Ventilation of roof. Eaves to eaves

[Aunty]

I am not a carpenter and have absolutely not studied the historical technical development of buildings.

A roof is not a waterproof layer. It is part of the building envelope.

You repeatedly say "you don't understand xxxxxx" and "I don't think you understand xxxxxx". I think you should explain instead.

Why would they be two different things? Explain where the difference lies.

And...sources for what you claim, please.

https://www.fuktcentrum.lth.se/fileadmin/fuktcentrum/Publikationer/Bygg-Teknik/2_00_49.pdf

 

[Aunty]

[link]

"Building roof structures without an air gap is becoming increasingly common today. You get faster drying of construction moisture and a healthier roof structure over time. This time in the tape school, we talk about which products to use when you have a roof structure with roof tiles and want to avoid the work of creating an air gap."

-Sjömarkens insulation

 

[Aunty]

"A roof structure suitable for houses for sustainable building, such as passive houses and Multi-Comfort Houses. When insulating pitched roofs and support legs with boards, ISOVER Bjälklag/Metal stud board 36 c1200 (replaced by ISOVER UNI-board 35) can be used."

-Isover

 

[Aunty]

can continue as all research says the same, and much of what is being built now is being built without an air gap in the roof.

then the fact that someone has worked for 10 years and doesn't know this is probably rather tragic and a pity for everyone affected by someone who doesn't want to do the right thing

 

[Cancerman_777]

can continue for all research says the same, and much of what is being built now is being built without an air gap in the roof.

then that someone has worked for 10 years and does not know about this is rather tragic and a pity for everyone affected by someone who does not want to do right

Interesting. You learn something new every day.

 

[Rickard.]

My world is not so black and white and easily explained, but you mistake me for someone who actually decides this when it's choices that designers at companies like NCC and Peab make despite all the information you provide. I have nothing to do with it, but I do get to see when it works and also if something doesn’t.

 

[Aunty]

My world is not so black and white and easily explained but you mistake me for someone who actually decides this, but these are choices made by educated designers at companies like NCC and Peab despite all the information you put out. I have nothing to do with it but get to see when it works and also if something doesn't.

I work with this daily and know many educated people at NCC and Peab you mention who would never design a ventilated space in a roof as they know it is not good.

But your reasoning falters a bit because I also know many designers at NCC and Peab who have designed risky constructions that were later banned, for example, single-stage sealed thin-plaster facades on wooden structures.

 

[Aunty]

Interesting. You learn something new every day.

you don't have to believe me but at least look it up, if you have other research or studies showing that I'm wrong, please present them so I can be convinced of your reasoning.

 

[Rickard.]

I work with this daily and know many trained at NCC and Peab as you mention who would never draw in an air gap in a roof as they know it is not good.

We are a bit behind up here in the north so I'll see if anything changes in the future

 

[Cancerman_777]

you don't have to believe me but at least check it out, if you have other research or studies proving me wrong, please present them so I can be convinced of your reasoning.

Your argument was strengthened by the document from the moisture center. No, as I said, I'm not that well-versed in the subject and have relied/am relying on old truths that don't seem applicable in today's construction techniques.

 

[eleson]

... fourthly, an air gap will lead to increased moisture load in the roof as moist air will travel into the air gap and condense against the cold underside of the raw ridge board.

How so?
The air moving in the air gap comes from outside and is therefore already cooled, so why would it condense?

 

[eleson]

[link]

So the document points out the advantages of a diffusion-open sub-roof?
Many would probably agree.
But just saying that it's better to remove the air gap in a roof construction feels risky, to put it mildly.

 

[plåtrickard]

How so?
The air moving in the air gap is from outside, and is already cooled, so why would it condense?

I am also curious about that, if it is both well-insulated and airtight with plastic?

 

[plåtrickard]

By the way, I also have not been on a new build without an air gap..
Except for porch roofs..
But I mostly work with old houses

 

[Cancerman_777]

So the document points to the advantages of a diffusion-open subroof? Many would probably buy that. But just saying that it's better to remove the air gap in a roof construction feels risky, to put it mildly.

What? No. That's absolutely not how I understood it. On the contrary. Sure, I skimmed through it, but I understood it as two dense layers. Nothing with diffusion-open or anything else, because then you're introducing moisture. That was the whole point; no moisture is introduced from the living space or the outdoor environment.