Advice on attic insulation options

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mir2001

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Hi
In anticipation of soaring energy bills, I have cleared out the attic and now need to figure out the best insulation plan.
I have tried to read up on this topic but still find I am not sure what way to go.
I'm hoping others here might have suggestions based on knowledge and experience.

The attic currently has really old fibreglass insulation - may be 100mm - looks like batts - between the joists. I think the joists are approx 15cm deep.
There is flooring over about 50% of the attic and an open water tank.
There is no insulation between the rafters which are about 10cm deep
I will need to continue storing items such as suitcases, spare bedding, DIY tools up there once the work is completed.
The attic has a velux window that lets in a stream of air around the edges and a drop down wooden ladder for access.

Possible solutions
1. It has been suggested by a handyman guy I know that we could leave the old insulation and install rock wool between the rafters but it seems to me the rafters are not deep enough to hold the 270mm (?) needed for good insulation. And then there is the issue with the Velux - not sure if that needs to replaced or if it can be repaired?

2. I looked at foam insulation between the rafters, and then getting that covered with plasterboard and adding full flooring so we could maybe stick a desk up there as I am working from home and short on space. The foam seems really efficient from a space and insulation perspective but there seems to be some mutterings online that it could give off gases, be difficult to remove, hide roof issues, and make selling the house difficult. No idea if any of that is valid criticism.

3. Put rock wool between the joists and put flooring above, but I wonder if this will really work if I don't remove the old insulation? Also wondering if a handyman could manage this or do I need a company to make removal safe?

4. Outlier option - go for a basic attic conversion as this will presumably handle the insulation too and give me a small space to work from home. But the attic space won't be big, it's a small attic. I looked at one in the estate that was up for sale once and outside the central strip, you tended to hit your head off the sloping ceiling.

Would be really grateful for any thoughts on this, or suggestions for other insulation options I may have overlooked, thanks in advance
 
Pinoy adventure said:
#3 you could give it a go yourself.get yourself a few rolls of insulation and a hand saw and away you go.
Give an extra 5/10mm so it fits snugly between joists/rafters.
Click to expand...
Thanks for the reply, do you mean place the rock wool over the existing fibreglass or remove it first?
 
There is no need and no advantage to removing the old stuff......unless it is causing some sort of other issue.
Just put the new stuff down over the old stuff.
If you can, you should seal any gaps in the ceiling too with expanding foam or caulk, e.g. around down light, pipes, wires, random holes.
General recommendation is that you should aim for 300mm of wool type insulation (i.e. rockwool, earthwool, fibreglass, wool etc.). I went for 400mm and could immediately feel the difference in the house.

With your joist being 15cm (150mm) you should fill between them and then add another 150mm on top of them.

Our joists were also 150mm so we Built a raised wooden platform to allow for storage but also allow us to insulate underneath it to the right level. Don't insulate underneath the water tank. But do insulate the water tank itself.

There is no point insulating between the rafters unless you intend to actually convert the attic.
 
Ajam is right leave the old stuff there and fit the new insulation running across the joists in the opposite direction to the existing insulation.
 
@mir2001 - when laying the attic insulation, make sure you have a proper mask for mouth & nose - there will be years of dust up there and also breathing in the fibreglass insulation isn't great, so don't scrimp out on that side of things.

When laying the roll out insulation, in between the joists, bring the level up to the top of the joists and then another layer perpendicular to the joists so as to cover the gaps as much as possible.

If you are taking up the floor in the attic, then have a think about putting down rigid insulation between the joists in that area, I feel it would offer better insulation and you would only need to go up to the joist level and relay your floor on top again. It will be more expensive for such, but I think would be a better solution.. Jjust make sure that the level of rigid insulation is equal to (or just below) the top of the floor joists, otherwise your attic floor will be on the insulation board, and any weight will be taken by the boards and not joists and thus could affect the plasterboard underneath.

While you are up there, have a look around on the roof area to make sure there are no damp marks / light coming in etc and careful of the water pipes (which should be also insulated) & electrical / house alarm wire which should be layed on top of the insulation.
 
If the old fibreglass has been there a long time it will have compresses and lost quite a bit of its effectiveness. The full joist thickness of new insulation will perform a little better though with the added headache of removing the old insulation (you could lay that out over the new stuff after.

Whichever option you choose, for the section you plan on flooring, make sure the insulation comes just to the top of the joist and you are not compressing it down to lay the flooring as that will affect performance.
 
The centre of our attic was floored for storage.
What I did was.
Remove everything "stored" to shed.
Remove flooring to shed.
Removed old insulation.
Raised the batten in the centre from 100 mms to 200mm.
Put new 200mms insulation down.
Replaced flooring.
Brought most stuff back up.
Everywhere else removed old 100mms insulation.
Put down new 200mms in its place.
Crossed new insulation with old insulation.

The old insulation was there 24 years and it illustrated what sometimes happens when things are not in view.
 
Lots of really great advice there, thanks a million to everyone who responded, it's really helped and I'm feeling a lot more confident about tackling this now which is honestly a great relief.

So I will definitely be opting for option 3 now and putting rockwool between/over the joists. I am still not certain about pulling up the old insulation, it's probably been there around 20 years at least, my gut instinct is that it may be better long term to try to pull it up now even if it's messy. I'm probably going to look at putting down raised flooring over the rock wool to allow for 300mm depth.

One last question: do I need to leave gaps near the eaves? It doesn't look like there are gaps in the current setup but I haven't looked close up yet so may be wrong.

@Jazz01 you mentioned rigid insulation - is this Kingspan? just wondering if 150mm of rigid be as good as 300mm of rockwool? Thanks again
 
Yes you should leave a small gap at the eaves so as to allow for air movement.
And yes 150mm rigid kingspan is roughly equivalent to 300mm of rockwool.
However, rockwool is a better sound insulator, so if you live on a noisy road it does dampen that out a little better than rigid insulation.
 
@mir2001 - great to hear that you will tackle it yourself, not too complicated & just give yourself time - doesn't all need to be done in the one day. Get some knee pads and a strong plank of wood to support your weight across the joists, will make moving around up there a bit easier... and defo invest in the breathing mask.
Best of luck with it...
 
@mir2001
Yes, you'll have no big problems laying the insulation, be careful around downlights. Just wondering what you're going to floor the attic with, especially the raised aspect of it after the insulation is down? That's far from a simple job if you want it done properly. Be careful what you start.
 
Thanks again to everyone, this has all been really, really informative and all the encouragement is very much appreciated.

@Leo The fibreglass is even in some parts but very bunched up elsewhere. I suspect it's even more uneven under the flooring.
We have no downlights so just have to ensure the wires for the alarm etc are laid on top.

Removing the old insulation is probably the thing I find most daunting given the toxic nature of fibreglass.
Just curious if others think it can just be bagged into a set of black plastic bags? Would double bagging be best?

@noproblem I haven't quite figured out the flooring - a guy at work mentioned you could buy floor lifters from Woodies so I was presuming you could buy the flooring there or somewhere similar too. Might just floor enough to store some items and then ask a guy I know who does some DIY in his spare time to complete the awkward parts as he has a decent set of tools.
 
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