Insulate attic stairs and increase energy efficiency

The roof of a house naturally decides to a large extent on the energy values ​​of the entire building. A potential flaw is an attic staircase. The insulation required by the Energy Saving Ordinance (EnEV) for the entire roof is often well below and costs heat and money.

The heat transfer coefficient (U-value)

The EnEV, valid since 2014, requires a heat transfer value (W) of no more than 0.24 per square meter (sqm) for the top floor to the loft. This so-called U-value is exceeded by bad or uninsulated attic stairs up to twenty times.

Even if the U-value is calculated on average over the entire ceiling area, the value of the projectile breakthrough can be reduced to 0.5 W / m² by expert insulation of the attic staircase. This will improve the overall insulation of the attic by up to ten percent, depending on the area.

Retrofit with and without disassembly

The isolation of a loft staircase can already be considered during installation or carried out subsequently in different ways. Both an already installed scissor staircase and an insertion ladder can be modified with or without disassembly.

In the variant without disassembly, a heat protection hood is placed on the walk-through. However, this creates a second opening flap to access the attic. The insulation value is slightly lower than with an insulation directly at the attic stairs.

For this purpose, the dismantling is required to apply an insulation board on the upwardly directed surface of the stair support plate. Alternatively, and because of the space available in some cases necessary, the complete flap can be replaced and replaced by an insulating board.

Surface insulation and joint tightness

In addition to the surface insulation, sealing the installation joints is crucial. The all-round joints should be sealed airtight. This can be achieved by a step bearing with glued elastic insulating tape. Prerequisite is a fitting close the attic stairs.

If you want to build a loft ladder yourself, overlapping rubber lips can create additional airstrip protection on the installation joints. To test the airtightness, the loft ladder can be tested with a candle. The flame should remain completely free of flickers near the joints with the flap closed.

Properties of insulating materials

As materials for insulating an attic stairs come several materials in question. Since condensation can also play a role depending on the structural conditions, the permeability to water vapor or the diffusibility must be selected accordingly:

  • Styrofoam and Styrodur are inexpensive, water vapor impermeable and flammable
  • Mineral wool is inexpensive, permeable and non-flammable
  • Wood fiber and mineral insulation panels are expensive, stable, permeable and conditionally flammable
  • Curing insulation foams are medium in price, impermeable to water vapor and flammable
  • Hemp and flax are medium-priced, permeable and less flammable

Tips & Tricks

You can choose insulating products and fabrics in different thermal conductivity groups. Ideally you use products of the groups 025 to 020. The lower the value, the better the insulating effect.