Jeremy Harris

If you do have to fit a vent pipe up through the heated envelope of the house, then worth looking at insulating it as well as you possibly can, as it will be a pretty effective "cold air chimney" that will act as a fairly significant thermal bridge. It's the primary reason I didn't want to have to fit one. In our old house the vent pipe runs in a boxed section in the bathroom and where it runs is always where condensation forms, as the damned thing is always cold.

Is it really a crack in the hull? If so, then same question as Dave, how's it still floating to its lines? I'm wondering if it could be a twig from that branch, rather than a crack - it's hard to see clearly from the photo, but right at the waterline it looks a bit like a twig.

I agree about service voids, we have them on all external walls, but all the internal stud walls are filled with rockwool, and there are a fair few cable runs through them, where the cables are clipped to the studs but surrounded by tightly packed rockwool. The ceiling/first floor void is filled with 200mm of rockwool, more than required by building regs, but my other half was concerned about noise transmission from the living room to the bedroom above (she goes to bed early and gets up at 5 am for work). It wasn't checked by building control, though, so could have been left out if we weren't concerned about noise transmission. I'd also agree that the acoustic insulation is a bloody nuisance and it was one of the most horrible parts of the build, too. I don't think I will easily forget the time spent packing 200mm thick rockwool into the gaps between the floor joists, as I had to do it from underneath, resting the stuff on my head as I went along each run. Even with a Tyvek suit on, with a hood, and gloves and ankles taped to the suit, I still ended up itching like mad.

Yes, it's not applicable to this specific case, I was referring specifically to cases where there wasn't a suspended floor, hence the reference to refurbs. There's a more general question here, though, why do we still consider having a suspended ground floor with a cold void underneath? It needs a great deal more insulation than a ground floor that doesn't have a void underneath, to achieve the same thermal performance, and, given that insulation can be load bearing and rest on the ground I wonder just how cost-effective a suspended floor is in the long term, say through the life of the building.

It may well be that we do start to see ring finals in 4mm2 before too long, especially in larger houses, as more and more cable ends up embedded in insulation. Almost all of our cables have some runs in insulation, because of the need to fit acoustic insulation between floors, and as acoustic insulation is often good thermal insulation. In our case, allowing for the number of outlets per ring final, plus diversity, plus de-rating for the between floor runs, we were OK with 2.5mm2, but had we had more outlets we'd have had to consider splitting the house into smaller rings, upping the cable size to 4mm2, or, the better solution, IMHO, switching to a radial wiring scheme. Even with a radial scheme we may well have had to up the size of the longer runs, or increase the number of radials, as de-rating for the long runs in insulation takes a 2.5mm2 radial down to around 18A. FWIW I did the same and ran 10mm2 to the kitchen hob etc, where it wasn't strictly required, but in my case it was partly because I had a long enough length of 10mm2 left from another job that would have sat unused otherwise! I'd wholeheartedly agree, but there are probably quite a few on this forum who have the knowledge and experience, and who don't happen to hold a current competency chit, who would be quite OK to determine cable sizes, and may well be able to do this earlier in the design phase, as they know where the cables are going to have to run, a bit like me checking the de-rating impact of the acoustic insulation in our ceiling/first floor void and the internal mineral fibre filled stud walls. If they then pass that information on to the competent person that's going to do the installation and sign it off, it reduces the risk of there needing to be spec changes later in the build. One advantage of this is that there are significant savings to be made by buying everything needed in as few orders as possible. I think that there is a different perspective on some aspects of specifying things like cable sizes for self-builders, both for the reasons given earlier and because often self-builders may be thinking ahead about how extras might possibly be added in future, something that any trades person tasked with installing a system may well not be aware of unless they are told, and that means the customer has to have awareness of the implications of what is initially installed in order to tell them. In our case I put several extra ducts in, to places where I thought we might possibly want power or water at some future date, but even then I've found that I didn't put one in that I'm still kicking myself about, and that's a water supply to the garage. It's far too disruptive to even think of doing it now, though.

