About to insulate attic - anything I'm missing?

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MAJJ

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Hi Folks,

Just bought and moved into a 35 year old home - 3bd semid. I am about to tackle the insulation between the joists in the attic. We have had an attic stairs fitted and we would like to use some of the attic for storage.

This is what we have planned and I would appreciate if anyone can highlight any issues. BTW - I have read the many posts on AAM on this topic.

The joist depth is 100mm and the current fibre glass stuff is degraded, ragged and very thin 40mm if present at all. I understand that a depth of 150 - 200mm is recommended. I have opted for Knauff combi cut 170mm - partially because of price (real cheap in B&Q) and it seemed like a reasonable match to my needs. I basically plan on removing the old stuff, moving any wires and placing these on top of the new stuff which I will cut to fit between the joists. I intend on leaving a 50mm gap around the eaves, insulating pipes but not directly under watertanks. I also have a gas flue and chimney running through the center of the roof.

I plan on partially flooring some of the limited space up there but this will compress the insulation material slightly and hence will lower it's u value - any suggestions there?

I plan on dressing for the occasion - gloves, face mask, goggles etc. Any tools required apart from saw/scissors for cutting insulation?

Also, I have two water tanks up there one large round one and another smaller square one. I plan on putting lids on these - any suggestions on what to use?

How/where to dispose of the old insulation material?

Is there anything else people could suggest.

Many thanks,
MAJJ
 
2 very basic questions:

Have you already put lighting up there?

I often wondered would aeroboard make a good lid for the tanks?
 
MAJJ said:
Also, I have two water tanks up there one large round one and another smaller square one. I plan on putting lids on these - any suggestions on what to use?
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Marine plywood perhaps? I just have a sheet of polystyrene over ours as a makeshift lid. Don't forget NOT to insulate below the tanks as the heat from the house should be allowed up to ensure that they don't freeze.

plan on partially flooring some of the limited space up there
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Be careful what you use the additional space for as without restructuring the attic beams will most likely not be capable of taking the same load as a normal upstairs room floor.
 
Hi Suellen/Clubman,

Thanks for your questions/suggestions.

Light - yes thankfully there is a light fitted.
Load - thanks - I will bear that in mind.

Lid - I thought of polystrene but being a bit new to this thought it could break up and get into the water system. I know this water is for washing but I thought it may block up something. Maybe there is a filter for that sort of stuff?

Undertank - won't be insulating under there!

Cheers,
MAJJ
 
I don't think aeroboard will break up too easily. We have used it a few times recently and I think you can buy quite thick stuff in Woodies etc. AFAIK you would need to hack at it a lot for it to break up.
 
also aeroboard will float - so it should never get into a position where it can block something in the tank given that the drainage points etc are located near the bottom.
 
Excellent so that's my lids sorted! I won't say I've thought of everything yet. Who would've thought aeroboard floats:eek: - I certainly didn't:)
 
MAJJ said:
Lid - I thought of polystrene but being a bit new to this thought it could break up and get into the water system.
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It won't break up unless somebody meddles with it. Even then it's pretty sturdy.
 
If you want to avoid compressing the new insulation why not fit timber battens to the top of the existing ceiling joists- to create a greater void under the new flooring. Screw fix the battens as opposed to nailing to avoid damaging the ceiling below. If using polystyrene as a lid for your tanks it would probably be a good idea to weigh it down with a piece of timber or tie it in place with some string to prevent the cover being dislodged (mice/ birds etc- it has been known to happen). Be sure to cut hole in the lid" to allow the expansion pipe to terminate within the tank.
 
macnas said:
Why not leave the old insulation where it is and lay the new over it?
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i agree with macnas, why remove the old insulation. Just place the new stuff over it. Less work, no expense of dumping the old stuff, extra benefit from the additional thickness of insulation, leaving it there seems a winner all round.
 
Carpenter's advice on increasing the height of the existing ceiling joists is right. Compressed glasswool would not only loose some of it's insulation value but it might also put to much pressure onto the 35 years old plaster board underneath causing it to crack or even come down.
When strenghtening the existing joists - and when you have the patience for it- it might be worth to lay new joists paralel to the old ones but of a stronger quality.This would a.) give a safer,more loadbearing floor and b.) a higher packing space for the glass wool. Fix the new joists with strong srews or bolts to the old ones to stiffen them , protecting them in this way to fall on their sides when shifting a load on the new floor.
 
"Carpenter's advice on increasing the height of the existing ceiling joists is right"

Whilst this does appear to be a very good idea does it not also add to the existing problem of lack of head height in attics though? How much height space would be lost?
 
Wow - so many suggestions. Thank you all for your valuable suggestions. Heinbold - thanks for the tips will bear in mind but will be more long term and if current plans for storage change will definetely take your advice on board.

Carpenter - as you suggest I will probably opt for fitting timber battons to the joists. Simple, elegant, solution often the best.

Sueellen - I'd be happy to have my house retain heat! But your right of course it will limit height. But they way it is layed out it's not that conducive to walking around anyway so we will only floor and use a small portion. And, yes we will distribute the load!


Any other thoughts on the benifit of leaving the existing old insulation. I thought I read somewhere of this potentially causing vapour to be trapped between the lairs.

Oh I've couple of decades away from 65:)

Thanks again,
MAJJ
 
Hi,

I've just been reading on

[broken link removed]

and it says that
If your attic insulation is currently less than 200 mm, then you should add further layers.
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.

Now I'm real concerned that my thoughts on this i.e taking up old (now sagging to no more than 20mm ) and replacing with 170mm. BTW - already bought the 170mm stuff!!!

I now believe that a minimum of 250mm is recommended - am I correct. I think that's 100mm between joists and 150mm accross the top in the opposite direction.

Can anyone please advise as I intended on completing this job at the w/e.

Thanks,
MAJJ
 
Hi MAJJ,

Rushing a bit at moment so sorry I can't have a root around the board to see if there is anything further to help. Perhaps you could have a quick read thru these and you may find something useful/helpful.
 
Adding more height to the floor would indeed reduce the overall height of the room. But with a storage space this is not that important. If the room is to be used as workplace or a living space then the building regulations should be adhered to(245 cm ?).
When using “open” glass wool it shouldn’t be a problem to add another layer straight on top of the old layer. But one shouldn’t leave glass wool open, so a simple breathable cover should be added on top. Glass wool can fly around and end up in the user/habitant. Either via the lungs or via the stomach. Since the water tanks suck up (polluted) air from the attic when they are in use the water coming from them is most likely polluted with glass fibres.
So cover the glass wool when finished with the job. Or use the already “packed” material, Knauf is selling that at B&Q as well.
 
If you put the second layer perpendicular to the first you get much better results as you cut out the Thermal Bridgeing of the wood.
 
Cutting tools for glass wool would be a toothed knife like a bread knife or a gardeners (foldable) branch/twig saw or a simple handheld saw. If buying a new tool the cheapest quality would be fine. When cutting lenghts of rolls of glass wool than cut the entire roll (unpacked) with a saw to the required width and use the leftover strip to fill up gaps. Cut the pieces a little bit larger than required, you can push the glass wool together ( compacting) but you can't expand it without loosing insulating quality if to short.
Don't use a power tool like a circular saw for the job , it would be to messy, inaccurate and causing a lot of dust. But there are also some sort of electric shears with a slow turning blade similar to a pizza knife that might be usefull , but I have no experience with those.
 
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