Just had the estimator round to get the loft insulation topped up. Particularly because of the very shallow pitch of the roof I'm concerned that the 250mm insulation will block the natural ventilation round the eaves.
What methods are the installers likely to use to get round this, and how do I check they've done it?
What is the roof covering? Is sarking present? What is the sarking made from?
Christian.
I've just been working in among the rockwool in my shallow pitched roof. Horrible, itchy experience. I don't know how much ventilation occurs naturally up there via the eaves but I do know that with an airbrick in each opposing gable wall, there's a pretty constant and very noticeable breeze. Do you notice much air movement if you stick your head above the parapet? If so, you could make sure there's a similar effect after they've finished the job. If there's noticeable air movement on a lightly breezy day, it should indicate a significant amount of ventilation eh?. I certainly wouldn't want to crawl around in the stuff any more than necessary if it's rockwool or fibreglass. Perhaps you've gone for the more literary type material?
The message from "Christian McArdle" contains these words:
Late 60s early 70s Marley (type) tile roof with felt sarking.
Ask the insulation contractor not to push the insulation up to the back of the felt underlay, leave a 25mm gap from the felt. If the insulation is pushed up to the felt underlay, the alternative is to fit vent tiles above the height of the insulation every 1.6 metres both eaves to cause an air cross flow. There are GRP vent tiles to fit all concrete Marley, Sandtoft, Redland and Russell tiles, both plain and interlocking. Just take out the tile cut the underlay, fold back or inwards and replace the tile with a vent tile.
K,S Notts
For what it's worth, 50mm (2") gap is the norm in England [1] (and reckoned to be a fairly safe bet, combined with sufficient ventilation top and bottom) - probably to allow a bit in case the sarking sags.
Cheers
Tim
[1] obvious building regulations/codes are different, but rot doesn't respect borders ;->
Ignore the "UK" bit - for some reason I thought I was posting to an international group :~ Need beer...
50mm is still recommended though...The message from "keith_765" contains these words:
Some of the houses round here which have had mucho insulation fitted have these.
What about eaves trays?
To fit eave trays you have to take off the roof covering. Which type of eave vent system are you referring to.
1) Full eaves vent system including, over fascia vent strips, with felt vent support tray. 2) Over fascia vent in one.Which ever you use, you will have to take off about 600mm x length of the building, of roof covering at eaves level.
KS Notts
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