Jeremy Harris

No, no vent stack at all, as it's a passive house, so adding one would have created a big thermal bridge. Instead we have an internal air admittance valve on top of the internal soil pipe stack, that opens and draws a tiny amount of air in from the loft space if there is ever a partial vacuum in the pipes cause by a toilet flushing.

UFH heat loss downwards can be high unless there is a decent level of insulation underneath, as UFH increases the heat loss rate through the floor when compared to other forms of heating. As an example, we have 300mm of EPS insulation under our 100mm thick floor slab (which has UFH pipes embedded in it) and we still lose around 8.5% of the heat that we pay for down through the insulation into the underlying ground. We live with the heat loss, but I'd not want to throw away more paid-for heat energy by having any less insulation under the floor.

No, no response. TBH I've sort of given up and to start with I'll just build-in a timer to do the job. When I get a bit of spare time I'm going to look at making a hot water charging unit, as an add-on, that connects to the lower power heat exchanger. It should b easy enough to build and test such a unit without having to connect it to the Sunamp, so I can iron out any bugs. Should be an interesting exercise, getting the control system to work OK.

So glad you said this, as I'd been looking at the drawings and thinking exactly the same, but didn't want to be overly critical. It seems to me that there are simpler and cheaper ways to achieve much better thermal performance without all the thermal bridges, if it's not too late to change the design. @Lots2learn, as an example of a very simple foundation that has no thermal bridging and very much better thermal performance, have you looked at using a passive slab? Quick and easy to lay for a lot of soil conditions, inherently good in terms of thermal performance (ours has 300mm of EPS under the slab and 200mm of EPS around the edges of it) and there can be significant saving in ground works cost, too, which offsets the slightly higher cost of the passive slab itself.

No, they don't. All three phases are separately metered, so you can be exporting on one phase and still importing on another.

I had a go at trying to work it out, for the various different options we were looking at, but in the end found that keeping track of it, and working out the offset over the life of the house, just got to be too much work. The house build itself has a pretty low embodied CO2 level, mainly the concrete slab, but that's only 100mm thick, the steel reinforcement in it and the EPS insulation underneath it. There are no fired bricks or cast concrete blocks in the house itself,. The frame is built from sustainably certified timber, the cladding is locally grown (6 miles away) and locally milled (3 miles away) larch, the wall and roof insulation is recycled newspaper and the roofing is recycled plastic slates. The internal flooring is a mix of bamboo (which is grown from sustainably managed plantations) and travertine stone, but both came from miles away (Taiwan and Turkey respectively), so had a fairly high transport C02 contribution. We do manage to offset this to some extent, as overall the house "produces" -0.9 tonnes of CO2, which means that it will end up "repaying" its build CO2 debt within a few years (I might sit down and try to estimate how long that will take). In simple terms, our house is roughly the same as having over 40 mature trees on our plot, in terms of its CO2 impact, except we couldn't have fitted 40 matures trees on it even before we built the house. The hardest part to work out I found was the transport CO2 impact. It's really hard to find out exactly how goods were transported from far away, especially when there are multiple journeys involved. For example, the timber in our frame was grown in Sweden, probably milled there, then transported to Ireland, where it was made into the frame of our house, then the frame was transported by truck and ferry to our plot. That's a lot of travelling for what is component that was grown in a sustainable woodland. I've no idea how much CO2 went in to turning harvested bamboo into flooring, not do I know for sure how it got here, but can guess that it would have meant a truck ride to a port, a 4 to 6 week sea journey in a container, then a couple of other truck trips within the UK before it got to us.

We have a Biopure unit, with an air blower. I looked at the passive systems, but having read reports of smells from some of them, and the importance of siting the vent pipes in a way that both ensures good air flow and doesn't result in smells near the house, I decided to bite the bullet and just get an air blower unit. Our treatment plant is barely 7m from the house, around 1m from the edge of our drive and maybe 2m from the adjacent lane. There's no smell at all from it that I've been able to detect. We have no vents on the foul drain that runs down to it, just the vent on the top of the lid. I believe that the key to reducing odour is to ensure that the unit is always operating as an aerobic digester, with plenty of excess oxygen to ensure no part of it is ever anaerobic. It's worth noting that septic tanks are inherently anaerobic, and this contributes a fair bit to the odour that some can allow out through the vent if the crust is disturbed. I believe that the biggest challenge that passive-type aerobic treatment units have is getting enough air into the effluent. It's hard to beat the effectiveness of a relatively low power air pump when it comes to both aerating and causing the internal effluent to circulate all the time. In terms of cost, our Biopure cost around £2k, plus about another £1k for installation.

