Mon, 25 May 2026 04:05:32 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18341 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18341 Mon, 01 Sep 2025 15:58:30 +0100 BWork
Greenbuilding.co.uk, owned by the AECB, promotes excellence in design and construction. This website, including the very popular Green Building Forum, was set up by Keith Hall, who co-founded the AECB back in 1989. Keith kindly donated the site to the AECB on his retirement in 2025.

The Greenbuilding site is for everyone from industry professionals including architects, builders, developers to green enthusiasts and homeowners looking for information and a place to discuss all aspects of sustainable building.

With the money that we hope to raise from this Crowdfunder we will be able to update the original website and forum, currently working using older technology that does not allow for necessary changes to the platform. With your support of a much-needed funding boost we will be able to invest in new technology that will bring the site into the 2020s. This will make it easier for visitors to navigate around the site and read the valuable information and resources we share, for those on their sustainable building journey. Users will also be able to sign up quicker and get involved in the conversations.

https://www.crowdfunder.co.uk/p/qr/dyR52gZn?utm_campaign=sharemodal&utm_medium=referral&utm_source=shortlink]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=289 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=289 Tue, 15 May 2007 18:00:44 +0100 GBP-Keith https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18428 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18428 Tue, 05 May 2026 18:28:24 +0100 Rex
While cleaning today, I found in the dark recess of a cupboard that is effectively, our plant room (HW cylinder and boiler cupboard) a pile of soft stuff; no idea what it is but vacuumed it. Thought it may have been coming from some insulation around the top of the wall hanging boiler.

Checked again just now, and at the back of the cupboard on the floor, I see ants. They appear to be coming from a very small hole where the Fermacell and screed meet.

I don't like eradicating insects but I also don't want ants nesting in the timber frame / Warmcell. Google tells me how to prevent them coming into the house but what is the best way to eradicate them from where I cannot see?

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18435 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18435 Wed, 13 May 2026 08:29:03 +0100 ChrisGT Cavity walls with 80mm glass wool batts, clod roof, dot and dab plasterboard walls and a terrible airtightness test
Planning to:

Fill cavities below dpc with ecobead.
Create warm roof by increasing rafter depth with intello membrane on inside and blown in gutex or warmcel and solitex plus counterbattens and battens above.

150mm eps from 300mm above ground to foundation fixed to exterior brick walls. Timber frame made from 2 x 50x50mm timber with noggins to create 150mm cavity to be filled with gutex and 40mm rendered woodfibre board outside. Intello against bricks connecting to foundation and roof vapour control layer.

Does this sound like a good plan. Have considered parge coat in wall or passivpurple but intello seems cheaper and more eco.

Triple glazed windows hung outside current wall in picture frame.

Any suggestions or thoughts on improvements?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18429 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18429 Tue, 05 May 2026 20:28:22 +0100 Victorianeco
Specifically, I would like to compare:

1. Cavity Fill Only: Filling the cavity with 80mm expanded polystyrene (EPS) graphite beads while keeping new windows (3G) within the traditional layer.
2. Cavity Fill plus External Wall Insulation (EWI): Performing the above and adding a 120mm EPS board external layer.

While the latter is more thermally efficient, it is also more labour and material intensive. I need to evaluate the payback period based on current material costs and research.

Furthermore, I have concerns regarding the impact of the 120mm EWI on the property's interior. Extending the wall thickness may reduce natural light and affect viewing angles from within the room, particularly at the 30 to 45-degree angles we currently enjoy. There is also the potential loss of the window frame's aesthetic "framing" effect to consider.

What are your current thoughts on these two approaches based on up-to-date material costs and thermal performance research? Please let me know if there are any other factors I should consider at this stage.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18432 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18432 Mon, 11 May 2026 21:04:47 +0100 chrisinbrighton It appears to last way longer than sealed units and a lot better performance.
My only concerns are how visual the small spacer dots are and the width of the packer.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18424 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18424 Fri, 17 Apr 2026 19:53:40 +0100 chrisinbrighton My own experience of aluminium on bikes is that it can go brittle with age.

