jack

I seem to recall that OP is in France.

Hi @EmmaSp, welcome to BuildHub. I see that you've posted the same question in the "House Extensions and Conservatories" sub-forum here: To avoid splitting answers across two posts, questions should be posted only once. I think the "House Extensions and Conservatories" sub-forum is the more appropriate of the two you posted in, so I've locked this post. People can find the other one by following the link above.

Welcome John. A couple of pointers: - add the term "Buildhub" to a Google search to find info on the forum - if you have a question, drop it in the relevant sub-forum for the quickest reply. As to what not to do, just use your common sense and I'm sure you'll be fine. Plenty of the regulars have no common sense at all and they get by.

I'm in the southeast and we get the occasional one - maybe once every year or two for 1-4 hours.

Hi tomaus Welcome to BuildHub. It's generally best to post specific questions in the relevant sub-forum, as not everyone monitors the Introduce Yourself sub-forum. In this case, this is the right place to post your question: https://forum.buildhub.org.uk/forum/79-mechanical-ventilation-with-heat-recovery-mvhr/ Any drawings, photos, or details about when and how the problem happens will likely help you get a better/faster answer. For example, when you say the "intake" circuit, do you mean this is a vent that extracts air from a room?

We're just doing it (without going crazy) because it seems like the right thing to do. If you were really struggling and your usage pattern allowed you to significantly reduce usage at the right times, being able to make a couple of quid here and there wouldn't hurt.

As well as that, I have quite a few of my downlights set so that they're driven to no more than 80-85%, in an attempt (possibly misguided) to make them last longer.

Also, some MVHR systems adjust per terminal airflow at the manifold. If you have such a system, you should have all terminals wide open while you get as close as you can by adjusting airflow at the manifolds. Once that's done you can make fine adjustments at the terminals if needed.

Absolutely. Plus more people means more incidental heating, particularly from showers, but also things like PCs and other tech used by occupants.

I think you're right about ratings. They're usually the highest output you can expect, which will generally be when it's warmer outside and you're generating relatively low temperature water. I have a 5 kW unit. With a well-insulated house, I never particularly felt the need for anything bigger until the cost of electricity went up and we went onto Octopus Go. On very cold nights it's realistically going to be more like an average of 3 kW when you take the lower output and periodic defrosting into account. Stuffing all of our expected 24 hour heat loss into a 4 period with Go isn't realistic, especially when I'd ideally like to also heat up our hot water tank at the end of that period. Realistically, a more powerful heat pump would give me more options. I may think about that if and when the current into needs replacing.

As I understand it, all houses require it. It's possible there's level access around the side/back where you can't see it - it just needs to be accessible from a parking spot. There's no requirement for you to maintain level access, only for it to exist at the time it's signed off. Do something cheap and temporary. Get hold of some bits of wood and build a ramp on top of what's there. Or lay plastic over your existing ramp, and lay down some cheap (even second hand) pavers in a weak concrete mix (or even just siliconed/glued to bits of wood of the right thickness underneath). Be creative - you might do it for something close to free. We did something similar with ours when the inspector noted the absence of level access on his final visit. We bodged something up with some concrete council pavers we had lying around, sent him a photo, then dismantled it as soon as we got the certificate.

It's a huge shame about the last minute delay (and other challenges along the way), but your parents must be chuffed to bits with the result. They should be proud of you.

Report the post, then in the comments section of the report say that you'd like it deleted/edited. One of the mods will take care of it.

We were advised to ask for 8.5 kW (the most we could fit on the roof) 7 years ago, and it was granted without question. I was surprised. Wow, is that typical? I mean, it's been an awfully long time since we applied (mid-2015 I think), but I don't recall paying an application fee.

Our plant room walls are Fermacell. Annoying to fit, but very strong, and allows some quite heavy things to be mounted to it without the need for a plywood backing. I think a single screw can take something like a 30 kg vertical load. I've never had anything move once screwed to Fermacell (we have it in some other places in the house too). Floor is cheap cork tiles (on sale at Wickes when we bought them) over concrete. Do think about having both heat and smoke detectors installed.

Does your heat pump have a sump warmer or a drainage tray defrosting circuit? Both of those will use resistance heating.