I hadn't seen those other comments that you quoted, Nick, but there is also another factor that is important to self-builders - VAT. My experience was that very few electricians around here were registered for VAT, and that means that you would be daft to get them to supply any materials, as you'd not be able to reclaim the VAT, so everything would automatically be 20% more expensive. Add in that trade prices for electrical items from local electrical factors are very often a lot higher than online prices for the same items, and for a self-builder it just doesn't make sense to have a non-VAT registered electrician buy the materials for your build. Also, it doesn't make sense, economically, for a self builder to buy reels of every size of cable, it's often cheaper to buy a reel of the biggest cable needed and then use it where it isn't really required. As an example, I needed a fair length of 6mm², and a short length of 4mm², but opted to use 6mm² in place of the 4mm² just to avoid buying another reel, or an expensive short length, of cable. The supervision of installation methods is a very good point to highlight. My way around that was to work with our electrician as his labourer, so he could ensure that all cables, boxes etc that I helped put in were to the regs and that he was happy to sign off on that basis, having seen everything go in with his own eyes. Edited to add: Sorry, Nick, I was typing as you posted.

Thought I'd have a look around to see how common double insulated tails with the right outer sheath colour are, and how easy they are to buy. The quick answer is, not that easy!. The usual online places, like TLC: https://www.tlc-direct.co.uk/Main_Index/Cable_Index/Tails_Meter_New/index.html , Screwfix: http://www.screwfix.com/p/prysmian-meter-tails-1-core-grey-25mm-x-1m-reel-double-insulated-pack-of-3/95832 Quickbit: https://quickbit.co.uk/meter-tails-double-insulated-cable , Discount Electrical: http://www.discount-electrical.co.uk/section.php/108752/1/6181y-double-insulated-meter-tails etc, that I've used in the past, all only seem to stock tails with the grey outer sheath, but City Electrical Factors seem to stock double insulated tails with blue or brown outer sheath, which may be of help to anyone looking for this stuff: https://www.cef.co.uk/catalogue/categories/cables-and-accessories-double-insulated-tails-6181y . My experience with them locally has been that their prices were a bit high when I got a price for all our cable, fittings etc, plus you need a trade account to buy from them (not a problem, I found, they seemed happy enough to let me have one for a self-build).

The pond mats I've seen have been either coils of pipe tied to a stainless frame, weighted down with concrete blocks, or ladder-like affairs made of polyprop pipe, rather like giant towel rails. Whether it makes financial sense to use a water-source heat pump is a bit debatable, though, as they are expensive to install and need periodic replacement of a lot of pretty expensive special, non-toxic, antifreeze. The antifreeze also reduces the collector efficiency by around 20%, as no antifreeze is as good as water in terms of either thermal conductivity of heat capacity. You may well find that an ASHP will be a fraction of the cost to install and have lower overall running costs.

The way that BSI have protected their copyright and charged a lot of money for any safety-related standard (not just electrical stuff) has always slightly irked me. The consequence is that a lot of the very useful and important information in those standards is not available to the majority of the population, and I think that's not conducive to making people more aware of risks and hazards. One consequence is that information ends up getting disseminated like this, in an exchange on an internet forum, and with the best will in the world that information is likely to have the odd error, or be out of date when someone reads it years later. There's also a very real risk that misinformation can be spread in this way, too. For all my working life I had free access to all BS and EN standards, as a part of my job, but since retiring I've lost that, so had to buy one or two, and they are far from cheap, which highlighted the access problem - I'd never really thought about it before.

I've had the DNO move a meter in our current house, when they replaced the incomer a few years ago. My understanding is that there is some sort of agreement between them and suppliers to allow this. There's also an agreement to allow meters to transfer from one supplier to another.

Same here. For years that seems to have been standard around here; I can't ever recall having seen tails with an outer sheath the same colour as the inner sheath, which is odd, as it's such a good idea that you'd think it would have quickly superseded the grey stuff that's been around for years.

