Green Building Forum - Housing - Renovation

External Wall Insulation/window installation

David Lam — Sat, 08 Oct 2022 09:23:23 +0100

Can anybody help please. I have some new windows being installed into my house in 4 days, and I have not spent enough time researching things.
I would like to outset the windows from the masonry to allow future EWI to meet it and reduce the cold bridge.
I plan to have 80mm insulation (probably mineral wool, but maybe EPS).
I have installed some brackets to allow this, as per the window installer's request.
The window installer has asked for a 25mm recess, so the EWI would sit 25mm out from the window.

Is this enough? I've already had feedback from MarkyP (thanks Mark!) who has said 50mm would be better to allow beading for the EWI. Do others agree?
Are there any other comments?
I'll try to add a drawing and photo to show you what is going on.

Thank you so much in advance. Any comments welcome.

David

Starting EnerPhit 1900's house - am i a massochist!

fredd — Sat, 03 Sep 2022 09:11:06 +0100

First post, hello all!

We have bought a detached turn of the century, maybe a little younger, house that I am planning to to a deep refurb and try to follow enerPHit as closely as possible. I have an unlimited amount of questions and am hoping for advice !

My day job is building new houses so you may think this should be trivial but the more i read about passivhaus and enerphit the more it feels like im about to cross into a third dimension!

Couple of questions right off the bat that im mulling off the bat. Windows From what I have read its best practice to fit the window not onto part of the outer brick skin but completely in the cavity so it is surrounded by insulation.

Q1 Now bearing in mind window frames are 70-90mm wide How then in the front weather sealed when there is a gap ?

Q2. The sides of the window can be fixed with straps, which leaves it dangling in the air. What is there for it to sit on other than cavity wall quilt and a weak plastic cavity closer ?

Thanks in advance and i apologise already for the many many questiions that are coming...

Fred

CWI or EWI? when combined with existing CWI/IWI

munnum — Mon, 19 Sep 2022 10:45:25 +0100

Hi, i have been reading back through years of advice on your forum and am hoping someone could advise me what my best option is here.

We have a two story detached house, built in 1999 with twin leaf blocks,100mm cavity partially filled with 50mm aeroboard. On the internal leaf is a dot and dabbed 50mm plasterboard of which around 37mm is insulation material (blueish in colour). The blocks are not plastered internally. The external finish is plastered and is done well. It was my parents house and we are now moving into it.

I was thinking of filling the cavity with PU foam which would improve airtightness and has a higher insulation value than beads. The beads in ireland are grant-applicable and the job would cost me ca. 1,000eu to do with beads versus around 10,000eu! with the closed cell PU foam (not grant applicable).

The house isn't really that leaky, i don' recall any draughts growing up there, we will be changing the windows, it has concrete subfloor and first floor.

I'm thinking of going ahead with the beads, but the rep for the PU foam, mentioned that with the dot and dabbed board inside that there will be a lot of air passing through to the blocks and the beads will just let it through, hence making them not worthwhile at all.

The foam seemingly degrades overtime too (according to my forum research)??

Im open to EWI too, it just seems like a huge job and im not sure if IWI, CWI and EWIis a good mix??

Ceiling-level airtightness membrane with cold loft

wookey — Thu, 22 Sep 2022 14:10:47 +0100

I am retrofitting a 1960s detached house.

I am trying to decide how best to deal with airtightess at the upstairs ceiling level. It's not terrible with just the existing plasterboard but it has been hacked-around where the loft hatch got moved. I've put some blowerproof on the joints but interesting that hasn't worked perfectly. Seems like 2 coats is a good idea.

My main question is about putting up a membrane, and the pros/cons of plastic sheet, breathable roofing membrane or smart intello-type membrane.

Obviously best practice would be pull down all the ceilings, take off the internal wall-tops, make a truly epic mess and put a continuous intello sheet across the whole ceiling. (Or decide to fit a warm roof). I'm not doing that :-)

However I am considering putting up a membrane in each room between the walls (wet plastered block so reasonably airtight) under the existing ceiling, tape it to the walls then put in a new ceiling with a ~20mm service cavity for light wiring.

I have already done this in the main bedroom a few years ago. I just used cheap green polythene sheet from the builders merchant, held up with orconF during installation (then screwed battens). So there is no vapour permeability. The question is how much does this matter in a building with MVHR and a ventilated loft?

A vapour-permeable membrane would be more robust long-term as it would allow drying down as well as up (in the summer at least when the loft is warmer than the house - not sure if any vapour would move down towards the warm side in winter?

So I _could_ buy a roll of intello but it's quite expensive and I'm not sure there is much point in this application.
I do already have a roll of Cromar Vent3 roofing breathable membrane which is specified as wind-tight and breathable with an Sd of 0.02 m
https://www.cromarbuildingproducts.com/products/vent3/
What it doesn't specify is whether this stuff is deemed airtight.
I guess I could do a test.

Has anyone tried using these roofing membranes as airtightness membranes? Is it a bad idea for some reason?

Apart from being 2.5 times cheaper than Intello, I can easily go to screwfix and get some more if needed (Â£114 vs Â£249 for 1.5 and 50m)
I also still have loads of green plastic which is very cheap, and wider so fewer taped joints.

I think the impermeable plastic is probably fine under normal circumstances. If there is any condensation then it'll go into the plasterboard and diffuse then evaporate into the loft. I know my loft is well-ventilated due to a major leak a few years ago (in Jan, which dried out by about March without any significant harm occuring to timbers). A leak like that again would presumably dry out more slowly with a vapour-impermeable membrane in place (but also with a vapour-open one and a second ceiling).

So what do we reckon. Is just plastic really a bad idea here? Any reason not to try something like Vent3? Are you all going to tell me to just go any buy a load of intello?

