ETICS. Double Layer With Resol Foam Sheets: Double Keeps Warmer

With a double layer of Resol hard foam panels, it is now also possible to "retrofit" facades where previously there was not enough space for double layering with EPS or mineral wool.

Author: Susanne Sachsenmaier-Wahl | Photos: Baumit

There are many arguments in favor of doubling an existing thermal insulation composite system. Markus Haberland, ETICS product manager at Baumit, sums it up like this: “By doubling an existing ETICS, the insulation values can be increased. As a result, the energetic character of a building is adapted to the currently available values. In addition, there is no need to dismantle the old system and thus protect the environment.”The existing ETICS is not becoming useless, but continues to do its job. It only gets support from another "warming" layer over it. As a result, there are no demolition and disposal costs.

Space is often a problem when doubling with EPS or mineral wool. Roof overhangs become too scarce, the permitted land development is exceeded or the proportions of the building are disturbed.

Slim and powerful

Extremely slim insulation has been on the market for a good ten years, with which the same insulation values as with conventional insulation materials (EPS, mineral wool, etc.) can be achieved with less thickness. We are talking about resol foam.

Resol rigid foam (often also called phenolic resin foam) - unlike EPS - is not a petroleum product. “Bakelite is the first industrially manufactured plastic. The first light switches and telephone housings were made from this material,”explains Markus Haberland and adds:“It is a plastic based on phenols, which is produced without crude oil. The insulation board is manufactured in a similar way to EPS insulation: phenolic resin is inflated with the addition of blowing agents (pentane).”Then it is laminated on both sides with glass fleece. The finished insulation material has a closed structure with very small cells and a relatively high bulk density of 40 kg / m3. As a result, the material can only be poorly penetrated by heat and cold. In addition, the propellant gas trapped in the cells has an insulating effect.

Since the thermal conductivity of resol foam is only 0.022 W / (mK), the insulation layer can be around 30 percent less than that of EPS in order to achieve the same insulation value. "As an ETICS, the board can be used without restriction", Markus Haberland describes the areas of application. “But it is preferably used where the focus is on a lower insulation thickness. The masonry structure becomes leaner, which also saves on the elaboration of sheet metal protrusions, etc.”

Other advantages of phenolic resin

However, the low thermal conductivity or, conversely, the very good insulation effect are not the only thing that makes phenolic resin foam panels attractive. "Compared to the usual insulation materials made of polystyrene or rock wool, the CO2 footprint in the manufacture of phenolic resin foam panels can be up to half lower," explains Markus Haberland. “Combined with the high insulation performance with a smaller insulation thickness, less material is required, which is a plus point in ecological terms. The material is rot-proof and theoretically lasts for a long time if properly applied. Sustainability is there."

Resol rigid foam also performs well in terms of fire protection. ETICS systems with resol rigid foam are classified in building material class B1, ("flame retardant"). In contrast to EPS insulation facades, which are only flame-retardant if they have been previously treated with flame retardants, resol rigid foam reaches building material class B1 without these controversial additives. In addition, it does not drip when exposed to flame. No additional fire bolts are therefore required for ETICS systems with this insulation material.

Double layer with resol foam sheets

It is almost self-explanatory that phenolic foam sheets are ideal for doubling due to the properties mentioned. Since the beginning of May 2016, Baumit has had the first building inspectorate approval in Germany for the doubling of existing ETICS systems with resol foam insulation boards. And - Markus Haberland is particularly proud of this - the company has a unique position on the market: "To our knowledge, Baumit is currently the only manufacturer to offer a double system with resol foam boards on the market." With the new approval for the extremely slim insulation system doubling can also be carried out where there is no space for mineral wool or EPS.

What should you watch out for when doubling with Resol hard foam panels? “The old system must be glued or glued and dowelled to the surface. The stability and load-bearing capacity of the old system must be checked by a specialist,”says Markus Haberland. Baumit offers Resol rigid foam insulation boards in thicknesses between two and twenty centimeters. But for the doubling you can not choose from the range. “The total insulation thickness of the old and new systems must not exceed 200 millimeters. The possible thickness of the new system therefore depends on the thickness of the old system,”warns Markus Haberland. The new insulation may also be a maximum of 14 centimeters. But Haberland is certain:"By using the insulation material with the lower coefficient of thermal conductivity, a sufficient U-value is usually achieved with these specifications."

What to look out for

So far, only existing thermal insulation composite systems made of EPS panels may be revised. But "an expansion to other systems is being considered", Haberland lets us know.

That is how long the quality of the old insulation has on the fire behavior of the overall system. "The presence of a fire bolt results in the fire classification of the old system. With fire bars it is flame retardant, without it it is normally flammable,”explains Markus Haberland. Of course, the old system can be optimized in terms of fire protection. To achieve flame retardancy of the overall system, the additional fire bolts can be added to the old system.

The new panels are glued to the old insulation layer. The adhesive is applied over the entire area when doubling up, whereas it can be carried out with an initial insulation with phenolic resin sheets using the bead point method and only a contact area of 40 percent has to be guaranteed. Resol hard foam panels generally have to be dowelled in a statically relevant manner. Of course, this also applies to doubling. "It is anchored in the masonry through the old and new systems," says Markus Haberland. There is a decisive difference to EPS boards when processing the slim insulation boards: “Phenolic resin foam boards are fleece-laminated on the surface and therefore cannot be sanded. It is therefore important to ensure that the subsurface is level and that the panels are applied perpendicularly,”advises the product manager. With a doubling, this should be the smaller problem, since the old insulation is usually relatively flat.

A base profile should be installed at the bottom of the doubled system. After the reinforcement, the final coating is done. "Both mineral and paste-like finishing plasters can be applied as final coatings." Markus Haberland also gives the following tip: "The original scratching plaster is also suitable, with many advantages of a lower tendency to contamination and good durability."

More on doubling:

PraxisPlus

The Resit rigid foam sheet from Baumit is called "ResolTherm XS 022". The double system with the slim plate is known as "onTop XS 022".

Further information:

www.baumit.de

Markus Haberland, ETICS Product Manager at Baumit

Up to now, existing ETICS made of EPS panels could be revised. An expansion to other systems is being considered.