Loft Insullation - Mineral Wool, Glass Wool, Rigid Board?!

[Steveb21]

Having the roof of our dormer bungalow replaced so will be taking the opportunity to refresh the insulation. There is current access to the dwarf walls via a hatch, but it is crawling space so awkward to work in. I think the previous owner's electrician left the current insulation scattered and poorly placed, it also looks very old.

While the roof is being replaced, my plan is to remove the current insulation, give the loft area a good hovering a lay new insulation. The joists are 150mm deep. I intend to lay 150mm insulation and then cross it over with another 150mm. Total of 300mm.

I am going to rule out using rigid board as it will be more time consuming and more costly than the other 2 options.

Can someone please explain to me which is the better item > Mineral Wool v Glass Wool? To confuse matters further i have even seen some items labelled as Mineral Glass Wool?!

Any particular brand/model to go for?

Much appreciated.

 

[RonnyRaygun]

No difference. They all have approximately the same thermal resistance.

Glass wool is more likely to make you itch if you don’t wear the correct PPE.

Recycled plastic is another option if you want to do all you can to save the planet.

Other than that, it mainly comes down to cost.

 

[phatboy]

It's that time of year where the sheds, such as B&Q, have very good deals on Knauf Earthwool - especially if you need multiple rolls. Although I have only seen 100, 170 & 200mm thicknesses.

I've found it reasonably pleasant to work with, as insulation goes... very little itching (When wearing shorts and t-shirt). It's a brown colour.

You are right to take this opportunity to replace and upgrade the insulation, and 300mm is about where you want to be. Do however, check that you don't block any eaves vents if present. We didn't have any, and so I insulated right into the new breathable membrane, and no problems to report 2 years on.

Glass wool is more likely to make you itch if you don’t wear the correct PPE.

I'm yet to find anything that doesn't eliminate the itching with glass fibre, maybe a space suit would do!

 

[JohnD]

The Knauf is treated with Ecose to prevent it shedding irritant dust and fibres. I use nothing else now. Many ownbrands are made by them. Look for the word "ecose" on the packaging.

 

[Koolpc]

Is it ok to lay insulation on top of any boarding in attic?

 

[noseall]

Is it ok to lay insulation on top of any boarding in attic?

Yes, although the movement of air beneath the insulation (between the roof joists) will negate some of the benefits, unless the void is filled?

 

[Steveb21]

Thanks. Am I correct in thinking Mineral wool gives better acoustic performance?

 

[noseall]

Thanks. Am I correct in thinking Mineral wool gives better acoustic performance?

That depends on the diligence of the fitter and how air tight one can get the product to fit. The advantage of wool type insulation is that it fills voids quickly and easily without the need for complex cutting and foam filling etc.

 

[mcprinter]

Picked a few rolls of Knauf 100 and 200 from B&Q yesterday. A fair bit cheaper than Wickes at the mo.
Made quite a difference to the acoustics in the car

Stripping out collapsed/filthy insulation is a lovely job.
1930s with no felt. A lot of the torching dropped and LOTS of dust.
Finding the Knauf good to work with.

 

[JohnD]

Old lofts are filthy

If you have the chance to board it while it is clean, it will be easier to keep clean in future

 

[mcprinter]

Old lofts are filthy

If you have the chance to board it while it is clean, it will be easier to keep clean in future

It is about 60% original with no felt and 40% extension with felt
Won't be storing anything in the old end. Only have a few bits to store and it is a bit awkward to get to with HW and header tanks