Nick Laslett

There are a lot of extensive papers on testing ICF. The two I have read are specifically regarding windows. Did also read a few sound test papers. https://www.bchousing.org/sites/default/files/rcg-documents/2022-04/ICF-Wall-Test-Modeling-Lab-Report.pdf https://www2.bchousing.org/sites/default/files/rcg-documents/2022-04/ICF-Field-Test-Report.pdf Looking at the Amvic manual it recommends a membrane behind timber cladding. The Thermohouse manual says to do what the cladding supplier recommends. The Nudura manual defers to building regulations and manufacturers requirements. These are the 3 ICF manuals I have on hand. NHBC doesn’t require a membrane behind cladding. https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/6.1/external-finishes-to-insulated-concrete-formwork.pdf

ICF in the UK doesn’t really need membranes and trays or to be treated like timber frame. But you do need a water shedding strategy with render, cladding, brick or some other facade. The concrete is your water proof layer. You could scrape all the eps off, if you didn’t care about the insulation and the concrete would behave like any concrete structure and give you decades of water proof, rot free performance. ICF is nothing like timber frame, and should not be treated in a similar way. If it wasn’t for the UV in sunlight slowly eroding the EPS, you could leave the bare EPS walls uncovered for many, many years and not see any degradation. EPS is not a new material, there are decades of evidence showing how it performs. ICF is not a new build method and has been around for over 50 years. Watch some Building Science videos with Joe Lstiburek, where he describes the “perfect wall” and what you need to do to prevent water ingress, this starts a the 30 minute mark, but the whole video is worth watching. Every building needs a good strategy for shedding water as this is one of the most damaging environmental effects. https://buildingscience.com/documents/enclosures-that-work/high-r-value-wall-assemblies/high-r-wall-icf-wall-construction

Fit a TMV mixing valve after the UVC so all hot water is pre-mixed with cold to 43°C or whatever the requirements. I think it might be part of the standard UVC schematic, I could be wrong.

@Mulberry View, please ignore this comment if appropriate, because I really have no idea about a lot of this stuff. I was talking with someone the other day and they said a block wall had poor acoustics. How poor is poor and compared to what, I ask myself. Anyway, I know you are detailed oriented, so hate to add another parameter to consider, if this is a red herring. I’m sure others will know more. Wall acoustics is such a can of worms.

I have a Zehnder ComfoAir Q600. Looking at the design spec for my install the supply air (240m­³/hr =67l/s). I went with the Zehnder ComfoWell filter housing, CW-F 625. https://www.zehnder.co.uk/en/productsceletons/zehnder-comfowell-filter-box/zehnder-comfowell-filter-housing-cw-f-625 Due to space constraints in my install, I have the filter on the intake before the MVHR unit. The filter is designed to be fitted on the supply pipe after the attenuator and before the manifold.

My MVHR is still not commissioned. But I’m always amazed that this topic doesn’t generate more discussion. Of course circumstances differ, but I’m in the countryside with 2 neighbours that have log burners going all winter. I went with the Zehnder comfowell filter box because it will be easy to get hold of the filters over the long term. You will need to size the filter box to your system requirements.

@Post and beam, yes we have 2 George Barnsdale doors. Very happy with them. The U-values were not very good, just scraping under minimum requirement for BR. Not sure if their window frames can achieve a better U-value now. Bought them in 2021, installed in 2022. The installer just fitted them with expanding foam. We put airtightness tape over the joint. Visit your nearest installer to see the product.

My wife and I did our window installations ourselves using some Illbruck products. We used TP651 Trio expanding tape, which is 35mm depth on 47mm depth window frames. We used the FM330 Pro Foam Air Seal expanding foam to fill the gap left behind the tape. I really rate the FM330 expanding foam. We then used Siga Fentrim IS20 airtightness tape, 10mm on the window frame, connecting across the foam to the ICF EPS reveal. Siga are one of the few airtightness brands that explicitly state their tape will bond with EPS. This was probably overkill, but we wanted to be sure that the windows were airtight. The Thermohouse ICF window blocks have a “Check Reveal”, which means the edge of the window frame is protected by 100mm of EPS. This is another layer of insulation and weather protection. Our renderer then fitted on the outside of the frame a window reveal bead, with a rubber seal. https://ewistore.co.uk/shop/external-wall-insulation/anthracite-window-reveal-bead-with-mesh/ I doubt any of this additional work will be reflected in our SAP score, but I am pretty confident that we have detailed the junction between the window frame and the rough opening in a way to provide us with a lot of long term benefits.

