tuftythesquirrel

Heating System Critique Hello, Would it be possible to have some form of constructive feedback on my proposed heating system. The house has been renovated to as close as we can get to Passive house in terms of insulation and airtightness, bearing in mind it was a retrofit of a 1950’s church hall. In the first instance we will use a gas system boiler and possibly switch over to an ASHP at a later date. The intention is to see what is the lowest temperature the buffer and hot water cylinder can operate at, by empirical methods to prove it is suitable for ASHP temperatures. I’ve been observing the ASHP technology and it is still developing i.e. some new systems can now get a COP of over 5. The overall heating design was based loosely on the Heat Geeks (https://www.youtube.com/@HeatGeek) mantra of getting as much plastic pipe in the floor as you can. Then the system can be run at a lower temperature (https://www.youtube.com/watch?v=9x1WeVDIAyA&t=45s). This is beneficial for both gas boilers (maximises condensing efficiency) and ASHP’s (maximises COP). It also means by running the system at a low temperature whilst running on gas, I will know whether it is suitable for an ASHP before I go and spend £000’s. I’ve deliberately used a thin floor screed to minimise the mass and improve response time. Construction Details and U Valves I have attached a few design drawings. Roof - 0.12 W/m²K, 150mm of Kingspan Quadcore composite sheet. Walls - 0.145 W/m²K, 200mm EPS external wall insulation system (EWI Store) Floor – 0.09 W/m²K, 200mm PIR/Celotex insulation, UFH and 60mm Cemfloor screed (as the finished floor) Floor area approx. 375m2 Airtightness < 2ACH Building heat load at -2C/+21C is 10kW Thermal bridge reduction where possible, thermolite blocks at wall floor level, compacfoam underneath door thresholds, steel roof trusses brought inside thermal envelope etc. Gas system boiler 24kW. Underfloor heating via 4 manifolds for downstairs only. Pipe centres at 150mm or less where I could fit them. Separate manifold running at a higher temperature for towel rails and optional radiator upstairs. Hot water cylinder is a 300L Gledhill unvented (PLUIN300), with 2 immersion heaters. UFH uses a 300L Telford unvented buffer tank with 2 immersion heaters and feeds the UFH manifolds via an NRG 6 port zone manifold to optimise heat transfer. Separate pressure regulators provided for the balanced water supplies, the boiler fill loop and non-balanced cold water outlets. I’m putting in a whole house automation system based on the Idratek hardware (http://www.idratek.com/) for the lighting and heating functions. It should allow customisable weather compensation, for the two tank temperatures. I’ve added pressure and temperature gauges so I can evaluate the process. Some of these are also fed back to the automation system so I can log them and look back to see how it is operating. I’ve selected both tanks with two immersion heaters so I can use them powered by solar PV and battery at a later date. I have had plumbers quotes and specifically requested buffer tank for the heating but no one gave me the option as the said they always run the heating directly from the heat source. When I said I would prefer it to prevent boiler/ASHP cycling they said it wasn’t necessary. However, Kingspan have now introduced their Albion Aerocyl cylinder that provides exactly what I have but in a single tank, specifically for ASHP installations, so who is right? Am I correct in saying that although ASHP’s can modulate, this is limited to around 25% of maximum power. So if my UFH requires 1kW, a 16kW ASHP could only produce a minimum of 4kW and would be significantly overpowered and probably cycle. Thanks in advance. P01 - GF Plan Volume Computations - 19.10.2021.pdf P02 - FF Plan Volume Computations - 19.10.2021.pdf UFS Q36658-001d Ground Floor.pdf Visio-Piping Diagrams v0.54 HWC and BT.pdf

Hi, thanks for the responses @Hilldes and @Iceverge, you both seem to have arrived at the same solution, which to me is good thing. I've had a look at the HepVo and I think it's just a different brand of waterless trap to satisfy the regs. I picked the Hotun product because they make an audible alarm that can be fitted to the bowl to detect when the T&PR valve operates. As suggested I read a few more posts (below) I relating to this topic and realised I’ve been concentrating on the section of the building regulations i.e. G rather than H. https://forum.buildhub.org.uk/topic/6727-soil-stack-passive-house/#comment-113214 https://forum.buildhub.org.uk/topic/4459-air-admittance-valve-soil-vent-pipe/#comment-71107 https://forum.buildhub.org.uk/topic/8829-soil-vent-pipe-tata-roof/#comment-150735 https://forum.buildhub.org.uk/topic/3975-tv-aerial-in-closed-panel-timber-frame/#comment-63244 Particularly helpful was the input by @Jeremy Harris. It started to make sense when he said you can split up the under and over pressure functions of the traditional soil stack. So what I have learnt from this thread is…. 1. Internal soil stacks are a bad thing if you want to conserve energy. 2. I can just have an air admittance valve internally, at the end of each of my soil pipe runs to satisfy the under pressure function. 3. Externally I need a low level vent to satisfy the over pressure function. This sure beats punching a hole through the 300mm solid concrete wall and the 200mm of EPS insulation. I’m still not crystal clear regarding the position and height of the external vent, since there are no outside toilets etc. but if anyone could suggest anything I would be grateful. Pipework drawing attached. TIA. Church Hall, Narberth - 4th Feb 2020 - DWG-Floor Plan - Substructure Drawing Model.pdf