I'm pretty sure there is a difference, even if it's only one of interpretation, between Scotland and England a Wales when it comes to venting foul drains, though. Our building inspector was happy that the treatment plant was an effective vent, because there were no traps between the stack inside the house and the treatment plant. He allowed me to fit an AAV inside the house, at the top of the stack and above the highest waste outlet, because the foul drain was vented by the treatment plant vent. I've no idea why this is frowned upon in Scotland.

Where we are is deep in a very sheltered valley, so I was a bit surprised at how strong some of the wind gusts were. Anyone that's visited us will know how sheltered a spot it is, but yesterday morning it was a struggle to get out of the car in the drive without the door getting blown off, so it must have been blowing hard up on the exposed Plain. The wind we had was not enough to do any damage, but did reveal a flaw in our wall-mounted mail box - the lid bangs up and down and makes a colossal row in a strong wind. I ended up taping the thing shut.

The heat collector mats that Anthony laid in the lake don't seem to be massive, but they do cool the lake down. We stayed in one of the smaller cabins (Monty's Retreat) over New Year a few years ago, during some very cold weather, and the lake froze where the heat collector mat was a day earlier than the rest of the lake froze. I'd definitely not go for the heat pumps Anthony's used, as they really are very noisy. He's had to relocate the one in the cabin we stayed in I think, to reduce the noise. I have a feeling that the treatment plants may be Vortex units, but I could be wrong.

Installation method 103 in table 4A2 of the regs covers a cable embedded fully in insulation in a stud wall, but there's no specific case in that table that covers cables embedded in thicker insulation within an enclosed space, as may well be the case with the requirement for acoustic insulation in ceiling voids. Often the acoustic insulation is mineral wool or similar and so is a pretty good thermal insulation, but realistically I think the de-rating factor given for Method 103 is probably good enough, given the U value that was used for the testing to derive the factor. Method 103 gives a current de-rating factor of 0.5 for T&E (as per table 4D5) embedded in insulation with a minimum U value of 0.1 W/m².K and not touching a surface. That's straight from my copy of BS7671 17th Ed, which is not the most recent, it's the amendment 2 version, not that I think those tables will have changed. If they have changed with amendment 3 than perhaps someone with a copy can correct me. I'm not going to buy another copy of the regs now our build is completed. As above, I'm not going to breach the copyright by posting the tables, either!

I'm logging some data at the moment to try and see what's really going on in terms of heat output into the house. Anecdotally, I can say that our heating often goes for a day or two in mid-winter without coming on at all, then maybe fires up for an hour or so and shuts down for another day or so. I have our room stat set for 20.5 deg C and the ground floor seems to be pretty stable, at between 20.5 and 21 deg C, with the unheated bedrooms upstairs being about 1 deg cooler as a rule. I'd be inclined to set the boiler to as low as is reasonable within its modulation range, which depends very much on how much heat the UFH is pulling from it when its on. 48 deg C flow should be pretty good in terms of boiler efficiency, as the return will be cooler and the boiler should be fully condensing. With the floor mixer right up at 35 deg C there's a risk you might get big room temperature overshoots. This happened when I had our mixer set to 28 deg C; the room temperature would continue to increase for a couple of hours or more after the heating had turned off. I run our UFH mixer at around 23 to 24 deg C now, just about as low as it will go, and that helps a great deal in terms of keeping the temperature more stable. I did hunt around for thermostatic mixer valves that would operate reliably at low flow temperatures, as this was something that had come up a few years ago on another forum, where someone with a similar spec house had problems getting the UFH to control properly. It was where I learned about the significance of having a low flow temperature and that few mixer valves allow the sort of low temperature flow adjustment a low energy house seems to need. The Wunda manifold I used uses an external temperature probe, fitted inside a pocket in the centre of the flow manifold, to control what looks very like a large thermostatic radiator valve on the hot inlet side. Sadly it seems that Wunda have now changed the design, and I've no idea if the three way mixer they now fit will adjust down to such low flow temperatures.

