Wed, 10 Jun 2026 09:15:41 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17899 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17899 Thu, 13 Jul 2023 19:12:20 +0100 GreenApprentice
W’ve now removed the boiler and I’m repairing the botched wall that was glued back together with expanding foam. All the loose fibre insulation in the area has left the building when they knocked the more than foot square hole through to fit the tiny flue.

I’ve bricked up the outside and now wondering how best to insulate the cavity - we are doing EWI, but with what I’ve read, feel we should fill the cavity.

The complication is that the adjacent wall looks to also have lost its insulation above this level. It has a window that will be blocked up at some point in the near future and that will also need the same consideration, so using loose stuff now will probably be pointless.

Also, we have some windows and a door to block up and our wall builder guy has said to use thermalite blocks on the inside of cavity and solid blocks for the outside skin with ‘wall log’ in between. Is this ok or can we better it and could I use this ‘wall log’ or alternative in the boiler hole repair?

Thanks in advance,
Denys]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17901 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17901 Fri, 14 Jul 2023 02:14:20 +0100 alexeix
We’re extending our 1953-ish semi and the majority of the external walls will be new.
The existing walls are 260mm thick and supposedly cavity wall, however, the cavity must be tiny.
We’ll check that when the build commences.

In terms of the finished building, 3/4 of the front of the building will be the original walls, but the rest of the external walls in this be house will be new.

We’re building new cavity walls and all the external walls (new and old), will also have internal wall insulation panels fitted (37mm).
The panels will include a damp proof membrane and will be taped, and we plan to fit an MVHR system, to take care of moisture in the air inside the house.

Our concern is what will happen to the external brickwork during the winter?
If it gets particularly water logged and then we have a spell of subzero temperatures, the brickwork may get damaged.

Is there anything we can do to prevent this or should we not be concerned?

We’re in the south of England.
Thanks in advance!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17908 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17908 Wed, 26 Jul 2023 12:24:34 +0100 Davycrocket
I've finally got round to chipping off the cement render on my 1800s terraced gable end.
When the property was renovated 15 plus years ago the internal chimney breasts were removed which at the time seemed to be a good idea.

I'm now regretting that as now while chipping off I'm following a crack in the render which is revealing some dubious looking stonework and missing stov
ne pieces.


Before I go any further would it be wise to fill in the void with a cement or similar slurry type material to bind this void and outer stonework together ?

Any other ideas would be gratefully received.

Thank you in advance]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17881 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17881 Wed, 28 Jun 2023 16:12:50 +0100 Arf measures I'm trying to decide between insulating between and above the ceiling joists (to give a total of ~300mm mineral wool insulation) and insulating between and below the rafters (giving a total of 150mm foam board insulation).
There is clearly a difference in material costs (£800 for the ceiling joist option including plastic legs to support the new boards vs ~£2,500 for rigid foam insulation boards to the rafters).
However, pretty much everything else seems favour insulating the roof (more usable space, boarding out first will make it easier installing the insulation, don't have to worry about insulating the loft hatch, and ventilation perhaps less critical?).
Are there other considerations I should be aware of? I saw a previous post about roof insulation boards shrinking over time - is that a significant risk?
Many thanks in advance]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17902 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17902 Fri, 14 Jul 2023 15:30:48 +0100 Dur
Some while since I have been here which is an indication of how slow our project is taking.

We have an Edwardian dormer bungalow semi and are soon to be starting on the ground floor by removing the suspended floors and fitting UFH from an ASHP. The floor make up will be sand blinding, DPM, 150mm Jabfloor 70, 50mm PIR then 150mm reinforced concrete slab.

We are thinking on two options for positioning the UFH pipes.
First is to put them onto the PIR using clip rail (which we have) then 70mm chairs to support the reinforcing for the concrete pour. This puts the pipes at the bottom of the 150 slab.
Option 2 is is to put the mesh on the chairs and cable tie the pipe to the mesh.
(Option 1 makes the fitting of the pipes at the correct spacings etc very eay compared with option 2)


I have seen a number of discussions on both methods but they mostly seem to be in houses which are very well insulated. Our situation
is that we are aiming to get the solid walls insulated up to BC renovation standard and very well air sealed (ultimately!). Wall insulation will extend down to the bottom of the floor insulation.
The upstairs has 75mm pir between and 75 under the rafters and well taped and sealed.
So while our insulation will be massively better than it was, it is not "well" insulated by this forum's standards.

My question - will the difference in height of the ufh pipes in the slab have much of an impact in reaction times and could that be a problem? It seems to be a balance between thermal mass which would allow us to run the ASHP at lower temps but for longer for efficiency versus the reaction time if the temperature drops. But does the pipe at the bottom v the pipe in the middle of the slab make much difference?

We do have a wood burning stove for a top up on winter evenings.

Grateful for your thoughts!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17888 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17888 Wed, 05 Jul 2023 16:05:53 +0100 Osprey
However, one roofer asked if I had thought of changing to a warm roof, where no ventilation is needed.I have no plans to put a living space in the loft.

I want to do the roof replacement right: which way should I go?
Thanks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17897 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17897 Wed, 12 Jul 2023 19:34:14 +0100 HookHouseResto
This is my first post but I have been lurking threads ever since we moved into our new old home back in May 2022.

I've done a lot of decorating in the rooms that just needed updating and a bit of loft work on airtightness and insulation so far but I have now started the first major renovation works in our house.

