adding insulation to the facade, how is the indoor climate affected

[RoP]

The house's rendered facade is coming loose, has long cracks, and should be addressed. The framework is horizontal log and standing plank. From a thermal perspective, it would be good to add about 5 cm of insulation and then replaster. Additionally, the facade system would counteract cracking due to the house's movement. BUT how will the indoor climate be affected? We have natural ventilation via the chimney (which is cold, as we have a heat pump). Will the house "breathe" worse? Could the wooden walls be damaged by the additional insulation in the long term, due to poorer moisture migration? Does anyone know more about this?

 

[Kalle_h]

The moisture migration will obviously be worse if you put up a denser facade, as the air is generally more moisture-laden indoors than outdoors, especially in winter. However, don’t you have quite a strong cold draft in the chimney during winter if it’s open and cold? I assume you were thinking of putting a whole sheet outside the house, like foam plastic, and then plastering against it? On more modern houses, there have been problems on the plasterboard when air penetrates to the exterior plasterboard and precipitates water. In your case, maybe the facade should be set "freely" outside the old one, but then you lose much of the insulation value... At our company, we have just added extra insulation to a log cabin from the inside, being careful that the inner wall is free from the logs, with studs and insulation, then a vapor barrier was placed inside the insulation, but you have to compensate for this increased tightness with proper ventilation, so we increased the number of fresh air vents. Heat (and moisture) also travels upwards, so the roof will always be most exposed, and it’s even more important not to be too tight there, so the vapor can travel through the materials.

How were you planning to build it up?

//ingenjörn

 

[Gabbe1]

the air is generally more humid indoors than outdoors, especially in winter.

Is this really true? I thought it was the opposite when we talk about relative humidity.

However, don't you have a rather strong cold draft in the chimney during the winter if it's open and cold?

Normally, there shouldn't be a cold draft through the chimney, on the contrary, it's the heart of the natural ventilation and creates an upward draft of warm indoor air.

Heat (and moisture) also travels upwards, so the ceiling will always be the most exposed; there it's even more important not to be too tight, so the vapor can migrate through the materials.

Here, too, I thought it was the opposite, that it was most important to have completely diffusion-tight roofs to prevent moisture from penetrating into the attic.

Have I misunderstood your post perhaps?

 

[RoP]

The option I've settled on is to mount a mineral wool board on the old plaster. Then the board is plastered with an open plaster, i.e., no plastic paint or the like. I've understood that mineral wool is preferable to cell plastic in my case. As for the draft, it is not significantly large. I must say that I don't completely understand how natural ventilation works. Gabbe's explanation seems reasonable, though. But... you seem to be disagreeing there, right?

 

[Gabbe1]

Here you can read about how a FUNCTIONING natural ventilation system behaves:
http://www.energimyndigheten.se/sv/...g-i-hemmet/Ventilation/Sjalvdragsventilation/

But sure, there can be cold drafts in abnormal cases, but then the natural ventilation system isn't working as intended.

 

[Kalle_h]

Yes, I think we are misunderstanding each other a bit. I probably expressed myself a bit clumsily, but you can (in such winters) encounter "setbacks" in ventilation systems of the natural draft type, and then you are likely to get overpressure. The percentage of humidity in the indoor air is lower, but the air indoors has a greater capacity to hold moisture and receives additional moisture from machines, people, and other things inside the house. No problems until it cools down again, and if it then gets pushed out in the wrong place, it will inevitably deposit the moisture.