Guidance on New Build

afrofish

Hello everyone,

My wife & I have just received planning permission for a 2-storey 3000 sq-ft house in county Cavan. We are now trying to decide on what systems to use for the build and the services inside the house.

I apologise in advance for cramming all of these issues into one post but I believe it is important to consider them holistically. For example a change to the central heating boiler may affect the hot water, just as a change to the building structure may impact on the efficiency of the MHRV and so on. (if the mods aren't happy let me know and I'll try to break it down).

We are hoping to make a relatively efficient house through high levels of insulation and application of some of the passiv-haus concepts. Having said that comfort (and affordability) are far more important than adhering to a standard. The house is for us to live in (permanently) so resale is not important.

There are some things we have decided on which may/will affect other areas of the build. I will list them below as they may help you understand other decisions:

• We are going to use underfloor heating,
  (I believe it will lead to a more comfortable home and I hope the lower temperature required will reduce the heating costs).
• We are going to use concrete floors upstairs and downstairs
  (as their rigidity works well with underfloor heating and wet-rooms and they don't transmit sound).
• there will be 2 stoves in the house (one solid, other not determined)
  (Stoves instead of open fires as they can be fed from an external air source [MHRV] and the ability to use Solid fuel seems sensible in the countryside).
• we are going to fit sash windows at the front of the house
  (because they look nice.. what do you mean they aren't efficient!)
• We are going to fit MHRV
  (It just makes sense, recover the heat from stale air before exhausting it. One proviso I have taken from the forums is to make sure it is done properly!)
• some of the bathrooms will be wetrooms (upstairs)
  (When I have used wet-rooms in the past I loved them, after all this is my dream home.)
• I want to have a power shower in the main bathroom.
  (See previous..)

Construction Method:

The first thing we need to decide on is how to build the house. Cavity wall, Insulating Concrete Form or something else entirely? Originally the architect drew the plans assuming a standard cavity but after recently hearing about ICF houses I am now wondering if they might be a better solution. Does anyone have any experience of them, what are their good and bad points? One thing that does concern me is that the elements will only be kept out by one wall, is there any possibility of damp penetrating over the years?

If we did decide to build a cavity-walled house the architect recommends not straying outside of a 110mm cavity as at this point you need an engineer to certify the structural integrity of the wall. How much insulation does 100mm give you? Would you fill the cavity with foam beads or use insulation boards?

Once we have decided on how to build the house we then need to decide on how we will service the house.

Electricity:

The house will be initially supplied by the ESB but since the house is slap-bang in the middle of a windfarm (and on a hill), I am looking to upgrade to a small wind turbine to provide power for the house (once the funds have recovered from the initial build). With this in mind, the additional cost of electrical services (over gas, oil etc) can be partially offset against the possibility of free energy in the future.

My only concern about this plan is that the nearest Aertricity turbine is approx 300m from the house and some of the neighbours seem to think we will not be allowed our own residential turbine as a result. Does anyone know if there is any accuracy in this?

Heating:

There are two elements to this section, room heating and water heating.

As mentioned previously we intend to use underfloor central heating throughout the house. The initial plan is to go with water underfloor heating but if the turbine became a reality electric underfloor may be viable (even sensible).

If we assume water based underfloor heating for the time being we then need to decide the heating method. (I should mention that we are in the countryside so we do not have a gas supply). I was originally thinking of an oil powered condensing combi boiler as it is simple, cheap and relatively efficient. My concern with this approach is twofold: Firstly it would not benefit from the turbine and secondly the cost of oil will continue to rise year on year. It is beginning to appear a cheap initial install but an expensive long-term option. I have come to the conclusion that solar is a great top-up option but not a heating method you can rely on in it's own right (also not sure if it would/should be used for HW,CH or both). I am also considering Ground source and Air2Water heatpumps as they would both be efficient and benefit from the free electricity in the future but they are expensive. (As you can see a lot rests on whether the turbine is viable). I have discounted log and pellet furnaces as we would have to purchase the vast majority of the fuel and I think they really come into their own if you can supply your own. Any suggestions or recommendations?

