Are spot lights in the ground floor ceiling and issue for Airtightness

murphy31ie

Hi,
I am wondering if anyone can help me out with info on downlighters on the ground floor ceiling (building 2 story). We are trying to airtight the house as much as possible and been told to stay away from any recessed lighting (downlighters). I know you don't want downlighters in the second floor ceiling due to airtightness issues but will downlighters cause any airtightness or insulation issues if put in the ground floor ceiling.
Thanks for any info
Brendan

Rabbo

No, it's normally not a concern on the ground floor ceiling as it doesn't form part of the airtightightness envelope

MicktheMan

Depends on whether a good air tightness strategy was employed or not when the house was built.

If not then recessed light fittings will leak like a sieve (unless the more expensive fire rated fittings are used and installed carefully).

BarneyMc

I don't understand why down lights would be an airtight issue on the ground floor as it doesn't go near the air tight envelope. Also, if a void is left under the air tight membrane on the first floor then I can't see why it would be an issue here either.

murphy31ie

Hi MickMan, I would only be putting the down lighters in the ground floor ceiling, could you explain how this would effect the airtightness as it will be inside the airtight envelope.

MicktheMan

BarneyMc wrote: »

I don't understand why down lights would be an airtight issue on the ground floor as it doesn't go near the air tight envelope.

You are assuming there is a (proper) "air tight envelope" to begin with! There is no information given regarding this.

Johnnydoe99

Sparkle here
Just a correction oon s

MicktheMan

murphy31ie wrote: »

Hi MickMan, I would only be putting the down lighters in the ground floor ceiling, could you explain how this would effect the airtightness as it will be inside the airtight envelope.

Ah, so you will be air tightening the building. Good.
What type of 1st floor will you have and how have you continued the air tight barrier from ground floor wall to 1st floor wall? If this detail is done correctly, then no worries, put as many recessed fittings in as you like.

Johnnydoe99

Spark here

Fire rated spots are not airtight if you are fitting them

They have an intumescent seal but allow air through

MicktheMan

Johnnydoe99 wrote: »

Spark here

Fire rated spots are not airtight if you are fitting them

They have an intumescent seal but allow air through

I was in the electrical wholesalers yesterday and was told (and shown one) that they were airtight. I hear what you are saying, but the one I was shown was a hell of a lot more airtight than you standard fitting. It was also a led only light. I can't recall the exact make etc but it looked quite good. If I'm in again I will get more detail. Thanks

murphy31ie

MicktheMan wrote: »

Ah, so you will be air tightening the building. Good.
What type of 1st floor will you have and how have you continued the air tight barrier from ground floor wall to 1st floor wall? If this detail is done correctly, then no worries, put as many recessed fittings in as you like.

Hi Mick,
Thanks for the info, I don't know the full spec of the airtightness off hand, my dad is looking after the whole thing as he is a retired contractor. From what I remember, we have 150mm insulation in the floor, 150mm pumped cavity and 62.5mm dry lining on external walls (I know we messed up there and should have just had a 250mm cavity and done away with the dry lining). 60mm insulation in the first floor, 400mm in the attic along with a air tight membrane. All windows, doors, ducts, service pipes, cables etc to be sealed and taped. All floor to wall and ceiling to wall joints to taped, not too sure on that one. Triple glazed windows and no chimneys or any vents in the house. We will be installing a MHRV system.

BryanF

Murphy,
You don't need to worry about air-tightness on ground floor ceiling assuming you have an air-tight envelope. Nothing you have mentioned so far suggested you have an air-tightness philosophy though.

MicktheMan

murphy31ie wrote: »

Hi Mick,
Thanks for the info, I don't know the full spec of the airtightness off hand, my dad is looking after the whole thing as he is a retired contractor. From what I remember, we have 150mm insulation in the floor, 150mm pumped cavity and 62.5mm dry lining on external walls (I know we messed up there and should have just had a 250mm cavity and done away with the dry lining). 60mm insulation in the first floor, 400mm in the attic along with a air tight membrane. All windows, doors, ducts, service pipes, cables etc to be sealed and taped. All floor to wall and ceiling to wall joints to taped, not too sure on that one. Triple glazed windows and no chimneys or any vents in the house. We will be installing a MHRV system.

Who is advising your dad on air tightness and what is your air tightness target? You haven't mentioned how the walls will be air tightened nor how the continuity will be achieved between floors. If this isn't addressed then by the look of things, your recessed fittings may very well leak (and every other penetration of the ground floor ceiling and 1st floor floor).

Unless your dad has experience in air tightening a house, then there is a very real possibility that you won't achieve a good result, your mvhr will underperform and you will still suffer severe heat loss by air infiltration.

