Just to be sure, you're using reflector-type lamps such as PAR30 or R30's, right? These cans aren't meant to be used with cheap, conventional bulbous lamps.

When insulation was installed between the floors, was it cut back 3" from the fixtures or was it run right up to the cans? If the contractor did things in such a way that insulation is close to or touching these non-IC cans, he's guilty of some major no-no's and I'd be more than a little ticked off.

If the space above the room being lit is uninsulated (an attic above, or if the ceiling is the underside of the roof), then you'll need sealed, IC-type cans. In places where the cans are between heated floors and the insulation is just there for sound deadening you can go either way, using IC cans or cutting (not pushing) back the insulation so the clearances are correct. Trying to address it by using dimmers or lower-wattage bulbs would be ridiculous.

Jon: Thanks very much for your comments. I checked with my invoice and the installed bulbs are the 75 watt PAR30's. Our home is actually 3 levels (full basement, first and second floor). The lights that were cycling on and off that I've noticed so far were in the ceiling of the basement and the ceiling of the first floor. I'm not sure whether the insulation was cut away from the cans when installed. We also have full insulation in the attic area. I'm not sure if the cans in the attic area are sealed IC type or not. How should I tell the contractor to correct this problem?

You're not going to know what to do until you diagnose the problem. I'd mark a few of the lights that are problematic and examine them closely. I just looked up the spec sheet for the H5T, and it appears there are a couple of screws going sideways through the can into the support frame just above ceiling level, visible after the trims are removed. If you remove those screws with the lights turned off, mind you) you may be able to pull the can down out of its frame enough to see whether the insulation was cut back properly or run right over the fixture. If you discover the insulation was not kept back from the fixtures then fixing this is going to be a real headache. But really, slow down and figure out exactly what is wrong before you grasp at solutions.

FYI, I installed recessed cans in my own insulated ceiling, but I am not a licensed electrician and don't have oodles of expertise here. I'm guessing that stupid and costly mistakes may have been made, but please proceed with the understanding that I may be wrong.

Correct diagnosis here is the key. I just talked with the contractor who believes that IC units were required by city code. We will confirm tomorrow. If they are IC units, do you think that some individual units might be defective?

"do you think that some individual units might be defective?"

If it were only a couple of units giving you trouble then that might be believeable, but it seems a very unlikely explanation when so many are affected.

One other thought -- which trim did you use? Some trims are more limiting, in terms of bulb size and wattage.

With a little persistence I think a sound explanation will become obvious. Just don't rush into some half-a**ed solution like keeping them dimmed all the time; make sure the system works as advertised.

Halo H5T's are a non-IC fixture, so if IC units are required by code, that's a BIG problem. If the cycling problem persists in applications without insulation around the fixture, the only option is to reduce the heat being generated, either by going to smaller wattage incandescent bulbs or to more efficient fluorescent bulbs.

why did he put drywall before checking the function of the lights?

we just put in 4" halo's and my son wired a can with an exposed wire. it did the same thing, on/off. It may be the wiring.

whatever the cause, it's not your problem to fix. If the builder gives you any trouble, call the building inspector and have him come check it out. I've found BI's are a home owners best friend when dealing with contractors that want to blow off work that was done wrong.

If the reflector/baffle trim is no. 5001, 5010, 5012, 5013, 5020, or 5060, then a 75w PAR30FL or R30FL lamp is acceptable. If it is the basic "splay" 5000 trim it can only take a 50w PAR30FL or R30FL lamp. All the other 5000 series trims can't take 30 series reflector lamps; most take standard A-19 or BT-15 lamps.

If the insulation is closer than 3" to the housing, only the electrician or the manufacturer can tell if it is possible to remove the housng in order to adjust the insulation.

First try a PAR30 halogen lamp instead of an R30 lamp. Then try a 50w PAR30.

Good luck

Here is a link that might be useful: Halo housing

The problem is almost certainly the insulation. Non insulation contact lights require that the "attic" insulation be pulled back 3" and the top be open to the attic space. If a non IC can is enclosed in a box, either in the attic or between floors then the box must be large enough so that the heat can disipate thru the sides of the box. Pulling the insulation back 3" from a non IC can installed in your first floor ceiling is not nearly enough.
Instalation instructions may not mention this because insulation between floors is rare.

There is no definite recomended size for how big a box is needed to disipate the heat because it depends on how well the box is insulated. I have heard recomendations of 2' x 2' x 2' and 2' x 2' x 4' for boxes over attic installed cans. presumably these boxes would be covered with insulation.

Whats happening in your lights is that a 15 cent thermostatic switch over heats and turns off your light before it gets hot enough to melt the wiring insulation or start a fire. If one of these high quality 15 cent switches fail then you will have a real problem.

I hate people that point out problems and then don't offer any solutions. So I'll offer one, although you probably won't like it.
All cans are designed so that the housing can be removed to access the wiring connections. Remove the housings and pull out the insulation. use a coathanger hook to pull out everything within 2' in the cavity where the light is mounted. This may be easy or tough depending on how the insulation is fastened in.
Another possibility is that the same brand IC contact housings may be able to be retrofitted into the existing non IC frames that are in your ceiling. That's a long shot but may be worth looking into.