What are the "air scoop" things on my roof for?

[Martin Angove]

Two on each side of the roof, look like the fake air scoops people fit to their 1.2l Corsas after the wobbly "spoiler". They are in place of a couple of tiles, and there is absolutely no evidence of them in the attic - the under felt is continuous.

Houses were built in the 1930s, ours has had a new roof maybe 15 or 20 years ago, fibre slates (originals were slate slates). Other houses in the road with both newer and older roofs don't all have these, though some do. Next door attached has a roof no more than 5 years old I reckon; they have no air scoops. Next door not-attached has what could be an original roof. Again, no air scoops.

Just interested really :-)

Hwyl!

M.

[The Natural Philosopher]

Ridge vents,to let moist air out and swallows in.

If the sarking is continous and impermeable, I suppose it ventialtes the battens!

[Martin Angove]

Ta, though they're about half way up the roof, not at the ridge.

Certainly seems to be - that tarry stuff. Looks like shed felt without the green sand. Hmmm...

Hwyl!

M.

[Mike]

One of these installed wrongly perhaps ? Or something else like it ?

[mindwipe]

are these any good? how much? anyone used them?

[keith_765]

Fibre cement slate condensate. The vent slate is put there to vent between the underside of the slate and the underlay felt. If not used you sometimes get white streaks running down the roof at the top from under the cement fibre slates. if you read the Eternit laying booklet it explains this as a must. The same vent slates are also used to vent the roof space as well its only a matter of cutting a cross diagonally and folding the felt out wards to reveal the vent opening.