Jeremy Harris

Here it's still 25 deg C, having dropped from a bit over 32 mid-afternoon. Hopefully it'll be down to the low 20's tomorrow..................

Be aware that there may well be safety issues as well. US 230V AC is 115V AC either side of earth, I believe, not the same as the UK system of 230V AC above earth; I think it's effectively a two phase 115V AC supply to the house, with the 115V circuits from one phase and the 230V circuits using both phases in series (it's a 180 deg two phase system, IIRC). This has implications for the PE and the internal wiring and insulation within the appliance, so needs checking. It may well be OK. but it may not. I had a 230V oil cooled arc welder years ago, that was US made. It didn't mind working on 50Hz, but it did need internally re-wiring to be OK on a UK 230V AC supply.

Sadly I think there are a fair few window manufacturers that make errors like this. We had a window delivered that was 400mm too wide, and to their credit they came back with a replacement a week later, but it shouldn't have happened in the first place, as the schedule was very clear. We also had a problem with a defective glazing unit; again they replaced it quickly, but it should have been spotted before it left the factory (it wasn't transit damage). For some reason, windows and doors seem to cause a disproportionate number of problems. I will admit to losing faith in getting the manufacturer to fix adjustment problems, after two goes at it, and spent a day adjusting all the doors myself. Not hard to do, but a bit time consuming. Worth it to get all the doors closing smoothly, with the latches operating very easily, and the tiny air leaks that were picked up on the air test fixed. I get the feeling that the big suppliers are geared up to fit loads of windows to new developments, and rush the installation work, knowing that buyers of new homes seem happy with crap.............

My money is on a slab problem, that has thrown everything else out. If the slab has a slope on it, for any reason, then that will have a pretty significant impact on all the openings, as well as the first floor levels. I doubt there has been any settlement or movement, as the bearing load that a slab like this imposes on the ground is pretty low, far less than the max allowable compressive stress in the EPS. IIRC, wasn't there some pretty bad weather when the slab went down? Maybe the fact that there's also a big step in the slab has also contributed to the problem (not an excuse for it, just suggesting a possible reason). Either way, my experience suggests that you'll get a solution from MBC, they seem damned good at fixing any glitches like this that occur.

Sounds to me like this is their problem, that they have to fix. I wonder why they didn't notice that they couldn't fit a 52.8m thick glazing unit into a frame that can only take 34mm?

That sounds right, we also have Planitherm glazing units, double soft e coated internal panes and argon filled, with warm edge spacers. Our gaps are bigger though, most are 4-20-4-20-4 with the toughened stuff at the front being 4-20-4-18-6.8. How come you've ended up needing thinner glazing?

If the slab is out, then the whole frame will end up out of true, I think. I remember the guys spending a lot of time getting the slab set out dead level, presumably to avoid just this problem. I wonder how the slab ended up as it has? I think that's probably the root cause of all the problems your having, as the frame should be pretty much dead square, if our experience is typical, but obviously the whole thing would be thrown out if the slab isn't flat and level.

In our case, the problem is the internal level. The bottom of the front door is barely 8mm above the travertine floor, hardly enough room to get even a very thin door mat in place, and I'm reluctant to try and make a recess for an inset mat. Even then the door cill barely complies with the 15mm Part M maximum height for an accessible door. The irritating thing is that technically this isn't an accessible door, either, as there are steps leading up to it from the drive, so it didn't need a Part M compliant threshold, but the supplier couldn't supply a taller cill section, and I didn't think to have a packing piece added under the cill, an oversight on my part. Another 5mm would have made all the difference, but having had the door off to check there's no way that it could be altered to allow this now..

The problem of door cill level is one that I think many have had. The biggest issue is that the thickness of the floor finish and the section of the door cill is critical, not just to get things right, but to comply with Part M. The door manufacturers have reduced the height of their cills, in order to comply with Part M, mainly, and that then reduces the available tolerance for the slab and floor finish. I had a devil of a job getting the dimensions of the cills from the door and window supplier, and when I did get them they were very scruffy, photocopied and then scanned copies of a fax, believe it or not.

That sounds reasonable, as a 28mm DG unit would probably be a 4-20-4 unit, whereas a 28mm 3G unit would have to be be something like 4-8-4-8-4, which would be a fair bit worse (not even sure that such a thing is available).

