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.

CAT6 install

Rex — Wed, 26 Aug 2026 13:32:37 +0100

What ho one and all,
Thought I had a separate CAT6 thread but only topics relating to my attempts, namely toilet seat and plasterboard.

Knowing that y'all are sitting on the edge of your seats, after a lot of procrastination and alternative plans, plus attempting limited demolition (Right said Fred, gotta take the wall down!), persistence has paid off and yesterday, I found the fish rod end and have finally have the CAT6 cable form the loft (second floor), horizontally through the Posi-joist / Warmcell floor/ceiling and into the wardrobe. From there , it will be a simple vertical drop to where I will install the CAT6 socket.

Don't recall any job where I have been so persistent in my efforts.

I won't make good until the fibre to the house is installed and I know the CAT6 is working; then a simple decoration job.

I did not remove the toilet but did remove the small cabinet beside the toilet which allowed me to bore another 100mm hole into the 22mm OSB to get a better angle.

Appreciate all the advice and suggestions.

Wall Build-up for timber frame structure validation

Oj0001 — Tue, 25 Aug 2026 14:38:05 +0100

Hey,

I’m currently in the progress of building a single story extension on the rear of my house, located in the midlands.

For the extension I drew up and got approved plans for a timber frame structure. The wall build up from inside to outside is currently:

15mm plasterboard
145mm studs with 100 PIR. (Resulting service space to inside, all joints tapped for Vapor sealing)
11mm OSB
Vapour barrier
70mm EPS with direct render.

However, since then I have read more into interstitial condensation, and under winter conditions there is a risk at the outside face of the PIR could suffer, this is behind the OSB and could lead to issues. Also the OSB becomes sandwiched between two layers, although EPS should have some permeability.

So far I’ve looked at :

-Increasing the PIR to 140mm and adding an internal service void does not seem to resolve it.

-Switch to 140mm Rockwool between studs. (Decreased performance notably, but increase breathability). Still need to add internal service void as internal vapour layer needed.

-Switch to internal PIR layer, add external ventilated cavity and render board. Also considered external PIR to reduce thickness, then cavity and render board.

Really just looking for a sanity check, is there a fundamental issue with the project as designed, is there a way to add improvements, or does anyone have experience with similar?

There’s a lot of discussion on similar build ups on here, but nothing quite the same.
Any and all help is appreciated!

Broadband and VoIP

Rex — Sat, 04 Jul 2026 14:48:15 +0100

What ho one and all,

Frequently happening as I get older, I am getting my knickers in a twist as technology leaves me behind.
At the moment, broadband and landline is with PlusNet via fibre to the pole. We are not paying for the landline, but it does receive incoming and we would pay per minute for outgoing calls.

My contract is ending but PlusNet are no longer offer a landline, just Full Fibre b/b. However, their associate company EE, will offer full fibre to the house and I assume, VoIP to keep the phone and phone number.

I am told that an engineer will have to assess how to get the fibre to, and then, into the house. At the moment, it is overhead to the front roof apex, then phone cable to the various RJ45 sockets which was part of the building process. The ''customer help' was not exactly helpful with my questions, but ......

Fibre has to come to the router which if it was in the loft, can I then use the existing wiring to the computers on the g/f?

The 'unhelpful' assistant was suggesting the fibre will have to be routed down the wall then drilled through the wall to where the office is located. The house is timber frame with Warmcel insulation. There is the breather paper on the frame (but that is inside the cavity) and internally, there is scrim under the Fermacel. Drilling through either of these materials is like drilling into a ball of wool; it just rips everything to shreds.

How does a fibre cable come into a very well sealed house if it has to be drilled through the frame and insulation? Once inside the house, can I use the existing wiring to use additional computers in different rooms?

