Downlighters - Air Tight Seals

[FraserK]

Been in our self-build 18 months and always noticed there being a slight draught on windy days and there’s sometimes a condensation ‘spot’ on one of the windows. House was built for us by local builder and has been signed-off by BC, completed EPC etc.

 

We have 12 eyeball downlighters on an angled roof and curiosity got the better of me - dropped the light to find that they had been installed by cutting through the foam roof insulation and roof membrane, leaving a draughty void behind.  Before I go back to my builder to ask them to put it right, what is the solution I need to ask for?

[ProDave]

What was your spec for the house?  What was the EPC rating? and air tightnes of you had a test done?

 

What communication happened between you, the builder and the electrician?  Who specified the lights?

 

Most of us on here, if asked first would have told you not to fit recessed spotlights in that roof structure, it is virtually impossible to make them airtight, especially if you want swivel ones.    We would either have advised changing the roof structure, or fitting some other form of lighting?

 

 

[saveasteading]

Although you probably don't need fireproof enclosures, they could be the solution.

Little fabric bags over the lights, sealed down somehow, with mineral wool, or at least something,  over them. 

This all done from below, which will require some thought.

[FraserK]

Thanks for your replies. The house was built during lockdown on the Isle of Mull, so we didn’t get the chance to inspect the build in detail  and many details like these lights were left to the builder so as not to delay the build and we had no reason to think they hadn’t been installed correctly. There wasn’t a physical air-tightness test as far as I know - it was done using a simulation/estimate of 7m3/h/m2. I’ve seen some plastic cowlings, Thermahood, so will look to fit them.

[Alan Ambrose]

There's some downlighter insulation thingies that might be useful. Not seen any that install from below, but it's not impossible. If working from above: this kind of thing:

 

https://www.wickes.co.uk/Loftleg-Loft-Lid-Downlight-Protector-Hood/p/148851

 

... and then patch the insulation and membrane? 

 

Alan

[S2D2]

4 minutes ago, Alan Ambrose said:

this kind of thing:

 

https://www.wickes.co.uk/Loftleg-Loft-Lid-Downlight-Protector-Hood/p/148851

I've used these in a traditional loft space, if you apply attention to detail with the sealant covering all cable entries etc they give an airtight seal. Remember to seal the cable with extra slack so the downlight can still be pulled downwards if required. Unsure on your roof structure though as you should insulate above them.

[Onoff]

I have to do some "reinstatement". I've compromised my vcl in so many places: 

 

 

The fire hood will be stuck down where it's rim meets the foil/vcl:

 

 

 

 

Edge of foil and vcl:

 

 

With hindsight I'd have done a suspended ceiling!

[Jilly]

1 hour ago, ProDave said:

 

Most of us on here, if asked first would have told you not to fit recessed spotlights in that roof structure, it is virtually impossible to make them airtight, especially if you want swivel ones.    We would either have advised changing the roof structure, or fitting some other form of lighting?

 

 

I’m just at this point with a flat cold roof. We’ve got 150mm PIR between the joists, 40mm overboard then the plasterboard. What would you recommend, and more importantly, how exactly should I ask the builder to do it, please 😊? I was thinking very thin profile downlighters. The room will be dark as near trees. 

We have wires dangling through single holes atm. He has use Al tape on the joins of the 40mm layer We could pull it all out if you think it’s a really bad idea…

[Onoff]

5 minutes ago, Jilly said:

I’m just at this point with a flat cold roof. We’ve got 150mm PIR between the joists, 40mm overboard then the plasterboard. What would you recommend, and more importantly, how exactly should I ask the builder to do it, please 😊? I was thinking very thin profile downlighters. The room will be dark as near trees. 

We have wires dangling through single holes atm. He has use Al tape on the joins of the 40mm layer We could pull it all out if you think it’s a really bad idea…

 

You could counter batten at this point. First foil tape all the joists and PIR joints. Make sure the wires coming through are sealed. Counter batten deep enough to suit low profile downlights then plasterboard.

 

It's what I should have done.

[FraserK]

Fortunately the wires run between the plasterboard and the membrane, so thinking I should be able to fit the hood/cowl directly into the insulation (dab of expanding foam to secure) and then tape the membrane around the edge?