jack

In a way, this sounds to be less an air exchange rate problem, and more an issue of internal air paths. I guess the paths are too difficult to model (especially given the different ways in which people use houses) so the simplest solution is to increase ventilation rates.

This is in houses to current regs without MVHR though. When most of us talk about "beyond regs" levels of airtightness, we're generally talking about implementing MVHR at the same time. I assume the main concerns with moisture are the interstitial kind, rather than the "black patch in the corner" that you sometimes get on external walls of poorly insulated houses?

Genuine questions: are these "leading experts" all unbiased researchers without links to large builders? Do you believe that the sole or dominant reason for stopping here is that independent experts have concerns? And while the rules may in theory be strict, do you believe that when a developer builds 10 or 100 or 1000 houses, all of them are built to fully meet the regs?

That may well be the case, but the story Jeremy relayed was that the surveyor specifically told him that "eco" houses, such as Passivhaus standard houses, were worth 10% less because the eco angle put people off. Nothing about the construction method (although that may have framed - pardon the pun - the surveyor's thinking). I tried to find the thread over on ebuild, but it's tough given he had nearly 11,500 posts!

I'd love to hear more about this. What little I've been able to find in the past suggested that UK regs ventilation rates actually resulted in too much air exchange, leading to unduly low levels of moisture during dry winter months.

I agree completely. I treat PH certification as being something like very modern design. It may well put off a lot of people, but it's just as likely to spark greater interest in at least some of those who aren't put off. Whether that impacts the final price is probably very situation dependent.

I don't think there is any, at least relating directly to PH certification. I think there's just anecdotal evidence that some surveyors will downvalue anything holding itself out as an "eco" house. I believe Jeremy Harris had that experience. I seem to recall someone else saying that PV can reduce the value of a house even if it's still going to have a cashflow associated with it for the balance of the FiTs contract. Here's feature that could give a windfall of thousands of pounds over the next 20 years. How much value do such people place on that feature? Negative thousands of quid! Bizarre. I don't believe the word Passivhaus by itself is a trademark. From memory they only have a trademark on the logo. There may be a question over whether the word "Passivhaus" is confusingly similar to the logo. Even if it is a trademark, to infringe you'd have to be using it in the course of business. A private individual can therefore describe their house as being of "Passivhaus standard" or "designed using Passivhaus principles", because that description isn't in the course of business. A developer, on the other hand, can't use such a descriptor when selling their houses unless they meet the standard AND have the certificate from the PH institute. The latter would effectively be a license to use the trademark. Irrespective of the TM position, you may be committing fraud if you're holding out that your house meets a standard when it doesn't (edited to add:) and you get some sort of financial gain from that assertion. Incidentally, the PH Institut had a big falling out with their US branch a couple of years ago. From memory the US branch ended up getting the rights to their US trademarks. It was all pretty nasty!

We did the same a couple of years ago. Adam and his family are lovely, and he's extremely knowledgeable (having co-written the Passivhaus Handbook). Worth the cost of staying just to pump him for info! I wonder whether we need to agree on what you mean by "Passivhaus". As you know, technically it's a (very!) detailed standard that a house can be built to meet. Everyone talks about airtightness and insulation, but there's a lot more to it than that if you want to go for certification. It sounds like what actually concerns you is a house having high levels of airtightness and insulation. On airtightness, as others have said, there's absolutely nothing to stop you keeping your windows open whenever you want to. We've only this week started closing windows in our Passivhaus-level airtight house - we typically leave loads of windows open upstairs through the shoulder seasons, and only close them in summer once the temperature outside gets higher than what's inside. The thing is, building airtight gives you options. If we have an extremely cold, wet and windy period and you need to keep windows closed, then you'll still have great air quality. If we have a hot period, you can close everything up, leave your MVHR on summer bypass, and hopefully keep the internal temperature low relative to the heat outside. If you don't build airtight, you don't have these options. Regarding insulation, even a building insulated to current building regs will overheat if it isn't designed with proper regard for solar gain. Get it right and your house won't overheat. In our case, we have around 500mm overhangs on most southern and western windows. We have a 5m long, 2m high slider to the south that gets quite a bit of sun through the middle of the day, because we don't yet have any external shading in this area. We also have external blinds on most southern and all western windows. We had a few days over summer where it was warmer inside than I'd have liked it, especially upstairs, but I'm doubtful having less insulation would have made much difference to that. That article repeatedly refers to things like poor positioning of vents and poorly designed systems that make fan noise noticeable even on the basic setting. If your MVHR system is designed and installed properly, there's no way you should hear anything meaningful on the basic setting. You might hear it a bit on boost, but that would be the case with a regular extractor. Same with vent positioning and flow rates - these are within your control. If you don't want to build to PH standards, that's cool. I personally think they're a little over the top in terms of the energy requirement, in particular. But don't compromise your one opportunity to build a really comfortable house based on misconceptions like not being able to open windows if you want to, or that adding more insulation is what causes overheating. Edited to add: I now wouldn't live in a house with a dog unless we had MVHR. I'm very sensitive to smells, and our house has absolutely no dog smell about it, despite us having a very energetic springer who goes paddling in the local stream twice a day when we take her for a walk.

