Jeremy Harris

I just used a document published by BRE (what used to be the Building Research Establishment), so it wasn't referring to a specific concrete company. The cement data came from the widely used figures that a tonne of cement produces between 750kg and 950kg of CO2. I'm not sure how that tallies with the data in that Wiki article though, as it doesn't seem to match very well. The mix ratios of concrete are volumetric, plus there is a fair mass of water added, much of which ends up being incorporated into the cured concrete. I used SGs of 3.11 for cement and 2.65 for the fine stuff and aggregate, and 1 for the water content, then just used the volumetric ratios of each to try and estimate the amount of CO2 from the cement manufacture that ended up in the final mix.

I made a cockup, @Ed Davies! I used a document published by the Readmix concrete people to get the CO2 produced from making concrete, and then spotted later that it was seriously optimistic, as it didn't include the CO2 emissions from manufacturing the cement - not sure how on earth they thought that made sense. Your Wiki link looks as if it might be more accurate, as I worked back from the mass of cement in the mix using the densities and volume mix ratios), tried to guesstimate the mass of water in the mix (that ends up becoming part of the set concrete) and ended up with what I thought was about the right CO2 produced (which it seems it wasn't). PS: when I edit stuff it doesn't show as being edited unless I remember to select the "show this message has been edited" box.

Richard was my chairman in my last job. Good bloke, IMHO, he wrote me a nice letter thanking me when the last programme I'd managed came to an end.

The problem government (any government, not just this one) faces with housing regulation is that the big developers are exceptionally good at lobbying against any proposed legislation that might increase their costs. They've been successful in watering-down proposed changes to the building regulations, that could have made our regulations as good, from an energy efficient view, as those in Ireland. They've succeeded in having legislation like the Code for Sustainable Homes withdrawn, via pressure applied to the technical standards review. They get away with building houses that fail to comply with the regulations because they apply a great deal of pressure to prevent any tightening of inspection regimes. To be fair, this doesn't just apply to housebuilding, and I doubt that the big building companies are any worse than any other major employer when it comes to lobbying government to get what they want. The key problem seems to be that the general public have an illusion that they control who gets elected, and hence what policies become regulation or law, when in reality democracy doesn't exist as far as law and regulations are concerned. This shocked me when I took up my first major procurement role. I arrived in my new office and was told I couldn't do anything until the letter from my minister arrived, giving me his delegated authority. By mid-morning the blue envelope arrived, instructing me that I had delegated authority to spend £1.55bn to deliver a new fleet of helicopters, and that I was charged with ensuring best value for the taxpayer when doing this. That week I set up a team to manage the fine tuning of a request for quotations, detailing the operational requirements that must be met, with the intention of getting several helicopter manufacturers in Europe to bid competitively to provide a solution that met the operational requirements. A week or two later, long before we had finished drafting those operational requirements, my minister had a private meeting with the MD of a British helicopter manufacturer, and a few hours later (without telling me) he announced to the press that the contract was not going to competition, but was being awarded to the said British (bit arguable that, given they were Italian owned) company. I only found this out when I heard the news that evening; he didn't even have the common decency to tell me. Needless to say I got bloody angry and when I met him in London a day or so later we had a "frank exchange of views". There was no way I could get best value for the taxpayer, as the contract had been effectively awarded before we'd even written the specification or defined the requirement. I later found out that the reason for awarding the contract in this improper way was because the company threatened to lay off a couple of thousand people, and the minister thought that it was better to pay them off. It made my job damned near impossible, as the MD was quick to remind me, whenever he was pushed, that he could be at Westminster within a couple of hours (using the company helo) and that he had the power to get my minister to bring me into line.

I don't blame you for feeling exasperated, as it sounds like a complete PITA. I'm wondering if the pump may have always been operating close to the point where it could stall, and so just a small increase in back pressure, perhaps from a slight reduction in the permeability of the soil surrounding the soakaway field drains, has been enough to be the "straw that breaks the camel's back". Opening the pipe close to the end, where it joins the field drain pipes, would give an indication as to whether it's increased back pressure causing the problem. My guess is that if you do this you will find that the pump is fine pumping up the whole length of the pipe, with a good flow rate.

This really is a bit of a puzzle, isn't it? It's hard to see what could be causing this, as it seems that a blocked pipe has been ruled out. Fitting a pressure gauge in a tee in the pump outlet pipe would show whether the pump is delivering the specified head. Ours sounds similar to yours, a stainless steel submersible one, and that has a 7.5m maximum head, so around 0.735 bar. Fitting a 1 bar pressure guage should give an idea as to whether the pump is working properly, although your small drilled hole in the pipe should be almost as good an indicator. From what I can recall about the pressure curves for centrifugal pumps, they can hydrodynamically stall, so that if the back pressure momentarily exceeds the maximum the pump can deliver, the pressure falls off again, rather than following the rpm being proportional to pressure line as rpm increases.

