Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: Smirker on November 24, 2012, 08:23:00 PM



Title: Advice on Self Build
Post by: Smirker on November 24, 2012, 08:23:00 PM
Hi All,

We are about to embark on a self build and are getting bogged down as to whether we should go down the heat pump route (Earth Save ASHP for UFH and Ecocent for DHW) or if we should stick to installing an efficient boiler to run UFH and provide adequate hot water? We intend to insulate to 0.15U Value or below with triple glazing and be as air tight as possible.

I realise that the capital outlay will outweigh the savings that we will get in the short term but we are willing to invest for the future as gas/electric prices are only going to increase.
 
We intend to install some form of solar tech (PV only or PVT if the budget will stretch) which will provide some of the DHW/electricity.

Really finding all the conflicting opinions confusing and we obviously want to make the right decision.

Does anyone have any views on the Genvex Combi as well as Earth Save Products integrated systems?

Thanks,

Jim


Title: Re: Advice on Self Build
Post by: desperate on November 24, 2012, 08:53:19 PM
Hallo Smirker welcome, speaking as a non HP expert........

If you have mains gas available it will undoubtedly be the cheapest option for the short term at least, although not necessarily the lowest carbon option, you will be exposed to future gas price increases with no options.
If you go down the HP route you will more than likely need a small amount of back-up particularly for the hot water, but it does future proof your heating against those price increases, of course electricity is going to increase as well but if you can generate some of your own with PV that will help out.

My gut feeling..........with your UFH, good insulation levels and glazing, go HP route.

Desp


Title: Re: Advice on Self Build
Post by: Smirker on November 24, 2012, 09:14:35 PM
Thanks for the reply,

A bit of a headache trying to decide what to do for the best facepalm. We would like to use some renewable tech but not if it is going to cost a fortune. A compromise has to be reached and we will prioritise insulation/airtightness so space heating demand should not be huge. DHW is a different matter. 2 adults and three growing children so the demand will be high. Best to spec a 250l Ecocent or gas boiler maybe in addition to solar thermal?


Title: Re: Advice on Self Build
Post by: Richard Owen on November 24, 2012, 09:21:39 PM
I'd make a thermal store with lots of tappings, the heart of the system.

Then, if your chosen technology doesn't quite deliver, it isn't going to be a major drama to add something else.




Title: Re: Advice on Self Build
Post by: Smirker on November 24, 2012, 09:44:42 PM
Ok, an interesting take. A thermal store would be a good option as we are thinking of some solar thermal as one of the inputs which could then be supplemented by an efficient condensing boiler.

Our friends who self built a few years ago went down this route and are happy with the results. Our only issue might be space for the tank.


Title: Re: Advice on Self Build
Post by: dhaslam on November 24, 2012, 09:54:15 PM
If you are getting an air source heat pump you should  buy a  good  reliable make.    The more expensive ones have a larger air throughput  that allows them  to work down to about -15C  and at more normal temperatures they can still produce quite a lot of heat.    With care you can top up DHW  with an immersion  for the last 10C which saves running the heat pump at excessive temperatures.    I don't see how the Ecocent can add anything because it means either cooling the house or bringing in outside cold air  which would be duplicating the main heat pump.  There is a small  net gain by condensing  moisture from the air in the house but a modern house won't have  high humidity.   An ASHP running cost can be very low  if off peak electricity is used.    When building you should allow  sufficient space  in the centre of the house for a good big   thermal store.  If it is centrally located any heat loss  will be retained in the house.     It can be used to even out   solar gain over a few days  as well as to allow flexible running times for a heat pump.    As Richard says a heat store allows other heat sources to be added.        


Title: Re: Advice on Self Build
Post by: brackwell on November 25, 2012, 09:27:16 AM
Comparing running costs between gas and heat pump then there is very little in it but soon you will be able to get RHI for a GSHP (the ashp is still in the air) and this will then make the GSHP a no brainer. The fitting cost on a new build when the JCB is already there etc makes this cost effective. Always assuming you have the space.

The thing you should really consider are passive solar heating of the building along with significant internal thermal mass in order to provide stable internal temps and reduce overheating in summer.

Ken


Title: Re: Advice on Self Build
Post by: Smirker on November 25, 2012, 03:14:18 PM
Thanks for the input. It shows how little I know about all this stuff, I had not considered thermal mass etc.

