DIY insulation


Active Member
Looking to help a relative in need.

I have helped in trying to get all the problems with the house solved.

However any trade that comes arrives super fast to do a quote. They then disappear and are extremely hard to get hold of and most just ignore me.

Others who I eventually after weeks get hold of turn down the work.

That said it looks like given no one will take on any jobs I may have to attempt it myself.

On loft insulation if you go down DIY route I am concerned about condensation in roof after a DIY job.

Anyone have any experience doing it themselves and how they went about it?

There are also three wasp nests appear empty and a 2 small holes in roof felt lining that need patching.


Well-known Member
You need to ensure there is ventilation within the loft space and us proper protective clothing/mask when do insulation otherwise restively easy job. Plenty of video show how to do. Roofing tape will fill. the holes in the roof felt.


Well-known Member
Did mine and it’s pretty easy.
Photos are jumbled up, but the ventilation is done by opening a window and drilling a 70mm (I think) hole in the soffit and popping a vent cover in ,then up in the loft make sure that the insulation doesn’t block air flow to these holes (I used some tubing to carry the air but you don’t need to do this..
The bubble foil is a staple gun job with a pair of sturdy scissors, it’s made a big difference adding that .



Active Member
I see what you have done with the soffit - the house I am doing does not have anything like that though.

Looking at guides it says 50mm (2 inch) gap should be left between the roofing felt and the loft insulation for ventilation.

So would the method through the soffit be enough anyway?

Wondering if I just put some 100mm in-between ceiling joists leave on each side a conservative 3 inch gap then roll some 170mm on top at 90 degree angle to cross lay. Again leaving conservative 3 inch gap so all around will be a continuous 3 inch gap.

Thing is I cannot work out where the ventilation is coming from in the roof.

Yet they say leave 2 inches but where? They do not make that clear anywhere.

Do I take it a loft will have no ventilation? which is why the soffit fix has been done? Or is the soffit fix done because the insulation is now blocking ventilation at point between roofing felt and loft insulation in NatTheGooner photos? If so then what is the leave 50mm about? Then if there is no ventilation then surely that is causing issues anyway as there should be ventilation in the roof. As said I just cannot work out from where?

Hope my idea would work but worried after reading all the various forums etc as they generally say condensation is caused and the very last thing I want is to cause my relative any more damage to house.

Nothing there at present and thinking is even with 3 inch gap all around still a lot more than there at present.

Anyone able to shed some light on this?
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Well-known Member
The gaps they are talking about is when you fix something to the underside of the roof from the inside - like kingspan or the bubble foil. The air from the eaves (either vents or just existing gaps) needs to be able to enter the roof space and flow under the roof and between any additional under roof insulation (like my bubble foil).
so basically just allow a little gap at the front and rear eaves to allow a bit of air movement in loft. I used to only have two vents at the front and the loft was absolutely fine - then I stupidly blocked the flow with fibreglass insulation and it got a bit damp i then realised what I’d done so I pull some away where the ven were and it dried out in a week. Wind blows against your house and is pushed up to the soffits and some goes into the vents - if you vent the rear too some gets pushed out or vice-versa.


Active Member
Problem is the house is in a right state of disrepair. There are wooden soffits and one large hole from gutter overflow. This has caused a rotting soffit which has then caused open hole. So I guess that is one air vent.

Can't see where the air flow is for the loft. However there must be some right?

Looking at these wooden soffits, apart from that rotten wood hole there is nothing to indicate any way it's connected to roof space.

There are air bricks at ground level. I wonder if it would be that air goes in through those up the cavity to the roof space?

So looking at guides - once I put in the loft insulation the roof will be colder. Then when the heat from house below reaches loft it will meet cold air and cause condensation hence need for ventilation. But how much and where? Or is there sufficient ventilation but how do I know??

Would ask roofer but had three round all said no problem give you a quote next week. However then after waiting and then chasing them they are all not taking my call.
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Well-known Member
I would just put plenty of fibreglass roll insulation to start with, just leave a couple of gaps down to the soffit area (see the metal tubes in my photo). That will make a huge difference assuming there’s little or none at the moment. You won’t get condensation as the warm air is trapped downstairs where you want it and you‘ll have a cold dry loft (in the winter) the insulation will also help stop summer loft heat warming up the bedrooms below.
Its cheap to do but I would recommend a disposable all-in-one suit and face mask. Some loose Rockwool is handy for awkward spots. You could have it all done in a day.


Distinguished Member
Without knowing OP’s DIY ability, I would suggest caution on advising OP to carry out work.

Not withstanding put a foot through the plasterboard ceiling below, cover large electrical cables, and causing condensation problems, it is a pretty nasty job. I have down myself a couple of times, but I know what I’m doing, no offence @johnbower.

If this property has no roof insulation or sub standard, can you still not get a government grant towards installation or upgrade?

That requires installation by a competent contractor, I believe, which may solve your employment issue perhaps?


Active Member
Unable to get any grants. Local firms and even further afield want just too much too do job. Others have just ignored me.

So nothing or DIY route only way at present.

I thought it would be simple call local firm and they come do it.

Did find one however they just said they were going to roll insulation over existing. So thought why pay extra for just rolling insulation.

Definitely just rolling because I asked what about the things already there. The small amount of roll here and there very thin. They said they would just roll over.


It's the sort of stuff they'd charge you £1.50 a 25l bag to dispose of at our recycling centre so getting rid of it could add up if there's a significant amount of it. As ufo says the more the merrier, keep it.

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