Thanks, not sure what on earth happened there. I haven't checked my profile for ages, so thanks for spotting that it had somehow got messed up. I've added a bit of up to date text in there now.

You're pretty much spot on, in that there are a real mix of people here. The only golden rule really is that we don't allow people to advertise on here, so those who work in the building industry and post here have agreed not to tout for business. I don't think there's an easy way to find out who's done what, unless they have added information to their profile. Checking everyone's profile would be a bit tedious, though. The build and renovation blogs section here is a useful guide as to who is doing what, though, plus some of us have blogs hosted elsewhere, perhaps with links to them in their signature, although mine is now a bit out of date, as we've completed our build, moved in and there's not been much to write about recently. The Private Message (PM) facility allows you to directly contact a member, if you need to have a private conversation. My personal view is that it's better to ask questions on the forum, rather than by PM if you can, as that way you're likely to get a better range of answers. PMs are useful if you want to arrange to meet someone, or have a look at someone else's build, something that a fair few of us have done over the years.

You should now see that the number has gone from zero to one, as I "liked" your post. That number is intended to indicate the reputation of members, very roughly, by indicating how many times someone has reacted to a post. Not sure that it's a very good guide, though, as a fair few reactions will from laughing at jokes.

Good move to stick with radiators, as the losses will be a lot lower than with UFH. UFH is nice, and removes the obstructions that radiators can cause, but it's never as efficient, as there is always some heat loss through the floor, even with pretty good insulation. We have 300mm of EPS under our slab yet still lose about 8.5% of the heat we put in to the UFH down into the ground under the house.

You can. My old compressor ran on one for years. New they are pricey, but I picked up an old second hand one pretty cheaply. All that was in it was a transformer and some big capacitors, IIRC, plus a starter relay that switched in extra big capacitors to handle the motor start load.

I agree, well worth ringing the planning officer. I decided to do this a week or so after the end of the consultation period and the planning officer was kind enough to email me his draft report. In it he mentioned the removal of PD rights as a condition, so I rang him, asked why PD rights were being removed and he said it was an error, from when he'd cut and pasted some text in with the standard conditions they apply. He emailed me a new copy of his draft with the PD rights condition removed, and that version was the PP that was eventually approved. It would have been a nuisance to have accidentally had PD rights removed, as it would have meant submitting a new planning application for doing pretty much anything after completion, even erecting a garden shed, so the phone call was, in my view, well worthwhile.

For some reason I can't get the spreadsheet download to work from the blog any more, not sure why, but something seems to have gone awry with the Wordpress database and is beyond my ability to fix. However, the heat loss spreadsheet is here: Heat loss calculator - Master.txt Just change the file suffix from .txt to .xls after downloading it (the forum has a problem with spreadsheet files as attachments). I also knocked up a UFH calculator that may be helpful: Floor heat loss and UFH calculator.txt Same as the other one, just change the suffix after downloading.

Depends very much on the properties of the surrounding soil, though. Some soils, like any very dry soil, are not very good thermal conductors, others, like any wet soil, usually are. In general any wet soil will be a reasonably good thermal conductor (as borne out from experience with ground source heat pump collector loops), and anyway, there's no form of soil type adjustment allowable when calculating floor U values, AFAIK. The assumption is that the ground temperature remains fairly constant, something that seems to be borne out by measurement. We are on solid clay, and the ground temperature under our slab stays at a pretty constant 8 deg C all year around, not varying by more than about half a degree, if that. The U value of the fabric is the U value of the fabric, and doesn't change just because of a change in the temperature on either side. If the temperature differential changes then the heat loss rate for a given U value changes. It would seem reasonable to use floor limiting and notional fabric U values from Part L1a for a basement wall, as the conditions are near-identical. There's also the point that meeting the limiting fabric U values in Part L1a may well not result in an acceptable TFEE/TER. That's one reason why there are also a set of notional fabric U values in Part L1a, to give a guide as to the sort of values that may be needed in order to get an acceptable TFEE/TER. The actual values are: Limiting fabric U values: Wall = 0.30 W/m².K Floor = 0.25 W/m².K Roof = 0.20 W/m².K Windows = 2.00 W/m².K Notional fabric U values: External walls = 0.18 W/m².K Floor = 0.13 W/m².K Roof = 0.13 W/m².K Windows, roof windows, glazed rooflights and glazed doors = 1.4 W/m².K Opaque doors = 1.0 W/m².K Semi-glazed doors = 1.2 W/m².K From the above I'd say that the target to just pass building regs requirements for a basement wall and floor should, perhaps, be the notional fabric U value for a floor, so around 0.13 W/m².K. Having said that, most basements will be very airtight, so there is a margin to trade off the reduced ventilation heat loss against the fabric U value, in terms of meeting the TFEE/TER for the whole dwelling.

