sgt_woulds

Just use some mud. It was used as mortar for thousands of years before cement was invented. Dig a hole and take the subsoil, mix with some sand, possibly add some fibres (wool?!) and experiment with the ratios until you get a pliable but firm mix. It will be resistant to sheep and less expensive to repair when the combine inevitably knocks it down again

Useful advice can also be found in the following links: Rethinking IWI with Natural Fibre Insulation Insulation and retrofit - Finding the sweet spot - The Alliance for Sustainable Building Products (asbp.org.uk) The-use-of-natural-insulation-materials-in-retrofit.pdf (stbauk.org)

Ah darnit, I've done this before as well! Copying and pasting from a standard e-mail response which says 'a high level of insulation' then changed it to U-value and forget to change it to say low U-value! It's an age thing sonny... 🙂

If your builder hasn't used woodfibre before (and it's great that he is open to trying) make sure he has the correct tools for cutting the boards as they are much denser than the materials he will be used to. Assuming a preference for power tools: For flexible woodfibre batts - a jig-saw or sabre-saw with fibre insulation blades (you can also use an insulation hand saw but this tends to rip the back of the insulation batt) For dense boards - a table saw or circular saw with a large blade and 'bastard teeth' (few teeth with large gaps between) and the best extraction they can get as woodfibre is very good at gumming up the works, in particular the safety guards. (You can get circular saw blades specifically for woodfibre, but these tend to be only available in Europe and for eyewatering prices) At home I have an ancient (1970's) open frame circular saw (no safety of any kind!) that works brilliantly, but only has a 50mm cut, so for deeper boards I have to turn them over and cut twice...

Just to pull up @Redbeard slightly, although I agree with his preference for woodfibre (I work for a woodfibre manufacturer so that's a given 🙂), this is a situation where a membrane may still be required. The best advice here is for you to have your external walls assessed via hygrothermal software - such as WUFI - which will take all of the site variables into account. Internal wall insulation is more complicated than external insulation due to the way it moves the dew point within the construction. Standard U-value calculations (Glaser) will not correctly account for the sorption properties of wood fibres nor their ability to pass on liquid water through capillary action. WUFI purely considers moisture issues and how the various elements of the building fabric will deal with the volumes based on site-specific conditions. More specifically, where you have an external finish that restricts 'breathability' you need to be really careful to reduce the amount of internal moisture that can get behind the insulation layer. Woodfibre will handle this better than Unnatural insulations, but it needs careful assessment. With woodfibre, it may be more appropriate to incorporate a framed system (with flexible insulation batts between) as this allows the addition of a moisture-vapour variable (VVCL) membrane such as STEICOmulti renova or SIGA Majrex® or PRO CLIMA intello plus . These membranes will limit the amount of water vapour that enters the fabric, but allow breathability back to the inside during warmer periods. Correct installation of the membrane and connections to all surrounding elements is the critical factor to get right with this approach, but it is less risky than it would be with unnatural insulations such as PIR. Woodfibre, actively transports moisture due to the sorbative fibres (I've seen studies that have shown the addition of woodfibre drawing moisture out of wet structures) whereas somthing like the Kingspan boards would trap it behind the insulation. It is nearly imposible to assure that any VCL (or taped PIR boards) are 100% perfect. That is without building trades or future homeowners unknowingly driving screws or causing other penetrations through the membranes after completion.. It is important to note that we do not generally recommend achieving high U-values with IWI due to the condensation risk to the structure. There is, generally, a sweet spot between 40-100mm of woodfibre that balances the energy savings, cost, and condensation risk. Part L of the Building Regulations for England offers flexibility when retrofitting existing walls, roofs and floors; an improved U-value of 0.30 W/(m2·K) is the target but a ‘threshold’ level of up to 0.70 W/(m2·K) is sufficient, as long as the approach can achieve a payback not exceeding 15 years and is ‘technically and functionally feasible’. It is worth discussing with your local authority / BCO; for an older building, most BCOs are now sympathetic to the argument that breathability is more important than the insulation value. Back to Earth offers WUFI, and I think Mike Wye & EWI pro / EWI store do too if you ask.

