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Author Topic: Advice on Self Build  (Read 7640 times)
Smirker
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« Reply #15 on: November 26, 2012, 08:17:52 PM »

Thanks. I had a look at the system diagram  but it's all way above my limited knowledge. I just hope I can find an installer who's not as clueless as I am (shouldn't be difficult) The principle of a tank with various inputs/outputs still holds true though, no matter how complicated the diagram looks facepalm.

Been researching various systems and the Genvex Combi seems to come out quite well as an integrated solution for DHW/space heating and MVHR. Any views on this system?
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brackwell
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« Reply #16 on: November 26, 2012, 08:26:13 PM »

Bornagain,

Thanks for that.

Have no probs with your thinking and i would have assumed COP 3.5 .  However i have never calculated using E7 because by doing so it makes the day rate more expensive and negates the advantage but i guess if you introduce the pv effect then maybe that assumption is not correct but it will clearly affect households differently.

Ken
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bornagain
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« Reply #17 on: November 26, 2012, 08:42:23 PM »

Smirker,

The piping up of the UFH is not as complicated as it looks - it boils down to a fancy valve connected to  the tank top, tank middle, tank bottom and UFH manifold.

Give Accumulator Tanks a ring and get the chap to explain -its quite simple - its even simpler if you look at one in the flesh. Mine is in North Lincolnshire if it helps....or send me a mail.

As for MVHR - as long as you stick to a few simple rules - you can do it all yourself - I did. It works really well, is quiet, and consumes practically no energy. 

P.
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Smirker
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« Reply #18 on: November 27, 2012, 02:57:58 PM »

Hi , thanks for the advice. I will take a look at those tanks. Also found Chelmer Heating who do Thermal Stores which can be linked to UFH, Solar Thermal etc so will give them a call. Think I am starting to get my head around all this now extrahappy
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desperate
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Backache stuff!!


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« Reply #19 on: November 27, 2012, 06:45:32 PM »

This is my take on putting an UFH system together whilst sidestepping all that overpriced baloney that the manufactureres try to sell you, all controlled by a roomstat a standard timer and a mixing valve.

http://www.navitron.org.uk/forum/index.php/topic,8465.msg209746.html#msg209746

Dsep
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www.jandhbuilders.co.uk

still a crazy old duffer!
dullnote
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« Reply #20 on: January 25, 2013, 02:16:53 PM »

Hi I also self built, one thing I did not do was put in a thermal store, get one with plenty connections, this will allow you to connect any heat source.

But more important, insulation, the more the better, again I increased the insulation but now wish I went further now looking at ways to improve

Dullnotr
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charlieb
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« Reply #21 on: January 25, 2013, 06:12:30 PM »

Well said Bornagain. REally good to hear what seems obvious in theory borne out in practise.

Smirker.  If you're selfbuilding you should be able to design a building that hardly needs any heating input at all.  What I would do is:
  • Definitely have a large thermal store/hot water tank, with multiple inputs (as below)
  • midsized woodstove/bellet stove.  Because they're lovely to sit round, and it gives lots of heat relatively fast on exceptionally cold days
  • Solar thermal.  Hot water in the summer, means boiler/immersion doesn't need to run
    • Small gas boiler, if ongrid, to top up the store when solar/wood aren't managing - basically for DHW in winter when you don't want to light the fire.  Or immersion if off gas grid but on electric. You shouldn't need to use this much at all
    Gas-driven GSHP heat pump I might consider, but I wouldn't get an electric one, and certainly not air source. Ground soure heat pumps are pretty much exactly as green and exactly as expensive to run as a condensing gas boiler, and significantly more up-front hassle. Air Source heat pumps might be cheaper but they're more expensive/dirtier to run and won't really be able to provide properly hot water.

    Incidentally, Navitron supply much of the kit (certainly thermal stores, solar tubes) and may be far more clued up about specific requirements than your average tank maker.  (I have no connection btw.  Admins, I hope I'm allowed to promote our hosts!)
« Last Edit: January 25, 2013, 06:17:53 PM by charlieb » Logged
Les101
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« Reply #22 on: January 25, 2013, 08:57:33 PM »

The GSHP v Gas argument isnt as straight forward as some suggest.

We fitted a Ground Source pump a couple of years ago - very straight forward once youve mastered not hitting the house with the digger!

Kensa pump was just over 5k including antifreeze, made our own ground loops with some pipe off Ebay & a bag of cable ties, for just ove 200. Manifolds cost around 150 to make & the digger was 500 for 2 weeks.

We got a grant for 1200 so all in total cost was just under 5000 + some hard work due to very rocky soil

Its expected to last 25 years with very little maintenance.


My cousin has built his son a house around the same time & the plumber talked them out of heat pumps so they went down the gas boile route.

Cost about 3000 to have gas installed to the house & over 1000 for boiler & installation so already similar cost to us & they have loads of land & free use of a JCB.

The Gas boiler in their holiday cottage has been trouble since new, has cost a fortune in repairs & needs replacing at about 8 years old.
Presumably, they have gone for a different make this time but it wasnt cheap rubbish last time.

I dont know how the RHI would pay with them being able to get gas, if they had not had the connection, but even without the RHI, the Heat Pump looks a much cheaper option.

