Energy Tariffs

[marshman]

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[pudding]

Hi, Thanks for the replies.

Yes with the GSHP, it would be left in auto mode for heating, as it is now, and simply turns on when needed. From memory last winter with thermostats set to 20deg or so, it would come on 3 or 4 times a day to fill up the 300L underfloor heating buffer tank when that tanks temp dropped to the min. I was planning on changing all of the thermostats in the house to demand a nice warm temperature overnight, say 26/7degs, such that the GSHP will be running most of the time I imagine, topping up the buffer tank for the underfloor heating, as the underfloor heating pumps will keep pumping the water out of the buffer tank until its reaches the target room temps. (if it ever would, depends obvs on response time and temp of water from the GSHP/buffer tank, some possible tweaking there to do to make the best of it), and then hopefully after getting to mid-20's fingers crossed by the evening the house would still be warm and not have needed to turn on the underfloor heating again (or too many times at least!) to try and reach a normal set temp of 20deg.

Sounds like it'll be best to wait a few more weeks and see what happens.

[Oldgreybeard]

We run our air source heat pump exclusively at night, during the heating season. I did, however, design the heating system to run using Economy 7, so we have a large (around 15 tonne) concrete storage heater, as the heat pump heats up the floor slab, via deeply embedded pipes. That slab has 300mm of insulation underneath it and around the sides, so stores plenty of heat with fairly low losses.

The system was designed to be self-regulating, by operating with a low temperature differential between the room and floor surface temperature. When the room cools the floor gives out more heat, as the differential rises. As the room warms the floor heat output reduces. During the day, when we are in and doing stuff, the heat we produce tends to be enough to keep the house warm, together with a bit of solar gain, perhaps. This means that the floor doesn't need to heat the house much. In the evening, when it starts to cool slightly, the floor heat output increases because of the increase in the temperature differential, and so keeps the temperature up.

This really only works OK because the house was designed to have a high decrement delay in the structure. This doesn't come from mass, really, but mostly from having lots of relatively high specific heat capacity materials in the structure. The net result is that it typically takes the house between 24 and 48 hours to drop 1°C internally, with no heating on, during typical winter weather here. With no heating at all, the house settles at about 12°C to 14°C in winter, with no one in it (found this out when building it). One person working indoors raises the temperature to around 18°C or more in winter, without heating (other than incidental heating from tools etc). I did over-heat the house badly one day when building it, when I decided to have a massive clean up and used a big industrial vacuum cleaner for an hour or so. The heat from that raised the house temperature up to over 25°C and it remained a bit uncomfortably warm (for working in) for a couple of days afterwards.

[Countrypaul]

We do very similar to OGB, in that we run our ASHP predominately overnight from E7 and only during the day if it is very cold. Unlike OGB's place, ours is a renovation in a conservation area so we were limited in alot of what we could do. We have a B&B floor with 120mm PUR insulation with UFH pipes and 70mm S&C screed (22tons of screed used), with 50mm of PUR against the external walls and 25mm against the internal walls (all largely original).

The UFH heating is set to 21C for the E7 period dropping to 20C until late evening when it is set to only 18C (some rooms are set lower). There is UFH only in the first floor bathrooms, al the bedrooms have no heating present. The bedrooms only get too cold* if the bedroom doors are kept closed all day and it is very cold outside. There is a 430L Thermal Store connected to the ASHP and UFH, with 2 immersion connected to an Eddi and connections for Solar Thermal and WBS neither of which are curerently implemented. The ASHP is set to automatic and only comes on when the TS drops below a preset temperature (25C at present).

Having 2 kids into computer games tends to mean there is a significant early evening boost to the house heating when they get home from school. One uses a normal PC plus Xbox, the other has a more dedicated gaming PC with twin screens, high end graphics card etc.

We seem to use about 8500kWh pa, although we also have a 3.3kWp PV install, though no battereis (yet).

*Too cold - defined by SWMBO (seems to vary)

[SafetyThird]

We run our air source heat pump exclusively at night, during the heating season. I did, however, design the heating system to run using Economy 7, so we have a large (around 15 tonne) concrete storage heater, as the heat pump heats up the floor slab, via deeply embedded pipes. That slab has 300mm of insulation underneath it and around the sides, so stores plenty of heat with fairly low losses.

