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Attic insulation: Should I remove wooden covers?

We have a fairly old house where the ceilings have wooden covers in the attic (see photo below).

One of my next projects will be to improve attic insulation for the ceilings of our rooms. After watching a fair amount of YouTube videos I am wondering if I should remove all these wooden covers in order to be able to lay proper insulation into the spaces between the beams.

Advice is very welcomed. Thank you.

The aircon installer removed the cover and left it flipped over (on right).

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Comments

EricL

Hello @TheHandySqirrel

In theory, those air gaps between the wooden covers and your ceiling are supposed to provide a certain amount of insulation. Unfortunately, I've no data to show how much insulation it provides. If you were to use large ceiling insulation bats that covered the entire surface of the ceiling instead of cutting them into sections the gap would serve as a thermal break. It would disrupt the transfer of heat directly to the ceiling gib.

Let me call on our experienced members @TedBear, @JoeAzza and @MikeTNZ for their recommendations.

If you need further assistance, please let us know.

Eric

TedBear

Hi @TheHandySqirrel , like @EricL , I have not come across this setup before, but I imagine that the wooden covers do supply some insulating properties already, just like the outer skin of a wall. It seems to make sense then that you could lay insulation over the top of the covers and would benefit from that extra layer of trapped air, instead of going to the trouble of removing them.

I assume that the covers are there to make it easier and safer to walk in the ceiling space??

MikeTNZ

Hi @TheHandySqirrel,

It's been some time since I've seen them sorts of insulation, they are rated at R 0.9

Personally, what I would do, is leave them where they are, they are not hurting anyone.

And please do not step on them at all, unless you want to end up in the room below, all of a sudden.

I think the best thing you could do, if you were going to upgrade your insulation, is to lay some sort of Batt type insulation over

the top of this arrangement.

It doesn't need to be Fibreglass, there are some really good wool-based and other "green" products that are even better than fibreglass, do your homework before buying enough insulation to fill out a whole roof space, it is just that fibreglass is the one that is specified when contractors do this work.

The only caveat I add to this, is if you have the older type down-lights in your ceiling that vent into the roof space, don't ever cover them up.

The temperature rise if these are covered up can cause a roof/house fire.

If you require further advice, by all means let me know in a post below.

Cheers,

Mike T.

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/24480#Comment_24480

Hi @MikeTNZ,

thank you for your advice. That makes sense to me. Here's my current plan for the attic project:

1. Survey attic to get measurements

2. Clean up dirt and other junk

3. Install permanent lighting

4. Install attic ladder

5. Replace downlights

6. Seal holes and cracks

7. Research and install insulation batts

Do you have advice on item 5, replacing downlights? I'm thinking of removing them altogether, but leaving a cable into the room below that ends in a box so I am able to install future lighting if required (which will then hang off a hook screwed into a joist).

I'm also not clear on the best type of insulation to use. There's rock wool, stone wool, mineral wool and then fibre glass. Do you have a sense of which one is suitable for the Sydney region? Thank you!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/74882#Comment_74882

Hi @TheHandySqirrel,

You could consider removing the coverings, cutting up and adding Bastion 1200 x 600 x 50mm XPS Multi-Use Insulation Foam Board and replacing the covers. Cost-wise it might be more budget-friendly to use Earthwool insulation, though the foam would be a neat solution.

Earthwool, rock wool, stone wool and mineral wool are all the same type of insulation. It involves heating natural rock to melting temperatures and then spinning the molten material into fibres. Fibreglass batts are made similarly but use glass as the base material. In my experience, I've found Earthwwol batts easier to work with and significantly less itchy, as I don't tend to get the same glass fibres embedded in my skin. You should still wear a long-sleeved shirt and trousers and appropriate PPE.

All of the above insulations are suitable for Sydney. It comes down to the R-value of those products and the amount of insulation you require. The higher the R-value, the better the insulation will be.

Hopefully, @MikeTNZ can offer their opinion on the light situation. I'd be inclined to think it would be best to leave the current lights in situ until you've purchased the new ones. That way, you can organise one visit from the electrician instead of multiple to disconnect and reconnect.

Please let me know if you have further questions.

Mitchell

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/101097#Comment_101097

Thank you @MitchellMc for your valuable points. I will give it some more thought.

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/74882#Comment_74882

Hi @TheHandySqirrel

As you live in the sydney region I installed Cellulose insulation ( treated paper) as a Viable option.

24 years later never looked back.

had an central roof air con leak the gyprock sagged and it all fell in simply swept up paper and into garbage bag and redistributed into roof once repaired and dried.

No mice (borax treated)

totally fire proof ie mine i burn with a blow torch in my hand and it glows but the second the flame removed it snuffs out completly with in 1second.

R rating 3 to 3.5 in a typical house cheaper recycled material. (Thickness dependant)

It compacts around rafters and all cavities fully (its blown in)

Safe around power and any electrical hot spots wont combust ( ie 50 w halegen globes get very hot)

It is raked and level in roof then sprayed with water which hardens the paper into a crust so no paper blown around.

