Jeremy Harris

I've found Osmo to be very durable on our oak staircase. It had a bit of abuse during the build, but a quick rub down with a Scotchbrite pad and another coat of oil and it came up looking like new again.

Flow restrictors. I had a problem with a temporary, part time, building inspector, who had been brought back in after retirement to work a few days a week to help clear their backlog. He was a complete PITA; started off by saying he didn't like the lack of "proper foundations" (bear in mind this was the completion inspection he was supposed to be doing), picked up on the water flow rates and wanted restrictors fitted and duly certified. When I told him I'd done all the plumbing and heating system installation myself he nearly had a fit, trying to tell me I wasn't qualified to do it. When it came to the flow restrictors, he eventually accepted that I could fit them, as long as there was photographic evidence of me installing every single one, plus he'd do a random bucket test to check that they were fitted. I tried to argue that that part of the regs didn't apply to us, as we had a private water supply (which was true) but he wouldn't wear it. In the end I bought a whole load of restrictors and spent the best part of a day going around fitting them. We had a very much nicer bloke around for the final (final) completion inspection, but I'd prepared for the PITA git. The chap we had in the end wasn't the slightest bit interested in any of the water stuff, as he agreed that it didn't apply to us, anyway. Needless to say, a couple of days after we'd got the completion certificate most of the restrictors were removed. I've left them on the basin and sink taps, though, because they actually makes them easier to control and less likely to splash. The restrictors are cheap, and just washers that replace the tap connector washers, but with a series of holes and an O ring that moves out to cover them if the pressure differential increases. They work very well, and are actually worth fitting to some outlets.

I think the reason we get a fair bit of heat transfer from the ground to the first floor is because we have a fairly large, full height (up to the internal ridge) hallway, right in the centre of the house. Both bedrooms, and their associated bathrooms, lead off from this space, so there is a fairly strong convection process running right in the centre of the house, that moves a fair bit of heat upwards. If we just had a stair well, then far less convection would take place, and there would be a fair bit less heat movement upwards, I'm sure. The devil really is in the detail I found, and trying to model or predict performance, even with powerful tools like PHPP, is not easy. I spent a great deal of time and effort trying to understand why our house, which had been modelled to death during the design stages, didn't perform as expected. There were lots of reasons, and overall our energy use is a fair bit lower than predicted, solar gain was a great deal higher than predicted and getting the controls to work for the small amount of heating needed to far more effort than I thought it would.

MVHR tends to make things dry well. We have a Victorian style clothes airer, one of the ones on pulleys, fitted in the utility room, with an MVHR extract duct above. It dries things very well. Towel rails need choosing with care to avoid excessive heating. I chose the lowest power electric elements I could find and fitted them to fairly large towel rails in the bathrooms. The circuit for these is on a timer, so they only come on for a short time each day. Tumble driers need to be of the condensing type, as you don't want a big hole in a wall pumping loads of heat out of the house, and the warm, moist air vented into a room from a non-condensing tumble drier would overcome the capacity of the MVHR to remove it quickly. Sadly, condensing tumble driers don't seem so effective as conventional ones, but that's amply compensated for by the way things dry so quickly if just hung on the airer.

I'd go for wet UFH in that case. Cheap and easy to install, allows the slab temperature to be kept nice and even, and can be run from any heat source. The electric systems are very good if all you need is comfort heating to warm up tiles on a first floor or above, where there isn't much heat capacity in the floor itself.

Low temperature UFH works exceptionally well in a low energy home, as several have shown, but there are some provisos. The flow temperature needs to be kept reasonably low for good temperature control - too high a flow temperature can lead to over shoots and poor regulation. The total heating demand for a low energy house, built to passive house performance levels, is very small, and as such natural air and heat movement around the house will tend to make all areas around the same temperature, with heat tending to rise. The MVHR will have very little impact on this, as it only moves a small amount of air and air doesn't have a high heat capacity. If building an upside down house, then consider having in-slab UFH on the ground floor, and allowing the heat to rise to the upper floors. You will probably find, as we have, that the unheated upper floor is usually a bit warmer than the heated ground floor. This is not great for our conventional arrangement, with the bedrooms upstairs, but would work well if the rooms were the other way around. Consider fitting cheap electric heating mats under the bathroom tiles if they are upstairs. They will cost peanuts to run, as all you're doing is adding a bit of comfort heating, via a timed and thermostatically controlled system, but will overcome the cold tile problem. If the bathrooms are on the ground floor then just use wet UFH in the slab and include the bathroom areas. Zone control is pretty pointless, generally, as the whole house will end up reaching an even temperature over time, defeating the point of using zones to control energy consumption. We did have a house with zoned heating years ago, and it was extremely effective, but then we kept the rooms that were off during the day closed off, the house had no MVHR and the heating requirement was many times greater than that for a passive house. Finally, I know, from personal experience, that it can be difficult to get your head around not needing a lot of heat. However, take our house as an example. In winter it typically needs around 400 to 500 W to stay comfortably warm. If the two of us move from one room to another that is a shift of around 200 W of heat input. If the house were zoned by room, the effect of just one person moving from one room to another would massively exceed the effect of the heating zone control system.

