If you are going to have double weather barriers, i.e., both asfaboard and weather barrier fabric, it feels better if there is a bit of space between them, like 45mm in this case, a gap that is also insulated.
Compared to having both weather barriers closely together, where it feels like any moisture could more easily "get trapped" in between, or rather that water vapor "binds" between the layers if they lie too closely together.
It's somewhat like two wet towels. They dry faster if they are hung up with a gap between them than if they hang closely together.
Compared to having both weather barriers closely together, where it feels like any moisture could more easily "get trapped" in between, or rather that water vapor "binds" between the layers if they lie too closely together.
It's somewhat like two wet towels. They dry faster if they are hung up with a gap between them than if they hang closely together.
I don't think it matters much where the extra layer is placed.
All 3 cases should work.
Your solution makes it feel less like "kaka på kaka", but whether it makes any practical difference compared to the other options, I'm a bit doubtful. However, I don't have anything substantial to base that on.
All 3 cases should work.
Your solution makes it feel less like "kaka på kaka", but whether it makes any practical difference compared to the other options, I'm a bit doubtful. However, I don't have anything substantial to base that on.
Extension builder
· Onsala
· 2 023 posts
Hello,
Facing the same decision when we re-panel our house in the spring. I have decided to go with Asfa (existing) and diffusion-open windscreen, primarily to compensate for existing damage, but also to protect against further damage and to ensure a completely windproof house while we're at it. I plan to place it directly on the Asfa, and I'm not particularly worried about moisture.
Facing the same decision when we re-panel our house in the spring. I have decided to go with Asfa (existing) and diffusion-open windscreen, primarily to compensate for existing damage, but also to protect against further damage and to ensure a completely windproof house while we're at it. I plan to place it directly on the Asfa, and I'm not particularly worried about moisture.
Found this thread because it is becoming relevant for me. I'm in the process of tearing down exterior walls & considering reusing the asfaboard. But since it's old with small holes, I'm thinking of adding a wind barrier on top. After reading the thread, that's probably how it'll be.
Yes, it's easiest to leave the asfaboard in place and simply add a layer of asfapapp/wind protection.
That's how I planned to do it when I replaced the panel on a southwest gable. However, the asfaboard was nearly 40 years old, and it was sometimes impossible not to damage it with the crowbar when removing the panel. (The panel was flush against the asfaboard, meaning no nail battens.)
The old asfaboard was brittle. It broke easily when handled and bent slightly. Not at all as tough as the new one. However, this wasn't a problem as long as it was mounted on the wall. Nonetheless, the old board was too damaged for reuse and was therefore sent off to the recycling center, and new was purchased.
The advantage of needing to remove the old asfaboard was that the underlying construction (frame and sill) could be inspected. It was reassuring to see that the sill was on sill paper and was completely healthy. Likewise, the studs and insulation, especially under the windows, were also perfectly fine. No significant moisture intrusion through the asfaboard seams, in other words. One might have expected that, given that the outer panel was so poorly covering due to warping, leaving long gaps to the asfaboard directly underneath. So, despite copious amounts of driving rain over the years, the asfaboard handled the task brilliantly.
For my part, I took the opportunity to add 45 mm of insulation to the facade. I replaced the old asfaboard with asfapapp, specifically as enhanced wind protection. Then, 45 mm studs and insulation were added, and on top of that, new asfaboard. All seams of the asfaboard were placed over studs, and narrow strips (5-10 cm) of asfaboard were nailed over the seams.
The new panel has a 12 mm air gap. This should reduce the strain on the asfaboard. It's more than sufficient in a windy position where the wind presses air through every board seam, yet adequate to prevent any significant amount of free water from running on the board.
Time will tell how well it works in various respects.
That's how I planned to do it when I replaced the panel on a southwest gable. However, the asfaboard was nearly 40 years old, and it was sometimes impossible not to damage it with the crowbar when removing the panel. (The panel was flush against the asfaboard, meaning no nail battens.)
The old asfaboard was brittle. It broke easily when handled and bent slightly. Not at all as tough as the new one. However, this wasn't a problem as long as it was mounted on the wall. Nonetheless, the old board was too damaged for reuse and was therefore sent off to the recycling center, and new was purchased.
The advantage of needing to remove the old asfaboard was that the underlying construction (frame and sill) could be inspected. It was reassuring to see that the sill was on sill paper and was completely healthy. Likewise, the studs and insulation, especially under the windows, were also perfectly fine. No significant moisture intrusion through the asfaboard seams, in other words. One might have expected that, given that the outer panel was so poorly covering due to warping, leaving long gaps to the asfaboard directly underneath. So, despite copious amounts of driving rain over the years, the asfaboard handled the task brilliantly.
For my part, I took the opportunity to add 45 mm of insulation to the facade. I replaced the old asfaboard with asfapapp, specifically as enhanced wind protection. Then, 45 mm studs and insulation were added, and on top of that, new asfaboard. All seams of the asfaboard were placed over studs, and narrow strips (5-10 cm) of asfaboard were nailed over the seams.
The new panel has a 12 mm air gap. This should reduce the strain on the asfaboard. It's more than sufficient in a windy position where the wind presses air through every board seam, yet adequate to prevent any significant amount of free water from running on the board.
Time will tell how well it works in various respects.