Non-breathable v breathable membrane on timber frame

[hayfordhillbilly]

Hello all.

I'm having an ancillary building erected in the back garden, complying with building regs etc as it'll eventually be habitable. Building warrant in place and planning secured. It's a timber frame construction, which will be clad in larch (board on board style, horizontal, with counter battens).

The builder has mistakenly wrapped the structure in Protect VC Ultra foil (non-breathable), with an additional vapour layer internally between the insulation and plasterboard). He thought the VC foil was breathable. You live and learn, I suppose.

Building control have picked up on it, stating that it has to be breathable. Given that a lot of the cladding is on, it's going to be a royal pain to remove it all and re-wrap using a breathable membrane.

Question: is there any way I can turn the non-breathable membrane into a breathable one by some means of adapting, or is it a case of rip it out and do it again? I'm resolved to the latter, but wondered if there's anything we could do.

Thanks,

 

[freddiemercurystwin]

Rip it off.

 

[hayfordhillbilly]

Rip it off.

Yes, we do think that's going to be the only way, but was just curious.

 

[mrrusty]

It has to come off if you have non-breathable on the cold side. If you think about it, you wouldn't want it anyway!. It's supposed to be non-breathable on the warm side and breathable on the cold side.

The non breathable helps to keep the warm air inside the room, and the breathable ensures any water vapour that does get in to the wall structure doesn't condense in the wall structure/inside of the membrane, but can pass through and be evaporated in the ventilated cavity behind the cladding.

 

[hayfordhillbilly]

It has to come off if you have non-breathable on the cold side. If you think about it, you wouldn't want it anyway!. It's supposed to be non-breathable on the warm side and breathable on the cold side.

The non breathable helps to keep the warm air inside the room, and the breathable ensures any water vapour that does get in to the wall structure doesn't condense in the wall structure/inside of the membrane, but can pass through and be evaporated in the ventilated cavity behind the cladding.

Sure. I understand that. It was genuinely a case of believing the non-breathable membrane was breathable when it was installed.

 

[freddiemercurystwin]

Dare we ask who's cock up was?

 

[hayfordhillbilly]

Dare we ask who's cock up was?

The builder's. But he's a good friend, so it's tricky.