Drying out construction moisture, vapor barrier or not?

[Marcus Hennix]

In a few days, we will have the roof of our weatherproof cottage insulated with loose fill. The roof is sealed with plastic but not yet the walls where we currently have 45 mm insulation (145 mm will be added before the vapor barrier). I have measured the moisture in the sill/joists and at most it was 17-18%, and I was considering whether it would be possible to turn on the heat and dehumidifier for a few weeks at this stage, or is it best to finish insulating and plastic the walls before turning on the heat?

 

[jonaserik]

Remove the moisture first, if you add heat, the moisture will increase significantly, better just use a dehumidifier then.

 

[Marcus Hennix]

Get rid of the moisture first; if you add heat, the moisture will increase a lot, so it's best to just use a dehumidifier

You mean renting a sorption dehumidifier and let it run for a few weeks?

 

[jonaserik]

Yep, then you get the moisture down to a reasonable level, renting TJA, there are cheap ones in the stores that work, some just have a tray underneath that needs to be emptied, others have it so you can connect a hose for drainage.

 

[Daniel 109]

Is it a wet concrete slab or where do you mean the moisture is coming from?

 

[Marcus Hennix]

Is it a wet concrete slab or where do you think the moisture is coming from?

It is the current surface moisture in the structure, there is no concrete slab but a joist on an insulated crawl space (hybrid foundation)

 

[Marcus Hennix]

Yep, then you can get the humidity to a reasonable level. Renting, WELL, there are cheap ones at department stores that work. Some just have a tray underneath that needs to be emptied, others can be connected to a hose for drainage

I have a condensing dehumidifier, but it's not effective below 10 degrees.. desiccant dehumidifiers work in colder temperatures, but they tend to be much more expensive.

 

[Daniel 109]

No moisture is added when you heat. The moisture will be redistributed so that it becomes dry on the inside and more humid further out in the insulation before the moisture is driven out. So you can heat out the moisture.

 

[Marcus Hennix]

Then no moisture is added when you heat. The moisture will be redistributed so that it becomes dry on the inside and more humid further out in the insulation before the moisture is driven out. So you can heat out the moisture.

Ok! And there's no risk that it condenses on the inside of the windbreaker, etc.?