insulate inside loft...

[unclebob1]

Afternoon all,

My tiled roof consists of the following laters (looking from the bedroom ceiling up:

lath+plaster, old squashed mineral wool/glass, wooden floor... and then the attic space followed by joists + tiles (with plenty of bits of daylight in between the tiles!)


I want to insulate this a bit better: along the lines of:
waterproof sheet run around and between each joist, then put a layer of 50mm or 60mm kingspan or similar.

Floor side, take off the wooden floor, and take out the mineral wool, same 50mm or 60mm of kingspan or similar, then put the wooden floor back.

Will rewire the light wires so they run in the cavity between the insulation and the wooden floor back, drill a gap of say 2.5cm though to then push the wires back through for light fittings/switches.

Foil back or straight foam better?

Sound ok? (more concerned re the plastic and insulation on the joist side with damp)
Looking to get insulation from a seconds company - mismarked/slightly off size.

 

[flameport]

Plastic not needed. Lighting cables don't need to be moved. Don't need to remove the old mineral wool. Kingspan is too expensive, 50mm is too thin and will take too long to install.

Alternative option:
Remove wooden floor.
Call British Gas who will insulate your loft for free.

If you really want the floor, before insulation is fitted put in suitable extra timber to raise floor level 12 inches above where it is now.
Or get rid of the junk and don't bother with the floor at all.

 

[unclebob1]

wife wants storage, and with the tiles showing daylight, im sure if wind is blowing the wrong way when raining, i will be getting water in.. there is no felt layer.

Will be using seconds of the kingspan (or celotex etc - secondsandco) labour will be my own so not to fussed re time, but open to other ideas?

 

[noseall]

Surely that loft is not suitable for storage?

 

[unclebob1]

noseall, im trying to make it suitable!

 

[noseall]

noseall, im trying to make it suitable!

Appreciate this. But everything will get covered in crap.

It's no fun cutting foam board insulation. What size is the hatch?

 

[unclebob1]

think the hatch is 70cm by 1m but will measure tonight... ideally would like to re-roof but concentrating funds on ground floor extension at present...
Loft is currently empty (save cold water and ch tanks) - so i'd rather do it now then once stuff starts getting put in! ( only just moved in and everything is currently in bags on the ground floor!

 

[unclebob1]

Sorry - hatch size is 55cm by 80cm.
been offered 4 sheets of celotex 100mm, 3 sheets of 90mm and 3 sheets of 80mm for £150 ( 1.2x2.4m sheets) so tempted to get... and atleast insulate floor level, and then plastic sheet the tile level

 

[unclebob1]

Sorry to bring this one back up, ended up re tiling the roof - a fair number of tiles were crumbling, few missing etc so had it replaced. So membrane is now directly under the tiles, such that i do not need to worry about that layer. Now its just the insulation. I understand you feel its not worth doing, however i think it will still be the best way for me to make use of the space. Putting in 12" risers will more or less lose a fair amount of storage space, so at present not really a go.

Currently the cold water tank, and central heating tank are both in that space, along with associated pipes, so i do not want to remove all heat from that loft space, rather insulate between the rafters and stop the heat loss to the outside.

The rafters are approx 100mm, so whats the thickest ridged board insulation i should put in between? Assuming i need to leave an air gap on the tile/felt side?

Will look to do floor joists at another time once rewiring is decided and accommodated for.

 

[Nige F]

Have a look at Loft Legs on the net- you can make a good storage platform over fibreglass insulation - my loft was insulated FOC for the previous old owner . Easy to construct a walkway between the higher loft legged chipboard area and leaving the tiles uninsulated seems to work for me - a cold loft rather than a warm one

 

[unclebob1]

Hi Hige,

Thanks for the reply, im hoping to insulate at the rafter level at the moment - there is already some fiberglass insulation at the joist level on the floor, its all boarded up at present... So i want to insulate the top, then rip out the boards, rewire, insulate then close it... but prob use celotex/kingspan seconds on the floor level so i can keep the height - if i put in raisers, i'll loose a lot of height to the point where i'd have to tilt my head in most of the space to move about.