TerryE

In my (previous) farmhouse which was a ~18C stone-built construction in a village, we used to get a repeat invasion most winters as the little buggers decided to opt for life indoors. IMO, the only good indoor mouse is a dead one; the worst kind is at least one of each sex as this will turn into an infestation in weeks. So we used a mix of poison boxes, and snap traps baited with chocolate which seemed to get any incomers before they could breed. Still, it could a lot worse!

Yup Nick, however we've got a largish detached 4 double bedroom + ward storage / drying room which we keep at ~ 22½ °C all day, all year -- this may seem profligate, but we're getting old now and I just like being able to walk around in bare feet and shorts when I want without feeling cold; my wife and son ditto. As we discussed on the forum previously, if you don't have fundamental design flaws in your build (unsealed air-gaps, missing insulation, cold bridges, etc.) then the macro heat-loss is pretty straightforward: just the sum-product of area × U-value × ΔT for external surfaces + the air heating of cold replacement air -- which is basically what JSHs spreadsheet represents. The overall heat-loss is driven by the cost trade-offs on the coefficients in this calculation that you can control. As you and others have shown, it is quite possible to significantly reduce heat losses by retrofit, but in my experience this is a lot easier to achieve in a new self build where the owner has far more control over the design itself and can monitor build quality. In our case the extras incurred for going to passive standard were pretty much offset by savings elsewhere (e.g. no CH system other than the in-slab UFH loops -- my entire heating system cost about £2½K and is pretty much maintenance-free). Even though 90+% of our electric heating is done at off-peak rate E7 tariff, with the expected tariff increases when our fixed price contract finishes, the ~4-5 MWh that I could save by installing an ASHP might just about cover its investment cost so long as I do the install myself. As Joe said on another post, IMO dot&dab boarding out counts as a major design flaw, as this is rarely done as the videos on YouTube demonstrate, and too many internal thermal images of such external walls show that these voids often act as a large plate heat-exchangers dumping heat into void behind the plasterboard where the external draft air circulating here carries it out as convective losses. If you must use a conventional blockwork + insulation + external brick skin, then going for wet plaster on block if a far safer option, as well as making sure that all interfaces are properly taped during 1st fix.

TBH, this is because of crap quality control during typical builds. Our actuals are closer to 0.5, because we designed in airtightness into our build and made sure we chose subs who knew how to build to this standard. You posted elsewhere that you are still in the planning phase so what targets you design your house to and how you implement this is still very much under your control.

I would have cast that slightly differently. If you are truly losing 4 ACHP with no heat recovery, then this will be by far the largest source of heat loss. Think of your house as a system: it has to be in balance. There no point in having fantastic windows, etc., to keep the heat in whilst at the same time letting it escape through every crack in the house if there is the slightest wind. I have a passive-class house which is maybe 40% larger than yours, and our energy expenditure is just over 11 MWh p.a., (This is all electric, of which about 60% is resistive space heating – I can't make a case for installing an ASHP even though we've allowed for one in our initial design). Even with ~ 90% heat recovery, our MVHR circulation accounts for about a ⅓ of our heat losses. I would suggest as an option that you consider retaining the MVHR, but look at what mitigation you can do to get your ACHP under 1. You will find this will get you a more balanced system, and a more comfortable house as well as lower bills. BTW, in my case my FP contract with OVO will more than double in October which tilts the cost benefit case and so we may be installing an ASHP over summer. ?

NodeRED uses connect-the-block pre defined modules to implement control. Lots of YouTube videos on it. You can do complex stuff in JavaScript which is pretty straightforward if you've ever done any programming.

