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Author Topic: New build newby  (Read 3820 times)
mikrt
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« on: October 04, 2012, 02:27:41 PM »

Hi forum,
We've just received detailed planning approval for a 220m2 house in West Wales. Our intention has always been to avoid using oil again as prices are only going one way!
We plan to use a wood pellet boiler with UFH on ground floor, with a few thermal solars on the garage roof to supplement it.
Just wondering, before we start paying money, if you all think this is likely to work and if so, what size water/buffer (or whatever) tanks would be recommended.
The house will have to be minimum code 3 sustainable, but we intend going a little beyond that, getting it airtight(ish) - no trickle vents anywhere, no letterbox and triple glazing too. Along with upping the insulation above recommended (not been confirmed yet).
Also using rainwater harvesting and mechanical heat recovery.
Lot of questions I realise, but any help or suggestions would be really appreciated,
Thanks, Mike.
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A.L.
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« Reply #1 on: October 04, 2012, 03:02:53 PM »

hello and welcome,

Not a lot of details to comment on! - but here goes, you are not likely to require a heat input averaging 5kW to maintain a 25C temperature difference with the outside and it could relatively easily be reduced to 3kW.

So be careful about the size of the pellet boiler, if the boiler is in a habitable room the biggest problem is likely to be local overheating unless you have a open plan design.

Is the UFH a concrete floor slab, how thick? or a timber floor. A thick concrete floor slab could use off-peak electricity and 'free wheel' during daytime. Boilers and pellets are not cheap.

Usually a buffer store of 50l/kW of output is recommended, a 300l DHW cylinder would seem reasonable if house has average occupancy/use, so maybe possible to combine.
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clockmanFR
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« Reply #2 on: October 04, 2012, 06:50:48 PM »

Welcome,

I find it difficult with a new build to get the builder and Architect to go that extra mile, with real Insulation, say 500mm in the roof, 200mm insulation blocks in the walls with 90mm air gap and insulation batts, double sewage system, grey water recovery, air lock type entrance doors etc etc.

Have a look at Passivhaus standards and see what you can incorporate.

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Everything is possible, just give me TIME.
mikrt
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« Reply #3 on: October 05, 2012, 08:54:12 AM »

Thanks for replies,

UFH will be wet type, in "wet screed" type concrete floor, which can be thinner than normal screed.

The smallest boiler size I can find is 14Kw, with the next nearest being 20Kw, so to prevent it over-modulating (not reccommended), is the buffer tank size suggested large enough? The boiler will be in utility room.

Also, my energy assessor has suggested that I will not require any heating upstairs at all, do you think he's being over-optimistic, or is it possible (will have electric towel rails in bathrooms). I'm tempted to lay flow/return pipes to rooms just in case we do find it cold over the winter, then option is there to fit rad's.

Thanks again, Mike.


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dhaslam
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« Reply #4 on: October 05, 2012, 10:11:34 AM »

In a well insulated  house passive heat  becomes much more important.    Rooms with south facing windows and with appliances like TVs  will be naturally warm but in comparison bathrooms  are  freezing, specially if north facing.   

Solar panels can produce  low temperature heat for  underfloor heating   very  efficiently during the heating season but  not every day.  They need to be coupled to long term storage  like an underground insulated water tank that can store summer  heat to make up for days without sun.   
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A.L.
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« Reply #5 on: October 05, 2012, 10:19:20 AM »

hello again,

The 50 litres per kw of boiler output is where you are attempting to store energy for later use, if you have say a 150mm concrete slab in thermal contact with the screed, i.e. insulation below slab, it becomes your buffer. How small the 'liquid intermediate buffer' could be in this case I had better leave to those who know - biomass is not really my thing.

Quote
my energy assessor has suggested that I will not require any heating upstairs at all, do you think he's being over-optimistic
- if you build to better than minimum building regs standards then you can do without upstairs heating, at building regs standards it might depend on your heating pattern, building thermal mass and personal preferences. Fitting flow/return pipes would not be costly and any eventual radiators would be small (500w)
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russ_fae_fyvie
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« Reply #6 on: October 05, 2012, 02:28:30 PM »

New build.....

Ah, I remember it well  !!

Most regulars on here will know our house inside out by now !

I won't go over everything, if you want to check out the intimate details of the build check out our Blog www.russquinlan.co.uk which is always worth a laugh !

Thing we didn't do, due to bad advice, was install a buffer tank, we have a 9kw Pellet Boiler and for our house it is plenty. We have UFH in thin screed too but nothing upstairs except for a single radiator plumbed off the UFH system (if you see our house plan you'll realise why no heating upstairs.

If I was ever to go through this again, (and I WON'T !!) just make sure you get sound advice from local tradesmen you can trust Advice from here is always a good starting point and also along the way, but you do need people installing the kit who know what they are doing and who you can trust. We promised all sorts from a few people but ended up sacking the plumber, sparky and the Pellet Boiler supplier !

I always start twitching when I think back !!

Good luck !!

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« Last Edit: October 05, 2012, 02:31:17 PM by russ_fae_fyvie » Logged

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offthegridandy
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« Reply #7 on: October 06, 2012, 11:24:49 AM »

Also, my energy assessor has suggested that I will not require any heating upstairs at all, do you think he's being over-optimistic, or is it possible (will have electric towel rails in bathrooms). I'm tempted to lay flow/return pipes to rooms just in case we do find it cold over the winter, then option is there to fit rad's.


IMO the answer to this depends on the lay out of the upper storey. For heat to effectively travel around the upper storey and into the rooms it needs to be able to get into and out of the rooms. If you simply have a landing with doors of, the landing will be warm and rooms less so.  We have open light wells from top of house (barn) to GF and heat circulates  v well.  Use towel rails in bathrooms as part of "heat dump" from boiler. Rails are always warm when boiler is running and keps bathrooms warm and dry.

We do have v small rads in 1st froor bedrooms.  Not really needed  but makes getting up ion morning so much nicer.  I'd say put in plumbing art 1st fix, then your covered if you need it.

And to echo Clockman,  don't settle for anything less than the maximum insulation you can fit in.  Its cheaper than buying energy later.  If your budget looks tight skip the fancy kitchen units you can add them later unlike insulation.

Good luck.

Andy
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« Reply #8 on: October 06, 2012, 01:53:41 PM »

Also, my energy assessor has suggested that I will not require any heating upstairs at all, do you think he's being over-optimistic, or is it possible

We're a little bit further down the line than you (though still not habitable)... but size and heating sound similar.

we're also going for UFH downstairs and towel rails in bathrooms but no other heating upstairs.  In our case I've designed the ducting route for the MVHR so that we can retro-fit some heating batteries to the ducting if the 1st floor turns out to need a little bit of a heating top-up.  We've used open-web joists, so if all else fails it won't be too hard to retro-fit a small radiator in each bedroom.

Good luck!



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