I don't think that is the case. The reason why it must be waterless is that water or steam very rarely enters the trap, so any water in a normal trap would evaporate. The tundish is a waterless or mechanical trap. There is a seal a the base of the trap held in place by a spring. The weight of a few grams of water in the bowl of the tundish is enough to push the spring back and allow the water to pass the seal after which it returns.

Thanks for the replies. I don’t know the absolute underlying reason behind the “fully vented” requirement, I just trying to understand why it isn’t explicitly stated in the building regulations approved document G. The G3 section is fairly easy to understand but doesn’t seem to mention it. To find the requirement, I need to leave approved document G, look at the FAQ’s for document G, find the section that references the BRE paper and go to the BRE site and pay £9 for their Information Paper IP8/07 (link below) last updated in Jul 2007. This was published some 10 years before the last update of approved document G in 2017/18 according to the website information. To me this seems very convoluted and would be quite difficult to enforce. https://www.brebookshop.com/details.jsp?id=287207 Yes it is a reference document that requires it, but I’ve also got other reference documents that don’t. I was just wondering if anyone had practical experience of this aspect and what building control would accept.

Hi, I know that this issue was partially discussed some time ago but I have an question regarding the discharge pipe from the hot water cylinder temperature and pressure relief valve from the fitted by the tank manufacturer and where it is terminated. Particularly in a passive house, where a fully ventilated soil stack would appear to be undesirable. Our general layout of the house soil pipes, we have a main pipe that traverses the length of the house, then 5 off 110mm spurs that go to each point of use e.g. bathrooms, bedrooms, kitchen etc. At the end of each spur there is an air admittance valve to prevent siphoning. So no soil stack as such. Note my references below apply to the Welsh versions of the building regulations. Also before anyone points out that I need a G3 qualification to do this, my arrangement with my heating engineer is that I will do all the donkey work e.g. fitting the supporting unistrut, tanks, pipework and he will do all the clever stuff, gas work, testing and commissioning to sign it off. Normally, the discharge would go via a 15mm copper pipe into a waterless tundish, then via a 22mm copper pipe to the outside world. So not great for a passive house. There is a section and diagram in the Building Regs. Approved Document (G3.50), describing the general D1/D2 arrangement and pipe lengths etc. However, it seems to be the trend to use a dry tundish that has a 32mm outlet that allows the fitting of an appropriate plastic waste pipe (as made by Hotun/McAlpine etc.). This can also be terminated on the soil stack, via a separate pipe, again permitted in the building regulations in G3.60. My question is, am I OK to terminate my 32/40mm soil pipe onto the 110mm soil stack, when it is not fully ventilated and only has the AAV’s. I always try to read and understand the regulations for each aspect of the build and that is why I am asking. I read the regulations and though I was OK. However, I then read the Part G FAQ’s (link below) in relation to G3.60 which says that the stack must be fully ventilated. If I hadn’t read it I would be blissfully ignorant. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/509352/160321_Part_G_FAQ.pdf I also read a few other articles, the first below by the CIBSE and the second from the NHBC standards. One mentions the fully vented requirement, the other doesn’t. https://www.cibsejournal.com/technical/guidance-discharge-from-storage-cylinders-into-pipework-systems/ https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/8.1/discharge-pipes-from-unvented-hot-water-storage-systems-.pdf Our BCO’s are fairly laid back and don’t seem to want me to jump through too many hoops, so I might be lucky. By the way my heating engineer says it conforms to the regulations. I just don't see where the fully ventilated stack requirement is defined. Any assistance would be appreciated.

You can also use a 50mm Munson ring style clamp, only 50p each at Direct Channel.

You are meant to balance the loads in the house across the three phases....

How about a small piece of 3-4mm anti-alkaline render mesh. Cheap and lasts for ever.

Ahh. good to know I get away with virtually anything, but I just need to get it straight in my own mind. The above suggests you needed 100m3/h, so what size unit did you fit and do you run at 0.4 ACH on a day to day setting or lower and boost when required? Thanks.

If you needed 600m3/h and you can generate 800m3/h, that means you are running at 75% of maximum capacity, which I was led to believe by some companies that this is too high and it should be around 60%. Or do you not run at 600m3/h but lower, which I have referred to in my response in the main thread. Thanks.

