AndyRP

Thanks Peter. Hadn't thought about 10mm but makes sense for such a short run. The basement is separated by well taped chipboard and vapour control membrane. I saw a lot of similar units that take waste heat from the house and extract it. These look neat but I'd already committed to a full MVHR. As I understand it the AroSTOR is different and designed for garages etc. It is often ducted to bring air in from outside and kick cold air out somewhere else. These ducts are in theory optional but I do see the risk in blowing cold air up at my timber joists so I'll probably duct at least the cold air outside.

I'm installing a new plumbing system in a retrofit that I'm doing to a small Victorian terrace. Heating will be direct electric panel heaters downstairs (peak heat demand should be under 2KW). Hot water will be supplied via a Vaillant AroSTOR 200, which is an unvented hot water cylinder with a heat pump on the top of it. The reason for me choosing this is that the property has little outdoor space but a decent basement. This heat pump water cylinder allows me to position the unit in the basement, thus easily drawing on external air and not interfering with the MVHR system in operation within the building's thermal envelope. I welcome any thoughts on the setup in general but my specific question is about correct pipe sizing for supplying hot water through the property. I have an eye on the challenges of speedy hot water delivery, energy efficiency and adequate pressure. The supply runs are: - GF kitchen sink, diswasher; 3m from tank - 1st floor bath/shower, toilet, sink, washing machine; 10m from tank - 2nd floor shower, toilet, sink; 13m from tank Mains pressure is 'good' (I guess I should probably measure it somehow but haven't). Baths are rare so quickly running a full bath is not a high priority. I realise convention would be to run 22mm to the bathrooms but this seems to overly favour speed of water delivery over efficiency. Can I get away with doing everything in 15mm plastic pipe? At the risk of muddling the thread, any thoughts on the merits of supplying dishwasher and washing machine with hot water from the cylinder also welcome.

@LA3222 Thanks for your really clear diagrams on this thread. I'm currently scouring BuildHub to try and get my head round a simple UFH heating setup using Willis heaters for low energy refurb (total heat load about 2KW). Is the diagram above what you went with in the end? Has it worked well for you?

I have a similar conundrum. Renovating to EnerPHit standard with a heat load in PHPP of 25w/m2 and a treated area of 72m2 giving a total load of 1800W. We are a family of two adults and two small kids. The most seemingly reputable company I'm speaking with have quoted me a 5KW Vaillant Arotherm Plus together with 40w buffer tank and 300L water tank. The more I look into this the more this seems overspecified, especially since Vaillant have a 3.5KW model. I am a bit worried however that even this would be overkill and lead to an inefficient setup. I've read about the difference between fixed and inverter driven heat pumps and the fact that in my situation I should be looking for an inverter driven one so it can run at below max output allowing constant (and therefore efficient) operation more of the time, avoiding short cycling. But I can't see anything on the Vaillant website to suggest it has a variable output. Is this variability just a given these days, hence it's not mentioned or is it a helpful differentiating factor? This is an interesting alternative approach. It would certainly be nice not to have a big heat pump in our small garden. @JohnMocan you give any guidance on where I could helpfully read up on a setup like this?

I've struggled to find resources on this and found this thread v useful so I'll attempt to dust it off with a few questions. I'm renovating a small three storey (inc. converted loft) Victorian terrace. The existing brick inspection chamber is shared with our neighbour. We plan an internal AAV together with a separate ventilation stack for the reasons mentioned above. I'm in two minds between running it up the back of the house vs. putting it in the (v small) garden. 1. Garden vs up the house seems primarily a trade off between smells in the garden or a big ugly pipe up rear of the house. Are there any other pros/cons I've missed. I think garden utility probably wins and I'll run it up the house. 2. Of relevance to question 1, what size must the ventilation stack be? Part H does not seem clear on this. 1.32 allows the soil pipe to be 'reduced' in certain circumstances but this clause is clearly talking about the top of a standard discharge stack where only the portion above appliances is dedicated to ventilation. Since it's not explicitly addressed I guess there is an argument for 50mm as that is smallest discharge stack allowed in the case of low flow rates and a dedicated ventilation stack will have a flow rate of zero? 3. Can the separate ventilation stack go directly to the existing (shared) inspection chamber or does it need to be branched from the pipework upstream? I've attached the current ground floor plan that shows the relevant runs in case useful. A.30915.4.101.02_A3.pdf

Thanks @joth and @Mr Punter. V helpful to get your input. I think I'll push forward with no heating other than electric towel rads in the upstairs bathrooms and see how it goes.

I am renovating and extending a small Victorian terrace to (hopefully) EnerPHit standard. Ground floor will be c. 40m2 and then there is a 1st and 2nd floor each about 30m2, so total of about 100m2. Heating will be via a heat pump and UFH on the suspended ground floor. There will be a whole house MVHR unit (without any heating element). My question is whether I need any heating on the 1st and 2nd floors and if so what? Rads or UFH? It's a complex and expensive project so I need to find simplifications where I can and I wonder if I can get away without any heating on the top two floors, perhaps just running cables for a few electric radiators to be added if they end up being needed. All the living areas are on the GF so I'd be quite happy if the 1st and 2nd floors were typically a few degrees cooler.