That's one reason I mentioned that each company (in England and Wales - as I mentioned earlier - Scotland and NI have a different system as they weren't privatised) has their own set of policies that they apply. One thing they are keen on is ensuring that any pipework etc that they will have to adopt at a later date (i.e. communication pipes laid within a development, for example) meets their requirements. In your case it looks like Anglian Water Services Ltd won't fit a water meter until they have inspected the installation for compliance with the regs, but as I understand it you already have a water meter fitted. How are they to know when you've finished and have the supply connected to the house? More to the point, I'm not sure what they can really inspect, as by the time the house is complete almost all the plumbing may well be hidden and out of site from any inspector that comes around. Building control may or may not want to see the water usage calculations. One of our building inspectors was a PITA about ensuring flow restrictors were fitted on every outlet, but I'm inclined to think he was just an anomaly, as others don't seem to have had any hassle like this.

As this is part of the SAP/EPC undertaken by an assessor, I'm not sure how, or why, building control can make any notional adjustment like this. We have at least one assessor on here, who may be able to shed some light on this, but my experience was that building control required me to produce both a design EPC and get the as-built EPC lodged on the database; they had no involvement at all in ensuring compliance with Part L1a apart from getting the paperwork and checking that what was built matched the drawings and spec, although even then they didn't inspect the insulation level.

First off, "water boards" ceased to exist in England and Wales a few decades ago, so you're dealing with a privately owned utility company, and although the regulations are the same for all private utility companies, each has it's own set of procedures and policies that it will apply, and they may well place additional requirements on customers over and above those that are mandated by regulations. This means it's hard to give a definitive answer unless someone here has direct experience of the way your utility company, Anglian Water Services Ltd, does things. In general, water companies aren't too bothered about what happens after they have connected a meter and set up your account. You'll be paying for water that you use, plus an availability charge, plus a sewerage disposal charge (if you're on mains drainage owned by the same water company) from the time that the meter is installed, so it doesn't really matter what you connect to the pipe. Having said that, you are obliged to adhere to the regulations when it comes to installing your side of the water supply, and that means things like using the correct type of NRV that the water company specify (most require a double NRV just after the meter) and ensuring that all your pipework, fittings etc are WRAS approved (almost all are). None of this is really anything to do with the water company though (except their requirements for the type of NRV), it's just a matter of adhering to building regs, specifically Part G and Part F.

We have a stream along one boundary, so the EA had a big say in the levels of both the finished floor in the house, the drive parking area and the garage floor level. They mandated levels above Ordnance Datum that we couldn't go below, and that ruled out a basement. The daft thing was that I was required to do a flood risk assessment, and that showed that even the 1:100 year flood risk level was only just covering part of the lane below our house - the EA made us have our FFL in the house 1.6m above this, which is daft, as the stream is small and fed from a spring about 3/4 mile up the valley.

Why does the fabric U value change just because it's a basement? All that changes is the temperature differential, with the ground being around 8 or 9 deg C or thereabouts all year around, so there is heat loss all year around too. A quick and dirty calc gives a U value of around 0.22 W/m².K. If the room temperature in the basement is maintained at 20 deg C, and with a ground temperature of 9 deg C, that means the basement loses around 2.42 W/m² of wall area 365 days a year. Not sure how much insulation you have under the floor, so I can't work out the floor heat loss per unit area. We have 300mm of EPS under the floor, with a 200mm wide upstand around the edges of our slab, which is contiguous with the 300mm of insulation in the walls. Our floor U value is 0.0975 W/m².K, and, because we have UFH, we still lose about 8.5% of the heating energy we put in down through the floor, rather than into the rooms.

Yes, the pre-heat does come out of the heating part, as it's the buffer tank for the heating that's used to pre-heat the water in the heating season. In the non-heating season there's enough excess PV generation to not need the pre-heat for DHW. I aimed to meet or exceed the performance requirements for a certified Passivhaus, without incurring the additional costs associated with getting PHI certification, so overall I've been pretty pleased with the way things have turned out. It has been a process of tuning things to reduce energy use though, as initially I fitted a big water filled thermal store, and that had losses that were only a bit less than our DHW usage, even after I'd added a lot of additional insulation to it. Fitting the Sunamp really improved things as far as DHW goes, as the losses are much lower, which has a significant impact on our DHW energy use. With the thermal store we'd have been using around 65% to 75% more energy for DHW, much of which would have been lost, as we had severe overheating problems in the service room and the adjacent bedroom, so much so that opening the bedroom window, even in mid-winter, was the only way to get that room to a bearable temperature.

