jayc89

What's the best course of action with the towel rad? Reduce flow through it more than the other rads in an effort to avoid the bypass? Thanks for the Baxi Relay docs, I'd seen it before, but I missed this sentence; When a DHW demand is applied to the boiler the Outdoor Sensor is overridden. Which mitigates my concern of the flow temp being too low on the WC curve for DHW.

Thanks for the info, it's really useful. The first radiator the boiler flow will reach is a towel rail, this is in the bathroom directly above the boiler, followed by the landing radiator, neither have a TRV, the landing rad is the one nearest the upstairs stat. I'll test the flow/return temps coming from the towel rad this evening. What else would I be looking for when trying to find a bypass and how would I fix it? Our boiler can be fitted with weather compensation, the main reason I hadn't yet was because the curve in the summer drops too low to heat the DWH. Is there a way around this? I also assumed that being able to request different flow temps from a boiler would be a boiler specific feature, i.e. not something that could be applied generically. It would be ideal for the UFH zone/DWH if possible. I did have a similar idea about setting the mixing temp higher and allowing the weather comp to dictate the actual flow temp. My concern there was we'd end up with hotspots in the floor as the room temp would overshoot the stat. The UFH pipes are sitting on 100mm PIR, with 25mm perimeter up stands. Based on our PA, this gives a calculated U-value of 0.15. I guess you're right that the boiler shutting off isn't terrible, but it's certainly less efficient. My other thought when it comes to the UFH zone is that the boiler is actually having to work harder because the flow is 70, but the return is only 40. So naively I'm assuming it's working harder to heat 40 back up to 70 for the UFH, than it needs to for the upstairs rads, which are returning at a closer temp to the flow. So perhaps the majority of the excess usage us actually coming from the UFH zone and not the radiators?

SOS. I'm tearing my hair out with our current energy usage. Prices going up is one thing, but over the last couple of weeks we've been averaging ~70kWh a day, which seems crazy high. 32kW Baxi Platinum+ condensing boiler set to 70c. Capable of modulating down to 10.4kW 250L DWH set to 50c UFH manifold set to 35c Two zones: 1) Downstairs: 7x UFH loops, approx 520m of 16mm pipe and 63L of water. Energy demand: approx. 6kW based on 100w/m2 2) Upstairs: 8x radiators all balanced. Energy demand: approx. 9.8kW UFH is set to 21c during the day ay 19c over night Rads set to 21c from 6pm - 9pm and 19c all other times Scenario: Reducing the UFH mixing temp from 40c to 35c appears to have increased energy usage by 34%. Hypothesis: The boiler continues to heat at 70c. Reducing the UFH mixing temp effectively wastes more heated water as the UFH mixer cannot make use of it all, resulting in more being returned to the boiler and the loops taking longer to reach temp. Scenario: When just the UFH is on, the boiler return remains low, at approx 40c. Significantly higher than 25c (UFH mixer temp - 10c delta). Hypothesis: The UFH mixer cannot make full use of the 70c flow temp, whilst some is being mixed and pushed through the UFH loops, too much is being returned straight to the boiler, increasing the return temp. Scenario: When just the radiators are on, the return temp remains high (approx. 60-65c) and the boiler cycles every 15/20 minutes. Hypothesis: The aggregate capacity of the radiators is not able to extract enough heat from the water to sufficiently reduce the return temp. I.e. the boiler is too large and/or it's not modulating down far enough. All radiators are balanced in that they all heat up at roughly the same time. I'm reaching the conclusion that the boiler is just massively over sized for our requirements. Even if everything was running at the same time (inc. 3kW for DWH) we'd only need 19kW in total. It's been fitted over a year now so getting the plumber back to rectify this will be near impossible. Whilst a buffer tank should reduce the time the boiler runs whilst the UFH is calling for heat, I suspect our only long term solution is to crack on with insulating the house and switch to an ASHP, but until I can do that, if anyone can offer any advice on how to make better use of our heating system, I'd greatly appreciate it.

Jeez I use half that just heating our DHW 250L tank, couple of showers a day, pressure is around 3bar so it only takes a 15 minute shower to empty the tank.

We have 7x loops and had 3x zones. Over summer I changed that a single zone. I haven't notice any obvious difference in efficiency. I had to increase the pump speed to get the flow rates set correctly as it was having to serve all loops at the same time, which it previously might not have had to do. I've also started playing with the temp differential (i.e how low below the target temp before the stat calls for heat). For some reason my stat was set to 0.5c (even though the manual says the default is 1c) and I found the boiler to be turning on every 30 mins. I've dropped it to 1c and it's now coming one once an hour, so a difference but I'll need to wait a couple of days to see whether it's actually made it more efficient to run...

That would have been useful info, wouldn't it. 1.8m. The original wall's built using lime mortar, it's that old. We could probably re-use some of the bricks, but wouldn't have enough for the full job (we're making it taller in areas) so the cost of sourcing matching bricks, cleaning up the existing ones etc would probably negate any savings.

We're going to have our boundary wall replaced, it's > 150 years old and has a pretty nasty lean on it. In total the section is 30m long, so we're going to go for a more chunky 9" English bond wall. The first quote has come through at £300/sqm excluding prep (knocking down old) or groundwork (laying new concrete foundation). Nothing special about it, no reclaimed bricks or anything. We're based in Yorkshire. This seems pretty steep to me, a quick Google suggests £200-£250 inc. foundations, but those estimates are a few months out now. Am I way off?

