Green Building Forum - All Discussions

New Green Building Forum & Website

BWork — Mon, 01 Sep 2025 15:58:30 +0100

Crowd funding

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

Welcome to Guests

GBP-Keith — Tue, 15 May 2007 18:00:44 +0100

Subscribing to and participating on this forum is no longer available to new users from December 2023. However it is a great resource to browse. Existing subscribers can continue to participate as normal.

MVHR, heatwaves, chiller?

john.connett — Thu, 02 Jul 2026 12:54:37 +0100

My house in Cambridge had a low energy renovation around 15 years ago with triple glazing, increased thermal insulation, solar thermal system, thermal store and MVHR. The MVHR unit is a Vent-Axia Sentinel Kinentic BH.

For most of the time since it was installed it has worked very well and I rarely needed to open any of the windows. However, during the recent Amber Heat Alert the house overheated badly. Possibly the high humidity made it worse than in earlier years or my age and, maybe medication, made me less resilient.

My suspicion is that during an extended heatwave with tropical nights the MVHR is unable to maintain comfortable indoor temperatures. With or without a summer bypass, if the air temperature is over 35º C outside then the MVHR will import that air. Even if the air temperature drops lower overnight it can't catch up and the house continues to retain the heat, made worse by the high quality of thermal insulation.

Some form of air cooling may be required! My back garden is nowhere near big enough for a ground-coupled heat exchanger so active cooling may be an option.

I have seen an example where a reversible heat pump was connected to a water/air duct heat exchanger (eg. Zehnder ComfoPost). However, my house has a gas boiler.

Has anyone else experienced similar problems or can suggest possible solutions?

Nordan v Allan Brothers

Victorianeco — Fri, 03 Jul 2026 00:04:36 +0100

Any preference even looking at 3G Alu-Clad?

1900s cottage retrofit advice

Charli — Mon, 15 Jun 2026 12:07:43 +0100

Small house- 74m2 over two floors- 2 up 2 down 1900 solid-wall semi. With a large garage (another 30m2) down one side that I want as a 'clean and nominally heated studio/workshop' that needs a new roof. On the right (downstairs) is a very narrow gennel. On the front is the complexity of lots of electrical wiring that will be bureaucratic and probably expensive to move. Uninsulated concrete floor downstairs. Heating is a log burner with boiler- wood is free in money terms, but not in effort (there is a gas supply). South facing roof.

I've got 30K and want a comfortable house with the lowest bills. Happy to DIY almost anything, I'm capable and practical and find it all fascinating.

With a south facing-roof solar pv is worthwhile, can fit 4.2kWp of panels on the roof and there's adjacent south-facing land that I could fit more on. I think that 6kW of panels with excess going to heat dhw will give me largely free hot water for most of the year.

Insulation would be next on my list. 400mm loft insulation is easy.
Garage I'd do a flat or pitched roof with 150mm pir in, and some form of roof lantern/velux. And IWI. The garage has no direct heating and that’s fine.

Need new windows on the north side- pvc triple glazing. The lack of condensation on the windows ever is worth it.

EWI would need the roof extending, the wires moving on the front and I've no idea what to do with the gennel (internally the narrow stairs are there). Would rockwool and lime render play nicely with the 'old houses are always damp' line I keep reading? XPS below dpc? I've no idea how far down the house goes yet- there's unlikely to be much in the way of foundations.
IWI would mean no thermal mass (wfh so in the house all day everyday largely), the kitchen/bathroom would have to wait until those rooms needed some work (I don't want to rip out a perfectly good bathroom for a few years). And the rooms are already tiny- but I could sacrifice enough for 50mm pir. Which is better than nothing, but not inspirational. (Still no idea what to do on the stairs-wall).

Any ideas/inspirational stories/words of warning/things I should go and think/read about?
Many thanks.

Skylights, roof windows and clerestory skylights

tony — Mon, 11 Jan 2016 16:22:22 +0000

Roof windows seem to cool rooms too much.

U values assume steady state and an indoor and out door temperature

But skylights can radiate heat to outer space which is at absolute zero.

This heat loss dominates on any clear night.

Should heat losses from these be reassessed?