1800s Tile Hung Timber Frame Insulation

michaelf — Wed, 08 Dec 2021 10:26:14 +0000

I have recently moved into an 1800s house with solid brick built ground floor and a timber stud frame first floor walls that are tile hung.

The lath and plaster is blown in places and I have done some initial investigations and the current structure appears to be as follows (from the outside) - Tiles, bitumen felt, mineral wool, lath and plaster, skim coat. The studs are 140mm deep.

The tiles are in good order and so removing them to replace the bitumen felt, etc. would be costly prohibitive so I was planning to tackle this from the inside. My plan at this stage is to remove the lath and plaster, fix timber stop battens, install 90mm Kooltherm K112 (or similar) to leave a 50mm air gap to the felt/tiles and cover with insulated plasterboard with an integrated VCL.

Does this sound like a sensible solution or am I potentially introducing issues with the timber structure? Is there a better/more cost effective way to do it?

Insulating suspended timber floor from below

KmcK — Fri, 30 Sep 2022 14:59:48 +0100

Hello,

I've been reading the various threads about insulating suspended timber floors, and thanks to everyone who's contributed - we've learnt a lot. Our situation is slightly different to the other threads and we'd appreciate some thoughts on the best options for us:

We're insulating the full ground floor (approx 50sqm) of a Victorian house, with suspended timber floors that we can easily access from below - there's a cellar running underneath the full house. For this reason (and because we're living in the house and couldn't manage the disruption or cost of taking up the floors) we'll be insulating from below.

The joists are 180mm deep, and we've already had a re-wire completed, with most electric cabling running underneath the joists, but some notched through the joists. We've also got some heating pipes underneath the joists.

We're improving the ventilation to the cellar as part of this work, but have a bit of damp down one section of the external wall. The joists run parallel to the wall, and the closest joist is about 50mm away from the wall

Finally, our finished floor surface above the floor will be stripped wooden boards. We've got some fairly gappy boards, and may look to seal these from below or from above, if it's worth the effort.

From what we've gathered from the other threads, our approach will be to use an inorganic quilt insulation between the joists, and to staple a breathable membrane below the joists to help with wind wash of the insulation and to ensure any moisture can escape. Our questions:

- the insulation material we're planning to use is rockwool, or Earthwool (which is slightly cheaper) - any reason to pick one or the other? We plan to use 200mm which compresses slightly to fill the depth of the joists

- for the breathable membrane there are lots of different ideas across the threads and elsewhere online, from a weed membrane, through to a Pro Clima membrane, and so a lot of price difference. What do we need to look for, here? Balancing out cost and performance, would Tyvek Housewrap work? The Pro Clima Solitex Plus comes in at circa Â£4/sqm, whereas the Tyvek is Â£1.63/sqm, and the weed membranes might be cheaper than this?

- I've seen in one thread on here the idea of using masking tape from below to seal the gaps between boards - is this worth doing, if you're insulating and putting a breather membrane below? We'll likely have some minor liquid spillage onto the floor above (we have a toddler!), so if it's worth it to prevent water interacting with the insulation then we might do this

- for the section of damp wall, what do you recommend? As detailed above, there's a joist running parallel to this wall at about 50mm from the wall, so we could foam this gap with an air-tight foam, but I don't know if that's a good idea? If we were to do this, would you recommend running the breather membrane below this, and therefore taking it to the external wall, or would we be better taking this to the closest joist to the wall, but no further?

- how important is taping the joins of the breather membrane and how important is taping it to the external walls? We're having a tradesperson do this work for us, as we have hectic jobs and the toddler, so keeping the work as simple as possible is best for making sure it gets done well

- we'll chat to our electrician about the cabling notched into the joists, and whether this needs to be de-rated

- finally, do we need to consider whether we're making the floor too airtight? We don't have mechanical ventilation, so will be relying on opening doors and windows to ventilate the house above. We don't have a woodburner or anything that would further compromise our air quality.

Thanks in advance for your ideas

How dangerous is a badly constructed VCL

Peter_in_Hungary — Sat, 13 Jun 2020 13:07:09 +0100

I have a roof that needs the insulation upgrading. The roof make-up in to out is
T&G 12mm planking
VCL
100mm x 100mm rafters with mineral wool between
20mm sarking boards
battens and slates (concrete/asbestos)

The plan is to remove the battens and slates and add
50mm x 150mm (fixed vertically) with mineral wool between
Breather membrane
battens and new slates.

Using Ubakus.de shows no problems - however if the internal VCL is removed then serious problems occur on the inside of the sarking boards if the internal RH goes above 50% and the external temp goes below +6.

Up until now the place has been used as a holiday home with minimal to no winter usage but now the plan is to use it year around so interstitial winter condensation could be an issue. If the VCL was put up with the same work quality as the rest of the works then there will be holes and bad joins within the VCL

I would rather not take down the T@G or remove the sarking boards due to the work and expense involved

You read here about electricians and plumbers making holes in the VCL with gay abandon but how much damage (or poor installation) can be tolerated in a VCL before there is a danger of interstitial condensation?

A palace for bats and pargeing

ralphpr — Sun, 11 Sep 2022 20:14:18 +0100

Hello all

I've been lurking for years and finally have an interesting project.Your help is sought.

It's a rectangular 550 mm wall solid stone built 110 sq m cottage in Wiltshire with bats in the attic.

Permission was granted in the teeth of the tree officer to extend it as an L shape ( a double pile was sought but encroached on two protected oaks so the wing doubles it in size hanging down on the eastern wall allowing good southern insolation to most windows)

The dream of making it EnerPHit was stymied when we realised that 200mm of floor insulation would have required Â£30,000 of underpinning due to the lack of foundation -so we applied to demolish the unlisted building and replace it exactly as before benefiting from the VAT newbuild concession.

