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Wasn't sure where to post this but here's our observations after storm Eunice passed through. Initially we watched the storm gather, we could see that that the wind was strong but from inside there was no indication, no sound, no draughts. As the wind picked up something we were not expecting happened, we could hear and feel a draught. We have two fairly large sliders and at the peak of the storm, the wind was pushing against the slider so much that there was airflow between the slider and the fixed pane. Not much and not continuous but it was definitely happening. Our air test was done to passive standards (positive and negative pressure) so we're fairly certain there is no problem with the sliders because if there was then the negative pressure test would have exposed that. Anyone have a contradictory view? A short time later we had a power cut , that doesn't matter. The house is warm, the Sunamp is fully charged (minus two showers), what could go wrong? Well, we're fully electric so there was no cup of tea to sup whilst watching the storm play out. Information gleaned is that the power will be out for over 48hrs And of course there's no heating. But what does that matter because the house is toasty warm at about 21.5° and we've not had any heating on for days. And the house is almost airtight, apart from the few blasts that squeezed through the sliders. Thanks to @Adrian Walker's advice we have a CO2 monitor, well we bought a couple. It was quite amazing how quickly the CO2 PPM started to increase after the power cut. Obviously the MVHR was having a bit of "quiet time", so now we had a toasty warm passive house that was not working as planned. As night drew in it got worse because lots of candles were lit. The only solution was to open some windows and get some airflow. Out of interest, it was only the monitors that informed us of the poor air quality, it wasn't something we sensed. So, we have a toasty warm passive house but with no airflow so a couple of the 'tilt and turn' windows on opposite sides of the house were tilted. That fixed things, air quality wise, very quickly but it also meant the passive house was now going to cool down more rapidly than planned. There are no heating options, apart from the bio-ethanol fire) so we were getting ready to break out the cold weather gear. Fortunately power was restored about 12 hours after the cut. We have a fair amount of PV, and it was quite a sunny storm but of course the PV trips off in a power cut. We were meant to have a battery system but the that didn't happen. The M&E individual who specced that (and didn't provide) had wired in an emergency power supply from which we could run the fridge and freezer in the event of a power outage, which was a pretty smart idea, shame it never happened, but actually my advise to anyone building to passive standards, if they have a battery system then make sure that the MVHR will run off the batteries. That's the main thing we've learned. If you have built to passive standard and have a battery system, make sure your MVHR can run from the batteries in the event of a power cut, I suspect most battery systems will power an MVHR unit for ages. Without that, you're not in a passive house anymore. Oh, and we had the first BBQ of the season this evening. Bit nippy!

I am in the process of building a Passivhaus. As there is no gas, I will be using an ASHP for Heating and Hot Water. Heating will be via radiators located downstairs and upstairs. I am in the process of deciding between two Mitsubishi heat pumps - the 4KW QUHZ (CO2) which is matched with a Thermal store and the 5kw PUHZ which is matched with a Hot water cylinder. I have phoned up Mitsubishi and spoken to them about the QUHZ (CO2 air source heat pump). There is no additional maintenance required for the QUHZ. I also asked them about reliability and there view was that as they've had to increase the spec of the QUHZ in several areas to take into account that CO2 is the refrigerant so they expected the QUHZ to be as reliable or more reliable than the PUHZ. I think there is a big difference in the way that it heats up the water as the QUHZ uses a thermal store rather than a hot water cylinder used by the PUHZ. Not an expert in this area, but research I have carried out suggests thermal stores are less complex than hot water cylinders. Idiots guide from Mitsubishi was to use the QUHZ if your hot water energy requirement exceeds your energy requirement. Using the more detailed data for range of temperatures supplied by Mitsubishi the services engineer checked performance in PHPP for specific loads and temperatures for our house. It indicated that the heating is indeed slightly better with the standard unit but hot water is considerably better with the QUHZ which correlates with the feedback from Mitsubishi. These were both modeled at 45 C heating design flow temp and 55 C DHW supply temp. So on the surface it would appear the QUHZ is better suited to my needs. The only caveat is that it is a relatively new technology for Mitsubishi (introduced 3 years ago) and I think in the market place in general. I had an early condensing boiler fitted to my current self build and it was always breaking down, so I am a little cautious of using anything new on the market because of that experience. Heat pumps seem to be tried and tested technology however so maybe I am worrying unnecessarily. I would welcome any thoughts / feedback on this.

