LnP

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.