we have underfloor heating in combination with a geothermal heat pump. Most likely the condensation would have been much better if there were radiators under the windows, but underfloor heating felt like a given in a small apartment to be able to furnish everywhere.S surfarn said:
You just get so irritated when these are windows that we got a quote on through the building trade. Then you would assume that what they suggest should be okay. They know where we live. Surely the windows are too poor (is the u-value what you should be looking at in this case?).M Myrkebab said:
We also live many on a cramped area. 5 people in 67 square meters (though with a gable roof, so there's relatively a lot of air in the apartment since at the highest point, it’s 3.30 in ceiling height). The children are not that old, 1, 3, and 6, so they probably don't release as much moisture as an adult, but still, there's certainly something to that! However, there is condensation even on days we have not been home.
this leads to many follow-up questions.
How harmful is it for the house to let it be like this for a while and then replace the windows when they've rotted enough? Can other parts of the construction be damaged by this?
if you would need to replace windows, is it possible to only change the window sashes (for example, to triple-glazed) and let the frame remain? Or is it likely that the frame is also too poor? It would be a much smaller intervention than replacing the whole windows with new salnings and insulation and all that jazz.
I have double-glazed windows with insulated glass manufactured in 2017, installed in 2018.
Under the windows where I haven't yet installed radiators (mainly the unfinished upper floor but also one on the ground floor), condensation forms periodically during the cold part of the year.
This is not a new phenomenon, many with older houses/windows encounter condensation problems inside when they remove the radiators under the windows and replace them with underfloor heating.
Underfloor heating seems to require triple-glazed windows of extra insulating quality to function perfectly.
I have FTX ventilation in my house.
Under the windows where I haven't yet installed radiators (mainly the unfinished upper floor but also one on the ground floor), condensation forms periodically during the cold part of the year.
This is not a new phenomenon, many with older houses/windows encounter condensation problems inside when they remove the radiators under the windows and replace them with underfloor heating.
Underfloor heating seems to require triple-glazed windows of extra insulating quality to function perfectly.
I have FTX ventilation in my house.
Sorry for nagging, but what kind of ventilation do you have? You need to measure the CO2 level in the air to check the ventilation. Too high CO2=poor ventilation=too much moisture. Do you have a proper vent channel to the kitchen fan? Or carbon filter? When so many are living in a small space, ventilation is especially important.M MissChico said:
I think the ventilation is called FTX. Above the kitchen fan, there's a whole box that manages the ventilation. If I understand correctly, it somehow reuses the heat to create new heat in the house? I don't feel like an expert in this, but it should be some kind of good system. There's no charcoal filter at least.S surfarn said:
In the garage (downstairs), we have a different system. And what I know is that those systems are not connected because they weren’t allowed to, as it can cause exhaust fumes to go up into the apartment.
We are looking into how we can measure the CO2 levels! It will probably involve buying a meter of some kind, but we have to sort out the different ones so we don't buy one that doesn't work well or gives misleading measurements.
Ok, you seem to have proper ventilation, which is good. But I still think it might not be quite enough. It would be interesting to see if you can keep it below 1000, or even better, 800 PPM, as well as a reasonable relative humidity.M MissChico said:
Do you know the U value of the windows? Are they energy-efficient glass?
Modern and more efficient FTX units with rotary heat exchangers recover much of the moisture. This is claimed to be good as indoor air often becomes too dry in winter.
FTX with plate heat exchangers, which were more common in the past, are better at drying the air, making the indoor air drier.
FTX with plate heat exchangers, which were more common in the past, are better at drying the air, making the indoor air drier.
As I wrote in post #2, you need to be aware of all the parameters before drawing any firm conclusions. I agree that the window type seems under-dimensioned for underfloor heating, but I don't think it can explain the severe condensation. The ventilation system doesn't seem like a likely cause either. However, I feel that the window type and the construction of the exterior walls seem questionable in a newly built house. I would like to know approximately where the house is located and what kind of house it is? Standard house, self-build, etc.
Today we had an inspector here who did various measurements. He checked, among other things, if there were thermal bridges at the windows/outer walls. What he could immediately determine was that the windows are too weak for where we live. The humidity in the house was 36%, which he considered normal/expected. However, the humidity at the windows was almost 60%, and he said that value stood out significantly.J justusandersson said:
We have now looked more closely at our windows and realized that they are definitely underdimensioned. When we bought the windows just over a year ago, they were called SP villa 2-glass insulated units. They have now changed the name of these windows to SP leisure 2-glass insulated units. So already in the name, you can now understand that they are worse. The U-value of these is 1.5, but since we have rather small windows, the U-value apparently becomes even worse (higher). Today, we received a list of just our windows, and the smallest have a U-value of almost 1.8.
In the quote we received when we chose windows, the U-value was not stated. We should, of course, have checked this, but there was so incredibly much going on at the time (with a newborn baby and construction and new jobs, etc.) that we never did. I think we simply trusted the building store, which provided us with three different quotes, that all three would at least withstand the climate where we live (Norrland).
The inspector also took measurements of the ventilation, and it was working optimally. The house had a negative pressure, which it should have (-2.2).
We will increase the ventilation further, to run on forced mode around the clock for two days to see if this makes any difference.
After that, you can think about how to proceed. I still think it's poor of the building store to give us a quote on a window that actually doesn't measure up. Need to ponder a bit on whether they can somehow be held responsible for remedying the situation? Compensate financially?
The house is a stick-built house. The plan was to build the garage on the plot first with an apartment above to have somewhere to live while the residential house was being renovated. Therefore, we made cheaper choices (e.g., when we chose the windows).
In a way, it is good that the situation became clearer, even if it has sad consequences. The construction trade lacks real knowledge in most respects. They cannot be trusted. It is completely clear that you need to replace the windows. Ask someone with real expertise first before you decide. There are more parameters than just the U-value. What I don't understand is how you got planning permission.
There are companies that can install additional insulated glass on the inside of existing frames. Could it be worth trying, maybe?
I would like to know what the room temperature is in the current space?
we usually have between 21 and 22 degrees. Yesterday we turned up the ventilation quite a bit, and then the problem almost disappeared. However, it's too early to draw a big conclusion from that as we need to see over time and temperature changes how it affects.J justusandersson said:
Try lowering to 20 degrees for a few days.