Thanks for the replies. I’ve included the hallways since that’s where we will be storing our coats, boots and umbrellas, so a source of moisture. It also has the side effect of balancing the supply and extract rates. Our airing cupboard is a misnomer, since it is actually a walk in wardrobe, some I’ve allocated it as a supply point. I know I’ve also included a plant room and a workshop, which normally is done, but we may convert these to bedrooms in the future so I would rather include these now. So this makes my unit larger. According to my calculations the maximum rate I need is 78 l/s for supply and 72 l/s for extract to meet building regulations, but also in the rooms that people don’t normally include, hallways, workshop. So this is 281 m3/h supply and 260 m3/h respectively. So if I round it up to say 290 m3/h and pick for example, the Vent Axia Plus B, rated at 490 m3/h. Even when running at the flows recommended by the regulations, I will still only be running at just under 60% of the units capacity. Does this not give me acceptable headroom? I believe most people say the regulations flow rates are over the top, hence giving me even more slack. Approaching it from another angle, using ACH, if I take the Vent Axia Plus B unit and run it at 60%, it will generate 294 m3/h. My building volume is 749m3. So around 0.4 ACH is possible. Unless I’ve made a mistake in the maths, the unit I’m looking still seems a contender.

No, not stupid and I’m going through the same exercise. Our useable floor area is around 360m2 and I’ve had quotes for a single Stiebel Eltron LWZ 280 Plus MVHR Unit (Rated at 350m3/h) through to twin Vent Axia Plus B (Rated at 980m3/h). So I’ve gone back to first principles. The Passivehaus Trust Good Practice Guide: MVHR for single dwellings September 2018, Rev 1.2, says use a minimum of 1m3/h per 1m2 of floor area, so based on that we need 360m3/h. However, when using the Building Regulations 2010 Part F1 - Ventilation Dwellings, 2022 (for Wales – sorry if the Table references are different), you have to use Table 1.2 for extract and Table 1.3 for supply. But the following also applies (for supply only)…. 1.24 The minimum whole dwelling ventilation rate for the supply of air to the habitable rooms in a dwelling should meet both of the following conditions: a. A minimum rate of 0.3 litres per second per m2 of internal floor area (this includes all floors, e.g. for a two-storey building, add the ground-floor and first-floor areas). b. A minimum rate determined by the number of bedrooms, as specified in Table 1.3. So in practice, because I have MVHR supply and extract terminals in nearly all rooms, for extract if I use the 0.3 multiplier my kitchen is 9.9 l/s, however table 1.2 says it should be 13 l/s. Again, for supply if I use the 0.3 multiplier my bedroom is 6.5 l/s, however table 1.2 says it should be 10.3 l/s (3 bedrooms is 31 l/s). So the BC tables effectively add flow for specific rooms to the overall flow rate. I’ve attached my spreadsheet to hopefully demonstrate this. Doing the maths, I end up with 281 m3/h for supply and 289 m3/h extract. I have the same issue, regarding do you sum the supply and extract or take the highest value. I also want to get though building control, so I was going to fill in the Appendix C - Completion checklist and commissioning sheet myself. Jeremy Harris on this forum gave a good method for commissioning the system, but other people seem to agree that you set it up to get through using the building control values, then throttle it down again. Any input appreciated. MVHR Flow Rates v0.04 (1).xlsx

Please could anyone help with the following, re. airtightness barrier. We are carrying out a restoration of a 1950s church hall, rendered cavity, brick and block construction. We have a Kingspan Quadcore composite steel roof, fitted with additional seals. The floor build up is 300mm concrete, 200mm PIR and 70mm Cemfloor screed, painted at the floor junction with Pro Clima Aerosana Visconn to continue the radon barrier under the concrete. The task is to make the walls airtight. There is a 200mm EWI system on the outside of the building. It is twin skin cavity, but having been filled with concrete due to the poor state of the block work. I was going to continue the Pro Clima Aerosana Visconn from the roof panels down to the floor. I’ve used the airtight paint but it seemed a little frail for our site conditions. e.g. we used it on some of the wall sections, where the joists run parallel to the wall and would be subsequently difficult to access to plaster. But having had a few knocks with bits of flooring etc. the paint has peeled off the wall. There are lots of maybe’s…. The EWI maybe reasonably airtight at the external render surface. The concrete in the cavity maybe airtight where it is continuous, but it is impossible to know. The cement render on the internal brick/blockwork maybe airtight. So my question is, would a plaster parge coat be a better bet and if so what plaster? The plaster will lap airtight tapes or paint at the window/door junctions. Please note, this is only to provide the airtight barrier. A decorative board will create a services cavity to run pipes, ducts and cables etc. British Gypsum obviously make a full range but they don’t have any real world figures regarding airtightness. I spoke to their technical support and they recommended their Soundcoat Plus. However, they can’t say that it is 10 times better than their other products, since no one has conducted any tests. The Passive House Guide To Airtightness (my Bible!), suggests 6mm of wet plaster is airtight. I wanted to use the Thistle Universal OneCoat plaster to get a good build up and reduce the labour costs. Has anyone had a similar situation and achieved good results with this solution. Any comments welcome. Cheers.