Nick Laslett

I am away this weekend, but happy to post pics of various edge finishes, just board, aluminum bead, paper bead. I did the corner bead and FST for our plant room. I had a tape & jointer do the FST for the rest of the house. Applying the FST and joint filler to finish fermacell boards is very straight forward. It is just hard work. https://www.belmoretools.co.uk/levelline-drywall-corner-tape-2-75-in-x-100-ft-roll.html

The Heat Geek tool is also free to use. No idea what it is like. https://heatpunk.co.uk

Mine are 40°. They are too steep for my liking. They’ve been in place since November 2022, so I’ve had plenty of opportunity to use them whilst working on the house. If you can I would definitely have a shallower angle. One of the hard to get right decisions, which are hard to undo. We have a poured concrete staircase.

Just for a laugh, as I’m currently on a train journey, I went and had a look at the only quote I got back in June 2020 for a heating systems install. This was via a recommendation from my Architect. The good news is the RHI which was running at the time had a payback of £11,000 over 7 years. The full quote included installation of ASHP, UFH, UVC, MVHR and ducting. Total price £41,601 ex VAT. (I know this is zero rate for new builds) This is from the quote, in the RHI section. I sent them a SAP, not an EPC, so I think they’ve just made up these numbers for the RHI grant. Here are some individual line item values: Please remember these are from 2020. 1. Nibe F2040 16kW ASHP = £6784.11 (I fitted a 5kW Panasonic based on my heat loss calculation using J Harris spreadsheet and the LoopCAD UFH software.) 2. Buffer Tank = £556.80 (with the Panasonic there is enough volume in the UFH loops, no need for a buffer tank.) 3. Nibe Megacoil 300l UVC = £1635.47 4. ASHP Circulation pump = £373.87 (I think this is needed due to the buffer tank. ) 5. UFH - design, materials and installation = £9030.00 (This was being subcontracted. Their quote listed materials, but not individual item prices. They had a 4 manifold design, I went with 2.) 6. Zehnder CAQ450 = £4246.00. (I actually went with the Q600, when I did the volume calculations the Q450 wasn’t big enough. The Q600 with enthalpy exchanger cost me £3,785.8.) 7. MVHR ducting, manifolds, plenums, etc = £4895.00 8. Installation costs for MVHR, ASHP & UVC = £5650.00 9. Zehnder ComfoPost = £2450.00. (I didn’t remember that they quoted for the ComfoPost. Some people on here give me a hard time for spending £950 on the ComfoPost I installed myself.) I’m confident that I spent less than this including the RHI deduction, but a lot depends on how you value your own time. For the ground floor UFH, the pipe install was included in the price for the insulated raft foundation.

This was the key change for me. My memory of the research I was doing in back 2019, was that the RHI government grant at that time, did not allow an ASHP to be installed with cooling enabled. There was some confusion on the BuildHub site from other members what the MCS would allow and many heat pumps, just did not actually have cooling capability at all. I only decided to go with a Panasonic AShP, because fellow member @jack had one and he had enabled the cooling mode. I can’t remember if it was @Josh or another member that imported their Panasonic fan coils from Italy.

@JohnMo, I only got it for the cooling, we have solar, so expecting that to cover the energy costs. System not yet commissioned, but my expectation is for it to knock 1°c degree off the internal house temps, if it achieves that I will be very happy. Currently only have the ASHP commissioned, in the recent August heat wave we had down south, we had 2 days of 30°c weather. The house temp upstairs reached 23°c. The bedrooms are in the roof, there is no attic. The ASHP cooling is just running on weather compensation, I think I set the lowest water temp at 13°c. Also, we have not moved in yet, so I don’t feel comfortable having the windows fully open when we are not there. In the design stages, I discounted installing AC, and went with alternative cooling strategies. The Fancoil approach had not matured on BuildHub at that point in 2019, with very few members having installed it. I have nothing against Fancoils and think it is a good solution. But my wife is anti having radiators outside of bathrooms, so not something I could easily retro fit if I wanted to satisfy that criteria. I was originally going to install the Zehnder ComfoCool Q600, which is about twice the price of the ComfoPost. In discussion with Paul Heat Recovery, they recommend the ComfoPost as being more effective. Zehnder actually replaced the ComfoCool with ComfoClime 36 during our build and the ComfoClime on top of the ComfoAir is too tall to fit in our plant room.

There website is very good. Huge amount of useful material. I think about 50% of my MVHR install answers came from reading their blogs. Often their replies to people in the comments is equally as useful. They said enough positive stuff about the ComfoPost to swing my decision to install one.