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18433 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18433 Tue, 12 May 2026 08:21:32 +0100 thebeacon
While digging in the front garden recently I found a capped old concrete/clay pipe that leads back to the main soil drain.

My question, was this once a soil vent pipe? And if it was should I reinstate it? We had to lower the garden in front of the house, so now it sticks out the ground. I either want to cut the pipe to lower it and recap it or fit a soil vent pipe if it’s required. Other houses in the area have what appears to be a vent in their front gardens.

Cheers,]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18427 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18427 Mon, 04 May 2026 19:31:46 +0100 Rex
Neighbour has gone on holiday and asked me to keep an eye on their house, including giving some liquid refreshment to some plants.

Looking up from the rear garden yesterday, this is what I see. Went to check from the balcony and the glazing is presumably, toughened glass but also laminated. It is only the inner pane that has fractured. Wheat could possible be the cause?

Toodle pip]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18425 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18425 Sun, 19 Apr 2026 23:00:46 +0100 ChrisGT https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18421 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18421 Sat, 11 Apr 2026 11:40:30 +0100 minisaurus
Has anyone experience of them? The positives are many, but what are the negatives? price I guess]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18423 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18423 Wed, 15 Apr 2026 10:35:53 +0100 andyman99
Whilst starting to help my son renovate his bathroom we came across a rather unpleasant problem. The tiles on an external wall pretty much fell off and everything behind is very wet.
Construction: this “front” wall appears to be a simple timber frame structure. From outside to in: PVC cladding - roofing felt (what I would call old style felt not a breathable membrane) - timber frame filled with fibreglass type insulation - plasterboard. The water ingress does appear to have come from the inside. The timber structure is very wet, the insulation a sodden mess and the roofing felt disintegrates as you touch it. We have an insurance assessment this Friday but I would like to understand a way forward if possible before then. I think the main structural walls are brick, left and right whilst front and back appear to be this timber frame structure. 2 rooms across the front, bathroom and bedroom. No obvious signs of a problem in the bedroom front wall. I’m wondering how fixing this would best be approached? Any ideas welcomed]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18361 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18361 Tue, 07 Oct 2025 12:20:39 +0100 Nick Parsons
I'm just raising this in a new thread since I am not sure where it goes from here. I have a 'soft spot' for GBF, and was 'in' long enough ago not to have paid anything, but if we assume (I don't *know*) that the number of active users ('supporters') is relatively small I am not at all sure how the £6500 will be raised. I'd be sad to see it go, but maybe that has to be??

Just some random ramblings, but any other thoughts would be useful to users and, I am sure to AECB as new 'Guardians of GBF'.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18414 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18414 Thu, 12 Mar 2026 08:19:49 +0000 fostertom https://www.greenregister.org.uk/civicrm/?civiwp=CiviCRM&q=civicrm%2Fmailing%2Fview&reset=1&id=5840&cid=40824&cs=f4a98d878cf7eb7a71342f57279ea33e_1773283838_720

"... research into stone structures to help move their use back into everyday construction.

Standing three storeys tall, the Stone Demonstrator shows stone’s potential as a contemporary, low-carbon, structural material.

Natural stone offers a route to cut carbon emissions sharply. Compared with a conventional reinforced concrete frame, the Stone Demonstrator drops embodied carbon by roughly 70%, and by around 90% when set against steel.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18419 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18419 Fri, 10 Apr 2026 07:20:37 +0100 Victorianeco
Any suggestions on materials that give a good corporate image but also boast good green credentials.

They must all be standardised and suitable for standing desks

TIA]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17796 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17796 Sun, 26 Mar 2023 23:01:59 +0100 zak99
We need to replace our broken concrete driveway and also provide a separate hardstanding for parking/working on a vehicle etc

Other than the usual concrete, block paving, slabs, gravel are there any other lowish impact surfaces I may not be aware of please?