Quick bit of background
A neighbour informs us that the house is of 1902 heritage, so right on the Victorian/Edwardian period border. It's a semi-detached 5br 2bath with a facade typical of the era. Mostly the walls are 2 brick solid but we do have a cavity wall on the side of the rear projection. At some point I'll share a post with the overall long term plans to renovate, including EWI, IWI, MVHR and more.

Before all that I'd like to hear input on my most pressing issue.

I've ripped out our family bathroom of 1980s vintage, unfortunately the internal plaster and lath work was not sound and didn't survive the removal of tiles and plasterboard and the external wall interior plaster suffered a similar fate. With everything stripped back the sins of the external wall have been exposed. There are small holes, cracks and great big gaping chasms in the internal leaf. Whilst I've been removing the debris I've been contemplating the best steps to improve the thermal performance of the room.

This was my original plan for the wall and I think the safest approach

1. Expose as much of the wall as I can - i.e. Remove ceiling and take up floor (done)
2. Repair brick work, removing broken bricks and replacing them with better condition imperial bricks that the previous house owner has stored in our garden. Use lime mortar (fortunately the Traditional Lime Co is a short drive from us)
3. Plumbing first fix - the waste pipe is moving to the corner of the room but apart from that major penetration nothing else should be changing.
4. Airtightness work around penetrations old and new, is foam enough or do I need to employ tapes etc.
5. Parge coat of lime product (just plain lime and sand or a thermally efficient one, please share opinions!) to improve airtightness and provide a level surface for the next steps
6. Airtightness tape applied to joist ends
7. Attach ~80mm wood fibre boards with buttered on lime product and plastic non-bridging fasteners
8. Work on the detail around the window, considering using more synthetic products here, I think that, due to the way the reveals have been constructed, I don't need to use aerogel but I still don't want this being a major thermal bridge.
9. Final plaster finish - now I'm a bit stuck at what to do here, I'm trying to use vapour open products but I also want to tile the bottom half of the wall as this is where the bath is going.
10. Tile
11. Paint upper half of wall - how well do clay paints fare in a bathroom?

Is there any problems with that?

Since its a cavity wall, is this a safer place to use something like a phenolic board (I have a pile of Kooltherm 70mm from over-ordering to insulate my sloping ceilings)? As its a bathroom it is probably a source of moisture input into the walls a lot of the time, so perhaps being vapour open wouldn't be an advantage here?

I've seen in other posts people struggling with posting photos but I shall do my best to follow up with images of the wall and problem areas. I'll also try and share a picture of the layout as the external wall is not actually a significant portion of this room.

Cheers,
Shaun]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868 Mon, 12 Jun 2023 21:02:53 +0100 greenfinger
I've got some repair work to do soon on a single storey roof that abuts a gable end wall. The leadwork was pretty shoddy before and needs replacing with proper lead soakers and flashing. As such, a couple or rows of slates will be coming off.

I've heard it's best to use slate and a halfs where possible, rather than thin width sections of slates. But upon enquiring it seems you don't really get slate and a halves in reclaimed Welsh slates. So that leaves me two options...

1. Forget about slate and a halves, use thinner width slates as needed, and carry on.

2. Use larger format but thicker slates. One rec yard has 30" x 20" slates which could be cut down to almost slate and a half (24" x 20"). The existing slates are 24"x 14". The trouble is that these slates are quite thick compared to the existing. I've never done and am no expert on roofing so am not sure whether the slates being thicker would cause more problems than I'm trying to solve?!

Any thoughts gratefully received!

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17876 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17876 Fri, 23 Jun 2023 18:14:22 +0100 Osprey
Is there any reason NOT to go with the work using the grant (arranged via local council, then intermediate company, then the work being done by a company called Evolve www.evolvehes.co.uk)?

I am thinking quality of work etc]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17885 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17885 Sat, 01 Jul 2023 07:25:41 +0100 Greenlady How should we prepare the floor before getting a professional tiler in ?

Owing to the cost we are having to do all the labouring jobs ourself before getting a professional tiler in to re-tile .]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17883 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17883 Wed, 28 Jun 2023 16:39:27 +0100 ballen
Having sat in a puddle of water for a number of years, the floor was completely rotten, the walls on one side are starting to go - the whole thing has dropped on the left hand side, causing the front wall to bow.

I'd like to try and save it, if possible - my idea was to jack up the wall that's failing, cut a foot or so off from the bottom and build a dwarf wall from engineering brick to sit it back down on. I plan on replacing the floor with a floating floor i.e. glued tongue and grove chipboard over celotex.

We're not entirely sure what we'll be using the space for - perhaps purely a summer house/games room or possibly as a home office. This got me thinking about insulating the structure, such that it might be useable all year round.

Given that its looking a little tired externally, the idea of installing EPS EWI and rendering is appealing, I wondered if anyone had any thoughts on this given the structure. The manufactures suggest things should not be fixed to the walls without allowing for seasonal movement of the 'logs' - I don't know how much this would be reduced by the installation of EWI. I'm also wondering if its a terrible idea as far as fire rating goes.

It seems most manufactures insulated by battening internally (on slotted brackets), filling with mineral wool and adding a VCL before cladding with wood (although I suspect this could be plasterboard if desired) and i suspect this might be a more sensible route.

Either way I would appreciate any thoughts]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17677 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17677 Thu, 22 Dec 2022 16:25:44 +0000 ianh100
We want to make the property as efficient as possible so have a big wish list of technologies we hope to use but struggling to find anyone to help select the best selection on choices we have.

The current property has 2 bedrooms and 1 bathroom. brick construction with foam filled cavities. The loft space has been badly insulated with >300mm of glass on on the floor but also glass inside the tiles (never seen that before). Ventilation has been blocked and I have condensation.

