Lilly_Pines

All the information I've seen suggests it holds a vacuum much better than regular double/triple glazing holds its gas in, with warranties of 15 years being routine. Combine that with the better aesthetics of slim panes and minimal to no double reflection, better sound insulation, and better thermal performance than reasonable multiple glazing options, it seems like a no-brainer if you can afford the initial outlay.

I don't have a plot yet so ground conditions are entirely hypothetical. Looking at heating only is probably not a good way to analyse this as the main benefit is intended to be for cooling, and the heating (of ventilation air and DHW) is mainly to balance out the incoming heat from summer cooling. If the balance works out right and the ground has enough storage capacity for year-round use there would be absolutely no reliance on energy flows with the surrounding ground, as the heat that goes in in summer comes out in winter (if anything, my intuition suggests that the ground is more likely to get too hot than too cold if used like this). MVHR is already pretty much non-negotiable because I want serious amounts of fresh air even in the winter, and I don't think solar & internal heat gains are anywhere near sufficient to compensate. As far as outlay is concerned, in the ideal case a number of shallower boreholes that could be drilled DIY with cheap equipment would suffice. If it can be combined with pile foundations (which seems highly compatible with a post&beam frame) the outlay would not only funge against ASHP cooling but also conventional foundations. If geothermal pile foundations permit building the house closer to mature trees etc. without harming either the house or the trees the aesthetic value of that also counts. Better construction and insulation may be easier said than done. I'm planning on overshooting the permitted glazing areas of Approved Document O by a factor of 2 or so, and east/west-facing windows are hard to shade with anything other than mature deciduous trees. A back-of-the-envelope calculation for a 100m2 house with 40m2 of windows at G=0.5 suggests I'd be getting 40kWh (minus shading) of solar gains per day in June, while heat gains through the walls and roof would only be around 10kWh per day at a constant outdoor temperature of 30c with U=0.2. Conductive heat through windows at U=0.6 for the entire window would be 6kWh per those same 24 hours. The windows are already calculated as about as good as they get, and improving the walls and roof from 0.2 to 0.1 would only reduce the total heat gains from 56kWh/day to 51kWh/day at zero shading and 36kWh/day to 31kWh/day at 50% shading. The real numbers would be even worse because solar gain during heatwaves is greater than the monthly average which contains cloudy and rainy days. If incoming ventilation air is cooled from 30c to 15c, while the indoor temperature is 20c, 600m3/h is sufficient to produce around 20-25kWh of effective cooling per day; doubling the ventilation rate seems like it would be approximately sufficient. This cooling could be achieved by simply rigging a balanced pair of fans to bypass the MVHR and spread the cool air using the same ducts. Pressure losses in the ducts would be greater than when the MVHR is used but bypassing the core helps, and the ducts would obviously be sized to accommodate the need. If I can convince building control that this is still a flavour of mechanical ventilation (which counts as a passive method) instead of air-conditioning (which is to be avoided where possible) passing Approved Document O should be a non-issue. If building control considers the pre-conditioning to be "active", being able to show ridiculous CoP numbers should still be helpful in getting away with the natural lighting I want. Those numbers look a bit worrying, and I'm not fully sure if they're representative considering what I'm seeing elsewhere (e.g. "20m of borehole for 1kW of power" for GSHPs, which a 2W/mK would indicate a 25K temperature difference or a -15c working fluid), but ground conditions vary and could probably easily explain this. In a real application I'd obviously be doing a proper survey or at least an empirical experiment before making a system load-bearing.

If the incoming air starts at 10c instead of 0c it arrives at 19c instead of 18c. Not a huge difference until you crank up the ventilation rate to silly levels because you like fresh air even in winter, and enthalpy cores that exchange moisture as well as heat have lower efficiency to begin with.

The mean annual ground temperature in the UK is around 9-11c and once you reach 10m depth there is very little change throughout the year. At 600 m3/h getting air from 0c to 8c is roughly 1.6kW. The heat transfer coefficients for air-to-water are listed as 600-750 W/m2K, or 4,800-6,000 W/m2 at a 8c temperature difference, thus indicating that a heat exchanger of roughly 0.3 m2 would be required, which seems perfectly viable. I found an earlier discussion, with some numbers giving a CoP estimate of about 40. Looking at the product in question, the heat exchanger seems excessively small resulting in unnecessary resistance to airflow and I'm also questioning if the brine pumping could be more efficient. However, even a CoP of 40 is massively higher than can be achieved with an ASHP which means a lot more bang for the buck, and a lot more nonsense in the building (can I cool a greenhouse with this? numbers say yes) before building control crucifies me. The possibility of using the ground as the only source of cooling also opens up the prospect of avoiding the hardware of an ASHP/whatever for space cooling and just plugging a DHW GSHP into the same boreholes. A GSHP also seems easier to soundproof than the outdoor unit of an ASHP buzzing somewhere on the property. The reason this isn't done more often is that it requires the groundworks of a GSHP which makes it prohibitively expensive compared to the gain in most cases, but if you're a weirdo wanting to do silly stuff and willing to DIY the hardware it starts to seem a lot more attractive to me.

