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I'm trying to figure out how to shoot silica gel pellets into an enclosed space in my ceiling.

Is there some sort of tool, mechanism, or technique to shoot dry, pellet-like or sand material, vertically, into an enclosed space where the only access is a hole from below the space?

  • You could rig something with a shop vac on blow, and a container for pellets that the shop vac blows in, and a tube small enough to fit in your hole comes out. Make the tube long enough so it will fill from top of space down, or you'll likely only get a half filled space as the pellets start to clog the tube. A piece of window screen around the tube, perhaps taped around the hole should prevent pellets from fall out of hole. – Wayfaring Stranger Sep 6 '18 at 4:55
  • Styrofoam, as found in "beanbag" chairs is likely you best choice for insulation, light weight for blowing, and insulation R-value. – Wayfaring Stranger Sep 6 '18 at 5:02
  • I have rented insulation guns for blowing chopped insulation in walls before, I think it was a 1" hole maybe smaller but that may be a possibility to pump your pellets. – Ed Beal Sep 6 '18 at 14:00
  • Why silica gel? That's a dessicant that attracts moisture. – Mike Waters Jan 21 at 13:21
  • @MikeWaters i was thinking that it would dry up the enclosed space and lock up the moisture so it is not available to mold. that's what silica gel is for -- to lock up moisture so the important things aren't affected by the moisture. – JDS Jan 22 at 15:08
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I don't think what you are trying will work. You appear to be attempting to dry out a ceiling cavity using silica desiccant, but:

1) Silica gel is a one-use material. Once it's full of water, that's it.

2) I'm a bit worried about the weight; if you're placing this into a ceiling cavity, it'll be supported by the drywall, and basically nothing else. Back of the envelope says 44 lb/sq ft, (assuming you place it one foot deep) plus 40% for water weight, so 60 lb/sq ft. This is a significant weight. Even one inch will give 5lb/sq ft over the entire cavity, and drywall is not designed to provide any support. If you're putting enough silica in the cavity that it's necessary to bring in actual power tools, the weight matters.

If the actual problem you need to solve is removing moisture from a ceiling cavity, there are better ways of doing this. (Solve the issues that allow moisture to accumulate, then add ventilation to encourage evaporation.)

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The simplest thing I can think off is to get a large enough hose and a Y-connector. Run a hose from the output of the Y to the hole. Attach an L-shaped elbow to the end of the output so that it blows sideways and not into the ceiling. Attach an air compressor so that it blows into one of the inputs. Feed pellets to the other input (ideally from the top to utilize gravity). The air stream created by the compressor should grab the pellets and carry them into the target space.

However the pellets will only fly so far depending on the strength of the compressor - this would be a problem with any injector. They will pile up around the hole, and might not get easily to corners farthest from the hole. I imagine if someone planned to use this method they would expect to have several holes, at least 1-2 meters apart. As far as working with what you have, you could periodically plug the pellet input, and let the compressor simply blow air, to push the pellets away from the hole.

If you run into airflow problems, use a thinner hose. It should speed up the airstream. Obviously, using pellets made of a lighter material will work better.

Will you ever need to remove them, though? That might get tricky if you can only do so through your one hole. You'd need a long hose for a vacuum cleaner that can be snaked into every part of the space.

  • i like this idea. no, i never plan to remove them. also, the total size of the confined space is 15" by 15' (between joists in a ceiling in a 15 foot room) – JDS Sep 6 '18 at 21:40

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