Qs on Blowing Insulation in Attic

The attic in my 20-year-old house has only 6 inches of blown insulation. All electrical fixtures are covered by the insulation, there is no vapor barrier, and there are no soffit vent baffles (but the soffit vents aren't covered by insulation, which is good). I am going to add another eight inches of blown insulation. Since it has gone 20 years without a fire, is it safe to assume I don't have to uncover the electrical fixtures? Since there have been no moisture problems, is it safe to assume I don't need to move all the current insulation and add a vapor barrier? At the soffit vents, do the bottom of the baffles staple to the existing 2x6 board, as shown in the following artistic masterpiece, or do I not bother with baffles and just be careful to not blow insulation on top of the soffits?
/ <---(top of baffle staples up here) / / / / roof rafters / / / | <---(bottom of baffle staples to top of this 2x6?) / _|_____________________ _^_^_^_| attic joists soffit vent
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The easiest thing as far as baffles I think is to buy the styrofoam baffles and staple them up to the underside of the roof sheathing. They're relatively inexpensive and will save you huge amounts of time and trouble when blowing in the insulation. What I did in addition to that with my house was stuff a little bit of fiberglass batt against the bottom edge of the baffle to keep from blowing anything past the baffle into the soffit. If you're going to be up there poking around, it probably wouldn't hurt to carefully find any junction boxes and light boxes and just give them a quick inspection for any problems. It's probably not a big deal, but you're going to be up there disturbing the insulation anyway, so why not have a look? I don't know how to answer the vapor barrier question. If it were my house, and there was adequate ventilation, I wouldn't worry about it. A well-taped drywall ceiling can be a decent vapor barrier if nothing else is there. You could also dig to the bottom of the existing insulation, there may actually be some type of barrier there already.
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Assuming they're recessed ("pot") fixtures:
No. Another 8" of insulation will trap heat into the fixtures a lot more readily, so you need to do some checking.
Check the fixtures very carefully for the acronym "IC" on the label. It stands for "insulation covered"...
If they say IC, you're all set, you can bury them and not worry about it. Mind you, at 20 years it's a very doubtful they're IC.
If they're not IC, you have several options:
1) replace them with IC-rated fixtures. They're only a few bucks more than ordinary ones. This is often easy to do - depends on how the previous ones were installed. This is the best option if you care about insulation (and obviously you do).
2) "box" them in with plywood - our codes talk about something like 8 cubic _feet_ of air space required. Or, at least they did - with IC fixtures being readily available, they may not permit boxing anymore. You can get most of the insulation value back by covering the boxes with insulation. A lot of work.
3) simply "uncover" them. Poor insulation value, and I worry about future disturbance of the loose insulation.
4) construct a "well" out of plywood to keep the insulation out. Safer, but still poor insulation value.
5) Switch to very low wattage bulbs (ie: CF floods). Someone in future may not remember _why_ they're CFs...
6) Prepare for a fire.

Research has proven that a good paint job on the ceiling acts as a perfectly adequate vapor barrier. Inspect it, and if in doubt, repaint with a good latex paint. If the fixtures are IC, bag 'em with vapor barrier plastic to eliminate drafting/air leaks around the fixtures - ie: big plastic square that's been fastened to the joists and ceiling drywall with staples and accoustic sealant (unbelievably sticky goop) or "tuck-tape" (vapor barrier tape). If they're not IC, don't do that.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Well, I ended up doing the job myself. Renting a blower from Lowe's was free with the purchase of 20 bags of insulation. You do, indeed, need two people. Installing baffles is a must, as the insulation blowing out of the tube up there sprays a lot of very fine material that floats all over. So you can't just aim it to avoid clogging the soffit vents. Note that since it gets real dusty during blowing, if you have a gas furnace with a pilot light up there, turn off the pilot before starting. I highly recommend blowing over blanket, and doing it yourself. It's easy, and saves money.
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