Replies

1. 
   DanH | Dec 27, 2009 03:33pm | #1

   If you simply wish to secure the insulation from falling out, the simplest approach is to put numerous small nails in the bottoms of the joists, about 16-24" apart, then zig-zag piano wire or twine between them.

   A slightly better approach, without replacing the insulation, is to tack up some sort of housewrap, or even just landscape fabric. This holds the insulation in place and also behaves as an air barrier, improving significantly the (poor) insulating quality of the fiberglass.

   Of course, many here will tell you to rip out the fiberglass and get the area sprayed with foam. Not a bad option (aside from cost), but be sure that you do any minor plumbing or electrical repairs first.

1. 
   rjw | Dec 28, 2009 06:10pm | #4

   >>If you simply wish to secure the insulation from falling out, the simplest approach is to put numerous small nails in the bottoms of the joists, about 16-24" apart, then zig-zag piano wire or twine between them.

   I think the 16"+ (or 24"+) stiff wires that spring into place between the joists are a LOT easier....

   Never tried the "nails and woven wire" technique but it sounds like a lot of work.

   See, e.g., http://store.contractor-pro.com/insulation-supports-c-54.html

1. 
   DanH | Dec 28, 2009 08:39pm | #6

   I think the 16"+ (or 24"+) stiff wires that spring into place between the joists are a LOT easier....

   A lot easier, only I've seen too many cases where they don't stay put.

1. 
   rjw | Dec 29, 2009 05:39pm | #8

   Hm.
   FWIW, I haven't seen such
   Hm.

   FWIW, I haven't seen such cases except where someone tries to space them too widely....

2. 
   rjw | Dec 28, 2009 06:12pm | #5

   duplicate post

2. 
   Clewless1 | Dec 28, 2009 08:35am | #2

   What Dan said. Criss cross w/ durable twine to hold it in place. If you want to do a real good job and improve the performance, use Tyvek as it will help reduce the convective air circulation w/in the floor.

   What is your location? Do you have a lot of ground moisture? You MIGHT consider blocking off the vents if you install a good vapor retarder on the ground.

1. 
   DanCC | Dec 28, 2009 11:44am | #3

   We are in central Maryland, about 45 miles north and west of Washington. Heavy clay soil conditions, but the crawl space is dry. Water problems come from other areas. I found out about the insulation when I checked on "Boxing Day' when water was coming in the basement from blocked gutters, bilco door etc. 22 inches of snow followed a week later by 2 inches of rain/rapid melting is not a good combination.

3. 
   benraymond | Dec 28, 2009 09:01pm | #7

   I posted a very similar question a short while ago. I have the same problem in a more northern (massachusetts) location. My bats were held up with tyvec - didn't work, many are on the floor. I'm going to staple up plastic mesh to hold my batts in place - look for "Tenax" at the home depot web site.

   The bigger issue I have is what to do about the crawl space. I blocked up the vents and I plan to encapsulate the crawl space - if you have moisture problems deal with these first. This will hold in the hot or cool air and become a conditioned space. Then the batts are less important in the floor (I'm dealing with mine anyway). There are a couple of sites that specifically advise against spray foam for the below grade foundation walls - it traps moisture and can rot out your foundation, apparently. Good luck!

   http://basementsolutions.blogspot.com/2009/11/do-not-spray-foam-your-crawlspace.html