Effective insulation for an attic

Hello forum,

We have a house built in 1955. The roof is still from 1955, but it does not actually need to be renewed. Under the roof, there is an attic that is dry and serves as a storage room for, among other things, clothing. The roof is insulated with insulation between the rafters. There are only 2 small dormer windows about the size of DIN A3.

- In winter, I will stuff insulation wool in front of the roof window shafts to insulate them.

- The attic floor is already partially covered with Styrodur boards to insulate the attic against the living spaces. Does it make sense to insulate the entire attic floor? The effort would be about 300 euros and one day of work (mainly clearing out).

- We have a hatch with a pull-down ladder to the attic with gaps about 5 mm wide. Does it make sense to seal such gaps? How can I do that?

Thanks in advance for the help!

Hello Hausmeister72,

Hello forum, - The floor of the attic is already partially covered with Styrodur panels to insulate the attic further against the living spaces. Does it make sense to fully insulate the floor of the attic?

Basically, it is necessary to insulate the ceiling of the top floor in unheated attics. Otherwise, the heat losses would be enormous.

Non-water vapor-permeable insulation materials such as Styrofoam and Styrodur, in my opinion, have no place in top-floor ceiling insulation: the moisture rising from the living spaces below condenses on the underside of the panels and cannot escape from this construction. Over time, your beams will rot. A continuous vapor barrier installed on the warm side—that is, at the ceiling of the living spaces—and a vapor-permeable insulation of the top-floor ceiling provide a remedy.

There is also the possibility, with sufficiently strong insulation (e.g., using mineral perlite or clay), to forgo the vapor barrier. Then the moisture escapes freely upwards through the unheated attic. However, a precise dew point calculation should be performed for this. A few walking boards are sufficient if you do not intend to cover everything with planks or thick tongue-and-groove flooring.