Roughly, yes, based on actual generation data plus estimated consumption data, the latter having changed a fair bit since we moved in permanently from increased energy usage for hot water and cooking, but decreased energy usage from not charging my old car here every day (the two don't quite balance out). Our total generation comes to around 5,800 kWh/year. We manage to self-consume around 2,000 kWh/year at the moment, but I'm aiming to increase that significantly if I can. Our export is way over the deemed 50% that we get paid for, at around 3,800 kWh/year. Being able to utilise some of that export with battery storage is one thing I'm looking at, plus a bit of it will get used to charge the car.

I'm happy with OSB that's been given a few spray painted coats of white emulsion in my workshop, but that decision was largely based on the ease of fixing things to an OSB wall. It doesn't look that rough after a few coats of paint, especially not the area behind the benches, where I added a couple of coats of white gloss, just to make it easier to keep clean. I've also used relatively cheap plastic T&G boards to line a rubbish bathroom ceiling in our house, that had been (badly) artexed. These were 250mm wide, matt white, around 3m long IIRC and went together with near-invisible joins. The stuff isn't thick, around 6mm or so, so needs to go onto an existing panelled surface, but it is quick and easy to install and gives a nice, wipe clean, finish.

Just to put some numbers in to give a sense of perspective for our all-electric house, our annual grid import is currently estimated to be 4,305 kWh, for a 130m² house. Heating is only a fairly modest part of that, about 450 kWh. Hot water is around 680 kWh. Car charging I've estimated at around 550 kWh at the moment, but there is a fair bit of uncertainty around that figure. Our heating uses a lot less energy than @TerryE, both because of our particular local microclimate, where we are very sheltered and in a relatively warm spot., and because our ASHP seems to run with a high COP, over 3.5 most of the time. If we used direct electric heating then our heating energy usage would be around 3.5 times higher, but cooling would remain the same. Splitting out the estimated peak rate and off-peak rate elements of our total energy usage for the year, allowing for PV generated energy self-use, I currently get an off-peak usage of 2,236 kWh and a peak rate usage of 2,069 kWh, so a percentage split of about 52% off peak rate, 48% peak rate. In cost terms, switching from the tariff we're on now to a basic E7 tariff (which is what we'll have to do initially, as only some suppliers will change the meter, it seems) will save around £100 a year, but if we then change supplier I can get that saving to around £210 a year.

It's surprised me, TBH, as I've been doing some pretty simplistic estimates of the cost/benefit of battery systems for a couple of years or so now, and the return didn't quite match the investment. Two things have changed. One is that the price of battery storage systems keeps decreasing, the second is that I'm now in a position to better utilise E7, and that has an impact on the savings from a battery system just from being able to offset peak rate imports. That offset is significant when looking at our peak rate energy usage pattern, where all year around the peak rate peak is in the early evening, from cooking, watching TV etc. We have 6.25 kWp of installed capacity, facing 207 deg and inclined at 45 deg. We generate around 5,800 kWh per year, and to simplify the sums I just looked at winter (150 days assumed) and summer (215 days assumed). I may go back and refine this by month, but doubt that this simplification changes things by more than 10%, if that. Yes, the DHW takes priority for any excess PV generation, as we need DHW all year around, with a near-constant daily demand. The car charging can't easily utilise excess PV generation (although I am trying to do the best I can) because of the limitiations of the J1772 EVSE protocol. The latter sets the minimum charge current that can be utilised at 6 A, and most car chargers aren't able to respond "on the fly" to charge point capability changes. This means that although the available charge current can be changed from the charge point end, in practice it's necessary to shut the charge point off, then change the current that's available, then turn the charge point on again, so that the car can sense the new available current and adjust its on-board charger to not exceed that. This is a "feature" that units like the Zappi seem to gloss over, with there being an assumption that using such a system can result in all the car charge coming from excess PV generation, which is far from being the case. I still need to do some work on how best to manage car charging during the summer, when there is a lot of excess PV generation available, but it looks for now as if the simplest solution may be to just use a low charge rate that only turns on when export exceeds that rate for a short period of time. I believe that will fit with my pattern of use, anyway, as much of the time the car will only need around 2 or 3 kWh per day of charge, if that, to cover the sort of journeys I do most of the time. For longer trips it makes more sense to just charge the car up at the off peak rate, as I'd do in winter.