And we nearly got away with it; on the eve of planning being granted, someone mentioned bats.

Â£5,000 worth of surveys ( that found five bats and their DNA) and six months delayed we have reverted to the original planning and are out of the ground with the extension - alas only 100 mm full fill thermal block cavity as we need to match the stone coursing of the undemolished cottage on the outside, but 200mm floor fill.

The cottage now has a reinforced concrete floor tray with a 125mm upturn allowing for 200mm there too and 125mm IWI. Triple glazing throughout to replace the Critalls.

My first question is what to do about the bat attic.: the licence to remove them will come in November by which time we will have completed the shell.

Do we strip the roof then and retile using a warm roof insulation or is it feasible to have an icy bat palace attic sitting on top of an insulated two floor box? The extension will be bat free and can have a warm roof.

Second question on pargeing - I'm aiming for 3Ac/hr to be realistic for MVHR . I need an IWI soultion to optimise the 125mm.

Many thanks

Ralph

Cracked sandstone repairs.

Davycrocket — Sun, 21 Aug 2022 08:56:37 +0100

Having chipped off the bottom 2 meter of cement render I've discovered some quite alarming cracks / voids in the stone work.

I'd like to think I can repair these areas with your help.

What is the method for these repairs please ??

Thanks in advance

forum members clever solution to secondary glazing

jamesingram — Mon, 12 Sep 2022 20:29:26 +0100

Hi , I've forgotten and or lost the link to the guys site that came up with a simple fix for secondary glazing on sash windows
Could anyone help me out
thanks

Exploiting thermal mass for cooling

wholaa — Mon, 15 Aug 2022 09:13:57 +0100

In the UK, are spells of hot weather ever long enough to make the thermal mass of concrete blocks a disadvantage for keeping a house cool?
Should we be adding thermal mass to an upstairs bedroom, eg. replacing drywall with real plaster on the blocks, or extra dense plasterboards to reduce overheating?

Limecrete Slab & Parquet Flooring

jamesmonk83 — Mon, 25 Jan 2021 12:28:47 +0000

Hi All,

We're renovating a small victorian terrace house and have put down a Limecrete floor system on the whole of the ground floor approx 18 months ago (provided by Ty Mawr). There is also a wet underfloor heating system installed in the slab (boiler not currently connected).

We're now at a stage where we're looking at the floor covering, our first choice would be an engineered wooden parquet floor which we've found. We've spoken to several local flooring companies about installing it but there seems to be lots of confusion over working with Limecrete.

Several contractors have said that they have to put down a self leveling compound otherwise the slab will dry out the adhesive too quickly. Obviously this isn't an option as it will affect the breathability of the floor, I've done some research and there doesn't appear to be a breathable option on the market? One contractor said he would have to put down a sub floor over the Limecrete which we want to avoid as we don't have much room to play with before the finished floor level starts to end up higher than our external door sills.

So my question is has anyone successfully installed a parquet floor on limecrete with just adhesive or is this not possible/advisable?

Any help/advice would be appreciated.

Thanks,

James

Most eco loft insulation

neelpeel — Sun, 07 Aug 2022 12:03:00 +0100

I'm going to help someone topping up their loft insulation and filling in the many metres of gaps. I will need to fill up the battened walls and much of the floor in the eaves.
They are keen to use sheeps wool insulation as the assumption is that it's the greenest option. There was discussion on this umpteen years ago on the forum, but what are the thoughts these days? Any new eco wonder products around?

Gable end again

Davycrocket — Fri, 15 Jul 2022 08:39:08 +0100

Hi I'm looking for advice from people who have "Slated" a gable end wall please. Not sure that's the correct term but I think you'll understand ?
Firstly, The walls are lime internally.

The gable itself faces straight into the worst of the west cumbrian weather and has numerous sycamore trees nearby.

Add to that it's delicate nature having many cracks in the current render and the red sandstone underneath making me worry about chipping the render off and starting again. It's had scaffolding up numerous times in various peacemeal attempts to stop water penetration.

So back to my original question.

Would a natural slate and breathable membrane covering be a good way to tackle this problem and if so is there any helpful information online you can share please.

Decorating corner beads

kristeva — Sun, 10 Jul 2022 18:54:01 +0100

Hi all

I purchased some corner beads from Wickes as I'm plastering one of my fireplaces (gypsum). The room is a mix of lime and gypsum so I was thinking of using clay paint to achieve some kind of consistency. I assume the very tip of the bead will be showing after the walls are skimmed, and I was just wondering if anyone knows if the clay paint will take to the galvanised steel? I guess a light sanding will be in order?

Or am I going down the wrong road here? Any experience much appreciated.

Cheers

Bedding limestone pavers in wet Limecrete

tvrulesme — Wed, 09 Feb 2022 12:24:52 +0000

Just finished excavating a floor ready for limecrete. I'm going to have 150mm compacted foamed glass, underfloor heating pipes followed by 75mm of limecrete. On top of this will be 20mm limestone pavers.

I came across this today where someone laid the pavers directly in to the limecrete.

https://limewindow.blog/2012/11/12/limecrete-floor-with-flagstones/

Seems like a great idea to me, saves on waiting for drying until floor surface goes down and also saves a little bit of head height loss.

Can anyone tell me any reason not to do it like this and wait for the slab to fully dry before laying the pavers?

Breathable membrane for air tightness on solid wall

jackmccabe — Wed, 29 Jun 2022 20:35:34 +0100

We are carrying out internal wall insulation with insulated plasterboard on timber battens to our Victorian maisonette.

The wall is ~400mm thick (quadruple brick?) but has areas where the brick work is in a bade state and where windows have been bricked up.

So my question is about how to achieve air tightness behind the insulated plasterboard, I know a parge coat is usually recommended but considering the unevenness in the walls it would be quite costly with materials and time.