Thanks and toodle pip

Garden Slab - Future Planning

Doubting_Thomas — Tue, 25 Aug 2026 16:01:56 +0100

I have an area behind the house, 2.5m x 6.5m, where I plan to put various outdoor storage: bike shed, composter, raised beds, possibly IBC rainwater tank (inspired by another thread). Eventually it could even become the floor of an outdoor 'garden room' of some kind.

It feels sensible to pour a level hard standing here as a base for all of the above. My current thought is a concrete raft slab of 100-150mm thickness would be more than enough support, but I'm open to suggestions on this.

Three sides are enclosed by ~2m high concrete retaining walls supporting neighbour's gardens, so formwork along the remaining edge should be straightforward.

My questions are:

- Should I insulate and/or damp proof below it, anticipating the potential ultimate use as an outdoor room? Or are these generally raised up on pedestals anyway?

- Will I need reinforcement and or movement/expansion joints in this footprint?

- Anything missing? Ducting for electrics perhaps?

I realise this could spiral into a full-on house slab if I'm not careful, and I'm keen to keep things simple and affordable. More likely than not it will remain a concrete extension of the patio for many years - I just don't want to miss an opportunity for some future-proofing.

NB - I can't dig down much deeper for the risk of upsetting the retaining walls, so underground nuclear bunkers aren't going to happen!

IBC rainwater storage

Rex — Fri, 07 Aug 2026 15:32:33 +0100

What ho one and all,

Have a 6000 liter rainwater collection tank in the garden (mainly for toilet flushing but also garden use) and it has of course, been empty for the past two months.

Wish I had installed an even larger tank but 15 years ago, who could predict this extended drought.

So at the behest of SWMBO, I am investigating most likely, one (or perhaps two) IBC and how to fill. Obviously, the best location is somewhere that I can divert rainwater but the design of the house is such that the only place would be against a side wall and these are somewhat ugly things.

Since the loft tank (for flushing) is filled by a submersible timer pump, I could access the pipe and T off to an IBC situated in a less obnoxious location. But is it possible to install a ball valve in an IBC so that when fill, it does not overflow?

I have not researched this idea but thoughts would be welcome.

Making good a cracked footpath

thebeacon — Thu, 20 Aug 2026 11:33:40 +0100

Hello,

I’m seeking some advice on making good the pathway at the front of my house. Its currently a 50-100mm slab of concrete which has some cracks and a drain in. The water currently runs towards and pools in front of the door.

I would like to repair the footpath and add a slight ramping in front of the door to direct the water to run away from the house. The entire path is about 2.6 x 1.3m. I imagine some areas would need 40mm while others less than 10mm.

I’d rather not break out the entire slab and add a resin based concrete product on top. Does anyone have any experience or advice with doing this? I have been looking at Cretex® EP Mortar (https://polycote.com/contact/) as a possible option to use.

Thanks,
Tom

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?

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?

Water prices

Rex — Sun, 16 Aug 2026 17:16:07 +0100

What ho one and all,

The headline on the front of today's Telegraph is what can only be described as 'surge pricing' for water during droughts. The aim is to encourage us to use less water.

This really anger me as we have a 6k liter rainwater collection tank and apart fro the fact that I'm not paying for incoming and by default, sewerage charges for using that water, I am unlikely to get any consideration for the fact that I am using less treated water than most houses.

With all the building regs we have in place, surely it makes sense that every new build, whether single houses or estates, must have a large rainwater collection to be used for toilet flushing. After all, every new build has to have a large soak-away, so why not collect that water before it goes to the soak-away?

It is absolute madness to flush expensively treated, potable water down the lavatory.

Now I'm off my soapbox!!

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.

diseased or rotten oak in external application

northumbrian — Tue, 16 Sep 2014 20:27:21 +0100

Six years ago we installed some oak sleepers in soldier format for a client. We import the oak 400 sleepers at a time and use it for many varied external applications. We concreted the sleepers into the ground and told the client there was no great need for a treatment and that they would weather naturally and last a long time.
The client decided to treat the sleepers in a black treatment(variety not known at this time), and now is complaining that some have rotted.
ALL the other applications we used the same sleepers for are absolutely fine.

