jack

We did that. Bought in 2012, knocked down and rebuilt during the course of 2015. My wife and I were discussing this just yesterday, and concluded that there's no way we'd be able to afford to do that in our area now. The same bungalow now would likely go for at least 30% more than we paid, and the cost of building has, if anything, gone up over the same time period. I suspect the numbers will be very variable depending on where you are in the country (or even within the same town).

There are also a couple of manufacturers that offer ducts with a flattened oval cross section. Useful if you want to run within a stud wall (as we did in places) or have limited space. Examples at the bottom of this page and here.

Great news that this is possible. Re: putting it in the attic, one thing to consider is access to change/clean filters. This needs to be easy to do at least a couple of times a year (we do ours quarterly or so). The (potential) worry with attic installations is that they're out of sight and out of mind. Maybe set a reminder in your diary? We went with a Brink Excellent 400. I'm not sure whether I'd do this again, as it was quite expensive relative to, eg, the Vent Axia Sentinal that I know a lot of people use. Our house is reasonably big (290m2) so that immediately knocked out a lot of smaller units. We were also considering Passivhaus certification, so needed a Passivhaus certified model, which further limited us. I second the vote for BPC. We didn't go with them in the end, but I had a long a very helpful chat with Gary at one point. Given we decided against PH certification in the end, I think we'd have saved ourselves a fair amount of money if we'd gone with them.

I've had friends of mine lose their heating and/or hot water in the depths of winter before. In some cases they couldn't get a heating engineer out for a couple of days. In at least two cases, they were then told that the parts would need to be ordered in, so they waited further days before they heat came back. I can't see that it's any worse for someone with a HA system. 95% of the system components - valves, pipework, thermostats, cylinders, manifolds - are completely standard and will be familiar to any heating engineer. All we're talking about here are a couple of relays being controlled by the HA system rather than a timer. It's a trivial matter for any heating engineer to look at a schematic and figure out where the likely failure is. If it isn't the HA relays (trivial to test), then it's somewhere in the rest of the system, which is completely standard. Of course, the HA system itself could fail, but that would manifest itself in many other ways as well. It's not that expensive to have a standby unit in the cupboard and a backed-up version of the HA software with current settings. Also, to repeat myself, I'm not suggesting this is general advice for anyone thinking about how to control their heating system. Alex already has the kit bought and installed. He's technically knowledgeable and knows how everything's set up. It just seems crazy to go and buy a whole bunch of other hardware to avoid using an existing system that's optimised for the task at hand. It's just more things to maintain and more things to fail in my view. Now if he didn't already have a HA system installed and ready to go, I agree completely with what you've said. There's no point introducing complexity and unfamiliarity for the sake of having it controlled by an HA system, unless it brings other advantages. Interestingly, I think that low energy houses are less likely to get a benefit from the flexibility offered by HA heating control, because often the system control is very simple (eg, only 1 or 2 zones to control, no need to have several heating periods per day with different turn-on times and temps).

These are real concerns Jeremy, I agree. But Alex has already installed a home automation system. In such a situation, it seems reasonable to me to use it, especially where the system involved is very well adapted to the type of application being discussed. We use our HA system for lights, blinds and UFH control, as well as monitoring some temperatures. I haven't bothered integrating it with the MVHR or ASHP, because the proprietary interfaces for those are ludicrously expensive (although I'll eventually end up controlling the MVHR speed setting by way of relays that close dry contacts). I've found myself very rarely having to access the app for Loxone, as most of the things I actually want to control day to day can be controlled by way of wall switches. The blinds are mostly automatic (all come down at dusk, some come up at 07:30, others - bedrooms, mainly - are closed automatically but opened manually by way of a wall switch). The lights are all controlled by pushbuttons in a fairly similar way to ordinary lightswitches, although I've set it so that turning on certain lights in the daytime will result in a higher light output than turning them on at night. I can check slab, air and DHW tank temps via the HA app, but this is mostly just because I'm interested, as none of those things are currently controllable via the app. Also, even if the the HA system itself becomes obsolete or the company goes out of business, the way the house is wired means that any other system could be transplanted in with relative ease. It's mostly just relays and simple programming, so not difficult to replicate in another system if ultimately required. I hope to get 10 years out of the current system. I have no idea what will be available then - with luck, HA will have become cheaper, easier and more secure by then. I don't know whether I'd bother with HA if I were doing all this again, but it is definitely very convenient for things like automatic external blind control.

Given how simple the control system will likely be, it wouldn't worry me that Loxone isn't an off the shelf controller. You can explain how it all works to a plumber in three mins, especially if you document it properly with a system diagram. Since you already have Loxone installed, and have the necessary relays free, presumably Loxone is also the cheapest option?

Welcome to Buildhub. Sounds like an interesting project.

