resercon: Insulating around recessed cans...


Old 12-24-04, 08:07 PM
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Join Date: Dec 2004
Posts: 13
resercon: Insulating around recessed cans...

I noticed your suggestion on this other thread:

The illustration you referenced made this recommendation for IC-rated fixtures.

I have a similar problem but I have 65 recessed cans in my home. They have peforations and consequently leak like sieves.

None of them are IC-rated, but they all have heat cut-off switches.

I read the following recessed can study and have been busy building drywall boxes:

Note that I have also been replacing the incandescents in the enclosures with flourescents in order to minimize heat buildup.

What are your thoughts on building sealed boxes for non-IC cans with heat-overload switches?

If you disagree with the practice, what would you do to minimize heatflow in a case like mine?

Finally, I live in Dallas, so my costs are primarily electrical during the long cooling season. Its easy to see the benefit of these boxes during the winter, but what sort of improvement would I expect in the summer?

Thanks in advance.
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Old 12-25-04, 05:07 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873
Recess lighting is by far the most inefficient type of lighting when used for general lighting purposes. The costs is ridiculous. Let's make some assumptions.

1. Each fixture uses a 60 watt bulb.

2. Each fixture is operated 6 hours a day for 365 days for a total of 2,190 hours.

3. The costs per KiloWatt/hour is $0.10. You can substitute the actual cost by looking on your electric bill.

4. Kilo mean 1,000.

The formula in determining cost to operate is (Wattage of appliance) times (Annual hourly usage) times (Cost per KiloWatt) divided by 1,000.

So 60 x 2,190 x .10/1,000 = $13.14 Cost per year. So what you say. But if you multiply this by 65 canisters, your cost just for lighting is $854.10 per year. Guess what? That's more than all your other electrical applicances cost combined, other than your heating and cooling. It's more than cost of both your water heaters.

Let's say you don't use all the lights everyday and some not even for that length of time. Let's say, and I can be generous here because I don't pay your electric bill, it's half. It's still $427.05 a year. Clearly, this lighting is the third largest energy consumer in your house. It's behind your heating and cooling because it is attributing to the cost to heat and cool your home. That's the only reason why it's third.

Would I recommend replacing the bulbs with 25 watt CFL's and installing an air tight cover for each canister in the attic. Well let's see.

25 x 2,190 x .10/1,000 = $5.48 times 65 = $356.20 subtracted from $854.10 = $497.90 in annual savings.

So let's say each CFL costs $15. and last five years. $15. x 65 = $975.

You can also factor in what it is going to cost you to install the covers. But what the aforementioned illustrates that it is not the cost of the appliances that makes our energy bills high, it is the shear number of appliances we have that does it. And if you think 65 lighting fixtures are a lot, try walking around you house counting all the appliances that use electricity. If this was my house, I would think about the lighting design and look at options that are more aesthetically pleasing and certainly more functional.

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