TerryE

Internal cables are single core: less attenuation, cheaper per m, but can easily fatigue if flexed too often. Patch leads are usually multicore. A lot more flexible (and cheap to replace if they do go).

Nick, It's not worth scrimping on the wall plates. Tripping over Enet leads is an occupational hazard. If someone goes arse over tit on a cable then almost certainly the worst that will happen is that the lock will snapped off the RJ45 plug at the plate rather than pulling out buried cables or snapping them out of the wall.

Sounds like you are having battles that you don't deserve. Sorry to hear that! I didn't like ecoHaus Internorms T&Cs, but I can't find any material faults with their installation service. They did a good job for us.

We compromised on Cat5a to all rooms (just one point) starred back to the electrical panel in the utility next to the master fuse box. I am putting a 12-port switch in there, with one cable going to the BT ADSL router in the kitchen. I will keep the main traffic to the wired circuits and the Wifi will be mainly used for the tablets and mobiles.

More to the point, the interface between the aluclad and the underlying frame isn't supposed to be exposed to the elements. So not only does the closer mechanically interlock the two frames, in this case it also include a flange to bridge the adjacent aluminum cladding elements. Given that you've spent all this money on a top-class widow system, I don' understand why you'd compromise on something so trivial.

One tip that we discovered with Megabad (and the other suppliers): they offer a 2% discount for direct funds xfer compared to CCard. So you will probably get a better deal by using an exchange broker to do the xfer. We use Moneycorp -- but that's because I already use them quite a lot to cover our EU expenses in Greece.

Hi. Who is your installer? What is the range for your windows? Is this the same for the coupled door? Is your installer also the window supplier? We have exactly the same configuration and this caused quite a lot of issues at detailed survey, but installation was trouble-free. The core point is that there must be an Internorm approved coupler between the two frames to ensure that they are tightly coupled from both a mechanical and air-tightness perspective. In our case the Ecohaus SW salesman quoted on the basis of the KF200 range doors and windows and when we said that the KF200 style doors weren't what we were looking for for the front door, he said that this would be best sorted at detailed survey, at which time we could swap the door style and pay any uplift, so we proceeded and paid our deposit on this basis. The problem came when our survey engineer said that we could only have a KF200-style door because the only couplers that Internorm supplied for KF200 profiles was a KF200 to KF200 type. We therefore had to have a KF200 door (and this then got us into trouble with the planners, but that's a different story). Back to your installation -- if you can see daylight between the door and the window, then the coupler is missing. Without the coupler, (a) you will never pass airtightness and (b) the mechanical fit of the window + door is compromised because they aren't properly coupled. Not good on both accounts. Whatever happens, the only way to fit the coupler is to remove and to reinstall both the door and window, as they need to be coupled before installation in the timber frame. If you've chosen a different door and window style then you have an issue but one where you could reasonably expect to have the supplier point out that the installation that they were supplying was an invalid configuration. Sorry to bring bad news, but you really need to sort this one out sooner than later. And IMO, this is one where you should not accept a compromise. You#ve paid a lot for quality product and that is what should be delivered. Terry

Correct. You would only get the heat recovery if the external air was cold enough for the internal air to cool to its dew point on the way out.

@Alphonsox, Neil, simple one first: the 1½°C comes from some information that I discussed in A few ASHP / UFH bits of information and is simply the ΔT calculated by taking the mass of my slab × SG of concrete and assuming that the heat has uniformly spread throughout it -- which (thanks to the conductivity of concrete and all of the rebar in the thicker profiles) isn't a bad assumption: within a few hours of driving heat sources being removed I expect that it would be within 20%, say of this average. As to a better model, getting a totally accurate one is difficult because the thermal conductivity of all the rebar is 60 × that of concrete. The simplest thermal model to consider is that of a PEX pipe embedded in concrete. This has two spacial dimensions and time of course, so is solvable by HEAT2D or equiv, which I am considering doing, but this also has its limits since the concrete has a boundary and the out and return runs are interleaved in the slab. A simpler way to envision this is to consider the rough approximation of the heat being transferred to a cylinder of concrete 300m long (my 3 loops are within 10% of this maximum pipe length), and of radius r. This is roughly πr²lρcpΔt and plugging in the numbers = πr²·300·2400000·0.75Δt J or 1.6E+9·r²Δt J or 470r²Δt kWh. So if the 9kWh was just transferred to the cylinder of concrete 5cm around the pipe, this would be raised by an average 7°C which is the right ballpark, but in reality the concrete immediately adjacent to the pipe will be at whatever the water temperature in the pipes is, and the heat will quickly diffuse into the main slab, at least. Whatever the distribution is in practice, the temperatures in slab will be bounded by the inlet water temperature. One Q is to ask whether a 3KW input is safe and the point to note here is that is factors less the input for a conventional UFH load for this size of slab, or per loop. Whatever happens I will instrument all six of the inlet and outlet temperatures and record the real response. I will design my initial heating strategy to keep the heating within safe operating margins. This will be by computer (RPi) control but with a thermal fail-safe cut-out (at say 35°C) independent of the computer control, so there is no risk of damage to the UFH system even if I make a programming cock-up during development. Unfortunately it's going to be another 3-4 months before I get to the point where I can start to commission the system and to collect real data.