Light tubes seem to work well, but few seem very good thermally, and the one house I visited that had them suffered badly from the top part getting covered in internal condensation in cool weather, enough to drip down into the house.

That's a good point. We have a single mast 1.2 miles away, but behind a big hill. The next nearest mast is 1.6 miles away, but behind two much higher hills. I used to be just about able to get a signal, on a good day (bearing in mind that mobile signal propagation is quite heavily influenced by the weather) in two locations on site, one over by where the garage now sits, the other on top of the scaffolding at the East end of the house (nearest the mast). Neither were usable for making calls, the best I could usually hope for was a text or message alert.

The sun rises well North of East in summer, so you will get a lot of early morning light and solar gain. We have found that we get more solar gain from the windows on the East than those on the South or West sides.

I no longer have access to kit to do this sort of measurement, but can say that 300mm of cellulose inside a timber built house, plus 3G glazing that has two panes with a low emissivity (metal sputtered) coating seems to have a fairly high level of signal attenuation. The best I can do in terms of a semi-quantitive measure is with the WiFi signal. The distance and level from the router in our old house (brick and block construction, with block internal walls) to the place where I park my car are around the same. The routers are similar in terms of power. I can get a very good WiFi signal sat in the car outside our old house, but a barely usable one, that drops out often, when sat in the car outside the new house. My suspicion is that a thick layer of cellulose is a pretty good attenuator for high frequency RF. We don't have foil-backed insulation or plasterboard, so it can only really be the insulation and glazing that's blocking the signal. Opening the fully glazed front door makes a big difference, with the WiFi signal in the car increasing to a usable level, so it seems that the glazing also blocks RF pretty well.

For the dug in part, then I would look at basement-type construction, perhaps an externally insulated reinforced concrete system, from one of the specialist companies that understand how to build watertight and well insulated basements. There are a few systems around now, a look at how @Bitpipe built his house on top of a large insulated basement might help, even though I'm guessing that you will have at least one open side, the technique is much the same. From then on you just cap the ground floor with whatever system you wish (beam and block might be a good choice) and build the above ground part as you wish. The retaining wall part of the underground part needs careful engineering, and can add a great deal to the cost, depending on the soil type and the local water conditions. We had to build a large retaining wall, around 35m long and 2.5m high and the cost was over £30k, excluding some of the excavation costs.

For a new build, integrating the MVHR and ASHP unit into the same ducting seems the least worst option. It allows the waste heat from the MVHR exhaust to be further utilised by the small ASHP unit, with the two downsides being that when the hot water is being heated the MVHR runs massively out of balance (by well over a factor of ten) and the house will need to have a heating system that can supply the heat that the small DHW ASHP needs to heat the water. The latter point depends very much on the house. When heating hot water one of these units is extracting around 2 kW of heat from the air in the house, no matter how it's ducted. That's over four times our nominal winter whole house heating requirement, so unless the heating system can put the heat back into the house in winter it has to cool the house down. It's really a matter of scale as to whether this is an issue. If a house needs an average of around 10 kW of heating to stay warm in winter, then increasing this to 12 kW for the few hours a day when the DHW heating is running doesn't make a lot of difference; it's only a 20% increase. However, if the house is like ours, and only needs an average of less than 500 W of heating to stay warm in winter, then that would increase to around 2.5 kW, so a 500% change. The bottom line is that none of these units give "free" heat, they all extract heat from the house in order to heat the water. They are efficient in terms of electricity use, without a doubt, but the heat energy they deliver to the water still has to come very largely from the heating system that is keeping the house warm enough in winter. In summer this isn't an issue, in fact it may well be a benefit in extracting some excess heat from the house. It's worth noting that there are quite a few systems like this, some built into DHW tanks, as is very common in the Far East, some stand alone boxes. Availability in the UK is pretty much limited to a couple of suppliers, AFAIK.

Very true. I had all the certificates lined up on the kitchen worktop for the completion inspection. They weren't even glanced at, and the inspector didn't even want me to give him the copies I'd printed off..........

