# About to insulate attic - anything I'm missing?



## MAJJ (4 Jan 2006)

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


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## Sue Ellen (4 Jan 2006)

2 very basic questions:

Have you already put lighting up there?

I often wondered would aeroboard make a good lid for the tanks?


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## ClubMan (4 Jan 2006)

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?


 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


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.


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## MAJJ (4 Jan 2006)

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


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## Sue Ellen (4 Jan 2006)

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.


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## nai (4 Jan 2006)

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.


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## MAJJ (4 Jan 2006)

Excellent so that's my lids sorted! I won't say I've thought of everything yet. Who would've thought aeroboard floats  - I certainly didn't


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## ClubMan (4 Jan 2006)

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.


It won't break up unless somebody meddles with it. Even then it's pretty sturdy.


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## Lemurz (4 Jan 2006)

If your over 65 Energy Action might be of interest:

http://www.energyaction.ie/


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## macnas (4 Jan 2006)

Why not leave the old insulation where it is and lay the new over it?


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## Carpenter (4 Jan 2006)

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.


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## NiallA (4 Jan 2006)

macnas said:
			
		

> Why not leave the old insulation where it is and lay the new over it?


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.


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## z102 (4 Jan 2006)

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.


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## Sue Ellen (4 Jan 2006)

"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?


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## MAJJ (5 Jan 2006)

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


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## MAJJ (5 Jan 2006)

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.


.

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


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## Sue Ellen (5 Jan 2006)

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.


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## z102 (5 Jan 2006)

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.


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## Touch Wood (6 Jan 2006)

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.


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## z102 (6 Jan 2006)

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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## ClubMan (6 Jan 2006)

Isn't also recommended to leave it longer than necessary at the edges/eaves and fold it back onto itself?


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## z102 (6 Jan 2006)

I haven't heard about folding it back but it should cover the ring beam for sure. I'm not sure about the product that MAJJ is going to use, as far as I remember my last visit to B&Q the Knauf product MAJJ is talking about comes in triangular mats. It is usually used between the roof beams where it would be stucked against each other like wedges and so holds itself in position without the need for further fixings like staples for example.These wedges are slightly more expensive than the rolls but are cheaper than the rolls "wrapped and packed" in plastic foil. For laying insulation the fixing of it is no issue, so the cheaper product would be o.k. in insulation terms. This could be indeed folded back. But the wedges are triangular and so a folding would always leave an uncovered piece , well, an only once-covered piece so to say since the folding of a triangle will never match the surface unless we're assuming a 90 degrees angle. Which the glass wool triangles aren't. And they are quiet thick and heavy,  some are treated  with a resorcin based resin to give them a more sprungy/stiff texture.These would be awkward to fold and to be hold in place.


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## ClubMan (6 Jan 2006)

ClubMan said:
			
		

> Isn't also recommended to leave it longer than necessary at the edges/eaves and fold it back onto itself?


I should also have said that you must take care not to obstruct any eave vents with the insulation material as the attic needs ventilation. Those are two tips that I remember hearing somewhere (most likely from the da) but I am open to correction on them...


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## MAJJ (6 Jan 2006)

Hi All,

Do you folks sleep? But really, thanks again. Sorry I would have checked in on the discussion last night but I have no connectivity yet. 

The comments on thermal bridging, eaves/ventilation are detailed in this document [broken link removed]

The product I have purchased is [broken link removed]  

These are rolls that are perforated to cut either in 1/2 or 1/3.

I am thinking of buying more this time 100mm splitting it in two to reach my desired width and using this for in between the joists and going over this at right angles with the 170mm giving me a total of 270mm - would that be sufficient. I will try and get an answer externally and post it back up as this is key to whole approach.

BTW - I have that answer I think this one post will be like a FAQ on the topic.

Thanks,
MAJJ


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## slave1 (6 Jan 2006)

Hi,

Tackled this job myself a few years back and can offer..

Lid - I used 4" polywhatsis, just put it on top on tank, it sticks a foot out all around, end of story

Light, put in TWO lights as the attic is high on the shadow factor and you do not want to lose your footing, so a  bulb at either end of the attic to avoid the shadows as much as possible

Laying the insulation - didn't bother taking up old stuff, put on ole clothes and simply threw them out when finished because the glass fibre gets everywhere

Tip, cut a large square bit of timer to avoid balancing on the joists, easy to pick up and move around with you, also dont insulate near the eaves, and to finish rolling the insulation I used a kitchen brush to reach into the ever narrowing space as the roof meets the eave.
Cut the insulation in the attic itself.

Top quality eye/mouth face protection required.


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## ribena (6 Jan 2006)

Sorry to cut in but do you need to have a lid on top of your water tank in the attic??  I know I don't have one on mine.


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## ClubMan (6 Jan 2006)

I don't think it's absolutely necessary but it just keeps dust and other minor debris out of the tank - especially if you are moving stuff around in the attic regularly.


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## ribena (6 Jan 2006)

Thanks ClubMan.  I thought it might have been necessary.


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## MAJJ (6 Jan 2006)

No problem Ribena - I had the misfortune of living in a house where a rat was in the attic and we had no lid on the tank.  Both problems were resolved by the owner. But my concern was, apart from the rat itself, was a danger of contracting weils disease or something else from the water tank becoming contaminated. Not sure if that concern was/is valid.

Another point someone from AAM made was - by insulating around the tank and placing a lid, the water temperature will be higher and hence doesn't require as much energy to warm it.

Cheers,
MAJJ


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## ribena (6 Jan 2006)

Thanks MAJJ.  The very mention of that furry animal makes me squirm.  I think I will put a lid on my tank after all!  Thanks for the advice on the insulation also.


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## Carpenter (6 Jan 2006)

ribena said:
			
		

> Sorry to cut in but do you need to have a lid on top of your water tank in the attic?? I know I don't have one on mine.


 
It's an absolute necessity to have a loose (not airtight) cover or lid on your cold water storage tank (cistern). New regulations and byelaws require it by law- older properties often had tanks fitted without lids but all new tanks now come complete with covers. If you ever have to drain down an older tank and plumbing installation you'll see why: flies and other insects invariably migrate into the attic, via ventilation points and will end up in an uncovered tank. During the warmer months the water can get quite warm in the tank- so these two factors combined can obviously be unpleasant if not dangerous to human health- which is why you should never drink water from the bathroom sink! This problem is exacerbated in houses with very large storage tanks or where the house is occupied intermittently as the water can remain stagnant in the tank when water is not being drawn off regularly. Which is why holiday home owners and the like should drain of their tank when the property is unoccupied.


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