Having an in-slab UFH implementation helped us a lot and made everything pretty simple. We've got a 3 storey detached house with four largish bedrooms and one storage / drying room with the heating requirement peaking at around 30 kWh in the winter months (and little solar gain because of our house orientation and planning constraints). If we heat only in the E7 window, that's just under 4kW net heating, and the thermal mass of the interior is such that this gives us ~1°C ripple on room temperatures. If we don't heat the house (an accidental experiment) then it cools overall by around ~1°C per day. This all depends on the "devil in the detail" during construction: all insulation installed to spec; decent air tightness, MVHR; no oops thermal bridges. A constant heating strategy would peak at ~1½ kW so IMO a typical small 8 kW ASHP would be total overkill. I don't know what the true replacement life of an ASHP is, but it would need to be 10 years or so for us to justify its procurement and installation cost. Over 4 years in and I have made a few tweaks to our system: The CH + DHW is controlled by a dedicated RPi using Node-RED for sequencing etc. We have added a Home Automation System (HAS) running on another RPi and using Home Assistant with lots of ZigBee devices doing the usual home automation stuff. This system also controls an Oil-filled electric radiator we have on our 1st floor landing which we run 0-7 E7 hours in the winter; this uses a smart plug which also reports actual power used. This rad plus E7 Willis Heating keeps the whole house nice and toasty. The HAS and CH systems use MQTT to swap set-points and logged data, but it's all set up so that the CH system will still run happily if the HAS isn't available. This automation approach might seem complex, but the H/W and install costs were in the few £100s. It all works pretty much automatically with minimal maintenance. The biggest wobbles to our system are caused by visitors staying, such as one of our kids + family, as this adds an extra 4 bio-radiators that move from room to room and can cause local over-heating if we all sit in one room for too long. The simple answer here is passive-house heresy: open a window or two for a bit to dump the extra heat.?

There's a parameter in your /boot/config.txt which can be used to override the MAC addr: smsc95xx.macaddr=<whatever valid addr you want>.

IMO, the whole concept of zones gets very questionable as the spec of your house approaches passive class. It is a bit like trying to maintain storage zones inside a thermos flask. The internal heat flows are an order of magnitude greater than external losses. We run our 3 floor house as a single zone which is heated by the slab. My control system circulates water around the slab for 10 mins every hour when not heating. This redistributes slab heat from solar gain and enables taking an accurate average slab temperature. The only real exception to this is the floor to floor heat gradient in colder months, as the 1st and 2nd floors do tend to be a degree or two colder than the ground floor, but I trim for this with a couple small oil-filled electric heaters on the two floors and they turn on for a few hours overnight on timers and add a few kWh of space heating on each floor. The 1st floor one sits in the doorway of my office and this boosts the entire 1st and 2nd floors. My son occasionally uses his in his top floor area.

You really need to do the sums for a sketch design. Search for Jeremy Harris spreadsheet on this site. I have a 3 storey passive house with underfloor heating. Our heating days are quite high but the actual amount of heat is quite low (we heat the house with a Willis -- which is essentially a 3 kW immersion heater in a jacket.) At the moment it's on for maybe 3-4 hrs a night at E7. However, we have little solar gain because of the house orientation and planning restrictions limiting the area of windows facing SE (and non on our S/W gable). The same house with larger windows on a south facing principle axis wouldn't need any supplemental heating at the moment. You really can't generalise, but a properly constructed passive house should be within 10-20% of this rough-cut estimate. The caveat here is the "properly constructed" as the devil in the detail. If you've got building flaws which result is thermal bridges, missing insulation, significant air leaks, etc. then your actuals could be way off.

@Bramco, I see that you've just done a like on my Heating the Slab – an overview post. After over 4 years the system works pretty much faultlessly. The 3 storey house is heated by what is essentially and immersion heater. The one tweak I have added is an oil filled rad in my office on the 1st floor which my home automation system turns on for a few hours overnight to add a bit of space heating for the upper floors (and more in cold snaps). Without this the temperature can drop below 20°C which is my comfort threshold. This actually works out cheaper as only need to supplement heating outside of E7 rates in the absolutely coldest weeks. Using resistive heating like this isn't really efficient in terms of run-rate as it costs us about £700 p.a. for space heating, but the upfront installation cost was pin-money, and zero maintenance because of no moving parts (I do have a spare Harvey heater for cold-swap if the current one fails.) Adding an ASHP might drop this energy cost by £500 p.a. or so, but at an upfront one-off cost of £5-10K for installation of a piece of kit that might just have a 10-year life. There is no economic case here. Our slab input temperature rarely gets above 35°C and if we were spreading our heating throughout the day then an ASHP with <5kW output in the range 30-35°C would be fine. Most installers wouldn't understand a house that operates in this domain. Our house pretty much exactly performs as the simple heat calc predicted -- we've got maybe + 20% on the slab losses due to a thermal bridging flaw discussed in the blog, but this is small-beer overall. And yes, air heating of leak churn is a big component. IMO using MVHR is pretty essential. This allow you to have an air-tight house but at the same time keeping it fresh and avoiding the damp + stuffiness that you would get without it.