AAHP in everyday houses

fostertom — Tue, 30 Jun 2026 09:59:42 +0100

I've reached the point of considering air to air HP (AAHP), maybe with cooling aka AC, as a lowest-intervention solution for boiler-replacement in ordinary small houses (whether 'modern box' or old/rambling cottage) which no one's planning to comprehensively insulate, even incl ones with no existing central heating of any kind.

I need to get up to speed with the varied considerations, like we've gradually learned with wet systems, UFH, ASHP etc. Not least grant aid. Aware of the horrors of 70s/80s cheapo air-heating, and duct-routing issues. And DHW.

Any pointers?

Air Con

Rex — Sun, 28 Jun 2026 13:44:21 +0100

What ho one and all,

There was a recent article in the newspaper regarding the a/c numbers in different countries. Japan (my wife is Japanese) has around 91% domestic a/c installations, the UK, less than 5%.

My wife is really, really keen to get an a/c in our house. 3g, 180mm of Warmcel insulation; I don't think it is going to happen as I'm not drilling large holes through the glazing or walls. She even thanks we could replace one of the 'smaller' glazing panels to accommodate the a/c pipe. No way Jose!!!

Her further research finds this kind of unit: https://nessally.co.uk/ Apparently, according to her, they are very popular and very good. My feeling is, it is all marking hype and a money making scam.

Is there any 'new' technology that makes these portable a/c units as good as the blurb suggests? Are they generally any good or essentially, just an expensive fan that will be in the skip in a few years time?

Grateful for your thoughts and opinions.

Skylights

owlman — Sat, 27 Jun 2026 16:02:43 +0100

I'd like to introduce more natural light into my bungalow living room space approx 8M x 8M. Skylights seemed to be the obvious answer rather than knocking down walls. However, the loft space is of a Fink trussed construction which I can't cut or change.
These large trusses are 70mm x 35mm timber section at 450mm centres and with plenty of length eaves to ridge. I'd seen firms that do long narrow 3g fixed lights for this sort of application. but I'm unsure as to how they'd look from the interior. I'd thought of three in a row on alternate truss spaces with 2 x flat ceiling sections between. It's a pantile roof so flashing detail could get messy. The good news is its N. facing.
Can anyone spot any flaws in my idea? Has anyone attempted skylights in a trussed roof situation and does anyone know of a decent firm who make the lights.

Telegraph Article - Eco rebuild

borpin — Tue, 16 Jun 2026 12:03:45 +0100

Not sure if this link will work, but this is a really good looking house IMHO.

https://www.telegraph.co.uk/gift/c79c96400f3a8bff
https://www.telegraph.co.uk/money/net-zero/i-spent-900000-creating-the-ultimate-eco-home/

One thing I noted is that he is funneling his MVHR extract into a 'cupboard' around the Heatpump. That sounds like an excellent idea.

Batteries

djh — Fri, 08 May 2026 17:57:27 +0100

What's the state of play with batteries these days?

I am generally aware of the 'big' batteries supplied by the likes of Tesla, Fox ESS etc

There now also seem to be much smaller products aimed at the 'balcony solar' market and I don't know anywhere near as much about them :cry: So ...

(1) are they actually legal and what regulations apply?
(2) does anybody know which ones are good and which ones to avoid?
(3) a lot are aimed at integrating with balcony solar, but I already have solar on my roof with microinverters, so I just want an AC connected battery. Does that change things?
(4) how are they controlled - which require cloud or other external connections and which can be controlled locally somehow?

I'm sure I'll think of some more questions, but that'll do for now! :bigsmile:

Embodied carbon, EWI, CWI, ASHP, Exposure zone 4

fostertom — Thu, 11 Jun 2026 11:42:34 +0100

A multi-faceted issue:

1. The new thinking, which removes high-standard External Wall Insulation (EWI) from its pedestal as the default/ideal for retrofit, on grounds that the embodied carbon (i.e. the CO2 and CO2-equivalent released to atmosphere) created in 'quarrying', manufacturing, transporting and installing EWI, is likely to exceed, sooner and for longer duration, the in-use carbon it saves over the building's subsequent lifetime.
Couple that with the rapidly declining carbon content of mains electricity, which means that electricity consumed over the building's in-use lifetime, already and increasingly carries little penalty in global heating.
Then, compared to super-insulation hence consuming minimal energy-in-use, the alternative of omitting the super-insulation hence consuming plenty of 'harmless' electric (via heat pump) energy-in-use, can actually be a lot better for planetary climate, both in this emergency-short-term, and over the building's lifetime.

