jack

Interesting stuff John, thanks for sharing. I've long had ideas about doing something similar but I doubt it'll get to the top of my to do list until a couple of years into my retirement (the start of which is still way too far off for my liking).

I feel bad for desparately hoping for some proper rain in the South East. It's been painfully dry for months, and the couple of small recent downpours have not been sufficient to convince the mushrooms to pop up yet. I did find my first mushrooms of the year today though - oysters on fallen scots pine.

I just noticed no-one actually tried to answer any of your questions. I'll give them a go. I haven't quite done exactly what you plan, but I did handle the MVHR penetrations during the build and have run various additional cables etc over the years, through a very similar structure. How did you detail the penetration through the OSB airtight layer? Cut a slightly undersize hole in a piece of membrane (thick plastic sheet or film is fine) and push the conduit or whatever through it. Seal the edges of the membrane to the OSB with airtightness tape. Cut the membrane square even for round conduits - much easier to apply airtightness tape in a straight line! Did you use proprietary airtight service grommets/collars or tapes around the pipe bundle? Generally not. They're expensive for what they are. At different times I've used offcuts of EPDM and DPM I had lying around. I've also used neoprene insulation a couple of times for cables. For example, I used a disc of thick neoprene insulation to run satellite cables through a snorkel on the roof, where I didn't want to disconnect the cables. I cut the disc a little oversized for the inside diameter of the snorkel, drilled some undersized holes through it for the cables, then cut from the edge to each hole. Slid the cables into the holes through the cuts, then slid the disc along the cable into the end of the snorkel. Neoprene is closed cell, so it was perfectly airtight. It's not a bad approach for running cables. Is it better to install a larger airtight sleeve through the wall and pass all the services through that? If I understand what you're saying, probably not. It's straightforward to seal a single cable, conduit, whatever, passing through a penetration. It's really hard to seal multiple cable etc passing through the same hole. We have one penetration like that, from the house into the attached garage, and it's a hideous nightmare that's probably responsible for half of the air leakage in the house. I suppose you could have one larger airtight seal over multiple holes in the OSB - if that's what you're saying then I think it'd work fine. How was the sleeve/penetration dealt with at the breather membrane and external cement board? Same as on the inside, but use membrane similar to whatever is currently in place. You could use non-breathable if that's all you have (e.g., just repeat what you did inside), as long as it's resistant to damp and whatever UV it might be exposed to. How did you deal with the condensate drain without creating an air path? We didn't have to do this, but consider whether you can run the copndensate drain to an internal drain. Alternatively, you could use a dry trap. We have one of those under our MVHR and it's worked fine for 11 years. Would you pressure-test the house again afterwards to confirm the airtightness hasn't been compromised? I wouldn't. Just pay attention to the detailing as you go and it'll be fine. On the underfloor cooling, we have a very similar Panasonic ASHP, probably an earlier model of what you have. It's very effective downstairs, but makes only a modest difference upstairs. Personally I'd consider installing aircon upstairs first, and seeing whether you can get away with mild underfloor cooling downstairs. It helps a lot if you have hard floors - tiles and concrete (we have the latter) are ideal. Not sure whether I'd bother if I had a lot of carpet. With wood floors, I'd be extra careful about making sure the temp is below the dewpoint. We had an incredibly humid couple of days in one of the hotter periods earlier this year, and we had literal wet patches appear on the surface of our concrete floors over the course of one day. They disappeared overnight. I think the floors were probably only a couple of degrees below the dewpoint. I'm not sure I'd have been happy having that with wood floors, even if this is the first time in 8 or 9 years of cooling that I've seen condensation.

We have an 11 year old Brink Excellent 400, and the criteria are similar (with the possible exception of the first one - I don't recall seeing anything like that in the manual). I seem to recall that some of the settings are adjustable.

That isn't how/when summer bypass mode works. Most (all?) MVHR units with summer bypass should switch to bypass mode only when it's cooler outside than inside, and only when the temperature is above some threshold (to avoid it coming on in winter). Even during a run of hot days, it's a rare situation in the UK when the overnight temperature doesn't fall significantly below the interior temperature of a typical house. It's therefore worthwhile to use summer bypass, especially if you don't want to open windows overnight (due to, e.g., insects or noise). Maybe it's of less use in Scotland because the interiors of houses don't get so hot in summer, but where I live, our bedrooms can reach 30 deg C, even with the underfloor cooling working downstairs. I see no reason not to use every available trick to reduce temps overnight. The one thing I haven't managed to get around to yet is to control the MVHR to boost during the cheap period when conditions are such that summer bypass will be in effect.

I should add that she was a lot more stoic about it than I would have been.

My wife was out doing some weeding a couple of years ago and didn't realise she was swinging a hand-held weeder into a bank right beside a wasp's nest in an old tunnel of some sort. She got stung three or four times in quick succession - nasty little blighters!

We have untreated Siberian larch. Wasps definitely use it to build their nests - up close, you can fine marks where they've scraped the top surface. They haven't managed to damage it much after ~11 years, so I'm not that worried about it. I assume a well-maintained coating would deter or stop them.

Do as I say etc. I can't tell you how much time I've wasted over the years trawling through poorly categorised photos of the walls before plasterboarding.

Missed this on my previous reading of this thread. Sounds like a great idea.