BarneyMc

murphy31ie wrote: »

Hi,
I am wondering if anyone can help me out with info on downlighters on the ground floor ceiling (building 2 story). We are trying to airtight the house as much as possible and been told to stay away from any recessed lighting (downlighters). I know you don't want downlighters in the second floor ceiling due to airtightness issues but will downlighters cause any airtightness or insulation issues if put in the ground floor ceiling.
Thanks for any info
Brendan

I think your fixation on downlighters causing air tightness issues is a red herring. Lots of things can cause air leakage but downlighters should not if you've a strategy in place.

murphy31ie

MicktheMan wrote: »

Who is advising your dad on air tightness and what is your air tightness target? You haven't mentioned how the walls will be air tightened nor how the continuity will be achieved between floors. If this isn't addressed then by the look of things, your recessed fittings may very well leak (and every other penetration of the ground floor ceiling and 1st floor floor).

Unless your dad has experience in air tightening a house, then there is a very real possibility that you won't achieve a good result, your mvhr will underperform and you will still suffer severe heat loss by air infiltration.

The walls will be scratch coated to seal the blocks, as I said I don't know the exact detail of the continuity between the floors. Assuming we have the correct detail in the continuity between the floors, sealing the blocks by scratch coating, taping all doors, windows, service ducts etc, airtight membrane in the roof space are missing anything?

Strolling Bones

murphy31ie wrote: »

will downlighters cause any airtightness or insulation issues if put in the ground floor ceiling.

They will cause the spread of fire and smoke if you don't install something like this

murphy31ie

BarneyMc wrote: »

I think your fixation on downlighters causing air tightness issues is a red herring. Lots of things can cause air leakage but downlighters should not if you've a strategy in place.

Fixation, seriously. I know the airtight envolpe needs to be good and if it isn't all the downlighters in the world won't make a difference. I asked the question would downlighters in the ground floor ceiling have an impact assuming there is a sound airtight envelope. Now you are saying I have a fixation

BarneyMc

murphy31ie wrote: »

Fixation, seriously. I know the airtight envolpe needs to be good and if it isn't all the downlighters in the world won't make a difference. I asked the question would downlighters in the ground floor ceiling have an impact assuming there is a sound airtight envelope. Now you are saying I have a fixation

OK, not a fixation then but not sure why you're so worried about downlighters at this stage. In an old house or new build with no airtight strategy they might be a problem. On the first floor, without a membrane in place, they could be a disaster.

Would downlighters in the ground floor ceiling have an impact assuming there is a sound airtight envelope? No. Your ground floor ceiling is not your airtight envelope.

JonathonS

Strolling Bones wrote: »

They will cause the spread of fire and smoke if you don't install something like this

Nothing as robust as that required if he installs ( a quality brand of) LED downlights, which is a no-brainer given the electricity savings over halogen.

Strolling Bones

JonathonS wrote: »

Nothing as robust as that required if he installs ( a quality brand of) LED downlights, which is a no-brainer given the electricity savings over halogen.

So how would an led fitting prevent the spread of fire from the lower storey into the cavity of the floor structure?

MicktheMan

murphy31ie wrote: »

The walls will be scratch coated to seal the blocks, as I said I don't know the exact detail of the continuity between the floors. Assuming we have the correct detail in the continuity between the floors, sealing the blocks by scratch coating, taping all doors, windows, service ducts etc, airtight membrane in the roof space are missing anything?

All junctions of the external envelope should be taped/sealed including f.i. wall to floor.

Also an air tightness target should be set and a preliminary test to measure actual air tightness after all elements are sealed but before any slabbng / internal finishes are started. This will give you peace of mind that all is ok and if not, an opportunity to remedy before its too late.

murphy31ie

MicktheMan wrote: »

All junctions of the external envelope should be taped/sealed including f.i. wall to floor.

Also an air tightness target should be set and a preliminary test to measure actual air tightness after all elements are sealed but before any slabbng / internal finishes are started. This will give you peace of mind that all is ok and if not, an opportunity to remedy before its too late.

Thanks for your info again Mick, yeah we have planned for an airtightness test before the plastering inside, the tester also has a thermal imaging camera.

JonathonS

Strolling Bones wrote: »

So how would an led fitting prevent the spread of fire from the lower storey into the cavity of the floor structure?

Choose one that's fire rated.

Strolling Bones

JonathonS wrote: »

Choose one that's fire rated.

You should post more here. Lots more.

Strolling Bones

JonathonS wrote: »

Choose one that's fire rated.

You should post more here. Lots more.

JonathonS

Strolling Bones wrote: »

You should post more here. Lots more.

So good he said it twice.

Not everyone will be aware of the asbestos potato sack you recommended, or of fire rated downlighters, so lets both keep posting?

Strolling Bones

JonathonS wrote: »

So good he said it twice..
Not everyone will be aware of .... fire rated downlighters

I wasn't so I checked it out.
Apologies and thank you.


I wasn't so I checked it out.
Apologies and thank you.