SteamyTea

Or worse, powering your neighbours house as they run the tumble dryer on a sunny day.

Generally it buffers as a liquid, not a vapour, so the risk is the same. Having said that, I am of the mind that a few grams of liquid water does not pose a long term problem. If it did, all newly build masonry buildings would rot the timbers in no time.

Cheers, mother (expletive deleted)er

Yes, I have been saying that for years on here. The joints will need to be treated when it is dry, but as they can be done in a very short space of time, and the joint can be made near enough rain proof with a PU adhesive during installation, it is not much of a problem. One advantage of sheathing a substrate is that it is done in a workshop, where there is less problems with weather, the UV in sunlight can cause the exposed surface to cure faster than what is next to the substrate, this can cause problems with under curing. Another really big advantage is that it is easy to sheath different substrates i.e. thin ply, thicker OSB, foam sheets. If you want to get really posh, different surface finishes can be incorporated i.e. non slip, arty patterns, fake tiles. I really do think that GRP is an underused material, but I think most of that comes from the industry 'doing it on the cheap' and as an afterthought/panic measure, rather than incorporating it at the design stage.

I wonder where that money comes from. Oh yes, the rest of us poor (expletive deleted)ers.

I started using GRP 49 years ago. I suspect that the remains of that kayak is still not rotting away at the bottom of the Isis between Newbridge and Northmoor.

Mist is condensed water vapour, so needs to be treated differently. Needs to be treated as rain, not vapour. Below is the data near me for last year. At temperatures below 16°C the RH is pretty consistent at around 86%. That accounts for 79% of the time (don't tell emmets that it is really cold and damp in Cornwall). Say climate change raises the temperature by 1°C, from 12°C up to 13°C, the RH will reduce by 2%, to 84%, really nothing in reality.

No, on two fronts. kW, is power, Kw is nonsense. Now a W is a unit of energy per second, J/s or J.s-1. The SI unit for energy is the joule, not Joule, that was the man it is named after. it is a derived unit made up from SI base units of kg⋅m2⋅s−2 An hour is 3,600 seconds. So, even correcting the Kw to kW, we have, in your example: 3,000 [J.s-1] / 3600 [s] = 0.83 J, which works out as 2.3 x 10-7 kWh, so small to be meaningless. Now if your energy usage, over 24 hours, is 56.5 [kWh] then to convert it to power [kW], just divide by the time [24h]. 56.5 [kWh] / 24 [h] = 2.35 kW (the time, h, cancels out).

Quite often when companies sell you a product on staged payments, they are more interested in the commission they receive from the finance houses. This was very much the case with car sales 30 years ago, the finance commission was greater than the sales profit. The trouble with this is that it leads to mis selling, and that does absolutely no one any favours. The UK over the last 20 years or so has had similar initiatives, but they have all failed. Roof for Rent PV was a classic, as was the Green Investment Bank (2012 - 2017). I can remember many conversations over at the 'other place' about schemes that lend you money to invest in domestic RE and then you pay it back with a slightly higher energy unit cost. The idea being that overall, your annual bill is lower. Never happened. Then we had the FiTs and RHI. Now the FiT was a success, when it paid 3 times the unit price, now people complain that they only get a third of the unit price, so not worth installing PV. If you want a heat pump, go out and buy one, avoid all the government incentives and just do your own research on prices. While that may not help 'the little old pensioner neighbour', it may help you. If you don't have the knowledge to make a decision, read up on it more. None of us where born with an innate understanding of thermodynamics, or poetry, for that matter.

Let us call it, at best, a mean of 50W. 0.05 [kW] x 8760 [hours] = 440 kWh/year. That is a 13% increase on my usage (~3,300 kWh/year). Or, to look at it another way, 10 gallons of diesel, nearly 700 miles, or an extra trip to see my Mother. I just done a speed check and got this, does not seem so bad.

I think you have summed it up quite well. Dew Point (condensation temperature) can be estimated quite accurately with this formula. Tdew °C = T(internal °C) - ((100 - RH(internal %))/5) The temperature gradient can be considered linear, so the middle point will be half the temperature difference. Using the typical ΔT of 20°C and an overall roof thickness of 0.25m and an internal relative humidity level of 60%. T = 20 - ((100 - 60)/5) T = 20 - (40 / 5) T = 20 - 8 T = 12 As the roof is 0.25m thick, and the ΔT is 20, that is 80°C.m-1 (20°C / 0.25m) Dividing by the dew point temperature, 12°C 80 [°C.m-1] / 12 [°C dewpoint] = 6.7 m-1 1 / 6.7 [m-1] = 0.15 m So in that situation, there is a condensation risk at 150mm and extending outwards. You can see why the insulation is preferred on the outside of the rafters. Now the real answer is how often do you get those conditions. I had a quick look at 2023 weather data for my location and the percentage of time when there was a greater than 20°C temperature difference was 0.36%. From my understanding, a warm roof is treated just like an ordinary wall (and why wouldn't it) in that you still need to fit a vapour control layer, this reduces the higher (generally) temperature and RH air migrating into the structure. (it is very early in the morning and I may have made a mistake, but shall let other find it)

Joe Grundy in the Archers always claimed that it was his Farmer's Lung that stopped him doing any hard work. Sing Along time https://en.wikipedia.org/wiki/File:Barwick_Green.ogg

Plan is important as well, you could have 1 metre wide and 150 metres long. https://www.dummies.com/article/academics-the-arts/math/calculus/how-to-use-differentiation-to-calculate-the-maximum-volume-of-a-box-192226/

Maybe because we have very poor quality control in the building industry. It is also populated with arseholes.

