ᐅ Getting Moisture Out of a New Build – How to Ventilate and Other Related Topics
Created on: 22 Nov 2021 18:10
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XxTankerxX
Hello everyone,
The shell of our house was recently completed. Our regional window supplier had a delay with a larger order, so we received our windows just 3 1/2 weeks after measuring—shortly after the roof structure was finished. In my opinion, this was almost too early, but I wasn’t given much choice since otherwise we wouldn’t have gotten them this year. Naturally, the house still contains a lot of residual moisture. The floors (especially in the basement) are now dry—or at least they look dry. However, many bricks (especially in the basement) are still dark-colored and damp. I’m also measuring a humidity level in the basement air of about 84%.
About the house: The basement is a waterproof concrete basement (WU-basement). The interior walls and all floors above ground level (ground floor and upper floor) were built with Poroton blocks.
Now to my main questions:
- What is the best way to ventilate? Currently, I have all basement windows tilted open. On the ground floor and upper floor, I have some windows (on opposite sides) open to create cross-ventilation. Is that sufficient?
- Following up on that: I still need to insulate the top floor ceiling with EPS035 (the insulation arrived today), and a waterproof membrane needs to be installed in the basement. When is the best time to do this, or how long should I wait before proceeding? I want to avoid trapping moisture underneath and causing mold in the end.
I’m interested in your opinions and how you handled similar situations during your build.
Kind regards,
XxTankerxX
The shell of our house was recently completed. Our regional window supplier had a delay with a larger order, so we received our windows just 3 1/2 weeks after measuring—shortly after the roof structure was finished. In my opinion, this was almost too early, but I wasn’t given much choice since otherwise we wouldn’t have gotten them this year. Naturally, the house still contains a lot of residual moisture. The floors (especially in the basement) are now dry—or at least they look dry. However, many bricks (especially in the basement) are still dark-colored and damp. I’m also measuring a humidity level in the basement air of about 84%.
About the house: The basement is a waterproof concrete basement (WU-basement). The interior walls and all floors above ground level (ground floor and upper floor) were built with Poroton blocks.
Now to my main questions:
- What is the best way to ventilate? Currently, I have all basement windows tilted open. On the ground floor and upper floor, I have some windows (on opposite sides) open to create cross-ventilation. Is that sufficient?
- Following up on that: I still need to insulate the top floor ceiling with EPS035 (the insulation arrived today), and a waterproof membrane needs to be installed in the basement. When is the best time to do this, or how long should I wait before proceeding? I want to avoid trapping moisture underneath and causing mold in the end.
I’m interested in your opinions and how you handled similar situations during your build.
Kind regards,
XxTankerxX
A
Alessandro23 Nov 2021 09:14I would still use a dehumidifier as an additional measure.
Is the hatch to the top floor ceiling/attic closed?
Is the hatch to the top floor ceiling/attic closed?
As mentioned before, during upcoming freezing temperatures it is best to fully open all windows (avoiding tilting windows, as this promotes mold growth; fresh air enters, but the moist indoor air cannot escape). At below-zero temperatures, water is drawn out of the brick and soil, freezes on the surface, and then evaporates again at suitable temperatures.
That is why it is recommended to let a shell construction dry out during winter rather than in summer.
Dehumidifiers will effectively dry the air, but they will not help with moisture in the soil and masonry.
That is why it is recommended to let a shell construction dry out during winter rather than in summer.
Dehumidifiers will effectively dry the air, but they will not help with moisture in the soil and masonry.
Bardamu schrieb:
Dehumidifiers will dry the air effectively, but they won’t help with moisture in the soil and walls.Of course they help, just like ventilation does. Soil and walls always release moisture into the indoor air. Where else would it go? The indoor air can only absorb moisture if the relative humidity is kept low; otherwise, the air becomes saturated. This is exactly what drying equipment (dehumidifiers/building dryers) is used for.
In winter, airing out by briefly opening windows works because cold outdoor air warms up inside the house. Warm air can hold more moisture, which means that simply by warming up outdoor air, its relative humidity decreases enough for the originally moist outdoor air to absorb more water. Without heating and with open windows, nothing happens. The same applies to permanently tilted windows: the air doesn’t warm up enough and cannot absorb additional moisture.
(In addition to heating and dehumidifiers, fans also help improve air circulation.)
Tassimat schrieb:
Of course that helps, just like ventilation does.
Floors and walls always release moisture into the indoor air. Where else would it go? Indoor air can only absorb moisture if the relative humidity is fairly low; otherwise, the air is saturated. This is of course achieved with construction dryers. That is true, but it only helps if there is moisture in the air or on surfaces. This moisture then evaporates.
However, if you want to dry out the masonry and screed completely, you can forget it.
The long exposure of a shell construction without windows and doors over the winter has proven itself over many decades for a reason. Otherwise, they would have said, just put in a wood stove and continue after four weeks.
You can see it with all the Town & Country houses—after five years they are all moldy.
And what would be so bad if the original poster installs the windows next year? Nothing much happens during the winter anyway.
Hello,
if I understand the original poster correctly, the screed and interior plaster have not been installed yet. In other words, the main amounts of moisture are still to come. The moisture in the wall bricks is negligible. With screed and interior plaster, several cubic meters of water will enter the building. That’s when things get interesting.
Until then, I would ventilate and, if necessary, set up a construction dryer. These devices consume about 0.5 to 1 kW per hour, so they aren’t cheap to run. Also, someone needs to empty the water containers.
However, as mentioned, it only makes limited sense to invest a lot of effort at this stage.
Best regards,
Andreas
if I understand the original poster correctly, the screed and interior plaster have not been installed yet. In other words, the main amounts of moisture are still to come. The moisture in the wall bricks is negligible. With screed and interior plaster, several cubic meters of water will enter the building. That’s when things get interesting.
Until then, I would ventilate and, if necessary, set up a construction dryer. These devices consume about 0.5 to 1 kW per hour, so they aren’t cheap to run. Also, someone needs to empty the water containers.
However, as mentioned, it only makes limited sense to invest a lot of effort at this stage.
Best regards,
Andreas