It's not that easy to calculate, but I doubt that a 10mm gap 3G unit (if available) would be significantly better than a 20mm gap 2G unit, with the possible exception that if it had two low e panes the radiated IR loss would be lower. I'd expect a Ug value of something around 1.0 to 1.6 W/m².K, with Uw (the actual window U value) being worse, and dependent on the frame type and the ratio of glazing area to frame area. This is largely guesswork, though, as I can't quickly find any data for 10mm gap 3G glazing units. It's based on the fact that I think that Ug will probably vary in a pretty linear way in relation to gap thickness, all else being equal, so the typical 0.5 to 0.8 W/m².K Ug of a 4-20-4-20-4 unit would be around doubled if the gap was halved.

No, I'm afraid it's not possible, or at least not without going for some really exotic product, like vacuum glazing, which will be a lot thinner (but isn't that easy to buy, and is mega expensive). The gap between the glazing is quite critical to performance - too big and circulating convection currents can develop in the gas filling the gap, too small and the conducted heat loss through the gas in the gap increases, pretty much in direct proportion to the reduction in gap width. 20mm is about the optimum gap, 16mm is just about the lowest acceptable gap for 3G, anything less than this will reduce the performance too much.

The guys that fitted our film just used a very thin stainless steel straight edge and a scalpel to trim the film very close to the edge of the glass. The film is maybe half a mm away from the external bead, but in practice that isn't at all visible. I can't see those beads being a problem, they will just hold their thin stainless tool against the edge bead and trim the film to a neat line just inside it. I can vouch for the external film being very effective in this hot weather. The inner panes of glass are barely getting warmer than room temperature, and the solar gain has been massively reduced, to the point where the cooling systems are not coming on until mid to late afternoon on the last couple of days, when it's been over 32 deg C outside.

My solution to dealing with network connectivity was to build a battery-backed, uninterruptible, low voltage power supply box for all the network kit. This provides both 12V and 5V regulated DC supplies, and has a 100Ah, ex-server farm UPS, sealed battery. It works well, and means that both the LAN and internet connectivity remain working during shorter power cuts. If the power cut is more than a couple of hours the internet connectivity goes down, presumably because the back up battery in the fibre cabinet up the road runs down. It would be be a lot neater to have a whole house backup supply, one that switches over in a few ms, as the Powerwall 2 does, though.

I've long thought that a system like the one they have in parts of France, where EDF change the tariff when they predict high demand, would make sense. Over there, or at least where some friends used to live down in the Loire valley, they announce the high price times and dates on the news, so that people can plan ahead and not use high power appliances during the times that the tariff is high. It's pretty low tech, doesn't require any changes to meters, cabling, data collection, etc, all it needs is for the billing software to take account of the high rate periods. I like the fact that it's nice and simple, with little to go wrong, be hacked etc, and seems a better solution than fitting smart meters, that so far seem not to be very smart at all. The great thing about it is that it effectively transfers part of the demand management task from the energy company to their customer, raising awareness of the challenges of managing peaks and troughs in demand. On the battery topic, I think there's also some value in the power cut supply capability that the Tesla system has. I'm looking at buying a small generator and fitting a changeover switch and connection point, so that I can run some of the house loads when we get a power cut (a not uncommon occurrence here). To me, paying up to around £500 to £600 for a solution to reduce the impact of a power cut would be worthwhile, and I might consider paying a bit more for a solution that provided a few hours of full power capability in a power cut. The Tesla Powerwall 2 would run our house for more than 24 hours, with no load shedding and pretty much no restrictions, just a bit of peak load management when cooking. It's not enough to make the Powerwall 2 viable, in terms of overall cost saving, but it does make it look more attractive. We generate massively more than the house uses for a large part of the year, and a few rough calculations suggest we could shave around £200 to £250 from a no standing charge electricity bill by having battery storage. We might be able to shave a bit more off if there was a reasonably cheap E7 tariff, if there's a way to grid charge the Powerwall 2 overnight in winter. It looks like we could save perhaps £2000 to £2500 over the life of the battery pack in the Powerwall 2, so not enough to make it worth fitting yet.

I've no idea, as I've never actually stepped foot into a Lidl store yet (or Aldi, come to that!). I'll ask on Thursday, provided they have stock locally.

My experience has been that cash flow can be a real problem for small traders, especially if they get one or two late paying customers. A couple of the guys we had working on our build gave us a slightly better price because we purchased all the materials, saying that they would rather make a few pounds a day less on their labour price than have to bear the cost of a load of expensive materials up front. I made a point of paying them all at the end of each week, too, provided the work was OK.

