The fact is that the insulation requirements of a house are constantly being tightened up. The government (and municipalities) individually is working hard on this. There are various systems to better insulate a house. Consider, for example, double glazing, refilling the cavity wall or an insulating retention wall on the inside of the house. However, these are solutions that only bring a limited improvement. And as the requirements are getting stricter, it is almost impossible to achieve with these solutions mentioned. However, there is another system that can provide a higher insulation value and can be tailored to the increasingly strict requirements. This system is the external wall insulation system, in which the outside of the facade is insulated.
History of BGI
Exterior wall insulation has been on the market for a while. The first external wall insulation system (BGI) was carried out in Germany in 1957. BGI only became interesting in the Netherlands after the first oil crisis of 1973. Production cut by OPEC led to an oil shortage, so the government decided to restrict energy. One of the measures was the car-free Sunday. But there was also more interest in alternative energy and more attention was paid to energy consumption. The government then decided to take a good look at insulating houses. As a result, the first BGI system was applied in the Netherlands in 1975.
The BGI system (general)
The BGI system is characterized by the gluing of (mainly) EPS plates on a stone or wooden construction. Depending on the condition of the substrate, additional plugs may have to be used. These plugs are an additional mechanical attachment of the EPS plates to the structural surface. EPS plates can be supplied in various thicknesses (on average from 20 to 400 mm). Depending on the thermal resistance of the construction, a thickness of EPS plate can be selected. When the plates have been applied to the structural substrate, the plates can be provided with an adhesive and reinforcement layer. Reinforcing fabric is therefore included in this. When this adhesive and reinforcement layer has dried sufficiently, a finishing plaster can be used. This can be a cement-bound or a synthetic resin-bound plaster. Afterwards, a paint system is recommended, but is not an obligation for most manufacturers. The advantage of a paint system is that the facade remains beautiful for longer and the durability of the facade is considerably extended.
The big advantage of a BGI system is that the space in the home is preserved. In addition, the home does not have to be evacuated for the work and the end user can simply stay in his or her home. In addition, a BGI system not only provides warmth in the winter, but also ensures a cool indoor climate in the summer. This reduces the use of any air conditioning system.
What thickness of EPS sheet do I need?
The thicker the insulation, the better the house will be insulated. But to determine what thickness is needed, it is important to make a calculation. The so-called Rc calculation (heat resistance construction) shows how much a construction can insulate. The current requirement for the Rc value is currently 3.5 m2 K / W. The government plans to increase the requirement for the Rc value to 5.0 m2 K / W.
Rd value (heat resistance material)
To properly insulate a house, the current construction must be considered. All parts of a structure have a Rd value. An Rd value is the heat resistance of a material. The unit used for this is lamda (λ). All these materials set up (including heat transfer resistances and corrections) form an Rc value.
To give an idea of what only one sheet of EPS can do in terms of heat resistance, five different thicknesses of EPS sheets are included below (with a lamda value of 0.040 W / (mK).
- 20 mm EPS gives a Rd value of 0.50 W / (mK)
- 50 mm EPS gives a Rd value of 1.25 W / (mK)
- 100 mm EPS gives a Rd value of 2.50 W / (mK)
- 160 mm EPS gives a Rd value of 4.00 W / (mK)
- 200 mm EPS gives a Rd value of 5.00 W / (mK)
Rc value (heat resistance construction)
Because the government plans to increase the requirement for the Rc value to 5.0 m2 K / W, it is advisable to take this stricter requirement into account. Most manufacturers have an Rc calculation program on their website. This makes it easy to make the Rc calculation by entering the desired data.
Detailing
BGI systems have not built up a very good reputation, but this is not due to the systems. With a BGI system it is very important that the details of the manufacturer are adhered to. When deviated from, various consequences can have a negative effect on the BGI system. Consider, for example, the following details.
- Roof overhang of at least 30 mm in relation to the finished BGI system.
- Perform water hammer / window sill with a minimum overhang of 30 mm in relation to the finished BGI system.
- The use of compriband for water-retaining connections.
- The use of anti-drumming tape for aluminum water hammer and roof overhangs.
- The correct thicknesses of the adhesive and reinforcement layer, but also of the finishing layer.
- Applying an appropriate paint system, depending on the type of finishing plaster.
- Applying the insulation plates in bond.
- The flagging application of the insulation plates at the location of facade openings such as window frames.
These are just a few of the points of attention for details in BGI systems. The manufacturer of a chosen system can provide you with more information. NPR 3924 (guidelines for exterior plasterwork) also includes various points for attention for BGI systems.