4 ms·

> Do you have some documentation on the “moisture through heat transfer” issue? Warm/er air can hold more moisture than cold/cooler air. If part of the house i

> Do you have some documentation on the “moisture through heat transfer” issue? Warm/er air can hold more moisture than cold/cooler air. If part of the house is warm, and you happen to cook and/or shower in it, it will have a high moisture content. But water vapour diffuses through-out an enclosure. So that water in a gaseous phase will equally spread everywhere (eventually). When it reaches the uninsulated part/s of the structure, the air is colder and so can't hold as much moisture leading to condensation. Get lots of condensation, and you have an environment that is suitable for mold growth (which can then release spores in the air and mess up indoor air quality (IQA)). Not to mention that water is a universal solvent, and so will turn your structure (stone, masonry, concrete, wood) to mush over time. The place of condensation will most likely be a surface that is a large temperature change: so in the winter your inside is warm, and your uninsulated outside walls are cold.

marvin 4y ago
Adding to this -- climates that have cold winters and a tradition for building well-insulated homes have detailed construction customs for how to deal with this. Today, it's generally solved by having an airtight sheet (plastic) between the insulation and the inner wall. Sometimes placed inside the insulation. This ensures a temperature gradient that will not cause condensation inside the house. You'll generally put a sheet that's porous but not airtight outside the insulation, to reduce heat loss due to convection and also provide an extra layer of defense against moisture damage due to wind-blown rain. This technique necessitates good ventilation (often powered) if it's used throughout the entire house. This is to avoid saturating the inside air with humidity due to breathing and other activity, itself leading to the condensation you're trying to avoid. It can sometimes be just on e.g. floors and ceilings. Then, the rest of the structure might still be leaky enough that mostly passive ventilation will do the trick. Older houses handle the problem by just being so leaky that condensation won't be a problem.
- illiac786 4y ago
  I still don’t get why there would be *more* moisture on the uninsulated inner wall compared to before insulating 3 out of 4 walls.
  - bluGill 4y ago
    Because you add the same amount of moisture (showers, cooking, breathing), and it needs to get out before it's was evenly over all 4 walls, now only one. Your total indoor humidity is going to go up because there is less taking care of it. That said, insulation is still the right answer, but it ain't cheap. OP should probably tear down that beautiful old house for something more modern.
  - qubitcoder 4y ago
    Most people know that hot air rises. It's helpful to think of airflow in terms of energy (temperature is a measure of the average kinetic energy of air molecules). Hotter air has more energy and thus will naturally "flow" towards cooler areas with less energy until equilibrium is reached. In this example, the higher temperature air holds more moisture. That moisture will be carried along and dispersed towards the cooler wall, where it could condensate.
    - illiac786 4y ago
      I do see your point, you believe the air near the uninsulated wall will have even more moisture because it’s now the only cold wall out of 4 walls. So all the moisture goes there instead of being split in 4. But a wall will stop condensating water when reaching a certain degree of humidity. So I’m not entirely convinced one can simply divide the amount of humidity in the air by the amount of uninsulated walls (or sqm).
      - throw0101a 4y ago
        > I do see your point, you believe the air near the uninsulated wall will have even more moisture because it’s now the only cold wall out of 4 walls. So all the moisture goes there instead of being split in 4. The air will not have more moisture, but rather all the moisture problems will be towards/on the uninsulated wall. > But a wall will stop condensating water when reaching a certain degree of humidity. So I’m not entirely convinced one can simply divide the amount of humidity in the air by the amount of uninsulated walls (or sqm). Condensation will never stop on a cold wall until all the moisture in the air is removed. If you boil a pot of water the air will fill with moisture, and the entire house will have a high humidity. But because one particular wall is cold because of a lack of insulation the condensation (water going from vapour to liquid phase) will be concentrated on that particular wall. The condensation will continue to occur as long as you continue to add moisture to the air via cooking and bathing (hot showers, baths).

marvin 4y ago

Adding to this -- climates that have cold winters and a tradition for building well-insulated homes have detailed construction customs for how to deal with this. Today, it's generally solved by having an airtight sheet (plastic) between the insulation and the inner wall. Sometimes placed inside the insulation. This ensures a temperature gradient that will not cause condensation inside the house. You'll generally put a sheet that's porous but not airtight outside the insulation, to reduce heat loss due to convection and also provide an extra layer of defense against moisture damage due to wind-blown rain. This technique necessitates good ventilation (often powered) if it's used throughout the entire house. This is to avoid saturating the inside air with humidity due to breathing and other activity, itself leading to the condensation you're trying to avoid. It can sometimes be just on e.g. floors and ceilings. Then, the rest of the structure might still be leaky enough that mostly passive ventilation will do the trick. Older houses handle the problem by just being so leaky that condensation won't be a problem.

illiac786 4y ago
I still don’t get why there would be *more* moisture on the uninsulated inner wall compared to before insulating 3 out of 4 walls.
- bluGill 4y ago
  Because you add the same amount of moisture (showers, cooking, breathing), and it needs to get out before it's was evenly over all 4 walls, now only one. Your total indoor humidity is going to go up because there is less taking care of it. That said, insulation is still the right answer, but it ain't cheap. OP should probably tear down that beautiful old house for something more modern.
- qubitcoder 4y ago
  Most people know that hot air rises. It's helpful to think of airflow in terms of energy (temperature is a measure of the average kinetic energy of air molecules). Hotter air has more energy and thus will naturally "flow" towards cooler areas with less energy until equilibrium is reached. In this example, the higher temperature air holds more moisture. That moisture will be carried along and dispersed towards the cooler wall, where it could condensate.
  - illiac786 4y ago
    I do see your point, you believe the air near the uninsulated wall will have even more moisture because it’s now the only cold wall out of 4 walls. So all the moisture goes there instead of being split in 4. But a wall will stop condensating water when reaching a certain degree of humidity. So I’m not entirely convinced one can simply divide the amount of humidity in the air by the amount of uninsulated walls (or sqm).
    - throw0101a 4y ago
      > I do see your point, you believe the air near the uninsulated wall will have even more moisture because it’s now the only cold wall out of 4 walls. So all the moisture goes there instead of being split in 4. The air will not have more moisture, but rather all the moisture problems will be towards/on the uninsulated wall. > But a wall will stop condensating water when reaching a certain degree of humidity. So I’m not entirely convinced one can simply divide the amount of humidity in the air by the amount of uninsulated walls (or sqm). Condensation will never stop on a cold wall until all the moisture in the air is removed. If you boil a pot of water the air will fill with moisture, and the entire house will have a high humidity. But because one particular wall is cold because of a lack of insulation the condensation (water going from vapour to liquid phase) will be concentrated on that particular wall. The condensation will continue to occur as long as you continue to add moisture to the air via cooking and bathing (hot showers, baths).