How to insulate an attic in a HRV house?

timmer3

this is a bit of a conundrum to me. everything you read about attic insulation/ventilation requires plenty of attic vents and leaving room for the air to circulate around the rafters etc. but in a HRV situation you don't want any holes in the house, so attic vents are out. so i'm thinking of using a highly breathable insulation like sheeps wool to completely fill the rafters and the eaves. with light wood panelling fixed to the rafters, leaving an air gap of 2mm or so between each panel. i'm expecting condensation to form on the inside of the roof felt, which risks rotting the timbers if the insulation stays wet. but i'm hoping the sheepswool will transmit the moisture back into the room, with the HRV keeping the attic air dry.
i intend to use the attic as a semi-warm room. it's got to be dry for storage and occasional habitability, one of the air supply ducts from the HRV (which is in the attic) can be opened to the attic itself.
can anyone point out problems with this, is there a better solution? i'd be slow to put a breather membrane anywhere, it seems risky to 'trap' that damp in to the insulation, even though the membrane is able to transmit moisture through it is still going to reduce the air/moisture flow substantially, especially if it's a diffusion open product like intello which is closed in one direction for half the year (if i understand correctly).

PirateShampoo

If you have the money then you should look into http://www.icynene.ie/

timmer3

hi, thanks for the reply. that's very interesting. have you used them before? do they really eliminate condensation? has anyone got experience with this product?