Double-ventilated roof?

[KungGeorge]

Hello!

We are facing a roof renovation and have received a couple of quotes. It's regarding a gable roof, 30 degrees with an attic and roof board in good condition. The chimney and one vent are the only penetrations. The initial plan was a classic renovation, removing tiles, battens, and underlay, and then replacing them in the same order.

This week, we had a roofing contractor here who proposed a "double-ventilated roof replacement." That is, removing the tiles and battens but leaving the old underlay. Then, as I understand it, a generously sized support batten and plastic sheet are installed, followed by counter battens and tiles. I have understood that Älvsbyhus has skipped the roof board and uses plastic instead, which has been debated. However, has anyone heard of a combination of roof board, old underlay, and plastic sheet? He called it a double-ventilated roof since it creates double air gaps.

Overall, they gave a very professional impression and seem to have been operating in the Stockholm region for a long time.

Thanks!

 

[Workingclasshero]

Never heard of a double-ventilated roof.
Plastic as a drip guard under my metal roof is what I have on the garage, mostly because I didn't know better and lacked money, yet the stretched plastic is just as nice and taut today 27 years later.
Personally, I would probably change the roofing felt to the best one and then use rafters and lay tiles or metal sheets.

 

[Nikorasu]

Hello!

We are facing a roof renovation and have taken a couple of quotes. It concerns a pitched roof. 30 degrees with cold attic and raw wood in good condition. Chimney and one ventilation are the only penetrations. The idea was a classic overhaul, removing the tiles, battens, and felt, and then reinstalling in the same order.

This week, we had a roofing contractor here who suggested a “double-ventilated roof replacement.” So, removing the tiles and battens but leaving the old felt. Then, as I understand, a generously sized support batten and plastic sheet are installed, followed by counter battens and tiles. I’ve understood that Älvsbyhus has skipped the raw wood and uses plastic instead, which has been debated. But has anyone heard of a combination of raw wood, old felt, and plastic sheet? He called it a double-ventilated roof as it creates double air gaps.

They gave a very serious impression overall and seem to have been around in the Stockholm region for a long time.

Thanks!

If you are still going to remove all the tiles and battens, why on earth wouldn't you do the little job of replacing the felt? It’s the felt that is the most important for providing a tight roof.

Avoid complicating things, I say. If the roof is in bad condition, repair with the same construction you’ve had.

 

[Matti_75]

Instead, consider insulation above the råspont to create a warm attic. What the company is suggesting is just nonsense.

 

[KungGeorge]

Thank you for the quick response. Spontaneously, it feels a bit crazy, but I thought this might be a new yet proven way to renovate the roof. If no new info emerges, it will probably be a classic replacement of felts, battens, and tiles from one of the other quotes.