The U-value of a loft ladder arises from several variables

Of central importance in a loft ladder is the heat transfer coefficient, which is also known as U-value. Since the "hole" in the floor slab is a potential weak point in the overall insulation of a house, the best possible U value should be sought. Not only the flap must be considered.

Energy Saving Ordinance (EnEV)

If you would like to install a loft ladder, you will usually construct a passageway in a flat insulated floor slab. The Energy Saving Ordinance (EnEV) in the latest version of 2014 requires a U-value of at most 0.24 on the entire storey ceiling. If the attic stairs have a higher U-value, the rest of the surface insulation must balance the difference.

Separate stipulations in the EnEV for attic stairs do not exist. In general, the U-values ​​for normal windows are used as a guide. The maximum value is set to 1.4 for skylights. These U-value reach or fall below simply uninsulated attic stairs with wooden flaps of at least three centimeters in thickness.

U-value spreads

The U-value specifications of the manufacturers usually relate only to the flap or hatch area. Well insulated panels achieve U-values ​​of about 0.7. However, this insulation value expresses only a part of the actual insulation of the attic stairs. A "true" U-value also includes the fodder box, the joints and the complete construction.

A crucial function is the sealing of the attic stairs. Improper sealing can massively affect the overall U value, leading to deterioration of up to 3.0 and above.

Frame and joints

When insulating a loft staircase any voids must be filled in the frame with insulation. A particular weak point are the joint exits. After inserting a Dämmzopfes the insulation material should be distributed horizontally and over the entire surface on the top strips of the frame to achieve a perfect airtightness.

For floor stairs, a U-value of 0.7 to 0.8 is desirable and feasible. Brand manufacturers offer fully tested floor stairs kits that are offered at a higher price. The investment is worthwhile because of the associated energy savings.

Tips & Tricks

If you have a loft staircase installed, you can attach the copy of the invoice or order confirmation to your energy recovery claim.

Video Board: Loft Conversion Plans