Using the new building systems from Panbo Systems in Beringe, the Netherlands can add up to considerable savings for growers. According to Ser Huibers, mushroom growers and compost producers can flatten the building costs by choosing for tunnels and growing rooms with ceilings that function as roof.

According to Panbo it is possible to save up to 20 percent when building new growing rooms and tunnels, by choosing a new way of building. In the new system of Panbo the ceiling of the growing rooms or tunnels functions at the same time as its roof. Because of this, it is not necessary to build a separate roof over the growing rooms or tunnels. This means that it is no longer necessary to build a rafter and purling construction on top of the growing rooms and tunnels.

Furthermore, growers and compost producers save money because in the new way of building the roof sheets are superfluous according to Ser Huibers from Panbo. In both the old and the new system the walls and the roof of the growing rooms and tunnels are comprised out of sandwich panels.

In the new system however, the panels in the ceiling are much thicker. They insulate much better than a regular roof. The insulation material in the panels is polystyrene. On this polystyrene layer a metal plate is glued with a synthetic layer on it. This makes sure the roof will not leak.

High temperatures

Subcontractors in the industrial building sector use sandwich panels with polystyrene filling already for decades. But in the mushroom sector these panels where until now not useable. During the steaming process the glue that was used to attach the waterproof sheets to the polystyrene went soft because of the heat. In the past this caused problems with panels that came unstuck. Huibers: “Fifteen years ago the mushroom sector judged polystyrene unsuitable for the construction of mushroom farms.”

In cooperation with Isobouw in Someren Huibers invented a glue that is resistant to high temperatures. This glue is made of poly-urethane. Ten years ago Panbo used these kinds of panels in a growing cell. Huibers: “We used the panels in those spots were it was easy to reach them. If the panels would come unstuck, we could easily replace them.”

Five years ago the company constructed a whole farm with these panels. The panels held together, this gave Huibers confidence in his system.

Thirty years waterproof

Huibers needed more than just a new glue. If you put sandwich roofs on top of the cells, you get seams. Sealant is used to make the seams waterproof. But this only holds a few years. The sealant dries up and gets unstuck.

To prevent this from happening, Huibers also uses an armed uv resistant pvc cloth. “What is so great about this cloth is that we can welt it on the synthetic layer.” To do this Panbo uses a kind of hair dryer. The heat coming out of this device melts both materials together. Huibers: “In the construction of industrial projects this method is well known, but we are the only ones who use it in the mushroom sector.” Panbo has been certified by Isobouw to give out a fifteen year warranty on the welding.

Over the last two year the company realized several mushroom farms with this system. The roof over every growing room is slightly bend to allow a good drainage of the water. This creates a kind of gutter between every cell. The water in these gutters runs through a drain on both sides of the roof. Huibers is very confident in this new construction: “I got on top of the roof at Isobouw. There it was lying for fifteen years. After we swept away some of the dirt it looked exactly the same as it did when they installed it."

Flat Roof System for Tunnels

Stimulated by the good experiences with this system, Panbo investigated the same way of building for compost tunnels. Huibers: The design and detail drawings for the first project for 18 compost tunnels are finalized and the project will be ready in October 2004. The advantages of this new system for compost tunnels are even bigger than for the growing rooms as the hollow room between the ceiling of the tunnels and the roof of the building disappears. In the new system the ceiling of the tunnels and the roof of the building is one and the same sandwich panel. With this thicker panel you have no problems with the forming of condense, and the old dusty tunnel roof that may cause infections during the spawning process is history with the new flat roof tunnel system.”