To address the points made in the last two posts; GSHP we had pretty much ruled out as we only have a narrow but fairly long plot 9.5x45m approx and did not think we would have enough room to lay the pipe work. A good point is made about the Ecocent unit in that it will drain heat from the building in order to provide DHW. It would seem then that a better route might be to install a thermal store with several inputs, we will need therefore to look at our plans to see where we could site one as I have seen how big they are plus we will need a place for UFH manifolds etc.

Is GSHP feasible in the allotted space we have? In which case this could be used to run UFH and hot water to an extent.

Passive solar heating will play a part as we have significant south facing glazing incorporated into the design.

Views on whether it's worthwhile to install solar thermal?

Does anyone have a view on the Genvex Combi, a good investment or not?

Thanks to everyone who has given advice, it's good to hear the views of people who are not necesarily selling something.


Title: Re: Advice on Self Build
Post by: bornagain on November 25, 2012, 04:36:36 PM
Hi,

Please find my two-pennies worth....

We completed our new build in Oct 2011, its around 190m2

It is built of ICF and has similar spec as your proposed house.   Walls U=0.15, floor <0.1, roof <0.1

We have solar thermal with quite a large Thermal Store. 500L

We have no heating at all upstairs and UFH  downstairs.

All the internal walls are blockwork, the ground floor is;- 300mm EPS: 100mm concrete: around 110mm of screed.   The UFH pipes sit on the concrete. The first floor is beam and block with screed on top.  This all adds upto loads of Thermal Mass.

The windows and doors are all 3G, we have a lot of glass facing south.

Vent Axia Sentinel Plus MVHR unit.

There is a small room sealed woodburner in the living room which has a back boiler that thermosyphons into the Thermal Store .   The woodburner does not get lit very often (ie hardly ever), but it is really lovely to light it on a cold winter evening.

We have PV that has generated around 3600 kWHr but I think the overwhelming majority of this has gone back into the grid - the Yorkshireman in me fancies an Immersun - but I think that the right thing to do is to export as much as possible.

The Thermal store is heated by the Solar Thermal, the backboiler and by a couple of Economy 7, 3 kW Immersion heaters.

We have no oil or gas, and our total fuel bill (if we ignore a little bit of timber) is around 670/yr (circa 7500 kWHrs)

PV is yielding around 1700, so we have a net energy bill of around -1000/yr.

We could have used less energy, but my wife likes the house warm 21 C.

I am an Engineer and I tried really hard to convince myself that we could do with an Air or Ground Source Heat Pump - but no matter how I did the calcs, it just didn't pay.  In retrospect, I was correct.   Spend your money on insulation.

Let us all know how you get on...

Regards

P.


Title: Re: Advice on Self Build
Post by: Smirker on November 25, 2012, 09:02:45 PM
Great concise response, thanks :genuflect The more I read the more it becomes apparent that we will be best to insulate to a high level and go down the solar thermal/thermal store backed up by a gas boiler (we have mains gas available). We too will be installing UFH downstairs. My only fear is that we wont have that much thermal mass in our building, being a timber frame. We have to minimise our wall thickness as it is a narrow site. The overall dimensions are the same (190msq), I am looking forward to the reduced energy bills from a better level of insulation and the feed-in from the solar.

The rational is that with a thermal store we can always add a ASHP at a later date if gas prices sky rocket. It makes no sense to bypass gas but run a heat pump with expensive electricity.

Are you happy with the MVHR unit you installed?

How does your UFH run out of interest; from the thermal store? I am lucky in that my wife likes it a bit more freeeze so our heating bills should be less so should be quids in. :hysteria


Title: Re: Advice on Self Build
Post by: acresswell on November 25, 2012, 09:33:25 PM
You may not be able to put much thermal mass in your walls, but don't forget that you can add thermal mass to the ground floor!


Title: Re: Advice on Self Build
Post by: Smirker on November 25, 2012, 11:46:24 PM
Thanks, will bear that in mind. Block and beam with added insulation so that will provide decent thermal mass in fact. Like the Blog by the way.


Title: Re: Advice on Self Build
Post by: brackwell on November 26, 2012, 10:47:18 AM
Bornagain,

P could you expand your thoughts/calculations a bit further  " I am an Engineer and I tried really hard to convince myself that we could do with an Air or Ground Source Heat Pump - but no matter how I did the calcs, it just didn't pay.  In retrospect, I was correct."    I am an engineer and when i have done calculations of running costs i come out pretty evens.

