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Heating Confusion


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31 replies to this topic

#21 SteamyTea

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Posted 25 February 2016 - 04:26 PM

I know of them, but never had any dealings with them, or know of anyone that has.

I take it your near Helston then.

Edited by SteamyTea, 25 February 2016 - 04:27 PM.


#22 Hoops

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Posted 25 February 2016 - 07:43 PM

View PostSteamyTea, on 25 February 2016 - 04:26 PM, said:

I know of them, but never had any dealings with them, or know of anyone that has.

I take it your near Helston then.
We are in Hayle and building in Tehidy near the golf club.

#23 SteamyTea

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Posted 25 February 2016 - 08:51 PM

I know both well, often have a coffee in Hayle, and in the woods.

#24 cjard

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Posted 26 February 2016 - 12:37 AM

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View PostHoops, on 25 February 2016 - 04:05 PM, said:

I just seem to be going round in circles with the gas or no gas issue. I don't actually know anyone who has fitted an ASHP but I am hoping to visit one of the customers of the local firm who are trying to convince me of its merit

Nooo.. That's not how the decision flow is supposed to work. It goes like this:

Building on mains gas grid?
Yes: install cheap reliable advanced gas boiler and use a few quids worth of mains gas per year. The end.
No: go round in circles between: currently cheap but volatile finite oil, expensive monopolised lpg, very expensive high maintenance biomass, outrageously expensive ground source, cumbersome dirty medieval wood burning stove, overly expensive unecological ASHP that's useless for hot water, over complicated hybrid of the aforementioned with some PV and solar thermal thrown in around a thermal store

Yikes. The more you read into it, the more it will do your head in. Make the decision now to use gas, build your house right and you may not in the rest of your lives spend as much on gas as your ASHP will cost (7k+ if you do it through an MCS co in order to get the RHI grant, which may be a white elephant if the low payments never recover the premium of paying the co)

ASHP have some benefits: they can cool the house too (no RHI compliant install does unless it has been messed with since registering for payments), and in some scenarios they can be a DIY install. They're predominantly crap at producing hot water (your ufh runs on warm water, which they do well) but there are a select few that do well, usually by relying on another technology like a gas boiler for a boost.

When you go to see your people bear in mind that people seldom want to admit to being responsible for making a bum decision and will often talk something up if they aren't privately so enthusiastic about it. Specifically ask them how much time the unit spends defrosting itself in spring and autumn when the world is quite damp but not so cold that the water in general air hasn't frozen on something else before blocking the ASHP up. If they know and can give you detailed assurances that it's a minimal amount of time because they've compromised their lifestyle and adjusted their hot water expectations to match the technological and physical capabilities of he unit, then be sure you're happy to make the same adjustments. If the news that it regularly blocks up with ice and must murder it's own efficiency unblocking itself is news to them/they just set 55 on the thermostat, pay the electric bill and let the unit worry about itself then (sorr to say) they probably won't be the right people to give an honest in depth appraisal of what living wih an ASHP is like. Unless of course, you're happy to take the same approach!

For what my father in law paid for his ASHP, plus what I've been quoted for mine, plus some reasonable chipping in from 3 neighbours, I reckon we could probably have got mains gas brought the quarter mile up the hill to our site. I do still wonder why we didn't consider it way back then. Lack of foresight was probably one, his brother ranting on about how amazing ASHPs are another. His brother builds houses that footballers buy though; not exactly the sort of people who care about the electricity bill if the system sizing was wrong or it spends a lot of time defrosting

Edited by cjard, 26 February 2016 - 01:13 AM.


#25 Hoops

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Posted 26 February 2016 - 03:41 PM

thanks cjard. Very eloquently put and echoing what a lot of people have said since I have been asking the question. I think I made the decision early on to use gas with my architect and have had my head turned whilst looking for quotes for the UFH. I am of the opinion now that for my particular build the gas boiler will be best.

#26 jsharris

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Posted 26 February 2016 - 03:44 PM

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If we had mains gas then I'd have fitted the most efficient small combi I could find that met our hot water needs, and coupled it with a Sunamp PV so that I could have an efficient way of storing excess PV generation for the provision of hot water, reducing or eliminating the need for the combi to fire up at all during good weather.

#27 SteamyTea

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Posted 26 February 2016 - 03:49 PM

Hoops
As you are 'in the woods'. will the new plot suffer from tree shading on the roof? If so, it may make PV less effective.