We will be adding a 9m x 7.5m open plan living space and converting the current property to 3 beds and 3 baths. In addition there will be a very large garage, office, laundry room and hallway.

The new build sections have been specified with thermal blocks, 150mm of Kingspan and a 10mm cavity. Only a small amount of the existing walls will remain external so we would like to consider external insulation for these walls.

We would ideally like wet UFH, solar PV, battery storage and possibly ASHP. The current flooring is a suspended wooden floor with around 600mm cavity, below this is a concrete pad which is clean and dry. The new build areas will be beam and block so wet UFH is not an issue but we are not sure what to do in the original footprint. Should we fill the void? Should we insulate between the current joists and fit one of the lower profile UFH solutions?

I can find people who will design the UFH install for me but they don't seem to be able to advise the best construction choices for the floors or how we consider the full building choices for insulation etc. We also plan to include MVHR in all rooms, again we can find MVHR people but can't build a full project view of where best to spend the money.

I appreciate I have asked many different questions, I would really appreciate any input on specific questions but more so on how to take a full project view to get the best balance for the overall design.

Thanks in advance.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17873 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17873 Wed, 21 Jun 2023 10:54:15 +0100 Osprey
I am planning to have the cavities filled (eps beads) of my detached house. This will leave a cold bridge at the wall plate (see attached) and possibly mould at the tom of the bedroom ceilings (I assume). I am also planning to replace the roof.

What is the best way to remove the cold bridge at the wall plate? Ideally, something that the roofers could install.

Thanks for any help!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17834 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17834 Thu, 11 May 2023 12:39:14 +0100 Osprey
I cannot find any company even willing to quote for the work (except for spray foam). Even the company the local authority use for grant-funded insulation work will not do it, and suggest DIY is the way to go.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17798 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17798 Tue, 28 Mar 2023 13:48:35 +0100 Osprey
Would it be worth adding 50mm EPS EWI (ie get a substantial insulation improvement)?

I realise the pebbledash would need smoothing for good EWI attachment. More than 50mm EWI would be difficult for various reason.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17829 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17829 Thu, 04 May 2023 11:10:54 +0100 alm
I'm finally ready to order the boards and get insulating our loft bedrooms. It's a room in the roof on a hip, so I've got three pitches and a central horizontal section. I'm only doing under the rafters as the rafters are only just 50mm. I'll be trying my very best, but inevitably I think I'm going to struggle to make all the different angles meet flush on the insulation boards. I'm sure this is a basic question for a lot of you, but are there any recommendations for filling any gaps between the boards, just to keep the thermal qualities as much as possible. I know foam is an option, I'm not a big fan, but I will use it if its the only way. I was also worried about it expanding to touch the roofing underlay.

Any tips greatly appreciated, I've already got lots of others from reading through the forum but can't find anything on this in particular.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17853 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17853 Fri, 02 Jun 2023 11:21:01 +0100 greenfinger
My house needs some lead work at an abutment. The wall is stone (random rubble), so it's undulating rather than flat. Also, the wall is rather banana shaped. As such, I imagine the slates won't sit tight up to the wall and there will in fact be various size gaps between the slates and the wall, and these gaps will expose parts of the soakers beneath. I hope that all makes sense!

In all I've seen and read, flashing - when with soakers - tends to be just vertical. In my head it would make more sense to have an L shaped flashing given what I tried to describe above. If it was just vertical, it would almost encourage water into the gaps on onto the soakers. I appreciate that's what they are there for. But with an L shaped flashing, the horizontal section would direct water away from the gaps at the intersections, and onto the slates.

Just wondered what people's thoughts are on this please? As it's not commonly done like that, I just wanted to check I'm not overlooking something.

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17570 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17570 Sat, 17 Sep 2022 12:58:53 +0100 michaelf
https://ibb.co/YhVksGX

The room is early 20th century, solid walls (approx. 330mm) and a double layer of slate damp proof course (the concrete slab appears to breach this looking from at heights from the outside. There are two visible air bricks, one above and one below the slates so I assume the concrete was a late addition.

Without wanting to rip up the slab, does anyone have suggestions as the best way to insulate - ideally reusing as many floorboards as possible and replacing the ones that are damaged when lifting but happy for alternative recommendations.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17802 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17802 Thu, 30 Mar 2023 13:48:55 +0100 greenfinger
I’m in the process of insulating my bathroom. I’ve taken the plasterboard down and put PIR between the rafters and joists, with more PIR beneath, perpendicular. We have a cold roof. The bathroom is more skeilings than ceilings. In the rafters, I’ve left a 50mm air gap between the topside of the PIR and the roof felt.

In the corner of the room there is a sewage/stench pipe from floor to ceiling and through the roof. I plan to box this in. I’m a bit confused about how best to tackle the stench pipe from a insulation and ventilation point of view... Presumably it will form a thermal bridge?

- Should I insulate and seal around where the pipe goes through the ceiling and PIR?
- Can I insulate around the pipe from floor to ceiling inside the boxing?

That’s what I had planned to do, but I then got confused as to whether this could cause problems with condensation or anything else on the pipe seeing as part of it is outdoors? The solution doesn’t need to be top notch from an insulation point of view; it’s an old house which will always have compromises. But with the pipe being out of site once boxed in, I want to make sure I get it right and don’t cause any hidden problems.