The system was designed to be self-regulating, by operating with a low temperature differential between the room and floor surface temperature. When the room cools the floor gives out more heat, as the differential rises. As the room warms the floor heat output reduces. During the day, when we are in and doing stuff, the heat we produce tends to be enough to keep the house warm, together with a bit of solar gain, perhaps. This means that the floor doesn't need to heat the house much. In the evening, when it starts to cool slightly, the floor heat output increases because of the increase in the temperature differential, and so keeps the temperature up.

This really only works OK because the house was designed to have a high decrement delay in the structure. This doesn't come from mass, really, but mostly from having lots of relatively high specific heat capacity materials in the structure. The net result is that it typically takes the house between 24 and 48 hours to drop 1°C internally, with no heating on, during typical winter weather here. With no heating at all, the house settles at about 12°C to 14°C in winter, with no one in it (found this out when building it). One person working indoors raises the temperature to around 18°C or more in winter, without heating (other than incidental heating from tools etc). I did over-heat the house badly one day when building it, when I decided to have a massive clean up and used a big industrial vacuum cleaner for an hour or so. The heat from that raised the house temperature up to over 25°C and it remained a bit uncomfortably warm (for working in) for a couple of days afterwards.

That sounds like a fascinating build OGB, do you have any more info on it anywhere, would love to get a better idea of what you've built.

[Oldgreybeard]

That sounds like a fascinating build OGB, do you have any more info on it anywhere, would love to get a better idea of what you've built.

Sadly not. I did start writing a blog, way back in the mists of time, but lost interest in it once the build started, mostly because self-build takes up every waking moment. In essence the design was mine, to fit the plot of land, make sure the roof faced the best way for the solar panels, etc, then the house itself was made off-site in a factory, as prefabricated panels that were assembled on site. I then did most of the fitting out, plumbing, heating system, ventilation system, wiring, fair bit of the joinery, kitchen and bathroom installations, etc.

The basic specs are:

Net floor area: 131m²

Insulation: 300mm foam under the floor slab, 300mm in the walls and 400mm in the roof panels The wall insulation overlaps down over the edge of the slab and joins the underfloor insulation. The wall insulation also tightly joins the roof insulation. This reduces the chance of thermal bridging, in effect the insulation is contiguous all around the whole house.

Heating and cooling: Air source heat pump that can heat or cool the 100mm thick ground floor concrete slab, using embedded underfloor heating pipes. There's no heating upstairs, just heated towel rails in the bathrooms. The house gets a bit warm in summer, so I added a small air to air air con unit upstairs. This cools the bedroom and also the whole house if we leave the doors open. Doesn't cost anything to run, as we only need it when it's warm, so it runs almost entirely of excess solar generation. I can also cool the floor with the main heat pump, again this runs for free, as it's only on when it's warm and sunny. In winter the house needs just a few hundred watts of heating to stay comfortably warm. Much of the heating comes from waste heat from us and things running in the house. When the heat pump is on it tends to draw slightly less than 1kW, so uses less than 7kWh for an average day's heating. We use more energy cooling the house in summer than we do heating it in winter, but all of the cooling energy comes from the PV system, so doesn't cost anything.

Glazing: All doors and windows are triple glazed, passive house certified. Only downside is that doors and windows are very thick - the glazing units alone are 52mm thick, and the doors are around 120mm from inside face to outside face (they are like strong room doors!).

Airtightness: There's an airtightness layer on the whole inside of the house, sealed to the edges of the doors and windows with airtightness tape and sealant. Anything that passes from the walls is sealed both sides. The house was air tested and came in with a leakage rate well below the minimum acceptable for a certified Passivhaus.

Ventilation: Every room has ducting in the floor/ceiling void feeding either fresh air supply terminals (in all habitable rooms) or stale air extract terminals (bathrooms, kitchen, utility room, downstairs WC). The ducting is all fed back to a heat recovery ventilation unit, that extracts heat from the stale air and uses it to warm the incoming fresh air. The fresh air intake has a fine filter (F7, so filters down to about 2.5µ) that keeps out dust and pollen. This ventilation system automatically boosts the ventilation rate if it senses high humidity in the extract air, so when cooking or when showering.

