S2D2

I've used these in a traditional loft space, if you apply attention to detail with the sealant covering all cable entries etc they give an airtight seal. Remember to seal the cable with extra slack so the downlight can still be pulled downwards if required. Unsure on your roof structure though as you should insulate above them.

I have the same setup, B&B floors with 50mm polystyrene, apart from one room with 50mm PIR instead. Probably 600+mm void underneath the floor though. The only sensible thing I've seen is the little spray foam robot you can send under which retains a ventilation gap, but that turned out to be prohibitively expensive. Watching with interest.

Thanks both, I'm no closer to clarification unfortunately, they're coming back next week though. To expand a little it's just a data connection I'm talking about, not power. Here's the installation manual: https://kb.solaxpower.com/image/68499e58090d4aafa0fb6d0545d4f2c1/2022-11-14/aceecfb2d55c951ce2334351692f3825.pdf The meter Solax sell comes with a CT clamp too, so it seems both are required not either. I had assumed the meter might have it built in: https://www.itstechnologies.shop/collections/solax-batteries/products/solax-chint-single-phase-ct-energy-meter And based on the installation manual it seems it can go anywhere between the household meter and the house load (consumer unit). No idea what he was on about with having to run a cable to the smart meter then.

Make sure the vents are taped over or something if the extractor has not been reconnected as even without a fan stack ventilation will be pushing hot, humid air up into the loft space. Rather typically when I went up to fit the new felt lap vents almost all of the condensation has blown off and dried up. We have had a fair bit more wind the last 24 hours but I'll probably have to wait until next year to see if the balance has been tipped back. A good airflow coming through the new vents though so they must be helping.

I've used these to good effect. However I topped up the loft insulation and the problem has tipped back to condensation like yours, so I've just taken delivery of a load more to try and get it sorted again. I only put 15 in first time. What has happened to the extractor vent that was connected to this pipe, is it now exiting directly to the loft?

Is the noise an issue or do you have them placed out of the way? I'm thinking about PV divert and have been looking at posts on these with interest. Useful info thanks @TerryE, trying to think how well this will work in the 90's house you mention at the end (but mine!). High thermal capacity still but larger temperature swings needed due to the much higher energy input.

Quick question on something my PV installer mentioned that isn't clear from the inverter installation manual: Is a hybrid inverter plugged directly in to the electric smart meter for the property or is there just a CT clamp anywhere on the tails before the consumer unit? The installation manual for the Solax kit suggests either is posible but it seems to suggest a connection to a second meter installed before the consumer unit rather than just the household smart meter. The installer suggested a direct connection to the smart meter (though it was ambiguous, I will clarify when they come back) which would be a much more convoluted route and likely leave a lot of ugly trunking in the garage. Just wondering if this is normal or not? Thanks

Octopus currently pay 15p/kWh, so more lucrative than offsetting gas (for now).

May be of use. The in-line shutters are audible when it's windy (they don't stop hot air being sucked out), even when fitted close to the roof outlet. I would say subjectively though that they are effective, so have left mine in for now.

I think it just determines drying speed past a certain point. For example, my dehumidifier has a laundry setting which goes full blast for six hours with a target humidity of 35%, idea being you shut it in a small room. I don't use this as I find just leaving it at the standard 55% with doors open dries plenty quickly enough, maybe 12 hours? The dehumidifier is right next to the clothes and spikes to 70something when they first go out. Clothes feel bone dry by the time it's back to 55%.

Quote seems a couple of grand heavy, might be worth getting a few more but prices are getting a little daft atm. Remember it includes a whole bunch of other kit, mountings, cables, scaffolding etc. And will give you an MCS certificate to get paid for export. Even with your high usage you may end up exporting a fair chunk.