We've jsut been having some debates about slab UFH strategies on the relevant forum, but I wanted to do some sanity checks without getting into over-specified 2D or 3D heat flow equations, which I then need to modle. Some of you have probably come across this type of graphic (source BuildingPhysics.com): (BTW the reason for the alternating hot and not-so-hot pipes is that if you think about it, this is house UFH loops are laid, using the double-back technique.) This also looks to be a steady state solution, and in my designs we will nearly always never get near steady state. Anyway, I tried to find some decent UFH design docs and after a reasonably long search I could find lots of guides that go into the installation side and failed miserably Most ship over this sort of stuff and just make passing comments like "use model XXX pump of the heated area < 250m² and model YYY otherwise." Worse what I can find is US stuff in GPM, etc. Great. So I am left with the book that I used 30 years ago to design our last CH system until someone can recommend something better. We have 3 loops of 16mm PEX, and from my old CH days, the max flow rate should be <1½m/s so ×3 loops that's 0.9 l/s or (3.2 m³/hr) so a 3kW heater will raise this stream by ~3 0.8 °C. A 100m PEX loop at 1½m/s is a pretty high head IIRC (just over 1 bar), and this 3.2 figure seems rather high for 3 loops so halving the flow rate will double the heating to ~1.6 °C with a head of roughly 0.25 bar or 25 kPa which is more typical of UFH pumps. So if I assume this lower figure then the difference between the out and return sides of the UFH will be ~1½°C but how much is the return above slab ambient? The answer is whatever is needed to pull 3kW into the slab, and that's going to be the stable flow and return temp. Modelling this is complicated because its not a true steady state solution. The return will start at slab temp and rise maybe 1°C per hour as the slab volume around the pipes is heated. As I said modelling it really complicated. Validating by direct measurement is easy. So at the end of a long heat, say 3 hrs, the flow and returns will be ~9°C and ~3°C above slab baseline temperature. One the heat source is removed, the heat will continue to transfer towards a uniform distribution throughout the slab some 1½°C above slab baseline. This will then slowly fall back towards baseline over the next day or thereabouts as heat is transferred from the slab into the rest of the house structure and the room environment. Jan is calling me for pre-dinner drinks so I'll break this now for any general comments / feedback

It did strike me that in terms of the physics, if the moisture is condensed out in the MVHR heat exchanger then the latent heat of evaporation will be returned to the airflow and effectively transferred (mostly) to the incoming air stream. So you'll only get the net cooling effect if you have the summer bypass on. This also largely addresses @ragg987's point above.

Yup, we registered our house last year for the first time, and ignoring the long story around that, when this was all done and dusted, our solicitor send us our original deeds as "these are of historic interest only!" Once your plot is registered with the LRO, the only time that the deeds might be useful is if you got into a legal dispute with a neighbour, say, over a boundary, and even then the assumption is that the LRO document is correct unless you prove otherwise.

@MikeSharp01 Mike, if I crank the numbers, my slab has a thermal capacity of ~23 MJ/K or 6.4 kWh/K. Using my 9 kWh "overnight E7 chunk" example, this represents about 1½°C temperature rise or 0.2mm across our house frontage of 11.5m. This is small beer compared to the internal expansion / contraction of the outer stone skin itself.

@le-cerveau, that's precisely correct: you may as well control from a single aggregate temperature. However, you also need to trim the manifold valves so that the flow-rate through each loop is roughly proportional to the area covered by that loop. This is a one-off calibration / setting issue. One simple way to achieve this is to balance the loop lengths within 10% say and use the same loop density on all floors, then you can just fully open all manifold valves. The other way if you are using separate temperatures is to use the temperature curves on the 3 loops to determine if one is out of balance.

