Help replacing downlights with ones I can insulate over

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timmmay

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#499304 29-Jul-2011 11:06

Thanks again JJ. I want something specifically designed and rated to be insulated over, or a way to close up the ceiling and hang lights underneath.

timmmay

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#499307 29-Jul-2011 11:08

gzt: Just googled for that consumer article. The main conclusion is: "Recessed downlights waste energy by sucking warm air from your living area into the roof space".

Insulation or lack of it is very far from the main factor.

If cans slow heat loss, most of the benefit will come from slowing air movement into the cavity.

And from rightlight: "Most recessed downlights have large ventilation air-gaps that keep the light bulb (and your house) cool, by venting warm air from your living areas into the roof space. "Little chimneys” - as downlights are known in energy-efficiency circles - could be robbing you blind"

Good spotting, I didn't notice that. That would be a huge factor. In my lounge I could feel the cold draft coming into the house. Cans might help, but these lights in the office won't be letting much air out - they have smaller gaps and that ceiling is better sealed.

I read all over the place though that small gaps in insulation make a big difference, so I do want insulation over the lights.

vinnieg

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#499337 29-Jul-2011 11:30

timmmay: Does anyone know how to get these fittings out of the ceiling? I think they're probably attached with clips, but I guess you don't just pull them, it may take the ceiling with it.

Just pull them really slowly starting at one corner, it'll have two snap back clips on a spring, so watch your fingers, they hurt when they snap back

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wallross

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#499339 29-Jul-2011 11:30

@timmmay

We made the mistake of putting some down lights in when we did renovations a few years back, and on a windy Wellington day in winter, it was like standing under a hair dryer on "ice cold" setting.

BUT - The solution we used was to replace the lights with Bathroom rated ones (IP something...) which fitted into the same holes. These have a glass covering on the front that seals to the until with a rubberised gasket (to stop any moisture getting into the fitting). They have stopped ALL airflow though the light fitting.

Then again - any of the downlights with a glass faceplate on them (eg http://www.lightingplus.co.nz/lighting/recessed-lights/ceiling-halogen-12-volt/) will drastically help. You just wont be able to "angle" the lights anymore.

You then do not need to worry about trying to get into the roof to insulate over, BUT they still need a clearance from insulation, or proper heat cans to protect the lights from touching the insulation.

The lights do cost $25-35 a pop from memory, but can be connected to exiting transformers, and may even take exactly the same halogen bulbs if you are lucky. As for Electrician costs, if you are in any way technically skilled, I would give it a nudge yourself (just do not tell your local council inspector!)

Hope this helps!

Ross

timmmay

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#499422 29-Jul-2011 13:55

@vinnieg thanks i'll try that this evening.

@wallross sealing would be a small win, given the light fittings and the ceiling/roof don't seem to leak much air. Insulation is what i'm mostly focused on. That's interesting about the glass faceplates though :)

wongtop

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#499447 29-Jul-2011 14:48

timmmay: @vinnieg thanks i'll try that this evening.

@wallross sealing would be a small win, given the light fittings and the ceiling/roof don't seem to leak much air. Insulation is what i'm mostly focused on. That's interesting about the glass faceplates though :)

These ones you can supposedly insulate right over, but they're $60 a pop. http://www.lightingdirect.co.nz/cronos-gx53-13w-27000k-recess-downlight-matt-white

timmmay

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#499448 29-Jul-2011 14:50

wongtop:
timmmay: @vinnieg thanks i'll try that this evening.

@wallross sealing would be a small win, given the light fittings and the ceiling/roof don't seem to leak much air. Insulation is what i'm mostly focused on. That's interesting about the glass faceplates though :)

These ones you can supposedly insulate right over, but they're $60 a pop. http://www.lightingdirect.co.nz/cronos-gx53-13w-27000k-recess-downlight-matt-white

Yeah they're the ones Mauricio recommended earlier in the thread, thanks :-)

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Regs

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#499543 29-Jul-2011 19:19

The consumer article, and others, will be basing their heat loss calculations on the light fittings with no rating, and therefore assuming the mandatory 150mm insulation gap around each one (which would then usually end up being cut square as its easier)

A CA (closed abutted) light fitting means that the insulation goes right up to the fitting/heat can, and where there is les than 5% of the area that is 'open' between the ceiling and room. These are the fittings that I have and mentioned earlier. With the CA rated fittings, you dont lose nearly as much heat as you do with the non rated ones.

check the NZA 4246:2006 standards guide on "installing insulation in residential buildings" here for some useful info and tables:
http://www.energywise.govt.nz/node/3009

execerpt from the PDF:
"For example a ratio of one recessed light fitting for every 5m2 of ceiling will reduce the effective thermal resistance of
R 2.5 insulation by approximately 10% so in that situation using R 2.8 insulation instead
of R 2.5 would go some way toward compensating for the thermal bridging associated
with the recessed light fittings. This calculation does not take into account the additional
thermal bridging that will occur if there is natural ventilation through the light fitting"

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www.snowflake.com

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timmmay

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#499623 29-Jul-2011 23:03

Regs: The consumer article, and others, will be basing their heat loss calculations on the light fittings with no rating, and therefore assuming the mandatory 150mm insulation gap around each one (which would then usually end up being cut square as its easier)

That's not correct. Consumer a variety of fittings, including CA (closed abutted) rated lights, though apparently CA rating means "there’s still a vent but its area is no more than 5 percent of the area of the hole cut in the ceiling.". One CA rated fitting (closed, insulation abutted) means 189% of the closed insulated ceiling - ie 89% more), almost double. With four CA fittings it was 284% (184% more heat required, almost triple). Another interesting number is with 4 RS rated bulbs (ie a breeze and a gap) the number is 333% - three times more heating is required.

This isn't regular house though, which has random gaps, windows, etc, it's purely talking about heat loss through the ceiling. Still, it shows that even CA rated downlights really shouldn't be used at all, only fully sealed units with insulation over the top.

It's a members only site, so I don't want to breach any rules about sharing articles or graphs wholesale.