roof insulation and ventilation query

[nrgserv]

not my usual subject, but doing the research....

after reading loads on insulating between roof purlins, leaving air gaps and eaves clear of woolly dog, my predicament is;

the house is ex metro with concrete gutters (pics lower down) and there isnt an air gap in the soffit to start with. the felt thats in place, i cant tell if its breathable or not, and there is no vents to the ridge.

plan is to insulate and board, and i i am scratching my head now whether to fill between the purlins with rockwool and board over (no airgap) or to cut 50mm kingspan to fit between them (purlins 50x75) and have a 25mm air gap. if i do it this way, ridge vents wont be too much of a problem, but do i need to sort a soffit vent? this would be the harder part, or can you get vented tiles?

and the pics....

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• nrgserv
• 20 May 2011
• 2

a general view of the concy gutter

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• nrgserv
• 20 May 2011
• 2

a close up of the gutter membrane
(with hole that i need to sort out as well)

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• nrgserv
• 20 May 2011
• 1

looking from inside at the purlins and other half of concy gutter.
the bottom plastic sheet goes all round gutter to outside, as
previous image.
can anyone tell if the felt's breathable or not?

Untitled

• nrgserv
• 20 May 2011
• 1

cross section sketch of how its set out.

more pics available if anyone needs any, with close ups.

cheers for any advise / info, will be back later!

 

[freddiemercurystwin]

Yes you can get tile vents, place a few each side of the roof as low as possible but above any insulation. Or have i missunderstood and you are planning to plasterboard over the refaters? In which case you need ridge vents aswell and a min gap of 50mm.

Looks like trad felt to me so not breathable.

 

[nrgserv]

ace, cheers for the reply!
yes, planning to board, just to answer the misunderstood bit.

kingspan it be then, with top and bottom vents.

i'll thank you when i find out how to do it!

 

[freddiemercurystwin]

http://www.insulation.kingspan.com/uk/pdf/k7.pdf

 

[nrgserv]

fig 2a and 5a is what i'm aiming for, it was the unbreathable sarking and lack of soffit ventilation i have that caused the original questions.

cheers for the link, i found it earlier when i was researching but still re read it, as it brought some of the terminology back that i'd forgotten!

what i'm after next, is vent tiles for the eaves and ridge vents.
any idea what type of tile i have, and what its called?

oh, and a reasonbly priced outlet for vents and kingspan in yorkshire!

cheers for taking time to read, if only beer could be emailed!

 

[freddiemercurystwin]

Posting in the Builders section may give you a good source for your insulation, post in the Roofing section if you want to identify your tiles.

 

[nrgserv]

Posting in the Builders section may give you a good source for your insulation, post in the Roofing section if you want to identify your tiles.

of course! ta muchly

 

[misterhelpful]

The tiles look like Redland Renown (same as mine) and I have universal vents like these VENTS but if you look around you can get others which match the tiles.