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17795 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17795 Sun, 26 Mar 2023 07:24:28 +0100 wholaa I was inspired by comments on this forum that toilet cisterns can chill bathrooms unnecessarily. I looked into the topic and found high-end toilets tend to be insulated, for example, Toto Japanese toilets (EPS). So I have been experimenting with this and trying to find the best way. I tried squirty foam, but it is very messy and bulky. It can be trimmed, but water enters many bubbles and may compromise the insulation properties. Anyway, when I did half of a cistern with squirty foam, I could see the side of the toilet cistern with squirty foam was a solid 2-3°C warmer than the non-treated parts. Has anyone else tried other methods? EPS glued on PVA glue?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17814 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17814 Sun, 16 Apr 2023 18:28:34 +0100 davidlithy@gmail.com
I am looking at a retrofit project (theoretical study). The project involves the retrofit of a Wimpey no-fines concrete terrace block.

I will be specifying an EWI to the walls, but I was wondering if anybody could kindly offer some suggestions on what would be the optimal solution in terms of thermal bridging/continuity of insulation concerning the single-storey section/flat roof (as attached indicative photo).]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17815 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17815 Sun, 16 Apr 2023 20:29:36 +0100 Dougmlancs
We’re planning on redecorating most of the house at some point so the disruption of insulating internally doesn’t matter and I could do the work myself but there are some areas like the kitchen and bathrooms which are all on external walls which would be very difficult to do internally. I’m hoping the answers to a few questions might help clarify things.

I understand EWI will only be fully effective on a cavity wall if the cavity is sealed/not full of holes so that there’s no great big cold draughts whistling through the cavity around the mineral wool. Now I assume they sealed the cavity when they did the CWI otherwise the loft would’ve been full of wool but is there a way I can check this? I would imagine there’s no way of telling if there are holes elsewhere though.

How would it work transitioning from your wall to your neighbour’s once you’ve fitted EWI given the differing depth of material? Can you taper it down?
How do you manage the condensation risk- I’m trying to get my head around dew point calculations!

We aren’t planning on replacing the DG in the near future- will that change anything apart from having deeper reveals and extending the sills?
Many thanks in advance]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17807 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17807 Wed, 05 Apr 2023 15:46:41 +0100 Davey P Following on from my window suppliers thread I am a little further along the road of sourcing windows having visited a few supplier/manufacturers.

I am now at the stage of having whittled the choice down to a couple of options:

Option 1 - Alu clad passive spec single sash top hung outward opening window employing Spilka's Opus hinge.
This option looks good. In theory the opus hinge is designed specifically for alu clad windows and is concealed allowing for an un broken aluminium profile. The manufacturers have said the hinge will take the weight of the single sash units (1600 x 1400) of around 70kg's (in my enquiry letter with dimensions I stated I ideally wanted single sash providing the weight was within hardware limitations) they are however a trade supplier and I'm a little concerned if the hinge failed over time it's a case of "tough luck!" I should state that 3 other manufacturers were happy to supply single sash units including a domestic supply and install provider.

Option 2 Same spec window as above but using Spilka's classic hinge and with 2 equal sash's.
This supplier was concerned enough by the sash weight that they wouldn't supply single sash. Also when the classic hinge is employed, the cladding is effectively 4 pieces clipped to the frame and there is an opening in the vertical cladding through which the hinge protrudes. No issue for a timber window but my concern is the ingress of insects and air born contamination which will over time create the potential for decay ie a build up of muck in what is a hidden void.

Unfortunately, we visited option which uses the opus hinge first and had nothing to compare the window too however on visiting other suppliers using the classic hinge, the sash felt much lighter to open and turn.
In reality, I'm not sure if this is really much of an issue as we have managed without having to fully reverse windows to clean them (easy enough from outside) and we will probably only ever crack them for ventilation.
I've contacted spilka to query both design loads (max 80 kg's) and whether this takes into account wind load (if so then our 70 - 75kg sash's should be ok probably not if it doesn't) and whether the opus and classic hinges have different leverage ratio's whether that would account for the difference in perceived weight. They haven't come back to me.

Also, I was under the impression that outward opening doors and windows were a more weather tight option as they get pushed against the seals in harsh weather but further investigation has revealed a number of high end manufacturers using inward opening systems with more seals eg internorm. Internorm are out due to to cost but I wondered if one system had meaningful advantages over the other???

Any input or thoughts on the above would be greatly appreciated as it's frying my little brain!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17732 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17732 Mon, 06 Feb 2023 21:50:42 +0000 number_thirty_three
A bit more info: On one side, they are adjacent to a converted dormer, so are in effect sat on 'internal' walls. The other side has no dormer and they are therefore sat on a section of that party wall which faces the outside air. We will be (under)hanging the loft floor joists from these two beams.

There is also a steel 'goal post' that is propping up the bricks of the chimney above the roofline. It is an absolutely absurd quantity of steel for the purpose, but it is there - and again there are bricks sat directly onto that goal post. That's against the wall, where I had already determined I would need to insulate a bit - so I expect that will mitigate some (most?) of that cold bridge. But perhaps there's some condensation risk I should consider...

For context: Right back at the start of our retrofit journey, before we moved in, we had the chimneys removed, and our SE suggested we install the steels for the loft conversion given that we had to do steels for the chimney removal anyway. I now understand that we could perhaps have avoided steels completely (I met someone subsequently who has used Glulam) or at least used a thermal break material like foamglas.

Be grateful for any suggestions on this.

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16375 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16375 Sun, 29 Dec 2019 14:05:58 +0000 malakoffee
The existing double glazing was fitted in 2002 approx. The closest room is used as a bedroom. the furthest room is a guest bedroom = storage.

