Insulation top floor ceiling - what costs do you have to expect?

If you do not want the loft to be used as a living space, just keep an unheated storeroom, you do not need to insulate the roof itself. In this case, an insulation of the top floor ceiling is sufficient. What costs you have to expect for non-accessible and accessible floor slabs, and what differences there are for individual insulation types for the floor slab, you will find in our article.

prime example

As an example, we want to create a simple, non-walkable insulation on the top floor. The attic of our family house is 12 x 10 m in size, so it has an area of ​​120 m². We want to insulate the ceiling with a 200 mm thick insulating layer of mineral wool sheets (035) in one layer, which are laid on top of the ceiling.

total price2,947 euros
material2,256 euros
working hoursabout 15 hours

Tips & Tricks

Further details on the insulation carried out by us can be found in these specifications.


Please note that the quoted price example is just a sample. Your home may incur higher or lower prices for this service, depending on a variety of factors.


Floors can be insulated in very different ways. Most often, an insulation on the floor ceiling is performed, which can be either walkable or not accessible.

But there are other possibilities as well:

  • Thermal insulation under the floor (rare and usually expensive)
  • Thermal insulation layer in the form of a suspended ceiling and as
  • Thermal insulation layer between ceiling beams (in the case of wooden beam ceilings, usually additionally designed
  • between the floor joists, bedding can also be carried out from above or from below, for example with perlite.

By far the most commonly used option, however, is the insulation on the floor slab. It is also the least expensive and therefore comparatively cheapest. If an insulation between the ceiling beams, it is to be expected in many cases only with low additional costs.

Basic criteria for floor slab insulation

Walk-in / non-accessible insulation

In many cases it is advised to invest the slightly higher costs for a walkable insulation - this provides the roof space a variety of additional uses. The price differences are on the one hand in the area of ​​the insulating material (plate instead of insulating track) and on the other hand in the additional cost of a then absolutely necessary vapor barrier. Which costs this is, is shown in the following table (data from our sample example)

executionCeiling insulation railwayCeiling insulation platedifference
150 mm, 035 MW single layer17 - 25 EUR per m²30 - 40 EUR per m²13 - 15 EUR per m²
200 mm 035MW single layer22 - 30 EUR per m²38 - 54 EUR per m²16 - 24 EUR per m²
Vapor barrier (separating layer)

Vapor barriers can be designed differently, and consist of different materials. Most commonly PE film is used. With a material thickness of 0.25 mm, you have to reckon with costs between 1.50 - 2.50 EUR per m² (including laying and seam welding). The material price for this film is around 0.45 EUR per m². With a 0.5 mm thick film with separating layer, the costs are around 2.20 - 2.90 EUR per m², the material price is around 1 EUR per m². One possible alternative is aluminum composite films, which are significantly more expensive. Here you have to expect around 4 - 5 EUR per m², depending on the thickness of the film. The material price is then around 3 EUR per m².

Influence of the U-value on the costs

The lower the U-value of the floor slab should be, the higher the costs. Required by the EnEV is a heat transfer coefficient at the floor ceiling of 0.24 W / (m · K) - as can be considered a value of 0.20 W / (m · K), which corresponds to the requirements for a roof insulation in converted attic. The following table shows an example of the influence of the U-value to be achieved on the costs of a (non-walkable) roof insulation

  • Wooden beamed ceiling with top insulation
  • Insulation not accessible
  • Insulation boards polystyrene foam (EPS) 035 or PUR / PIR 025
  • Beam height 20 cm, beam width 8 cm, beam distance 60 cm
required U-value ceilingCost per m² ceilingCosts for thermal insulation on the upper side + intermediate beam insulation
0.20 W / (m · K) (recommended)85 - 115 EUR per m²85 - 115 EUR per m²
0.16 W / (m · K)95 - 135 EUR per m²95 - 135 EUR per m²
0.12 W / (m · K)115 - 165 EUR per m² * with PUR 025115 - 155 EUR per m²
less than 0.10 W / (m · K) (passive house)125 - 175 EUR per m² * with PUR 025145 - 195 EUR per m²

Note: Prices may vary significantly due to different bar dimensions and distances

Cost of possibly additional work required

In addition to the option for a walk-in instead of a non-passable separating layer, it may also be necessary to additionally carry out further work. If cavities are in the area of ​​the ceiling, they must be completely insulated with blow-in insulation. For this purpose, different materials are used, such as mineral wool granules.

Conservative factors

  • lower insulation requirements (low U-value of the ceiling construction)
  • no cavities
  • Use of less expensive insulation materials
  • Insulation in own contribution (self-installation)

Increasing factors

  • existing cavities (blow-in insulation required)
  • high U-values ​​of the ceiling (higher insulation required)
  • Desire for walk-in insulation
  • Use of expensive insulation materials

Saving opportunities through self-construction or personal contribution

The insulation of the top floor ceiling you can easily run as non-walkable insulation itself. You save about 5 - 8 EUR per m² of costs, if you can buy the insulation materials cheap but pay attention in the execution of a sufficient insulation thickness (calculation by a specialist) and on the fact that you absolutely avoid thermal bridges during installation. Also pay attention to existing cavities, which you must additionally insulate.


In many cases, subsidies can be claimed for the insulation of the upper storey ceiling. There are individual options for claiming the income tax return. More information about possible funding can be found in our general funding overview. Please note that not all subsidies or depreciation are always available for self-executed work.

Tips & Tricks

In any case, decide whether you want to expand your attic later. Even if you continue to use the rooms only as a (heated) storage room or storage room for the time being, it is more economical, equal to a roof insulation, e.g. to perform as intermediate buffer insulation.

Video Board: How to Beef Up Attic Insulation - This Old House