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Is the flooring actively used? If not, then there is no need to lift it, just add insulation on top. If yes, then rigid insulation boards (creating floating floor) may be the answer. I'm doing a hybrid: in the middle (under the ridge) rigid insulation boards covered with planks to spread the load, but away from the centre standard wool, proportionally thicker. That way I loose less headroom where access is needed, and save on cutting the rigid boards (nasty dusty affair)

If it's got water, it is not incidental use. Dig a hole, check what used for the existing carport, match it

What is the floor finish? 42 is already high for some materials. But in principle, until you can't get enough heat of the floor, the lower-the better, so 42 is fine. What is the heat source? Good news, the floor extracts a lot of heat from water, maybe even too much As long as it stays at 1.5 Bar long term (it will fluctuate with temperature changes) it is fine. Red line if indicated by a hand is probably adjustable, 4 is fine. Are the loops of the same length and shape? Loop 2 seems to be using 2/3 of the total flow, possibly saturating the pump in the process. Turn the valve on that loop slowly until you get about 1l/min and see if the other loops pick up. You may struggle to adjust precisely, but at least you'll get an idea of what is happening in the circuit with loop 2 slowed down. I'm also finding it impossible to adjust flows with manual valves, Salus kit waiting for installation.

DPM over DPC: - DPC is pretty rigid, by the time you finish the roll of double sided tape, it may lift off where you started - you want to fold DPM nicely in internal corners / fix in external, so it needs to be on top

With only 50mm to play with it will be hard to find something that efficiently provides thermal break. Bonding screed layer with the slab would be imho beneficial, as you get more thermal capacity (unless you are sold on quicker reaction times). With the cold bridges due to the specifics of the construction method I think you need to adjust the UFH circuit layout: pipes running along the areas where concrete forms bearing points would mean heat is transferred this path anyway (not contributing to space heating), so by avoiding laying near the perimeters you don't loose too much on house heating, yet reduce losses.

My opinion (no evidence to support it though) is that the manufacturers' marketing departments came with 'equivalent U value' where they calculate (or make up) gains due to low emissivity of the foil face (hence the gap required) and improved airtightness and turn reduction of the heat loss in their model into what U value of conducive losses would be. In already airtight house with foil facing rigid boards (or other low-e faced material used) the benefit of using them will be close to 0. In droughty, wool filled house, they would do something good, but still not sure if offer value for money

'interlinked' Yours may already have that feature so just use the same brand. Most use wireless connection (own network, no WiFi/mobile required), so no need for 4 core cable (or any cable in case of battery powered)

Correct: you will recover some of the cost of going UFH route by saving space and flexibility on the layout. Warm feet being a 'freebie' Only structural engineer. Possibly test pits can be done from outside so you don't have holes in the floor, but it is down to SE to decide. I'd go passive slab: - sand blinding - DPM - depending on how deep you have to/must not go (existing foundations depth may be against you) and how will it be dug up, then (together with your budget) you have options of using EPS or PIR as floor insulation and deciding on thickness - this bearing in mind that investment in extra thickness upfront means payback (lower losses) long term. - PE separation (250um DPM) - 100mm (unless SE requires thicker) concrete on top with perimeter insulation

Nah, why overcomplicate again? Stated 0.3 tog => R = 0.03 m2K/W U=1/0.03=33 W/m²K Clearly the winner, the trick used of course is thickness of next to nothing - but if the floor surface permits, that is the way to go.

0.13/0.045 = 2.88 - yep, one is 3 times more insulating Not sure how flat the floor finish is, my understanding has always been that the purpose of the underlay is supposed to mask all the imperfections of the subfloor first and then add impact sound insulation. The product I'm looking at is https://www.interfloor.com/app/uploads/2016/08/Heatflow-Wood-Laminate-DURALAY-TS-3.pdf . Although R = 0.035 m² K/W, at 3mm thickness only it gives overall U=28.6 W/m²K. 3mm thickness requires decent floor finish though.

Exactly my silent assumption too: PRV after the softener and all balanced from then on. Also softener is on 22mm pipes, all domestic water on 15mm To help a bit I'm trying to figure out if supplying the toilets before balancing would help at all. One aspect I can't comment on yet is any noises generated by the softener - I'm assuming only regeneration is something to worry about, but the time of the day of this event can be set.

That's only how they are advertised, probably on the assumption that it is the easiest to find a spare space there (by moving all the bottles, sponges etc away), also most likely kitchen is on the ground floor and water enters somewhere nearby. The device could not care less where it sits. The closer you can get it to the stop cock, the more outlets (all but drinking tap in perfect scenario) can benefit. I don't, that was my original plan until I had to repurpose room in airing cupboard for heating manifold. Cold mains will still go all the way up to the ceiling and now back down to the ground level, and then up again before heading to all the outlets. Length of cold water runs won't make much of a difference, it does not suffer 'dead leg' issue as hot water. If you prefer, you might want to insulate them so the extra volume of cold water does not suck heat out of inside (in Winter) and gets condensation on the surface (in Summer) - it is simply easier to warm up small volume to ignore such nuances.

