Attic Insulation and Flooring?

cormie

Hey folks,
Looking for advice for a friend with regards insulating their attic. There's a bit up there already but it could do with another bit and they also want to put floorboards up there.

I've been up in the attic and the air is very bad, after a few minutes you can feel it and even biting down on your teeth it feels like it's slightly gritty, is this the glass fibre insulation that's up there? I've worked with it before and you come out itching all over. Is rockwool the same? Is there anything better to use nowadays?

Also, is it advisiable to insulate the ceiling rafters and tile over these too with the floorboards?

The attic isn't really big enough to convert to a room, which they were thinking to do, but at least if it was all insulated and sealed up it would make the place much warmer and then much easier to breath when you're up there too.

Any advice would be great including the best place to buy insulation and the boards!

Sleepy

Planning to do the attic myself soon too so definitely interested if anyone has any good tips on where's the best bang for buck on the insulation!

Sleeper12

We used to use Kraft insulation. Brown in colour & comes in a roll. We used to love using it as it wasn't itchy but had great insulation properties.
If the old insulation is old & worn from tradesmen over the years then its best to replace it. If it were me I'd raise the joists by screwing 2x2 or 2x1 on each one. This means the new flooring will be way above any cables or pipes.
If you have an electric shower & the cable is in the attic make sure you don't cover it with insulation.

cormie

Thanks for the advice. Never thought of raising the floor. Are you suggesting it just to avoid cables, or to be able to pack a bit more insulation in too?

Why would you suggest removing old insulation and not just packing more in? I don't think the stuff up there is in such a bad state, just it gets hard to breath up there after a few minutes and you can feel you're breathing in fibres so hopefully that will all settle down once the floorboards go down?

Also thinking to put in a new stairs and opening, but I think that might be a big job itself and you'd need to cut back joists and all that.

So I think:

• Install new stair and opening
• lay some 2*1 along joists to raise floor above cables, but I think it might be much easier (and better??) just to cut out small valleys for the cables to sit into the existing joints
• pack new insulation to floors
• cover floor with floorboards
• cover joists on slopes and then pack insulation instead of putting insulation up first and having to keep it held up while you secure board to slope.

Does this sound ok?

Just have to find out where to get good insulation and boards at a decent price now!!

Saw the openings for the attic with a ladder for €99 in Irish Building Supplies in Dun Laoghaire.

Sleeper12

Thanks for the advice. Never thought of raising the floor. Are you suggesting it just to avoid cables, or to be able to pack a bit more insulation in too?

You can get legs to raise the floor 6" and put in foam insulation

Why would you suggest removing old insulation and not just packing more in? I don't think the stuff up there is in such a bad state, just it gets hard to breath up there after a few minutes and you can feel you're breathing in fibres so hopefully that will all settle down once the floorboards go down?
If insulation is lets say 100% effective when first installed, this 100% reduces each time a tradesman crawls over it, something resting on it or just by being pulled back & put back down to make room for cables. It also flattens over time. For me if insulation is very old I'd dump it out & replace with new. It's very cheap anyway.
You don't insulate under the water tank & never go all the way into to the eaves. The attic needs to be able to breath a little

seamus

cormie wrote: »

might be much easier (and better??) just to cut out small valleys for the cables to sit into the existing joints

It's easier, but do not do it.

Joists cannot be cut cross-ways to make room for cable. It weakens the joist and potentially compromises the whole roof.

OK, so they can - there is a certain amount you can cut in depending on where in the joist you do it, but it's safer overall to just not do it.

If you really want to route the cable, then cut the cable in half, bore a hole in the centre of the joist and run the cable through.

Or what I did when laying chipboard flooring in the attic was to cut into the flooring and run the cables up through the flooring, over the joist and back down again. Then just covered the exposed cabling with duct tape to avoid catching on it.

Only using it for storage, so I'm not concerned about the look of the cables or long-term questions of standing on then.

Calahonda52

OP, there is so much wrong with what you are proposing and what sleeper in part has suggested I really don't know where to start, other than log out of boards and go shopping.

I will come back later from the desktop where I have links to some reference material but in the meantime, can you please post the precise makeup of the roof construction, including the eaves detail.