So I was thinking of putting a breathable membrane behind the timber battens directly against the brick, is that a bad idea?

Insulating cut off chimney

jackmccabe — Wed, 01 Jun 2022 19:33:21 +0100

Hi, I realise that chimney insulation has been covered extensively on here but I am not sure if the general advice applies to our situation.

We have 3 storey Victorian maisonette (4 floors total) that has a Fireplace in each of the 6 rooms on the party wall.
We have insulated the roof and are going to be doing IWI insulation throughout and fitting an MVHR system.
Airtightness is obviously a big concern so ensuring the chimney breast is insulated and draught free would be great.

So the few differences I see to the usual are:
The chimney breast has been completely removed below us.
There is no loft space as the ceiling is vaulted.

I am thinking of sealing each flue with either a chimney balloon or rockwool shoved in a bag,
then thinking of filling each flue with EPS beads and capping with a rain cover?

Does that sound reasonable or should I seal at roof level and add air bricks in the top 2 rooms?

Velux Installation and trimmers

Victorianeco — Fri, 10 Jun 2022 22:49:49 +0100

I've just ordered a pair of Velux PK10 top hung Windows to go next to each other.

The existing roof is constructed of 3x2 timbers.

Double trimmers will be needed to be in-between the 2 Windows. But would I also need double trimmers on the outside and the top and bottom?

Any thoughts please?

Cavity Wall Insulation

richo106 — Tue, 03 May 2022 21:05:39 +0100

Hi

We are starting our 1960â€™s bungalow conversion later in the year, currently my bungalow has 70mm cavity with blown insulation. The extension above (stepping brick/block out 15mm each side) and to the side will have 100mm and I am planning to use Celotex Thermaclass 90 cavity wall insulation, I just wondered if there is any more alternatives to look at?

Another note regarding insulation for the floor, I have planned to have 200mm PIR but it is more cost effective to use 300 EPS 70, has any body got any thoughts on this?

All help and advice greatly appreciated

Tile hanging over EWI

tony — Sun, 01 May 2022 19:18:42 +0100

How would you support tile hanging over 100mm of EPS

I am thinking of hanging vertical 47x50 battens from the roof rafter feet long fixings at 1.4m c/c recessed into green EPS, membrane and horizontal barrens at 120mm c/c for plain tiles.

Will that work?
What to at the bottom?

Wood fibre panels between rafters-full depth without ventilation (?)

studiodub@mac.com — Fri, 08 Apr 2022 15:24:07 +0100

If one is trying to maximise thickness of breathable 'wood fibre' insulation between rafters -ie full depth- is a small 'gap' left between each timber sarking (roof) board sufficient ventilation in lieu of a vented gap above the insulation? If so what sort of gap is required between the boards? Is this approach/detail acceptable to Building Control...I have heard it referred to as 'Scottish Practice'..!

Related to the aboveâ€¦is a gap above 'wood fibre' insulation actually required if one uses a breather membrane such as 'Pro Clima' atop the roof boarding in a full roof retrofit? Context: Traditional building with Planning restriction so cannot add more insulation atop rafters and need to maximise headroom below.

Bathroom - Solid wall insulation - Damp

tvrulesme — Mon, 18 Apr 2022 06:18:16 +0100

In the process of renovating an 18th Century Listed Building and attempting to go traditional and breathable where possible.

A later extension built in the 1920s is of solid wall construction and has no DPC. We are putting a bathroom (shower, WC and sink) into this extension and I'm concerned about damp as an existing stud wall was completely rotten at the bottom. We've sorted the ground levels outside which were high and the entire floor will be breathable Limecrete with limestone pavers.

As a listed building I am not able to insulate externally but would like to insulate the internal walls and wondering if someone could recommend what to use?

Wood fibre for the bathroom seems to be out given the moisture content of the bathroom so should I just ignore breathability just for the bathroom, get the best extractor fan I can and effectively tank the bathroom with tile backer boards or is there another way?

If I put tile backer boards on a treated timber frame what insulation could I use behind? Breathable would be pointless because it could not escape through the tile backer boards.

Advice on Internal insulation on unfilled cavity

Violet3 — Sun, 17 Apr 2022 11:52:44 +0100

Hello,

I am new to this forum and also to house renovations. I am looking on advice for the best way to insulate some of our external walls, focusing on the northwest facing front room first. The house is non-standard construction, downstairs is brick and thermal block with a very small cavity (<50mm). The upstairs is timber frame mansard and it looks like the mansard sits on the upper floor joists. We have been advised against getting the cavity filled due to how small it is and also it is not capped at the top so any pumped insulation (beads or similar) would migrate into the cavity. We will be getting the mansard insulated with PIR insulation. The downstairs floors are concrete.

For downstairs I am considering the PIR backed plasterboard (37.5 cm thickness) just straight onto the wall, but worried whether this will cause any condensation issues. The room is quite narrow and the door frame is only 5cm from the front wall so we are quite limited on the thickness. I also looked at the Spacetherm wall-liner but it is really expensive so not sure whether it is worth it (~Â£800 versus Â£200 for the insulated plasterboard). I am also not sure whether the mansard roof insulation will overlap the upstair floor joists at all and whether we would need to do something about that space if it is left completely or partially uninsulated.

On the front room wall we also have a bow bay window with an unfilled canopy and this seems to be quite a large source of cold air too - any advice on how to insulate this from the inside and also the window sill from the outside?
Also to complete the picture, for the concrete floor, we will probably add minimum thickness solid insulation again and wood floor on top.

Ultimately due to the odd house construction I don't expect it to be perfect but hoping there are ways to make it a bit warmer without creating condensation issues. Also my DIY skills are not great so looking for the least complex solutions that would still make a difference please :).