No, just a pipe that dripped waste engine oil on to a pre-heated metal plate. There was a pot underneath the plate that was used mainly as the pre-heater, and to catch any unburned oil from the plate. You'd open the small door, pour some paraffin and a bit of rag in the pot, or just some petrol in the pot (if you were brave!) and toss a match in. The trick was to let the pot get the plate nice and hot before turning on the external drip valve. There was a bit of an art in getting the drip valve set about right, as the flow rate from the waste oil tank would increase as the workshop warmed up and the oil thinned out a bit. The nice thing was that, at the time, my "business partner" (really just a mate from work who was an ace welder) and I were were servicing and repairing cars on the side, in the evenings as a second job, so the fuel for the heater was free, it came from oil changes. In really cold weather, if we turned up at the workshop in the evening and it was a bit too cold to work, we'd preheat the plate with the oxyacetylene torch to get the stove working a bit more quickly...........

Reminds me of the old waste oil heater I had in a car workshop, years ago. That didn't have a fan, but burnt used sump oil. They were in common use in garages and workshops for years, I think, mine was already installed in the workshop when we rented it. It was a tall, cylindrical affair, that would start on paraffin (or petrol if you were brave) and then when up to temperature would just vaporise old engine oil from a drip feed. Turned up to maximum it could get the top glowing red hot............... I hate to think what the emissions must have been like. The flue was just a metal pipe out through the corrugated tin roof, and was probably kicking out every toxin known to man.

I've found the spreadsheet I used and have attached it, but the online one that @ragg987 has given may well be easier to use. Rename the extension of the spreadsheet to .xls from .txt - it's only changed to allow it to be posted here. Water Usage Calculator - Master.txt

PIV is just like MVHR but without the heat recovery, plus it also needs extractors fitted to kitchens, bathrooms etc. The smoke problem would be much the same, and would depend where you managed to locate the PIV intake, just like MVHR. PIV is really a good fix for an older property that's a bit draughty and perhaps used a bit carelessly, like places where the occupants leave a lot of wet stuff hanging up to dry, so get condensation and mould problems. It's pretty inefficient, as it increases heat losses, so if you have the choice I'd go for MVHR, because the installation costs aren't going to be a great deal cheaper for PIV, anyway.

I did both the MVHR commissioning chit and the water usage chit. No requirement for a person holding any form of special qualification to do either. MVHR commissioning is a PITA, because of the tedious nature of making all the measurements that are required, but not really difficult, just repetitive and a bit frustrating. The water usage is easy, I just used a copy of a standard spreadsheet. I'll try and dig it out later and post it up here.

Probably not, as that's the very time when the reduced heat loss and improved air quality are most important. The rest of the year you can open windows and doors as required.

No, and there's no reason to, as when you want to boost the extract rate to get rid of excess water vapour is the very time when the MVHR will give the maximum benefit, by recovering a great deal more heat. This happens because moist air has a much higher heat capacity than dry air, so there is a lot more heat energy to be recovered. Depressurising the house with just an extract system will still draw air from outside, with the smoke, in, but it will come in via the leakage paths, rather than the ducts.

If you have also got a decent internet connection................. The rural problem that afflicts mobile phone, TV, DAB etc reception also afflicts broadband, sadly, so there are some of us who can't stream video over the internet, as the speeds are too low. For us, getting a box to allow the mobile phones to receive data indoors via the broadband connection wouldn't work, except for voice calls, and in that case we've be better using the landline.

The companies selling this kit are using the same loophole in the Wireless Telegraphy Act that the sellers of illegal CB equipment used back in the late 70's/early 80's, that it's legal to sell or own equipment that cannot legally be turned on and used. It seems that even something like cellulose can block high frequency RF pretty well - our WiFi doesn't work outside the new house, for example. At our old house I used to be able to get a WiFi signal in the car parked on the drive, I can't at the new house. Part of that is that newer glazing is sputtered with a very thin metal layer internally, to reflect back long wavelength IR, and this also works well to screen out radio signals. There is a big difference between mobile frequencies, though, as mentioned above. When we were working on the house the guys with phones working on the O2 or Vodafone low band were just about able to get a signal outside, those of us using EE on the high band couldn't, despite the masts being collocated, with roughly similar antenna patterns (it's a rural area so pretty much all the local masts are set up to be omnidirectional). If you're currently using an 1800 MHz band phone network, then it might be worth trying to get someone with an 800 MHz phone connection to see how it works. The frequency effect is quite marked; for example we cannot get DAB radio reception (which uses frequencies of around 200 MHz) but can receive FM radio OK (which uses frequencies of around 100 MHz).