In addition describe the roof type and the sort of house you are living in.
At s# 18k posts you should be able post some pictures.
Thanks

Sleeper12

seamus wrote:

If you really want to route the cable, then cut the cable in half, bore a hole in the centre of the joist and run the cable through.

Cut the cable in half???

seamus

Sleeper12 wrote: »

Cut the cable in half???

Yeah, split it and rejoin it. No biggie.

Sleeper12

seamus wrote:

Yeah, split it and rejoin it. No biggie.

Rejoin it with what?

seamus

There are a number of ways of doing it and it depends on what kind of cable you're splitting (e.g. power -v- network -v- alarm) and the gauge of the cable.

If you're not comfortable doing it, I would suggest not doing it.

Sleeper12

seamus wrote:

If you're not comfortable doing it, I would suggest not doing it.

It's not best practice. Cables should not be cut & rejoined generally. And if it was a 6mm or 10mm cable it could be downright dangerous.

Water John

Be careful with old glass fibre insulation. Use a breathing mask.

Sleeper12

Ripped from SEI website
I want to floor my attic. How can I insulate the attic properly and install a floor?
In many cases, roof spaces will have joists that are 4-6" high. This is not sufficient space in which to install insulation material that will bring the level of insulation up to Building Regulations standards, ie. 0.16 W/m2K. In order to have a sufficient level of insulation in your attic underneath a floor, you have two main options:

1) Raise the height of the floor by install battens, 4-6" high, at right angles to the existing joists in order to allow a sufficiently thick layer of wool insulation to be installed under the flooring and maintain a uniform level of insulation across the attic.
2) Install a layer of rigid insulation of sufficient thickness and apply the flooring to this. A 4" thick layer of typical rigi insulation materials is roughly equivalent to 8-9" of wool insulation. Some suppliers supply rigid insulation with a layer of chipboard bonded to it which acts as the flooring when installed.

It is important to ensure that ventilation openings, e.g. soffit vents, remain unblocked.

Calahonda52

See pages 66 onwards here
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx

The physics of insulation is that, for the vast majority of insulation materials, the air is the insulant and the material such as wool, glass fibre et etc is just a medium to retain the air.
So
packing insulation just compresses it and drives out the air so is a waste of time and effort and money.

The next issue is stopping the air moving through the insulation which is not addressed in that piece of pretty useless advice, ripped from the SEAI website.

Putting the new battens at right angles is counterproductive in my opinion for two reasons.
1: laying the new insulation across the existing rafters will invariably create humps and hollows that the air from the eaves will pass under, making the new layer meaningless.
2: its impossible to do against the eaves, and especially in a hipped roof: the SEAI picture shows a nice gable..:(

It is essential to bring the insulation out to the outer edge of the wall plate, other wise you get what is shown in the attached pictures.

The proper way to do this is to strip off the bottom few layers of tiles, fit the eave carriers as shown in page 66 in the first link and then fill up with loose insulation such as cellulose.

My final grip here with the SEA idea is that unless the ceiling below is 100% airtight, the rigid insulation or / and the chipboard will act as a barrier, with the jew point in the insulation below, leading to condensation. http://www.dpcalc.org/

Cutting notches in ceiling rafters is not a good idea. Cut them in the new rafters which are not structural
Power circuit, immersion cylinder cables and cooker cables need to be properly sleeved as they are designed for heat loss to air.
Alarm, CCTV, etc cables no issue. the same usually applies to lighting circuits.

Finally the suggestion of cutting and rejoining elec cables is dangerous and AFAIK, against the regs as the connections need to be identifiable and exposed for examination.

Keep well and good luck.

Sleeper12

Calahonda52 wrote:

Finally the suggestion of cutting and rejoining elec cables is dangerous and AFAIK, against the regs as the connections need to be identifiable and exposed for examination.

Totally agree here.
I've seen an attic burn so bad that the owners had to move out of the house for close to 8 weeks because some genius used a connection block and insulation tape to extend the cable going to the immersion. I can't say one way or another about the regs but I have seen first hand how dangerous it is.