@Mulberry View, you have my sympathies. I have also been very cautious with the use of contractors. Unfortunately unless you watch them like a hawk and actually know how to do the job yourself, it is always fraught. My wife and I joke that this is our perfectly, imperfect house. I only recently realised that the contractor that installed our ground floor UFH, only fitted 75% of the designed piping. This throws off all my heat loss calcs and means the ASHP will have to run at a higher temp. Unfortunately the damage was done a long time ago and there is nothing that can rectify it. I’m sure we will survive. Good luck getting a decent resolution.

Maybe I’m being hugely naive, but as I have designed and installed my MVHR gear, I was not expecting noise to be much of an issue. I fitted 600mm Lindab box silencers on the house supply and extract sides, I would have liked to have used the 1m models, but did not have the room. I asked Paul Heat Recover if the ComfoPost had any sound attenuating properties, they said it didn’t, but basic physics tells me that it must have some effect, whether positive or negative because the air path is changed. I went with the semi-flexible ducts from a manifold, as this was meant to be better for sound transmission between rooms. The anecdotal evidence based on the BuildHub community back into 2019, when I was specifying all this stuff, was that MVHRs pushed the air at such a low rate, that noise would not be a problem. How noisy is my unit going to be? I’m still ages away from commissioning the unit, although I could run it without the plenums just to get a general feel. Building work is still going on upstairs. Anyway I will report back on this post at some future date, with any tales of woe and regrets.

Beware USA centric building information. It can be really useful, but things like Building Regs, BBA certificates, NHBC and manufacturer materials will cover the requirements in the UK. You can of course do whatever you want if building controls will sign it off. Lots of videos about ICF in USA because it is more popular there, if you research deep enough you will find in some regions ICF has a problem with termites and needs special treatment in those regions. @Russell griffiths who has an ICF Nudura build recently posted about render coating ICF here.

I have just had this recommended to me. Just C02, temp and humidity, not particulates. A bit pricey at €169 euros. https://aranet.com/en/pro/products/aranet4-home I believe it integrates with Home Assistant. They have a separate PM sensor. I probably don’t need it, I would use it for C02. But do find these kind of measurements interesting.

Should I be worried about this? I assume this is for 60°C water? I’m using Hep20 for my ASHP from the insulated Pex to the UFH manifold. Not sure if I’m using the calculator correctly, but just wanted to record somewhere the max flow rate for 1.3 m/s velocity. I believe my ASHP is running at 14 l/min.

I’m sure others much better informed that I will be along soon. My build is also off main drainage. My architect arranged a specialist to do our drainage and rainwater designs. We have our sewage treatment plant feeding into a drainage field. Lots of building regs about the design and requirements of drainage fields. Maybe having it feed into a rainwater soak away is okay, but my memory tells me to check the specific BR part H Drainage and Waste Disposal.

@JohnnyB always a mystery why some topics get lots of replies and others are ignored. It doesn’t help that the forum has a dedicated ASHP section, which is separate from the Plumbing/Heating section. It is great that you have posted a detailed quote and others I’m sure will find it very useful. To me the quote looks fine. As @Bozza already mentioned, maybe £1698 for “general plumbing materials” is a bit high. The pricing of most of the kit looks reasonable. You might not need the Buffer Tank, depends on the volume requirements of the ASHP and how much UFH piping you have. I didn't go with Anti-freeze values and that is its own topic, but @sharpener is right, you will need a pair. The quote doesn’t include groundworks, but getting the ASHP as level as possible on solid surface will pay dividends over the long term. If you are going down the UVC route, you should take a look at the OSO brand. @TerryE, just had one fitted. For the extra cost you get a cylinder which is insulated with Vacuum Insulated Panels, which greatly reduces the heat loss. If space is an issue HeatGeeks have recently launched a very compact UVC especially for ASHPs, which comes in many formats, even one the size of a kitchen cupboard. https://forum.buildhub.org.uk/topic/39202-mini-store-heat-geek-newark-cylinders-for-ashp/ @Dam0 just started an ASHP design thread today, I sure that is an interesting read. It is often a case of deja vu with some questions as they come up so frequently. @TheMitchells had a thread back in July about his ASHP quote.

I previously collected a few good threads on this topic in the thread linked below. There is a HeatGeek video on YouTube about pipe diameter, I believe a higher flow rate/lower temp requires larger diameter. For the insulation question the length of pipe will be the biggest factor.