Can anyone shed any light on why this rot may have occurred in a relatively short period. Could it be something in the soil which surrounds their feet?
Could it be moisture that has been trapped in by a non breathable treatment?
Any suggestions would be welcomed as we have used green oak for years without a problem

Thanks in advance

Acoustic insulation between floors in old house

reed — Mon, 03 Aug 2026 18:19:19 +0100

I am looking for advice for acoustically insulating a 280mm void between ground floor and first floor. I have installed internal timber stud walls with mineral wool slab insulation on the external walls of my late Victorian house, I have insulated the suspended floor downstairs and I will insulate the loft space in the bedroom above. I have lifted the floorboards with a view to sanding them and relaying them in both bedroom and lounge with no carpet above. The old ceilings are down and I have not yet installed new ceilings. I need to reduce the drum effect which will exist if I do not install some sort of acoustic insulation between the floors. I would prefer not filling the whole enormous 280mm void with insulation for cost reasons and also I am not averse to leaking some heat from the lounge (woodburner heated) to the bedroom above. Am looking at various solutions but would happily receive comments on:
1. layer of insulation slab (Knauf RS45) next to plasterboard ceiling of lounge. Void above to the floor boards of the bedroom. What thickness slab? will the void above slab be a significant acoustic issue?
2. thicker layer of rolls of acoustic or loft insulation. Should be cheaper but I presume less effective? What thickness?
3. combination of solutions 1 and 2 but it seems a bit labour intensive and costly.
4. Decouple the ceiling by laying battens on the lower side of the joists before fixing plasterboard. How much impact does decoupling have? Not my preferred option due to limited height between the ceiling and the top of my windows

Many thanks

Toilet Seals

Rex — Tue, 21 Jul 2026 19:02:37 +0100

What ho one and all,

In my continuing quest to find a way to thread a CAT6 cable from the loft to the office, it may (only may?) be useful to remove the toilet to allow better access to the small area of floor below the pipe.

Not a big job, just a couple of screws and wiggle it free from the fittings. Of course, I would have ensured the cistern is empty.

But the toilet has been in place for around 15 years and I am wondering if the various seals should be replaced when re-installing, or are they all OK to reuse? Of particular concern would be the two yellow seals, which I assume are not replaceable. I would give a smear of silicone grease around the seal before reinstalling.

Your thoughts most gratefully taken on board.

Thanks

Replacing wind turbines

tony — Wed, 29 Jul 2026 16:49:47 +0100

I recently read about a scheme to replace wind farm turbines with new ones. Their idea was to remove the existing ones and put new ones up, much bigger ones. It might seem like a good idea because because all the cabling infrastructure will already be there but of course it won’t be suitable because the the output of the new wind turbines will probably be something like 10 times as much as as existing ones so the cables would need to be upgraded anyway.

My intention is that it’s crazy to take down in turbines that still useful. Why not? Just put the new ones up somewhere else then we’d have both the old ones and the new ones all functioning?

Shower

Rex — Wed, 29 Jul 2026 13:53:50 +0100

What ho one and all,

Me again!!!

I frequently feel that design somehow does not improve the function, and this is exactly the case.

As in the two photos below, I have one of these bath tap shower fittings. In the lower photo, push the right thing and it switches from bath filling to shower. But!!!!

Frequently, either this does not happen or if it does, the design malfunctions and upon turning the water off, it will not revert to bath or most frequently, supplies both shower and bath at the same time.

The left spring sits in a recess in the body of the tap, so should all be locked in place. Disassembly usually shows one of two things: 1/ The spring has somehow, become dislodged or 2/ one of the O rings has been forced by water pressure from its seat. The water is running at 3 bar because that is the recommended pressure for the softener.

