Hello, I have been a bit of a lurker here and now recently just in time for a new recession I got on the property market.

The house I recently bought to fix up is a small 2-storey mid terrace house, built around 1900-1920 I would guess.
I am considering internal insulation. The existing walls are 600mm solid masonry walls with lime plaster on the inside. The existing floor appears to be poured cement throughout although in one room where I have pulled the carpet there are sheets of plywood laid, I'm not sure what this is for.
In order to make the house cheaper to heat, my initial thoughts were to fix 40mm wood fibre insulation direct to the front and back walls of the house internally, covered with lime plaster again. This would provide a better U value overall and retain the walls permeability. The side walls are shared with occupied buildings so these wont be required.
The attic will be filled between the rafters with regular fiberglass insulation, unless anyone has a suggestion of a better alternative?

The floors I was considering leaving but since I will pull up all the carpet I am considering a thin 16mm sheet of wood fibre insulation again. I don't think a vapour membrane would be needed here either to help prevent rising damp, I would imagine there is a pre-existing one below the floor.

The external wall of the bathroom houses the shower also, I'm guessing I can't use the wood fibre here without some sort of vapour barrier behind the tiles.

I can take the floorboards up on the first floor and fix wood fibre insulation to the external walls between the joists too, although I probably can't avoid the thermal bridge through the timbers themselves and through the concrete lip the joists sit on. I was wondering then should I take down a strip of the drylined ceiling from the ground floor as I am running cables, then replace it with a breathable material sheet and lime plaster the ceiling here. This will allow the ceiling void to be breathable and hopefully prevent any damp on the joists.

For ventilation I will add an extract fan to the bathroom and kitchen. The windows are single glazed, I am thinking of drilling a few holes along the top side and adding trickle vent covers. This should provide enough ventilation to help prevent any damp.

Any advice would be appreciated as the house is completely damp free, not any bit of evidence of rising damp anywhere even though it has not been occupied for at least 5 years. I am very cautious of messing with the houses "environment" given that their is no issues with damp, but don't want to cause any issues now with my intentions to reduce the gas bill.

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Welcome, Hiceadha.

Is the 'attic' an attic (a bedroom) or a loft? You refer to insulating between the rafters (the sloping timbers), which you would do if it were a room, rather than the joists (the horizontal 'floor' timbers) where you'd insulate if it were an open loft. In the latter circumstances you have unfettered opportunity to insulate as Tony advises. If it's an attic room you are much more restricted, and would have to use something other than regular fibreglass to achieve the required U value.

Download (Building Regs) Approved Document L1B from www.planningportal.gov.uk. It will tell you what standards to have to achieve, and where you can find ''get-out clauses'. Most or all of the work you propose is 'Notifiable', because it is 'Renovation of a thermal element' - Renovation as defined by the Building Act meaning 'Adding or replacing a layer to a thermal element (any surface which loses heat to outside)'.

Where I live a Building Notice for Renovation of one or more thermal elements costs £150, although I gather this can vary. A quick search (which brought up https://www.no-use-empty.org.uk/advice-and-guidance/property-tax-and-vat/reduced-vat-schemes/ among many others) shows that it's worth checking the VAT position on any works you have done by a VAT-registered contractor.

With your 600mm thick walls 40mm woodfibre (for example Pavatex with a lambda value of 0.042W/K) would give you a U value of around 0.6W/m2K. Part L1B requires 0.3W/m2K, although there is some leeway where old buildings were built with water vapour-permeable materials are involved. Note, however, that some purveyors of woodfibre insulation suggest you should not use more than 80mm, which would only get you about 0.38W/m2K. Steico and Gutex apparently offer a slightly better lambda, though I have never used them.

Lots of experience and expertise here, so good luck! Look forward to hearing more.

Hi, yes, sorry, Anglo-centric assumption re Regs! Apologies. I don't know anything about Irish Regs, but in England

https://www.planningportal.co.uk/info/200128/building_control/38/building_regulations/3, says:

“Failure to comply with the building regulations

If you do not follow the building control procedures set out for handling your building work or you carry out building work which does not comply with the requirements contained in the building regulations, you will have contravened the regulations.

Prosecution and enforcement notices

A local authority has a general duty to enforce the building regulations in its area and will seek to do so by informal means wherever possible. If informal enforcement does not achieve compliance with the regulations the local authority has two formal enforcement powers which it may use in appropriate cases.
First, if a person carrying out building work contravenes the Building Regulations, the local authority may prosecute them in the Magistrates' Court where an unlimited fine may be imposed (sections 35 and 35A of the Building Act 1984). Prosecution is possible up to two years after the completion of the offending work. This action will usually be taken against the person carrying out the work (builder, installer or main contractor).”

Loads of people don't comply, knowingly or unknowingly, but I always advise clients to do so, for various reasons. (1) Because the law is clear. (2) Because, even if one feels the law is not clear, or is an ass, when you come to sell the house the purchaser's solicitor will send a load of enquiries, including asking whether you have had work done to the house, and whether it complies with the Regs, where necessary. If it complies but was simply not notified, then in England you can apply for 'Regularisation'. You pay something like full-price-and-a-half as a bit of a slap on the wrist, but you can end up with a retrospective approval. If the work patently does not comply, and you go for Regularisation, BC can ask for upgrades, which you may or may not be able to achieve.

