Air tightness layer & Wind tightness layer: whats the difference ?

Calahonda52

I think I know the answer but am having a "discussion" with a builder about it.

I won't share his ideas here, just wondering can someone pen a few lines on the difference that I can use rather than just tell him what I want and tell him either do it or .....
Thanks

Strolling Bones

air tightness measures tend to take place on the warm side of the insulation layer.
wind tightness - to the cold side

Calahonda52

Thanks.
Its a bit unusual as the insulated structure is inside a rain-screen which is ventilated top and bottom.
There is a walkway between the rain-screen and the insulated structure.

Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition, which is insulated, between the studs with 100 mm alu covered, on both sides, rigid "poly" insulation.
All joints taped and taped over the studs from the walkway.

Builder's view is that the painted mdf and the taped alu covered insulation is good enough for the air-tightness and the rain-screen does for wind-tightness so no need for any "expensive" membranes

BryanF

Calahonda52 wrote: »

Thanks.
Its a bit unusual as the insulated structure is inside a rain-screen which is ventilated top and bottom.
There is a walkway between the rain-screen and the insulated structure.

Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition, which is insulated, between the studs with 100 mm alu covered, on both sides, rigid "poly" insulation.
All joints taped and taped over the studs from the walkway.

Builder's view is that the painted mdf and the taped alu covered insulation is good enough for the air-tightness and the rain-screen does for wind-tightness so no need for any "expensive" membranes

set your required air-tightness level, get a tester of your choosing to test before the builder has closed anything up. What had your arch shown in the detailing? Is mdf on inside? Is it adequate to act as a vapour control layer aswell as AT layer?

Strolling Bones

Calahonda52 wrote: »

Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition,

No vapour check?

Calahonda52 wrote: »

Makeup of insulated structure, 100 mm deep metal stud partition, which is insulated, between the studs

Straight trough repeating thermal bridge. Really really bad.

Calahonda52 wrote: »

with 100 mm alu covered, on both sides, rigid "poly" insulation.
All joints taped and taped over the studs from the walkway.

How durable is that ? Tapes and inslaution will degrade with passing traffic.

Calahonda52

SB, Thanks
No vapour check and two out of two for the others!