Attic insulation: Should I remove wooden covers?

[TheHandySqirrel]

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).

[TedBear]

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]

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]

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]

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]

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!