Why would you want to put a bunch of holes in your lovely insulated roof?

If you can't stop, I'd go with the lowest profile 4" cans you can find.

I'm using a Trac12 system by Juno. It utilizes a remote low voltage transformer wired to surface mount tracks. There are a variety of LED floods, spots and pendants that can hang from them.

For the kitchen we did dual fluorescent tube all around the top of the cabinetry. I think my ceilings might be a bit higher than yours and the reflected light is.....just right. No holes in the ceiling.

This is another "just say no" kind of deal- seriously! It causes enough issues with air sealing and heat leaks even in vented attic designs, but in vaulted & cathedral ceilings, fuggedaboudit! It's not worth it!

Also, an all-downlighting solution makes for some of the crummiest most shadow-prone ambient & task-lighting conceivable. The luminosity contrast between the high-intensity center and the field of ceiling surrounding (the technical definition of "glare") causes human pupils to constrict slightly, making for less visual efficacy at any lighting intensity. A combination of up-lighting to brighten up the field reduces the glare aspects and offers better acuity at all ambient light levels. The kitchen cabinet-top up-lighting is useful, but cove-lighting & wall sconces can do a lot of zero-glare high efficacy fill-in for other rooms.

In my own home I rarely even use the ceiling level down-lighting in the rooms that have dimmable fluorescent coves, in either the cathedral-ceiling portions or the standard-height flat-ceiling rooms. It's mostly lamp and task lighting, setting the general ambient levels with the cove lighting. If it were simple and easy to just rip out the pot lights in the cathedral ceilings, I do it, and wouldn't miss them a bit.

Bottom line, DESIGN your lighting, don't just hack it, and stop punching unnecessarily large holes in your ceiling.

A good place to start is to surf through the lighting design materials available on the RPI website.

http://www.lrc.rpi.edu/

http://www.lrc.rpi.edu/researchAreas/applicationDesign.asp

...the pot lights in the cathedral ceilings...

Dana.

Did you just tell us you have pot lights up there?

OMG. Have you even had a decent night's sleep since moving in?

Was thinking the same thing...would have thought that you would have capped and stowed the wires and foam insulated those holes long before now…

Greg - is your vaulted ceiling scissor trusses or truss joist construction?

Posted By ICFHybrid on 30 Jan 2014 02:11 PM

...the pot lights in the cathedral ceilings...

Dana.

Did you just tell us you have pot lights up there?

OMG. Have you even had a decent night's sleep since moving in?

Sure! (But only in the summer time! :-) )

When I moved in the  place had about 15-20 square feet of air-leak cross section and no foundation insulation, R7 rock wool in air-leaky kneewalls in the built out attic rooms, etc.  The useless ugly ice-dam inducing pot lights are on the list, but not at the top of the list- there are priorities.

The mid-term plan is to dense-pack the cathededral ceilings and put 5" of rigid foam above the roof deck when it's time to re-roof, which will likely be within 5 years.  Whether it's worth yarding the lights out at that point is still TBD, but there are still bigger energy-hog fish to fry on those rooms (like doing something about the 100 square feet of U0.5-ish clear glass double-panes.)  The foam-over should fix most of the ice-dam aggravation caused by the existence of those cans.  I've air sealed them from the interior, but they still seep a tiny amount of air when the house is pressurized. When the house isn't pressurized they still suck, but at levels difficult or impossible to detect with a smoke-pencil.

The economics of retrofits are VERY different from new-build scenarios.  Were I to build this 1920s bunglow + 1990s addition using the same floor plan from scratch it would have less than half the current heat load, and be far more resilient to moisture. (And it surely wouldn't have those lights.)  From where I started when I moved in the heat load has been cut by over 25%. With the projects already sketched out for the next 5 years it'll be hitting near 40% energy-use reduction since day-1.  (If U0.1-ish vacuum insulated glass becomes available in that time it'll be even bigger, since windows are currently about a third of the  present whole-house heat loss.)  Rome wasn't built in a day, but it didn't burn in just one day either.   Attacking the big issues takes priority over the nuisance problems.

But on new builds it's worth designing-out those silly nuisances, eh?