I went through Part F to see what the requirements were in terms of competency to install an MVHR and it turns out that there aren't any! The problem is a cultural one, I think. Building inspectors are getting so used to seeing bits of paper from a supposedly competent person that they seem to expect them for everything. There is a guidance note for providing the evidence that an MVHR has been correctly commissioned, but when I was looking through all the regs its existence was far from obvious, so I just wrote up a report showing compliance with each part of Part F that applied, with some installation photos to show things like the accessibility requirement. It was only later that I found the compliance guidance note, but if anyone's looking for it, it's here: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/456656/domestic_ventilation_compliance_guide_2010.pdf It's a bit easier to find, now that the government website has been tidied up. Back when we started our build I ended up downloading all the regs and cross referencing the bits that applied to us in a single document, as it was more than a bit frustrating trying to wade through loads of stuff that didn't apply.

When up there years ago, the two of us went into Hull one evening, really so my mate could show me the "delights" of Hull on a Friday night. I've never forgotten it, mainly because of the delightfully polite and ladylike young women, out en masse for a drink or two............... (In reality the place seemed full of pissed slappers who'd make a bunch of football hooligans look like gentlemen. It's the only place outside of Redruth, Cornwall, where I've seen women pissing in the middle of a busy street and no one taking any notice).

Go and talk to a local farmer - 5 minutes and he'll show you how to just use the leverage on fencing pliers to pull plain galvanised fencing wire dead tight, with no need for anything other than staples. If I had the means I'd make a video, as it's really quite easy to do, and relies on the partly hammered home staple next to where your tensioning gripping the wire enough to hold it tight. Bit of a knack, but cheap and easy. If you don't have anyone to show you how to do it with just fencing pliers, then get a tensioner, like a gripple, along with the pliers. That way you can tension the wire with one hand and bang the staple all the way home with the other.

Good point, it may have gone hard in the 20 plus years I've had it sat in the loft. I've not even opened the boxes to look at it. May end up stripping it out for the copper...............

I like the idea of using double insulated tails with the outer the same colour as the inner; it's always puzzled me why most of the stuff available uses a grey outer and then needs a label or colour coded sleeve to be added. I should have put the reels of old cable up on ebay, as I've never had either a reason or desire use it in all the years I've had it sat here; it was an impulse buy that ended up being thwarted by the regs. Might stick on ebay when I clear out the loft before we move, perhaps with a note that using it would be non-compliant to cover my backside. IIRC there's at least two full reels up there, maybe three.

Tensioning is pretty easy with fencing pliers: https://www.jacksons-fencing.co.uk/product/sc_370700/250mm-universal-fencing-pliers.aspx?tpc=AF&fmc=CS&fnc=CB&timber=1 I've run miles of wire around farm fencing with them and with a bit of practice you can get the wires really tight.

What size pipe you use really comes down to the incoming pressure. Our rising main and stopcock in our old house is 15mm, and we have mains pressure hot and cold systems fed from it. We never see any noticeable changes in flow with things like the washing machine coming on, or a toilet flushing, but that's down to the pressure coming in never being lower than about 6 bar. The main downside with having a 15mm cold main going up into the loft and right down to the other end of the house from where it comes in is that it's a bit noisy. For those with an incoming mains pressure that's right at the lower limit of a supply, then there's a great deal of sense in running the biggest pipes you can, as every tiny pressure drop removed helps.

You're spot on, Jamie, if you continue wing insulation down to a couple of feet below ground level, even with a vertical thermal bridge up through the the core, the net effect is to significantly reduce the overall thermal bridge at this point. There was some work done on using below ground peripheral insulation to reduce thermal bridging in refurbs, where taking the floor up to add under floor insulation was impractical, and it is a pretty good mitigation measure. By significantly reducing outward, horizontal, heat transfer, the heat loss path is forced to be vertical, and even though soil isn't that good an insulator, with a deep layer of buried peripheral insulation you can create a deep enough layer of soil under the floor to be a reasonably effective insulator.

Why's he labelled the tails the wrong way, and are those tails double insulated? When I got wind of harmonisation and the colour change I went and bought a couple of reels of the old cable. Still have it in the loft. Not saying I'd use it, but it might be handy for anyone doing work on an older house who may not want to be too obvious that the work was done after the change...........