Permaculture garden designer suggested gravel and sleepers for the drive or gravel with random planting in the gravel but she is hard to nail down on the details. Like will a wheelie bin or wheel barrow pull through the gravel or how do I do low nutrient random planting with type 1 sub base or will the sleepers be slippery in winter. My wife would like to break up the gravel expanse with some sparse slabs but designer feels gravel will always end up on top of slabs.

For the hard standing beside the garage I may possibly be able to reuse some old slabs but wondered if there are other lowish impact materials for a new surface?

Whats your experience please?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17406 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17406 Sat, 05 Mar 2022 20:47:49 +0000 chrisinbrighton
The walls are all 700mm thick stone and one of these walls is covered in slate with a 50mm gap. I was thinking this would be a good place to add insulation.Is there a particular type which would be best and does a vertical slate wall need a breathable membrane?
Thanks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18415 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18415 Mon, 16 Mar 2026 11:29:31 +0000 ChrisinYorkshire
Hopefully this makes sense – if its hard to follow let me know and I’ll look at posting a diagram.

I would like any thoughts about my planned action for insulating a wall where my house transitions from being underground to above ground.

Context
The house is built against a valley side. It is mostly of traditional thick sandstone construction, although 30-40 years ago or so some areas were rebuilt with cavity walls.

To one side of the house two floors are effectively underground – the top floor pokes above ground approximately at floor level. The wall against the earth has been fitted with a cavity drainage system, metal studs, with PIR insulation and careful attention to airtightness/VCL.

My current area of concern – the transition point of said wall, as it pokes out from the ground. This involves 3 large wooden beams that are bedded into the wall (upon which sit the top floor floor-joists). I am switching to breathable insulation for the top floor room (a kitchen).


Further context and observations

It has been a very wet winter, the kitchen is unheated and has no mechanical ventilation. Where one of the beams enters the wall I am getting a 23% moisture reading ( this is the top face of the beam)

Floorboards have been cut away (approx. 70-80mm) from the wall during summer last year. They are reading 20% moisture at the edge closest to the wall, this is in the coldest corner of the room.

A floor joist running along side the wall, but separated with DPM and a gap, is reading 21% moisture.

Therefore I think there is a general humidity/condensation issue, though the beams bedded into the wall might also be wicking some moisture from the wall.
The coldest corner of the room, is a bit damp, also from condensation I believe. Note this corner is going to be behind kitchen cabinets.



Current course of action:
- I have dubbed out and parged the wall with NHL 3.5 and sand mix.
- Planning to meet the PIR insulation with wood fibre board which will then continue up the wall.
- I have considered but don’t want to use an eps/xps plinth layer at the transition from PIR to wood fibre boards, because I don’t want to trap condensation/moisture around the large beams that enter the wall.
- There is a leaky gutter externally that will be repaired/replaced.
- Kitchen will have mechanical ventilation and heating installed.

Any concerns over ‘wet process’ vs ‘dry process’ wood fibre boards? Wet process appear to be more capillary active than dry process boards. Frustratingly it's hard to find suppliers of wet process boards in tongue and groove.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18416 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18416 Tue, 24 Mar 2026 11:40:09 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18379 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18379 Thu, 04 Dec 2025 16:25:55 +0000 revor https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18413 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18413 Mon, 09 Mar 2026 20:04:02 +0000 Gareth J
I didn't ask him, but what's the advantage over a non breathable setup? Something like DPM, concrete slab, PIR/EPS, top layer/s. His place is all above ground and is a well built house.

I can see that there are likely lower carbon and non plastic based advantages but from a performance perspective, does the floor need to breath? Is it mitigating potential moisture issues? This might have been covered loads or be completely obvious and I've missed it so apologies in advance!