Thanks in advance for your help.

Velux Cabrio

Victorianeco — Sun, 08 Nov 2020 21:43:08 +0000

Anyone have any experience with these? Or have an alternative suggestion?

Thanks

Major renovation and extension of 1960's detached house

kaicasswell — Sun, 03 Apr 2022 18:12:38 +0100

Looking for any input on the following design:

The old part is cavity wall - uninsulated - and the new part (shown as the whole right hand half of the elevation pdf) will be solid concrete block 220mm wide.
200mm EWI all around. with 65mm XPS down to foundations. The floor is 150mm kingspan type with screed on top. The roof will be kept as it is, and the loft insulated as much as possible (no loft conversion, ignore the velux shown). Air tightness inside with lots of tape/wet plaster. MVHR system.
The new extension also sits on a new ICF basement,
Once we have the shell watertight and finished i was planning on measuring the heat loss before deciding on final heating arrangements, but probably small gas boiler/unvented DHW or thermal store/UFH/solar thermal and maybe PV/battery.

First floor void holes and gaps

DWHITE — Fri, 01 Apr 2022 13:34:38 +0100

Hello everyone. First time poster, long time lurker etc. Will try to keep this brief but am looking for some guidance from the experts.
This is my first attempt at some home renovations on my first home so please be gentle. Limited DIY skills being a simple data analyst but learning as I go. I've started in our spare bedroom on the first floor which is my covid office. Cold draughts from under the skirting, particularly from the wall which looks out over the front of the property. I've been using posts within the forum and the excellent readinguk.org posts as guidance but wondered if I could get your opinions on how best to deal with a couple of specific issues I've hit.

Context: 1990 end of terrace 3 bed house. Block and Beam ground floor. Dot and dab plasterboard. Aircrete inner leaf. Integral garage... Can't think of much else but assuming I've captured most of the bad-house-bingo marks there.
So far Iâ€™ve had the cavity fully filled (60mm) with polypearl platinum eps beads and have been working on filling the loft with 500mm of insulation although I will be going back up there to address some of the penetrations.
I am attempting to do the actions listed in the following:
https://readinguk.org/draughtbusters/going-further/first-floor-void/
https://readinguk.org/draughtbusters/going-further/dot-and-dab/
https://readinguk.org/draughtbusters/basic-techniques/walls-and-windows/

Question 1: How best to fill an 8cm diameter hole within the aircrete block? I can see the outer leaf brickwork through it.

Question 2: How best to deal with a 20cm diameter hole which has both cables and pipework going through the wall and entering the roof space above our front door entrance and downstairs loo. The aircrete block is crumbling here and around half of the hole is covered in EPS beads from having the cavity filled.

Question 3: Between the inner leaf block and the ceiling/wall plasterboard joint of the room below there is a gap is a 2cm gap followed by a 28cm drop to the next aircrete block where I can see a metal lintel. Would you run gap foam around in a similar manner to the readinguk.org first floor voids article or would you attempt to put something down there such as insulation around the metal lintel?

I am trying to publish photographs of the above areas however it is my first time posting photographs on the forum.

How to insulate a small industrial unit

GarethC — Mon, 14 Mar 2022 20:11:09 +0000

Hi all,

Business at my small startup has been good (our first proper winter selling season just past), and I'm moving into a small industrial unit (10 metres by 5 metres, which is still over three times larger than the extended shed I was producing in before).

However, it's going to be a nightmare to heat. The rear wall is just solid brick and stone. The end walls are breeze block or brick, but at least not external (other units on other side of them). The near wall is breeze block with a double, very poorly fitting garage door. The floor is bare concrete and the ceiling is some kind of corrugated metal.

My product is an energy saving one, so I'd feel a right hypocrite if I didn't insulate it at least to an extent.

First off I think I need to fill lots and lots of gaps, particularly where ceiling beams meet the walls and around the garage door. I'm thinking of stuffing rockwool in the biggest gaps, and using expanding foam for smaller holes. Thoughts on that plan would be appreciated.

Beyond that, I'd sincerely appreciate advice as to what I should do next and prioritise re: walls, ceiling and floor. Funds are very tight, so there will probably be a limit to what I can do, but I'd like to have a plan and a target to work towards over time.

Many thanks in advance.

Best practice for Internal wall insulation

jackmccabe — Tue, 15 Mar 2022 11:48:44 +0000

Hi, we are renovating out Victorian Maisonette set over three floors, it has very thick brick walls of around 400mm and has had some moderate damp issues in the walls (seemingly due to a cement parge coat in places and leaking window ledges)

The plan is to use Kingspan k118 on the solid brick walls with timber battens to achieve a U-value of 0.3.
I am aiming to get the building as airtight as possible so one concern is that the insulated plasterboard won't create a particularly good seal against the very draughty brick work.

I was thinking should I do a parge coat in lime on the brickwork before installing the IWI?
Is that a bade idea as it would reduce ventilation to the air gap behind the insulation?

Also Was planning to continue the insulation down between the joists maintaining the air gap by foaming an insulated board between the joists. Again is this a bad idea due to reducing the ventilation? (We already have put 200mm of rockwool between the joists.

Thanks in advance

Renovations~Best way to internally insulate a solid wall

jamesingram — Sat, 19 Feb 2022 16:43:14 +0000

Thought I'd revisit this basic skill to see what people thought was the current best way to achieve a good long lasting solution to internally insulating a solid wall.
I'll give my preferred methods, feel free to critique it and offer alternatives stating the benefits.
Non vapour open.
Foam boards
On solid brick/block wall with good existing prepared plastered finish and render or brick external finish.
Using lamented plasterboard comb a tight coat of bonding adhesive on to the wall and fit board , foam perimeter.
or
Using insulation board do similar but then fit vertical batons over with fixings through into the wall to create a service void the fix plasterboard to them.