How to resolve the all to frequent dismantling beats me. It happens pretty much every couple of months. I have investigated replacing the tap unit, but want the same, which of course is either no longer available or is surplus stock for around a very profitable £250.

Having dismantled, reset whatever is unset, reassembled, it will work as it should for a few months, then the cycle repeats itself.

Grateful for any insight into how to ensure the push button works every time as it should.

Thanks and toodle pip

Old window

tony — Thu, 30 Jul 2026 16:47:39 +0100

Just saw a window over 350 years old - yea it was a wooden window frame set into a stone surround.

https://share.icloud.com/photos/053drZp42Ur_dTRWMN-hRQb8w

Hope the link works

Aerogel insulation

Sandfordbarn — Mon, 26 Sep 2022 08:21:13 +0100

Hi, I'm refurbishing a stone barn, and am looking at aerogel.

Does anyone have any experience applying it directly to stone walls, in particular the blanket rather than the boards. Then direct plaster/lime over that?

I'm keen on this finish as I'd prefer a more irregular finish, rather than flat boards.

I've seen some European company are applying aerogel render externally (with aerogel granules in the render mix), but I've not heard back from any of them.

Any shared experiences on this would be very helpful - it seems to be a revolutionary product?

Hole in plasterboard

Rex — Mon, 27 Jul 2026 07:25:39 +0100

What ho one and all,

Continuing with a different topic but still related to my CAT6 cable saga, I think I am planning to cut at least one hole, and maybe two 10 cms holes into the plasterboard ceiling.

My wife wiggled the fish rod (oven sized earth wire) and I can clearly hear that it is kinda where I want it, but nevertheless, still around 10 cms+ away from where I can grab hold. The option is to drill an access hole ito the plasterboard ceiling, behind which is the Warmcel!!!

On the destination side, it is not a major issue as we have emptied the wardrobe and the dust can fall onto the shelf. But the office side (which is where the wire is at the moment, has all the office equipment below.

Apart from removing, disconnecting everything, dust sheets, etc, is there a way to drill a hole in plasterboard that does not send dust everywhere? I've seen vids on a small, drill-bit hole but not 10cms. Of course, I would use a vac but that is challenging with 10 cms. Perhaps a padsaw?

Your thoughts appreciated.

Thanks

Rex

Wallpaper onto lime plaster

WillInAberdeen — Tue, 28 Jul 2026 11:17:41 +0100

How soon can you wallpaper onto fresh lime plaster, does it need specific wallpaper paste, anything I should know about it?

I put breathable wood-fibre IWI with Lime Green Solo plaster on the external stone wall of a room, and want to hang plain lining paper (no vinyl) to match the existing finish on the other internal walls. I will paint the lining paper with some breathable paint, probably Earthborn.

Lime Green say they don't recommend wallpapering their plaster but didn't explain why.

ISTM that lime plaster walls have traditionally been wallpapered for 100s of years including in my house, so not sure what the issues might come up?

Home Energy Model

djh — Fri, 15 Dec 2023 09:32:39 +0000

Will in Aberdeen spotted the Home Energy Model initiative: https://www.gov.uk/government/consultations/home-energy-model-replacement-for-the-standard-assessment-procedure-sap but can't start an appropriate thread. So here is one.

Oak Frame, Oak Sarking, Roof Insulation

DrewWiley — Thu, 23 Jul 2026 18:04:13 +0100

I have been building an Oak framed out building for a number of years for use all year round, it is 10mx5m. It will have a heated floor.

On the inside Its open oak rafters, then oak square edge sarking with 3mm spacing using random sized boards. I dont want any insulation on the inside of the building as it looks lovely inside.

Externally i dont want any soffits or fascias just open rafters and perlin ends.

My dilema is insulating the roof, my initial thought is as follows

the sarking is pretty flat however not perfectly flat.