@jack, my basic thesis is that with the thermal capacity of the slab and the time constants of the house we really don' t need a fine control. My intent is simply to dump large chunks of heat into the slab on an occasional basis. The exact amount per chunk isn't really that important. This could be an inline electrical heater dumping into the slab for 3 hrs @ 3 kWh during the E7 window; it could be running the ASHP at a set 30°C, say, for 30 mins. I doesn't really matter that much whether we have 1, 2 or 10 chunks per day; the only issue is that the chunks must add up over the day to whatever the house needs as input to maintain an environment within the target temperature tramline. One simple strategy to ensure this is to establish a minimum back-off between chunks and trigger the next one when the flow return temperature from the slab falls below a preset threshold. As to the time bit, well that's what you get when you eventually retire -- though there still don't seem to be enough hours in the day!

I've got three loops in a single zone and what I am proposing is to use 6 × DS18B20 sensors with a thermal gel and taped to the PEX, then insulated around each pipe + sensor. These are positioned as the PEX leaves the slab, and I will attach a couple more at the two manifold inlet / outlets. This might seem like overkill but the DS18B20s are cheap (IIRC, I last bought 10 in waterproof sleeves for £15) and using one-wire to connect them up to a Wemos ESP8266 module is another £10-20. My main reason for this is instrumentation and calibration. With enough data, I can correctly balance the 3 loops and also get a good handle on the transfer function of the slab. However I also propose to use them for my control. My measurement cycle will be something like running the pump for couple of mins whilst I collect temps. If the temps are imbalanced then this would indicated that it might be worth running the pump to help redistribute the heat in the slab, but if they are much of a muchness then there isn't any point in wasting the electricity. I am mainly doing this because I get pleasure out of this sort of project. My ultimate control strategy will no doubt be a lot simpler, but with this data I will have an evidence-based understanding of how effective it is.

David, Neil, I want to cover this in detail separately but the thermal flows in the slab make it very problematic using point monitoring in the slab as a feedback for control. I will be using a different remote sensor: the temperature of the UFH water return. In JSH's case he has a Genvax which does active control of the air temperature on a far shorter time constant than the slab's so using room stats are even more problematic. Need to finish that blog blog post one this.

You will need a long drill if you want to make this easy. I used an old 1m × 15mm masonry bit. If you are using 20mm tube then drill the hole on the inner; use the long drill in-to-out; withdraw the drill after doing the pilot hole and drill the outer hole from the outside using the pilot as a guide. Then thread the drill back through the new enlarged outer hole. Remove drill from the chuck and slide the pipe over it as a guide; push the pipe through and out to the outer wall line if nec. Sikka tape both sides for air tightness. Neaten outer after the stone skin is up; foam and silicon after the cable is in to complete air tightness. Takes about 10 min per hole with a bit of practice.

If you do the maths, its actually a lot cheaper to hang your wet washing in a MVHR extract room such as a utility room. (We have a store room configured with extract only for that reason.) Add a dehumidifier if the moisture is getting too high. The run rate for one of these is a lot less than a condensing tumble dryer.

