Friday 26 February 2021  

Refurbishment of pitched roofs

When we decide to refurbish a roof, regardless of the reasons why, it is almost obligatory to replace or upgrade its thermal insulation. The roof can be refurbished either by replacing all the layers completely, or it can be adapted only from the inside or only from the outside.
We can notice that something is wrong with the roof, already during the first winter or the first summer, wihout needing to control the level of fuel consumption. Thermal bridges can be seen on a pitch roof covered with snow, but in summer or in winter thermal bridges can be noticed due to the amount of the delivered energy for cooling or heating. As the pitch roof represents a large surface in contact with the outside temperature, the quality of the roof, the so-called fifth façade, plays a decisive role in providing a comfortable living space in the attic.

Symptoms and possible reasons for inappropriately insulated roof:

1.   Hot in summer, cold in winter

  • Thermal insulation layer is too thin
  • Vapour barrier foil is applied on the outside, thus keeping the moisture within the construction and causing higher thermal conductivity of the construction elements.
  • Vapour barrier layer  (closely fitted boards, chipboards...) is applied on the outside. Moisture is kept within the construction, and is damaging it, and at the same tim reducing the efficiency of thermal insulation.
  • Water vapour permeable foil is applied on the inside, contacts between vapour barrier elements may not be sealed, or the foil might have been damaged during installation or intentionally punctured during the installation of services. Air circulation increases the heat flow.

2.   In windy weather the air temperature changes relatively quickly

  • The outside wind-protection foil is not installed.
  • The outside wind-protection foil is not sealed.
  • Partially vapour permeable membrane (e.g. roof cardboard) is laid only between rafters
  • Vapour retardant or vapour barrier (the lower foil) is not laid, or is not sealed.

The  next step is taking the decision to refurbish the roof
If we want complete refurbishment, then the rules that apply to new buildings, should be followed. If we want to refurbish the roof from one side only, we need to adapt to the existing situation. Here are some suggestions what steps need to be taken in case of upgrading or refurbishing the roof.

Internal or external remedial work?
Our decision largely depends on the state of the roofing. If it needs to be replaced, the installation of thermal insulation will definitely be carried out from the outside, but at the same time it is useful to check the quality of the entire roof construction.

If the roofing does not need to be replaced, and the roof construction is made of wood, it is better to carry out the work from the inside. In this way we can affect the balancing of water vapour permeability of the roof construction from the inside. Another advantage is that our work does not depend on the weather, and the installation can proceed gradually. If we use FIBRANxps ETICS  GF or BT   boards, the installation is carried out without additional subconstruction.

Refurbishment of pitch roof from the inside
The roof is additionally insulated from the inside with thermal insulation boards FIBRANxps ETICS  GF or BT , using ETICS façade. The boards are fixed onto the existing facings or directly over the rafters, in case we first wish to remove the existing cladding. The boards are fixed with anchors, covered with façade adhesive mortar, in which a façade mesh is placed, and then covered with an additional layer of adhesive mortar. In this way about 3mm protective layer is formed, and then levelled out with plasterputty and painted over. Joints between thermally insulated surface and other construction elements (inner walls, pillars) are filled with permanent elastic putty. Before plastering it is recommended to reinforce the joints, in order to avoid the forming of visible cracks.

Refurbishment of pitch roof from the outside
If thermal insulation is added from the outside, we first need to check the airtightness of the internal vapour barrier (internal foil).

Tiles, battens and secondary roofing are removed first. If necessary, additional flexible thermal insulation (e.g. wool insulation) is fitted in the space between the rafters. FIBRANxps MAESTRO boards are laid over the rafters, and then gradually covered with secondary roofing (water vapour permeable foil), and fixed with counter battens to ensure the ventilation air path.  Tiling battens are fixed next, and then tiles are laid on top. By ensuring perfect continuousventilation along the complete surface, an exceptionally effective thermal performance of the roof is achieved.

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