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
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
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.
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.
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
I highly recommend blowing over blanket, and doing it yourself. It's
easy, and saves money.
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