You've highlighted a major issue, @Big Jimbo, the attitude of the planners! When I started to write the Design and Access Statement for our planning application I mistakenly thought that "sustainability" meant what I'd guess most here think it means. Sadly, in planning terms, it doesn't. Sustainability as far as planners are concerned relates to whether the community and facilities around a proposed development are sustainable, in terms of having things like transport links, services infrastructure, road and path capacity, access to schools, hospitals etc. There's now nothing within the planning framework anywhere (as far as dwellings are concerned) to give any preference for energy efficient homes, or those that have a low embodied energy/CO2 content. In the words of my planning officer "That's nothing to do with planning, we leave all that stuff to Building Control".

It's worth looking in a bit of detail at just how great the emissions are from some of the building materials used. Readymix concrete tends to be around 0.8kg CO2 per tonne, so taking our concrete slab as an example, that uses around 25 tonnes of concrete, plus around another 120 tonnes in our retaining wall (!), plus another 10 tonnes for the garage slab, so a total of around 155 tonnes of concrete. That makes the CO2 emissions from manufacture around 124kg, which seems way too low. However, it seems that the CO2 figure often quoted for readymix concrete fails to include the CO2 produced when the cement used to mix it is included (bit of a major flaw there). Cement seems to produce a LOT more CO2 to manufacture, around 780kg/tonne. Readymix will have around 60kg to 80kg of CO2/tonne from the cement, so in reality the CO2/tonne for the finished mix will be dominated by the cement figure, and for all the concrete in our build (which is a lot more than average, because of the big retaining wall) it looks like the CO2 figure is around 11 tonnes. The EPC for the house gives an annual CO2 emission figure of -0.9 tonnes of CO2 per year. That means (very crudely) that the house balances out the CO2 from the concrete around 12 years after completion, and from then on it's CO2 negative for the remainder of its life. I could use the BREEAM Technical Standards to calculate the "pay back" time for the whole house, but it will be dominated by the concrete, I suspect, given that the rest of the house is either timber, or timber-derived (like the many tonnes of recycled newspaper insulation).

For commercial developments there has long been a requirement (for those seeking reasonably good assessments) to offset the embodied CO2 in some way. Buying carbon offsets is the way cheats do it (IMHO), but some choose to take a more direct path to offset the carbon in the build. For example, the last programme I managed before I retired included building a big (900 people) laboratory and office building. This was largely constructed from reinforced concrete, although it used carbon fibre reinforced concrete - foam - concrete precast cladding. To offset the concrete we chose to plant a few tens of thousands of trees on the adjacent land. As a consequence of that, plus the energy saving measures (good insulation, airtightness and MVHR) that building achieved a BREEAM Excellent rating (the first public sector building in the UK to do so, I believe)

Possibly, it depends on what suitable dyes are available. I've used fluorescein and OBAs (the latter is more sensitive) and the advantage of either of these is that a very tiny amount goes a long way, as they are both detectable when very highly diluted by rain. The idea is to let the rain wash the dye down into the dry part, rather than saturate the roof with enough diluted dye so as to get it to penetrate. Fluorescein has the advantage of being reasonably easy to see, although it's far better to use a UV lamp to trace it. OBAs can only be detected with UV, they aren't visible to the naked eye, but they are detectable at very low concentrations.

I think a very careful dye test, doing one small area outside at a time, is perhaps the easiest way to find out where the water is getting in. This needs to be done very carefully because you don't get a second chance, once dye has found its way to the area around the window opening you won't be able to prove any other leak points.

There are lots of options around, this place has a reasonable selection: https://smartgreenshop.co.uk/index.php/energy-monitors/home-energy-monitors.html Some energy suppliers used to give these away at one time, so you may be able to find one that way (pity, I threw one of these free ones out when we moved house recently). If you wish to monitor individual appliances, then a plug-in monitor might be more useful. I have a couple of these: https://www.screwfix.com/p/energenie-ener007-energy-saving-power-meter-socket/3477h that seem to work pretty well.

I'm afraid you'll need a great deal more than 10mm of insulation underneath UFH if you don't want to waste most of the heat downwards. The bare minimum is around 100mm of something like PIR, preferably more (we have 300mm of EPS under our UFH heated floor). As a quick and dirty estimate, if your summerhouse has a floor area of 20m² (just a guess) and it needed about 1000 W of heat (another complete guess) into it to keep it at a comfortable temperature, then with just 10mm of underfloor insulation around 600 W to 700 W would be wasted heating the ground underneath (this rough estimate ignores the thermal resistance of the flooring itself). Ideally you want to aim to reduce the heat loss downwards so that it's no more than about 10% of the total, i.e. you draw (and pay for) 1100 W from the mains supply and the heating delivers around 1000 W into the summerhouse (just guestimate numbers).