Remember that you can open windows any time with an MVHR system. This just affects its efficiency. The main concern with an external venting cooker extract, is that it creates a permanent air leak in the system. I do not believe there is a significant air pressure balance issue with this, but, I could be mistaken in this point. Passive House & MVHR does not preclude an external cooker extract, it just needs to be factored into the system design. There are Passive House certified extract ducts with air tight seals. When I was researching MVHRs back in 2019, there was good evidence that an MVHR system was beneficial and cost positive even in a house with an air tightness above 1.0 ACH. The goal would still be to have very good air tightness and try to reach the PH 0.6 ACH figure. https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

Just to add to this as others might not know this, most ASHP will have a thermometer for the weather compensation, so you don’t necessarily need to have an additional weather station outside.

One of the cock-ups on my build. We have poured ICF walls, so I asked the builder to set the MVHR inlet/outlet 200mm steel spiral ducts in the wall prior to them pouring the concrete. This was near the top of the wall, the amount of concrete on top was not that great. I gave him 500mm lengths, with end caps to strengthen the ducts. I requested a 3° fall, he is Romanian, so something might have been lost in translation, he set to ducts at nearly 30°. I never checked the angle of the ducts. It wasn’t until after the concrete first floor had been poured, that I realised the angle was wrong. I wasn’t sure how big a problem this might be, but in the end I could not face rectifying this mistake. On the inside I had enough head room to fit a 30° bend to correct that angle. On the outside the external grill will be mounted on timber cladding, the plan is to fit a 15° bend to correct most of the angle but still leave it pointing slightly downwards.

The best thing about this site is seeing everyone's journey, but most builds do not go to plan. Everyone has their own level of involvement they are comfortable with, it can be frustrating that the "self build" label is such a broad term. I'm in my 50's and my wife and I have been doing as much of our build as we can. We started in 2021. I remember your build, because like you we used ICF, you also asked questions about Fermacell and I was also interested in using that product too. Without the community here, asking all their questions, I would never have made if through my build. It helps to have met a few members too. I visit the site most lunch times and enjoy catching up on people progress. We are still at least a year away from being complete. No one else can give you the right answer on how best to proceed, but perhaps visiting some other members and seeing their builds would help clarify your situation.

The article is not as clear as it needs to be, in another paragraph it states: I’m definitely in the 300+ region for hardness. They then go on the say: Which is good, but in layman’s terms how easy is it to measure micro siemens? Not sure where that was covered in the article? Found this guide on Google, which seems simple enough. https://sciencing.com/measure-conductivity-water-multimeter-8523350.html Found my local water report, the micro siemens before softening was 800. According to this website, softening water with ion exchange does not increase its conductivity. Not sure if this is true, but… https://www.heylneomeris.com/en/conductivity-measurement-water-hardness-measurement/ I was more alarmed by the “bug growth” statement. Is this a concern in a closed system?

John, I’m not sure what you mean? Admittedly I only watched a few YouTube’s on filling UFH loops. They just seemed to use the mains supply. Not sure if the output from the water softener is particularly salty. But the water here is very hard, so the lesser of 2 evils. For the ASHP, the choice seemed to be add antifreeze or antifreeze valves. My ASHP is only used for heating, DWH is a separate system, so temps should rarely hit 32°-34° in depths of winter.

Sorry, it means “Too Long, Didn’t Read”. I felt the primer needed a good summary, before getting into the details. I read the whole thing, but I felt some people will struggle to maintain their interest to the end. .

I just read the Heat Geek VDI explainer, I think it needs a TLDR section. I filled my UFH loops with water from my Harvey water softener. Not using any anti-freeze. A low temp ASHP based UFH system seems like it will suffer from very little corrosion. Not anticipating ever having to drain down the system and refill. All the pipework is barrier pipe, very little metal. Do the stainless steel manifolds corrode much or let air in?

Here is a good primer by Joe Lstiburek of Building Science Corp on vapour control and how modern “smart” vapour control layers like Intello work. https://buildingscience.com/documents/building-science-insights-newsletters/bsi-099-its-all-relative

The Weber specifier tool has 2 fire specs A2-s1,d0 reaction to fire, B-s1,d0 reaction to fire. Searching “ewi a1 fire rating”, seemed to bring up a lot of hits.

