Do-it-yourself insulation of the attic floor

Recommendation points

• Warming options
• Advantages of mineral wool insulation
• Materials and tools for work
• Work order
• A few tips

Insulation of the attic floor can be done in various ways using different materials. We propose to consider a fairly common option for insulating an attic floor using mineral wool mats. This method allows you to achieve good results with minimal effort..

Warming options

Among the options for insulating attic floors are such as insulation with expanded polystyrene and foam plates, various options for using foam and aerated concrete, insulation based on clay mortar with the addition of sawdust or straw, and, of course, one of the most common methods using mineral wool boards and mats. Mats will be called roll material of a given thickness. The use of mineral wool mats gives a number of advantages when performing work.

Advantages of mineral wool insulation

The use of mineral wool mats allows:

• reduce the number of joints compared to using plates;
• perform work using a single layer stacking;
• significantly reduce the load on the attic floor.

In addition, mineral wool as such:

• has one of the best thermal conductivity indicators;
• can serve as additional sound insulation;
• when used on horizontal planes, in the absence of loads, it lasts up to 35 years;
• has good vapor permeability.

Materials and tools for work

To carry out the work on insulation of the attic floor, you will need:

• rolled mineral wool mats;
• vapor barrier film;
• double-sided construction tape;
• long blade knife.

Work order

Let’s start with a general cleaning of the attic floor. Although the installation of the mats does not require any special surface preparation, it will still be necessary to remove the debris. Then a vapor barrier is laid on the surface of the floor. It should be laid with an overlap of 15–20 centimeters, with the side with the inscriptions facing you, or, in their absence, with the rough side down. This ensures the removal of air moisture from under the floor to the thermal insulation layer, and then into the space under the roof for its weathering. In places where the vapor barrier layers overlap, it must be glued with double-sided tape. It should also be borne in mind that part of the vapor barrier needs to be admitted onto the walls of the attic or onto a strapping beam (Mauerlat) for the entire thickness of the insulation.

After that, they begin to lay the insulation. Laying is carried out from the far wall of the attic, going to the exit. The mats should only be laid with slight interference. Thus, almost complete absence of the effect of the joints on the quality of thermal insulation is ensured. The abutment to the walls of the attic should also be tight. The mats should be unpacked at the place of installation. Pay attention to how the roll is packed in the package and place it so that after unpacking it is convenient to roll the roll towards you. After unrolling the roll, it should be aligned with the wall or the previous roll, then lightly pressed along its entire length to each other. The last section of the attic surface in width may not contain a whole roll. Then, having measured the width of this section, you should, without unpacking the roll, cut off a part of the mat in width with a knife with a long blade. Keep in mind that you need to cut off two to three centimeters more than the measured value.

Having completed this work, for the length of the mat roll, another layer of vapor barrier should be spread over the insulation layer, which is laid in the same way as the first layer. It is necessary to fill the edge of the upper layer of the vapor barrier over the edge of the lower layer, completely wrapping the end of the insulation, adjacent to the wall of the attic (or Mauerlat), around the entire perimeter of the insulation. Then you can lay the next row of slabs along the length of the attic.

Do not be afraid to navigate the already paved insulation. Modern materials for insulating attic floors are able to restore volume and shape.

A few tips

Do not make insulation less than 100 mm thick. Smaller layers of mineral wool mats can only be used with a special calculation. When performing work in your attic, you will not save much, and you will not be able to achieve the desired result. However, the use of a layer of more than 150 mm in the absence of calculations can lead to the fact that moisture vapor will not be removed from the thickness of the insulation, and this will lead to a decrease in its effectiveness. True, this is true only in cases where concrete slabs are not used as an attic floor. In this case, the insulation can be carried out without the lower layer of vapor barrier, and the thickness of the insulation can be chosen at your own discretion.

Decide for yourself whether you will continue to operate the attic or not. In the first case, it will be necessary to provide for either a continuous covering of mineral wool, or the device of passages from boards along the surface of the insulation. In the second case, there is no need for additional flooring. If you ever have to go through the insulation, then there is nothing to worry about.

Pay special attention to the reliability of gluing the joints of the upper layer of the vapor barrier, otherwise it will be periodically exposed by drafts.

And further. Look at your thermal insulation from time to time, the timely elimination of such things as the opening of the upper layer of the vapor barrier, water leakage through the roof, will ensure the long-term operation of the completed insulation.