Our ASHP is too big just because very small ones were near-impossible to obtain when I was looking. There are now 4 kW ones around, and one that size would have been a better match, although the 7 kW we have seems to be fine just run at a much lower output. Having the Sunamp doesn't affect the size of the ASHP, as the Sunamp is only used for direct electrically-heated hot water. ASHPs can be used for hot water OK, but I chose not to, mainly because the predicted COP when running at the temperature needed to charge a thermal store was pretty poor. A thermal store was our original set up as I didn't want to have to employ a heating engineer to install, and sign off against Part G3, an unvented cylinder. The Sunamp is just a compact thermal store and again wouldn't be well-suited to be charged using hot water from an ASHP, as the charge temperature would have to be over 60°C, which is a bit high for an ASHP to deliver.

All I did was load a large saloon car into the drawing CAD package and then sweep it around to see if it would fit in the space we had available. As it did, with room to spare, I added a bit extra to make turning easier.

I ended up ringing around a couple of places that hire fencing for events. One near me was selling used panel sets (panel, two clamps, one foot) for £15 each. These hire places seem to replace their hire stock fairly regularly, so might be worth asking around.

By way of contrast (and this probably reflects on the house thermal performance of our house as much as anything else), if I had opted to try to claim RHI then it would have added well over £2,000 to our ASHP installed cost (all the quotes I had for an MCS approved installation carried that sort of premium) and the payment we would have received would have been about £84 a year for 7 years, so under £600. For us it made no sense at all to spend over £2,000 extra to install the same heat pump in order to be able to get back less than £600 from the RHI.

My experience is that cooling is a significantly greater power demand in hot weather than heating ever is in cold weather, especially with a lot of glazing. Our highest solar gain comes from the East through to the South East in the morning; by midday in summer it generally isn't a problem.

I've purchased from appliances direct in the past with no problems. The self-install air-to-air heat pumps look to be easy enough to fit, and quite neat. For the modest heating demand for your extension I can't see why one of these units shouldn't work well. The only thing I'd perhaps want to look at closely would be the maximum cooling capacity and the noise level. The latter can vary a lot from one model to another. One office I worked in ended up replacing the air con units because of the noise, and the replacements were virtually silent.

You can DIY any practical domestic scale installation, but if planning to export more than 16 A per phase to the grid then you need approval from the DNO, who will set an export limit. In our case I wasn't sure what size array would be allowed, so just asked the DNO for the maximum they would allow and they set the limit at 12 kWp. Our system is only 6.25 kWp, so I can increase the size at any time, up to the 12 kWp limit. In terms of hardware, then there's no real difference, as the price pretty much scales with the power generation capacity. As far as installing the system goes, then it's the same for either a < 16 A per phase as it is for a >16 A per phase system. In England and Wales that means that the electrical installation and testing must be undertaken by a Part P accredited competent person and the installation certificate must be lodged on the database by them. If you don't intend to claim any payments, and are under the 16 A per phase limit, then the only other thing to do is notify the DNO after completing the installation. If the system is over 16 A per phase then that notification would have been done before you do the install, as part of the process of getting DNO consent. In Scotland (not sure about NI) then any competent person can do the electrical installation and testing, and the EIC only needs to be given to the house folder, it doesn't have to be notified to building control or put on a database.

That's correct, the crappier the house the more money the government pay you. You really couldn't make this up. Mind you, our system's not as crazy as the NI one. Their version paid people to heat open barns...

My car has now charged up from excess PV generation twice in the past couple of weeks. I suspect that over the course of a year more than 50% of my car energy requirement will be at no cost. It definitely increases the "smug factor" when you're driving around for zero fuel cost.

Stick the cable inside a drive-over heavy duty cable protector, like the ones used by location film crews, and make sure the cable is adequately protected at the TBS end, in case it gets damaged. Alternatively you could stick a couple of poles up and sling it overhead, but there's always the risk that something like a digger jib might snag it. If you think the cable's going to be there a fair time then it might be better to just bury a duct across the access, ideally in a location where you might need to get cables through in future, so it can be reused. My preference would be to bury the cable in a duct, if you've already got a digger on site. If not, then sticking it inside a heavy duty cable protector would be the next best thing.

A friend of mine, who was a keen walker, used to reckon you could assess the surface wind speed from the height at which the midges were flying AGL.

Our whole house is entirely heated and cooled by an air source heat pump. It uses a bit less than 1/3rd of the amount of energy that it delivers, as it just pumps heat from the outside air into the water we use to run the UFH and pre-heat our hot water. It works fine down to about -20°C, and that restriction is only because of the type of refrigerant used, as there is still loads of heat in air at -20°C (air at 0°C contains about 3.7% less heat than air at 10°C, air at -10°C contains about 7.3% less heat than air at 10°C).