About 65 kWh I think.

The h cancel out, so becomes kW. Not Kw.

@Nic Are the grid squares 0.5m?

So a foot then

Yes, to a certain extent. In a small place like mine, it would make no difference, but if the place is a more complicated than a simple rectangle, there may possibly be savings to be made. It is why we do room by room heat loss calculations, they show up this sort of thing and help make the decisions.

Shame you sold your tape measure.

This may need a bit of clarification. There are Zones and Circuits. 1 circuit can have many zones. Basically the zones are connected together in parallel and act as 1. Different pipe spacing can change the amount of power that is delivered to different rooms. That is a good point, if not built yet then it is the time to review the thermal losses.

My day rate electricity is currently 37p/kWh (and getting cheaper by the quarter). So £8500 / 0.37p/kWh = ~23 MWh That is about double my area. I use around 3.3 MWh/year, and I have no technology at all, just insulation and airtightness. So if you use double that, and if you fit an ASHP you will use a lot less, that is 3.5 years worth of electricity, and nearly £500 a year on lost interest. PV on its own is probably worth while, as long as you do not get a silly price to install it and 3.5 kWp is a usable amount. You can probably use 2/3rd of that, which amounts to 2.3 MWh/year. Leave the batteries until a later date. A 5 kW monoblock ASHP will probably do you, as will a 200 litre cylinder. All you need, keep it simple.

Some things, DHW, Space Heating and MVHR are in reality, separate, so should be treated as such. DHW can be dealt with in 2 ways. Heated and stored for later usage, instantaneously heated when needed. MVHR is just ventilation, it saves you opening the windows. The confusion starts when the heat source for DHW and the space heating are the same unit. We have got used to that with combi gas boilers, but they work in the same way as a heat pump, but just at a different power level. The word power is important there, it is not temperature or energy. Basically, you put water in one side, hotter water comes out the other which you then use to heat the house or a cylinder for your hot water (or use directly). So the only controls you need is a diverter valve to push the water into either the heating system or the DHW system. The problem comes because you want the heating system at a lower temperature (generally) than the DHW temperature. That is set up by the boiler/heatpump control system. It may seem complicated when people start talking about different temperatures and flow rates, weather compensation or load compensation, but all that really means is that the maximum power point is not always the same as the maximum efficiency point (like a car, too low in the rev band and it will still die, too high up the rev band and it will use a lot of fuel). Batteries and PV are a bit more complicated as they are more to do with your usage pattern and the amount of generation on the day in question. There is a lot being made of how great batteries are, but they are still an expensive form of getting electricity to power something. Just because the energy used charge them may be cheap, or seemingly free if from your own PV, there is still a cost because they do not last forever, and if you don't use most of your stored energy, then the next charging opportunity is missed. Sometimes this energy can be diverted to the DHW, but if that is already 'full' then it gets exported. Initially I would treat each part individually and monitor what is happening (well worth spending £100 on a decent logger), then after a year or two, start to tweak the systems, which may involve buying some extra kit, usually more sophisticated controllers. Where you are near Exmouth has a similar climate to where I am, warm, lots of rain, burst of powerful sunshine, and always windy. You cannot control those elements. So. Set up MVHR and let it do what it is designed to do, change the air and recover some of the energy in it. Set up the heating system to deliver at the lowest temperature and flows possible i.e. weather compensation. Set up a diverter on the PV system to charge batteries first, then divert to the DHW cylinder. You can try running heavier loads like a washing machine around noon, but these days washing machines are very energy efficient, I think mine uses about 300 Wh for a load, 10p worth of the most expensive day rate electricity that EDF can supply me. Make sure you don't have parasitic loads draining your system, I used to use an old desktop PC to monitor my energy usage, it drew 300 W of power constantly. I now use a Raspberry Pi that uses so little that it is basically unmeasurable. Buy the lowest power/highest efficiency fridges and freezer you can get, they really do make a difference. @Radian (not seen him around for a bit) bought a new fridge that uses less energy than my much smaller one, and mine only uses 5W. If you really want to save energy, get a more economical car. My current car uses 700 Wh/mile (65 MPG) but an EV can easily halve that. And monitor and analysis your usage.

Not much higher than the surrounding uncovered ground. We don't thermally insulate our houses by sticking on another layer of bricks. Clay has a k-value ~3 W.m-1.K-1. So not very good. By the very nature of building, the ground needs to be well compacted, so often a worse thermal conductivity. It is also a nature of physics that the greater the temperature difference, the faster it looses energy. So what does get through the slab, is then into a semi infinite heat sink. A lot of people think that the ground under a house makes for a good thermal store, so good that every house has one. There is a reason that insulation has a low k-value and a low density, it stops the energy leaking out from where you want it.

Not that often. Maybe on a few really cold winter days. At the moment the air temperature is 13⁰C and the ground temperature is 6⁰C. The sea temperature is 10⁰C. So most of the time the ground is colder than the air, and especially the air in a building. And people wonder why I say that just adding mass to a building makes it colder.