2. Retrofitting the 30% of UK building stock which is still-uninsulated cavity wall, with or without EWI the cavities should be filled (CWI), as it's near-impossible to prevent outside air blowing around in the cavity. Even fitting EWI can't be relied on to seal the multiple cracks, entry points and open-to-loft top of typical cavities - outside air is still liable to bypass the EWI, separated from the interior only by the inner skin. External render can't be relied on either. Even Partial-fill CWI is poor at preventing outside air blowing around in the cavity; it really needs to be full-fill CWI.

3. CWI is cheap to install, with small embodied carbon. So, considering both 1. and 2. above, the new default looks like installing full-fill CWI, without EWI, along with electric (via heat pump) energy-in-use. In which the CWI is an indispensable part, hardly works without.

4. But what about cavity-wall buildings in high-exposure areas? There, CWI is pretty much banned by Building Regs, certainly with traditional 50 wide cavities (as opposed to more recent 100-ish cavities) and certainly in exposure Zone 4 areas (i.e. most of the west/southwest of UK). External render doesn't help.
https://assets.publishing.service.gov.uk/media/606c366ad3bf7f400e10af54/wic-final-report.pdf also gives little hope that a coat of gunk would make the wall more suitable for CWI.
Does anyone know different?

5. Without CWI, a house has nearly zero insulation, if outside air is blowing about only separated from the interior by the inner skin - even if accepting plenty of 'harmless' electric (via heat pump) use. Especially if extending an unfilled cavity-wall house; the existing cavity wall becomes an internal wall, but super-cooled because its cavity is continuous with the still-external parts of the cavity wall adjacent.

6. Similar applies if you've EWI'd your half of a semi-detached house; your unfilled cavity, inside the EWI, will be super-cooled because continuous with next-door's unfilled cavity.

So WTF to do about all this? Any solutions, bright ideas?

(AI) data centres, water, geo

minisaurus — Sat, 06 Jun 2026 08:22:14 +0100

I’m surprised water consumption by data centres is an issue. Presumably, in countries with at least half-functioning planning systems, a centre could be forced to 1) use geo energy for primary cooling, and 2) build a closed circuit water circulation (with filtration) system for the needed-in-summer cooling fans, with a restriction on the amount of drinking water the centre be allowed to use per annum?

My workplace - large hospital - achieves all cooling needs using geo energy - approx 100 holes approx 70m depth. We even heat space & water (almost) year round using same energy & some extra electricity to get the temp up from 40C to 68C

If I wanted to build a data centre, I’d do this.

However, I don’t want to build one :)

Finally finished all the eco energy improvements! De-carbonized 190 year old house!

stonecold — Mon, 15 Jun 2026 03:08:20 +0100

Its finally finished!

The house is no longer stone cold, damp, with slugs getting in. It's warm, comfortable and the bills have dropped loads.

Since the planning started 4 years ago we have FINALLY got the last job done!

Here's the main jobs done
- LPG cooker with non-fan oven ?? induction hob and electric fan oven
- Oil boiler and immersion heater ?? Heat pump and central heating refit
- Solar PV ? with large battery, and gateway for off-grid
- EV charger
- Solid wall insulation - Diathonite lime/cork EWI - from 2.0U to 0.60U
- Triple glazed timber/alu - all but 2 windows, 3 doors
- Raised concrete patio bridging damp course ?? lowered porcelain patio tiles
- MVHR and removed bathroom and kitchen extractors, recirculating cooker hood
- Wood and recycled supasoft loft insulation top-up
- All light fittings now use replaceable LED bilbs ?

oh and we needed a new roof!

Thank you to everyone for their suggestions and answering so many questions. I'm so glad GBF is still here - I can't remember who is currently running things but many thanks! There's nowhere similar. :cool::cool::cool:

No doubt I will still post since there are other important repairs needing doing plus some accessibility improvements, I'm hoping to get eco-friendly stuff for. :cool:

Boiler Upgrade Scheme grant now £9,000 for oil or LPG replacements

stonecold — Sun, 14 Jun 2026 23:31:43 +0100

Very little coverage of the grant increasing to £9,000 (from £7,500) for moving to a heat pump and even hard to confirm on UK gov websites...