Rafters are 80mm so on top of the sarking lay a vapour membrane (i need to this to be black as i will see it through the sarking gaps inside) ill then screw using stainless spax washer heads a 80mm wide, 50mm deep oak battens on top of the rafters (externally). i will then use kingspan 50mm k107 in between each of these new battens (from the ridge to the end of roof). then my normal roofing approach counter batten with draping roofshield followed by pantiles. Would this be a suitable approach?

I would need to use an oak batten running the length of the roof that is 50mm tall to stop the insulation sliding down and providing a more decorative finish.

This all sounds like a mix between warm and cold.

Any suggestions would be welcome, i did look into TLX Gold etc but wasn't keen.

Or do i simply use something like Solitex Fronta Quattro, then PIR, then counter battens then tiles.

Thanks

Is Hinkley C dead?

SteamyTea — Mon, 07 Mar 2016 18:10:53 +0000

What do people think?

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?

Roof ventilation and summer overheating

wholaa — Fri, 17 Jul 2026 19:42:58 +0100

With the recent hot spell across much of Europe, overheating in homes is back in the headlines. As expected, there's plenty of discussion about air conditioning and the trend towards very large south facing windows, but much less attention seems to be paid to roof ventilation.

I'm not a builder or roofer, so this is a genuine question rather than a statement. It seems to me that relatively few homes have the recommended level of ridge ventilation. Perhaps I'm simply not noticing the more discreet ridge vent systems, but ridge ventilation appears to be much less common than soffit ventilation.

In room in roof houses, particularly where rigid insulation has been poorly installed, could inadequate roof ventilation, especially a lack of ridge ventilation (lacking the stack feect), be a significant contributor to overheating? I'd be interested to hear the views of those with experience in roofing or building physics.

GivEnergy equipment

marsaday — Thu, 16 Jul 2026 12:22:41 +0100

My 4 yo inverter has possibly died. It is not covered by any warranty as GE went bust earlier this year.

I have spoken to the installer and they are looking into my options. They can supply a new inverter I think.

I am pretty poor on understanding the electrics, so if anyone can help me out that will be appreciated.

I think my inverter has failed because I signed up to Axle energy to sell some of my surplus energy. They took control of the inverter on 7th July and I know for a fact the inverter was down from 11th July and has been ever since. I should have checked everything was ok aster the first control event by Axle energy, but I didn't.

Is it likely Axle energy have caused by inverter to die or is it coincidence ?

Eco-friendly Shower tray & enclosure ie low embodied carbon

stonecold — Tue, 14 Jul 2026 20:36:57 +0100

Any suggestions for something with low embodied carbon, or if there is even some line of certification to look for when searching?

I would rather avoid a plastic shower tray unless it's 99+% recycled. Steel is very high embodied energy.

What do all those Carbon Lite home fit? Where do I even start?

Solar irradiance

djh — Mon, 03 Feb 2020 17:30:32 +0000

Does anybody know of a source of solar irradiance data?

Specifically broken into fairly small areas?

I'm trying to forecast how much heat my house needs each day. Apart from the internal and external temperatures, I think the other major factor is solar gain. So I'd like to get hold of records of irradiance over the past year or more and also a 24-hour forecast of irradiance (or longer :)

Historical data I can estimate from my solar generation records but it would be good to have an external source to compare against, and a forecast is the most important bit.

Best Apps for Energy use & PV export monitoring

jms452 — Tue, 06 Jul 2021 11:47:21 +0100

Having recently had a smart meter fitted there are apps out there that can tie into your meter giving you accurate half hourly monitoring without additional hardware.

For example I found an app called Octopus Compare that I can code to my smart meter and look at what different tariffs would cost me. I can also see from the Octopus dashboard my usage and export in half hourly blocks so this data should also be available with the right logins.

So there must be some cool apps out there that monitor, advise, correlate but when I search I'm mainly finding proprietary software that talks to specific brand inverters.

Any recommendations?

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?

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.

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:

(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.

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

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