Hello everyone,
I’m new here and would like to ask you something:
We recently bought a house built in 1977 and want to start renovating.
The facade is not insulated, but the interior side of the exterior walls is covered with 2 cm (1 inch) of polystyrene foam and drywall. This measure was originally planned by the architect and is documented in the original building description. After 40 years, there are no signs of mold or moisture in or on the walls. Now we wonder: should we leave it all as is, or would it be better to remove it?
Additionally, we want to install new electrical wiring, so we will have to chase grooves into the panels. Is it generally okay to do that? Afterwards, can we simply fill the grooves with plaster? Would it be advisable or possible to install a new drywall panel over that?
Thank you very much in advance.
I’m new here and would like to ask you something:
We recently bought a house built in 1977 and want to start renovating.
The facade is not insulated, but the interior side of the exterior walls is covered with 2 cm (1 inch) of polystyrene foam and drywall. This measure was originally planned by the architect and is documented in the original building description. After 40 years, there are no signs of mold or moisture in or on the walls. Now we wonder: should we leave it all as is, or would it be better to remove it?
Additionally, we want to install new electrical wiring, so we will have to chase grooves into the panels. Is it generally okay to do that? Afterwards, can we simply fill the grooves with plaster? Would it be advisable or possible to install a new drywall panel over that?
Thank you very much in advance.
Hello "BoBeLe".
2cm (1 inch) of polystyrene as interior insulation. I could hardly believe my eyes.
While interior insulation is not necessarily complex from a building physics perspective, you need to know what you are doing. For interior insulation to be effective, among other things, the insulation must be sufficiently thick. But 2 cm (1 inch)? That is never functional, even with a rough estimate.
The surface temperature of the wall relative to the outside temperature provides an indication of the approximate temperature distribution through the wall cross-section. The thickness of the insulation must be adjusted accordingly, along with a vapor retarder (which is usually applied as a brushable seal in interior insulation cases).
Let me put it this way:
The 2 cm (1 inch) thickness of the insulation probably had little effect. Except that it may have shifted the dew point inside the room. That is why there is no mold, because moisture did not condense on a building component.
Cutting grooves into the board and applying gypsum plaster falls into the same category as the installation of the 2 cm (1 inch) insulation layer:
With all due respect, that is poor workmanship.
Either you have interior insulation planned and installed by someone who truly understands the subject, or you will face unpleasant surprises.
Without meaning to offend you: My guess is that you might be overwhelmed by this topic.
At this point, I intentionally will not give any advice, because when it comes to "half measures + interior insulation," it often causes more damage than benefits!
------------------------
KlaRa
2cm (1 inch) of polystyrene as interior insulation. I could hardly believe my eyes.
While interior insulation is not necessarily complex from a building physics perspective, you need to know what you are doing. For interior insulation to be effective, among other things, the insulation must be sufficiently thick. But 2 cm (1 inch)? That is never functional, even with a rough estimate.
The surface temperature of the wall relative to the outside temperature provides an indication of the approximate temperature distribution through the wall cross-section. The thickness of the insulation must be adjusted accordingly, along with a vapor retarder (which is usually applied as a brushable seal in interior insulation cases).
Let me put it this way:
The 2 cm (1 inch) thickness of the insulation probably had little effect. Except that it may have shifted the dew point inside the room. That is why there is no mold, because moisture did not condense on a building component.
Cutting grooves into the board and applying gypsum plaster falls into the same category as the installation of the 2 cm (1 inch) insulation layer:
With all due respect, that is poor workmanship.
Either you have interior insulation planned and installed by someone who truly understands the subject, or you will face unpleasant surprises.
Without meaning to offend you: My guess is that you might be overwhelmed by this topic.
At this point, I intentionally will not give any advice, because when it comes to "half measures + interior insulation," it often causes more damage than benefits!
------------------------
KlaRa
If the house was granted building approval before November 1, 1977, there was only one requirement for minimum thermal insulation according to DIN 4108 from 1952. Starting from November 1, 1977, the first thermal insulation regulation defined the thermal insulation values for heat-transferring external building components. In the first case, the architect may have acted more proactively within the possibilities available at that time, or in the second case, fulfilled the requirements of the first thermal insulation regulation with interior insulation.
Without detailed knowledge of the building conditions, construction methods, and the planned renovation or conversion measures, it is not possible to provide a qualified statement on energy-related building refurbishment. Which insulation and heating concept is appropriate or feasible in your case can only be decided in the context of the entire building. Uncoordinated individual measures and spontaneous decisions without a professionally sound background must be avoided to prevent building damage.
Interior insulation is particularly complex in terms of building physics. What is currently applied to your wall does not correspond to a functionally sound building-physical structure. Interior insulation must either be completely vapor-tight—practically impossible under actual building conditions—or vapor-permeable, installed without cavities, and capable of capillary drying from the inside.
The materials used so far meet neither of these requirements. They may appear harmless at first glance; this becomes clearer when the interior insulation is partially removed. It is very likely that condensation and mold have formed over the years in the transition zone between the polystyrene and the cold interior surface of the external wall.
I would recommend completely removing this interior insulation, as chasing electrical wiring into it is also inadvisable. A new insulation concept should only be developed with an architect or structural engineer experienced in older buildings and renovations, who can also advise you on material choices and component assemblies, especially if you plan to carry out the work yourself. I advise against so-called energy consultants who are unable to consider such a project holistically.
Without detailed knowledge of the building conditions, construction methods, and the planned renovation or conversion measures, it is not possible to provide a qualified statement on energy-related building refurbishment. Which insulation and heating concept is appropriate or feasible in your case can only be decided in the context of the entire building. Uncoordinated individual measures and spontaneous decisions without a professionally sound background must be avoided to prevent building damage.
Interior insulation is particularly complex in terms of building physics. What is currently applied to your wall does not correspond to a functionally sound building-physical structure. Interior insulation must either be completely vapor-tight—practically impossible under actual building conditions—or vapor-permeable, installed without cavities, and capable of capillary drying from the inside.
The materials used so far meet neither of these requirements. They may appear harmless at first glance; this becomes clearer when the interior insulation is partially removed. It is very likely that condensation and mold have formed over the years in the transition zone between the polystyrene and the cold interior surface of the external wall.
I would recommend completely removing this interior insulation, as chasing electrical wiring into it is also inadvisable. A new insulation concept should only be developed with an architect or structural engineer experienced in older buildings and renovations, who can also advise you on material choices and component assemblies, especially if you plan to carry out the work yourself. I advise against so-called energy consultants who are unable to consider such a project holistically.
N
nightdancer21 Jan 2017 10:14BoBeLe schrieb:
The facade is not insulated, but the exterior walls are covered on the inside with 2cm (1 inch) of polystyrene and drywall. I am currently renovating with an architect and an energy consultant. You can forget about that—the insulation effect is really minimal. The important thing is that you have to separate both materials: drywall in mixed construction waste and polystyrene separately. Proper disposal of the latter is quite expensive these days. Although with 2cm (1 inch) it doesn’t amount to much.
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