Thanks for the replies and links. Hopefully this will help curb my better half's appeal of pot lights.

FBBP - They are a scissor truss with an extended heel, with about 24" of room for insulation. Blowing in cellulose, so no problem getting R50+.

Posted By sleddermb on 03 Feb 2014 04:00 PM
Thanks for the replies and links. Hopefully this will help curb my better half's appeal of pot lights.

FBBP - They are a scissor truss with an extended heel, with about 24" of room for insulation. Blowing in cellulose, so no problem getting R50+.

Here's more timely grist for that mill, if need be.

Recessed can lights in vaulted ceilings are of the devil.
Just say "NO" to pot lights in vaulted ceilings.
File for divorce if your spouse insists on recessed can lights.



In all seriousness. One way someone could install recessed can lights in a vaulted ceiling is by utilizing SIPs and then using a furring hat channel to drop the ceiling by 1.5" - 2.0" and then installing a low profile recessed LED can light within the furred spacing. The SIP is never cut or manipulated in away way and the can light sits below the SIP within the furred channel and finished drywall.

Sorry Dana - but that's crap.
The reference •••You can check out this article•••• just goes to show that the author and apparently a number of people on this forum don't know what vapour hats are or how to properly install a poly membrane so that its air tight, much more air tight then any drywall, osb or any other combination. Talk about drywall boxes, caulking around lites, its just not done. A proper IC can and a vapour hat is all that is needed. As I've said before Canadian codes have mandated this approach for two and a half decades and the results show for themselves. If we had anywhere near the exfiltration the author talks about, our attics would be full of ice crystals. At very least, we would experience frozen cellulose around the lights. This just doesn't happen. Sure you can have a poor install but that is the case with any product.

sleddermb - you are Canadian and work in the trades so I'm sure you are familiar with vapour hats for electrical and exhaust fans. When properly mounted and sealed to the heavy duty 6 mil poly ceiling membrane you will be putting on your ceiling, your IC pot lights are more air tight then the same combination for a standard octagon box. As you have scissor trusses (and that's why I asked) you have lots of room to add a pile of cellulose over each pot light.

You might consider though that when approaching the height of your vault, the light source will be a long way from their target and therefore might not be the most efficient way of lighting.

As for the better half, you can tell her what ever you want ;-)

Well, even if you solve the exfiltration problem perfectly, you still have the problem of a quarter square foot hole in your insulation layer for every can. At 7-1/2" in height, don't they effectively halve R50 insulation, not to mention what they do in vaulted ceilings?

And, I have to point out, once again, that the theoretical treatment of such things is very different from what I've actually seen routinely practiced by the installers.

Posted By ICFHybrid on 03 Feb 2014 08:54 PM
Well, even if you solve the exfiltration problem perfectly, you still have the problem of a quarter square foot hole in your insulation layer for every can. At 7-1/2" in height, don't they effectively halve R50 insulation, not to mention what they do in vaulted ceilings?

And, I have to point out, once again, that the theoretical treatment of such things is very different from what I've actually seen routinely practiced by the installers.

Exactly. 

In a cathedralized & vaulted ceilings you usually don't the option of heaping another 6-12" of insulation over your perfectly tight fixture, and since the fixture is a heat source when the light is on, you end up with localized heating at the thinnest point of the insulation.

Even though I rarely turn them on, I can easily find the locations of the (now nearly-tight) fixtures on the otherwise-R38 cathedralized ceiling by the location of the ice-bumps while raking snow off the roof (necessary after a big nor'easter to limit ice dam formation.) They DO have at least some insulation over the fixtures, but not NEARLY enough to manage 2'+ of snow on the roof.

On a possibly related topic, there's a pretty good primer on detailing a poly vapor barrier in a ridge-beam cathedral ceiling (sans pot lights) as a primary air barrier in this video.  There are plenty of good tips to be had there!

I can't say they did nearly as good a job at detailing the batt insulation as they did the poly air & vapor barrier in that demo though- I'd flunk it on the number of voids & compressions. There are even some short-batts with voids near the bottom plates in some of those bays. Caulking the framing to the sheathing would be in order too.