My current rads are 15mm copper from 22mm boiler, and previously I had microbore with combi, which makes me think that it does not matter - the flow speed must change accordingly to cross section (with all the consequences, like resistance/pressure drop) and that's about it. The plumber we parted ways today mentioned whistle effect if I forced him to go 28mm (I checked - it happens due to high flow velocities, quite the opposite large diameter does), hence the question before I make my hands wet.

I'm planning the refurb to be futureproof and wanted to run 28mm pipes to the UFH manifold, so any future ASHP would have easier life. For the time being the combi will continue the service though, and it uses 22mm connections. Any issues with changing midway the diameter from 22 to 28mm (on feed, so 28 to 22 on return)?

Invest in £10 device that will show relative humidity, that will give you an idea how bad the ventilation is and at what temeperature condensation happens - that is roughly the temperature of the wet patch you see. With another £30 spent on a decent IR thermometer you can check for cold spots (fancy thermal camera will do it better, but at a price) and it will better pinpoint where the cold gets in.

I had the same symptoms with a window that was installed without using any foam around it - just screws and mastic on the sides and top, but not under the sill!. With such professional (FENSA certified) job, the outside cold could effectively reach all the way to the inner leaf. With low temperatures this time of the year it causes condensation of water vapour and on plasterboard it is just more obvious. Go outside and have a look around detail under the external sill, you might be lucky to have some mastic/silicone but any cracks will allow cold air to circulate freely.

I'm thinking along the lines that if toilet cisterns are supplied with cold water taken before PRV, they should not affect taps flow when filling in. For few meters of 15mm pipe that feels like a luxury worth having. How does it look like in practice?

Thanks for detailed intro, but more information needed Set how? Condensing is not a separate mode, it is a physical phenomenon: for it to happen the return water temperature must be 54C or lower (and the lower - the better). Judging by how much heat you can extract from water in UFH, it should be condensing. First of all, if you change heating times, you should be able not to sacrifice comfort (but at the expense of higher gas usage). The amount of heat you need suggests the insulation level is poor. How many floors are there? If ground floor is not well insulated from underneath, most of your heat will warm up Mother Earth - that was not an issue with radiators, as the air temperature at floor level was not much higher than floor/ground itself.

Depends on how far from the back wall: small - no PP, bigger - 'prior approval' , biggest-full PP Read here https://www.planningportal.co.uk/info/200130/common_projects/17/extensions/2

Ok, but it does not mean you have to have UFH: you are after upstairs being warm - that's it. Depending on the house layout, use of ventilation (including MVHR) and heating required, both due to conductive and convective losses (U value and airtightness) and solar gains you may need zero additional heating upstairs. Heat carried by natural and force convection (ventilation) from downstairs plus incidental gains: you spending there 8h each day and anything DHW gives away, may as well be enough. Or even too much (there is a thread here on a bedroom overheating). Typically you'd need to add some heat though, but then check what is practical, economical and comfortable. I suggested A2A, as it will give instant heat and instant cold (bonus over UFH), but some noise and airflow, installation is way easier than UFH. You can have electrical radiators (or UFH) - just leave spare spurs for that. Or use fan heaters, nearly 0 investment. Maybe skirting heaters is something that would work for you. With so much wood on top indeed not too much heat will go up. Add insulation below and not much will go down neither, so you'll end up circulating hot water - what can create new issues in itself (short cycling etc). It also will not react quickly if that's what you're after.

Kingspan is a brand, not a material - in this case it is confusing, as Kingspan offers both PIR boards (yellow, lambda 0.22) and phenolic (pink, 0.18). I'm assuming it was PIR that was originally planned, with phenolic at the same thickness you get 20% better insulation at 80% more price. Aerogel and vacuum panels are unlikely to be economical for self build. Any reason for specifically 75mm screed? There are thinner options available, that would free some extra space for insulation.

Is it driven by heat demand, or do you 'just want it'? If you're after boost heating, other options (especially air-to-air, giving you cooling in Summer) may be much better choice, also economically. If you spec the loads properly, you can even have UFH pipes in screed. I like concept of Lewisdeck for example

I think the answer is controls: with a buffer between source (boiler, heat pump) and heaters you demand heat from the source using buffer temperature. Simple. With buffer on the return you'd have to use flow measurement to shut off the source when demand (=flow) reduces, but getting there means more and more struggle for the source (on both modulation and pressure). With the only benefit being lower buffer standing losses, you pick a buffer on supply side every time.

You need to do some calculations, but nothing stops you putting multiple extraction ports - as many as needed to extract volume of air necessary to remove all the excess heat. It should be possible within capabilities of stock units (350-400 m3/h). Do remember that you need to make sure equal amount of air can be delivered to that room - gap under the door will no longer be suitable. Some use pre- and after heaters, so why not? Have you checked exhaust air heat pumps? DHW will happily suck your 24kWh per day Do you mean power supplies? Your heat generation will depend on workload, you mentioned network traffic routing only, but it is probably computing/graphics that will use the most. If you're rendering 24/7, or mining, then the generation will indeed be constant, but in 'normal' use you'll be idle probably 90% of time - currently IT devices work on 'race to sleep' principle

Make sure removal of OSB skin will not affect structural properties of the wall, it may be there not only to keep the cellulose in place