The suspensoended floor in my own solid wall cottage needs attention at some point in the future so am keeping half an eye on options. It's complicated by being half dug into the ground around it though.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18408 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18408 Sun, 22 Feb 2026 19:05:31 +0000 Victorianeco
Considering roofing options to replace 70 year old concrete tiles.

Solar makes perfect sense at this point and so does a standing seam roof.

This could be a good all in one system?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18410 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18410 Sun, 01 Mar 2026 10:27:23 +0000 Rex
We own a maisonette that is rented out. An old Potterton Kingfisher cast iron boiler, bullet proof, always passes the annual test but by today's standards, very inefficient, provides the DHW and heating.

The gas guy always recommends replacing with an electric boiler. My wife sees the Fischer Future Heating (https://fischerfutureheat.com/product/electric-boiler/) ads in the weekend papers and is keen for me to investigate (advertising pays!)

I don't know one end of a replacement electric boiler for the other; the Trustpilot reviews are all great, but they are mostly based upon installation in the past few months, not long term usage. Are these boilers any good? Apart from boosting the EPC rating and a small saving on the annual test, are they worth the installation expense?

Thanks and toodle pip]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18391 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18391 Tue, 06 Jan 2026 12:45:55 +0000 fostertom Thickness - 15, 12, or will 10 ply be adequate?
Material - WBP ply? - any concerns about poss long-term intersitial condensation, positioned as they are well outboard in the insulation/sandwich? Is fibre-cement or other mineral board used instead? I guess interstitial condensation is no more likely than on/in the the window frame itself, but with less drying potential?
Assuming air-sealing to the wall, and to the window frame, are do-able, what about air-sealing the four corner-edges of the box?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18407 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18407 Sat, 21 Feb 2026 21:37:47 +0000 Victorianeco
While I can appreciate it's quicker and lighter we feel we would possibly like vertical cladding.

I guess that would mean we'd need vertical battens followed by horizontal followed by the cladding...

What are the pros and cons of each? And are there any simpler methods of fixing vertical boards while ensuring drainage?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18406 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18406 Tue, 17 Feb 2026 17:03:54 +0000 Rex
My slab is reinforced poured concrete sitting an industrial corrugated galvanized metal base with an air gap below.

When I park the car following a wet drive, inevitably, water drips onto the concrete and there is frequently a puddle in the morning. It is probably not of concern to me, but it does cross my mind that reinforced concrete with water sitting on top can in time, cause the rebar to rust with the obvious consequences.

Is this something I should be concerned about? Alternatively is there anything I can apply / paint on the surface to reduce the absorption of water?

the mats at the front are to 'contain' water from the front arches, but the large damp patch is from water that I guess is dripping for the various under-body panels.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18398 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18398 Fri, 23 Jan 2026 07:59:39 +0000 Rex
Kinda trivial as it does not concern me but just out of interest!

Have a new neighbour in a 1930's house and they are having the place re-wired. Obviously, it mean removing all the wiring that is covered with plaster.

Which gets me thinking, how would a future owner of my t/f house with Warmcel insulation, do the rewiring?
Not easy as they would have to cut slots out of Fermacel. I also have the ceiling fully insulated with Warmcel.

How is it done?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18402 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18402 Thu, 05 Feb 2026 17:59:25 +0000 davidj
Just a query about insulation. We are trying to retrofit a 1976 bungalow. Cavity wall with loft. We are going to insulate the cavity and externally and clad in timber. We are intending to remove part of the loft./ceiling to create an open plan kitchen/living room. We are raising the ceiling over the kitchen just to give some visual interest to the room. The roof above the kitchen is an east facing pitch roof with a bitumen felt beneath Burlington slates. We will install some roof lights, taking the ceiling up to the rafters.