Current challenges :-
These bay windows are badly affected by condensation during the winter. Fully closing the blinds and curtains makes it worse.
During the summer I have to keep the blinds and curtains closed to minimise the solar gain. ( Up until around
midday in mid-summer ).
I used to like the open feel of this huge bay window, however since the new neighbours have arrived, with their "more active" lifestyle I would be quite happy to close down the panoramic aspect.

Possible responses :-
- Do nothing : sell up and move on
OR
- Replace the existing window units with triple-glazed units
OR
- Replan the glazed areas and infill the rest with highly insulated walls. ? How to estimate an acceptable amount of light i.e. How big/small the new windows ?

Additional :-
Either side of the bay windows the corners are cold corners. The internal wall surfaces are prone to ( mild ) mould growth.

Any thoughts or guidance would be appreciated.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17739 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17739 Sat, 11 Feb 2023 12:38:16 +0000 Phil & Colette
I find timber sizes very frustrating as 50 x 50 mm square is "nominal" and actually 47x47 or even 45x45 depending on the finish and processing

So..

If a 50mm service void is specified is that a true 50mm or a nominal 50 mm made by using "50mm" battens? Or is something thicker cut down to that size.

Void will be in ceiling with electrics and slimline downlighters.

Thanks

Phil]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17773 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17773 Thu, 09 Mar 2023 13:20:02 +0000 greenfinger
I've got some work to do to a ceiling (and the insulation above), which I might have more specific questions about later. For now, I've been left a bit confused as to when - more generally - a VCL is or isn't needed, and the potential problems with not having one.

Would I be right in saying that the majority of houses don't have a VCL? Victorian terraces, 1950s/60s bungalows. LA and ex-La houses, etc. etc. - do they have VCLs?

If they don't, then I'm guessing that's why it's so important that roof spaces are adequately ventilated. But by that reckoning, if an adequately ventilated roof is capable of dealing with problems from household moisture, and resulting condensation, why when I read info about doing work to ceilings and roofs (including loft conversions) are VCLs almost always recommended?

Taking that premise a step further - if an adequately ventilated loft can deal with household moisture without a VCL, then could adding a VCL be detrimental by trapping more moisture into the habitable parts of the house rather than letting it escape to the roof space where it can be dealt with?

Which brings me nicely onto my last confudlement. We live in an old solid wall house (albeit with more modern extensions), and so have been learning about the need for letting the walls breath by using lime, etc. Is the same not true of ceilings and roofs? Are there merits to having breathable ceilings/insulation/roof space in old houses? If so, what further confuses me is that while I can see the need for different approaches to different types of wall (modern materials with a cavity VS stone walls without a cavity = different approaches needed) are there any major differences between old and new roofs? Putting thatched roofs and the like aside, are old and new both principally the same insomuch as they have a hard roof covering and timber supports?

It's all left me scratching my head, so I wondered if anyone could help explain please?

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17775 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17775 Mon, 13 Mar 2023 21:01:23 +0000 number_thirty_three
In the attached photo (of my own handiwork), what I'm unclear about is:

how to make the insulation continuous between the warm flat roof construction and the vertical rear wall. In my drawing, there's a big gaping cold bridge between the fascia board and the inside.

I can see a couple of options, but is there a 'best practice' for this fairly common problem statement?

All the manufacturer's details show just one plane of detail - the warm flat roof, or a timber frame wall, there is a paucity of details showing the joins!

Options I've come up with:

1) Simple but probably won't work - Add a chunk of PIR at the end of the joists to make it wrap around - and hope that the fascia can be attached to that through to the joist end

2) Kinda complicated - add a modest depth of insulation to the end of the joists (say, 20mm) so that the fascia can be screwed through into the joist ends still; then place 150mm or more inbetween the joists where the joists overhang; then insulate the external side of the wall plate atop the stud wall.

(also, welcome any constructive criticism on any other elements of the detail)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17757 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17757 Sun, 26 Feb 2023 20:36:30 +0000 David Lam Can I pick your brains please.
I'd like to add some IWI to my front wall (victorian terrace with a bay window). It's quite a small area and I plan to have max 60mm insulation. So tiny job really.
It's partially to make the walls plumb as I've now had high quality windows installed.
My main issue is that the wall is highly irregular.
The plan is to frame it out so the wall becomes level and plumb and true with the windows. This will create a small cavity which I would like to fill with insulation.
However if I used batts there will be lots of gaps as the wall above the window sticks out about 50mm more than the below the window.
I thought about boarding it out with OSB and then shoving something like Gutex thermofibre in it.
This is the sort of blown insulation that you're supposed to use a special machine for which would be ridiculous in my situation.
What do you think? Do you think using the blown insulation but just pouring it in would work?

Thank you]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17766 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17766 Sat, 04 Mar 2023 19:04:56 +0000 number_thirty_three
Does it matter if a warm flat roof construction has a second layer of decking above (on the cold side) of the insulation?

Here's my proposed warm flat roof construction:

Outside
EPDM membrane
150mm tissue-faced PIR (glued with Instastik or similar)
VCL
18mm OSB deck
Joists
Inside

-

Question:

The roofer has said that his standard detail is actually to use foil faced PIR and mechanical fixings, with a second layer of OSB on top of the PIR because the tissue faced stuff inevitably gets damaged during install.

I don't really like this idea because:

(a) it's more OSB;
(b) mechanical fixings introduce mini thermal bridges; and
(c) I've read that that second deck is more susceptible to rot because it's on the cold side of the insulation - but have no idea whether there's anything in this...?