England and Wales only (Scotland has a £1,500 rural uplift already).

LPG or oil boilers only so mostly rural/off-grid homes.

https://www.airahome.com/en-gb/blog/heat-pump-grant-9000-uk

I only heard about this last month in a quote for a heat pump (now installed! ?)

Retrofit project

ChrisGT — Wed, 13 May 2026 08:29:03 +0100

Starting a retrofit of a new house shortly. Its only 25 years old!
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?

PHPP or Similar?

Victorianeco — Wed, 03 Jun 2026 20:41:28 +0100

Is this easy to use? Or anything alternative?

Looking for my own interest more than anything?

Any tips or thoughts?

Air-to-air heat pumps

djh — Tue, 18 Nov 2025 17:34:03 +0000

So, the government has included air-air heat pumps in the BUS (see https://www.gov.uk/government/news/discounts-for-families-to-keep-warm-in-winter-and-cool-in-summer ), which has set me thinking about them again. Does anybody have any ideas about whether this will decrease or increase prices, and when. Or how to find a competent and trustworthy installer? (in Suffolk if it matters) And about any specific products?

PS They've also included subsidies for 'heat batteries', but since heat batteries are now more expensive than electrical batteries for the same capacity, it seems like another poorly thought-out scheme!

Solar pv edge

revor — Wed, 18 Oct 2017 19:25:28 +0100

Does anyone have a view of whether solar edge is worth the extra expense? I have been quoted Â£7K for a 14 panel 4Kw system and do not know whether this is good value or not.

Solar Panel Fire

Rex — Thu, 28 May 2026 20:27:00 +0100

What ho one and all,

Just seen this on the Mail on Line web site.

https://www.dailymail.com/news/article-15854881/solar-panels-explode-home-explodes-flames-family-inside-escape.html

Will we ever hear why this happened? Bet the estate developers will have a nightmare with all the other owners wanting reassurance their solar panels will not catch fire. There is a 100 Taylor Wimpey built estate near me and they all have solar panels.

Help with Tanking/breathability

Brightonreno21 — Tue, 26 May 2026 16:23:27 +0100

Hello
We live in Brighton and have a Victorian terrace which is south facing and high on a hill so tends to take a bit of a battering from rain and wind. A lot of the houses on our road suffer with damp in rooms at the front

On moving in, we noticed active damp in a master room at the front of the house. The opinions we got at the time where either very expensive damp proof materials (chemical injections etc), or we were offered the suggestion of using tanking slurry to waterproof the wall. This has effectively worked, that room is now dry.

We are now doing a Reno and having read much more about breathability we’ve started to worry about this. We are wondering if we get the render done in breathable lime render, could we keep the wall as it is (remove the tanking will also be damaging for it we understand)

We’d welcome views on how much of an issue it would be to have one room be tanked/not breathable - if we then get the render done breathably.

Whilst we are reluctant to invasively remove the tanking we don’t want to be storing up too many problems

4.5+ sqm 20mm thick aerogel insulation

mdaley — Tue, 26 May 2026 11:31:06 +0100

I have around 4.5m² of surplus 20mm thick aerogel blanket rolled up. I bought it for insulating a room where I didn't want to lose much space. It is exceedingly efficient with a thermal conductivity of 0.017W/mK at 20°C, and it is A-rated for non-combustability.

Given that it was rather expensive to obtain, I would like to sell this surplus. I can see from the Passive House Store that, from them, it would cost around £230/m². I'm willing to part with it for around half that as I need it to be out of the way. So I would be happy to accept £500 for it.

I can provide a spec sheet and a CE mark cert.

There are various offcuts that could be used too. I will throw these in free or you could negotiate a price if you just want a small amount. For example, I've used small amounts when building extra insulation into existing doors.

The way I used it was to place it between battens and put boards over the top. It's on the internal side of an already insulated cavity wall so I decided to not be too worried about cold bridges from the battens and fixings. Ideally you would want a continuous layer with no battens but all my attempts at this failed, given my lack of appropriate skill and experience.

I prefer pickup from my location in Bristol. Wrapping and transport would be hard as the roll is quite heavy.