I'm tempted by the generator. I wonder how noisy it is? It'd only be a back up for power cuts, and 1200W is more than enough to keep our house going most of the time.

The two big challenges of trying to keep any DIY beer fridge cold are air leaks and insulation effectiveness, so if fitting a glass panel I'd keep it as small as possible and ideally the lowest U value you can get. Also, if the glazing has a low e coating, fit it so that the face that's supposed to go outside is facing inside the fridge, so that more radiant heat from outside is reflected back out. I made a cool box, using a Peltier heat pump, around 20 years ago, and although it's fairly well-insulated (50mm of PIR all around) and pretty well sealed (over-centre catches pulling the lid down on to a neoprene seal), it takes a lot of power to stay cool, and warms up fairly quickly when the power is turned off. I recently bought a small PC water cooling kit, with a pump and radiator, to re-build this cool box, to try and overcome the problem of heat soaking back from the outer heat sink to the inner heat sink as soon as the power is turned off, but have decided to build a complete new cool box, slightly bigger, with around 100mm of PIR all the way around. I have a small beer fridge here in the study, but it's an ex-hotel one, and is old and getting a bit noisy, so I'd like to see if I can make a quieter one, that can run from 12V and double up as a big portable cool box.

Something odd is going on today, as it's hotter outside, yet cooler inside, so much so that the slab cooling hasn't come on yet. It's 32.1 deg C outside, from the sensor standing off from the sheltered North wall (the hottest I've seen so far this year) yet it's only 22.2 deg downstairs and 22.6 deg C upstairs. The MVHR cooling has just come on (it comes on at 22.5 deg C upstairs), but I suspect that the slab cooling may not come on at all today (it comes on at 22.5 deg downstairs). We're currently generating just over 6 kW, and consuming around 3 kW, with my car on a slow charge. I'm tempted to pull the USB stick from the logger and see what all the data looks like.

Reminds me of lying in a bed in Northwick Park Hospital, during very hot weather in late summer 1972. It was an orthopaedic ward (all five of us in it were victims of our own stupidity on motorcycles) so we were allowed alcohol. Friends used to bring in cans of beer (and Fosters for the one Australian) and to cool it down we used to fill the sink at the end of the ward with cold water and stack it full of cans. The fun bit I remember was trying to open a Party 7 (remember those?). It took three of us to get enough working limbs to open it, all in wheelchairs. One wedged the can against his wheelchair, one held a spare pin (that had been through his ankle when he was in traction) against the top of the can and the third hit the pin with the base of a drip stand. The banging alerted the sister, who was not amused when she came in and saw a fountain of beer foam erupting towards the ceiling..............

There's enough there to make a few really good DIY beer fridges..................

I've seen similar systems to this used in France, where they seem to use more steel in buildings anyway; most "stud" walls in French houses seem to be made using steel. I suspect there's going to be a brick or rendered block external skin on that building, as there doesn't seem to be an easy way to fix cladding. Be interesting to see what it looks like when a bit more work has been done.

I doubt that the ASHP will be using more than a small percentage of your PV generated output in practice, so rather than have the ASHP switching from heating to cooling mode, with the inherent power loss that creates for every switch over, I'd just leave the DHW running from the excess PV. What's the output rating of your ASHP in cooling mode? Ours is rated for a lower output when cooling than when heating, and rarely uses more than around 500W of input power in cooling mode. Right now the PV is generating nearly 6 kW and the cooling has yet to come on, but when it does that will still leave more than 5 kW of spare generation capacity for DHW, and the Sunamp PV can only use 2.8 kW of that, so we will still be exporting a fair bit (enough to charge my car).

Our slab cooling uses a pretty constant 500W or so when on, and has been on for around 4 hours a day during the hot days, so around 2kWh/day, perhaps. That's input power and energy to the ASHP, and seems to equate to a bit over 7 kWh of effective cooling energy, or around 1.8 kW of cooling power. In addition, the MVHR heat pump has been running for around the same time, and that delivers an output power of around 1.5 kW in cooling mode, and uses about 400W, so around 1.6 kWh input energy, and perhaps 6 kWh output energy (bearing in mind that this is really outward heat transfer power and energy for both). We have been generating over 40 kWh/day recently, so the cooling is effectively free, in terms of energy cost. We are just coming up to 20 MWh of generated energy in total, with a total consumption of just over 7 MWh, over a longer period (the electricity supply went in before the house was erected).