The bungalow roof has had three large purlins installed, each 350 mm deep, 5600mm long. These were installed because of a failed trussed purlin before we moved into the house. The new purlins are vertically installed and variably at approximately 900-1000 mm apart measured along the rafter slope. The purlins consist of two pieces of timber glued and bolted together and appeared to be doing their job satisfactory, although I don't know why they needed so many given the small spans between the rafters.

We are hoping to put as much insulation in as possible. We are intending to insulate under the rafters to allow ventilation to the full depth of rafters, which are 100 mm deep. We were then going to insulate between the purlins. Sorry, can't seem to attach a drawing.

The question I have is what type of insulation to use. One of the cheapest and possibly easiest is to use PIR. After angle cutting the PIR to ensure the sheets would fit accurately between the vertical purlins I would add Gapotape to ensure a snug fit, though would probably needing some support at the lower end where the angle wilth the purlin is obtuse. We were intending to install 260 mm of PIR in whole 2.4m boards, staggering the joints between layers. We would then tape the edges to the purlins and between each board to form a continuous VCL and achieve air tightness.

However, we have been spooked by the potential condensation issues and whether we should go for a more breathable/vapour permeable solution. Given this is above a kitchen generating lots of moisture, we are wondering which way to go. We are intending in any case to install a ventilation system, hopefully an MVHR, to manage the moisture levels in the house. The purlins are not fixed via brackets to the gable so at least no embedded timber to worry about and the cavity and exterior would be insulated.

The other options is to use flexible wood fibre or Thermafleece batts. These cost quite a bit more as we needs 280-300 mm, and don't achieve quite the same level of thermal performance (albeit I am not convinced about the claimed performance of PIR). But they are at least vapour permeable and more sustainable products. Mineral wool batts are another option but it is actually quite expensive at the moment and because of the spacing between the purlins (900-1000mm), it would involve lots of cutting, bearing in mind this material is horrible for lungs and skin.

The other problem with batts is that they are quite tricky to install as I would probably have to install lots of regularly spaced "I" beams or Larsen trusses to achieve a friction fit. Annoyingly, the rafters are variably spaced at around 400 mm (the some are 450mm!) so it is not simply a case of hanging these directly from them. I would have to screw the larsen truss ends into the purlins first then fit the plywood inbetween for the friction fit. I would need approximately 30 of these and then cut every 1200mm batt, so pretty tedious to do.

If I put the batts in horizontally I could put a horizontal "I" /larsen truss beam in between the purlins, though I would probably have to hang these vertically so that the width between is consistent for the depth of insulation. So a bit of a phaff. Also, the width of bats is inconvenient so would have to be cut down.

To add to the difficulty, batts would require a membrane above to minimise wind washing from the ventilation above and also an air tightness membrane below the insulation. This all adds to the trickiness of the installation and the cost.

Thermafleece would probably be the way to go rather than wood fibre as the sharp angles with the purlins may be easier to fill with the softer wool. Hemp is another option

The risk with PIR is obviously condensation on the purlins. Moreover with the purlins being composed of two pieces of wood glued and clamped, there is a risk of condensation if there are any gaps inbetween (so would need to seal these). But at least there would be plenty of ventilation above the insulation, with the ventilation in the rafters linking to the loft space which is cross ventilated at either end of the gables.

The big sheets of PIR would also minimise the joints through which moisture could enter the roof space and also avoid cold bridging (though appreciate moisture has a way of finding its way in however well this is installed).

I guess there is also the option of loose fill...

I would really appreciate some advice on which way I should go on this. Many thanks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18404 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18404 Wed, 11 Feb 2026 15:41:09 +0000 Mikeee5
Has anyone experienced white marks on external brick cladding and damp problems on the internal walls following the installation of external insulation? I have attached a pic of one of the walls being affected. This is the side elevation of of a 3 sided semidetached property, the front elevation wall is being affected on the adjoining property.

