Replies

1. 
   Frank | Jul 14, 2010 01:30pm | #1

   Seattle Weather: http://forecast.weather.gov/MapClick.php?lat=47.60431120244565&lon=-122.32589721679687&site=sew&smap=1&unit=0&lg=en&FcstType=text

2. GBA Editor
   Martin Holladay | Jul 14, 2010 02:07pm | #2

   Frank,
   The answer to the question, "How long does it take damp-spray cellulose to dry?" is, of course, "It depends." Cellulose dries faster if the air is warm and the relative humidity is low.

   Here's an online resource: Spray Applied Cellulose and Moisture Facts from National Fiber, a cellulose manufacturer. According to the document, "National Fiber recommends 24 hours before cover."

   Your cellulose will continue to dry through the plywood sheathing and interior gypsum drywall after the stud cavities are enclosed. Don't install interior polyethylene or vinyl wallpaper.

3. 
   Christopher Briley | Jul 14, 2010 03:25pm | #3

   It will not be completely dry. I had a house where we did a moist applied cellulose installation (7" cavity) we let it dry for a week with as much heat as we could put in the house without resorting to salamander propane heaters (don't use those). It was surface dry, but if you plunged your hand into it, it was moist (about 21%) we had no choice, we put up the sheetrock and the builder fought humidity issues though spring (condensation on windows, trim and doors always on the move) but in the end, after a good summer, it all worked out though it took about a year for the house to settle in. There were also some tweeks to the ERV (which we changed to an HRV, by swapping a filter). And then humidity has been well under control since. We decided we would never do that again for a winter install but we have numerous times in the summer.

   Let it dry for as long as you possibly can. Postpone sheet rock finishing as long as you can. If you want you could ask the installer to come back with his moisture meter and tell you what the moisture content is before you sheet rock. That puts a little burden on them to tell you its okay. I have this item in my house specs, though it is usually overlooked (or ignored) by the "common" builders.

   You're probably going to be fine.

4. 
   davidmeiland | Jul 14, 2010 05:06pm | #4

   I use a Drizair dehumidifer on almost every job. It comes in as the drywall board is stocked, and stays thru interior painting. It is amazingly effective at removing excess moisture from the job, and it might help in your case. When it's running I am monitoring the RH and temp as well as the MC of framing members and sheathing in various places.

5. 
   Frank | Jul 14, 2010 09:06pm | #5

   Martin
   Thanks for the feedback. The cellulose pdf file you passed recommends NO Vapor Barrier.
   From what I understand, the drywaller tape and texture sub applies a vapor barrier as part of his operation. Should he forego this? or is his application actually a vapor retarder and will not interfere with the cellulose drying to the interior (diffusion through drywall)?

6. GBA Editor
   Martin Holladay | Jul 15, 2010 05:56am | #6

   Frank,
   That sounds like a question for your drywall sub. I will repeat my previous advice: don't install interior polyethylene or vinyl wallpaper.

   If you or your building inspector want to see a vapor retarder that comes in a roll (instead of interior paint), install MemBrain, a "smart" retarder with variable permeance.