Lighting: All LED, a mix of LED lamps in conventional fittings plus lots of LED panel lights in the kitchen, utility room, bathrooms etc.

Water and drainage: We don't have mains water or drainage, so have a well for water, with a submersible pump and filtration system that supplies the house and outside taps. Drainage is a mix of a large soakaway for roof and surface water plus a sewage treatment plant that discharges clean effluent to the stream alongside the house (with a licence to discharge from the EA).

[SafetyThird]

Wow that sounds amazing. what a fabulous project, thanks for taking the time to write all that up, very interesting indeed.

[Oldgreybeard]

Wow that sounds amazing. what a fabulous project, thanks for taking the time to write all that up, very interesting indeed.

Thanks. At the time I started working through ideas for a zero energy home, in the late 1990s, everyone I knew thought I was a bit of a nutter, including my wife. I remember a holiday in France in 1999 when, whilst my wife was enjoying the pool, I was sat with a notepad, sketching ways to best build a low energy home. Even when I started the build, in 2012, the general view of most people I spoke with seemed to be that I was bonkers, and going way over the top with the energy efficiency.

By 2016, things were starting to change. The house was finished and seemed to attract some attention, kicked off by the council (who had not been supportive) when they called me to question whether the EPC that I'd lodged (giving a rating of A107) was correct. They were struggling to understand how a house could be more than 100% efficient (notionally, A100 would be a zero energy home).

I then got asked to give talks to various groups about the design and build of the house, ranging from a group of church people interested in saving energy (attended by the local bishop, no less) to a request to give a talk in the local village hall (amazingly, the place was packed).

My wife and I have just watched the last episode of Frozen Planet II this evening, which ended with Sir David Attenborough appealing for us to change. My wife turned around to me at the end of it and just said "you were right about all this energy stuff 20 years ago, weren't you?". Best compliment I've ever had, but I regret to say that I was still 50 odd years too late.

[Stinsy]

Wow that sounds amazing. what a fabulous project, thanks for taking the time to write all that up, very interesting indeed.

Thanks. At the time I started working through ideas for a zero energy home, in the late 1990s, everyone I knew thought I was a bit of a nutter, including my wife. I remember a holiday in France in 1999 when, whilst my wife was enjoying the pool, I was sat with a notepad, sketching ways to best build a low energy home. Even when I started the build, in 2012, the general view of most people I spoke with seemed to be that I was bonkers, and going way over the top with the energy efficiency.

By 2016, things were starting to change. The house was finished and seemed to attract some attention, kicked off by the council (who had not been supportive) when they called me to question whether the EPC that I'd lodged (giving a rating of A107) was correct. They were struggling to understand how a house could be more than 100% efficient (notionally, A100 would be a zero energy home).

I then got asked to give talks to various groups about the design and build of the house, ranging from a group of church people interested in saving energy (attended by the local bishop, no less) to a request to give a talk in the local village hall (amazingly, the place was packed).

My wife and I have just watched the last episode of Frozen Planet II this evening, which ended with Sir David Attenborough appealing for us to change. My wife turned around to me at the end of it and just said "you were right about all this energy stuff 20 years ago, weren't you?". Best compliment I've ever had, but I regret to say that I was still 50 odd years too late.

Great work. And good on you for getting something non-mainstream built and managing to be proven “right” so shortly thereafter.

I’m annoyed that all these years later all houses are not built like that. New-build housing estates all over the country are currently being constructed with no solar panels and with gas boilers.

[sharpener]

The UFH heating is set to 21C for the E7 period dropping to 20C until late evening when it is set to only 18C (some rooms are set lower). There is UFH only in the first floor bathrooms, al the bedrooms have no heating present. The bedrooms only get too cold* if the bedroom doors are kept closed all day and it is very cold outside. There is a 430L Thermal Store connected to the ASHP and UFH.

Am thinking of something similar. What kind of thermal store do you have @Countrypaul? I have looked at Sunamp (very expensive) but their current range only includes models for hot water thought they have told me versions for heating are in the pipeline (again).

We have a barn conversion with UFH, and my long term thinking is more PV plus a small ASHP running all the time there is daylight or off-peak grid. With a thermal store to last through the evening until the off-peak comes on.