Vapour open option
Wood fibre boards , fixed with lime adhesive , mesh lime plaster top coat

Which type of cavity wall insulation?

rhamdu — Sat, 15 Jan 2022 18:21:58 +0000

We have the choice of bonded bead or mineral fibre insulation for cavity walls.

Later we may want to cut through the walls for doors or windows or a possible extension. I'm thinking the bonded beads are more likely to stay in place when we do this.

What would people recommend?

By the way, additional wall insulation may be added later, internally or externally. But I can't see how this would affect our choice.

Grade II listed barn conversion thermal envelope

Shevek — Tue, 21 Dec 2021 13:22:34 +0000

We're quite excited to be commencing design work on a Grade II listed barn conversion and I'm interested to hear from anybody who has experience with this kind of thing, with a focus on the detailing of the weathertight thermal envelope.

The roof tiles and weatherboard will be lifted, providing opportunity to add a sheathing/sarking, perhaps an insulated sheathing/sarking. The sheathing/sarking racking strength just needs to be sufficient to transfer wind loads as there will be some secondary structure added internally to help support the frame. The roof tiles will be replaced with new tiles but they (and the sarking) will need to follow the existing wobbly roof. The weatherboard will be a mixture of recycled + new. The main focus is preserving and maintaining visual exposure of the timber frame internally. So a small amount of insulation can be added between studwork/rafters, but not full depth.

Are there any standards/guidelines out there for this kind of work?

My initial inclination is to stay away from plastics and sheath the frame in a suitable wood fibre board of some description on the outside, then wood fibre insulation + wet plaster between stud/rafters.

But I did also wonder about EPS. And I did also wonder about a fibre-reinforced plasterboard like Siniat Weather Defence board. This as a vapour resistance of 0.77 MNs/g and would provide a weathertight, fire resistant sheathing with no need for a breather membrane. I haven't checked the figures but I imagine a wood fibre sheathing/sarking + breather membrane would come in about the same figure. Although Weather Defence may not be appropriate for a pitched roof, and a wood fibre sarking might be better able to follow the wobbly roof.

How to apply draught proofing tape

GarethC — Tue, 01 Feb 2022 06:53:08 +0000

Good morning all,

Bit of a trivial one, but hope someone might have some thoughts.

I install a form of secondary glazing I've developed, most commonly in old, single glazed period windows (especially sash and case).

My product doesn't by itself reduce leaks around ill-fitting sashes though. My solution to that is simply to apply some draught-proofing tape. Most commonly I use the translucent kind which has adhesive across half of it's width, and which you attach so that it forms a lip across leaky areas.

It can work surprisingly well, last for a surprisingly long time and you don't generally notice it when it's installed. It's amazing how often I find myself installing it on windows which have already been draught-proofed with brush strips.

I don't charge anything extra for it, because the materials are very cheap, it doesn't take very long and it's not going to last for decades (and I'd feel like I was only doing half a job if I didn't do it frankly).

The only problem is that sometimes it doesn't last long at all. Sometimes this is because we get a duff batch of tape (which I'm pretty sure does NOT have the promised 3M adhesive). At other times the frames can be damp (not uncommon with single glazed windows) or otherwise in poor condition (flaky paint and uneven surfaces).

My usual MO is to give the frames a quick sanding where I'm going to apply the tape. Then I give it a good clean with alcohol spray. If they're damp, I also give the frames a blast with a hairdryer (although often the frames are a bit saturated, so this doesn't seem to work all that well).

I'm just wondering if there's anything else I can do to increase the chances of the tape lasting longer. Perhaps applying a very quick drying primer? Or perhaps a dod of clear silicone at either end of the tape (where it's most likely to come away)?

Greatly appreciate any tips. Thanks!

Sourcing 'proper triple glazed' uPVC windows

Nick Parsons — Mon, 17 Aug 2020 13:57:40 +0100

I am trying to find someone to supply (and fit?) uPVC 3G windows in England.I want a section capable of taking a minimum 48mm unit, not a frame designed for double-glazing into which, with a smaller beading, a 'pinched' 3G unit (of 36mm max, according to one supplier) can be squeezed.

Can anyone point me in the right direction? (Note I would not choose uPVC, but the client does).

Thanks!

Any options for underpinning without cement based concrete

Peter_in_Hungary — Mon, 31 Jan 2022 08:51:33 +0000

Are there any options for underpinning without using cement based concrete?

The wall concerned is a stone wall with earth and rubble infill with a thickness of 60cm. Only one side is accessible. (The outside is a hill!)

Limecrete mixing ratio

tvrulesme — Wed, 19 Jan 2022 11:57:27 +0000

I am in the process of planning to lay a limecrete floor. Getting conflicting information regarding the NHL to Aggregate ratio and what to use for the aggregate. Just wondering if someone could please advise on what they have had success with in the past.

2:1 or 3:1 by volume?
Slabbing Aggregate, Coarse sand, LECA as the aggregate?

Many thanks in advance

Aerogel Internal Wall Insulation

alm — Mon, 17 Jan 2022 15:09:06 +0000

Hi,

I have looked on past discussions, but aerogel hasn't been mentioned for a few years so I was wondering if anyone had more recent experience.

I was pretty set on using aerogel around some bay windows - we have brick piers so need a fairly thin product. However, I just had some advice from a specialist retrofit installer who said he see's a lot of damp issues with aerogel and its not as breathable as you would think - particularly where the boards join. He recommended we use 20mm wood fibre for the piers, and 60-80mm for the rest of the wall. My issues with this is some pretty awkward detailing, and the windows looking a bit strange. And damp issues where the two insulation depths meet.

