An acquaintance decided to insulate the house from the inside: he explained to him how to do it NOT NECESSARY

Due to the insulation, you can save a lot on heating, but only if you do everything right.

I recently went to a friend's house, and he had half a room full of bales with insulation. Time allows and he decided to insulate the coldest room of the house from the inside with mineral wool in winter. Moreover, it is "reliable" to insulate, so that it turns from the coldest to the hottest. It's good that I managed to warn him about the possible consequences.

Why mineral wool is not used for indoor insulation

Friends, disclaimer right off the bat. I understand that the topic of insulation is complex and very ungrateful to discuss. There are different opinions, technologies, approaches, and worst of all - there are many myths. I do not presume to convince someone, but I will try to save you from mistakes that I myself once made.

Warming of premises must be done from the outside - from the side of the street. This is the only correct option. Everything else is an attempt to get around the laws of physics.

In winter, the temperature inside the wall “crosses zero”. The temperature of the outer edge of the wall is negative, the inner one is positive, and somewhere inside the wall it is zero. This is the so-called dew point. To keep the house warm and free of dampness, the dew point should be as close to the outer edge of the wall as possible.

With external insulation with mineral wool, the walls retain their vapor permeability - they breathe. In this case, the dew point is closer to the outer surface of the wall (as it should be).

With internal insulation with mineral wool, the dew point moves closer to the inner part of the wall. Condensation, dampness, fungus, etc. appear.

That is why mineral wool is used only for external wall insulation. If you want to understand this issue in more detail, I recommend the video (Vasily talks in detail and with simple examples about the dew point in the walls):

Is it possible to insulate the walls from the inside with foam plastic?

At the beginning, I outlined my opinion about the insulation inside the building - INSULATION SHOULD BE ONLY OUTSIDE. Nevertheless, we always find ways to circumvent the laws of physics - internal insulation with expanded polystyrene is one of such methods. The balcony itself was so insulated from the inside, because there was no other way around the ninth floor.

When we use expanded polystyrene instead of mineral wool indoors, the dew point goes inside the insulation (this, of course, depends on its thickness). We use the material that is vapor-tight, so condensation does not appear inside. There are two serious drawbacks to this insulation method:

• The walls are no longer vapor permeable.
• The problem of condensation formation may appear along the perimeter of the insulation (at the abutment to the ceiling and floor).

Think about finishing right away

For insulation, extruded polystyrene foam - EPS (PENOPLEX) is often used. Its glossy surface has virtually no adhesion. If decorative plaster is applied to it, it will hold for a while, but then it will still fall off from the base.

Sometimes on sale you can find EPS with a rough surface - prepared for the application of decorative plaster. If such insulation is not available, we independently increase the adhesion of a smooth surface - with an emery cloth, a spatula or an ordinary hacksaw.

On non-extruded polystyrene foam (white), decorative plaster adheres well without preliminary preparation. But it has slightly worse thermal insulation properties.

I do not recognize the options of insulation on the frame, when the layer of insulation is "cut" by bars. Yes, then you can screw drywall to the bars and make any finishing option on it. But a lot of cold bridges appear in the insulation.

But what to do with the mineral wool that you have already bought?

My acquaintance has bought too much mineral wool. There is nowhere to put it - you need to use it. I strongly advised him to wait for spring and insulate the walls outside. But in my practice there was a precedent for internal wall insulation with mineral wool, which showed itself well. Perhaps some of you will come in handy.

We mount a plasterboard frame on the wall. We pack each insulation mat in an airtight plastic bag and install a bullet behind the wall profiles. The attachment points for the suspensions are foamed. This method of installation is rather out of desperation.

Learn from other people's mistakes and allow as little of your own as possible. If the material was helpful, put a "thumbs up" 👍 and subscribe to the channel.