Regards

Mikey]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18403 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18403 Mon, 09 Feb 2026 13:32:54 +0000 Nick Parsons https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18270 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18270 Sat, 01 Mar 2025 16:21:48 +0000 Artiglio
I’m looking for a half way decent humidistat 6” extractor fan, the room it’ll be in suffers from damp ( one wall is half height below ground level, and house has had all sorts of changes in its history that have’nt helped), the fan is intended to hopefully improve the internal conditions a bit until such time as the causes can be dealt with.
Also internal condensation can be a problem. Lots of fans available, however does anyone have experience of either one they’ve been happy with or ones to avoid. Noise levels will be important.

Many thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18400 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18400 Thu, 29 Jan 2026 10:14:05 +0000 DanS
I'm currently detailing my self-build home - Main wall fabric: Plasterboard+skim (breathable paint), timber frame studs + FrameTherm40, 9mm OSB, breather membrane, 50mm PIR, 50mm cavity, masonry skin. All standard (ish!** no VCL!).

My issue is the 50mm cavity I believe offers a ventilated space to deal with water ingress through the masonry. BR AD-B says this cavity must be sealed by fire rated cavity barriers, top, sides, openings, compartment floors etc. So what's the best practice here?

Intumescent cavity barriers obviously maintain the open cavity and solve this issue, but there are plenty of other compression mineral wool style barriers/socks that are approved for this use in timber frames with masonry skin. How is this acceptable? Plus dividing/sealing the cavities must be of some benefit thermally!? My gut tells me that a vapour-open sock would be the best of both worlds, but none of the manufacturers datasheets express this as a feature. And they appear to be wrapped in polythene...
I don't really understand why the need for a 50mm cavity, if it is then going to be sealed shut for fire spread. A 25mm (or even 10mm! - as is now commonplace with T&G PIR cavity insulation) would suffice if circulation is not deemed necessary?

Thanks in advance :)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18399 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18399 Sat, 24 Jan 2026 16:41:33 +0000 gravelld
Tescon Vana works up to 90C, but that would be no good for the flue, certainly.

What have people used?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18395 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18395 Sat, 17 Jan 2026 11:30:06 +0000 Rex
Easy peasy! But he and his wife do live in what can only be described as a complete and utter chaotic mess (think those house clean TV shows!) and there was not way I was going to empty the under sink cupboard with the very limited space they have. They can do that.

He called his friendly plumber and later reported to me that is was a fat-ball in the trap. But he also told me that the plumber told him that there is now a kinda fat-ball vacuum that plumbers use to clear kitchen traps without having to access the trap

Purely out of interest, what is this tool? Surely it cannot be as efficient as dismantling the trap and giving it a through clean?

But what do I know?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18393 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18393 Fri, 09 Jan 2026 14:09:23 +0000 alant We are going to install an engineered wood floor on top of 22mm OSB subfloor in the living area (first floor) of our house and we need to reduce the impact / noise transmission to the bedrooms underneath. We fitted 100m of Hemp batts between the I joists but this has been pretty useless at reducing much sound.
Does anyone have any recommendations of what to install as an underlay of up to 10mm thickness to reduce impact noise. Ideally we don't want to use material that has lots of VOC's or off gasses. We have tried several specialist retailers and it seems that they are very good at quoting dB reduction for complete systems of floor make ups not for providing reliable figures for just underlay. Some say Cork is good but its relatively light so i can't see how that helps much.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15876 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15876 Tue, 25 Sep 2018 19:55:13 +0100 andyman99
Render - 150 EPS - 215 Block - Plaster (poss plaster board on battens).

Will this be OK or do I need add a vapour control layer?

Many thanks again

Andy]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18392 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18392 Thu, 08 Jan 2026 15:52:17 +0000 Jeff B 2025
It seems all our efforts to improve the insulation in the place combined with solar PV and solar thermal panels have paid off in that we are now in band B (previously D).

