Geothermal Piling

[Caroline]

9 hours ago, PeterW said:

 

I love those sorts of statement..!! 10% of what..??! If you replaced all of your lights with LED from CFL you would easily make 10% but it’s meaningless for a new build.... 

 

Ground mount PV lend themselves to tracking systems so think about placement and exposure. 

Thank you. “Tracking placement” can you explain a bit more please?

[Caroline]

2 hours ago, pdf27 said:

• As I understand it, most oak frame/SIPs combinations now have the oak frame inside and the panels wrapped around the outside of it to avoid cold bridging through the oak. The thing is, SIPs are themselves a structural option, which makes the oak frame largely redundant. If you do follow this route, then I would suggest thinking exactly where in the house you actually want to be able to see the oak - it may for instance be possible to work some oak timbers into the structure of a timber-framed building without needing an entire oak frame, saving £££££.
• More importantly, if the SIPs are on the outside then the only real limitation on thickness is the internal and external dimensions of the building. That means any insulation level up to Passivhaus is possible with a full structural timber frame - see https://www.oakwrights.co.uk/siteI/cfbc0416c099a39a8bd816131025b2d8/press/39935ffd63b49558c7873a6fea6f430e.pdf - but the best way of doing it may not necessarily be with SIPs (the couple in that example didn't use them, for instance).
• If I'm understanding things correctly, the UK building regulations at the moment should limit consumption to about 50 kWh/m²/year for space heating - about 9,000 kWh/year for your proposed buildings. For comparison Passivhaus is defined at 15 KWh/m²/year with a rather more rigorous modelling system to back it up - about a 70% saving over building regulations even before you start looking at heat pumps. By the time the heat demand gets that low even electric resistance heating (which is really cheap to install) is economical to run.
• Don't feel forced to go down the heat pump route - I happen to think it's a pretty good one, but the better insulated your house the better it works. If you're planning on only meeting the minimum PP target, then I would think seriously about alternatives like LPG or Oil: they're well understood, cheap to install and deal well with increasing the output temperature a bit because say your radiators were a bit too small. Personally I think heat pumps are the best solution for a low-energy house, which is why I want to go down that route, but don't make the assumption that they're the best option for every house. Good performance is critically dependent on them supplying heat at a low temperature - the worse the insulation, the harder this is to actually achieve.
• Assuming total annual consumption is about 14 MWh (plug loads, hot water, etc.) then you need about 1.5 MWh/year from PV to meet the PP specification. As a rule of thumb, a 1kW panel facing south in the UK will give about 1 MWh/year of generation - so you could meet it with a 6 x 250W panel system costing maybe £2k for a ground-mount system. That's almost certainly the cheapest way to meet the target, and will be why the PP suggested it.

I would suggest taking a step back and thinking through (in order):

1. What your energy target is going to be - the minimum to meet PP, minimum cost to live in afterwards, or something else. This will define the insulation levels in the structure, which will make clear what else is practicable. If you want to have a play with that, @JSHarris has written a pretty decent heat loss calculator at http://www.mayfly.eu/wp-content/uploads/2017/01/Fabric-and-ventilation-heat-loss-calculator-Master.xls
2. When you know this, work out how you want to deliver the heat - radiators, underfloor heating, warm air, something else? Underfloor will work with just about anything, but warm air and radiators don't play well with heat pumps.
3. Then you can do a meaningful trade-off between ASHP, GSHP, electric resistance, LPG, etc. - knowing the annual heat consumption and peak heating load is critical here because it changes the design of a heat pump system radically, while a traditional boiler system really doesn't change a lot.
   1. If you want building regs minimum and radiators, then you should probably look at LPG or oil - you need quite a bit of heat delivered at a high temperature.
   2. Building regs minimum plus underfloor might well be the sweet spot for a GSHP as demand will be high enough for the COP gain to be worthwhile. It's worth running some calculations on this though - the SCOP figures published by the manufacturers should be good enough for this, divide heat load by SCOP to give electrical consumption and work out if it ever pays back over an ASHP.
   3. If you want Passivhaus or close to it - particularly with underfloor heating - then you should probably look at an ASHP like @jack as the heat load will be so small that there is no point to a GSHP. Resistance heating is feasible at this point, however, and gives you low installation cost with bombproof reliability: at 15 kWh/m2/year and 15p/kWh then your heating bill for a 180m² house is only going to be £400. @TerryE has gone down this route and it has worked very well for him.
4. When you've done all that, then is the time to think about renewables (PV, realistically) - more insulation or underfloor heating is an utter nightmare to add by retrofitting, while a ground-mount PV system is incredibly easy. Make sure you've got the things that are locked in done early, and worry about the rest later.