This then leaves the question of how we heat the hot water. I have read that modern (high-power) combi's are able to supply a sufficient feed of hot water to supply a power shower but I have no first-hand experience. How would the heat-pumps fare? I have heard of people who use a 300ltr tank in the loft-space which is heated by a combination of solar,CH and sometimes nightsaver electric. Would 300ltrs be enough for the power shower?

Apologies again for the length and scope of this post but I couldn't figure out how to split it without losing the relevance.

Regards, Afro.

beyondpassive

You Might have difficulty with your proposed turbine due to turbulance, are you upwind of the farm?, will they have difficulty with you? Even with >8m/s av wind speeds, you'll have difficulty making the investment in wind stack up. Are you planning on investing a couple of million for a 60 meter diameter Vestas?

I'd advocate the principle of eco-minimalism over eco-bling. Before you spend a fortune bolting on capital expensive renewable technologies with long payback, work out what your optimum level of fabric improvement should be. In any cost benifit analysis there is an equilibrium point. For a 3000 sq footer on a Cavan Hill. Its proberbly u- value walls 0.17, Roof 0.16, floor with underfloor 0.13 with a cold bridging psi of 0.04, Air tightness under 2 ACH@50pa. Then heat it with Stove+solar +electricity buffered in 2000l heat bank cyclinder. Or just solar and oil boiler. I'm only advocating solar because its mandatory for compliance under part L 2008.
The biggest issue for your build will be reducing cold bridges. For instance Its nonsence to build ICF on standard rising walls. I wont go into cold bridge detailing now, but with underfloor you need to consider it. Your wall build can be 220 full fill, no probs there I've done 4 so far, you'll have a site engineer on board anyway, and the wall tie calcs take 5 minutes to verify. Alternativly you could use 150-200 external insulation on 150 quinnlite, i'd prefer this to ICF, the inner polystyrene isnt effective. The standard cavity wall is past tense, it dosent work. PIR insulation, cold bridging at rising wall and eaves, cold spots in corner bedrooms, drylining walls while avoiding wall floor junctions, lots of problems. Move on. Model your build in the PHPP planning package, that will give your decisions some clarity.

Sash windows look nice, and they have advanced quite a bit in the last 300 years since they were invented, and are very pleasing aestetically, so hang one on the wall by all means, but they really don't have any place in contemporary dwellings. That said planners without any design training often stipulate in conditions that houses must have twee little cottagey features. Simple clean high performance windows can look great and won't go out of fashion. Sash windows might be the pine country kitchen's of the next decade. Choose neutral external features, just like the little black dress or black two button suit, it'll never go out of fashion. afrofish Enjoy the build, no regrets eh!

afrofish

Thanks for the reply Beyond Passive,

I need to go away and do some homework (to figure out what it all means) but my initial thoughts are as follows:

I am estimating that a small wind turbine would cost €15K (approx) and that would supply all the power for the home (when there was wind - which round here is 90% of the time). If I were to install GSHP/ASHP with underfloor heating the only input is electricity and I would effectively reduce my heating and electricity bills by 90%. That means I could be paying less than €200 in bills per year which has to be a saving of at least €1000 per year. Now that would still mean a 15 year payback (ignoring the Heat Pump outlay). Not the greatest but still better than the payback on a €15000 car! I would also have to factor in maintenance too...

(My figures are off the top of my head and I have no idea about turbulence)

If my turbine cost is way out or the turbine would not power the house please feel free to burst my bubble. Sometimes I need a good dose of reality!

I totally take your point about eco-bling but the promise of self sufficiency is so alluring!

sinnerboy

Get the fabric of the house and ventilation strategy right and you drastically cut the complexity of how to heat it .

If fully implemented in design the Passiv House (PH) approach will eliminate the need for a conventional heating system

But you have planning already and you want to use sash windows - PH standard may not be easily realisable now .. but so even so you can still , with careful and expert input now from a professional , expect to need no more than a modest heating system . Perhaps a condensing oil boiler may suffice or a wood pellet boiler which will reflect well on the CO2 part of you BER cert . ( Side issue - my own opinion is that folks will pay more attention to this when CO2 taxation is expanded )

So where to start ? - at the bottom . If you build an insulated raft foundation
( google it ) you can eliminate cold bridges between wall and ground floor . Moving onto the walls - the construction method that lends itself most easily to detailing out other cold bridges is rendered external insulation on solid blockwork .

