spray on cellouse

building a new home in northern iowa with 2 - 6 walls, used celluose spray on insulation on walls,contractor has plastic and drywall installed on inside and osb board on outside .contractor has started to install siding on and discovered one piece of osb board warped then replacing finding out cellouse still partialy wet approx 2 inches along osb board. Is this common? any thoughts?

Wall spray cellulose has a very low moisture content. This moisture that you are experiencing on one outer wall area must be getting there from some other source. The cellulose insulation is not the moisture issue.

Was the drywall installed at least 24 hours after the insulation was applied?

thanks for response,yes no drywall installed for one week no siding on 7 / 16 osb board with permable house wrap,no heat in house, had over 10 inches of rain in 4 week period sept 22 thru oct ,very little sun . covered front porch no rain on, is as wet as any place like 3.5 inches damp, insulation sticks to osb board. your thoughts? tia

I have found, at least in the Chicago area (because of our climate) that spray cellulose is not a good product. It absorbs moisture and supports mod growth.

I prefer a spray foam type insulation. With spray foam, there is an air / vapor and liquid water barrier on both sides of the insulation space. Plus, spray foam has a higher R value per inch.

Spray cellulose also does not provide the type of col air infiltration barrier that is called for with the new energy efficiency ratings.

Hope this helps;

I’ve had installed wet blown cellulose insulation in many houses here in northern Michigan. What you have experienced led me to not use the product this time of year. It wouldn’t dry quick enough. I, and others around here, learned to use it only in the summer months where it had good conditions to dry out before closing up the walls.

I highly concur with Larry, Whenever Installing cellulose in cold weather, Give it a week WITH HEAT before covering, or dont use it at all. Im also not a fan of plastic underneath the drywall, it does not allow the wall to breathe, and traps any moisture in the wall. Whenever you have 2 vapor barriers, you have a container. With your tyvek on the outside, you could keep that wall wet for a long time.

On a side note, Yes Foam insulation rocks! Man is it expensive.

I concurr, do not use wet spray cellulose this time of year unless there is a substantial amount of temporary heat to dry out the walls.

Here is a description of how it happens.
Adding moisture to the wall cavity of homes is a touchy subject. One that the fiberglass industry likes to promote as dangerous to structural and human health. The truth is a bad application can be dangerous and ineffective. An inexperienced applicator can introduce an unsafe level of water into a wall system. Mold, mildew and even rot can result. On the other hand, skilled applicators achieve an effective and safe balance of moisture-to-fiber and provide a superb insulation system. A target of approximately 30% moisture content by weight is appropriate. Freshly sprayed cellulose should feel damp, but you should not be able to squeeze water out of a handful if you tried.

As the sprayed cellulose insulation dries it stiffens and is very resistant to settling. Sprayed walls should be left open until the Moisture Content (MC) of the fiber drops below 25%. This normally requires a 2-day drying out period depending on the climatic conditions. The installer should check the MC using a moisture meter to assure the fiber is dry before authorizing a close-in of the walls.

Sprayed cellulose is not all roses. An entire house can be insulated in one day, but it will be a very messy day. The inside of the house will resemble a combination of mid-winter blizzard and coastal fog. Windows, doors, and electrical boxes must be protected with plastic sheeting and tape prior to installation. Blowing fibers irritate the respiratory tract and eyes so a protective mask and goggles are a must. A sea of waste fiber must be vacuumed and shoveled on an ongoing basis. Spraying damp cellulose during freezing conditions is rough on equipment and drying time can drag to a crawl. And while priced competitively, it will cost a few hundred dollars more than fiberglass batt insulation. But the upside is worthy.
The best solution is to go with SPF, the cost around here is about $1.00 a board ft.
and to achieve the rating of a moisture barrier, you need at least 2-1/2". Very expensive material.

I disagree with Marcel.

Please not that I am describing conditions in my area (Chicago) and not Maine

House wrap provides a LIQUID water barrier, from the OUTSIDE, and allows any moisture in the sheathing to “breath” out (a one way movement).

I prefer spray foam because it provides and air / water / vapor barrier both on the interior of the sheathing and just behind the drywall.

No movement, of heat, air, water or water vapor.

Hope this helps;

Will, I thought that is what I was saying, I prefer SPF, I was only describing how sprayed wet cellulose gets accomplished and how it can turn into problems using that product this time of year.

Quite right, Marcel. I was referring to the previous post and got confused.

To often, builders believe that the house wrap wil stop everything.

Sorry for the misunderstanding.

No problem Will, and I would like to mention that the alternative to wet sprayed cellulose is to use a netting on the ceiling or walls and then spraying dry cellulose, the netting holds everything in place and does not contribute moisture trapped in the assembly.
Most contractors get impatient with the wet cellulose and cover it up prematurely.

Most contractors get impatient with the wet cellulose and cover it up prematurely. -Marcel

So true. Happens all the time. Not all Insulation contractors do a good job of informing the contractors of the importance of this step, and a week long waiting period idea doesn’t go over well.


Read the above from 1994 for a bit of a primer on the change in building science understanding of moisture movement, air and vapour barriers. Note especially the section detailing the wet applied cellulose in Calgary where its -30C (-22F) today…that’s a real area to test for condensation.