I've seen past discussions where aerogel has been used and nothing came up on damp. So just wondering if anyone who used it a while ago has seen this, or any other advice around the window. We have a lot of original features (It's an Edwardian semi) and it's important to us to keep as many of them as possible, whilst improving the thermal performance of the house.

For the record the house has 225mm solid walls, external wall insulation is not an option.

Thanks,
Anna

Brush in Floor Brick Grout on Limecrete

Tomasz_P — Sat, 11 Dec 2021 22:43:57 +0000

Hi everyone,

I have almost finished laying my reclaimed cut bricks onto a Limecrete floor with UFH. I used a lime based adhesive. The bricks are close laid and fairly uneven due to the varying thicknesses (and lengths and widths!). Grouting with a wet mix would be very time consuming and I don't think it would work all that well. A brush in grout was recommended to me and I think this method could give me quite a nice sympathetic finish. One slight concern for me was using something not breathable but given that it makes up such a small area and the bricks themselves are porous I thought that would probably be fine as long as I use a suitable sealant at the end. Osmo Poly X oil was recommended to me for this by someone who lays a lot of brick floors in old house. Interesting as that is typically a product for wood.

Cavity between existing house and new timber frame

Christopher — Sun, 09 Jan 2022 18:45:22 +0000

This is my first post to the forum, I am building a lean-to extension on the back of a 1930s mass concrete house and would appreciate any advice or comments on the best way to deal with the 30-50mm cavity between the two buildings. The existing house is approximately 300mm thick mass concrete walls lined with 25mm horizontal battens and vee lining. I intend to strip back to the concrete and add 25mm solid insulation, then plasterboard. The new frame has breathable membrane, osb sheets, 138mm thick timber then plasterboard. Roof is I beams and overlaps the bottom of the existing house roof by 450mm approx. There will be a 50mm cavity and 100mm plastered blockwork all round the new frame. There is insulation below the new concrete slab and uninsulated timber floor in the old house. So what is the best solution for insulation of the frame along that wall? The cavity will be connected to the new cavity wall, so full of cold airâ€¦ plus there is going to be a cold bridge up from the uninsulated ground below. It seems to me that the whole wall will need to be insulated, unless the cavity can be blocked, or filled, but wonder if there is then a condensation risk inside if it is no longer ventilated? Hope I have described the situation clearly, Will try to attach a picture as wellâ€¦

EPS fill under suspended timber floor?

nickbond11 — Sun, 09 Jan 2022 10:22:24 +0000

There seem to have strong opinions for and against doing this on several threads over the years.

I can see the attraction of a quick and easy DIY way of insulating the floor void, but even though some people seem to have been doing this for the last 10 years I am assuming that the issue of removing ventilation and the risk (even if small) of damp issues arising still make this impossible to get building control sign off for?

I am looking to dig down an existing 1.5m basement to give useable head height, which I'm assuming will be specified with a Delta membrane or similar system. Doing this will cut off the front ventilation from the rear of the house, so I assume I for BC I would need to install new cross vents to compensate for this?

Thanks,

Nick

Edwardian House - renovation and extension - advice needed

nickbond11 — Mon, 03 Jan 2022 13:18:32 +0000

Hi, I'm looking for some advice on IWI options and the potential for extension works to cause rising damp issues for a house built in c1902. The walls are typically 9" brick.

The front and the back are on different levels, so that we currently effectively have basement (c 1.5m head height), ground and first at the front and ground, 1st and 2nd floors at the rear. Raised timber floors with air vents at ground level, from what I can see at basement level there is no existing insulation under the floor and just 100mm or so of fibreglass in the loft.

We are in London and the front of the building is south facing, no signs of existing damp. The house in in a conservation area and adjacent to a locally listed building so EWI is unlikely to be an option.

It is in a terrace but has an an access arch through and a rear outrigger, so most of the ground floor also has an external ground floor wall to the side and even the small suspended timber floor over the top of the access arch has 4 large air vents underneath.

We are planning to dig down and underpin the 4m x 4m basement so this has sufficient headroom to be usable and install a delta membrane or similar system and c50% of the rear elevation will also be extended, for which I assume a new concrete slab/dpc and c80mm of insulated PIR would be the usual spec and perhaps a new concrete slab may be suggested for the existing rear ground floor. We may also potentially add a dormer to the loft.

They are not all in great condition, but all the existing windows are double glazed UPVC.

It is also currently split into flats, so we will need to do significant work to the electric/gas supplies and plumbing, so given all the work that we plan to do in any event to extend and covert back to a single dwelling, moving sockets and possibly radiators off the external walls shouldn't be a major issue if this is recommended.

My queries are:

1) how do we mitigate the extension changes to the basement and ground floor leading to rising damp in the existing structure?;

2) would any IWI options be recommended, again bearing in mind the milder weather in London and the south facing front external wall?; and

3) what are the things to consider for chimney breasts and the chimney with regard to insulation/ventilation?

4) should we also be thinking about benchmarking most of the works against a likely need to achieve EPC C in the future when selling the property? I would also add that I expect to want to sell the property in 10 years to move back to the area of London that we live in now with regard to EPC and the cost of IWI vs payback in heating cost savings.

Ideally the IWI would be a basic insulated plasterboard DIY option that I could just mechanically fix, without the added work of needing to add a coat of anything to the rear.

Having had real issues with finding a plasterer that could competently use lime plaster in the past I would much rather use an alternative plaster if possible, accepting that some breathability may be lost.

Sorry for the long post, any advice will be gratefully received!

Nick

Cement corrugated roofing or asbestos

tonya — Tue, 12 Oct 2021 19:53:47 +0100

Is there any way to determine whether corrugated roofing has asbestos content cheaply? I have a roof on an outside building and its leaking and wish to replace it. Fortunately i found a Council refuse point that will take it but before I get into removing it would like to know whether it contains the dreaded asbestos.

