LnP

The 4 pipe has two coils and the 2 pipe has one.... so are you saying that the 4 pipe, in total has more coil, a larger heat exchanger i.e. they didn't just cut the 2 pipe in half to make a 4 pipe?

Sorry I think I'm missing something .... so regardless of the position of your summer/winter switch, when there's a call for heat from the DHW, the ASHP automatically switches from cooling to heating?

Very interesting. Thanks @JohnMo for sharing. I'm not clear though what happens to the ASHP when you're in summer mode and the DHW calls for heat. I can understand how a call for heat from the DHW makes the 3 port valves turn and the CCT pump start. But won't that send chilled water to the cylinder? What tells the ASHP to switch to winter mode and start producing heated water?

My situation's a bit different, but this might help ... We're going to demolish the existing dwelling and build a new one. The water meter was in the existing house and needed to be relocated. At the same time, I wanted to put in a new 25 mm MDPE pipe, running about 15 m across the plot, from the new meter. I got a moling company to that for £780 + VAT. No need to dig a trench. The moling company made the new connection to the exiting stop tap with a suitable Atplas fitting for the new meter. UU then came along and fitted a new meter at the existing connection in the street. Cost was £183. The stop tap is in the pavement on our side of the street. In your situation, I'd start by talking to a moling company to get a price for the new line and stand pipe. They might have suggestions about the best way to approach the utility. It was all cheaper than I expected. Not your situation I know, but might be helpful.

Well here's one way it affects self builders. I just got this from my approved inspector, PWC: Please find below the Notice of Cancellation of our Initial Notice regarding the above project. The reason for cancellation is: we have become unable to continue to carry out the function with respect to any of the works to which the initial notice relates (as per Section 52 (1) of The Building Act 1984), due to the Building Safety Regulator (BSR) rejecting PWC application to be put on the Building Control Approvers Register. PWC have gone into voluntary liquidation. Apart from losing money, I'm trying to find out from the LA what that means for my project. The Initial Notice was made prior to the change to the building regs in 2022. I hope this doesn't mean that the new regs will now apply to my project.

Excellent write-up, thanks. I'm in the process of assessing timber frame quotes, looking at four companies. As mentioned elsewhere, it's not straightforward because they all have different scopes. I've not finished yet, nevertheless it's looking like MBC will be ~30% more expensive than the others. Of course best value is not always lowest cost, but I'm interested in views on this. PS I'm going well insulated but not Passivhaus.

Press release from the HSE. This is a consequence of the The Building Safety Act 2022, which implemented recommendations from the review of building safety regulations lead by Judith Hackitt. The focus was "high risk buildings" (>7 floors, 18 m, 2 residential units), but the Building Safety Regulator's website says that they are there to: regulate higher-risk buildings raise safety standards of all buildings help professionals in design, construction, and building control, to improve their competence Does this have any impact on self builders? Will BCOs be looking at things they didn't look at before?

I'm trying to get up to speed on this, so excuse me if these are daft questions. We're planning an ASHP with UFH on the ground floor and upstairs bathrooms. We want to use the ASHP for cooling. We're got 3 phase electrical supply and plan ~11kW of PV. So following questions: 1. The ASHP will only need to run in cooling mode when the sun is shining and for a few days a year. Would it be true to say that designing the system to optimise the performance of the ASHP in cooling mode is not that important? 2. Upstairs I'm thinking about fan coils in the bedrooms for cooling, but with the possibility that they could also be used for heating in the unlikely event they are needed. Downstairs I'm thinking about fan coils for cooling, i.e. no cooling in the slab. With that configuration, why wouldn't you have the fan coils on their own circuit via a zone valve and plan for a flow temperature below the dew point, i.e. insulate the pipes and have condensate drains on the fan coils? If your flow temperature is limited by dew point considerations, doesn't it put more uncertainty around whether you're going to have enough cooling capacity? Thanks for your understanding if these are silly questions or I've missed something!!

Nice tiles. What are they? Thanks

I visited a timber frame build recently and the builder told me he runs Cat6 to every room in the house and provides a Unifi wifi access point in every room. He said it was because metal foil VCL interferes with the wifi. Is this overkill?

It's been said on here before, but this graph from the European Heat Pump Association shows clearly the relationship. A higher ratio of electricity price to gas price ("spark gap") correlates with fewer heat pump installs. The UK has the highest spark gap amongst the countries included in the analysis. No surprise then that people in the UK are not choosing to install heat pumps so much as other countries .... when there is a choice. Btw, it's helpful that the UK are included in this analysis.

+1 and I'm very happy to pay for my planning consultant. I've noticed BH has a strong DIY ethos. I even remember somebody on here commenting that if you don't have hands on the tools, you're not a self-builder. In my opinion, being a successful self-builder (which I'm hoping to eventually be), involves knowing when to buy help in.

The STA guidance has tables of separation distances. It depends on the classification and size of the timber frame.

🙄 My goodness!