Hello all, I stumbled on this forum as part of a search for information about SunAmp batteries. I’ve spent a bit of time reading other threads on the topic and this seems to be a friendly and helpful piece of the internet. I’m on a quest to reduce the CO2 generated by the 3-bed 1960s semi (approx 98 sq m) where I live with my partner (no kids). We’ve insulated the upstairs, added some loft insulation, upgraded the double glazing and last year, we installed 5700W of solar panels and a Tesla Powerwall 2. I’d estimate we generate around 5000kWh a year from the panels, and export around 3000kWh of that. We’ve got our grid electricity usage down to about 500kWh per year. The biggest element of this being our electric shower (the Powerwall can only ever supply 5kW of the 10kW load). Gas is used for heating and hot water via a 15 year old Worcester combi-boiler - which I’m guessing is nearing end of life. Our gas usage is fairly low, but I’m looking to reduce that next, from the current 5000kWh per year (more when we have a cold winter). I'm not planning on replacing the gas boiler, meaning we'd be 100% reliant on electricity for heating and hot water. We’re on a deemed solar export tariff, and I’m looking to use as much of the energy generated as possible. I’ve also recently begun the switch to Octopus energy to take advantage of their Agile tariff, so it might be possible to shift much of our current gas energy usage over to electricity - but what would be best for us? GSHP not an option here (small garden) ASHP may be, but I’m conscious of the effort and cost of installing Underfloor heating. Air to Air an option? Right now I’m thinking a SunAmp for the hot water, or could the Uniq 12 supply our heating and hot water? Maybe we could supplement that with and a couple of electric radiators in the lounge and bedroom to keep us warm on demand? I’m not sure if that would be what we need especially if we have a long cold winter like last year (I’m on the South Coast of England). I would be grateful for any thoughts from anyone who has done similar or knows more than I do about these things. With thanks, David.

Hi, Since my parents moved into their new apartment, my mum has insisted in turning off the central ventilation system as she doesn't like the noise. I am sure it is partly also because she thinks it saves money and likes turning things off. Frequently I have gone to their apartment and found the air very stuffy. Today they called me and said that the CO2 monitor in their bedroom was red showing a high of 1664PPM over the last 24 hours and an average of over 1200. They haven't been feeling great for the last couple of days. Apparently my dad wanted to put the heating on and instead my mum closed all the window vents as she believed they were making it cold, thus the flat was totally sealed up. Would this CO2 level just be due to a lack of ventilation or should I worry about something else. They have been robustly told to stop closing all the vents!

I am finalizing my MVHR specification, having to self install, as there are no contractors who will fulfill my requirements (no surprise). I will be fitting 2 x Brink Renovent Excellent 400 Plus units with Ubink ducting. I have discovered that I can get internet connections for the MVHR units so I can do away with the 3 position switches/remote controllers and use a web interface/ app to control them. I will be fitting RH sensors in the extract ducting to auto boost the system, but I was wondering if it is worth including CO2 sensors also. The theory being that I could run the system slower than the building regs extract requirement with the CO2 ramping it up if required, the same as the RH. The building Regs extract requirement is the key as I have a large house 439m2 so this trumps any wet room extract rate. I have the following planned extract rates: 0 150m3/h Very low level for un-occupied periods. 1 320 m3/h lowest keeping room extract rates at BR requirements 2 495 m3/h floor area extract rate to comply BR 3 570 m3/h Boosted keeping the units within PH standards My original plan was to run the units at 1/2, depending on house occupancy levels with the RH boosting up to 3 as required, however with CO2 sensors I should be able to just let the system do it's thing. Do they work and are they worth it? (approx. £700 extra on a £10,000 equipment spend)