Well pdf 27, you obviously know your stuff, so glad I joined this forum. I have some homework to do now!  

[Caroline]

8 hours ago, Nickfromwales said:

You can always use lpg for gas cooking btw.   

I’m an induction girl?

[billt]

Tracking systems have the panels fitted to a moveable mount so that the panels are always perpendicular to th esun; they follow the sun through the course of the day. A tracker system will give about 30% more output for a given array than a fixed system. Against that you need an extremely robust tracking mechanism which is going to be expensive. If you have the room it's generally cheaper to have a bigger array than a tracking system.

 

Placement just means that you put your panels in a place that has the most clear view of the sun with no shadows from trees or buildings. Shading reduces PV output enormously.

[Caroline]

2 hours ago, JSHarris said:

There are potential gotchas in Part L1A of the building regs for an all-electric house, that can make it challenging to not use a heat pump or fit PV.  I know we often say that Part L1A isn't a great standard for modern house performance, but in real terms it isn't that bad, either.  In terms of whole house heating requirement it's about 3 to 4 times higher than a passive house, which is massively less than a house built 20 or 30 years ago, and much of that difference comes from the much higher ventilation heat loss.

 

More importantly, though, is the penalty imposed for all-electric heating with no renewable generation.  This would almost certainly rule out resistance heating unless the house was made airtight and insulated to close to passive house levels.  Adding some PV makes a big difference as far as getting the energy use down in SAP is concerned, and is one reason why many new builds have a few panels on the roof - they are there to get an adequate SAP score without needing to air test new houses (which really means not having to make them properly airtight).  Airtightness is, if anything, more important than insulation.  If our house just met the Part L1A airtightness requirement, so had no MVHR, it would need about three times more heat in winter.

 

It's very well worth looking at the trade offs between construction cost (better insulation and airtightness), heating requirement, heating options and how these all impact on the SAP score, particularly for an all-electric house where it's already challenging to meet the requirements now.  You may well find that you're driven to use an ASHP with a house built to just meet building regs, because it would not pass if fitted with electric resistance heating.

 

On the topic of oak frames, I know at least one passive house company that can supply oak internal frames for their passive house kits, so it may well be an option to consider.  I suspect it's a cheaper approach than the structurally wasteful SIPs over oak frame option, which always struck me as being just an idea that one oak frame company came up with as a way to continue to sell their standard oak frames yet still meet current building regs requirement (there are issues with oak frame movement over time that make it easier to have two structurally independent "frames" like this).

Hi JSH, are you able to let me know the PH company? Would they supply a traditional cottage? ps wish you was my neighbour, would be inviting you round regularly for a self-build coffee?

[Jeremy Harris]

1 minute ago, Caroline said:

Hi JSH, are you able to let me know the PH company? Would they supply a traditional cottage? ps wish you was my neighbour, would be inviting you round regularly for a self-build coffee?

 

Have a read of @dogmans recent post (we used the same company and were very pleased with them, so I'm a bit biased!):

 

[divorcingjack]

Hi Caroline, 

 

I have only one bit of advice as your head is probably exploding. This forum has a habit of doing that - you think you've made a decision (just one!) and then you come on here and start reading and everything changes. Keep an open mind ( even to things that you had previously ruled out) and you may end up with a much better house that you started with in your head, I know I have. 

 

Good luck! 