Ken


Title: Re: Advice on Self Build
Post by: bornagain on November 26, 2012, 06:03:28 PM
Brackwell,

Assume that we use a typical amount of electricity for normal, day to day use   3500   kWHr/yr
                     
All remaining electricity is used for DHW & Heating                  4000   kWHr/yr
                     
Assume a CoP of 4 (which is pretty optimistic)                     
                     
Energy required to drive a heat pump                                  1000   kWHr/y
                     
Actual Energy Required to Drive Immersion Heater                             4000   kWHr/yr
                       
Energy "saved" by Heat Pump                                                      3000   kWHr/yr
                     
This energy is all E7 electricity which costs 5p kWHr and therefore costs                150   /yr
                     
If we Use a CoP of 3, then the saving drops to around 133/yr                     
                     
So, in order to save at most 150/yr I need to buy a heat pump, install it, and then maintain it. Then buy a new one is (say) 15 years.

Feel free to spot the deliberate mistake - but if you can't then I'm sure you will agree that unless E7 electricity gets a lot more expensive, you don't need a heat pump.
                  
Regards

P.


Title: Re: Advice on Self Build
Post by: bornagain on November 26, 2012, 06:12:49 PM
Smirker

The UFH is connected via a 4 port valve installed like the arrangement on the Accumulator Tanks website -goto the downloads page and download the last circuit diagram.

I bought my tank from Accumulator tanks, it appears to be a one man band, but he knows his stuff and gave a bit of support over the phone when I came to pipe it all up.

The solar thermal installation onto two coils seems to work particularly well, although the solar thermal company who installed it took a lot of persuasion - ultimately, Akvatherm are a big European outfit who know what that they are doing.

http://www.accumulatortanks.co.uk/Circuit%20diagram,%20AKVAir%20Solar%20Plus%20range.%20For%20guidance%20only.pdf

good luck

P.



Title: Re: Advice on Self Build
Post by: Smirker 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?


Title: Re: Advice on Self Build
Post by: brackwell 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


Title: Re: Advice on Self Build
Post by: bornagain 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.


Title: Re: Advice on Self Build
Post by: Smirker 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 exhappy:


Title: Re: Advice on Self Build
Post by: desperate 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


Title: Re: Advice on Self Build
Post by: dullnote 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


Title: Re: Advice on Self Build
Post by: charlieb 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!)


Title: Re: Advice on Self Build
Post by: Les101 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


Title: Re: Advice on Self Build
Post by: dullnote 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


Title: Re: Advice on Self Build
Post by: Smirker on January 29, 2013, 03:52:13 PM
Thanks to all for keeping the thread alive exhappy: 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?


Title: Re: Advice on Self Build
Post by: titan 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.


Title: Re: Advice on Self Build
Post by: Smirker 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.


Title: Re: Advice on Self Build
Post by: dhaslam 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.    


Title: Re: Advice on Self Build
Post by: Smirker 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.


Title: Re: Advice on Self Build
Post by: A.L. 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



Title: Re: Advice on Self Build
Post by: Smirker on January 29, 2013, 07:02:08 PM
Hi A.L,

175mm of rigid PUR insulation, not fibre wool (140mm in stud + extra layer to the interior) we have been told should achieve 0.15.

Airtightness we are aiming for <1 so three is the worst case scenario. I am accutely aware that we need to focus on "fabric first" as a means to reduce energy consumption and therefore cost.

Perhaps we should try to increase the insulation in the walls further to 200mm?


Title: Re: Advice on Self Build
Post by: A.L. on January 29, 2013, 08:05:15 PM
hello again,

using lambda 0.025 for PUR (more realistic than sometimes quoted 0.022) gives U=0.171 (105mm brick, 50mm unventilated cavity, 12mm OSB, 140mm TF+PUR, 35mmPUR,12mm plasterboard, 2mm skim coat) assumes 15% timber fraction as BRE recommendation

200mm PUR (extra 25mm) gives U=0.144

250mm PUR (extra 75mm) gives U=0.111


Title: Re: Advice on Self Build
Post by: Smirker on January 29, 2013, 08:29:55 PM
Thanks for the calcs A.L. :genuflect

We are not going brick skin but render (might be able to use a self-coloured/ insulated one?) We have a juggling act of trying to maximise insulation but not making the walls too thick. The plot is only 9.45m wide but 45m long. With 1m between boundaries each side the width of the house is only 7.5m. we want to maximise insulation without unduly affecting internal space. Our friends self built with timber frame and their walls are 450mm thick! Not an option for us.

