New roof. No insulation between rafters question

Inforapennyinforapound

Just had new roof of concrete tiles on pitched semi.
Having read loads of posts on here about roof insulation(and Google ) I am totally confused.

The loft is insulated yet I hear and read advice about Kingspan(and other types of) roof insulation. The roofers are self certifying the work to comply with regs. No insulation between rafters…please please someone tell me what is correct/advisable?

I have read that the roof needs insulating and I have read that it doesn’t ….as long as insulation between rafters…
and just read on one council website that a loft is MEANT to be cold and draughty and well ventilated because this helps disperse any damp(their words not mine).

So,legally I guess all is ok BUT what do people on here advise? I guess I could quite easily fit Kingspan, or whatever, but not sure it’s a good idea.

Thanks in advance

stuart45

As loft as you have enough insulation at joist level, and the correct amount of ventilation it's fine.

travis-powers

If it’s just a loft then it’s spot on insulation in and on the joists.
 You only have to insulate the rafters if you are converting the space!

FreeBear

stuart45 said: As loft as you have enough insulation at joist level, and the correct amount of ventilation it's fine.

The minimum recommended level is 270mm of fibreglass or rockwool type insulation between the ceiling joists. This should have been checked as part of the self certifying process and brought up to spec if it wasn't sufficient. Loft insulation isn't hugely expensive, and putting an extra layer in is well within the scope of most DIYers (just be careful not to put a foot through the ceiling). But if your loft is boarded out, adding more insulation isn't so easy.

Inforapennyinforapound

Thanks all. So basically there is no need to insulate between rafters as long as suitable insulation between/over joists. Having said that I now wonder why people do the rafters as I have read stories on here about severe damp/condensation issues in the loft space caused by this very thing. Companies sell this stuff but appear not to warn about ventilation problems…

FreeBear

Whilst companies like Celotex & Kingspan do indeed sell insulation boards, and even have diagrams in their literature showing use between rafters, it is the architects and building designers who are responsible for specifying the finer points. If you are insulating between the rafters, the default assumption is that you are going to use the area as a habitable space, so need good levels of insulation to comply with building regulations.

If the loft space is just being used as junk storage (which most of us use it for), there is absolutely no point in heating it. Put the insulation down between the ceiling joists and keep the heat in the rooms that are actually used. Saves on heating costs.

travis-powers

Inforapennyinforapound said:

Thanks all. So basically there is no need to insulate between rafters as long as suitable insulation between/over joists. Having said that I now wonder why people do the rafters as I have read stories on here about severe damp/condensation issues in the loft space caused by this very thing. Companies sell this stuff but appear not to warn about ventilation problems…

90% of condensation problems in lofts comes from inside the house, I had cavity wall insulation fitted and it caused all sorts of problems in my loft space!
 As you have had your roof done I assume you have breathable felt so you shouldn’t have any condensation problems.
Roger Bisby of skill builder on YouTube gives a in depth explanation of condensation should anyone be interested.

Jeepers_Creepers

Inforapennyinforapound said:

Thanks all. So basically there is no need to insulate between rafters as long as suitable insulation between/over joists. Having said that I now wonder why people do the rafters as I have read stories on here about severe damp/condensation issues in the loft space caused by this very thing. Companies sell this stuff but appear not to warn about ventilation problems…

It isn't even a case of one or the other. If that is a loft space, then it should be treated as one - which is to keep it as well ventilated as possible. That way it'll be cold, yes, but also be dry, and that's the important bit. The insulation layer is added above the house's ceiling, so heat isn't lost to this chilly-but-dry loft.

When lofts are converted, then - yes - insulation sheets are added to the new ceiling, which often includes the slopes of the roof rafters. But that is done in a careful way so that ventilation is still occurring on the other side of it, between the insulation and the tiles. Again, without this ventilation, rot could set in.

So, as said above, if you don't have the recommended amount of loft 'ceiling' insulation, then it's worth adding. One thing to watch out for - don't stuff the material right down tight into the eaves, because that's usually a ventilation gap!