ICF works fine but if you are really concerned about damp penetration you could build it "timber frame style" by that I mean construct the ICF wall and the a block / brick skin over to achieve the psychological comfort of a cavity . Expensive mind you to do that . Single skin ICF does work .

You have indicated concrete upper floors which imlpies
1. You need a consultant engineer
2. Timber frame is ruled out ( yes its is possible but you complicate things )

It is possible to obtain very efficient sash windows - I will post a link another time .

MVHR is a good idea - combined with very high air tightness way above min b regs . Keep that heat in .

B Regs compel you to provide renewables . So Solar Thermal for hot water for Summer . A Wood Pellet boiler ( for Winter hot water and space heating ) in winter should take care of this . Or condensing oil boiler and make both your stoves wood would also help get you there .

I can not speak with any great expertise on wind turbines .

sinnerboy

Be aware that if you build with so much concrete - all ext walls and floors ( many if not all of your internal ground floor level internal walls will also be concrete to support the first floor ) that the building will have a high thermal mass - it will heat up and cool down slowly .

If your lifestyle is such that you are out of the house a lot - this may not suit you . A thermally massive building works best with constant low level heat .

Windows

Forum rules forbid the naming of individual companies - but I am sure you find what you need by searching here

http://www.bfrc.org/Consumer/search.aspx

sinnerboy

Get a BER assessment done now . You have to have a BER Cert published before occupation ( by law ) anyway but a pre build assessment can be used to make informed specification choices now .

If your architect is not trained to use DEAP ( Dwelling energy Assessment Procedure ) the software used to prepare BER Assessments ( and verify compliance with b regs Part L ) then appoint a BER assessor ( one who is/was an architect or architectural technician ) to work with your architect .

Expect to pay more than the standard €200~300 for this but no more than €500~600 ( depending on to-ing/fro-ing ) . It will be a smart investment

Also appoint , before works , an air tightness tester who can also advise before and during the build so that when the actual test is done - you realise the desired result without pulling back finishes and fittings to seal faults .
Look for someone who can

1. Advise on the details tender drawings before they are issued for pricing
2. Give a site presentation to the site workers - especially the plumbers and sparks . Get then all "on board" from the start
3. Inspect the works when roof is on and tiled and windows are in BUT before plastering starts . A pre-test test is a most effective snagging procedure
4. Finally the test - with glowing result

Budget €900~1000 . Smart spend .

imitation

Good luck with yourself build, I`m on the same road myself, albeit a small bit further along, I`m going to cherry pick questions as I dont know all the answers. I`ll also apologise in advance for my hand waving answers, I dont have the maths at my finger tips.

afrofish wrote: »

• We are going to use underfloor heating,
  (I believe it will lead to a more comfortable home and I hope the lower temperature required will reduce the heating costs).
• We are going to use concrete floors upstairs and downstairs
  (as their rigidity works well with underfloor heating and wet-rooms and they don't transmit sound).
• we are going to fit sash windows at the front of the house
  (because they look nice.. what do you mean they aren't efficient!)
• We are going to fit MHRV
  (It just makes sense, recover the heat from stale air before exhausting it. One proviso I have taken from the forums is to make sure it is done properly!)

Underfloor heating is a good choice if somebody is in the house all day (or simply if you enjoy the comfort of it), as your effectively using the house floor and internal walls as one big radiator. This has some effects that are worth noting, it takes a significant amount of time to heat a room, and also for that room to cool. That means you`ll want to pay close attention to your heating controls so you can fine tune them keep temperatures comfortable.

On MHRV, the most crucial aspect to the success of this is airtightness, in a sealed system it is very efficient, but this drops off rapidly the less air tight the house is. When your putting your specs in make sure you tie down everybody with the stipulation that the house will be air tight. Its no good for your builder to be going to great lengths to seal his gaps if the plumber is drilling holes all over the place. 3 meters cubed per square meter per hour is the usual target for air tightness.

Sash windows can be used in an airtight house, I have seen it, but the person involved had a lot of trouble getting the windows to seal properly. Personally I wouldnt touch them with a barge pole considering that and the cost (and the fact I think they dont belong on a contemporary house).