Ants

Rex — Tue, 05 May 2026 18:28:24 +0100

What ho one and all,

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

Kitchen worktop replacement

djh — Fri, 15 May 2026 11:42:58 +0100

We're thinking of replacing our kitchen worktops. We have laminate worktops and some of the glue-on end pieces keep coming off and get damaged.

We're considering getting a granite or quartz overlay rather than a full worktop replacement. Does anybody have any experience of these? What's your preference for replacing worktops?

Learn about lead above glass

tony — Wed, 13 May 2026 05:43:49 +0100

I’m certain that I’ve done this one before but can’t find it. I talked about having lead above glass.

See this picture : - (also further down the thread)

https://share.icloud.com/photos/066qjqEKhBi6whb1qP5FrnWUg

https://www.dropbox.com/scl/fi/15k1oufc1bdnmtthlvbe8/lesson-to-learn.heic?rlkey=sgq0970dw33medi6mk29ceupv&st=vyoi58g9&dl=0

The white streaks running down the Glass are caused by rainwater slightly dissolving the lead, which you can just see above the glass, and taking tiny amounts of lead oxide down the glass. You might think that you could just clean this off easily. You can’t. The lead oxide etches the surface of the glass irreversibly. Ugly and fully preventable.

All architects, glaziers, conservatory manufacturers and in general anyone who specifies glass for use on roofs needs to understand this. And never use lead above glass.

EWI + Cavity Fill versus cavity fill only

Victorianeco — Tue, 05 May 2026 20:28:22 +0100

I am looking for a comparison of the real-world savings and practical implications for two insulation strategies on a 1960's uninsulated cavity wall property.

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

vacuum glass

chrisinbrighton — Mon, 11 May 2026 21:04:47 +0100

Has anyone here used vacuum glass panels?
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.

aluminium roofing nails

chrisinbrighton — Fri, 17 Apr 2026 19:53:40 +0100

Has anyone got any views on using aluminium nails for a slate roof. My roofer says they are better that copper as they `give ` a bit and have bigger heads.
My own experience of aluminium on bikes is that it can go brittle with age.

Thanks

Do i need a soil vent pipe in front garden?

thebeacon — Tue, 12 May 2026 08:21:32 +0100

I have been renovating a Victorian Terrace house. I had it re-plumbed a few years ago. When doing so a durgo vent was fitted in the loft.

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,

Shattering

Rex — Mon, 04 May 2026 19:31:46 +0100

What ho one and all,

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

Trustworthy trades to assess/install ASHP and solar panels

Louis036 — Fri, 01 May 2026 15:39:53 +0100

Hi everyone

I am looking into ASHP and solar panels for the house I moved into recently. I need a feasibility survey and want to find a trustworthy surveyor and tradespeople. I am currently with Octopus Energy for gas and electricity supply, so I started there, but have had this weird experience where they kept not showing up for initial phone discussion appointments made with them. Three times - with no explanation from the survey department or their customer services. I have no faith that Octopus will be able to do the job if they can't even get this far.

So I'm looking for trustworthy and reliable alternatives in the Havant, Hampshire area. Does anyone have experience of someone like that in this area, please?

Many thanks,
L036

Peak Cluster CCS pipeline

ChrisGT — Sun, 19 Apr 2026 23:00:46 +0100

CHESHIRE west Council is considering a motion to prevent this carbon capture and storage project going ahead in a couple of days. CO2 from several peak district cement factories will have the CO2 produced during production removed and pumped out by pipeline into Morcambe Bay depleted gas fields. The cost, a mere 5 billion! Theres a lot of opposition, not sure whether just nimbyism or maybe due to cost and unproven technologies' efficacy being exagerated. Would be interested in any views on other alternatives to enable co2 from this sector being reduce.

Hempblock - has anyone tried?

minisaurus — Sat, 11 Apr 2026 11:40:30 +0100

I thought these ones looked interesting: https://uk.hempblockinternational.com/ - load bearing, no mortar needed, insulation, noise reduction & presumably pretty green.

Has anyone experience of them? The positives are many, but what are the negatives? price I guess

Help with wet timber frame wall

andyman99 — Wed, 15 Apr 2026 10:35:53 +0100

Looking for a bit of advice please.