Technically, the majority of these repeaters are illegal for use in the UK. There are a small number of certified units available, primarily (or only) available from some network providers that are legal, but the vast majority are classified as unlicensed radio transmitting equipment and their use may render the person using them to confiscation of the equipment plus a fine under the Wireless Telegraphy Act. That's not to say that I didn't buy and use one myself - but I did so knowing that it was illegal and that I was taking a risk. The risk was the same as when I used illegal CB over 35 years ago, though, and I never knew of anyone who got prosecuted for doing that (although some did, I'm sure). One issue is that the mobile network operators can, and will, shut off your contract if they discover that you're using an unlicensed repeater. Technically they can discover this fairly easily if they take the time to do some detailed analysis, but in practice I've never heard of them actually doing it and would guess that they have more important things to do than go around trying to catch people using these things if they are not causing a problem. The latter point is worth being careful about. These units can cause a problem if the two antennas are too close to each other. There's a host of technical reasons why this happens, including the fact that none of them are approved and so may well not have the required level of out-of-band rejection. What happens if the internal antenna and external antenna are too close is that there can be feedback, and, without going into the technicalities, if this happens the unit stops working plus there is a greater chance that the network operator may detect that a repeater is being used. If buying one, then you just need to be aware that if it is not a unit specifically approved by a network operator, with a valid and genuine CE mark, then it is almost certainly illegal to use. It isn't illegal to sell these units in the UK (as the perfectly legal website @reddal shows) nor is it illegal to own one as long as it isn't powered up and operating. The offence occurs as soon as you apply power to the unit, when you're then technically operating an unlicensed, and non-licensable, radio transmitter. They do vary a fair bit in quality and performance, as all these units are made in China, and some of the cheaper ones are not that great. The usual places selling these units are awash with the things, and often the actual transceiver/booster boxes are the same from many different sellers, the main difference in terms of performance is the quality of the cable and the antenna. I found that the cable supplied with the unit I bought was garbage, it was very lossy at the high frequency band that EE uses (the 1800 MHz band). The unit was designed to work on this band, but was fitted with the cheaper cable that would just about have been OK on the other, lower frequency, band used in the UK (the 800 MHz band). Changing the cable and connectors to LMR240 made a massive difference to performance, more than doubling the apparent signal strength. Changing the crap cable for decent stuff is not something for the faint hearted, though, especially for the high band kit, where you're dealing with microwave frequencies that need very good cable and connectors to work well. If you get a decent signal outside with your phone, then the chances are all you need is a simple to install kit with omnidirectional external and internal antennas. If you only get a weak signal on your phone outside, then investing in a kit with a decent directional antenna outside, and taking the time to align it properly with your nearest mast, will give better performance. I used to run a high gain yagi antenna, fitted to the top of a 12ft pole that was bolted to the gable end of our old house, in order to get a usable signal. At the new house not even that gives a reliable signal, as the hills between where we are and the nearest mast are just too high. Also, there is a very big difference between network providers when it comes to indoor performance. All the networks that use the 1800 MHz band will perform worse indoors than the networks that use the 800 MHz band. This is down to the physics of radio propagation and the fact that it is far easier to screen high frequencies than lower frequencies. So, if you're using a provider that operates on the high band, try and see if you can get someone with a phone working on the low band to visit and check their phone performance. There's a chance that that may work OK without a repeater. Finally, there is a legal way around this problem. Several companies now make devices that allow your phone to connect and work via your broadband connection when in the house. These generally seem to work well, if you have a decent broadband connection, and are a legal way to get around having no mobile signal inside the house, for those that feel a bit concerned about breaking the law, even if the risk of getting caught is pretty small.

Yes, it's one reason why aircraft fires are always doused with fire retardant foam, other than the risk from fuel. The water/heat/aluminium reaction is pretty violent, if the temperature is high enough, releasing significant amounts of hydrogen, from the aluminium + water = aluminium hydroxide + hydrogen reaction. This reaction isn't easy to start, but can be self-sustaining if the conditions are right. A high initial temperature is usually needed, plus a reducing atmosphere that decreases the rate at which aluminium oxide forms. A fierce fire is likely to be reducing at it's core, where the temperatures may also be at their highest, so in theory the conditions seem about right.

I agree, I'm not 100% convinced, but I'm tempted to do a couple of experiments to see if there's a difference between "wet" PIR and "dry" PIR. I've already got some PIR tests underway to see how the surface coating reacts with cement, and I'm tempted to do some blowtorch tests to see just how the stuff reacts to flame. Might as well compare "wet" and "dry" whilst I'm at it, just out of curiosity.