#28 Hoops

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Posted 26 February 2016 - 03:53 PM

No we are on the outskirts of the wood and I have just spent £7000 removing 4 60ft pines that were obliterating the plot. The PV is non-negotiable if we have gas because the local authority insist on them to meet the SAP apparently.

#29 jsharris

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Posted 26 February 2016 - 04:36 PM

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View PostHoops, on 26 February 2016 - 03:53 PM, said:

The PV is non-negotiable if we have gas because the local authority insist on them to meet the SAP apparently.

They cannot do this, unless there is a specific planning policy saying that all new developments shall have renewable generation (RE).

SAP is a red herring, it's a Building Control method used to ensure compliance with Part L1a of the building regulations, and nothing at all to do with the planning authority, as you can use a private company for building control approval if you wish.

I've just had a quick scan through the core planning policies for Cornwall and there is no mention of mandating the use of RE on new developments at all, as far as I can see. Personally I think that RE is a good thing, but I'm not at all sure I'd agree with any policy that made incorporating it mandatory.

All new houses should be able to "pass" the SAP assessment, which is a misnomer anyway, as there is no real pass or fail, you just have to ensure that the DER (the Dwelling Emission Rate) is lower than the TER (the Target Emission Rate). It's easy to do this with a properly designed home with out having to fit PV panels, in fact if someone is telling you that you need to fit PV in order to get the DER equal to or below the TER then that means the house is very badly designed, and is lacking in insulation, has poor airtightness or is otherwise using more energy than it should.

Factoring in the fact that our building regulations in Part L1a are pretty poor and easily met by the sort of rubbish built by the big developers, and it's clear that there's some misunderstanding somewhere about what's required to make a new dwelling adequately energy efficient.

Certainly some of the big developers fit PV panels because it's cheaper than making the house adequately insulated or airtight, it's a sort of "rule cheating" manoeuvre to lower the DER below the TER on a house that is poorly designed or built.

The general rule when designing and build a new house for yourself is to make the basic structure as airtight, well-insulated and cold-bridge free as you can, and only then think about adding things like PV panels if you want them and they will give a useful energy saving. By following this approach you can significantly reduce the complexity (and cost) of any heating system (if you build to the sort of standard we, and a few others here have built to, then heating is almost unnecessary).

Edited by jsharris, 26 February 2016 - 04:37 PM.


#30 SteamyTea

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Posted 26 February 2016 - 09:28 PM

I have not heard of it being a planning condition down here, and I am sure I would have.
Not seen any on any of the new builds in that area either, not even the 'eco' ones at Portreath and South Crofty.

#31 cjard

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Posted 27 February 2016 - 08:21 AM

On the SAP scoring thing, Jeremy noted recently an example of how skew wrong it can be- a terribly insulated and energy wasteful house that scored 135 out of 100 simply because it has 30 kilowatts of PV generation ability. Compare that to the lengths J went to to "only" score 107 and you start to wonder whether Volkswagen had a hand in writing the SAP scoring system. Make sure you leave your garage door open when the assessor is looking and it should get a pass ;)

Edited by cjard, 27 February 2016 - 08:23 AM.


#32 jsharris

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Posted 27 February 2016 - 08:59 AM

View Postcjard, on 27 February 2016 - 08:21 AM, said:

On the SAP scoring thing, Jeremy noted recently an example of how skew wrong it can be- a terribly insulated and energy wasteful house that scored 135 out of 100 simply because it has 30 kilowatts of PV generation ability. Compare that to the lengths J went to to "only" score 107 and you start to wonder whether Volkswagen had a hand in writing the SAP scoring system. Make sure you leave your garage door open when the assessor is looking and it should get a pass ;)

As another example of the way SAP can be easily skewed by developers "gaming the system" I was invited to look around a local development that had only been granted PP after a long battle with the locals over it's "eco" credentials. All the small houses had half a dozen PV panels on the roof, and these were proudly mentioned on the blurb from the developer. When I got home and checked the SAP scores I found that they had just scraped through the Part L1a airtightness limit (so pretty poor really) and none of the houses had heat recovery ventilation, all had window trickle vents.

A quick "back of the fag packet" calculation showed that it was cheaper for the developers to build the houses to a poor energy efficiency standard, then get the SAP DER down to scrape under the TER by adding a few PV panels then it would have been to make the houses more energy efficient. All these houses were EPC band C; without the PV they would have been Band D or lower.

Edited by jsharris, 27 February 2016 - 09:00 AM.