Ceiling Insulation

Old 02-15-04, 11:35 PM
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Ceiling Insulation

I have a condo unit which is the 2nd floor of a 3 story building. I recently had flood damage which took down the ceiling and the insulation that was in there. It appears that the insulation had been blown in and looks like shredded pieces of cotton. When the ceiling came down I kept finding round foam plugs which I assume were to close the holes made by blowing in the insualtion. I have never done insulation work before and have some questions.

First, I'll give a brief description of how the unit is set up. The front wall of the living room has a sliding glass door that goes out onto a small deck (deck extends approx 3 1/2 to 4 feet out). This is common to all the units in the building, except for the groud floor which has a small garden yard. The way they are built, my ceiling rafters extend the 3 1/2 to 4 feet out and that provides the flooring for the deck above me, and is finished to be the ceiling of my deck. Where the rafters end, there is a stone exterior to the building. The floors of the units are some type of poured cement on top of the wood that my rafters attach to.

Now to the questions. I need to reinsulate. Since the bulk of the ceiling is down, I figured I would be able to handle the insulation job. I am somewhat handy, but this is just something I have never attempted. I am concerned with the extension that goes out over the deck. I don't think I should just put the insulation there as I am ceoncerned about moisture and possible mold growth. My question is this, should I staple plastic inside the rafters to control moisture and drafts? If so, would this be placed at the area above the sliding glass door? Say a square that would be stapled into the top then sides of the wood? Secondly, since this unit has a unit above it, would I need insulation with a vapor barrier? Should I install an additional vapor barrier between the insuation and the drywall? Would this vapor barrier just be a sheet of plastic that was installed on the edges of the rafters. Stapled? Should I be concerned about moisture between my unit and the unit above me?

If necessary I can provide a bit of a diagram of how the unit is layed out showing what I described above.

Thanks in advance!
Old 02-16-04, 08:00 PM
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The ceiling directly above the outer wall to your small deck, you insulate it as a continuation of the wall with a vapor barrier. In other words, you stand up the insulation in between the ceiling joists as if it was part of the wall insulation. This is because this portion of the ceiling is the only place in the ceiling that separates a conditioned space from an unconditioned space.

As far as the rest of the ceiling inside the house, install unfaced insulation, without a vapor barrier. The insulation is primarily being used as a sound barrier. Even though each apartment has their own heating units, heat flow is induced by temperature difference. For example, if you keep the temperature in your apartment at 70 degrees and the apartment upstairs does the same, there will be very little heat flow from one apartment to the other. On the other hand, if the temperature in the house is 70 degrees and outside is 30 degrees, there is a considerable amount of heat flow. The reason for this is known as equilibrium. Where areas of different temperatures tend to attract till both areas have the same temperature. The greater the temperature difference, the greater the attraction.

For your information, all heat loss/gain calculations are based on this principle.
Old 02-17-04, 06:21 PM
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Thanks for the info.

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