Block house airtightness

[vfrdave]

Traditional build here and have given some thought to airtightness. Internal wet plaster is effectively going to create my airtightness. I appreciate the wall/ceiling junction can crack and compromise the airtightness. The issue I have is that through choice in our bedroom block (circa 5.5m x 21m) we will have 34 spotlights. My question is therefore is it worth spending time on airtight membrane to then puncture it in so many places?

 

I will do windows and doors with tape.

 

Please don't send me to the firing squad.

[CC45]

Ive put a false ceiling in our bathrooms - creating a 100mm void to house spotlights.  The original ceiling heights were deliberately designed with this in mind.  The only other option is to use airtight hoods at ~ £10 each. The false ceilings are under the airtight membrane.

[dpmiller]

Batten out for a service void- what depth are the downlights?

[vfrdave]

@dpmiller This is a bit of a last minute effort.  Not sure I fancy the expense of battening out for a service void for the whole house.  Most of the 1st fix cabling is already in.  I have no idea what depth the downlights will be, haven't looked that far ahead.

 

Treading water to keep the day job going and the build and family time.

 

[Declan52]

You can buy expensive hood covers that sit on top of the plasterboard. Or I used clay plant pots from b&q. They where under a £1 each when I bought them. Think mine are about 30cm tall so plenty of room so the light never overheats.

Try to get the pots without the drainage holes but if they have none then a squirt of silicone and some of your tape covers the hole. You will need a grinder to cut a notch in the rim for any cables. A good bead of sealant will hold it in place and keep it sealed with extra around where the cables come out. 

[vfrdave]

2 hours ago, Declan52 said:

You can buy expensive hood covers that sit on top of the plasterboard. Or I used clay plant pots from b&q. They where under a £1 each when I bought them. Think mine are about 30cm tall so plenty of room so the light never overheats.

Try to get the pots without the drainage holes but if they have none then a squirt of silicone and some of your tape covers the hole. You will need a grinder to cut a notch in the rim for any cables. A good bead of sealant will hold it in place and keep it sealed with extra around where the cables come out. 

I remember reading about this before just couldnt remember who had done it.  So did you not use a membrane in the ceiling?

[Declan52]

Yeah used it as well as mine is a chalet bungalow so the membrane covered the entire roof section and was then glued to the floor and the blocks to create a fully sealed room. 

The pots where the easiest most cost effective (cheap!!) way I found I could do it.

[vfrdave]

3 minutes ago, Declan52 said:

Yeah used it as well as mine is a chalet bungalow so the membrane covered the entire roof section and was then glued to the floor and the blocks to create a fully sealed room. 

The pots where the easiest most cost effective (cheap!!) way I found I could do it.

Mine is a standard bungalow and just wondering with so many downlights should I just tape the plasterboard joints and the ceiling to wall junctions and put hoods/pots on the lights.

[Onoff]

13 minutes ago, vfrdave said:

I remember reading about this before just couldnt remember who had done it.  So did you not use a membrane in the ceiling?

 

I was most concerned about puncturing my continuous, draught free vcl:

 

 

But now with 4 downlights, 2 speakers, a rainfall shower head and bfo body dryer etc I think that ship has long sailed. Just doing the best I can to mitigate air/heat loss!

[Declan52]

19 minutes ago, vfrdave said:

Mine is a standard bungalow and just wondering with so many downlights should I just tape the plasterboard joints and the ceiling to wall junctions and put hoods/pots on the lights.

How much would the membrane cost to do your ceiling??? You will also have the glue that is needed to stick it to the blockwork to factor in.

 

It will be around the edges that the cracks will appear most so it's making sure it's done well here that is the most important. 

We had spots in our last house and the wind that came through them was unreal so you Definitely need to do something there.

[Dudda]

How are you ventilating the house? I'm guessing you don't have Mechanical Ventilation with Heat Recovery (MVHR) and it's just wall or window vents?

 

If in the unlikely event you do what Declan is suggesting and do it really well you could end up with the situation where your house is to airtight for natural ventilation. This is great if you've MVHR but if not you'll then need to install more wall vents. Not a big issue just something to be aware of.

[vfrdave]

I have MVHR installed (or nearly 1st fixed) so another penetration to deal with.

 

@Declan52 I would probably need 2 rolls to more than cover my bedrooms block so £336 going on gerband vario pricing plus the adhesive.   Then there is the other tape at £30 a roll to cover the membrane to allow it to be plastered.

 

It is more the time and hands required to put it up and how to deal with the electrician coming along with his hole cutter to put the lights in.

[Declan52]

Not really that much over the total cost of the house but it does take a bit of time to put up. It's an easier job with 2 people of you can get an extra pair of hands.

The sparks hole cutter will cut it and leave it raggy but the pot will easily cover it. 

[vfrdave]

Just resurrecting this thread I have done alot of the membrane and taped and glued to the walls.  To plaster over the membrane that is glued to the walls, what did you do @Declan52 tape it or expanded metal?

[Declan52]

I didn't use anything. Once the plasterboard was on it covered most of it. I had the membrane bent over to make a fold ,like a Z , where it went onto the wall This meant the roof and walls could each move when they dried out and not rip the membrane.  The rest was covered by the scrim cloth the plasterer put on.