Safe word?

As long as "moderating" is not some sort of codeword you use on your, erm, private forum.

It's all down to what the network in your immediate vicinity can handle. Having other PV installations nearby can affect this. We applied for, and were granted, the right to install an 8.5kW array in an ordinary suburban area. Took longer than expected (something like 7 weeks instead of a month? Can't remember!), but was granted without comment.

Welcome, looks like you'll fit in fine

Agreed there's nothing at all wrong with the Pi! I love Pi! Absolutely. I'd never for a moment suggest going and buying something new when you have something perfectly useful sitting there ready to go. I was specifically responding to Steamytea's comments about the difficulties of getting a Pi to run reliably for months. In these "embedded" type situations, there's a lot less to go wrong, stability-wise, with a microprocessor that isn't running a general purpose operating system. That's basically the end of my understanding (I hesitate to use the word "knowledge"!)

Pardon my ignorance, but wouldn't something along the lines of an Arduino would be more suited to this kind of long-term task? (Not saying PeteW should have gone and bought one just for this task since he had a Pi sitting around - I'm more asking in case someone comes along and is inspired to try and do something similar).

Welcome! We have an MBC house with a completely flat roof south of Farnborough. We have 400mm of cellulose insulation and there's no way you get enough heat through that to cause overheating. Do think carefully about roof structure. In the end we went for a cold roof with cellulose. If doing it again I'd go for a warm roof, possibly with rigid insulation. I'd also consider going for fibreglass rather than the high tech German EPDM/modified bitumen system we went with (although that's largely driven by dissatisfaction with the way it was installed)

I agree. However, this is something I know MBC are aware of following a spurt of growth in the last couple of years. Unless something's changed in the last few months since I spoke to one of their senior guys, the actually reduced the number of teams they had late last year and slowed down taking on new work. I don't know whether they'd reached a point where quality was actually suffering, but I was heartened by the fact they were addressing the issue proactively while their reputation was still good.

I had the same reaction as Nick - if not spam, at least an unusual posting of a link to a commercial blog in a first post. I let it slide, but mainly because I'm scared of confrontation

Yes, I remember the post. Just making the point that there may be more to it than being on sand. I don't doubt that what Hilliard specs will work - my limited understanding of this type of system is that it's pretty robust, and there may be several ways of deep-exfoliating the feline.

Interesting. We're on almost 100% sand and he specced no fines.

I think we're pretty relaxed about genuine recommendations from long term contributors like you Vijay.

If you go for railway ballast, make sure you specify the cleaned stuff (I think they steam clean it). The stuff we got hadn't been cleaned and it was a bit greasy/grimy in parts. Unfortunately, it was delivered and laid on a day I was at work, so it was too late to complain at that point.

This sounds a bit like what we used to do when it was too hot to sleep in Australia - move to the lounge, which was the only airconditioned room in the (largely uninsulated, timber framed) house. This is basically the same idea, but with insulation. And yes, the house was ice cold in winter (this is in Sydney's far western suburbs, which are hotter in summer and colder in winter than central Sydney).

We're still under some sort of hybrid site/buildings insurance. We're trying to get our completion certificate by Christmas. Until that's issued, we can't get normal house insurance.

I tried once. We had a couple of specific areas where we wanted some ideas and help. We took the guy through the house, showed him the problem areas, told him we were on a tight budget, and gave him links to our Pinterest light boards. He came back after two weeks with £9000 worth of light fittings for one of the areas. It was very nice. I never contacted him again, and he, quite wisely I thought, didn't pursue us for part of the few hundred quid he'd suggested the whole process would cost. I don't doubt that working with the right lighting person would be absolutely awesome. The problem is getting someone who can do something interesting without immediately reaching for coloured LED strips in cove lighting (fair play to you if that's what you like - it's clearly very popular - it just isn't my cup of lapsang souchong). One thing we've done in some of the public areas of our house is use wall lighters. We found some modest, relatively reasonably priced lamps that provide enough light to see by while giving, we think, some atmosphere. The other thing is to consider using 5 amp circuits and/or home automation to easily allow the use of secondary lighting such as lamps and wall lights. Personally, at night the last thing I want on is downlights, so in our house, they're secondary lighting in most rooms!