Probably right. Always amazes me when amateurs are willing to buy at auction without a huge amount of research. If you're the highest bidder, it means that no professional is willing to pay what you're willing to pay. Fine if it's your dream home etc, but if you're hoping to make money...

Exactly. I still want to know where £313k went. Anyone want to take a stab at the internal area of the house and the size of the plot?

Amazing they thought they'd squeeze two semis onto that plot given how little space even a very modest 3 bed house leaves around itself. They paid around £313k to build that house. Seems a lot for what it is. I wonder how much all the "unforeseen" groundworks contributed to that? My gut feeling is that they've overcapitalised, because their idea of what was needed in a property to reach the "top" of the market (value-wise) in this area was off target. Interested in your thoughts on this @Ferdinand

Size isn't everything

Well don't keep us in suspense, how much smaller should you make them when there's UFH?

Ours was the same. Point blank refused to accept that a 5kW ASHP would be sufficient. He wanted to install a 14kW unit! From memory, his concern was that the house temperature would drop during the couple of hours that the ASHP would be in DHW mode each morning, and that the ASHP would struggle to catch up with that loss as the day went on.

Has always worked fine for me.

You definitely have the right attitude. I'm not for a moment suggesting you shouldn't research the hell out of things. If nothing else, you'll be better informed when things do go awry!

I truly, truly hope that's the case, but having been there, I can guarantee that there will always be unknown unknowns, no matter how much time you spend researching. I took heart from the fact that professionals who've done this every day of their lives for 20 or 30 years still overlook things or get things wrong. It's all about how you (and they!) bounce back from the inevitable mishaps. And welcome!

If you want to cool the slab, an ASHP is probably the only viable off-the-shelf option. I suppose you could provide the wiring and plumbing for such a unit and decide after you'v lived with it for a while whether you actually need/want slab cooling. In my experience, the only places that I've wanted cooling during the peak of summer is upstairs. Downstairs was always perfectly comfortable, but after long hot spells the bedrooms did get warmer than desirable at times. One thing I'd absolutely build in if I were doing this again is provision for insect screens on bedroom windows. At times last year it was a choice between being too hot and being eaten by mosquitos. Another option would be a fan - I lived in Sydney for years, and found that a simple pedestal fan was fine to make the temperature tolerable enough for sleeping, even during very warm weather.

We have Crosswater Mike taps through a lot of our house. Pretty happy with the quality after ~18 months of use.

Given PH levels of airtightness and insulation, I think it's reasonable to assume that there'll be a short heating period during winter, and an occasional use for cooling during summer (depending on solar gain - we got through last year reasonably comfortably without cooling our house). Between those, there'll be weeks, or more likely months, where the slab doesn't need to be heated or cooled. I'd therefore consider whether to make the system switchable between a summer mode and a winter mode. Given you only need to switch it twice a year, a manual switch would be fine. It might be as a simple as routing a call for <action> to either heating or cooling, depending on the switch setting. To be honest, you might not even need this given the way this sort of house reacts to changes in temperature over the year. Set up properly, I can't see a situation where you'd be calling for (floor) heat and then wanting cooling within hours or even days of that.

I should add, the sinus problems that have plagued me through much of my adult life have largely gone away since moving into a house with MVHR.

I've lived in a house with MVHR for over a year now and would never be without it. In your case, I'd be slightly concerned about how late the decision to add it is being made. Do you have a location in mind for the unit and associated manifolds? Is there space for you to run ducting to all the required inlets and outlets (as a minimum, usually at least one extract in each bathroom, the kitchen, and utility room, and one supply in each bedroom and reception room)? Where would your main inlet and outlet (through the roof or an external wall) go? These are non-trivial questions, but need to be given a fair bit of thought given the point you're at now.

These things work, I believe, by running a match filter on a code output by the laser, and adjusting a time offset until the match filter confirms it's locked. The distance is worked out from the time offset (=the round trip delay) needed to get the match. The high viz won't affect the round trip delay.

As a guide to longevity, Panasonic in the past has offered a 7 year warranty on ASHPs installed by certified Panasonic installers. Not many appliances give you that sort of warranty, and I think it gives some idea of what they expect from their kit in terms of longevity. ASHPs are basically large fridges. There aren't that many moving parts, and they've been around so long that the engineering is generally pretty robust. We went for an ASHP, but that was largely driven by the lack of gas connection and our speculation that we'd need to cool the slab in summer. That didn't really turn out to be the case in the end, as we just don't have that much solar gain. Do consider UFH pipework in the slab though. Running it for a least a few hours a day (especially when sunny) helps distribute heat evening around the slab. I suspect our kitchen would be intolerably hot at times of the year without this.

Size queen.

Yes. Someone with some sort of clue will be able to tell you how low on the tank you should consider fitting it. The Willis-type arrangement would likely be less of a faff.