Jeremy Harris

For info, these are the AICO units I used: https://www.tlc-direct.co.uk/Manufacturers/Aico/Smoke_Alarms_Mains_Alkaline/index.html Not expensive, and dead easy to unclip from the base to change the backup battery. You can also use a lithium PP3 backup battery, rather than an alkaline one, that increases the battery shelf life a fair bit.

I deliberately chose the mains powered AICO ones that use a PP3 backup battery, as when the backup battery needs replacing you don't need to replace the whole alarm unit, just the battery, and this can be done as easily as changing the battery in a non-mains powered alarm. I believe the ones with the hard wired back up battery are designed for use in rented or social housing, where there's an anti-tamper requirement. They all wire up the same way, as far as power and the inter-alarm interconnect is concerned, so should be a quick and easy thing to change.

Mineral wool is going to have both a lower U value than the SIPs panels and be subject to windwash, so although easy to fit there will still be a thermal bridge at that corner. Corners really need better insulation than flat areas, because of the hard to avoid geometric thermal bridge they create.

Pretty sure I have a spare brand new AICO smoke alarm, as I made an error when buying them and bought two smoke alarms instead of one heat alarm and one smoke alarm. The box has been opened, as I only discovered the mistake after installation, but as all the AICO units use the same backplate it was easy to just swap the smoke one out for a heat one.

Depends. Our mains powered and linked smoke/fire alarms have a lithium PP3 back up battery, that should last around 5 to 8 years. It looks easy enough to replace, pretty much the same as replacing an ordinary smoke alarm battery.

It should be fairly straightforward to cut wedges of insulation and fill the triangular gap. ideally using low expansion foam to seal and secure the insulation. If the insulation is extended out beyond the outer edge of the inner SIPs wall then that will help to reduce the geometric thermal bridging, too. I did this at our eaves, and fitted additional insulation inside the eaves ladder frame overhangs, just to reduce geometric thermal bridging in the inner corners.

Have a read of @dogmans recent post (we used the same company and were very pleased with them, so I'm a bit biased!):

In general, there isn't a requirement for a competent person to do any work on an electrical circuit that operates at ELV (or SELV), which is one with a voltage below 50VAC or 75 VAC (under the LV Directive) or 120 VDC (under BS7671). SELV has lower voltage limits so is covered by the ELV rules. Having said that, there is still a requirement that any ELV or SELV circuit is safe and functional, particularly in the case of a fire or smoke alarm, as the functionality of those comes under fire safety regulations, rather than wiring regulations. As such, I'm not sure I would be comfortable, as a landlord, allowing tenants to do any work on such systems. ELV lighting is less of a concern, but there are still fire risks associated with the installation, so although the regs may not require a competent person to do the work, again I think I'd be concerned, were I a landlord, that a tenant could screw up. One easy error to make would be for a tenant to replace something like a 12 V LED MR16 lamp with a 12 V halogen lamp, that then overloads the capacity of the ELV cable supplying the fitting. In an ideal world the transformer running ELV lights would shut down and protect the wiring, but I bet there are a lot of older 12 V downlighter installations that have re-used the original halogen rated transformers, and some may well have had the original heavy gauge wire replaced with something lighter (and cheaper) on the basis that LEDs were being used.

What does the architect say about fixing the massive thermal bridge at the eaves? It needs resolving, as there is definitely a significant condensation risk there, right where the roof imposes loads on the wall SIPs panel.

There are potential gotchas in Part L1A of the building regs for an all-electric house, that can make it challenging to not use a heat pump or fit PV. I know we often say that Part L1A isn't a great standard for modern house performance, but in real terms it isn't that bad, either. In terms of whole house heating requirement it's about 3 to 4 times higher than a passive house, which is massively less than a house built 20 or 30 years ago, and much of that difference comes from the much higher ventilation heat loss. More importantly, though, is the penalty imposed for all-electric heating with no renewable generation. This would almost certainly rule out resistance heating unless the house was made airtight and insulated to close to passive house levels. Adding some PV makes a big difference as far as getting the energy use down in SAP is concerned, and is one reason why many new builds have a few panels on the roof - they are there to get an adequate SAP score without needing to air test new houses (which really means not having to make them properly airtight). Airtightness is, if anything, more important than insulation. If our house just met the Part L1A airtightness requirement, so had no MVHR, it would need about three times more heat in winter. It's very well worth looking at the trade offs between construction cost (better insulation and airtightness), heating requirement, heating options and how these all impact on the SAP score, particularly for an all-electric house where it's already challenging to meet the requirements now. You may well find that you're driven to use an ASHP with a house built to just meet building regs, because it would not pass if fitted with electric resistance heating. On the topic of oak frames, I know at least one passive house company that can supply oak internal frames for their passive house kits, so it may well be an option to consider. I suspect it's a cheaper approach than the structurally wasteful SIPs over oak frame option, which always struck me as being just an idea that one oak frame company came up with as a way to continue to sell their standard oak frames yet still meet current building regs requirement (there are issues with oak frame movement over time that make it easier to have two structurally independent "frames" like this).