I don't think you can generalise. It depends on the character of the CA and the prominence of the building. I replaced some of the windows in a Victorian building in a CA and it never occurred to me to get PP. I've sold the house in the meantime and the only question I got from the purchaser was where I'd got them because they liked them and wanted to put in some more. I just did a complete refurbishment of Victorian coach house in a CA including all new windows and doors, for which I got PP. There were no conditions about that. It has uPVC windows and composite doors.

I've just run across this as well and realised I'll need extra money in the budget for it. Even if you're planning to clad the building in brick, you have to consider a fire during construction. The STA have published guidance, "Design guide to separating distances during construction. For timber frame buildings. Version 3.3", and "The 16 Steps to Fire Safety", available here. I've learned I'll have to do an off site fire risk assessment. I'm still considering timber frame quotes but Potton have quoted £1,188 to arrange one. Haven't shopped around yet. I don't know yet what the cost of the mitigation will be. One timber frame supplier said they would expect to simply supply the outer sheathing on the side closest to the neighbour (and 2.4 m round the corners) in cement board instead of OSB which wouldn't cost that much more.

Well, that is my question. All other things being equal, is there a difference in efficiency between R32 and R290? @JohnMo's info suggests there isn't. But comparing quoted efficiency numbers might not give a valid comparison, so I'm curious whether there's a fundamental thermodynamic reason to choose one over the other. There are several reasons why a manufacturer might choose one refrigerant over another. R290 is preferred if you need a high flow temperature because its critical temperature is higher than R32. At a 70o C flow temperature, R32 would be close to supercritical (critical term 78o C) in the condenser and supercritical fluids don't condense. Both have low enough boiling points at suitable pressures to be able to be evaporated in the evaporator in cold winter air. The Carnot engine is the most efficient heat engine theoretically possible. The efficiency of a Carnot engine is independent of the working medium of the engine. But the irreversibilities inherent in the vapour compression cycle cause the coefficient of performance of practical applications to depend on the refrigerant. A heat pump isn't a Carnot engine but the same principles apply. If you're buying a car and are interested in fuel consumption, it will be handy to know that diesel engines are inherently more efficient than petrol ones because of their higher compression ratio. That's an inescapable thermodynamic fact and it will save you scrolling through petrol engine ones to find the best fuel consumption. Considering an R32 vs an R290 heat pump in an application where both would be technically suitable (i.e. a 45o C flow temp), is there a fundamental thermodynamic reason why you'd choose one over the other? COP, SCOP or something else? I'm curious 🙂

For the same operating conditions (in heating mode, the flow temp and outside air temp), how do the COPs compare for R32 vs R290?

@JamesPA bit off topic but what software did you use for the drawing? It looks good.

I am also figuring out the same thing. Your best bet is to talk to an installer even if not's the one you plan to use. That's what I've done and that way you'll get real world advice.

I'm starting a new thread after seeing comments in this one about the risk of fire from PV panels. I'm planning an in-roof system on timber frame. There were some interesting concerns raised in that thread and I'm interested to learn more. I shared a link in that post to guidance from the Fire Protection Association on fire safety with PV installations. It's mostly aimed at commercial installations and doesn't give much specific guidance. There's also a guidance from the IEC but it's quite expensive and I haven't bought it. One of the things the FPA guidance says is that PV panels should be mounted on a non-combustible surface. On-roof would be better in that respect as it's on top of tiles or slates, but would there be any benefit in putting cement fibre board under the panels for an in-roof installation? Any other suggestions to manage this risk?

Guidance on PV panel fire safety from the the Fire Protection Association here RC62 RECOMMENDATIONS FOR FIRE SAFETY WITH PV PANEL INSTALLATIONS

It was on the planning drawings but for building regs I didn't do a Full Plans Submission, just a Building Notice. You're right that if I'd submitted building regs drawings they might have commented. But this was a renovation of a dilapidated Victorian coach house and there was a lot of uncertainty what problems we'd find and how we'd solve them. Building Notice seemed like the right way to go. This was the right decision albeit that the balustrade caused some head scratching.

There's a lesson here which I wish I'd known before I built our roof terrace. If you're planning a balcony or roof terrace, think about the balustrade. How will you mount it? I think it's a bad idea to bolt it to the roof and penetrate the roof covering and have to rely on sealing around the bolts. Also I wasn't happy to bolt it to the copings. Their function is to keep water out of the wall so not a good idea to penetrate them. Also, for strength I'd have been relying on the mortar bond between the copings and the GRP cap across the top of the wall which I wasn't happy about. How will you achieve the required 1100 mm height required by building regs? Doing it the way I did passed BC, but I do take the point that somebody could step onto the parapet. If I had my time again, I'd build that roof without a parapet and just take the GRP across to the edge and down onto a fascia board. It would have saved me a lot of money in building the parapet (bricks, copings, GRP flashings, rain outlets) and I could have used an off the shelf balustrade system rather than having to fabricate something. I didn't realise the parapet would be a hassle it was and was convinced by others it would look nice!

I didn't like the idea of penetrating the GRP or the copings with the balustrade brackets so I used fascia mounts.