The refurbishing of well-functioning inverted roofs constructed a few decades ago has today become necessary in order to achieve energy efficiency. How can a roof such as this be refurbished cost efficiently? RAVATHERM Hungary Kft. offers a solution to this problem by performing the least work possible and retaining the impeccable heat insulation.
The roof, as part of the building structure, plays a decisive role in the energy balance of our buildings. Up to one quarter of total heat may leak through an inadequately insulated flat roof. The formerly installed heat insulation of 6, 8 or 10 centimeters no longer corresponds to the demands of our age. Sooner or later, these roofs need to be made much more effective. RAVATHERM XPS makes it possible to install extra heat insulation as a second layer while retaining the existing heat insulation.
During refurbishment, the first step always consists of examining whether the existing layers can be retained. During the exploration required for this, each layer needs to be closely examined, and if possible, their technical parameters checked. Due to the advantages of the reversed layer structure, these roofs are typically still in good condition after 30 to 40 years, and layers can be removed and reinstalled easily and without damage. When examining them, it’s best to concentrate on the two main components of the roof besides the support structure: the water insulation and the heat insulation. Critical locations of water insulation include wall joints, along dilatations and edges, as well as around the roof drains. When examining the heat insulation, its solidity and moisture content need to be checked. Even closed-cell polystyrene foams may absorb moisture in a continuously damp environment – especially if the layer structure was not installed professionally or if water is not drained from the roof due to lack of maintenance. A few percentages per volume of water in the boards does not yet cause a significant change in their heat insulation capabilities. The extent of the change is typically not more than 4 to 8 %, and manufacturers have taken this into account when specifying the design values. If the boards are suspiciously heavy, it’s best to have them examined.
Theoretical layer structure and rules during the two-layer refurbishment of inverted roofs (from the outside to the inside).
- Gravel load (in case the roof is used, additional cover or vegetation)
- Waterproof film (vapor penetrable impermeable film installed with 15 cm overlaps)
- RAVATHERM XPS closed-cell polystyrene foam heat insulation
- Existing closed-cell polystyrene foam heat insulation (if its thickness is less than the thickness of the RAVATHERM XPS to be subsequently installed, the new heat insulation needs to be installed as the bottom layer.)
- Water insulation (repaired or refurbished as necessary) with an appropriate tilt and implemented on a solid base
The economic benefits of two-layer refurbishing of inverted flat roofs
- The existing heat insulation leads to continued energy saving without any new investment
- Significant waste disposal costs can be saved
- • The low operating/maintenance cost of the roof does not change
The Refurbishment Process
During the refurbishment of the roof, damaged or possibly blistered water insulation needs to be removed and replaced with new insulation. Once the surface of the water insulation is completely flawless, the heat insulation boards can be placed directly onto them. The installation principles of the inverted roof need to be observed during placement. If possible, the heat insulation should be placed in a joint pattern, and the next layer also shifted a bit when placed. Do not forget the waterproof separating film at the top of the second layer and the placement of the appropriate load. Depending on the method of use, the load layer may be gravel, clay aggregate, or a concrete slab cover placed on supports.
Please note that the flat roof may even be covered with vegetation during refurbishment. A green roof is a multiple environmentally friendly solution. Vegetation helps take load off the drainage system, binds some of the dust, decreases warming up in the summer, and also has a positive influence on the city micro climate if sufficiently large.
RAVATHERM Hungary Kft. provides help in the refurbishment of formerly installed inverted roofs and the upgrading of energy efficiency by providing technical consultancy, assistance in condition assessment as necessary, and the RAVATHERM XPS 300 SL product which offers consistent high quality and reliability.