Yes, the idea is to get 0c air to 10c and 25c air to 15c before it goes to the MVHR (in winter) or bypasses it (in summer). With a 87% efficient MVHR and 20c indoor temperature the incoming air would be 18.7c instead of 17.4c in winter, cutting ventilation heat losses in half. Which is kind of a big deal if you're going for multiple air changes an hour. In summer the incoming air would be below the desired indoor temperature, helping compensate for heat gains and high air temperatures without using compressor-based (significantly less efficient) air conditioning. The raw borehole fluid would not be suitable for UFH as it would be cooling the house down, not heating it up. Using a GSHP would be possible, but running the compressor on the refrigerant consumes electricity and limits the achievable CoP, so I'd prefer to use it only for purposes that really need the temperature differential (DHW and backup heating when heat gains and intake air preconditioning aren't enough).

I'm looking to use ground source non-heatpump heating/cooling to pre-condition ventilation air before the MVHR, but I'm having a hard time finding data to base performance calculations on. The idea is to have one or more boreholes (e.g. geothermal pile foundations) with fluid circulating through them, then going through a water-to-air heat exchanger to heat intake air in winter and cool+dehumidify it in summer, without incurring the losses of a heat pump in between, as this should result in vastly higher return on the energy expended. However, I can't find how much higher the effective CoP would be, only vague estimates like "around 30-100". I'm comfortable doing the math on fans, filters and ducts to minimise pressure loss and fan power, but haven't had luck on things like "if I have X m3/h of air and Y l/min of water going through this heat exchanger, and their entry temperatures are Z and W, how much will their temperatures change and how much pressure loss will be incurred in each". Does anyone here know how to find the relevant information and equations?

Does Wales have leeway in ways other than One Planet development? I've looked into that but am not particularly enthusiastic about the requirement to generate income off the land when my comparative advantage lies elsewhere.

I've seen quoted efficiencies (ignoring driver) of around 110 lm/W (e.g. Nichia Optisolis) which seems good enough for dimmer lighting (morning and evening) and in full daylight mode I'd be combining them with more efficient but spectrally suboptimal high-CRI blue-pumped LEDs (I've seen 165 lm/W on greenhouse lights, possibly better nowadays) to reduce the cost in both purchase price and electricity consumption. With sufficient windows (every single house I've been in I've wanted to punch a bunch of additional holes in) the full power should only be needed on cloudy days which also helps, and with mid-pane U-values of 0.5 (LandVac) the windows themselves shouldn't be too much of an issue, especially when considering solar gains on sunny days and "waste" heat output from the lights on cloudy days. Ideally the slight underfloor and wall heating required for radiant comfort in the bathroom could be produced by something like a compost pile for garden waste and no other heating would be needed, so I'd only need a heat pump for DHW (with the ability to optimise for efficiency at high temperatures) and all other efforts would go into preventing the house from overheating with appropriate shading, using ground source non-heatpump pre-conditioning for the ventilation air before the MVHR, etc.

I come from Finland, where the planning is very different: areas get zoned for residential use and the municipal planners specify certain limits (like roof slope and orientation, max ridge height, allowed wall finishes and colours, the part of the plot the house or its outbuildings have to be at, and most importantly the maximum floor area) and then individual builders have a fairly hands-free approach to the details. Unfortunately the planners are very enamored with modernist style and the aesthetic rules tend to reject most of the things I would want (like ornamentation) as "pastiche" and "not reflecting its time" which I in turn consider being stuck in the bad ideas of 100 years ago. As far as I've understood it, in the UK you instead have to apply for every single building as if it was an exception, and when buying a plot there is very little confidence in whether you will be allowed to build what you want if some bureaucrat wants something else. This then seems like it creates a catch-22 where you need to have a design ready so you can know whether you would be allowed to build it on the plot you're considering, but a truly beautiful design cannot be made without extreme sensitivity to the particular details of the specific site. On the other hand if you get planning in principle or outline permission and buy the plot on that basis you'll sink lots of money and open yourself up to the planners twisting your arm however much they want on the details. Meanwhile Paragraph 79 seems to be designed to let rich people build things that look like post-apocalyptic strip malls half-buried in sand as long as they can pay a sufficiently famous architect to hype them up, while aiming for extraordinary levels of merely ordinary beauty is not exceptional enough to qualify even if the vast majority of onlookers would find it much less of an eyesore. On the technical side I'm expecting some people here to get a bit of a chuckle with some of the things I want to do like building the house around/inside a large greenhouse, ventilating it with something like 2-3 ACH (to maintain air quality even as atmospheric CO2 concentrations rise; to limit CO2 to 100ppm above ambient you need roughly 200 m3/h of fresh air per person), having enough indoor lighting to compete with the sun (to prevent seasonal affective disorder; my current living room has roughly 50,000 lumens of light or the equivalent of 60 regular lightbulbs for under 30 sq.m), or using composting toilets with bidet showers regardless of whether a sewer connection is available (to avoid clogging and aerosol plumes and reduce water and paper consumption while improving comfort and hygiene).

Hi everyone! I've been lurking occasionally, now finally made an account. I've immigrated a few years ago so not overly familiar with how things work around here, mainly looking for information on how to be allowed to self-build the way I want. I'm a bit of a mad engineer with strong and specific aesthetic opinions so anticipating quite a bit of friction with bureaucracy. My ideal would be to combine picturesque, almost fairytale-traditional aesthetics with modern high technology (think vacuum glazing, ultra-efficient lighting and HEPA-filtered MVHR, not smart home gadgets; I work in tech so I don't want any unnecessary computers in my home). I like tall ceilings (3.5m tall, not 2.7m "tall"), biodiversity, Christopher Alexander's books, post and beam framing, and violet-pumped LEDs. I dislike fire retardants, wasting energy, pollen allergies, inadequate natural lighting, lawns, and car dependency.