Yes, you can pass SAP with electric only heating (at least the 2016 Rev), but you really need a passive-class house to make the numbers work.

It really depends on the internal moisture content within the walls. My last house was ~300 down to 150 year-old Cotswold-like stone around 600 mm in depth, with the internal face rendered then hard plastered. We had an injected DPC that worked really well: when we moved in the infill was like damp soil; within 10 years it had entirely dried out to a mix of grain husk and clay powder. Based on heat losses I reckoned the U-value was around 1.0 once dried out. Still a bloody cold house though to heat! You also be better off with MVHR than vents. That would also mitigate / remove any dampness.

Nick, you've got to admit it: you are just another cantankerous old man ? My kids would unanimously stick me in that category as well.

We have acoustic insulation between the rafters and in the internal stud walls. The floors still tend to drum.

@Russdl Thanks to our planners objecting to the impact on the street-scene, we had to drop rooftop PV from our plans, and so we are import only.

I've got an MBC TF with external stone skin. I don't have any issues with room-room noise except between floors, and this is because ecoJoists seem to be very effective at transmitting noise vertically. We have 12mm board. You can get a range of decent wall fixings which typically butterfly or balloon in the void, and some are rated up to 25 Kg per fixing, so we've never had any issues with fixings.

I am fairly lucky in that I planned to switch to the Agile Tariff, but had to wait until my meter got upgraded to SMETS2. In the meantime, the Agile rates went through the roof, so I aborted this plan. I am just entering the second year of an OVO fixed price tariff at 9.19p / kWh night rate (about 70% of my annual usage) and 15.81p / kWh day rate. Sometimes the dice roll for you. With my house system, I could easily implement supplier-friendly demand shaping, but I see no point without adequate price incentives.

As soon as you start instrumenting a house and wanting to do more them IMO, it is just easier to bite the bullet and install Home Assistant on an RPi 4. You get a Zigbee dongle for it and Zigbee thermometers cost a few £s each. No need for any wiring fabric.

Modern PIR + IR nightlight cameras are pretty low power these days. I've got a bunch of Reolink PoE cameras and IIRC the power draw is less than a quarter what the exterior CAT6 is rated for, and well with the specs of my PoE switch. In fact one of my cameras uses an existing 5m run of pre-laid CAT5E -- it's buried under the block paving drive and it was just easier to use it rather than lift and re-lay the paving (if it worked that is). I've had no problems with it.

True now, but not when I configured mine. My point is that 1Gb for a single link is ample, so don't get into sweat over 5E Vs 6 for internal wiring. If you are wiring everything as a star into a switch, then the issue is switch capacity which is nothing to do with the fabric bandwidth. My main point of that you don't need to be too worried about uplink bandwidth: if you are pumping that much data into the cloud then that's a serious concern in its own right. It is your data. Don't give it away lightly.

Maybe I am old fashioned, but for the life of me I can't see the advantage of such a high bandwidth uplink other than running a largish business. I planned out my house 6 years ago and used Cat 5E internally. The internal Enet links all run at 1Gb. I've a PoE switch in a shed and all of my cameras are wired back to it using exterior grade Cat 6. They FTP their snippets back to an internal file server. I don't really backup or use 3rd party services off-site (just on-site). My remote access is via a VPN service from one of my RPi4 servers.. For the life of me I can't see the advantage of putting my balls on a plate, and offering them gratis to some 3rd party with whom I have no effective contractual remedies.

As old Ronald Reagan said: trust, but verify. ?

We had an external stone skin added to our TF the following summer. Our windows were triple glazed Internorm Aluclad. One thing that we did do was to cover them all with a building grade polythene protection pretty much soon after they went in. The last stage of the stone work was to careful cut around the widow frame / stonework junction, remove the polythene sheets then do the final pointing fillet.

That's what we did just under 5 years ago. Our TF included a warm roof 3rd floor which was sarked. The frame and windows were erected in Nov. The slates went on in Feb. No probs at all.

As old Ronald Reagan said: trust but verify. Actually doing the calibration was a very useful confidence exercise and meant that I could have trust in the sensor outputs. I've zero problems with my DS18B20-base temperature acquisition in the four years that I've been using it.