Loft insulation

[bobbley]

We need to get our log insulated. There is som insulation between the joists but this is boarded. In the roof part there are currently polystyrene blocks but they are always falling out.
Taking up all the boards will be a massive pain, so we're thinking of getting rid of the polystyrene blocks and having that insulation spray thing done. Where a company come in and literally spray the insulation all over the inside of the roof.

Has anyone had this done and does it work?

Bloody autocorrect.. log insulated?!! Loft!!

So many typos .... sorry... am using my phone to write posts!

Don't even think about it. Your roof is meant to breathe. The spray foam prevents this. You can take up the boards in half a day easy.

Yeah... dont even think about spraying the inside of the roof with foam... completely fucks the roof
Also that wont Insulate the house... just the loft space... so a waste of time and money and it will cost even more money to fix it in a couple of years
I am amazed companies are still selling this as an option

Wow thank you! This is why I love MN! It prevents me from destroying my house!

We are doing a huge refurb of a Victorian house and architect has recommended spray foam - why would you not recommend it and what would be the alternative?

Celotex/kingspan cut between the rafters.

If you are doing a loft conversion I would highly doubt spray foam would be building regulation compliant

Architect has recommended for external wall insulation throughout the house, underneath the floors and in the attic which has already been converted. Mmm - will need to ask more questions of architect I think

" Where a company come in and literally spray the insulation all over the inside of the roof"

Fuck no.

Google "roof spray foam."

If you don't think you can take up floorboards yourself, for example if you are infirm, get a carpenter in.

They will be held down by nails, and will lever up; or by screws which, ummmm, unscrew. Lofts are not difficult as they serldom have fitted carpets or large furniture.

Hoover it out and lay new mineral wool (the brown stuff treated with ecose that does not shed dust and fibres). Dust masks are essential when working with old fibreglass.

If you get an insulation company in they will just throw fibreglass down and not take anything up.

You can relay the old boards if not badly damaged, but if the loft timbers are shallow you will need to lay them on slabs of rigid foam. You can't walk on thick insulation quilt as it hides the timbers; but ply or chipboard can be laid on rigid foam, screwed through to the jopists, and is safe to walk on. If you manage to find a carpenter she can do it, but at this time of year a loft will be terribly cold to work in.

Ok thanks. What would you suggest for insulating the walls? This is part of major refurb so all plaster is off the walls anyway.

walls are most often insulated with rigid foam slab. It can be done with mineral wool which is cheaper but needs to be twice as thick for the same effect. You only need to the the external walls. It will be around two inches thick. Some plasterers do it and you will want the wall plastered afterwards. Plasterboard with skim has good fire resistance. You do not need wooden battens. The correct board will (should) have a metal foil skin to block water vapour. It is not expanded polystyrene, which is a cheaper material. If you have a look in a place like Wickes you can see and handle it. Some board is available with plasterboard factory-bonded to the foam. I definitely recommend having it taped and skimmed because this will give a better surface and is much easier to redecorate without damage.

It can also be applied to the ceilings of bay windows and porches if it is impossible to insulate in any other way.

Consider your electrical switches and sockets because they will need to be set further forward. The electrician can run new cables prior to insulation and fit the new sockets after. I recommend running horizontally them in oval conduit on the brick, because if you want to add an extra socket later, it is possible to access the cables without hacking the wall open. It is of course much better to include ample sockets at the time of insulation.

You can also insulate on the outside of the wall and protect it with cladding, but this is more expensive.

Diagrams of the correct way to do it can be found on the manufacturers' websites, such as Knauf, Kingspan and Celotex. You need an understanding so you can verify the installer is working to the correct standard.

Remedy any defects in the wall, especially damp, before doing it.

update

I just had a look at the Knauf website, and they seem to have taken the foam wall slabs off and just show mineral wool now. I should think that's because it's non-flammable, which I applaud, but it does need to be thicker than the foam.

You can also use non-flammable Foamglas slabs, but they are more expensive and seldom seen in the UK. There is a European factory, I have an idea it's in Belgium.

Thank you so much that's incredibly useful. Off to have a call with the architect.

After googling last night, I read on some forums that lenders are not happy to offer mortgages on properties with spray foam so another good reason to avoid.

Thank you

Op, I have a “room in loft” (it’s not officially extended into the loft as head height is too shallow) and found it to be not insulated at all when I moved in. Due to the roof needing a decent airspace to “breathe” and as such prevent damp and timber rotting I went with polystyrene boards. There are many different types to choose from and I would look into what you have and if it can be upgraded. My loft space is an actual room and it was counter effective to rip out all the interior so putting the polystyrene in from the eaves worked well for me and hasn’t budged since (decide the bottom parts with a little nail in each side of the rafters).