What do folk here think?

For clarity, here's his proposed construction:

Outside
EPDM membrane
11mm OSB deck
150mm foil-faced PIR, mechanically fixed through to Joists
VCL
18mm OSB deck
Joists
Inside


Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17692 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17692 Mon, 09 Jan 2023 20:47:09 +0000 ferkan
I have a 1880 victorian terraced house, with brick walls. I'm looking to add some insulation to an inside of the rear wall. Later I hope to insulate the outside. Possibly with cork.

For space reasons I'm only adding about 30mm, but I think it should make a meaningful difference to the brick only wall? I''m also doing it so as the wall needs redecorating and has damaged plasterwork.

My plan is to use about 25mm of expanded cork tile affixed to the existing plaster with isovit e-cork.
I want to cover that with a decorative cork layer. Something like this: https://puretreecork.com/product/36033

My questions are:
-Anything about this a bad idea.
-Does anyone know if any decorative cork layer is breathable? I've not been able to find much about how the decorative layers are made.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17754 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17754 Fri, 24 Feb 2023 17:29:53 +0000 number_thirty_three
Is there anything useful that can be done with them - by which I'm thinking put them into some kind of breathable bag and use as insulation somewhere - or is it the case that in their raw dust form, not compacted, they're not likely to be very useful as insulators?

I imagine I'll be able to use some of the bigger offcuts in some places, just pains me a bit to throw so many of the smaller peices away as they are pretty pricey!

Sheepswool definitely generates a lot less waste from cutting to fit! Couldn't believe how much woodfibre dust the festool generated (and got clogged up with!)

Thanks for your thoughts]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17748 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17748 Mon, 20 Feb 2023 20:09:15 +0000 philedge
Question is how to insulate. The interior has been decorated in the last year or so and with a second baby on the way they really dont want any/much disruption inside. There's enough eaves overhang to get a bit of EWI fitted so thoughts are to work from the outside, remove the external cladding, fit 50/75mm of PIR between the studs and a further 75 over the outside of the studs. Vertical battens fixed through the PIR into the studs with timber cladding fixed to the batten.

With no VCL are we going to hit problems even though weve got an equivalent or more insulation on the outside than within the studs? Second question is, if we can use foil faced insulation, do we need a membrane over the outside of the insulation?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17758 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17758 Mon, 27 Feb 2023 18:46:47 +0000 evan I used to post on here many years ago, got some great advice and nice to see a few familiar names still here.

Since I last did any renovation wood fibre has become affordable, so I would be interested to use it, and/or some kind of wool to add insulation to my current house: old, barn type Scottish rubble wall type construction, which has a suspended wooden floor and lath and plaster walls with a gap between the wall and the back of the dry lining.

What is a recommended recipe in this case for walls? I imagine new stud walls with insulation between / on top of the studs, but not sure where any membranes or barriers should go, and can the rigid board be plastered or is plasterboard on top still advised?

Likewise for the floor, to which I would also like to add UFH.

Only current insulation is in the loft, 150mm rock wool.

Any suggestions or examples appreciated!

Thanks
Evan]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17727 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17727 Tue, 31 Jan 2023 20:09:24 +0000 Davey P I was thinking Aluclad from a longevity perspective but not encountered them before. Are they worth looking at or a waste of money.
Also, the really thin frame detail on some of the more contemporary units I've seen would look out of place on our rustic 400 year old pile of stone. I'm wanting to go for a single opening unit ideally to maximise both light and efficiency but the frames will need to be reasonably chunky.

Can anyone recommend any suppliers as I literally don't know anyone with triple glazing apart from locally sourced plastic. I've spoke to Russel Timbertech but not used them before. I've heard of Internorm but thats just from a google search. This will be our last home so want whatever I install to last so I don't have to replace them again.

Any info much appreciated.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17734 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17734 Tue, 07 Feb 2023 10:20:58 +0000 lngn2
Context:

New concrete slabs with DPM underneath.
PIR on top
Slip membrane/VCL
Anhydrite Screed.

I understand that the DPM should be joined to the DPC in the wall (but can't as the builders didn't leave enough membrane free and I wasn't aware at the time). Seems I can mitigate with a paint-on DPM such as BlackJack or Synthaprufe).

How does one deal with the floor VCL though? Should that also be joined to the wall? I'm tempted to trim it back to floor level and then use blower-proof paint over the junction? Alternatively I could use some sort of tape - Contega Solido?

As an aside, does anyone know how long a concrete floor should be left before covering with PIR? Our builder said it would be OK after a few days (which is what we did) but subsequent digging suggests otherwise and I've had to pull him up on a number of technical points he got wrong and I suspect this may be one?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17698 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17698 Mon, 16 Jan 2023 12:34:01 +0000 lngn2
Question - has anyone else had a similar issue and how did you resolve it? Options as I see it are:
1. Remove the boards and make up. Not going to happen as we can't afford to waste the materials, don't have the time etc.
2. Live with wonky walls and make up as best we can around verticals (the doors etc).
3. Use the top-coat plaster to make up - but will the boards cope with the required thickness of plaster hanging off them? Could be an inch or more in some places. The supplier isn't sure, so anecdotal evidence would be much appreciated!