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

Supporting the Green Building Forum (/AECB)

Nick Parsons — Tue, 07 Oct 2025 12:20:39 +0100

I see that, of AECB's £6500 target for the future development of GBF, £271 has been raised, with, I think, 30-something days of the 'campaign' to go.

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'.

Prestressed stone massively cuts embodied carbon

fostertom — Thu, 12 Mar 2026 08:19:49 +0000

This is interesting:
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.

Office Desktop Materials

Victorianeco — Fri, 10 Apr 2026 07:20:37 +0100

Looking to refurb my office - 6 desks 1800mm x 700-800mm depth

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

Last year I helped build my daughter an extension.

tony — Sun, 12 Apr 2026 16:34:50 +0100

Last year I helped build my daughter an extension. This is the story of the first three weeks :-

Document here - https://docs.google.com/document/d/e/2PACX-1vQ2s-HB1cud4gZISwGuQvP8oIifaCVcF94ySusEaaPanqcCf4md3UPJDOKeD02Gg9MitbCVb4vXe5SW/pub

Is a VCL needed below a cold roof

Peter_in_Hungary — Tue, 31 Mar 2026 18:59:32 +0100

I'm doing a total renovation of a single floor dwelling. There is a new cold roof with the ceiling make-up of plasterboard - 300 mm glass wool - ventilated roof void. The ceiling joists (100 x 150 at 900 centres) are within the bottom part of the insulation. The roof is tiles with a breathable roofing felt.

The question is - Is a VCL above the plasterboard (i.e. on the warm side of the insulation) required?

Who should be on the design team?

tony — Fri, 10 Apr 2026 15:32:59 +0100

This is probably the most basic of fundamental questions, “who should be on the design team?”.

I’m gonna make some suggestions

1) the client
2) the designer
3) a building physicist - they could be a consultant
4) an engineer
5) an energy assessor
6) a QS ?

? Crack on then ……

front garden path, driveway and hardstanding materials ?

zak99 — Sun, 26 Mar 2023 23:01:59 +0100

Hi,

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?

external insulation

chrisinbrighton — Sat, 05 Mar 2022 20:47:49 +0000

Im just starting to plan the renovation of a Welsh chapel,i can imagine il`l have lots of questions on here!

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.

Foundations for an extension

tony — Fri, 27 Mar 2026 09:22:41 +0000

His an interesting question. Should the foundations on an extension to a house be laid at the same depth as the foundations on the house itself? If not why not?

In sustainability terms, it seems crazy to build hugely deeper foundations which use an awful lot more concrete and produce additional problems and costs of disposing of the spoil when it may well not have been necessary. I think this approach would be better for the environment too. :-)

IWI transition risks/mitigation

ChrisinYorkshire — Mon, 16 Mar 2026 11:29:31 +0000

Hi Everyone,

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.

Testing

fostertom — Tue, 24 Mar 2026 11:40:09 +0000

Testing - has there really been nothing posted for 6 days? AECB mod, is that so, or is it just not coming through?

Company failure Kill Switch

revor — Thu, 04 Dec 2025 16:25:55 +0000

Whether you believe in China building in a kill switch into your EV or solar panels or not I have been subjected to and inadvertent unplanned kill switch. My Italian Inverter stopped working on Monday morning at 8.30 am. It was lifeless. No error warnings preceding it going down It just stopped. The monitoring on the PC and smart phone froze at that point but the historical data was there. After doing some digging discovered that the inverter manufacturer is in the Italian form of administration i.e running down the company and the process started a few month ago. The software driving and monitoring the inverter was developed by a 3rd party who then hosted the network of installed inverters. It seems that the hosting company has pulled the plug, understandably as who is going to pay them. The opinion of my original supplier who broke ties with the Italian manufacturer about 2 to 3 years ago is that the inverter should work albeit without any form of monitoring. I have had over the time I have had the inverter, a few tweaks to my software, remotely from Italy so mine may not behave as told it should. Either way without the monitoring it looks like it will be useless. I have emailed the hosting company to see if they can confirm that they have stopped hosting and that it happened on Monday, then I know for certain if that is the cause and not a hardware problem. They have been lacking in a response so far. One solution off course would be for the hosting company to do a subscription service I guess there will be several thousand inverters out there. Whether they will remains to be seen.

Breathable flooring, main reason/s?