At 327 W average, this is less than the average by which I reduced my energy consumption during this trial (bearing in mind the issues I had with my wife choosing this period to do vacuuming etc). And that's for 300,000 homes - there are 25 million homes in the UK, so we'd need 75 of these installations to provide the same level of storage for everyone. Fair bit of time, resources, and money required before we can get anywhere near that level of storage. As I've said before, I'm firmly in support of building out storage. Unless and until we do that, reducing energy consumption is one thing we can do to improve the situation. All we seem to be arguing about is whether there's any point trying to get people to reduce their consumption when peak consumption overlaps with reduced output, and if so, how.

That number is what I saved on that particular day. Why are you extrapolating that number to the rest of the country ad infinitum and assuming it will stay like that no matter how the implementation changes? This isn't "the long term solution". It's an experiment around one particular element.

Again, that's not the focus of these sessions. If you want to discuss total energy consumption, this isn't the thread. Exactly. And when there's predicted to be a period of low renewable power available relative to demand, reserve capacity is expected to be placed under strain. I assume that making up the anticipated shortfall requires importing expensive energy from other countries and/or firing up dirty sources such as coal plants or diesel generators. You can see on gridwatch that the average contribution from wind power (light blue) has been falling continuously since yesterday: We were exporting energy to France until just after midday today but now we're importing. I haven't looked at the rest, but it's clear that local/cheap capacity is already starting to come under pressure now, wind output continues to fall, and the evening peak period is still hours away. Let's see what happens between 17:30 and 18:30 tonight. Decades is a long time to operate a system that according to you doesn't work.

You keep analyzing this trial in terms of total energy saved, but the explicit aim is to reduce consumption during peak periods (presumably at times where there is predicted to be lower renewable energy available), not save energy in absolute terms. Also, I'm surprised that a scientist is so negative about doing preliminary experiments to see what happens. This isn't the end, it's the start. If the experiment proves successful enough to go further, then they can try adjusting charges, incentives, periods, etc, to see what works best. If it doesn't, fine, they know what doesn't work and maybe they'll try something else. People understand money, not kWh.

I have absolutely no idea what's going on. £1.11 is roughly half a kWh, which suggests an average of 2 kW during that period for the previous 10 days. The heating and DHW aren't on at that time of the day, and a lot of the time we don't start dinner until after 18:30. I know there was a bit of unusually-timed car charging in the preceding week, but 17:30-18:30 is still an unusual time for us to have been using a lot of energy. I may dig into the numbers when I get a chance.

Correction: I can only assume we managed this because there was a lot of cooking going on during this period in the lead-up to the saver session. Let's see how tonight's session goes. We're using the slow cooker during the middle of the day while the sun is out, so hopefully we can beat the number above.

Welcome to my world. Surprise, surprise, but it appears we didn't get a payment for the last one. Will see if I can do anything about tomorrow (possibly helped by the fact that our atrocious result during the last period will contribute to the average against which the next one will be measured).

Given your budget, have you ever considered doing something smaller but higher quality? I know some people on here don't like architects, but the right one working together with a good interior designer and landscape architect could potentially give you a barn conversion that would be an absolute joy to live in. Think along the lines of better fixtures and fittings, hand-crafted built-in furniture where appropriate, a proper budget for interior design and the garden - all the stuff that people working to (and often beyond!) an already tight budget often don't have the luxury of considering. You mentioned in your first post that there was more than one barn. I'd also be thinking about smaller outbuildings for things like a garage, gym, workshop, storage, etc. Friends of ours have a small barn in their back garden with a kitchen, pool table and big TV. They use it for entertaining, parties, their kids having friends over - all sorts of stuff. Personally, I'd rather a perfect 300 m2 house than a 500 m2 house that's just good. @Ferdinand might have some thoughts.

I increased my temps slightly, and have increased temperature compensation. From memory, I now have something like 26 ºC for temps above maybe 8 ºC, with weather compensation kicking in below that to a high of 29 ºC as the temperature falls to around 0 ºC. I'll likely be increasing these temps a bit further now that I'm going to try squeezing more of my heating into the Octopus Go cheap period. Also, it's worth bearing in mind that the ASHP stops heating when the return temp reaches the flow temp. That will be well before the slab temperature reaches the flow temperature. I know you're saying this approach to heating puts a cap on room temp, but unless there's a lot of solar or incidental gains, the room temp is very unlikely to reach anything like the flow temp. As an example, I ran our ASHP open loop through two winters without a thermostat (just relied on flow temp control), and I don't believe we ever got the room temp above about 22 ºC. True for high humidity at low temperatures, but when it's mild I assume higher humidity also means additional efficiency due to energy gained from condensation of water vapour. Presumably there's also energy extracted from the phase change to ice, but that's more than balanced out by the corresponding need to defrost.