Well cheaper than wool and not itchy like fiberglass,

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/101097#Comment_101097

Hi @MitchellMc,

I have two more questions as I'm preparing this project.

1) Some websites recommend two layers of half the final R-value laid perpendicular to each other. This sounds good, but would add about 50% to the cost of the insulation. Is this warranted, i.e. do I get a much better insulation result than with just one full R-value layer?

2) My joists are only 100mm high, but R4 insulation is about twice as much. What is the best technique to raise the joists in the area where I want to build a catwalk for attic access? I'm assuming I put pieces of 100x50 on top of the joists, but I'm unsure how to connect the two in a stable way.

Thank you so much!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/117761#Comment_117761

Hi @TheHandySqirrel,

Since you're installing insulation thicker than the joist's depth, where the insulation protrudes above the joist, it might not sandwich against the next batt. If the batts don't squeeze together at the top, you will lose within the vicinity of 1.0 R-value. A way to get around this would be to cut thin slices of insulation and sandwich them into the void. Please see the image I've created below.

Halving the thickness of the batt and laying the second layer perpendicular to the first would be an effective way not to have to deal with the gaps between the batts. However, I see no R-value benefit to laying half your insulation in the opposite direction.

For the catwalk, I'd suggest placing 90 x 45mm framing timber on top of the existing timber and connecting them with Pryda connectors. There's a connector or nailing plate to suit just about every connection you can think of. You can use a connector plate or nail plate to fix the two timber's side faces together. The 10mm of batt compression is negligible.

I just wanted to remind you to be very careful working in the ceiling space and only walk on solid timber members. If you can squeeze a couple of timber boards up into the roof to work off, that would be best. That way, you can at least scootch your platform along and kneel on it instead of trying to balance on the beams.

Please let me know if you have further questions.

Mitchell

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/117761#Comment_117761

Hi @TheHandySqirrel ,

I agree 100% with @MitchellMc s ideas, but would like to offer an modified view as an option to consider. Although putting insulation in the gaps over the timbers might give you a perfect result, there are some disadvantages...

1) the return on time and effort would likely be not worth it, given that the timbers provide good insulation, unlike the plaster ceiling between them,

2) It will make it very difficult for anyone, including you, who needs to work in the ceiling to know where they can safely step. I doubt that any contractor will be willing to venture into the space.

I prefer Mitchell's idea of keeping some wide boards in the ceiling to move to where you want to go, but if you need a fixed catwalk, then raising the necessary timbers in the manner he suggests makes sense.

But compressing the insulation temporarily with boards to get to some areas shouldn't be a problem. I've made temporary kneeling platforms before and the insulation has bounced back ok.

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/127170#Comment_127170

Hi @MitchellMc,

thank you so much for your detailed reply. I'm going to use some form of Earthwool batts – wouldn't they extend outwards towards the joists when put in place? Losing 1.0 R-value seems a lot.

Thank you too for giving me links to the correct materials. I was looking in a totally different corner at much more expensive options. I'm guessing you didn't suggest any H4 treated pine timber because it might not be suitable for indoor applications due to the chemical treatment?

I'm very conscious when I walk around in the attic. The current plasterboard lid helps mitigate missteps a little, but eventually I want to build a sort of cat walk – in my case a raised plywood access – to allow future maintenance jobs. In that regard I concur with @TedBear not to cover over the joists to facilitate orientation if one needs to move past the cat walk. Currently I do this all the time to lay cables or remove debris, and I want to preserve this advantage.

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/127173#Comment_127173

Hi @TedBear,

thank you for your contribution and different perspective. Maybe I misunderstood "cat walk" – I'm really just thinking of some permanently fixed plywoods (which I picked up from Gumtree) so that maintenance work can be carried out safely in the usual areas. Beyond that I'd do what you suggest and use moveable pieces of plywood to act as a bridging platform. Good to have your experience weigh in.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/133393#Comment_133393

Hi @TheHandySqirrel,

Hopefully, they should extend outwards above the batts as per the image below and meet each other. However, if they don't meet each other and there are gaps similar to the second image, then those need to be addressed, as cold/hot air can bypass half the thickness of your batt and reach the timber. Those gaps would really affect the R-value and diminish the point of going for the thicker batt in the first place.

No need for H3 or H4 timber inside; that's just for exterior use, where it will be continuously exposed to the weather.

Mitchell

TheHandySqirrel

https://www.workshop.bunnings.com.au/discussion/comment/137214#Comment_137214

Hi @MitchellMc,

my project has progressed, and I am now getting quotes for two options:

1) R4 batts laid in one layer, abutting as per your drawing

2) 2x R2 laid perpendicular to eliminate thermal bridging via the batts

Also, after talking to a few tradies in the area, I have decided to remove the top plasterboard layer. Most likely this was the original ceiling as the plasterboard is painted on the underside, and the joists must have been exposed. A later owner then added the lower plasterboard as the ceiling we see today.

BTW, I am opting for polyester batts as these are unattractive to vermin. I found quite a significant amount of rodent poo in the only area that had batts before. Although I'm aiming to close any entry points to the attic I'm sure I'll be outsmarted. Better not to offer them a hotel than chasing unwanted guests!

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