The idea being (I think) you can convert the outside air to absolute humidity then calculate the relative humidity once you have raised it to internal temperatures. This gives you a "best case" relative humidity if you were to add no moisture at all. I think in your case it comes out at 72%, you are adding 9pp from somewhere which seems perfectly within the bounds of evaporating construction moisture or even just general household usage. Heat the room or run a dehumidifier and it will stabilise. I've been looking at this on our house and we were sitting about 13pp above best case humidity due to drying clothes etc. Dehumidifier reduced it down to 55% within a week.

The £650 application fee for G99 (depending on location) is a big disincentive. OP may have split panels East/West or otherwise not optimally placed which mean gains from upgrading would never pay this (plus the inverter upgrade cost) off. All depends on individual usage, it is a shame a 3.68kW inverter wasn't put in originally though.

Doesn't sound normal to me, suggests a very quick air change with outside air. A wireless thermometer would probably reveal the source, check window vent, sockets, light fittings etc.

I've used loft legs, the XL version and they worked very well. Shouldn't be too expensive if you buy by the box rather than individually. Remember they can be spaced at 600mm along the joists, but yes the 400mm joist spacing will increase the number required in the other direction. Use the expensive screws which don't require pilot holes and self countersink, they pay for themselves in about five minutes and make the job very quick indeed.

Calibrate beyond a fixed scaling? I can use that for a certain device but I presume it will be different between devices?

Annoyingly I've been using a Meross equivalent for this but after recently comparing with real time smart meter readings, I've discovered they're giving a reading of 200W for a dehumidifier which is actually drawing 160W. Pretty useless then. Are the above more accurate?

+1 for LVT, I used quick-step and I'd do the same if I did it again.

Assuming a loft installation your only real option for a standard house design is the upstairs landing. It is not silent so you don't want it in a bedroom and you want to create a pathway from input to extract, usually in bathrooms, so it can't go in those either. You can usually get quarter baffles to stop it creating a draft in a particular direction if it is at normal ceiling height and one aspect gets more usage than the others.

Yes I haven't done the calcs just rounded up, it does seem to be a suspiciously linked rate - I guess they want to incentivise against gas offset otherwise they'd have less export to sell off and so less clout on the market. I guess the innocent explanation is just that gas and elec rates will always be linked at around these ratios. From an eco perspective I'd rather offset gas usage but will save the hassle for when rates drop.

I use this setup to good effect. It depends on airtightness, ours is too poor to warrant MVHR running costs (probably, based on many assumptions...) Unsure on building regs, our last house was a new build with PIV and no trickle vents so it's possible.

Whilst usually true, I assume this is an MCS install so eligible for the current 15p octopus outgoing export rate vs ~11p gas offset? Obviously this rate can disappear overnight so an immersion divert may be a longer term plan, especially if it's part of a negotiated recompense as suggested above.

Interesting figures, I recently looked at this on our house with 13 months of DCC smart meter data compared against heating degree days from a local weather station (https://www.degreedays.net/). Regression fit for input kWh to degree days, input both with and without hot water (some energy lost to the drain). Came out somewhere between 4.1 and 4.7 kWh/hdd. This is a mid 90's house with some insulation everywhere, but nowhere near modern standard and poor airtightness. It'd be interesting to get a range of figures from different types of housing. Also, the point of me doing this is that you can use the average forecast temperature for the following day to work out how many kWh heating will be required the following day, allowing a PV divert to power a heater without over-heating the house. I'm yet to get this set up and am unlikely to bother until export rates drop as my heating is still mains gas.

I installed something like this as an experiment at the insulation layer of a duct run and unsurprisingly it makes an annoying noise when it's windy outside. I will move it to after the inline fan and report back if it's still a nuisance. Sadly a 100mm pir plug is not suitable, no matter how effective!

I was surprised when I checked the agile rates and they'd dropped so soon after the 15p fixed increase so maybe it's just a blip, depends how many of their customers swap over I guess, probably most will ride it out. I had assumed rates would stay high for two years. End of the day it only makes 2 years difference to the system payback so not a major issue. I don't have time for the power cut scaremongering, nearly laughed at the solar installer when he offered a £1k upgrade for an off-grid switching system, we'll do just fine without.