[vivienz]

2 hours ago, divorcingjack said:

Hi Caroline, 

 

I have only one bit of advice as your head is probably exploding. This forum has a habit of doing that - you think you've made a decision (just one!) and then you come on here and start reading and everything changes. Keep an open mind ( even to things that you had previously ruled out) and you may end up with a much better house that you started with in your head, I know I have. 

 

Good luck! 

 

I fully second this.  The house that we're building now is very different to the initial concept, and the change to the heating and hot water systems are probably the most radical.  When I first looked at BH, before we had bought our plot, I hadn't a clue about a lot of the stuff going into our house, or how the house is being built.  I'm a couple of years older and wiser now - wise enough to realise that there's even more stuff about which I know somewhere between zero and absolutely nothing.

[Ferdinand]

Rumsfeld on unknown unknowns.

 

Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones

 

Best of luck.

Edited June 18, 2018 by Ferdinand

[pdf27]

9 hours ago, Caroline said:

Well pdf 27, you obviously know your stuff, so glad I joined this forum. I have some homework to do now!  

Bear in mind that I was once described by a crusty old RAF flight sergeant as "being able to tell you the square root of a jar of pickled eggs but unable to get the f***ing lid off". I like to think that I've improved a bit in the years since, but being as I haven't yet built anything all my comments need to be treated as theoretical rather than real. 90% of them are probably right, but...

 

9 hours ago, billt said:

Tracking systems have the panels fitted to a moveable mount so that the panels are always perpendicular to th esun; they follow the sun through the course of the day. A tracker system will give about 30% more output for a given array than a fixed system. Against that you need an extremely robust tracking mechanism which is going to be expensive. If you have the room it's generally cheaper to have a bigger array than a tracking system.

 

Placement just means that you put your panels in a place that has the most clear view of the sun with no shadows from trees or buildings. Shading reduces PV output enormously.

I think trackers are a solution to a problem that no longer exists for terrestrial systems - when they were first a thing PV was hideously expensive and they added 1% to the price of the system for a 30% increase in capacity. Now PV panels and inverters are cheap, it adds >100% to the price of the system for a 30% increase in capacity - no longer such a great deal.

 

8 hours ago, JSHarris said:

 

Have a read of @dogmans recent post (we used the same company and were very pleased with them, so I'm a bit biased!):

 

I think Touchwood do something similar going by their website, and they also have a few happy customers on here (if fewer than MBC). There are probably a number of other companies capable of the same sort of thing.

 

4 hours ago, vivienz said:

 

I fully second this.  The house that we're building now is very different to the initial concept, and the change to the heating and hot water systems are probably the most radical.  When I first looked at BH, before we had bought our plot, I hadn't a clue about a lot of the stuff going into our house, or how the house is being built.  I'm a couple of years older and wiser now - wise enough to realise that there's even more stuff about which I know somewhere between zero and absolutely nothing.

One of the things that it's really difficult to teach new engineers to actually do is to write a solution-neutral problem statement. That is, a description of what you are trying to achieve which does not indicate in any way how you are going to do it. It's a very valuable exercise because it often gets you thinking of new ways to attack the problem, but people instinctively think of ways to solve a problem as soon as they start working on it and that leads to particular approaches being adopted, whether or not they are appropriate. In this case, for instance, the problem statement was "we want a house built with an oak frame and SIPs shell" rather than "we want a house with oak beams visible in rooms X, Y and Z". The latter statement invites a far wider choice of potential solutions to the same problem, and the more solutions are considered the better your chances of finding the best one for your requirements.

[Jeremy Harris]

7 minutes ago, pdf27 said:

I think Touchwood do something similar going by their website, and they also have a few happy customers on here (if fewer than MBC). There are probably a number of other companies capable of the same sort of thing.

 

Yes, Touchwood do, as I mentioned earlier in this thread.  I've seen one of the builds but not one with oak framing internally.  When I got a quote they were expensive, though.

[Gone West]

13 hours ago, pdf27 said:

I think Touchwood do something similar going by their website, and they also have a few happy customers on here (if fewer than MBC). There are probably a number of other companies capable of the same sort of thing.

 

Friends of ours used Touchwood Homes and are very happy with their build.