I have a question regarding the estimated annual figures for the space heating and hot water requirement:

The annual heating figure in the new EPC is 9168 kWh and for hot water 2195 kWh – total 11,363.
1 litre of kerosene yields 10.35 kWh of potential energy. As my boiler is obviously not 100% efficient and is actually 90%, then I assume in my case that 1 litre of kerosene potentially would produce 0.9 x 10.35 = 9.31 kWh of “useful” heat. So 11363 kWh of useful heat would require the burning of 11363/9.31 = 1220 litres of kerosene.
This is odd because we use on average 1500 litres of kerosene p.a. combined with the fact that our solar thermal system provides us with hot water for most of the summer months and the boiler is off for weeks at a time. 1500 litres is equivalent to 13965 kWh (boiler efficiency 90%), some 2602 more than the EPC prediction.

My question is why is there such a large difference between the calculated and the actual oil consumption? Is the boiler less than 90% efficient? I’d be surprised, as it is only 4 years old and regularly serviced. Or is there some other factor that I am overlooking?

I’m just concerned because a prospective buyer (if a bit geekish like me) might question this inconsistency!

Thanks for any feedback.
Jeff]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18390 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18390 Sat, 03 Jan 2026 00:37:17 +0000 ChrisinYorkshire
What do you recommend for insulating an RSJ when:

- the wall is mostly solid stone build, and being insulated internally with wood fibre board, lime plasters, breathable system, however;
- there is a retrofit cavity section that spans approximately 4m width of the wall, which involves a row of windows and an external door.
- the inner leaf of this part of the wall has the RSJ above it, with a cavity tray extending to the outer leaf.

I'm concerned that if I fill the RSJ with wood fibre batts between the flanges and front this with rigid wood fibre insulation, that vapour might reach and condense on the beam and saturate/overload the insulation more often than it can dry out, particularly in the winter months - is this a valid concern? Equally I'm concerned that if I fill the RSJ and cover with non-breathable insulation, XPS/PIR or similar, that moisture will creep in and be trapped against it. Since the RSJ is already in situ, I cannot fit a perfect DPM around it.


Other factors:

The RSJ has had considerable rust with flaky rust sheets that I've mostly removed and were presumably caused by approx. 30 years of kitchen humidity with no extraction. I am planning on scraping off any remaining flaky rust and treating RSJ with Jenolite rust convertor.

I can quite easily reach into the cavity and insulate the cavity side of the RSJ.

I also need to consider fire boarding, particularly with this being above the main entrance/exit to the house.

Any guidance most greatly received! :-)

Chris]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18389 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18389 Wed, 31 Dec 2025 09:14:59 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18388 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18388 Fri, 26 Dec 2025 10:35:16 +0000 Nick Parsons
I don't know how many I'm writing this to now, but hang on in there and let's get GBF/AECB forum thriving again!

All the best]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18378 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18378 Thu, 27 Nov 2025 18:11:24 +0000 Rex
I have the boiler and DHW cylinder adjacent to each other in the utility room. Probably less than two metes away, is a toilet with hot water to the basin. The HW pipe, obviously goes from the top of the cylinder, into the ceiling and drops down to the basin HW tap.

Recently, when turning on the tap, based upon the noise from the issuing water, there is considerable air in the system. It does clear but like the Terminator, it will be back. All other HW taps do not have air coming out.

Since it's running at around 3 bar, I assume if air is entering, water is leaking out somewhere? But there is no evidence for that. Where could this air be entering and how can I prevent it.

As an aside, all cold water is mains and there is no air from any taps.

Grateful for any ideas.

Thanks and toodle pip]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18385 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18385 Fri, 19 Dec 2025 18:35:34 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18356 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18356 Mon, 29 Sep 2025 16:38:37 +0100 Artiglio
My mother ( mid 80’s years old) is downsizing and we’ve purchased a small 1920’s bungalow , it’s pretty much untouched in terms of insulation since it was built. Basically only 100mm of fibreglass in the loft.

