How do you insulate your attic ceiling

Insulate the top floor ceiling. This is how it works

A lot of heat is lost in winter via the top floor ceiling to the undeveloped roof space. Since warm air rises, insulation measures have a particularly lasting effect, especially in this area of ​​the building.

A calculation example

The comparison of an uninsulated with an insulated 20 cm thick reinforced concrete ceiling makes it clear which order of magnitude is involved. Without thermal insulation, the ceiling's energy loss is 32.3 liters of heating oil per square meter per year. With an area of ​​100 m2, this results in heating costs of 1,427.66 euros per year. If you take the same blanket and cover it with a 36 cm thick thermal insulation felt, the heating oil consumption of this area is reduced to around 1 l per m2 per year, the heating costs drop to 44.20 euros.


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Depending on the circumstances, insulation can be carried out using exposed ceiling, suspended ceiling or lower ceiling insulation. The variant of insulating on the floor slab is the most popular and can be done by the skilled do-it-yourselfer.

With what and how to insulate?

The first decision to be made: with what and how should it be insulated? Depending on whether the attic is to be walked on or even inhabited in the future, the insulation materials and types to be used differ: If the room under the roof is empty in the future and is no longer walked on, then simple, openly laid insulation mats or panels made of rock wool are sufficient , Glass wool, wood fiber or styrofoam. Roll out, done.

If your attic is to serve as unheated storage space, the insulation material used must be accessible, i.e. also pressure-resistant. Here, it is best to use Styrodur or PE, which are covered with chipboard or OSB panels, which then serve as a substructure for the pavement. The trade also offers ready-to-walk attic elements here. And this is how it works:

Step 1:

Prepare the substrate: The floor must be clean and dry. Even the smallest objects such as stones or splinters must be removed by vacuuming, sweeping and wiping, as they could damage the vapor barrier film.

2nd step:

Attaching the vapor barrier: First, cut the film into the required lengths with a cutter knife and always leave at least ten centimeters overhang for walls, plinths or pillars. Now stretch the film strips over the surface (attention: not too much tension!) And glue them to the edge areas with the special sealing adhesive. The individual strips should always overlap and be tightly connected with the adhesive tape.

3rd step:

Laying insulation material: Now take the panels or mats and lay them row by row. It is best to start in a back corner and work your way meter by meter to the other side of the room. With the foxtail, pieces that are too large for edges or corners can be easily cut and fitted.

4th step:

Laying chipboard or OSB boards: If the attic is to be walked on in the future, a pressure-resistant support is required on the insulation material. These panels are then laid floating and glued together in the groove.

What you need:

No do-it-yourself project without the necessary materials and, above all, the right tools. Here you can find at a glance what you need for the individual work steps.

  • Choice of insulation material
  • duct tape
  • Vapor barrier film plus suitable adhesive
  • Chipboard or OSB panels
  • Craft knife
  • Foxtail
  • Brooms & vacuum cleaners

Tip: These DIY instructions show you the workflow for your project in rough steps. Due to the complexity of the work, we recommend that inexperienced and inexperienced DIY enthusiasts hire a professional company. Pay attention to the observance of personal safety during the implementation, wear suitable protective clothing if necessary. Have the work described here carried out by specialists if you are not familiar with the materials, work processes and work rules.