Potential purchasers, when faced with non-compliant work, often do 2 things - (1) they ask for the vendor to take out a single-premium indemnity policy against any future come-back re non-compliance (apparently only do-able if BC are not already aware) and (2) they ask you to drop the price. Price drops requested can be out of all proportion to the alleged 'breach', but if everything is already delayed and you have another house to buy (etc. etc.) you may just have to take it on the chin. If you comply in the first place (or agree with your BCO that a 'diluted' standard will be deemed to comply) you will be saved this potential costly irritation.

My plans for IWI have hit a roadblock, after further reading on wood fibre insulation it is recommended that the entire wall must be breathable, after chipping a piece of the outside wall off I have no reason to assume its breathable here. While the indoor plaster is certainly lime, the exterior render shows no signs of bubbling with vinegar sprayed on it and there is about 3 different layers of paint from over the years, which I can assume aren't breathable.
I guess rather then breaking away all the exterior render it would be far more economical to look at exterior insulation, would wood fibre still be the way to go here?
I think maybe just 100mm and the gutters could be ok, though I will need to get up on a ladder and have a look tomorrow.

Although going with 40mm breathable wood fibre IWI still would be much cheaper and from reading online it seems that condensation isn't common in the u value is still below 0.5

Hi Tony, from running some simulations using software I downloaded it is clear that EWI is the way to go (attached), I will just do it down the line when it makes sense from a budget perspective.

Posted By: rosecottageyou do not want to go too thick on IWI with a standard house as you will lose much of the breathable element

Not sure what that means - Extra (or less) thickness of insulation does not affect the wall's breatheability (i.e. water vapour permeability), provided the chosen insulation material is permeable (wood, hemp, wool and other 'organics', or EPS, or spray Icynene); obviously if the chosen material is impermeable (all the other plastic insulations, and other spray insulations) then the wall becomes unbreatheable (if it wasn't already).

The danger with greater thickneses of IWI is that the wall loses the 'benefit' of being warmed from the inside, so becomes liable to interstitial condensation, which may never evaporate even in summer, hence build up year by year. No such problem with EWI thickness - the more the better for the wall!

What's that vinegar test? intended to detect lime rather than cement render? Interesting.

Roughcast cement render is generally considered adequately breatheable, because of micro-cracking rather than permeability (though even cement render can be permeable sometimes). Layers of recent-type plastic plastic masonry paints will counter that, but older limewash paints are OK. It may be possible to damage, scar or scabble off enough paint to allow breatheability.

I would not do IWI without a vapour barrier on the warm side ESPECIALLY not with natural organic insulants

The majority of manufacturers agree with you, Tony (and disagree with those who claim that anything 'natural' and 'breathable' wouldn't need a VCL), but generally the wood-fibre manufacturers claim that they are OK without a VCL. I would not like to guarantee it, but my experience over a few years and that of others I know over quite a lot more, suggests this is right.

Wood fibre does hygroscopicity tricks, which no one really understands fully (same with the cob farmhouse I live in - much more 'insulative' than it should be!)

Posted By: djhI've never got to the bottom of why my bale walls behave as they do.

What behaviour do you mean?

Posted By: Ed Davies

Posted By: djhI've never got to the bottom of why my bale walls behave as they do.

What behaviour do you mean?

I've never been able to explain the internal humidity in my house, specifically its stability. It seems to be less dry in winter than it 'should' be. There've been some previous discussions on here, for example:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14682
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15596

I am going to get a quote on external wall insulation in the coming days, if I can achieve a certain U value for the overall wall that is up to building regs then there is a possibility to apply for grant aid.
I do believe that with 40mm or 60mm of wood fibre IWI with lime plaster it would have been a fairly DIY job and probably wouldnt of led to condensation, although I lime plastered some areas of the building where the walls were bare brick like behind skirting boards and its more time consuming then I expected. Waiting a week between plaster coats.
With maybe 600 euros worth of 60mm boards I could of brought my external wall u value down to 0.5 from say around 2.1. A massive difference
The getting from 0.5 to 0.18 is where the money gets spent and to do this it needs to be EWI, considering the lesser chance of condensation and the fact the house could do with a new external paint-job anyway. No harm in getting quotes anyway.

I would yes, although in a mid terrace house the external walls are really the 3rd largest exposed surface area. The attic and floor being larger, the attic will be insulated but I will always have that heat loss through the floor unfortunately.

Thanks Fostertom, I will look into getting that done as part of the works. This would lead to a far more stable underfloor temperature of around 12 degrees I would imagine then, not influenced by frosty mornings.
Have you come across people retrofitting insulation to the ground floor below their carpets, laminate floors etc?
I note some of the wood fibre panels suppliers also offer wood fibre sheets for laying underfloors, around 35mm for acoustic and some insulation benefits?

Hiceadha, we insulated the floors of our previous old house and are doing the same in our current old house.

Timber suspended floor has insulation hung between/below the joists (like the loft but upside-down), this is done whilst crawling below, or by lifting floor boards, depends on space.

Solid floor is done by getting somebody else to dig it out, lay insulation and new solid floor on top. Optional underfloor heating.

Both are combined with fixing damp and skirting draughts.

Both make the floor feel warm and dry, so improve the liveability of the house as well as saving energy, though undeniably expensive and disruptive jobs.

Search back for previous discussions on this, good luck!