Gareth J — Mon, 09 Mar 2026 20:04:02 +0000

A friend has just put down a limecrete floor in a solid stone wall built house. Part of a system with foam glass as an insulation layer underneath.

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.

Trickle Ventilator problems

tony — Sat, 07 Mar 2026 08:36:18 +0000

Trickle ventilators

During the 2021/2022 season at DraughtBusters we started to encounter a lot of problems with trickle ventilators. These have been even more of a problem prevalent in 2026.

Some of the problems are : -

Draughty when closed
Insect protection gone or decayed
Wouldn’t or couldn’t close
Householder didn’t know how to open or close them

Draughty when closed.
We found that in a lot of cases draughts were emanating from the trickle vents even when closed. These vents were surprisingly insubstantial and it was rather a shame to find that they were letting in draughts. It would be possible to seal them to the frames to prevent some of the draughts but this would be tricky. If the windows can be used on a ventilate position, i.e. fixed in a secure vent position using the second position on the window handle then we recommend sealing up the trickle ventilators.

Insect protection gone or decayed.
We have identified whole estates where trickle ventilators have lost their insect protection, these are often with ‘over the head’ type ventilator arrangements. The insect grilles become brittle and fall out or are knocked out with window cleaner’s brushes.

Won’t close - this is different from draughty when closed as those do close but a draught enters between the frame and the vent. Some ventilators have plastic clips that hold the vent in place and these can break and the vent flaps about remaining open all the time, others just don’t close and allow draughts all the time even when closed.

Householder can’t open them, we didn’t like this one! There are a lot of different types of trickle ventilators many and varied ways of opening them some push left or right some up and or down, others click open, while others need a sharp but gentle press. It is nor really surprising that some people can’t open them.

Trickle ventilators are the bane of a DraughtBusters life, they are intended to let draughts in, in a controlled way. They are proving themselves to be unfit for purpose. We see ventilation as an active thing, to be controlled by occupants as and when required and a general government directive of ‘one size fits all’ is resulting in draughty homes. We have said before that draughts do too much by way of ventilation when it is windy and not enough when it is calm. Trickle ventilators should now be outlawed in favour of saving energy. Controlled ventilation is what we need.

The adage, ‘build tight ventilate right’ is a very good one, unfortunately trickle vents although the intention was for them to help have turned out to be unhelpful, they cause draughts as highlighted above, do not ventilate right and it will take a lot of work to rectify the situation. Sadly this is a repeat of the same mistake made in the fifties with compulsory through the wall vents in all bedrooms in new homes, DraughtBusters expend a lot of effort blocking those ones up even two generations after they were installed.

The next generation of DraughtBusters will need to spend even more time sorting out leaking trickle ventilators in windows.

How to prep for MVHR installation retrofit

oliviaaa99 — Thu, 05 Mar 2026 16:48:47 +0000

Hello! We are preparing to self-install (or contract out) a MVHR retrofit in the cold loft of our bungalow, but we have a few questions for the prep stage!

Quite a lot of our electrics are in the loft& attached to the current boards. These will be removed for insulating, so we aim to attach the cables to the floor joist sides instead.

Should the order of layers go:
1) membrane > insulation up to joist level > layer of ducting with insulation around it above joists > loft boards

2) insulation up to joist level > membrane across joists > layer of ducting with insulation around it > loft boards

3) ducting with insulation around within and above joists where necessary > membrane above joists and ducting ( > potentially a layer of insulation above joists and ducting so the membrane is on the warm side?) > loft boards

4) something else? We’re open to any alternative ways as we’re not sure which is correct!

We are also not sure if we need an intelligent membrane, VCL or just airtight? For reference, the joist depth is appx 8cm and the roof is ventilated at the eaves. The floor was sealed with VCL over the subfloor but under a plywood base, and the house has been replastered/painted (still some new cracks though!).

Thank you!

Panelvent versus OSB

Triassic — Fri, 26 Sep 2014 09:05:00 +0100

The structural engineer has specified 9.5mm Panelvent, rather than 9mm OSB, as the sheathing for our timber frame. What is Panelvent and what is it's advantage over OSB?

I realise Panelvent is more permeable than OSB and this is to aid moisture movement, but I'm left wondering what part the external breather membrane plays and is it necessary?

Why have a high permeability board covered with a low permeability fabric?