT data for building products

logo_smallECOINVENT is a database which contains for many products production data which are important for the environment like the use of primary energy, raw materials, etc. This means that during development of a new product which is based on other products, the developer is able to obtain all data of the products he is using for his invention.

For example, if somebody is using celllular glass besides other materials for the construction of a house, ECOINVENT allows to calculate how much the environment suffered from this construction.

downloadBELGLAS could obtain the public report  about building materials, which is used to generate the ECOINVENT database. Although public, this report could not be found by Google and for that reason, it is included in this post.

On page 456, a very detailed description is given about the production of cellular glass based on a special glass composition. All used raw materials are listed together with their function in the process.

inventThe report mentions the following:

  • Electric melting furnace with molydenum electrodes at 1250°C
  • Grinding with corondum cylinders
  • Steel moulds coated with clay and aluminum hydroxide
  • The use of 10 kg one way pallets instead of 22kg EURO-pallet

In a following post, we will calculate the production cost of cellular glass with the numbers of this ECOINVENT report.

An old but interesting German patent

logo_smallAbout 50 years ago, an invention was made and patented in the VEB Schaumglaswerk Taubenbach, East-Germany. I give the abstract hereunder.

A process for making foam glass wherein mixtures of sulfur trioxide-containing glass and active carbon are first sintered in a pure steam atmosphere having a partial pressure above 200 mm. Hg and subsequently heated at a temperature ranging from 800° to 900 °C to form a foam structure.

steamGlass powder is sintered in a steam atmosphere before foaming. The glass powder is a mixture of a sulphate containing glass and active coal. Due to this steam atmosphere, a better foaming behaviour is obtained and the cells contains up to 11% H2S instead of less than 1%.

It seems that this procedure allows to foam a lower density with improved thermal conductivity.

All cellular glass green roofs with boards and gravel

logo_smallOriginally, gravel was not meant to be used in roofs. But the Kaluga plant produces 300000m³ cellular glas gravel, which is almost completely used for flat roofs. Typically, the upper layer of green roofs is soil, which is needed for the plants but can also serve as ballast.

gravelIn case ballast is present, we have the choice between a warm and an inverted roof. And if an inverted roof is accepted, we can indeed use cellular glass gravel. In case gravel is used under the concrete slab (floor insulation), the gravel is compacted to obtain a large compressive strength. This seems not be necessary for the roof, but this is a wrong statement.

In the roof, the warm side is under the gravel and convection is possible (contrary to the floor). An interesting paper about the thermal conductivity of gravel shows with calculation and experiment that compacted gravel has a lower thermal conductivity than uncompacted gravel.


However, even with compaction, there is always the risk that sudden cold rain water reaches the bottom of the gravel, creating condensation inside the building at the ceiling. This is precisely the effect where the inverted roof got its bad reputation. This can be avoided by installing 40mm GLAPOR cellular glass boards under the water proofing membrane. The  following figure shows such a roof, with a thin layer cellular glass boards to avoid any condensation problem.


By using tapered GLAPOR insulation, drainage is also installed. The water proofing membrane is protected against UV, thermal changes , humidity changes and mechanical damage. In our opion, this is the best roof possible in winter and summer for a very sharp price.



A Trumpian question: Is a passive house ecologic?

I could imagine that President Trump should put this question  and even answer it with no, it is not. Indeed, it is clear that too much thermal insulation takes more from the environment that the energy saved during the life time of the building brings back to the environment. Or in other words, which thickness is the break even point? We answer the question for GLAPOR cellular glass

 Passive houses have generally two requests:

  • The building envelope has to be airtight
  • The U-value should be between 0.15 and 0.1 W/m²K 

GLAPORlogoIt is clear that large GLAPOR cellular glass boards are the most ideal thermal insulation to obtain airtightness. But for an U-value of 0.15 W/m²K, we need 36cm GLAPOR PG600 boards, which is acceptable as wall thickness. Today, value down to U=0.12 W/m²K are already requested in Europe at some places. But is this ecologic? We answer this question with the UBP-system of Switzerland


ubp_passive housegrundschema_der_methodederoekologischenknappheit

For U=0.15 W/m²K, we need at least to use the house 13.5 years to pay back the environment for the production of the thermal insulation. For U=0.1 W/m²K, we have already 30 years. In Sweden for the roof, I found the following on Wikipedia: 

In Sweden, to achieve passive house standards, the insulation thickness would be 335 mm (about 13 in) (0.10 W/(m²·K)) and the roof 500 mm (about 20 in) (U-value 0.066 W/(m²·K)).

For U=0.066 W/m²K, we need already a lifetime of 70 years, while except GLAPOR, thermal insulation manufactureres does  not give a lifetime more than 50 years. And the UBP for all other thermal insulation boards is worse than GLAPOR, saying that even more than 70 years are needed with these materials even up to 150 year. 

trumpThis is a nice example of eco-fundamentalism, when laws forces people to demolish the the environment. Small U-values can only be approved  with thermal insulations with a very long life time and we should ask ourselves: Is this needed? In my opinion, below U=0.05 W/m²K (125 years), Trump should be right.