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17729 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17729 Wed, 01 Feb 2023 23:53:59 +0000 number_thirty_three
We have plans to include two fairly small openable rooflights - looking at Velux or Fakro - in our loft conversion. Have scoured for guidance on how to minimise the bridging around the frames but it seems little has moved on since this post from over a decade ago, and the manufacturers still offer fairly limited solutions in this space:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4112&page=1" >

Some specific questions:

1) One of the interesting ideas I've seen mentioned in a few previous posts is about constructing some kind of mini-SIP to house the Velux frame in. Has anyone got any pictures or links to anything detailing how this has been done successfully?

2) I'm planning on putting 80mm PIR above the rafters; can't find guidance on how to install Velux or Fakro in such a circumstance - presumably they have to be installed onto timber, not to PIR - so would we need to construct a raised timber frame above the rafters in line with the insulation, to secure the frame into? If so, then I guess that's introducing more thermal bridging - any ways to mitigate this? I've seen mention of wrapping Aerogel up the insides. Worth it?

2) Should we rethink having openable rooflights? The loft design has one rooflight in the bathroom, one in the bedroom, and then a large openable window on the dormer side. We're due to have MVHR. Do we need to be able to open the skylights, or should we consider being more radical and having them fixed to improve the overall thermal performance?). Feel like we will want cross-ventilation on warm summer nights... Obviously this is a personal choice kinda question but I'm curious what the folks on this forum would do.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17724 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17724 Tue, 31 Jan 2023 12:36:36 +0000 alexeix
I live in a 1950s semi, which I am going to be extending (awaiting a decision on planning).
Most of the original, external walls will be subject to the extension and therefore the new external walls will be properly insulated, however, most of the front of the house and one part of the rear upstairs will remain original.
Bizarrely, the house has almost no cavity, so I’m looking at internal or external insulation panels for the relevant areas.

The house is quite humid, which has caused some mould growth, so I’m now ventilating twice a day by opening all windows for about 10 mins and running a dehumidifier when the windows are closed.

Therefore, I’m going to need to fit some kind of automated ventilation.
I considered an MVHR system, but it would require substantial changes inside the property, including boxing in of pipework, so it’s not suitable.
We also know peoples who have recently fitted a PIV system and they said the incoming air is cold, so we want to avoid that.

We seem to be left with adding individual heat recovery ventilation units in rooms (probably not all), but I’d like to get some feedback from people who are using them.

Does anyone here have these things and are they any good?
How much noise do they make?
Recommended brands?

Thanks!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17722 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17722 Sun, 29 Jan 2023 23:30:37 +0000 number_thirty_three
1. Would anyone care to critique the detail in the pic attached? I'd be grateful for any constructive criticism of my draft - I've assembled this based on research on this forum and elsewhere but before going ahead with the build phase I'd love to get a sanity check that it's not terrible / is there anything we could be doing better etc - thank you in advance :)

2. Foam? I have seen mention of some squirty foam being used when PIR isn't tightly fitting - what is this foam, should I be using it (instead of stuffing in something like wool) and what is its u-value? (The only one I've been able to find on a google is a Soudal one from Screwfix, but they give a u value of 35, which I'm perhaps mis-reading, as it would seem to be inaccurate by a factor of 100...)

3. Mechanical fixings Anyone have any specific product suggestions for mechanically fixing PIR above the rafters? On here I've seen mention of some hammer-in fixings for example but not seen any specific product name or link to follow. Would need something around 115mm in length (going through 80mm PIR). And related to this - do people typically secure the Counter Battens (by which I mean the battens that run in line with the Rafters over the external insulation) separately after installing the PIR, or is it a case of securing the PIR with a minimal amount of screws, and then installing the Counter Battens through the PIR to the Rafters?

I assume that they don't *need* to be thermally broken - partially I say this because our rafters are only 50mm wide, so any thermally broken fixings (ie. plastic covered) will be a tad difficult to use, but also it's the insulation external to the rafters, so hoping the thermal bridge it creates is less significant...

4. VCL? Am I right in thinking that our Airtightness membrane we'll be placing on the inside of the PIR is also - in the context of this pitched warm roof - our Vapour Check/Control Layer (VCL)? (So long as it's taped at joins).

Thanks in advance :smile:

PS. re my proposed detail, I am unclear on whether I need the insulation to extend all the way to the ends of the rafters, as it's a good 30cm or so beyond the edge of the IWI (Woodfibre) coming up from the floor below - the main reason I have continued it down is that it looks to reduce the thermal bridge at the join...]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17711 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17711 Mon, 23 Jan 2023 19:02:27 +0000 Osprey
I was wondering if I could simply make a hole (in each stud partition) and pour in EPS beads. Then fill the holes, job done? I would prefer to use the grey, cavity wall beads, but they seem almost unobtainable, so could I use white beads?

The outside of the bay wall is rendered (pebble dash, good condition) and the inside is very good condition plaster/paint.

Any thoughts on whether this would be a good or really bad idea welcomed!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17709 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17709 Sun, 22 Jan 2023 20:07:22 +0000 number_thirty_three
I'm looking at the insulation options for our upcoming loft conversion and have hit a wall (metaphorically speaking).

Its a typical mid-terrace 1905 period house. The pitched roof has a little gable triangle on the front - I've attached a diagram to illustrate it. The diagram also shows the parapet atop the fire walls breaking the roof line between our roof and the neighbours either side.

Because of those parapet walls, I believe we can raise our roof height on the front elevation a little as it won't be massively noticeable from street level, enabling us to convert it to a warm roof (by which I mean adding around 100mm of PIR above rafters, and filling the 100mm rafters with a further 100mm).