This is a real can of worms, but I would suggest that you are basically describing an External Wall Insulation (EWI) system. With EWI you move the cold layer further towards the outside of the house, reducing the condensation problem. https://ewipro.com/services/system-build-ups/mineral-wool-insulation-system-build-ups/#mineral-wool-timber-frame Weber have specifier tool for U0.15 wall. https://www.uk.weber/facades/selector

I was interested in the ComfoClime, but found I did not have enough space for the unit. I had a short discussion with Paul Heat Recovery and they felt the ComfoPost unit was better for cooling anyway. My MVHR is not commissioned, so not sure if the ComfoPost was worth the effort. Most discussion on here point to fan coils being a better cooling solution. The overheating issue, was a topic many Buildhub members discussed when I first joined the forum back in 2019. If you can, you need to design out as much overheating as possible with shading and smart window choices. We fitted the 70/30 suncool glass, which we are very happy with, there was no discernible degradation in the interior light quality. We also lent on the cooling capabilities of ASHP. We were already having a poured concrete 1st floor, so it made sense to fit UFH upstairs for cooling purposes. There are a few recent threads on this approach. Unfortunately this year, the weather has been so poor, it has been difficult to ascertain how effect the ASHP cooling will be. We nearly put in a roof window in the flat roof at the top of our house, where the ridge has been made flat to accommodate a planning height requirement, but ultimately I could not face the extra stress and complexity of getting it fitted. The objective with this would be to utilise the heat column/stack effect for some additional cooling. One small issue which @Jeremy Harris had, was his hot water solution leaking too much heat into the house. He went with a Sunamp in the end to address this issue. Oso do a very well insulated unvented cylinder. I guess the point I trying to make is that you can easily overlook the heat loss from the hot water system and it’s contribution to overheating a house.

Hello Geoff, I enjoyed your visit. Here are some good threads from when I was looking at this topic. Another product that might be of interest is OSB3 SmartPly from Medite, this has an airtight membrane already attached. https://mdfosb.com/en/products/smartply-airtight Forum top tip, you can tag someone to a post by using the @ symbol and their user name, e.g. @G and J, @Nick Laslett, this will then send them a notification. Not something to abuse, but when you are trying to get a specific subject matter expert it can be useful.

Fermacell powerpanel H20 is designed for this. But probably one of the most expensive solutions. https://www.saimaxx.com/fermacell-h20-powerpanel-12-5mm-x-2-6m-x-1-2m-square-edge-board-75054-115343.html https://www.insulationshop.co/image/catalog/pdf/Fermacell/product-data-sheet-fermacell-powerpanel-h2o.pdf https://www.youtube.com/embed/LpnG1d8hJL0 I used Marmox multiboard for shower area and then swapped to standard fermacell board for rest of the room, but all my walls are 2 layers anyway. Marmox do a nice pre-made niche for the shower area. https://www.marmox.co.uk/range/multiboard-products

@MortarThePoint I used the Wavin Osma AAV 4S306, which is A2 rated. However the 4S304 appears to be able to be installed below spillover level. https://www.wolseley.co.uk/wcsstore/ExtendedSitesCatalogAssetStore/images/products/AssetPush/DTP_AssetPushHighRes/std.lang.all/ti/on/Wavin_Osma_Soil-Waste_Installation.pdf *Edit Just had a looked at the BBA cert for the Wavin Osma AAV 4S304, this gives very clear guidance on installation location. Added another pic. https://wavin-digital-indianajones-prod.storage.googleapis.com/assets/category/1520297e-f72b-4c71-9b89-dc027056ec87/d3c79907-6216-49e4-b861-3f792432bcdc/2b939e03-ca09-4297-8f3b-828b5b200e22 The British Plastics Foundation have a good guide on AAV https://www.bpfpipesgroup.com/media/71872/Air-admittance-valves-for-domestic-properties-v2-Jan-2024.pdf

ASHP cooling is one of the cornerstones of my design. I didn’t want to install AC. You may only need active cooling on average 3-4 weeks* a year in my part of England, but it sure would be nice to make things a little cooler during those times. There are a number of different strategies you can deploy for cooling. I chose to have UFH both downstairs and upstairs in insulated concrete slabs. These slabs will create a cold heatsink to cool the whole house. I only put in the UFH upstairs for the cooling. You can set the ASHP weather compensation curve to be 2°c above the dew point. You would also insulate the pipe work. Is there a risk the UFH pipes in the slabs will cause a problem, to be honest I don’t really know. All the other associated pipework is visible to inspection in my build. The weather has been so poor this year, that I’ve only had the cooling mode active on 2 occasions just for fun. My system was only commissioned in April. *this is a made up figure. I have no idea how many evenings a year have temperatures above 27°c. Although the Met Office told me this May was the hottest on recorded, so forgive me for being very sceptical about any official data.

In the comments Adam is asked if it is vented or unvented and where the expansion vessel goes. He replied,

New mini store water tank from Newark Cylinders designed with Heat Geek. Specifically for ASHP, with 40° water temp requirement. Not an unvented Cylinder apparently. How it works video will be up tomorrow.