@JohnnyB, I have some left over rolls of compriband, various expansion thickness if you want some to experiment with. TP651 https://www.illbruck.com/en-gb/products-systems/product-finder/tp651-trio/

I just watched this video which tries to explain the relationship between cycling, volume of water, ASHP power and modulation. I like the guy, but he doesn’t do the greatest job of explaining the topic. You can see that balancing all these factors does require some insight and number crunching. More UFH pipe increases the volume in the system. The modulation data for a lot of ASHP can be hard to find or difficult to compare. Rule of thumb appears to be 30%. Excessive cycling can be an issue if your ASHP is massively over powered for your heating needs. Sometimes they will spec a more powerful ASHP to speed up the UVC reheat time. My take away from when I first read up on this topic was that excessive cycling will drastically shorten the life span of your ASHP, but this might be misleading information. John Cantor has a good video about ASHP cycling.

@Crispy75, my MVHR is not commissioned yet. I would be somewhat hesitate at this stage to recommend the ComfoPost without these caveats. There are other members like @Dan F with more experience, with good comments in other threads. I won’t be running the water in my ASHP in cooling mode any lower than 13°C. My aspiration is to knock 1° to 1.5°c off the house temp with the ComfoPost. Looking at the design spec for my install the supply air (240m­³/hr =67l/s). Hope that helps.

oops, double post

It looks fine to me. The “average wall U value = 0.33” is calculated and includes the windows. I take it you are planning to have a better air tightness than 1 air change per hour? Target should be 0.6, but anything below 1 is good. You will need a blower door test to get actuals for this. If you change this number you will see how big an effect, air tightness has on the heat loss. I also take it that you have got the mean minimum monthly temps from the MET office from your nearest weather station?

My advice would be to pay a tradesman if you can. I found it a very nasty job cleaning up a steel beam with an angle grinder. The rust gets everywhere, you need a full face visor. I used these grinding pads, they did an amazing job and were very quick. https://www.amazon.co.uk/Stripping-Remover-Oxidation-Abrasive-Grinding/dp/B098BHYZZ5/ref=sr_1_1_sspa?crid=2PP5S0KHREEFA&dib=eyJ2IjoiMSJ9.-RiUzUPMM0xDSoj_ao0kyzCEkq06Ki9_tKwgAzUzzGgX0w9E79tHP9RGLHAZ1uvD6v4vAAxkOKU6EGAIZZPMcvZ671hrmCKe2R6Tt7GZoB69DpVG1u726XRYtt00LEgJLT0HQPuTJyAz5KFmiO3G46nG7BCaR5hFBVumshPhIn5gaZt4E5aSzxJJLeX3p4bPE-_uKnof6GWenJfVRmlP7I0bfM6W6TT9qNV7A-b0lzxrg3EyRxCQdPaIfmCTWNYaapLHh_bgqAPpLorSF6pTcAg1RtEdnc5IGTeUrhOdDzM.ZZ4qAg_eV6JXNLQLgrNZx0vRPf5X8GVjbarfh9fhWWc&dib_tag=se&keywords=poly%2Bstrip%2Bdisc&qid=1725208867&sprefix=Poly%2Bstr%2Caps%2C94&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

I am going with traditional skirting boards. Never considered a shadow gap, it would also not suit the house style. You could create rounded edges with a router bit. Never considered leaving the Fermacell without corner beads. Although the boards are strong, I would still worry about the long term wear and tear at corners.

As a complete novice, what I liked about the passive slab, was how simple it was to execute and understand. The EPS tub created a continuous insulation layer you could see. No cold bridges, and no extra steps. The power floated concrete gave you a finished floor, which needs no additional work, no screed no additional moisture being pumped into your build. I went with fermacell for the same reason, no wet skim adding moisture to the build. The simplicity of putting the UFH in a large piece of concrete with a lot of mass and the ability to hold a lot of heat. This suits the ASHP for heating and cooling. I had ICF on top of my slab, so this was even more simple, the continuous insulation layer around the whole house could be inspected and easily understood. I realise these options aren't for everyone and not applicable in a lot of builds. But don't underestimate the value of simplicity, even if it costs more.

My tape and jointer guys used aluminium corner beads. He stapled them onto the fermacell, then used joint filler to create the corner and hide the beads. He used the joint filler over all of the staples/screws and over the jointstick where the boards meet. We did all the boarding ourselves and followed the Fermacell installation instructions to our best abilities. After the joint filler and FST was applied all the boards were lightly sanded. Here are some pictures: 1. Ceiling showing stapled aluminium corner beads, with joint filler and FST 2. Wall showing joint filler to cover joints and staples with the rest of board covered in FST. 3. Corner bead 1. 4. Corner bead 2. 5. Raw fermacell boards, showing routed corner and fermacell jointstick for the board joints. 6. Corner beads before joint filler and FST. Just the screws and joints have been joint filled.