There’s a bit of money to make some improvements , with the caveat that where possible we do it ourselves.

The aim is substantial improvement and comfortable living rather than ultimate energy efficiency.

I’m struggling to find a definitive guide to iwi with insulated plasterboards. Rooms are small and we don’t want to loose too much space.

Wall construction is 9” flettons, painted pebble dash on 3 sides, 4 side has only 700mm to neighbours wall and the eaves and guttering mean there is only a 6” gap. Gutters have been cleaned and leaky joints fixed.

Other side has 2.O overall gap to neighbours. Again very protected from weather, only front and rear elevations have any real exposure.

There is evidence of damp internally but this is pretty much all related to condensation behing previously fitted cupboards and units and very old aluminium framed windows.

Is it possible to bond insulated board direct to the existing wall? If so i can use a thicker board than if I were to use a battened system.

There will be mvhr . Heating is going to be gas combi boiler. Floors have been lifted, sub floor swept clean, joists repaired. Where fireplaces had been removed but screeded flush to the floor, these have been lowered and now the timber floor joists extend over. Floor joist are on sleeper walls and don’t touch the walls. There will be rockwool insulation between the joists before chipboard flooring goes down.

At least that’s the plan, i’m struggling a bit to find an easy to understand comprehensive guide to what i should be doing . Can anyone point me in the right direction?

Thanks in advance.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384 Sat, 13 Dec 2025 14:22:50 +0000 Rex
Have the replacement panel up and running and since if it activates, it is impossible to hear the external sounder in the house and particularly if entry is from the back.

So this time, I have fitted a sound bomb, if for no other reason that the excessive inside noise is slightly disorienting.

However, I now have a very faint humming from the sounder and wondering if it is induced by the incoming mains.

The red line is roughly the cables from the sounder that go on the bell terminal on the board. These two wires go under the plastic housing and enter the interior just below the terminals. The yellow lines are the mains to the transformer.

I know little about the science of electricity but could the transformer and/or the incoming mains be inducing a micro current in the sounder wires that is causing the sound to hum?

If so, what is the solution? Reroute the wires so they do not cross the incoming mains or go under the transformer? Reposition the sounder?

Grateful for any suggestions.

Compliments of the season to one and all,

Rex]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18363 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18363 Sat, 11 Oct 2025 11:24:00 +0100 Rex
Want to replace the 6v 330mAh Ni-MH back-up battery. The one I have removed has the following markings - 280H5A1H

When I Google search for a similar, I have found 7.2v Hi-MH GP320BVA6 (https://www.buyabattery.co.uk/alarm-bell-box-battery-7-2v-7-2-volt-ni-mh-gp320bvh6a6.html) Apparently, this replaces 6N280BC

What does all this mean? Can I replace a 6v with a 7.2V? What does the code tell me?

Thanks and toodle pip]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18369 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18369 Thu, 13 Nov 2025 10:13:17 +0000 owlman
TRÅDFRI
LED bulb E27 470 lumen, smart wireless dimmable/warm white globe
£12Price £ 12
Energy efficiency class C]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18382 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18382 Sat, 06 Dec 2025 10:15:46 +0000 revor
https://insideevs.com/news/780568/tesla-lg-battery-pack-defects-china/]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18364 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18364 Tue, 14 Oct 2025 20:15:08 +0100 Rex
Just been watching an item on the BBC regarding below standard EWI (https://www.bbc.co.uk/news/articles/c203rnepzexo) I guess this is similar to the poor cavity insulation.

Is the failure of either type of insulation because it is a mistaken concept, or because of poor installation by snake oil installers?

As an aside, am not considering either, just interested.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18370 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18370 Sun, 16 Nov 2025 19:34:48 +0000 Rex
https://www.bbc.co.uk/news/articles/c0rpy7envr5o]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18376 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18376 Fri, 21 Nov 2025 14:47:45 +0000 ChrisGT