It's the pressurised volume rule - the heat exchanger coil is the only pressurised part and will be under the volume limit to require a G3 sign off, as I understand it. The bulk of the water in the thermal store will be unpressurised and vented via the header.

It depends. A pressurised cold water system, like we have, doesn't require a Part G3 sign off, and can be done as a DIY job. The same goes for a thermal store hot water system, if the thermal store itself isn't pressurised, and for a Sunamp PV; none need a Part G3 sign off or annual inspection. You only need a Part G3 qualified installer, plus annual inspections, if you fit an pressurised, unvented hot water cylinder.

I could relatively fairly easily add an external RH sensor, I think. I already log ASHP flow temperature, floor temperature and outside air temperature just above the intake to the ASHP on the North face of the house. Currently the logger records a set of readings every 6 minutes, and stores the data in 1 month chunks, using a GPS master clock to keep the timing consistent.

As I read the water regs, it's no longer legal to supply potable outlets (typically cold water to the kitchen) from an open or vented cold water tank, irrespective as to where the water comes from.

Worth trying teak cleaner to see if it brings the colour back: http://www.teakcleaner.co.uk/

The general rule of thump is that the usable near-constant pressure volume from an accumulator is around 50% of the total stated volume. The pre-charge air pressure has to be adjusted (using a tyre pump) to adjust for the operating pressure, typically it will be set to 1 or 2 psi below the max water pressure.

They only have a single connection, so can only be plumbed in parallel. Each 300 litre tank holds about 150 litres of water under pressure, as the compressed air behind the bladder uses about have the volume. With a non-return valve on the mains inlet the accumulator(s) will charge to the highest available mains pressure during mains pressure peaks, usually overnight. The outlet from the pressure tank(s) (really just a continuation from the tee at the base of the connection to it) works just like a cold mains input, but an a constant pressure until the tank(s) empty, when the pressure will drop to the incoming mains pressure. It can split to feed both the hot and cold system, using a mains pressure hot water heating system, such as a combi boiler, UVC, thermal store or Sunamp PV. The advantage is that the pressure is then the same at all hot and cold taps, which makes mixers work well.

I've told this tale before, but it's worth repeating. We had an open weekend where around 40 people came to look around our house. One of them was a lady who had finished building a Touchwood Homes house a year or so before. She'd insisted on having a wood burning stove in the living room, the smallest room sealed model available, which I think was rated at about 4 kW. They lit it for the first time on a Christmas Day, and within an hour the living room was over 30 deg C and they had to leave the room, even with all the windows open. it took several hours for the room to cool down enough for them to use it, and messed up their Christmas a bit. Since then they've never used the stove again and last time I heard she was looking at getting an LCD monitor installed in it to display a flame effect.

My experience has been that the published COP curves are unrealistic, as the killer is humidity, rather than temperature, and it's hard to get hard data for the combination of the two and the way the defrost systems impact on COP. I spent a lot of time fine tuning the settings on our ASHP, and in the end managed to get it working so it very rarely, if ever, defrosts. This has a massive impact on COP, as the defrost cycle runs the heat pump in reverse for around 10 minutes, pumping heat out of the house, so just one defrost cycle per hour knocks 30% off the true COP. Our ASHP has temperature and RH sensing at the air intake, and uses some form of combination of the two, together with the heat pump operating power, to try and predict when a defrost cycle is needed. I found by experiment that adjusting the weather compensation to remove it, and setting the heating output temp to 40 deg C, resulted in virtually no defrosting for our installation. Our ASHP is significantly over-sized for the heating requirement though; it's a nominal 7 kW rated output unit that rarely needs to deliver more than 1 kW to the floor heating. I worked out that it just wasn't worth paying the big premium for an MCS install, as for us the RHI would only have been around £80 or so per year for 7 years, and the MCS premium was well over £2,000. I knew nothing about installing these things and had it installed in a day, just two pipes and two cables, it really couldn't have been simpler. I did spend a lot of time tuning it to improve the COP though, and it now runs at over 3.5 on average and exceeds 4 from time to time.

