Hello,
Over the turn of the year 2016/17, our L-shaped bungalow was built using sand-lime brick construction. External wall insulation (EWI) was applied, I believe, in November 2016. Inside, gypsum plaster was used, with underfloor heating installed beneath a cement screed. During the last four weeks before moving in (in January 2017), two dehumidifiers were used. The drying progress was said to be good enough that the floor moisture measurement gave the green light for our glued vinyl flooring. We moved in mid-February 2017.
Yesterday, the inspector came. Not without reason. There are condensation issues on an exterior wall in the bedroom and in the utility room. On average, the house has an absolute humidity of 9.5–11.5 g/kg of air. Our inexpensive hygrometers distributed throughout the house showed mostly 55–60% relative humidity in March but have risen noticeably since mid-April, reaching up to 75% in the bedroom. His measurements indicated that this is very likely due to residual construction moisture (the report is still pending). This could also explain why our vinyl flooring has started to lift again *grumble*.
In short: it’s my house, and I want to avoid further problems as quickly as possible. At the moment, I don’t care who is at fault here (whether we should have moved in later or ventilated better… that’s not the point here). So far, we have only aired the house by opening windows for cross-ventilation once a day. I’m not sure yet if twice a day is feasible. That’s why I considered setting up another dehumidifier now in addition to ventilating. Whether it helps, I’ll only find out afterwards. My question is: is it better to use two smaller units (each 10–15 L/day) or one larger one (50 L/day)? It’s also a matter of cost. The smaller ones have the advantage that I can place them distributed around the house but have only a very small condensate tank and have to hope the automatic shutoff works properly. For the large one, I found a model with an integrated condensate pump – it could run continuously. But I suppose proper air circulation in the house would be missing then, right? Does anyone have advice on which option I should choose?
Best regards
PS: I’m not sure about the category placement here in the forum, so please feel free to move this if needed. Thanks
Over the turn of the year 2016/17, our L-shaped bungalow was built using sand-lime brick construction. External wall insulation (EWI) was applied, I believe, in November 2016. Inside, gypsum plaster was used, with underfloor heating installed beneath a cement screed. During the last four weeks before moving in (in January 2017), two dehumidifiers were used. The drying progress was said to be good enough that the floor moisture measurement gave the green light for our glued vinyl flooring. We moved in mid-February 2017.
Yesterday, the inspector came. Not without reason. There are condensation issues on an exterior wall in the bedroom and in the utility room. On average, the house has an absolute humidity of 9.5–11.5 g/kg of air. Our inexpensive hygrometers distributed throughout the house showed mostly 55–60% relative humidity in March but have risen noticeably since mid-April, reaching up to 75% in the bedroom. His measurements indicated that this is very likely due to residual construction moisture (the report is still pending). This could also explain why our vinyl flooring has started to lift again *grumble*.
In short: it’s my house, and I want to avoid further problems as quickly as possible. At the moment, I don’t care who is at fault here (whether we should have moved in later or ventilated better… that’s not the point here). So far, we have only aired the house by opening windows for cross-ventilation once a day. I’m not sure yet if twice a day is feasible. That’s why I considered setting up another dehumidifier now in addition to ventilating. Whether it helps, I’ll only find out afterwards. My question is: is it better to use two smaller units (each 10–15 L/day) or one larger one (50 L/day)? It’s also a matter of cost. The smaller ones have the advantage that I can place them distributed around the house but have only a very small condensate tank and have to hope the automatic shutoff works properly. For the large one, I found a model with an integrated condensate pump – it could run continuously. But I suppose proper air circulation in the house would be missing then, right? Does anyone have advice on which option I should choose?
Best regards
PS: I’m not sure about the category placement here in the forum, so please feel free to move this if needed. Thanks
The drinking water connection does not necessarily have to be insulated; it might be considered good practice, but nobody in this construction area has done it. And as I mentioned, seeing how wet the insulation of the brine pipe is, the same would happen here—the condensation would just continue and then drip freely at the bottom. It seems like efforts are really needed to reduce the humidity in the air. Even in March, at 21°C (70°F) and 60% relative humidity, the exposed water pipes were sweating heavily. I can’t even imagine what’s happening with the cold water pipes under the floor heating.
As for air exchange, I confirmed it myself because I took care of ventilating once daily in addition to running dehumidifiers during the screed drying. Otherwise, nobody would have managed it. I do appreciate and agree that pointing out certain standards and saying "there are regulations and it has to be done this way," or asking “you’re building a turnkey home, so why are you dealing with this?” is valid, but in the end, things are as they are. Arguing doesn’t help me now because I want to prevent long-term problems already.
Due to the lower room temperature, the expert advised me to keep the bedroom closed, so a second dehumidifier might not be a bad idea after all. I’ll see what the market prices look like.
Also, can anyone comment on whether, in practice, masonry drying after moving in can still be (significantly) sped up with this method? If it can take 3–4 years otherwise, I suspect that the plaster allows very little diffusion, so while the dehumidifier regulates moisture in the room temporarily, it may only have a marginal effect on the masonry itself.
As for air exchange, I confirmed it myself because I took care of ventilating once daily in addition to running dehumidifiers during the screed drying. Otherwise, nobody would have managed it. I do appreciate and agree that pointing out certain standards and saying "there are regulations and it has to be done this way," or asking “you’re building a turnkey home, so why are you dealing with this?” is valid, but in the end, things are as they are. Arguing doesn’t help me now because I want to prevent long-term problems already.
Due to the lower room temperature, the expert advised me to keep the bedroom closed, so a second dehumidifier might not be a bad idea after all. I’ll see what the market prices look like.
Also, can anyone comment on whether, in practice, masonry drying after moving in can still be (significantly) sped up with this method? If it can take 3–4 years otherwise, I suspect that the plaster allows very little diffusion, so while the dehumidifier regulates moisture in the room temporarily, it may only have a marginal effect on the masonry itself.
But you deliberately decided against a mechanical ventilation system with heat recovery... so you should be aware that simply airing out the house once a day won’t be enough for the first 2–3 years.
I really can only shake my head about this because avoiding such a system means an extra daily effort.
Maybe someone could link this thread to the current discussions about mechanical ventilation systems – unfortunately, it’s not possible with Tapatalk.
Best regards, Yvonne
I really can only shake my head about this because avoiding such a system means an extra daily effort.
Maybe someone could link this thread to the current discussions about mechanical ventilation systems – unfortunately, it’s not possible with Tapatalk.
Best regards, Yvonne
Hello,
I have a quick question regarding controlled ventilation for living spaces:
Can I use our controlled ventilation system (which will be commissioned next week) to dry the screed to about 1.8% CM moisture content?
Or would it be better to use a dehumidifier in this case?
Best regards, Barossi
I have a quick question regarding controlled ventilation for living spaces:
Can I use our controlled ventilation system (which will be commissioned next week) to dry the screed to about 1.8% CM moisture content?
Or would it be better to use a dehumidifier in this case?
Best regards, Barossi
Barossi schrieb:
Hello,
I have a quick question regarding mechanical ventilation with heat recovery:
Can I use our mechanical ventilation system (to be commissioned next week) to help dry the screed at around 1.8% CM moisture content?
Or is it better to use a dehumidifier for this?
Best regards, BarossiNo. Use a construction dryer (dehumidifier), as it also extracts moisture from walls and floors. I don’t think a mechanical ventilation system can achieve this.
Regards, Yvonne
EveundGerd5 May 2017 22:49I agree with the previous commenter. Use the construction dehumidifier. Efficient and quick.
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