However, I'm unclear what to do about the the little triangular gable. If we added 100mm there, it would make the triangle wider/bigger overall, and that wouldn't be acceptable to do. The only way around it would be to remove the rafters there completely, shrink them down and rebuild, which seems like an awful lot of rework (all the existing roof rafters are in good condition so can remain in place).

I'm keen to go down the warm roof route but this has me blocked. Has anyone seen something like this before / any suggestions?

So far I've considered the following:

a) Adding only a small amount of insulation above the rafters in that section - 20mm say - which would hopefully then not distort the appearance of the triangle. I imagine a downside is a potential thermal bridge where those sections meet the 100mm areas, with inconsistent u-values around the fabric of the front elevation, which I imagine could leave to condensation issues / risk of rot etc.

b) Doing a warm roof on the main pitch, as well as the little gable triangle vertical face, but a 'cold' roof on the pitched roofs of the little gable. There will be intersecting points between the two which would add complication to the detailing even more I imagine.

c) abandoning warm roof aspirations and insulating it as-is (i.e. as a cold roof). This affects head height though, so I'd like to avoid if I can.


Thanks in advance for any suggestions]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17702 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17702 Wed, 18 Jan 2023 11:20:25 +0000 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17700 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17700 Tue, 17 Jan 2023 07:45:29 +0000 WeeBeastie
If this is not best practice can anyone point me to a drawing showing how it could be improved to minimise cold bridging? Will the new windows be exactly the same sizes as the old ones? I can't find a builder working in my area who has any experience of EWI so am worried about getting this right. Have read a couple of threads here but being a layperson don't fully understand the text descriptions so a drawing would help.

Second issue is how to insulate the lead roof of a bay window. Architect suggests doing this internally so the ventilation is not interfered with - if this is the case then presumably the new window would be lowered at the top to accommodate?

If I lose window size in any of this it's not an issue as they are very generous.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17634 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17634 Tue, 08 Nov 2022 12:53:47 +0000 Dominic Cooney I suppose at least there was something, there was nothing in the stud walls that partitioned off the eaves storage space. Also nothing to stop the external air from the eaves blowing all the way across the room, under the floor boards, between the floor joists to the other side. Lets just say it is well ventilated!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17681 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17681 Tue, 27 Dec 2022 12:42:06 +0000 alm
Sorry, this is a bit of a lazy question on my part. I'm getting ready to insulate our roof, at rafter level. The rafters are very thin, so the plan was to just fix 150mm celotex under them, taped and sealed, battens and then plasterboard.

I've also seen some comments on using EPS instead, and how this might be a better material. Would anyone recommend one over the other for this detail?

The EPS appears significantly cheaper, I know the U-Value will be slightly less which I'm happy to accept, are there any other disadvantages?

Cheers]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17676 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17676 Thu, 22 Dec 2022 12:32:48 +0000 Osprey
The kitchen internal dimensions are 4.7m x 4.7m. From what I can see through a downlight hole, the joists are around 240mm high, and are about 320mm face-to-face: I cannot see their width.

Can anyone with experience of houses of around this vintage estimate what the joist thickness is likely to be? (Don't worry, I will get a proper structural engineer in before having anything done!)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17670 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17670 Sun, 18 Dec 2022 11:14:10 +0000 Osprey
My 1920s house has three brick chimneys. All on outside walls, all 'stick out' (so inside walls are flat) if you see what I mean.

Chimney 1: Unused. Taken down to loft floor level (under eaves). Two flues, one bricked up with vent to bedroom, one with no vent bricked up in dining room.

Chimney 2: Stack remains. One flue used, in lounge. One flue unused, bricked up with vent in bedroom.

Chimney 3: Unused. Taken down to loft floor level, as above. Masonary is half height, only to first floor. One flue, bricked up with vent in bedroom.

Complete removal would be expensive, and I am aware there would be cold bridging if they remain. iwi is not really an option. So given those restrictions, what would be best way to reduce heat loss (and prevent damp)?

Thanks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17672 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17672 Mon, 19 Dec 2022 20:33:24 +0000 Osprey
Part of the property has solid floors, and I beleive they are sealed from the wall cavity, and have a tunnel to the rest of the house (suspended wooden floor). A couple more are sealed from the wall cavity, and directly access the sub-floor void. However, approx 6 air bricks are unsealed and also vent the wall cavity. The 1920s house is rendered, with a cement plinth. 50mm cavity, brick walls.

It would be very difficult to remove the airbricks from the outside, and also risk loosening the render. If I can get access from inside, via the underfloor void, would it be possible to add sleeves to the existing air bricks, sealing with eg expanding foam? Or any other suggestions.

Thanks!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17668 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17668 Thu, 15 Dec 2022 09:57:34 +0000 Osprey
In the loft, I can see that the cavity walls are uncapped - indeed I can see no other means of loft ventilation - and the loft itself is dry. There is a good amount of loft insulation between/over the joists. There are quite a few airbricks around the property, below dpc. These connect to the space below the suspended wooden floors. I believe they also ventilate the cavity walls (no tunnel) so cold air can freely circulate through the walls and loft, with high heat loss. Obviously I want to reduce the heat loss.

1) would capping the cavity in the loft make much difference? I would need to provide other loft ventilation. I would much prefer not to use soffit vents - are other methods possible (old, tile hung with bitumen paper lining)
2)if I go for bead cwi, what happens below the floor? A fibre insulation installer said they would need to drill and install some sort of shields, at an angle, over the airbricks.
3) what happens at the bottom of the CWI? Does it go below the DPC and just lay on the ground between the walls? Doesn't that bridge the DPC?

Thanks for any help/advise!]]>