Hello everyone,
We recently purchased a house, and in a few weeks, the renovation and refurbishment work will begin. The house was built in 1957; the exterior walls are made of 24cm (10 inches) pumice concrete blocks (all floor slabs are reinforced concrete, and the basement walls and foundation are rammed concrete).
The previous owner partially insulated some of the exterior walls from the inside, sometimes very simply with plastered polystyrene panels, and sometimes with professionally installed wooden cladding including a vapor barrier between the wood and the wall (which we will probably keep for now). We understand that there is likely mold behind the polystyrene panels—but that’s a separate issue. 😉
We are currently wondering how to deal with these apparently very cold exterior walls in winter. From our perspective, there seem to be basically three options:
We remove the polystyrene insulation in any case, eliminate all mold (possibly also from the plaster),
1. and simply renovate without adding insulation. We’ll wait through the first winter and then see how the temperatures and comfort levels in the rooms are. At worst, we’ll have to heat a lot. However, the walls can breathe and avoid further mold growth (assuming proper ventilation 😉 ).
2. and add insulation on the inside in the places where the previous owner already added it, using built-up interior walls with a vapor barrier (there are prefabricated systems made of expanded clay aggregate, but these are expensive and complicated to install—and they reduce the room depth by about 8cm (3 inches)). But wouldn’t this prevent the walls from breathing?
3. and insulate the entire house from the outside. This would probably be the “best” solution, but unfortunately, it’s out of our budget.
Do you see any other options?
Sorry if this is a common dilemma, but we’re a bit overwhelmed and want to avoid making mistakes. Would it be advisable to consult an energy expert for an independent on-site assessment?
Thanks very much for all tips and opinions.
Best regards,
NFA
We recently purchased a house, and in a few weeks, the renovation and refurbishment work will begin. The house was built in 1957; the exterior walls are made of 24cm (10 inches) pumice concrete blocks (all floor slabs are reinforced concrete, and the basement walls and foundation are rammed concrete).
The previous owner partially insulated some of the exterior walls from the inside, sometimes very simply with plastered polystyrene panels, and sometimes with professionally installed wooden cladding including a vapor barrier between the wood and the wall (which we will probably keep for now). We understand that there is likely mold behind the polystyrene panels—but that’s a separate issue. 😉
We are currently wondering how to deal with these apparently very cold exterior walls in winter. From our perspective, there seem to be basically three options:
We remove the polystyrene insulation in any case, eliminate all mold (possibly also from the plaster),
1. and simply renovate without adding insulation. We’ll wait through the first winter and then see how the temperatures and comfort levels in the rooms are. At worst, we’ll have to heat a lot. However, the walls can breathe and avoid further mold growth (assuming proper ventilation 😉 ).
2. and add insulation on the inside in the places where the previous owner already added it, using built-up interior walls with a vapor barrier (there are prefabricated systems made of expanded clay aggregate, but these are expensive and complicated to install—and they reduce the room depth by about 8cm (3 inches)). But wouldn’t this prevent the walls from breathing?
3. and insulate the entire house from the outside. This would probably be the “best” solution, but unfortunately, it’s out of our budget.
Do you see any other options?
Sorry if this is a common dilemma, but we’re a bit overwhelmed and want to avoid making mistakes. Would it be advisable to consult an energy expert for an independent on-site assessment?
Thanks very much for all tips and opinions.
Best regards,
NFA
For the energy-efficient renovation of a building, a comprehensive renovation plan covering the entire building is necessary, which also integrates the heating/heating system. Partial insulation measures should be carefully evaluated because they carry the risk of increased condensation and mold growth in particularly cold spots (thermal bridges). Insulation already in place—especially interior insulation—must be checked for building physics consistency, particularly if it was installed as a DIY project and involves vapor retarders/vapor barriers. The latter always have flaws and thus leakage points.
If you want to insulate in sections, this is possible but only after a complete overall plan with clearly defined interfaces has been developed. Regarding your insulation options:
1.) Feasible, but not economical, as you may turn your house back into a construction site after 1–2 years. Walls do not breathe; rather, they absorb moisture sorptively to a limited extent and release it again into the indoor air. Nothing passes through the wall except thermal radiation. Mold results from insufficient or improper ventilation, inadequate building insulation, and insufficient room temperature (e.g., a cold bedroom) and is usually caused by user behavior.
2.) Not recommended due to building physics complexity. Interior insulation must be free of cavities, vapor-permeable, and capillary-active. Suitable materials are available today but must be installed professionally. Expanded clay is not among these.
3.) The best solution. Insulation is always applied on the cold side. Interior insulation is a last resort when structural conditions do not permit otherwise or when heritage conservation regulations prohibit exterior façade insulation.
I recommend working directly with a combined building energy consultant/architect who can develop an individual renovation plan tailored to your budget and family situation (moving in, DIY work, etc.). They can also advise you on potentially relevant funding programs from the KfW Bank or BAFA.
What I strongly advise against: 1.) spontaneous actions without a plan, 2.) acting without professional planning, 3.) proceeding based on uncoordinated contractor quotes without independent planning.
You can find regional building energy consultants for initial on-site advice through the dena list of energy efficiency experts.
If you want to insulate in sections, this is possible but only after a complete overall plan with clearly defined interfaces has been developed. Regarding your insulation options:
1.) Feasible, but not economical, as you may turn your house back into a construction site after 1–2 years. Walls do not breathe; rather, they absorb moisture sorptively to a limited extent and release it again into the indoor air. Nothing passes through the wall except thermal radiation. Mold results from insufficient or improper ventilation, inadequate building insulation, and insufficient room temperature (e.g., a cold bedroom) and is usually caused by user behavior.
2.) Not recommended due to building physics complexity. Interior insulation must be free of cavities, vapor-permeable, and capillary-active. Suitable materials are available today but must be installed professionally. Expanded clay is not among these.
3.) The best solution. Insulation is always applied on the cold side. Interior insulation is a last resort when structural conditions do not permit otherwise or when heritage conservation regulations prohibit exterior façade insulation.
I recommend working directly with a combined building energy consultant/architect who can develop an individual renovation plan tailored to your budget and family situation (moving in, DIY work, etc.). They can also advise you on potentially relevant funding programs from the KfW Bank or BAFA.
What I strongly advise against: 1.) spontaneous actions without a plan, 2.) acting without professional planning, 3.) proceeding based on uncoordinated contractor quotes without independent planning.
You can find regional building energy consultants for initial on-site advice through the dena list of energy efficiency experts.
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