Would upgrading to higher spec insulation (PIR) help in this regard? I think over 200mm of insulation and the walls will start to become too thick.

Thanks for everyone's help thus far, we really want to get this right first time.


Title: Re: Advice on Self Build
Post by: Sean on January 29, 2013, 08:45:53 PM
have you considered a proper multi-foil ?

there's a somewhat rambling thread on the GBF relating

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=125&page=1&Focus=44665



Title: Re: Advice on Self Build
Post by: Smirker on January 29, 2013, 08:52:25 PM
Cheers Sean, will take a look. My understanding of multifoils is that they are not all they're cracked up to be but that opinion could be wrong!


Title: Re: Advice on Self Build
Post by: A.L. on January 30, 2013, 08:30:05 PM
hello again,

Cheers Sean, will take a look. My understanding of multifoils is that they are not all they're cracked up to be but that opinion could be wrong!

- thats my understanding to,

tri-iso super 9, claimed to be equivalent of 200mm fibreglass may only be as effective as 75mm -www.planningportal.gov.uk/uploads/br/multi-foil-insulation_july2005.pdf (http://www.planningportal.gov.uk/uploads/br/multi-foil-insulation_july2005.pdf)

given that it requires a 25mm gap on both sides it is really 75mm thick,

at around 11 per m2 it may be a bit dear


using render will reduce the 200mm wall u-value from 0.144 to 0.151, effect of any 'insulating' render is insignificant

substituting PIR at lambda 0.022 gives U=0.136 from 0.151

I understand that 89mm timber frames are structurally adequate, 140mm was largely introduced to accomodate extra insulation!

reducing the frame to 89mm but leaving 200mm of PIR gives U=0.122

my concern with rigid insulation is fitting into the timber frame in an airtight manner, perhaps consider a sprayed polyurethane like Walltite from BASF


Title: Re: Advice on Self Build
Post by: Sean on January 30, 2013, 09:27:57 PM
tri-iso super 9, claimed to be equivalent of 200mm fibreglass may only be as effective as 75mm -www.planningportal.gov.uk/uploads/br/multi-foil-insulation_july2005.pdf (http://www.planningportal.gov.uk/uploads/br/multi-foil-insulation_july2005.pdf)

your understanding is sadly flawed, clearly you are not aware that the report you have used to form your opinion was based on test results taken from sites where the installation methodology was shown to be incorrect



Title: Re: Advice on Self Build
Post by: Richard Owen on January 31, 2013, 06:42:47 AM


my concern with rigid insulation is fitting into the timber frame in an airtight manner, perhaps consider a sprayed polyurethane like Walltite from BASF



It's not difficult. Either cut the boards tight and friction fit or cut them loose and seal them in with spray foam.

Foil tape all the joins and the job's a good 'un.

Running a layer of insulation over the top of everything (need only be 25mm) helps as well.


Title: Re: Advice on Self Build
Post by: titan on January 31, 2013, 09:12:17 AM
I don't know where the building will be situated but if noise is a potential issue ( traffic, aircraft, wind, neighbours  etc )   PU has virtually no sound deadening qualities.


Title: Re: Advice on Self Build
Post by: Smirker on January 31, 2013, 11:27:51 AM
Thanks, good points raised here. Re the frame, it is being built by English Bros who cut the insulation with a laser saw then shoehorn it into the frame. I think 140mm stud is their "standard" but it might be worth asking about 89mm and increasing insulation as suggested. The reduced wood cost compensating for the additional insulation. So render actually worsens the U-value (albeit by an insignificant amount)? would not have thought that. We are planning on filling the frame than adding 50 or 60 mm of extra insulation and having watched the Denby Dale stuff on Youtube will be placing emphasis on junctures to avoid cold bridging etc. I will be happy if we get air tightness to <1.

Sound insulation not too much of an issue as we are not on a main road and back onto fields. we plan on using Fermacell rather than plasterboard in the interior. The Architect (my Father-in-Law) is dubious about the amount of heating we will require and wants us to put some heating in bedrooms which I think will prove unnecessary. Still pondering over Ecocent plus boiler for UFH or thermal store+solar thermal. Decisions, decisions.