Flickering lights

Q.  My wife and I have lived in our home for almost five years. The lights in the home generally flicker for a brief moment a couple of times each day. At the time we purchased it, there was nothing listed in the inspection report which would indicate any electrical system irregularity or problem. We have not added any feature to our home which would cause a greater drain on our electrical capacity. I wonder if this is something abnormal or a cause for concern, and if so, what type of problem it might indicate.

A.    Flickering lights are always a hazard. They are usually caused by a loose connection somewhere from the main service entrance all the way to the power company’s connection.

A loose connection can cause arching or a hot spot, and can result in a fire. Loose connections or hot spots in the main entrance service should be addressed by a home inspector if they were present at the time of the inspection. You did not mention that this occurs only seasonally, so it rules out the possibility that it is caused by a neighbor’s air-conditioning unit kicking in if more than one house is on the same transformer.

You should have a licensed electrician check your service entrance and any other place he or she deems necessary, and correct the problem.

Installing light fixture on a ceiling that has heating cable

Q.    We have electric ceiling cable heat. In our living room, we want to add a chandelier but we are concerned if we can do it with ceiling cable. Our house is 30 years old and it does not have any light fixture on the ceiling presently.

A.    I assume that you will have a licensed electrician do the installation, as you should. The safest way to do what you want is to use wire mold, but extreme care must be taken not to hit one of the ceiling wires with any driven fasteners. For that reason, it is best to use adhesive.

Cold air comes in through recessed lights

Q.    My house is only nine years old and well insulated with one exception. The recessed lights that are in many areas throughout the  house allow a significant amount of cold air into the house in the  winter time; in fact, probably as much draft as one would find in a very old house.

I have asked for advice, and all I hear is that you can’t put insulation around these lights, and the only solution, an expensive one, is to replace them with the newer recessed lights that don’t permit air to go into the house. Do you have an inexpensive solution for this?

A.    Those who recommended changing to lights that “don’t permit air to go into the house” are referring to IC fixtures (IC stands for insulated ceilings). These fixtures can be covered with insulation and would be the best solution to your problem.

You didn’t say but assuming that you have flat ceilings and access to the attic, I’ll pass onto you a system a mechanical engineer friend and I devised years ago to solve this very problem. You can build a collar with 24-inch wide stock aluminum coil roll. Make the collar 24 inches in diameter and fasten its ends with sheet metal screws or pop rivets. Place this collar on top of the existing attic floor insulation Put a sheet of aluminum on top of the collar. Wrap R-13 fiberglass insulation around the collar and place the same type of insulation over the aluminum sheet.

This leaves enough air space around the fixture for the heat generated by the bulb to dissipate while blocking cold air from getting through and providing an insulated jacket. Be aware that this is not a procedure recommended by building codes.

However, if you have cathedral ceilings, there are only four solutions: Replace the fixtures with IC fixtures; replace them with surface mounted fixtures after insulating around the new electrical boxes and repairing the drywall; remove them entirely and patch the ceiling; or live with the problem.

Recessed lights in a cathedral ceiling

Q.    A few years ago, I added a one-story family room to my house. The  room has a peaked ceiling with recessed incandescent ceiling lights. The  ceiling is insulated with fiberglass. There is a roof vent and vents in  the soffits. The problem is that a lot of cold air comes out of the  recessed lights in the winter. Is there anything I can do about this?

A.    It is always a mistake to have recessed ceiling lights (also called  can lights) in a cathedral ceiling. There is not enough depth in the rafters to accommodate as much insulation as can be put in and still allow for a venting space. Unless a can light is UL-listed as IC (for  “insulated ceiling”), no insulation should be closer than three inches from it; this leaves very cold spots. Your problem is that there is little or no insulation above the recessed lights. Why don’t you have them removed, have insulation put in the spaces and a plastic vapor retarder taped over the holes, and then replace the can lights with surface-mounted fixtures.

Water drips from cathedral ceilings after cold spells

Q.    I am a self-employed building contractor and have followed your column for years. The problem that I am having is with two separate additions that I built within the last two years.

Both additions have cathedral ceilings with skylights. The construction consists of 2-inch by 12-inch rafters, 24 inches on center, with 5/8-inch tongue and groove plywood decking. The roofing material is 30-year asphalt shingles applied over No.15 felt paper, with Grace Ice & Water Shield applied around the perimeter of the skylights as well as to the bottom three feet of the roof. There are continuous 2-inch soffit vents as well as a continuous ridge vent on both additions. The rafter bays have plastic baffles for ventilation from top to bottom. R-38 faced-fiberglass insulation was applied below the plastic baffles and was stapled to the rafters. The ceiling is made of 1-inch by 6-inch tongue and groove beadboard applied to the bottom of the rafters.

The problem is that every time we have a real cold snap followed by a quick warming up period, I get dripping from the cathedral ceilings occurring on the inside of the additions. My first thought was that maybe the ridge vents weren’t performing correctly, so I tore off the existing vents and did them over. I noticed a considerable amount of condensation on the bottom side of the plywood as far down as I could see.

I contacted several architects I know as well as other people in the trade. The consensus was that because of the cold, condensation built up, and when the weather warmed the frost on the bottom side of the plywood melted, thus creating the dripping which took place. Hopefully you can provide me with some help in resolving this situation.

A.    I have bad news for you. The people you contacted are correct in saying that considerable condensation occurred during the cold spells. The subsequent dripping comes from the fact that the condensation froze on the underside of the plywood roof sheathing and melted when the temperature warmed up.

But the condensation takes place because you used faced-insulation and tongue and groove boards on the ceilings of both additions but did not provide an air barrier. Moist, warm air convects through the joints between the ceiling boards and bypasses the kraft paper vapor retarder. When it comes in contact with the cold roof sheathing, condensation occurs. No amount of ventilation can overcome this scenario.

If you had used unfaced fiberglass insulation and carefully stapled on 6 mil plastic as a vapor retarder, and had no ceiling perforations such as electric boxes, etc., you would not have this problem.

Unfortunately, there are only three ways to remedy this situation. One is to remove the ceiling boards and carefully staple 6 mil plastic to the underside of the rafters. The second is to remove the roof and the insulation and to spray closed-cell polyurethane between the rafters. The third and most appealing option is to have an experienced foam insulator remove the fiberglass from the rafter bays with hooks they insert from the fascia and the ridge vent and inject closed-cell polyurethane.