You could use something like this to control it: Single Axis LCD Solar Panel Tracking Sun Tracker Controller W/ Wind Speed Sensor | eBay UK

Fair enough 🙂 Our customer was an Econutter who was eeking out every last watt. Eventually, even he only adjusted his array twice a year. End of October and end of April from memory. In the first year he changed it daily; his panels faced slightly east of East of South, if he laid them back in the late afternoon he captured a few more rays before the sun set. Like I said, 'Econutter'. You can afford to play if you are retired I guess! These days an automated single axis tracker would be easy to set up, though

You could always look at a design that allows the array to tilt at different angels for summer / winter. We did this for a customer many years ago and it made quite a difference to his outputs - he kept daily records, and after 2 years had worked out the optimal time of year to adjust the angles which was a 30 minute job with spanners twice a year. I can't remeber the details of the frame we used but I can see it could work well with scaffold tubes as it would be easy to create a pivote around the poles.

Assuming 5x1 row then no! 5 x 1134 = 5.67m without considering the clamps (assuming approx 25mm width for each clamp that would add an additional 150mm) Best get 2 lengths at 6m. You need to make sure that you add enough support to the unistrut rails with the scaffold poles - a proposal sketch would be useful. If you have large overhangs with unsuported unistrut then use 41 x 41mm unistrut instead of 21 x 41 mm.

I like those scaffold/panel clamps - not seen them before but I've been out of the game a while. Bloody expensive though! Before MCS was introduced to extort money out of the system suppliers and legacy installers, we used unistrut for everything. My vote would be for galvanised unistrut as it will last longer than mankind. Having said that, if you don't mind a bit of surface rust after a few years then BZP will be fine. We used to get ours from CEF (2 x 21 x 41 mm). I'd use aluminium T-clamps and mount them to the strut with with short-sprung unistrut channel nuts. (the springs are a luxury but it makes locating the bolts easier). Be aware of the clamping zones for your panels - clamping outside the zones can induce stress and create microfractures in the cells. In extreme cases it can cause 'rapid, unplanned dissassembly' in strong winds...

At least if they use robots with set programs there would be less of the Great British Builders attitude of 'good enough for a Friday / Match day / customer who doesn't know better'...

Unfortunately, FACIT has just closed it's doors as there were not enough self builders who wanted to use their system and the mass housebuilders wouldn't even consider it.

Unistrut. Mechano for big boys... 🙂 Scaffold poles are harder to cut, not as easy to fit together, and you will still need a way of mounting the panels. However, if the tubes and labour are free...

Talking of screwpiles reminds of another GSHP project in London; They were using a machine to fit a vertical deep-bore heat pipe. TFL arrived and asked them to stop - less than politely but for very obvious reasons -when it was pointed out that their back garden was directly above part of the Norhern line...

I've not been able to check your calculator yet Steamy - no computer at home at the moment. Could it include occupancy levels and biogenic heat sources? I read this recently: The small passive house problem - a solution? - passivehouseplus.ie To my mind, most PH builds have been massivly oversized because it works better on paper. It would be nice to have a tool that advocates for sufficiency.

I guess my thinking was, if you have a digger in anyway, just dig a few trenches for GSHP as well. All points taken on board, and I do think GSHP has had its day. I vaguely remember reading in (I think) Green Building Magazine (great magazine sorely missed now that the deathly boring PH+ has replaced it) that someone had built a heat store under the foundations, using a tarmac drive with pipes to heat it up. Maybe it was a school - it was a looong time ago. Back then we had a lot more people willling to experiment. Back when I was installing solar (when the average system was £25000 for 1.5kw), we worked with a some fantastic experimenters and early adopters. One chap - who lived in a Walter Segal designed, and self built house - dug out his entire back garden to shoulder depth using nothing but a shovel and wheel barrow to bury his GS pipes. He was powered by Rum and Wacky Backy and was older than I am now when he started! The soil was removed by barrow to skips at the end of the lane, stored offsite, and then returned for the reverse process. Unbelivably he finished it all in a couple of months. Then he realised there was a leak and had to repeat the process...

In the colder regions of America they sometimes extend insulation out from the foundations, or create a skirt of insulation deeper than the foundations. I think this is for frost heave, but it should also make the temeperature under the slab more stable. Could GSHP pipes be layed under the raft at the same time to take advantage of this, or would removing heat under the slab cause other issues?