What I find odd is that the product looks really good. The chap on their (old company) stand at Swindon was happy to demonstrate how it worked and I have to say I thought it was impressive, very quick to install from what I could see, with high quality components.

Pretty much any of the big name brands (Panasonic, Mitsubishi etc) inverter controlled ASHPs will be reliable and easy to setup. If you want really hot domestic hot water, then the Daikin hybrids are worth a look - they have a gas boiler internally that boosts the DHW temperature, and can run on LPG. The advantage of them is they don't use a lot of gas, as they use the ASHP to preheat the water and only use the gas boiler to add an extra 10 deg C or so. Fan noise from our inverter controlled ASHP is really low; we've had people stand next to it and not realise it's running. Ours is a re-badged Carrier (another really big name in heat pumps - Willis Carrier was the chap who first introduced air conditioning using heat pumps over 100 years ago) and several companies sell the same unit with a different badge on the front (ours is badged Glowworm, but identical units were badged Kingspan and a few other names). In terms of cost, our ASHP (self installed) cost around £2k all in. The cheapest borehole GSHP quote we had was £8k, not including the cost of drilling the hole.

Worth talking to one of the SEs that are familiar with passive slab design, though, as you may find that you can just increase the depth of stone under the insulation to both reduce the bearing load and get below the heave zone. It's usually a fair bit cheaper and quicker to just add more stone than it is to bring in a piling rig. We costed up using piles and they were going to be both more expensive and take longer to put in than just digging out the base area a bit deeper and adding stone.

Unless you're on clay that's prone to a lot of heave, shrinkage and movement, then I'd have thought a passive slab would be cheaper, quicker and a lower risk than piling. A passive slab can be made to work with poor ground conditions by just increasing the depth of the crushed stone sub-base, and generally imposes a low over bearing load on the underlying soil, making it idea for most poor ground conditions. It's a concept that is still relatively uncommon, as it's only been around for ten years or so, and the building industry seems to be very reluctant to accept anything "new", but our house is built on gault clay with a passive slab an the foundations took 4 days to put in, start to finish (including fitting all the ground floor UFH pipes).

We have an ASHP about four feet from the back door, and you can't hear it from there when it's running normally, so noise isn't really an issue with modern inverter controlled ASHPs. The noisiest heat pump I've ever heard was a GSHP, that was so noisy that the owner ended up moving into an outbuilding to reduce the noise level in the house. In terms of efficiency, then the worst case for ASHP is just above freezing, with damp air, where it may start to run defrost cycles unless it's set up properly. Set up is key to getting good performance I found. Cold air makes very little difference to performance; air at -5 deg C only has about 5.3% less heat in than air at 10 deg C, not enough to make any noticeable difference in performance. I worked out that there was no way to ever recover the much higher, purchase, installation and maintenance cost of a GSHP (running from a borehole) over the very much lower cost of an ASHP over its lifetime.

You were also fortunate enough to be able to get a tank over 30ft above the ground floor outlets to give you 1 bar. Our house has no loft, so there's nowhere to put a tank to gravity feed taps on the first floor, and the highest pressure we could get from having a tank in the services room to the ground floor taps is about 0.25 bar. According to the MI's, that's too low to operate our dishwasher or washing machine, both of which need 0.5 bar minimum. As well as the issue of not being able to supply drinking water from a vented loft tank, so needing some form of treatment for any potable water outlet, there's also the issue of needing large bore pipes to get a decent flow rate. Our two 300 litre pressure vessels store potable water at 3 bar, which means we have plenty of pressure available to get a high flow rate using smaller bore pipes, which in turn means that we have less time to wait before hot taps run hot, as the pipe volume is smaller. We also have potable water from every outlet in the house.