Best loft insulation

jblakes

Evening all, 

I am installing loft insulation as the old stuff is crap. 

Can somebody shed any light on if rockwool is better than fibreglass?, as in worth the price. 

Should I aim for 300mm or is more better? 

Kind regards
James

FreeBear

No real difference between rockwool and fibreglass in terms of performance. At the end of the day, it boils down to preference - Personally, I go for Knauf Eco Roll as it is made from recycled glass.

There is a rule of diminishing returns when putting in insulation. Whilst the first 100mm will cut your heat loss by (random guess) 25%, the next 100mm will only add a further 12.5%. Going to 300mm will gain another ~6%, and so on.. Current guidance is for 270mm, but as standard roll thickness is 100mm, 150mm, and 200mm, 300mm would be a reasonable target.Much more than that, and you need to be careful not to block ventilation in the eves.

jblakes

Thank you for your response. 

I was under the impression rockwool is better in alot of ways, which is why it's double the price of fibreglass 🤷‍♂️

markin

Some quotes from google

"In many ways, mineral wool is a superior insulation product. It has a higher R-value per inch compared to fiberglass, about a 22-37% higher R-value. It contains 70% recycled material, making it a greener product than fiberglass at 20-30% recycled material"

"Mineral Wool is supposedly rodent and pest resistant. Fiberglass is probably the best nesting material out there for rodents, they love the stuff."

"Rock wool can be more costly per batt but has a higher R value than fibreglass per inch; less health risks during installation; easier installation; it performs better for fire and sound and is less harmful to the environment."

"Key benefits of ROCKWOOL insulation include: Fire resilience – ROCKWOOL insulation is extremely resilient to fire. Our stone wool insulation used to manufacture fire cavity barriers and structural fire protection is capable of withstanding temperatures in excess of 1000°C."

I think for sound it could be better if you live near a main road or under a flight path, and i know its preferred in walls for sound.

fenwick458

IMO the cheapest stuff you can get (normally pink or yellow) is not nice to work with. whenever I go into a loft to work thats full of yellow/pink fibreglass I get a mask and gloves even if it's only for 2 minutes, and it still makes me itchy. it seems to come apart more easily when you move it  and just spreads around the air and gets breathed in
the slightly more expensive stuff (Knauf earth wool for example) is much nicer to work with, I sometimes wouldn't bother getting gloves and a mask out of the van, depending on how much work was to be done up there.
so thats something to consider, if you are installing it and if you think you might have to work around it in the future then get that type

FreeBear

markin said:

Some quotes from google

"In many ways, mineral wool is a superior insulation product. It has a higher R-value per inch compared to fiberglass, about a 22-37% higher R-value. It contains 70% recycled material, making it a greener product than fiberglass at 20-30% recycled material"

From https://www.insulation-info.co.uk/insulation-material/mineral-wool

Fibreglass u-Value 0.035-0.039 w/mK

Rockwool u-Value 0.032-0.044 w/mK

The difference between the two is small, and when laid to a depth of 300mm, it becomes academic. Use which ever one you are comfortable with.