(This post is a précis of a post and thread discussions that took place on the eBuild forum October last year and subsequent discussions with my builder.) Many of the self-builders active on the forum will have used or be familiar with the Passive Foundation system marketed by MBC Timberframe. The essence of this is that the foundation is a raft slab that incorporates a ring-beam that sits inside an EPS former. This former both acts as shuttering for the concrete pour and as insulation between the slab and the underlying hardcore base. The slab is therefore wholly contained within the thermal insulation envelope of the house, typically giving an overall U value for the slab of around 0.1 W/mK. So far so good. A variant of this is where the house has an external brick, blockwork or stone skin. In this case one approach is to pour a second outer ring-beam to carry the outer skin, and the MBC structural engineer (SE) Our skin is a rough-cut Cotswold-style limestone with an s.g. of around 2.5 (or 2.4 allowing for mortar); the walls are ~5m high, and the courses on average 125mm deep giving a linear loading of around 1.5 tonne/m rising to 1.8 on the 3 gables. The underlying ground is a very stiff impermeable (Oadby Member) clay, but We have some medium size tree quite near the foundations. Here is a simplified diagram of this. The SE specified bridging H20 rebars at 150mm centres to couple the inner and outer ring beams structurally, so that the load of the skin is carried across onto the main ring-beam and transmitted down through the ESP300 underneath the beams. If we assume that the load of the stone and house was carried only by the EPS300 sections of the slab, this gives an overall GBP of some 12 kPa and the 266 H20 rebars ensure that there will be minimal differential movement between the outer stone skin and the timber frame supporting everything else. This is comfortably within the allowable bearing pressure of 120 kPa recommended in the Geo-survey report. So this is a good structural design, but it unfortunately embeds a major thermal design flaw. If you consider the thermal cross section of the total rebar, it is pretty much the same (from a thermal perspective) as replacing the rebar and the EPS between the two beams by solid concrete. To be honest I along with everyone else missed this thermal design flaw when I was given a copy of the slab design to review. The penny only dropped for me when I saw the rebars in place, and the concrete was just about to be poured. The inner slab and ring-beam is within the insulation envelope of the house, but the outer ring-beam is at ground level and directly carries the stone skin. In the base design this would be fully exposed to the elements and could often drop to ~0°C or below in winter. The 266 × 2cm diameter mild steel rebars have a total cross-section of 0.084m, and this couples a slab at roughly 21°C with a ring-beam at roughly 0°C across a 20cm gap. This is a pretty perfect thermal bridge as steel has a thermal conductivity of roughly 40 W/mK -- this means that we will lose heat at roughly 21×40×0.084/0.2 W = 350W or 8.5 kWh / day in colder winter months through these bars. This is over 3 times the design figure of 2.6 kWh for the entire slab. Here is a small extract from the slab engineer's design. I've coloured the different components and removed a lot of the structural detail which isn't relevant to this discussion, so we can focus on the issue here. We were too late to change the design fundamentally, but if left uncorrected, this flaw would result in the slab being the single largest source of heat loss (more than the walls, the roof, or the windows and doors for example). So after discussion with MBC, Hilliard their SE, and members on the eBuild forum, what we decided to do was: We retained the outer EPS formwork that wrapped the outer ring-beam. This still left a thermal bridge between the top of the outer ring-beam and the stone skin it was carrying. Hilliard confirmed that a course of Perinsul Foamglas would be capable of supporting the design load of the skin and largely close the thermal bridge. However, we would then have an exposed ESP front and FoamGlass course edge which is cosmetically crap and vulnerable to rodent damage. So after discussing options with our builder we decided to cover the entire exposed EPS / FoamGlass surface with some courses in engineering brick. And when the skin was complete we would then put a perimeter path 60cm wide and 10cm (min) deep around the house on the crushed stone bed. Here is a simplified schematic that I drew up for my builder of the approach that we finally agreed on. What he did was to use two external courses of engineering bricks as an plynth in front of and on top of the FoamGlass, followed by two header courses to step back the wall line. This engineering brick wrapper is primarily cosmetic and a weather protection as the load is actually carried down vertically through the FoamGlass onto the ring-bean, I've also included a photo of the plinth at one of the rear French windows where you can see how it looks in practice. There is still going to be a little bridging on the diagonal between the ring-beam and the outer engineering brick layer, but my rough estimate is that this will be more like 50W rather than the 350W discussed above. An extra 1.5kWh/day, I can live with.

I've since talked to a few guys in England who say the same thing.

Our experience is that when you've got a competent sub-contractor, then they will sort the issues entirely within their responsibility. However when it comes to interfaces - such as your reveals - then it's down to you and the devil is in the detail.

A Larsen strut timber frame filled with cellulosic filler has reasonably high thermal mass, especially balanced by a passive slab. The decrement delay factor beats ICF hands down. The main problem for you with this type of design is that when couple with MVHR and no thermal cock-ups, its too well insulated to prevent a log stove overheating the house. Anyway one comment on the design: it seems out of balance. It shows three small double bedrooms, a snug and an open living area. OK, if the house has a couple as occupants and the two extra room are guest rooms for occasional visitors, but if the 3 bedrooms are routinely occupied then have you enough living rooms. Either that or you need to make your bedrooms larger to include living space for a desk or a settee... At a minimum, I would suggest making the master bedroom a lot more spacious. Another thought extend the house to move the bedrooms 2 and 3 some 1.6 - 2m apart and fill the space with a split forming 2 small walk-in wardrobes this will free width for a desk / dresser / couple of chairs or whatever.

I see that your windows are set back 50 to 75 mm in the the frames. What is your weather seal treatment going into the reveals? Are your depths OK?

With the best will in the world, even the good builders are a load of messy buggers