Welcome Matt. When posting about your idea, please keep in mind the commercial posting restrictions on the site. Fine to discuss ideas - not fine to share commercial links or invite/encourage people to use your product/services. Basically, if it feels like advertising, it'll be deleted. Other than that, crack on.

Thanks @Nickfromwales No point replacing the elbow if the waste outlet turns out to be the problem. I'm flat out today but I'll take a look when I can.

Thanks @Nickfromwales This is the joint: https://mcalpineplumbing.com/plastic-chrome-fittings/multifit-waste-fittings/135-universal-bend-x-bsp-coupling-nut/ The end that's leaking is the BSP joint at the waste outlet. I'll take it apart again later and check more closely for damage at the waste (the elbow itself looked fine). All I noticed when I first took everything apart was a short bit of thread missing at the lead-in end of the threaded waste outlet.

We've had a leak underneath an upstairs shower for a while now. I've finally gotten around to opening up the ceiling underneath and having a look. There's a 135 deg, 1 1/2" BSP to 40 mm compression elbow coming straight off the 1 1/2" BSP outlet from the shower waste. Based on the muck around it and how clean everything else was, it's clear that's the source of the leak. The BSP nut was very loose - I had to turn it nearly two turns to tighten it up. I hand tightened it up as firmly as I could and tested: immediate leak. Dismantled and pulled out hair, gunk, etc from the shower waste outlet, then cleaned up the fitting and connections as best I could. Installed again, firmly hand-tightened everything, tested: immediate leak at BSP joint. What would be your next step? My first thought is that the rubber washer's hardened over time, so replace that and see what happens. Anything else to look out for? Should I go for the same square section washer? @Nickfromwales, tagging you in for visibility. Thanks.

I bought a cheap Erbauer one in mid 2015. I've told the long story before, but the short version is that the window installers massively stuffed up by not packing the windows up by 15 mm as shown in the drawings. When they went to install the cills, the outer edge of the reveal held the cill up almost horizontal. I bought an Erbauer oscillating tool and some blades, and spent hours - maybe a day more - trimming the reveals to allow the required fall. (Upon reflection, there was probably a more efficient way of doing this, but nothing else occurred to us at the time). By halfway through, the grease in the gearbox had liquified and leaked out everywhere. It got louder and louder, and the vibrations were horrible, but it kept going and got the job done. I've used in many time since and it still keeps going. I actually had it out on the weekend to move a smoke alarm in the kitchen, by going in through the floor above. Still produces insane amounts of noise and vibration, but other than that works perfectly well for the sorts of things I need it for. I'll use it until it dies.

Not a realistic option at the moment, but: https://en.wikipedia.org/wiki/Atomic_battery

100% agree.

I'm more than happy to have turbines near me. I've had plenty of conversations with friends who feel the same. More to the point though, building more in England is unlikely to change the number being built in Scotland. If you think there are too many wind turbines being built in Scotland, that's something to take up with the Scottish government.

https://www.instagram.com/reels/DOd5v_yiL4E/

Fixing it in the open position will guarantee to make your house hotter during the day. Bypass should only be used (and should automatically turn on) when the outside temp is below the inside temp. Your MVHR shouldn't ever be delivering 31 deg air. In normal, non-bypass mode, the MVHR will work to maintain any existing temperature difference between inside and outside. In summer that means it will transfer most of the heat from the incoming air to the outgoing air, significantly reducing the temperature of the air delivered to the house. So if it's 30 deg outside, and 20 deg inside, the air delivered into the house will be something like 22 deg, depending on the heat recovery efficiency of your unit. Summer bypass only comes on when it's cooler outside than inside. Depending on the unit, you might be able to adjust the temperature at which it kicks in. To maximise effectiveness: Reduce airflow when it's really hot outside, cooler inside, and you want to minimise incoming heat. Turn it off if you like, but you risk a stuffy, humid house. Personally I'd avoid that. Summer bypass won't operate in these conditions. When the temperature outside drops below the inside temp and summer bypass kicks in, bump up the flow rate to maximise purging.

I've deleted the duplicate post.

Any particular reason to place this upstream of the MVHR unit? I may be missing something, but this way you'd lose some of the "coolth" through heat exchanger inefficiency. That inefficiency could potentially be worsened by moisture in the outgoing air condensing due to the cold incoming air.

Generally yes, but only if humidity is lower outside than in. Where I am, humidity is still high, and is forecast to rise through the night into the high 80s. Thankfully it should drop a fair bit through tomorrow.

I lowered the flow temp on our underfloor cooling from 16 deg to 14 deg a few days ago, in anticipation of the several day heat wave. The surface of the door (polished concrete) slowly fell to a minimum of 18.7 deg a couple of days ago. It's slowly drifted up to 18.9 deg since. In the middle of the afternoon today, I noticed some darker spots on the surface of the concrete. Within three hours of noticing that, entire sections of the floor in the kitchen were slightly damp. We've never seen so much as a whiff of moisture in 7 or 8 years of using underfloor cooling. It's amazing what a two degree flow temperature difference coupled with high humidity (~80 inside at the moment!) can do. I've turned the flow temp back up and will monitor.

You need some ventilation even when everything is closed up. Draughts will do it if have a draughty house. MVHR is a way of providing that ventilation without bringing in full temp air from outside to replace your precious cool air. As noted, MVHR isn't 100% efficient. I tend to keep it turned on as low as possible during weather like this, as that reduces the losses in absolute terms (i.e., you lose double the amount of energy with the same 90% efficiency if you double to airflow).