Stones

The main challenge on the outer isles is getting a contractor, as they are generally busy so are in a position to pick and choose, and new builds certainly preferred to large scale. Two contractors work with ICF here. In addition as has been indicated, additional costs in terms of getting materials to the Isles, and worker accommodation costs, albeit these are offset to an extent by lower plot prices. Getting material delivered can be challenging. As @ProDave mentioned, my choice of treatment plant was ultimately decided on the grounds of delivery. You will probably find that you have to organise onward shipping from Aberdeen for many things - easy enough to arrange as there are various firms who do it, it's just another cost. Planning wise, its a very relaxed regime for the outer isles. @westbound are you already living in Orkney?

Sadly, nothing to offer other than a regular clean and treat the moulded area with bleach. I find that when I remove the heat exchange core, and angle it over, a fair amount of condensate drains out, but generally this remains free of mould. The plastic louvre grill tends to have mould grow on it, as do the extract fan blades, so I clean the lot, and make sure the drainage hole and pipe run off is clear and free flowing. Having measured the temperature of supply air into the house, my unit seems to operate at 90% heat recovery. Added to that the higher relative humidity and moisture levels, it's perhaps not surprising there is so much condensation - but at least shows the unit is working.

At each end of the louvre assembly, the 3 slats you can see closed. The bypass forms when the solenoid closes the main louvres, and opens the 3 slats at each end. This prevents air cycling through the heat exchanger by guiding the airflow (with the aide of foam on each end of the heat exchange core) around the heat exchange core.

Have to agree with this - I wonder if condensate has formed in the heat exchanger as it's pulling air from outside inside - if the extract air was cooler than the incoming air, and the incoming warm air was moisture laden, it would potentially condense on the intake side of the exchanger fins, then run down through the fins and collect where it has.

Same here, on the extract side, condensate drain blocked with biosnot, water built up until the fan started churning it. I

Following on from this original topic, I have today just completed the annual main clean and service of my MVHR unit, now 8 years old. With our unit now located within the heated envelope of the house (rather than our cold loft as it was originally), the blocked condensate drain issue has not arisen again. There is always some evidence of mould growth on the extractor fan blades and extract fan chamber, but given this is a cold and damp / wet part of the unit, that is hardly surprising. I did however uncover 2 new issues: 1. The summer bypass, which consists of a plastic louvered fin assembly in a rectangular frame, opened and closed by a solenoid, was stuck in the closed position, i.e. on summer bypass. Closer inspection revealed the end of the solenoid which allows the unit to switch from heat recovery to summer bypass had broken off. On attempting to operate the louvres by hand, they were stuck solid. The screws securing the louvre assembly to the frame had corroded to such an extent that they prevented movement, which in turn caused the solenoid to break. The screws were so far gone that they dissolved on contact with a screwdriver. With the gentle persuasion of a mallet, I was able to tap open the louvre assembly to the heat recovery position. This means that I now have no summer bypass as there is no means to close the louvres. Not an urgent problem given the time of year, but something I will have to think about getting a replacement part for. Top tip therefore, lubricate the screws to try and slow / prevent corrosion. 2. Eight years of removing and re-inserting the core has torn / destroyed one of the seals (pictured hanging). Fortunately, I had some neoprene adhesive backed tape which I used to replace. Other than that, (and a previous fan bearing replacement) the unit is still going strong.

Indeed. Storage is of course measured in kWh.

Sort of. I think this is the real plan: https://www.telegraph.co.uk/business/2024/07/11/chinese-electric-cars-to-power-your-home-in-octopus-deal/#:~:text=A Chinese electric car maker,parked in their driveway... You can just imagine how the conversation went - Minister, if we prohibit the sale of ICE and force everyone to buy electric cars and we tell people to plug them in to get a 'discount' on their electricity bills, that gives us 33 million x 60 kWh of storage, which is nearly 2000 GWh of storage, which gives us 40 days of energy security even if we generate nothing for a few days. And the best part is, it won't cost us a thing, the public will pay without even realising. Even better we'll finally be able to introduce road pricing and increase revenue from that. Minister, this will transform our country, and you'll go down in history with a legacy few will ever surpass. Whilst there are obvious flaws to such a plan, you could see how a politician would get on board with such a vision. Nothing wrong of course with the idea of using your car as a power bank. Whether its better for the grid vs distributed storage at local / household level is a different question.

I'd also suggest comfort comes into this, and what type of heat you want. How an A2A delivers vs an A2W via UFH. I personally dislike warm air being blown around by an A2A, but when on holiday, appreciate the cool breeze of aircon. Heat delivered via UFH from our A2W gives a nice steady even temperature in house (with the added benefit A2W provides my DHW needs as well). But the cooling is less effective as it takes longer (albeit very pleasant when up (down?) to temperature. I think A2A are fantastic in large rooms / open spaces, less so in small(er) rooms. Like everything else, there are trade offs, and individual lifestyle requirements, and house location / design all play a part.