I would not recommend pots in I joists ceilings. But in scissor trusses, why not? It would cost 'bout a buck thirty-three to pump an extra puddle of cellulose over those pots. OP indicated LEDs so probably not anywhere close to 7.5". Even if he is going to use full height IC cans, he has the height for insulation.

When I see a poor ICF job, I don't blame the block and I certainly would not recommend that no one use ICF ever again. If I see a poor framing job, I don't blame the 2 x 6.

OP has indicated both a new build and scissor trusses. You might not use either poly or pot lights everywhere but for an open vented attic using cellulose, they are about the best bang for the buck. And more important, the easiest way to air seal the attic.

WRT the video. First he is using regular grade 6 mil poly. Canadian codes require poly to conform to CAN/CGSB-51.34-M or as known in the trade as CGSB poly. Yes, it is also 6 mil but is much tougher. It can handle tack hammers and other abuse much better then regular 6 mil. It costs us around $85.00 to $95.00 per 1000 sq. ft. roll depending on which wholesaler we pick it up at.

Prior to place the poly, all double studs and plates (anyplace where you can't get insulation between) should be sealed with acoustic caulk. And while the video doesn't show any wiring, all holes in top or bottom plates, both interior or exterior walls, should be caulked as well.

All penetrations should be in place prior to insulating and sealing. And you would never vent an oil burner under a window.

If you noted the poly under the ridge caps, it is normally available in 18" wide rolls of CGSB poly (framer's poly). The framers will install this between the top plates of any interior wall meeting an insulated ceiling and behind the end stud of any interior wall meeting an outside wall. Now when you install the ceiling and wall poly, it will be continuous after you apply the caulking on the seams. And don't forget to caulk the holes Sparky made when he ran the wires.

The amount of staples he used for that little shack should be enough for a 2000 square foot house. Just use enough to keep the poly from getting snagged on the drywall when the boarders swing the sheets into position. The poly should go on just before the boarding crew arrive to limit any chance of damage. And make sure you leave a few partial rolls of tape around so that the boarders can do damage control.

I didn't do away with pot lights entirely, I just tried to keep them out of the insulation envelope. I used them quite extensively under second floors and other such places where their negative qualities don't matter so much.

Little shack? That’s looks like the perfect size place to me! However, it really should be in a much nicer and more private location.

As you get older you appreciate that it isn’t how big your “wants”, but how little your “needs” to be truly happy. I suppose my perception could be biased from having spent three years on a 38 foot sailboat circumnavigating the planet during my younger days. Small space is good space when shared with people you love, doing stuff you love. This is especially true when this space is in a hostile environment.

Posted By FBBP on 04 Feb 2014 06:54 PM


WRT the video...

Yeah, there were a lot of things half-assed or toddully rong in that video, but the sealing job on the poly  (which was the point of the demonstration) seemed about right, eh?    

It appeared to be a throwaway demonstration project but it would have been worth doing the whole thing a lot better (and explaining it) if they were going to do the project at all.

Sailor - it was not my intent to deride the size of the shack but rather the amount of staples used. If you are saying that most of us build a lot more house then we need, then I would have to agree with you.

Dana - its good from the point of view that people understand that there is no point in just throwing some poly on a ceiling and it's going to work but I agree someone should do a good video on the subject. Here's your chance to be a movie star!!

Certainly no offense taken FBBP. Also totally agree about the excess staples…and found your info quite educational too.

I watched another video several months ago where the poly was pre-glued to the drywall with about 2 inches of overlap. The boarders just applied adhesive/sealant to the studs prior to screwing in the drywall. Then they just applied adhesive/sealant to the seams before placing next sheet. Hadn’t seen that before and haven’t tried it either, but it avoided the use of any staples and tearing the poly.

I already have this situation and want to seal it up and put track lights. What do you think about using can light converter, and sealing up the old light can with spray foam and caulk?

It sounds like the can light converters depend on leaving the cans in for mounting support. The cans I've seen are often installed poorly with gaps around the insulation. It would be nice if you could check for that at the same time.

True. I was hoping to leave the old cans and fill them with insulation. I can't find any info or videos online that describe doing so.

I suspect the converters tie into the old can wiring therefore this has to remain accessible.