Wet Spray Cellulose Dry Time
kennebecwoodworks
| Posted in Green Building Techniques on
I’m building a house in Maine, we recently did a wet spray cellulose installation in the wall cavities, its a 2×6 wall with zip sheathing and 2 inches of poly iso on the exterior. We installed about 2 weeks ago and the cellulose is still very damp. I was told to drywall to prevent the cellulose from absorbing more moisture. I’m concerned about possible mold in the damp dark wall cavities. Any thoughts?
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Replies
Summers are tough for moisture. I never lay hardwood in this type of weather. Bad timing. Mechanical drying next or fans or both or wait it out for dry weather.
Frame in the warmer months, get the roofs on before low sun angles and finish in the cooler dryer months.
Mark,
Although it sounds counterintuitive, the advice to go ahead and install drywall may make sense. To read what cellulose expert Bill Hulstrunk has to say about the issue, see How to Install Cellulose Insulation.
In that article, Hulstrunk notes, "The only times we have only had problems are when we waited a long time before installing the drywall. Now that buildings are significantly tighter than they used to be, the construction moisture loads in these buildings tend to be greater.
"We recommend waiting 24 hours before hanging the drywall. After that, the surface of the cellulose is dry. It isn’t all dried out, but if we leave it for a longer time, the construction moisture in the building can migrate into the cellulose. If it remains uncovered for a month, the construction moisture can make the material very wet. It can end up with a greater moisture content than when it is sprayed.
"If I get a call that a spray job won’t dry, the next thing the caller usually says is, ‘I’ve been waiting a month.’ But we like to see the sheetrock on there after 24 hours, because the sheetrock actually slows down the moisture migration from the indoor air into the cellulose.
"The cellulose wants to dry out, and it always dries out eventually. The idea that the cellulose in a wall could stay wet and not dry out is not correct."
I don't like the idea of drywalling over a wet wall assembly, for two reasons. Here is southeast Wisconsin, we typically use a lot of wood trim in our homes, wide casings and base, crown, chair, wall panels, etc. When we build a home during wet periods, or next to a lake, the high moisture content in the studs and framing can wreak havoc with 1) the drywall and 2)the wood trim. As the wall assembly dries out and shrinks over the course of the first winter, nail and screw pops will rear their ugly heads (pun intended), drywall joints in the corners will crack, and later, the tightly fit wood joints will also separate as the home dries out over the winter. Maybe this is less of an issue in drier parts of the country where drywall returns are the norm and less trim is used.
If my primary drywall subcontractor knew that the cellulose was wet inside the cavities, he would flat out refuse to install the drywall unless I signed off on it (which I wouldn't do).
I haven't used wet sprayed cellulose yet, but based on the concerns above, I think I would bring in lots of fans and industrial strength dehumidifiers to dry out the assembly before I would install drywall.