4 Panel Victorian Doors - New

Victorianeco — Fri, 10 Dec 2021 17:29:47 +0000

Where can I buy solid 4 panel Victorian doors where the panels are flat with beading around the perimeter?

I cannot find any anywhere new...

Lime plaster storage

kristeva — Sun, 05 Dec 2021 08:24:16 +0000

Hi all

I found someone not too far from me giving away 8 bags of base coat lime plaster for free after recent renovation work. It's bagged and ready mixed by the looks of it, seems a shame to let it go to waste, but I think its been stored in her garden and subsequently exposed to the elements. If this is the case and its suffered a few freeze / thaw cycles is this going to still be usable?

I guess materials get left exposed on site all the time, although so much in winter.

P

Airtightness Barrier - what's best?

tuftythesquirrel — Mon, 20 Sep 2021 12:07:23 +0100

Please could anyone help with the following, re. airtightness barrier. We are carrying out a restoration of a 1950s church hall, rendered cavity, brick and block construction. We have a Kingspan Quadcore composite steel roof, fitted with additional seals. The floor build up is 300mm concrete, 200mm PIR and 70mm Cemfloor screed, painted at the floor junction with Pro Clima Aerosana Visconn to continue the radon barrier under the concrete. The task is to make the walls airtight. There is a 200mm EWI system on the outside of the building. It is twin skin cavity, but having been filled with concrete due to the poor state of the block work. I was going to continue the Pro Clima Aerosana Visconn from the roof panels down to the floor. Iâ€™ve used the airtight paint but it seemed a little frail for our site conditions. e.g. we used it on some of the wall sections, where the joists run parallel to the wall and would be subsequently difficult to access to plaster. But having had a few knocks with bits of flooring etc. the paint has peeled off the wall. There are lots of maybeâ€™sâ€¦. The EWI maybe reasonably airtight at the external render surface. The concrete in the cavity maybe airtight where it is continuous, but it is impossible to know. The cement render on the internal brick/blockwork maybe airtight.
So my question is, would a plaster parge coat be a better bet and if so what plaster? The plaster will lap airtight tapes or paint at the window/door junctions. Please note, this is only to provide the airtight barrier. A decorative board will create a services cavity to run pipes, ducts and cables etc. British Gypsum obviously make a full range but they donâ€™t have any real world figures regarding airtightness. I spoke to their technical support and they recommended their Soundcoat Plus. However, they canâ€™t say that it is 10 times better than their other products, since no one has conducted any tests. The Passive House Guide To Airtightness (my Bible!), suggests 6mm of wet plaster is airtight.
I wanted to use the Thistle Universal OneCoat plaster to get a good build up and reduce the labour costs. Has anyone had a similar situation and achieved good results with this solution. Any comments welcome. Cheers

Refurbishing a detached cavity wall property

Victorianeco — Fri, 19 Nov 2021 22:42:16 +0000

Got an opportunity to purchase what we would call our forever home.... Property needs a complete refurb 50s 60s brick cavity)

We would be going from a mid terrace Victorian house with EWI/IWI, double glazing, lift insulations and running an ASHP

The house we are looking at is detached, bigger and has single glazed windows, cavity walls with no sign of insulation....

As such, my first thoughts are loft insulation, triple glazed windows to front, bead cavity insulation and maybe open up the rear windows being South facing to take into account the solar gain.

We would then choose a heating system based on u-values etc. The floor is concrete and assumed un-insulated. Probably another ASHP or perhaps even direct electric in each room and then invest in solar panels etc.

Any immediate thoughts? We would like to maintain the brick facade so EWI probably out of the question

Extension party wall thermal bridge issue

luz13827 — Sat, 20 Nov 2021 11:25:49 +0000

Hello,

I have just noticed a big cold bridge issue in our extension (see attached pic). We are building onto neighbour's party wall - however they have a flat roof, and we have a pitched roof (already being built as we speak so cannot change the design). The issue is that because we aren't going to the same height as their roof, we are going to have a thermal bridge through the brick wall.

Whether it's right or wrong, I am less worried about heat loss at this stage, and more about the wall being cold and causing condensation and mould.

I think it would be difficult to do EWI on the wall properly because we will have a gutter close to the wall. Would a small amount of IWI help keep the surface of the wall warmer - and if so, would breathable (wood fibre) be best, as opposed to a foil backed insulation?

Soot/ chimney breast removal - health concern & repairing wall

luz13827 — Sun, 07 Nov 2021 00:24:25 +0000

We've removed a chimney breast, which has left black marks, I assume soot.

Have two concerns - health and then getting this wall back to standard.

Would the best approach be to try chisel off the front of the bricks where the soot marks are? A bed will go against this wall, so I'm a bit concerned about the soot being toxic if left.

And then are there recommendations for repairing and levelling this wall - would something like Baumit RK 38 work? Before then boarding over. We are trying to stick to lime and clay plasters as much as possible, but let me know if you think something else would be better.

Flooring above insulation

WeeBeastie — Sun, 31 Oct 2021 05:55:57 +0000

My bungalow's suspended timber floors are to have Rockwool or similar fitted below.

Would I be ill advised to have wooden floorboards as the finished floor in the kitchen and bathroom?

I'm not so concerned about the condition of the wood from regular small splashes and drips, more what happens if a larger splash makes it through to the insulation.

Thanks.

Gypsum V Lime breathability

kebabman — Mon, 17 Sep 2012 11:06:25 +0100

Looking at the column for vapour permeability in a PDF entitled Breathability Matters that I think I downloaded from the natural building website it says that gypsum plaster has a value of 50 and lime plaster 75.
I have some areas of wall that have been plastered with gypsum and I was thinking of removing it but if the vapour permeability is lower for gypsum should I bother and why is lime plaster said to be better?

Many thanks