Air tightness membrane "crackling in the wind"

[ProDave]

I'm close to finishing fitting the air tight membrane to our house.  Inside the house, the timber frame is clad in OSB sheet. The air tight membrane is stretched over, and then battens are fitted (following the positions of the studs in the frame) to both hold the membrane in place, and create a service void before the plasterboard goes on.

 

On a windy day like today, when there's a gust of wind, the membrane on one side of the house will "inflate" very slightly between the battens, and the other sode of the house it will suck tight too the OSB. In doing so you can hear a very faint "crackle" a bit like a rustling crisp packet, but very much quieter.

 

My concern is it's going to continue doing this, and will it be audible once the plasterboard is on?

 

Clearly there are some small air leaks in the frame, and the membrane is doing it's job of catching them. But although it's stretched as tight as I can, it's not elastic and not tight like a drum so will move a bit.

 

Anyone else noticed this? did the plasterboard shut the small sound in?

[Crofter]

I've noticed my membrane ballooning up too. I've been putting it down to having not finished all the detailing outside- cladding, soffets, etc- and have crossed my fingers that it won't be an issue once the exterior is more sealed up.

 

Another user on here suggested using pieces of insulation board as packers within the service void to help hold the membrane down.

[Stones]

I masked up our windows (polythene taped to the frames) and when the wind speed was high, I observed the effect you describe, polythene inflated on windward side, sucked to glass on leeward side. It really does highlight how much of an impact high windspeed has and the potential for wind driven heat loss.

 

Hopefully the plasterboard will dampen any related noise down.

[Crofter]

Another thought on this- is there a risk of the membrane fatiguing and eventually failing if it is going through thousands of cycles?

 

I really was quite surprised by how much air was getting through. I was very careful to foam up every joint and gap when I added a layer of PIR around the whole interior of the build.

[jack]

1 hour ago, ProDave said:

I'm close to finishing fitting the air tight membrane...

 

Until you've completed it, there's still the possibility of leaks through the unlined areas. Are all your windows and doors adjusted to be maximally airtight?

 

I can't say we've noticed any sound at all from our build-up (much like yours: airtightness membrane over 22mm OSB walls, held on with battens to form a service void).  

 

34 minutes ago, Crofter said:

Another thought on this- is there a risk of the membrane fatiguing and eventually failing if it is going through thousands of cycles?

 

If it's anything like the stuff we have, I doubt a bit of flapping will do it any harm.  It's seriously tough stuff.

[ProDave]

For me, the problem is worse in the sloping ceilings of the roof upstairs. There it is just the wood fibre sarking board and an insulated timber frame. There's also the small matter of 2 velux windows not yet fitted so an obvious great big hole to let air in between the frame and the membrane. Obviously it will be a lot better when those are fitted and sealed up.

 

Downstairs where the wood fibre is rendered and all windows are in and sealed, it hardly inflates anywhere at all.  But it is certain there will be some air leak somewhere so I was concerned this might continue and be audible.

 

I might look at an extra row of battens in between the ones that are there to reduce the "span" between supports so to speak.

[CC45]

Ours inflates with the wind.  We use horizontal battens - behind which Ive packed some foam backers which have helped.  PIR is jammed between these battens.  I cant hear our membrane.