We have a 5/6-bedroom house in the west of Scotland, next to a loch, built 1850 and used as a holiday let.
In cooler times (that's most of the time) as soon as someone is in the house (particularly upstairs), condensation is apparent and with a full house, the amount of water running off the windows is astonishing. Because of the type of building, this is a bad sign as the air from inside will be escaping into the gap behind the lath and plaster lining and condensing on the stone walls leading to problems with the joists eventually.
The house is single glazed with 500mm thick dense stone walls. There is modest central heating, an open fire and a large multifuel stove (which provides part of the heat for the central heating).
The previous owners did an excellent(?) job of draughtproofing the windows.
I have read a bit (a lot) about MHRV and it seems to be the most efficient way to remove the excess moisture from indoor air. It is quite expensive to install and I'm only considering installing it for the upstairs as anything further would be too difficult. The people who sell/install these systems seem to think that it will do the job.
Now, I'm having doubts on two fronts. Firstly, west of Scotland environment is particularly damp, so the air drawn in will be close to 100%RH (at the cold outdoor temperature) whereas in a drier part of the world the incoming air would be drier. Will this adversely affect the performance. I see from humidity tables that air at 5 degrees 100%RH heated to 15 degrees will have a RH of 50%.
Secondly, all the performance information for MHRV systems relates to new builds, airtight, well-insulated houses. The house is anything but! Furthermore, I've seen it said that these systems perform much better in well-insulated airtight homes. I generally find these kind of things easy to understand but I don't really see why a system that is capable of changing the air in a building ever 90 minutes or so should be affected by the level of insulation or airtightness (OK, it won't work in a dutch barn, but in a dutch barn you have no need for any mechanical ventilation). Does anyone have experience of these things in old buildings or offer advice?
In cooler times (that's most of the time) as soon as someone is in the house (particularly upstairs), condensation is apparent and with a full house, the amount of water running off the windows is astonishing. Because of the type of building, this is a bad sign as the air from inside will be escaping into the gap behind the lath and plaster lining and condensing on the stone walls leading to problems with the joists eventually.
The house is single glazed with 500mm thick dense stone walls. There is modest central heating, an open fire and a large multifuel stove (which provides part of the heat for the central heating).
The previous owners did an excellent(?) job of draughtproofing the windows.
I have read a bit (a lot) about MHRV and it seems to be the most efficient way to remove the excess moisture from indoor air. It is quite expensive to install and I'm only considering installing it for the upstairs as anything further would be too difficult. The people who sell/install these systems seem to think that it will do the job.
Now, I'm having doubts on two fronts. Firstly, west of Scotland environment is particularly damp, so the air drawn in will be close to 100%RH (at the cold outdoor temperature) whereas in a drier part of the world the incoming air would be drier. Will this adversely affect the performance. I see from humidity tables that air at 5 degrees 100%RH heated to 15 degrees will have a RH of 50%.
Secondly, all the performance information for MHRV systems relates to new builds, airtight, well-insulated houses. The house is anything but! Furthermore, I've seen it said that these systems perform much better in well-insulated airtight homes. I generally find these kind of things easy to understand but I don't really see why a system that is capable of changing the air in a building ever 90 minutes or so should be affected by the level of insulation or airtightness (OK, it won't work in a dutch barn, but in a dutch barn you have no need for any mechanical ventilation). Does anyone have experience of these things in old buildings or offer advice?