Acoustic Rated Downlights

[endorka]

As part of my studio acoustic improvements Stuart recommended putting more insulation in the attic type eaves that run along the front and rear walls to dampen down resonances in them. There really wasn't much loft insulation in the front eaves at all, far less than recommended by UK building guidelines.

After a bit of investigation I found out why. The problem was 11 halogen ceiling downlighters in two bathrooms directly below the eaves. These had been installed through circular holes about 75mm in diameter through the ceiling plasterboard, directly into the eaves. Of course the acoustic isolation of the ceiling takes a big hit with this practice. And not just that, the fire rating goes. And to top it all, the light bulbs get hot, so you can't stack insulation over them, whether halogen or LED. Thus the small amount of insulation - the installer had actually done the right thing by keeping it sparse.

Fortunately, there is a solution for LED bulbs. It is possible to buy downlighter fittings that are fire rated, acoustic rated, and can have insulation stacked on top of them up to a depth of 300mm. In a nutshell, they make good the deficiencies in the ceiling caused by cutting a hole in it. I ordered the following type, the fixed ones are best. At about £6 per fitting they were only a couple of pounds more expensive than standard ones;

Aurora EFD Pro - Fire Rated Insulation Coverable Downlights
https://www.downlights.co.uk/aurora-ins ... ights.html

enlite-efd-pro-fixed-mw.1510330241.jpg (9.33 KiB) Viewed 21145 times

enlite-efd-pro-fixed-mw.1510330241.jpg (9.33 KiB) Viewed 21145 times

These are far more impressive than the usual downlighter fitting, which is often just a pressed metal disc outlining a huge hole into the ceiling void. These are large, heavy and solid with a proper seal between the bezel and the ceiling. The electrician was seriously impressed with them. On the fixed version, with the bulb fitted there are no gaps through it into the cavity. The weight of the bezel and bulb portion feels consistent with putty pads, so the acoustic rating seems credible.

The adjustable version does have a small gap even with the bulb fitted, so probably should be avoided for best acoustic isolation.

I suppose if acoustic isolation was a big priority ceiling downlighters would be avoided altogether or put in a cloud. But these were in bathrooms, so improved acoustic isolation was useful, but not crucial. The main goals were to be able to place insulation on top of them, and getting a proper fire rating back in the ceiling is actually very reassuring.

P.S. Stuart, I intended to post this in the Studio Construction sub forum, but ended up here by mistake. Please feel free to move the post there.

Cheers,
Jennifer

[Gregwor]

Those housings don't look like they have much surface density. A solution would have been to build little square enclosures out of OSB (the correct thickness to achieve your needed surface density) to cover the lights. You could have then covered that with as much insulation as you need.

Greg

[Soundman2020]

P.S. Stuart, I intended to post this in the Studio Construction sub forum, but ended up here by mistake. Please feel free to move the post there.

Done!

Those should be much better than what you had, as you'll be able to get the missing insulation in now. Have you considered boxing them in from above? Even a simple wood box placed over all of them and sealed down with caulk would give yo a bit extra isolation. OK, so it's only a bathroom, but as you mentioned it did have its isolation issues before. Maybe now would be a good time to do something about that? Do you have space up there to work, to get a box in, or maybe build it in place?

Or maybe there's enough mass in those, and the seal is good enough, that you'll get the extra you were looking for.

- Stuart -

[endorka]

Nice to see you here Greg!

Thanks for the covering box ideas chaps, I hadn't though of that. Is it ok with the heat coming from the bulbs though?

Before I bought these I checked they were acoustic rated. I have only found a summary of the test online, you have to pay for the full document and it's quite expensive. It seemed quite thorough though, and as I had to replace the old halogens with LEDs anyway, thought they would be worth a punt;

The fittings conform to BS EN ISO 10140-2: 2010 & BS EN ISO 10140-3: 2010 + A1: 2015
"confirming that they maintain the ability for an internal or separating floor to provide sound insulation"

Abstract; https://www.iso.org/standard/42089.html
Summary; https://www.iso.org/obp/ui/#iso:std:iso ... ed-1:v1:en

I'd be interested to hear more details on this test procedure if anyone has the document.

Now that the downlight fittings are installed I've done some measurements and I think the claim has justification. As ever, I'd love to hear your thoughts on my ramblings

The bulb alone 25g has a 5cm diameter, so area is 19.64 cm2, giving an average surface density of 12.7 kg/m2. A bit better than 12.5mm plasterboard which is 8 kg/m2. So if it could be sealed in place, the ceiling acoustic integrity is preserved.

The downlight fitting is pretty massive, made from thick metal and fits flush to the plasterboard ceiling with a proper gasket. a couple of clips grip the drywall from the side, and two springs above hold it in place vertically;

There are holes at the top of the fitting, presumably to let heat escape. At first I was alarmed at this, but the bulb fits into another "sub fitting" with another bezel that then twists into this, providing an airtight fit;

The bulb is held firmly in place against the bezel, so the unit is properly sealed.

So it looks like the acoustic claim is theoretically plausible for a single layer of drywall. A box as you both described would be required for ceilings with more than one layer.

Of course the proof of the pudding is in the eating. I'll post acoustic test results once I've done them.

Cheers,
Jennifer

[Soundman2020]

The claims sound reasonable to me. As long as there's plenty of metal and good rubber seals. you should be good. I don't think that thing will get very hot: if it is LED, there should only be a few watts of heat, so I wouldn't be too worried about cooling. But once again, knowing your thoroughness Jennifer, I'm sure you-ll be up there checking on temperatures after having them turned on all day!

- Stuart -

[endorka]

Ha! I did indeed do exactly that

Cheers,
Jennifer