Alll cases are different so everyone needs to do their own calculations and see what is best for their situation
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dullnote
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« Reply #23 on: January 26, 2013, 10:29:30 AM »

Hi Les I agree with your comments, I did not have land to put in loops, bores too expensive  so went for ASHP, and am happy when compared with LPG. I think at present if you can fit GSHP your self go for it, if not and you have towns gas use that but there is very little difference

Dullnote
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Smirker
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« Reply #24 on: January 29, 2013, 03:52:13 PM »

Thanks to all for keeping the thread alive extrahappy I have been offline since we moved house in early Jan due to the incompetence of BT! Having done some further research it boils down to us using one of two routes. Route 1. We have gas so could use a thermal store fed by a boiler and solar thermal which will provide DHW and space heating through UFH. Cost for this about 8.5k plus installation from Chelmer Heating.

Route 2 is to use Earth Save Products Ecocent for DHW and a seperate boiler to run the UFH. Not got costs for this yet but I anticipate it will be similar. Sceptical about using an external ASHP to run the UFH. Space is tight to the sides of the house and I don't want a big shiny box on my patio! Could a wood burner be a viable option for the UFH? Solar PV but not thermal as ESP guy thinks we don't need it with the Ecocent.

I did get a quote for Genvex EAHP/MVHR unit plus a Genvex thermal store but that was about 14,000 including installation hysteria.

We intend to insulate to sub-passive levels (175mm in timber frame walls and 200mm in the floor) and be as airtight as we can. <3 ach is the target.

Any opinions on the above? Am I overcomplicating and should just be shoving a boiler in along with some solar panels? Everyone says we will need MVHR. Do we really as it's not cheap?
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titan
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« Reply #25 on: January 29, 2013, 04:38:48 PM »

I am not convinced by the large thermal store route. If you have good insulation and gas then ufh and an unvented dhw cylinder sized for your lifestyle should do all you need. You could have solar thermal for summer use or if you are also going for pv fit an Immersun ( or similar) With a thermal store the temperature will need to be kept 10 deg above your highest demand increasing the standing losses as will the all the long pipe runs to and from the various heat sources and extra pumps. Admittedly not so much fun.
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Smirker
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« Reply #26 on: January 29, 2013, 05:00:52 PM »

I am not convinced by the large thermal store route. If you have good insulation and gas then ufh and an unvented dhw cylinder sized for your lifestyle should do all you need. You could have solar thermal for summer use or if you are also going for pv fit an Immersun ( or similar) With a thermal store the temperature will need to be kept 10 deg above your highest demand increasing the standing losses as will the all the long pipe runs to and from the various heat sources and extra pumps. Admittedly not so much fun.


Thanks for the practical advice. Meeting with a plumber on Thursday to discuss options so I will mention this to him. Sure it will be cheaper both short and maybe long term.
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dhaslam
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« Reply #27 on: January 29, 2013, 05:17:44 PM »

If you have a very airtight house you must have a ventilation system and a heat recovery setup  gives you fairly warm air coming in and the air is filtered.  It might also be a way  to provide hot water except that the exhaust heat pumps can be expensive.   It is easy to fit the ventilation pipes in the ceilings when the house is being built.  

If the house is  passive it would be hard to have a woodburner that could heat water without  overheating the room.  Also underfloor heating should only be needed to  give very slight heat in bathrooms and  north facing rooms.  Other rooms can have very widely spaced  piping.    There are a lot of options  for  low volumes  heat  but I think that  PV panels  plus small heat pump plus immersion supplying a large buffer tank makes a lot of sense.   Underfloor heating should only be needed in the early morning and in the evening  which wouldn't line up with peak PV output.   Also of course there would be excess electricity in summer and a shortfall in winter.    
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DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
Smirker
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« Reply #28 on: January 29, 2013, 06:07:16 PM »

Thanks Dhaslam.

The house won't be to Passive standards but hopefully not far off. If no UFH then how would you go about space heating? Looked into an EAHP but expensive as you say and the anecdotal evidence is that they don't provide enough heat in really cold weather.I see what you mean about UFH demand not matching with PV output but the pV would be used to offset rather than directly power the UFH. We have gas available so it's a dilemma whether to just keep things simple or to go down the more complicated Ecocent route which, in essence is a large buffer tank with an integral heat pump. Ecocent+PV+uFH perhaps? Will definitely go with MVHR and solar, just trying to work out the most efficient way of heating/supplying hot water.
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A.L.
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« Reply #29 on: January 29, 2013, 06:38:40 PM »

hello,

We intend to insulate to sub-passive levels (175mm in timber frame walls and 200mm in the floor) and be as airtight as we can. <3 ach is the target.

Any opinions on the above? Am I overcomplicating and should just be shoving a boiler in along with some solar panels? Everyone says we will need MVHR. Do we really as it's not cheap?

optimistically 175mm of good fibreglass (lambda 0.035) in a timber frame could give U=0.22 (Passivhaus max 0.15)

3ach@50Pa is five times Passivhaus max of 0.6ach@50Pa

200mm of floor insulation should be about U=0.12 so O.K.

if you want to minimise energy use MVHR is a sensible choice, at times recovering 30x energy used to power it

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