Talking of sums, this is a bit out of date now (I saved this about 5 years ago), but posted for further discussion: This does not include running costs. Perhaps someone here can update the MVHR / MEV costs based on real life experience. I've costed iPSV componants at around £800 for my small 3 bed, two storey house. at current prices

These only list temperatures at 1m depth, which is barely below the subsoil in most regions. We are on solid chalk and our topsoil depth is only about 300mm max. At depths of 1.5 to 2m the rock should be at stable temperature. In Hungary i've visited peasant wine cellars built into slopes where the depth above the vaulting is less than two metres and the resulting drop in air temperature is very noticable even in sustained heatwaves. Soil pipe / Earth tunnel. Same thing - just don't confuse it with the other type of soil pipe 🙂 Cooling only. I gather it is quite popular in French public buildings and schools & used by enviro-mentalists (like me 🙂 ) in California . Measures need to be taken to ensure that rain/rodents etc cannot get in. I suspect that clay pipes would work better than plastic to for energy transfer. It's not about energy gain, this is about drawing in cooled air for sustained high temperature situations where subsoil and rock maintain a lower temperature. Even a 2 degree drop from ambient air temperature can be a significant health benefit in a sustained heatwave. Could we see your sums on this? Are you talking about a planned and 'intelligent' passive stack in a well sealed or even 'passive' house or retrofit to leaky fabric? If it is the latter, then none of the ventilation options are perfect...

One of the drawbacks I can see with iPSV is hot days and sustained heatwaves with little wind to drive ventilation. Currently we 'sail' or house through heatwaves by closing off all ventilation and shading the south facing windows (curtains, but we are planning external shades when we replace the front windows). Our roof and walls contain lots of woodfibre so we have good decrement delay, and occupation is low during the day so CO2 and moisture levels are not an issue. In the evening after the sun has set and the air temperature has dropped, we open the north facing windows and the skylight and purge ventilate the house - you can feel the cooler airflow and it is very refreshing. However, after a couple of days of heat, the night time temperature difference is reduced (due to radient heat from the earth and buildings) so this option tails off and CO2 levels inevitably rise. We then use portable fans to make life bearable. I know they considered this issue with the Bedzed buildings and tried using ventilation cowls / wind catchers but I don't think it was very successful. It is pretty much a given that climate change will lead to more frequent and longer heatwaves so I'm considering building a solar chimney with soil pipe ventilation - I have to build a patio out the back anyway so it is just a little extra excavation. The chimney might be an issue with building control, but sod 'em! We'll stick it up and see if anone notices! I have a couple of ideas on the design, and I'm considering buying the Handbook of Domestic Ventilation but I don't know if this is a good sourceof information or if there is better text elsewhere. It is an expensive book to take a punt on...

With iPSV you don't need a fan in the bathroom or kitchen, to maintain overall conditions. You might want a small fan to assist with kitchen odours though. We do have an extract fan in our kitchen, as an easy route for passive stack was not available. Building from scratch, these problems could all be mitgated at the design stage.

Restricting moisture sorbing and release to the surface materials (Gypsum plaster boards) limits the positive benefits of stable indoor moisture levels that natural insulations can provide. Not an issue with MVHR of course (unless there is a sustained power cut in winter with high occupancy) as this is artificially removed. Personally, I'd rather not rely on a mechanical system to stay healthy indoors. Horses for courses. And I prefer my straw hat to tin foil 🙂

I remember working in a factory conversion many years ago. They wanted the high vaulted ceiling look, but realised that in winter all the heated air would be above their head. They had a wierd looking single bladed fan to force warm air back down to occupent level...

Interesting comments on Gypsum plaster. For our woodfibre IWI, lime plasters are always specified because it is more breathable than Gypsum in the same situation. The sorbative properties of woodfibres (and natural fibres in general), can release moisture quicker with direct lime plasters than than gypsum. Some testing in Germany has shown woodfibre insulation to activily transport moisture from damp structures to the surface, so breathablity is critical. We have an alternative system using battens and boards with plasterboards and flexible woodfibre behind a moisture vapour variable membrane. (M-V VL membrane restricts moisture entering the insulation, but still allows it to breath out effectively when contditions allow. (After the Gypsum has (slowly) released its moisture) This works technically, but holistically it reduces the moisture buffering and moisture exchange rates and is not the best use of natural products. (Essentially, building moisture buffering is almost wholly down the the plasterboard and skim).

Thats the point. I'm concentrating on airtightness, then introducing a controlled volume of fresh air, based on internal moisture levels. As long as internal moisture levels are low, the vents remain closed so over-ventilation shouldn't be an issue. Empirically, I have noticed CO2 levels rising pretty much in line with moisture levels and occupancy so I'm not concerned about passing out from hypercapnia using moisture as the controlling method. It would be nice to have some heat recovery and filtration, but since Ventive pulled their product from the domestic market this doesn't seeem to be commercially available.