1) there are regulations to comply with for the loft and big fines to pay if not observed.

My suggestion is to repair/replace as few tiles as possible. Don't bother about sarking felt or lac of it. Insulate at ceiling level with 300mm quilt.

2) external insulation is a great idea -- definitely do it and make sure that it goes down good and low ( one meter below ground floor level would be good! ) and make sure that it joins up to the loft insulation.

Where you do have solid floors it is a very good idea to insulate down below ground -- the house will be warmer ( see thread on U values of solid floors)

Also a great idea to insulate under the floors. Make sure that no wind or air can get from into the house from under the floor.

Ref loft -- as soon as you put a floor in it and insulate it then it is considered as a loft conversion so must have compliant stairs, means of escape ventilation etc etc.

Hopefully the inspector will be nice to you ask him lots of questions and he should help you.

Any suggestions for someone to install external wall insulation to a single terraced house? All the companies in INCA seem to be too large to bother with tackling a small project. We are in North London

Making slow progress on our project. Steep learning curve.

Question about roof insulation.

We are thinking of putting the boiler and thermal store in the loft, so it would seem to make sense to insulate along the roof pitch, rather than horizontally. Is the lack of roofing felt going to be a problem here? Do we have to strip the tiles off the roof or is there another way to deal with this? I was planning to use Celotex or Kingspan.

What I understand so far:
We will need to leave a 50mm gap above the insulation and a gap over the roof ridge to allow for air circulation. Correct?

Planning to install a roof window. Most probably Fakro triple-glazed. Presumably we need to carry the insulation round the edge of the frame? i.e. between window frame and tiles, under the flashing?

Now to the wall insulation
We are planning to build a single storey rear extension, so the external wall insulation will have to wait until that is built. However, there is some work that is going to affect the walls. Moving bathroom from rear to front of house, so there will be some new pipework. Also want to get the gas and electricity meters moved outside. Should we place a thick board, or some such thing behind the meter boxes to prepare for this? Clearly we don't know exactly what the depth will be but I guess we could overestimate and replace with a thinner board later. Also What do we do about the pipe entry points?

You may not need to worry about the roof bit as it is likely above the level of the loft insulation?

The bit of wall would be best insulated so long as you can agree it with the neighbour even 65mm of pur board.

Hope the project works out ok for you.

I would not put the boiler in the loft! Think about a combi? and fit it in the house easily accessible, its heat loss is your gain. Cheaper too.

Also be careful that you dont do a 'quiet' loft conv and get caught -- heavy fine or cant sell house etc

Great. It is technically very difficult and time consuming to insulate up and down the roof slopes but it can be done.

Solar hot water is a good idea but the wood burner could be contentious especially in a town/city centre location but I am very anti wood burning.

To best practice or building regs? You may regret doing without these in the future.

50mm air gap, 25mm pur/foil insulation between rafters, 100mm pur/foil insulation under the rafters, vapour/air barrier linings.

Rot more likely caused by roof not being watertight (broken/missing slates). 20mm + 100mm of insulation?

Keviin.

Acoustic stuff is, I think, not as good an insulator as thermal stuff (this could be nonsense but picked it up somewhere) so you may need a slightly thicker layer to get the same result.

S.

You should aim at 50mm but ok for it to be 25 min in places not too often.

I dont see you changing the under Slater's felt? That would virtually mean re roofing.

So it is OK to keep so long as you have the 50mm air ventilation space we have talked about.

Breathable felt makes horrid noises if you dont tape the joints, but they need taping to make it work properly too.

Your felt is not breathable

Draughts in the void will not significantly detract so long as wind cant get the wrong side of it all and there are no gaps misses or cracks.

Use a vapour barrier to ensure no vapour can get out, taping the joins is a faff and not so good as a sheet of thin polythene.

Use the same insulation in the ceiling it is only small anyway?

it will be

I have very rapidly become an insulation bore - but I guess this is as good a place as any to go on and on....
It is so helpful to have access to other people's thoughts and experience (if they choose to answer).

In my attic rooms, under the pitch of the roof, I am beginning to think that I must put 75-100mm insulation below the rafters (I was hoping to get away with 50mm, or less). How much is the warmth noticeably increased for each 10mm of insulation I wonder - or are other factors, e.g. draughts far more important?f Is it worth also insulating the low sections of outer wall - or far more important to double-glaze/draughtproof windows? (There will also be a skylight in the roof).
With an insulated plasterboard incorporating a vapour barrier, the barrier will obviously not be continuous where the boards butt together at the rafters. Is it better to have a polythene sheet between an outer layer of PUR/foil and normal plasterboard? The sheet will have to be punctured at attachment points, won't it, but will be squashed against the rafters by the plasterboard which will grip its screws tightly so that nothing can get through(?)

Tony says a thin sheet of polythene is better than taping the joints....
Maybe the answer is that joints have to be taped if an insulated plasterboard is used, but not if a polythene layer is placed between the underrafter layer of PUR/foil and the plasterboard. Hope Tony replies to Mike George.

Could it be better to put the polythene between the two layers of insulation, before the underrafter layer is attached. Why is the inner layer of insulation foil-backed, I wonder.

I have to stop wind from above - coming through the Slaters' felt and down the edges of the rafters (where inevitably in some places the between-rafter insulation will not fit quite snugly) and "vapour" from below, including clouds of steam from baths and showers.... How difficult/vital can this be.
NB the rafters are shallowest (less than 70mm) and the roof height lowest in the proposed bathroom.
Must remember the mantra: any insulation is better than none.
Hm. Must stop musing and take ACTION
Regards to all. I'll be back....

Hello Kevinwatcher - I have exactly the same problem as you - 70mm thick rafters and trying to insulate to a high standard but reducing head height as little as possible. Im trying to get some information together before going to chat with Building Control.

If I have understood it correctly the thinnest system I have found is a Celotex system with 50mm between rafters, 65 over, 25mm battens to give an air gap then plasterboard. To get my 50mm ventilation I will have to make the rafters deeper by fixing battens below them. Seems awfully complicated. I think I was expecting some sort of super material that would solve this more simply - and thinner.

Anybody got any better ideas??