ETC helped me out massively after we were lumbered with a terrible set of drawings from our initial technician. His help and advice ultimately shaped the overall direction of the extension we're hoping will be granted final approval this week!

Only works if the outer leaf is to be rendered, or hidden in some other way though, not facing bricks?

Stat. 21 during the day (up to 9pm) and 19 over night.

Our existing manifold is running at 45c. I laid a new screed floor a couple of months ago which is now ready for commissioning. Ideally I'd do this without dropping the temp for all other loops. What's the best way of doing this without losing heating to the rest of the house?

Minimum u-value here is 0.18 which I believe means we'd need a minimum cavity of 170mm. Given the digger bucket size, 175mm would make the most sense. I dropped the insulation company an email asking for some advice/materials to pass back to our Architect, so we'll see what they say.

Thanks, another concern was the additional costs of wall ties, lintels, cavity closers etc. Has any one done the maths on how much extra a wider cavity cost them? I assume there are savings to be had with EPS beads, presumably, cheaper than K106 boards.

Would you minding sending me their details? Here or DM would be great.

This is exactly my concern. With the best will in the world I don't see the builder paying enough attention to butting up the PIR boards, which I don't want.

East Yorkshire so only a couple of hours away from you, do you think you guys would travel that far?

We're not discussing building regs with our Architect. We're going for a traditional cavity wall construction (for a multitude of reasons I won't go into here). I touted the idea of a 175mm cavity using blown EPS beads once the cavity is constructed and closed. He's less keen on EPS beads, worrying that it's effectively done blind and he believes there's also a risk of slumping over time. Ultimately he's left the ball in my court. Is there are evidence out there to mitigate his concerns? Whilst I could of course "over-rule" him, I'd prefer to work with him rather than against him.

Makes sense. I was thinking of potentially battening out after the AVCL and before PB to provide a service void for lights etc as to not penetrate the AVCL. Of course all the cables already in the loft would need pulling through first...

Is this Duplex boards on the first floor ceilings? Would a membrane across the bottom of the roof joists, then PB, work? Could also act as an airtight layer?

As part of some remodelling we're doing, I've had someone come up to move a couple of windows and brick one up. Given the house is old, I was quite meticulous in who I wanted to work on it, making sure whoever it is has a track record of using the right materials for the job. I found someone local, a young lad, who's done quite a bit of restoration work on older properties using lime mortar. He knew what he was talking about and his past work looks good. Sods law that I'm away with work the way he can fit the job in, but SWMBO is at home, so he cracks on. The other half sends me pictures of the finished job and on the inside of the wall he's built up, where one of the windows were, there are a couple of concrete blocks bedded into it... It's not necessarily the end of the world, because it'll be getting plastered over, but I find it odd that someone who knows of all the benefits of using lime over cement, and has re-used clay bricks for the outside face of the wall, would stick lumps of concrete in too. The written quote clear states, "rebuild wall with bricks to match"... Small sections like this likely won't cause any long term problems, but it's sending my OCD wild. I haven't paid him yet, should I be standing my ground?

I'm considering buying a weather compensation kit for my system boiler. It's configurable and allows you to choose the curve required for your system. There are a couple of options; Curve 30 Outside Temp: 20c. Flow Temp: 47c Outside Temp: 0c. Flow Temp: 73c Curve 20 Outside Temp: 20c. Flow Temp: 20c Outside Temp: 0c. Flow Temp: 52c Curve 30 seems useful for the colder periods, especially for the upstairs rads until I fit IWI, but given I also use the boiler to heat our unvented cylinder, neither seem appropriate in the summer months. Ultimately, I hope to heat the hot water using PV in the summer months, so the boiler would be off altogether. In which case, is weather compensation actually that useful?

Interestingly, I've just had a fiddle with Jeremy Harris' heat loss calc, I included upstairs (radiators) and downstairs (UFH) and it's coming out at approx 17.5 kW (20c delta T). Perhaps that's more accurate and would be a better representation of the impact of installing given insulation. Boiler is set at 55, DWH is heating to 50. I've not checked for cycling when only the DWH is calling for heat, I'll add that to my list.

Where did you get those return valve settings and are they in litres per minute?

Great, thanks for those. Interestingly, those don't seem to match with what the UFH company sent me when purchasing my kit; The City Plumbing Heat Loss Calc suggests I need, on average 100W/m2. Which is works out at approx 7 kWh. Perhaps I need to leave it running for longer to see what the energy usage looks like once the slabs at heat for a period of time? I could live with 7 kWh until I get around to fitting the IWI!

I was rebalancing our UFH system yesterday after adding a couple of new loops, so they're ready for when the weather turns. It was running for a couple of hours as I was waiting for it to reach temp etc. We have 7x loops across approx 70 sqm (150mm centres), all are sitting on 100mm PIR, with 25mm perimeter strips and are connected as a single zone. The manifold is mixing to 45c by a gas system boiler with a flow temp to 55c (for hot water) and return was around 35c during this time (so certainly within the condensing range!). Loops are flowing at between 2 and 2.5 l/m in order to reach a 10c delta. All flooring is tiles and they peaked at 28c. I don't really want to go much higher than that. According to OVO, I was using approx. 18 kWh whilst the slab was reaching temp. That seems quite excessive to me. Am I missing something or is that just a symptom of our current heat loss? Internal Wall Insulation is next on my todo list, but the weekends seem to be getting away from me this year now!