If memory serves, the original Passivhaus heating standard was designed so that all of the additional heat requirement could be delivered via a ventilation system (resistive heater). I know someone here who designed specifically to Passivhaus accreditation level, but still requires additional heat on certain days. Average solar gain for example is all very well, but rarely do you get the gain evenly spread. When I was looking at it for our house (2016), I looked at a range of options and heat requirement levels. The conclusion was that for both heat and DHW requirement, if the requirement was below 2500kWh annually for each, you would over a 10 year time frame be better off using straight forward (and inexpensive) resistive heaters. Above that level of requirement, the figures stacked ever more favourably in the direction of a heat pump. Energy prices have of course significantly changed since, so the cut of kWh requirement point will have changed.

@Steve W Appreciate this relates to fans in a Vent Axia, bit hopefully give you the push to try bearing replacement.

Would you mind sharing how much the course cost you, and any registration fees you need to pay?

Although I imagine the challenge given the postage stamp sized gardens is where would the ground pipes go. As you rightly point out a borehole would solve this, but how many GSHPS can a borehole support - presumably as you also say, local geology dependant

We went out of interest to have a look at a new development outside Inverness (Tormagrain). No heat pumps, all gas. When I questioned this, they said they had been refused permission for heat pumps, on the grounds of noise - apparently the combined effect in the house layout pattern would be over 100db. The only way they could have a heat pump based system was to install a communal one (think large supermarket or warehouse size provision) and locate it away from the houses. High overhead cost, (albeit not insurmountable) to manage that - invoicing etc, and lack of support to maintain and service such units/systems apparently.

Thanks all.

Do you happen to have anything in writing from the course confirming that?

Interested to hear what users have been required / requested to submit in the way of plans / details for accessibility ramps beyond providing a written specification (including ramp geometry) and marking on site plan. Has anyone been required to submit additional drawings / sections / calculations?

I've got an acquaintance installing one of the following small hot water heaters in a portacabin style building: ATC-Pacific-Unvented-Water-Heaters.pdf The installation info shows the discharge point post tundish as 'to drain'. The project in question requires a building warrant due to the length of time the building will be in place, and therefore needs to comply with the relevant section of the most up to date (Scottish) building regulations: 4.9.4 Discharge pipe termination: The pipe termination should be in a visible location and installed so that discharge will not endanger anyone inside or outside the building. Ideally, the final discharge point should be above the water seal to an external gully and below a fixed grating. Other methods for terminating the final discharge point would include: a. up to 100 mm above external surfaces such as car parks, grassed areas, or hard standings; a wire cage or similar guard should be provided to both prevent contact with discharge and protect the outlet from damage, whilst maintaining visibility b. at high level into a hopper and downpipe of a material, such as cast iron, appropriate for a hot water discharge with the end of the discharge pipe clearly visible c. onto a flat roof or pitched roof clad in a material capable of withstanding high temperature discharges of water, such as slate/clay/concrete tiles or metal sheet, with the discharge point a minimum of 3m from any plastic guttering system that would collect such discharges. Discharge at high level may be possible if the discharge outlet is terminated in such a way as to direct the flow of water against the external face of a wall. However evidence of the minimum height of the outlet above any surface to which people have access and the distance needed to reduce the discharge to a non-scalding level should be established by test or otherwise I recall from previous discussions that some users had been able to terminate the discharge to a drain inside their houses rather than externally. I'd be grateful if someone could advise what they did / if BC accepted?

There was something on the local radio last week about this. In short, the way the payment has been set up (for speed of payment rather than accuracy) they are using simplified data to determine areas that are not connected to the gas grid, and therefore alternatively fuelled.

To clarify, there is no intention to charge the domestic properties for any excess diverted from the commercial array. Clearly there would have to be legal agreement on who was responsible for the battery and tech that would enable this. In this case it would be the community company that runs the commercial business, as they would also be the landlord of the rented houses. Absolutely take the point if trying to sell to households for the reasons you have listed.

I'm involved with a local project that will be a mix of community commercial premises and housing for rent. One of the things we are thinking about is a semi combined / community PV and battery storage system - fitting as much PV as we can to the commercial buildings, and cascading surplus generation first to battery storage for the commercial buildings, then when they are charged, to batteries in the rental houses. The rental houses would have their own PV fitted, which would divert excess generation into a household battery and potentially a DHW cylinder. Each property, be it the commercial buildings, or the domestic properties would need to remain islands for billing purposes. Is this possible? - I can't see why not Would the domestic properties need two batteries - one for excess feed from the commercial building, and one fed from their own array? Has anyone experience of setting up or been involved in anything like this?

Is it just that window, or every window that you have condensation inside (when outside temp is as per you describe)?

@Barryscotland A friend has something similar to the set up you're describing. TV seems unnaturally high on the wall to me but that's something you can perhaps get used to. What they do have is a 150mm deep timber mantel over the stove position with a steel heat shield fixed to the underside.

Just checked mine, over the last two weeks the ASHP has used 105 kWh on heating (155sqm internal footprint, 50% full vaulted ceilings with an additional 15sqm attic type room - footprint is laid out as two interlinked cottages, so a lot of exposed exterior wall). This has delivered 387 kWh of heat to the house (so a CoP of 3.6). I have the master thermostat set to 19C - we are trying a lower set point this year to see what the energy saving is compared to previous set point of 21C. So far, so comfortable and the house sits around 19.5 - 20C. It can get higher, but that depends on the sun appearing. Ambient temp wise, not as cold here as elsewhere, but higher wind speeds, which ultimately have much the same effect in determining our heating requirement.