Vertical insulation in the loft

[GMM]

My loft is above a 2 storey section of the house, which joins a 3 storey section at right angles. Where these sections meet (an internal gable wall possibly, but I'm sure someone will correct that term), is an internal wall (half-brick) abutting teh loft space. Consequently, it gets pretty cold in winter.

Since I have to spend a certain amount of my time in that loft this summer for other reasons, I thought it might be a good idea to insulate the wall. It's not really a place for Celotex etc as, apart from anything else, I would never get any significant portion of a sheet into the space. I shall be cutting a bit more access but it would still be simpler to use something in a small/flaxible format.

So what would be the best thing to use? Somehow, regular loft insulation doesn't 'feel' like the thing for the job on a vertical wall. I was thinking of something like cavity wall batts but I'm open to any sensible suggestions. It's probably about 20sq m so not a particularly price-sensitive situation (unless gold-palted caviar is the thing for the job...)

[Davey]

The mind boggles:

1. Equivalent to a shed, but indoors.
2. Photographic darkroom, old-style.
3. Playing kinky games, your 'dungeon'.
4. Racing-Pigeon fancier.
5. In-laws coming to stay for a long time, your escape den.
6. You actually work for the FSB.
7. Ham radio operator.

[GMM]

All of the above actually ....but while I'm there, I'll be installing a floor and insultaing between that and the ceiling, as well as repairing a roof purlin.

[Davey]

You are a busy handyman!

[harry]

The problem with mineral wool used vertically is that it sags. Any little gap negates the whole insulation project.

I had a similar situation, I cut celotex into strips to get it in the hole. It was "reassembled"/glued into place with canned fixing foam.

[meow2222]

You won't see much return on your spend, so celotex is hard to justify. Pol ystyrene's too flammable/toxic for safety. Fibreglass would work find if yo u could keep it against the wall, and not have sagging gaps open up. Maybe glue would help. Wet cellulose would work well, but you presumably don't ha hve the equipment - I dont know if it can be trowelled on. Papercrete would work well if you've got a paddle mixer, but of course most dont have one.

Cardboard works but is rather flammable. Borax might sort that out. But you 'd still need to apply a whole bunch of layers.

If you dont have the right equipment for cellulose or papercrete I'd probab ly glue fibreglass to the wall.

NT

[stuart noble]

Fibreglass batts

[Martin Bonner]

Yes (but you can staple on netting/roofing membrance/wrapping paper to solve that).

Why do you say that? (It is pretty true for a gap that lets through a draught, but brick walls are pretty draught proof).

If 10% of the wall ends up not insulated, and the OP improves the heat loss by x5 on the remaining 90%, then the overall heat loss will be 10% + 90%/5 == 28% of the original. Thus failing to insulate the entire wall is responsible for about 1/3 of the remaining heat lost.

On the other hand, if 1% is missed, the resulting heat-loss is 1% of the original - and the gaps are responsible for 5% of the heat loss.

Note: 1% == 2cm on a 2m high wall.

[GMM]

t by this site

I think if I did that, it would be simpler to forget the celotex and just use the canned foam as access would never let me get any decent sized bits in.

[GMM]

Indeed. Although (to some extent) the same must apply to draught proofing: Unless there is a significant pressure differential (which seems unlikely in most situations), blocking half of a gap allows only half as much of a draught to pass.

[GMM]

olystyrene's too flammable/toxic for safety. Fibreglass would work find if you could keep it against the wall, and not have sagging gaps open up. Mayb e glue would help. Wet cellulose would work well, but you presumably don't hahve the equipment - I dont know if it can be trowelled on. Papercrete wou ld work well if you've got a paddle mixer, but of course most dont have one .

ou'd still need to apply a whole bunch of layers.

ably glue fibreglass to the wall.

You have clearly got the essence of the problem. I was thinking (vaguely) that fibreglass batts held in place with thin battens screwed through them into the wall might be a solution. Or maybe using plastic insulation retainers in place of screws (though that sounds a little like overkill). Somehow, I have trouble picturing glue holding up fibreglass very effectively.

I'm not sure the return will be ~that~ small though: This wall runs alongside the top floor landing and is positively cold to the touch in winter and chills the stairs and landing. I reckon it's worth putting a bit of effort into it, just like the ceiling below the same loft.

[harry]

If air can get through gaps in the insulation, the insulation may as well not be there. It can usually circulate behind the insulation.

[harry]

not by this site

Well I cut my cellotex into three pieces longitudinally (ie two cuts). I reassembled it in the same order so the joints were very thin.

[harry]

Polystyrene's too flammable/toxic for safety. Fibreglass would work find i f you could keep it against the wall, and not have sagging gaps open up. Ma ybe glue would help. Wet cellulose would work well, but you presumably don' t hahve the equipment - I dont know if it can be trowelled on. Papercrete w ould work well if you've got a paddle mixer, but of course most dont have o ne.

you'd still need to apply a whole bunch of layers.

obably glue fibreglass to the wall.

Cavity wall bats are intended for cavity walls where they will be continuously supported. Another alternative is to use two component spray on foam. You can probably hire the equipment at a tool hire shop.

Messing around with bats is just bodging and will be ineffective.

[Jim K]

y. Polystyrene's too flammable/toxic for safety. Fibreglass would work find if you could keep it against the wall, and not have sagging gaps open up. Maybe glue would help. Wet cellulose would work well, but you presumably do n't hahve the equipment - I dont know if it can be trowelled on. Papercrete would work well if you've got a paddle mixer, but of course most dont have one.

ut you'd still need to apply a whole bunch of layers.

probably glue fibreglass to the wall.

up against one leaf whilst also leaving an air gap between the batt and the other leaf..... sounds a similar scenario to me...

tsk tsk hazza that really is a bodge, esp on underneath of roofs

Jim K

[stuart noble]

A kingsize bodge and something of a health risk for the operative!

Batts need battens but Celotex could be screwed to the wall (at a push)

[meow2222]

Polystyrene's too flammable/toxic for safety. Fibreglass would work find i f you could keep it against the wall, and not have sagging gaps open up. Ma ybe glue would help. Wet cellulose would work well, but you presumably don' t hahve the equipment - I dont know if it can be trowelled on. Papercrete w ould work well if you've got a paddle mixer, but of course most dont have o ne.

you'd still need to apply a whole bunch of layers.

obably glue fibreglass to the wall.

Maybe its worth using celotex 2nds then

NT

[harry]

ify. Polystyrene's too flammable/toxic for safety. Fibreglass would work fi nd if you could keep it against the wall, and not have sagging gaps open up . Maybe glue would help. Wet cellulose would work well, but you presumably don't hahve the equipment - I dont know if it can be trowelled on. Papercre te would work well if you've got a paddle mixer, but of course most dont ha ve one.

But you'd still need to apply a whole bunch of layers.

d probably glue fibreglass to the wall.

He's on about a wall. The stuff is fine as long as kept out of sunlight. And fine too as a temporary repair on "nailsick" roofs.

[harry]

y. Polystyrene's too flammable/toxic for safety. Fibreglass would work find if you could keep it against the wall, and not have sagging gaps open up. Maybe glue would help. Wet cellulose would work well, but you presumably do n't hahve the equipment - I dont know if it can be trowelled on. Papercrete would work well if you've got a paddle mixer, but of course most dont have one.

ut you'd still need to apply a whole bunch of layers.

probably glue fibreglass to the wall.

I would say the best thing to use in those circumstances.

[Jim K]

Temporary as in sticks like shit to a blanket...

You used it then have you?

Jim K