If we did decide to build a cavity-walled house the architect recommends not straying outside of a 110mm cavity as at this point you need an engineer to certify the structural integrity of the wall. How much insulation does 100mm give you? Would you fill the cavity with foam beads or use insulation boards?

I`ll give my own build as example, it has a 150mm Cavity, with full fill cavity insulation + 50mm dry lining it will (hopefully) be able to achieve an A3 rating. Of course the whole house is rated, so thats just a very rough indication.

Insulation boards VS full fill has a bit of debate going for it. The main thing most people have against full fill is the fear of moisture getting through the cavity, which most people feel isnt likely to happen. ( My own engineer has recommended it). On the other hand insulation boards need to be installed correctly and the cavity needs to be kept clear, if a shoddy job is done here you`ll have poor insulation AND possible moisture trouble. Its alot easier to just pump the cavity. Personally I dont trust full fill, moisture bridging the gap doesn't seem to be a common complaint, but I feel in 20 years time it could be a different situation, and none of the people recommending it will be anywhere to be found if it does transpire.

Electricity:

The house will be initially supplied by the ESB but since the house is slap-bang in the middle of a windfarm (and on a hill), I am looking to upgrade to a small wind turbine to provide power for the house (once the funds have recovered from the initial build). With this in mind, the additional cost of electrical services (over gas, oil etc) can be partially offset against the possibility of free energy in the future.

I think the payback time for a wind turbine on average is like 10 years, maybe more. My feeling is the money would be better in a deposit account, as after 10 years it could be clapped out and in need of replacement or repair. Dont forget there is more of difference between a domestic turbine and a big commerical turbine than just size. Commerical turbines are high enough to sit in a nice strong clean air stream, where a domestic turbine is usually so low that it is in turbulent air (generated by trees / houses / hills etc)

My feeling is that PV solar cells could be the energy generation system of choice in the future (considering how far semiconductors have come along), they just need the development. I`ll be going with solar water heaters to meet the regs for the meanwhile.

Heating:
There are two elements to this section, room heating and water heating.

As mentioned previously we intend to use underfloor central heating throughout the house. The initial plan is to go with water underfloor heating but if the turbine became a reality electric underfloor may be viable (even sensible).

I don't think electric underfloor would ever be as efficient as using a Heat pump system.

If we assume water based underfloor heating for the time being we then need to decide the heating method. (I should mention that we are in the countryside so we do not have a gas supply).
.

As far as I know geothermal is well suited to UFH, as doesn't heat as much as a oil boiler, in fact they pretty much go hand in hand as most of the reports I have heard are that its not that great with radiators.

I have also heard reports that UFH can be expensive to run off oil, I`m guessing because the system is running constantly ? Not too sure on this one really.

Leadership

We had the same thoughts 12 months ago and many of same choices for our build. In many respects our homes are similar.

http://grianan.blogspot.com/

In the end we went with the following spec from your list:

• ICF - Reward system. It was a no brainer for us as it has good insulation inside and out and its air tight with the benifit of a quick build.
• Concrete 1st floor and stairs. Again a no brainer especially with kids as you can have dance party upstairs and not be bothered by any noise.
• MHRV - Sealed home so no brainer
• 2 stoves, 1 with a modern backboiler attached to a thermal store and the other is a fancy inset stove for the formal room
• Solar
• Radiators - Unless you have underfloor upstairs so the operating temps can be lower all round then oil and and a mixed UFH/rads will burn so much oil.
• Aluclad windows - Look great!

Good luck

afrofish

Argghhhhh, the more I learn, the more I realise I need to learn.
A little knowledge is certainly a dangerous thing!

Right...here we go.

Fist of all thankyou all for taking the time to reply, I have found your posts very informative and helpful.

I may not cover all the issues below but I will try...

First of all passiv-haus is not achievable at this stage without major redesigns and my wife would be using parts of my body for a necklace if I so much as suggested it! Having said that my aim is to achieve 60-80% of the targets and hence drastically reduce the energy input required....but I will still need input energy.

I don't think PHPP modelling is viable at this stage as I imagine the leadtime is realistically at-least a month.

To explain the reason for the rush a little better, I have an imminent arrival of a baby and we are living in small cottage at the moment. It is cozy enough with the fire on but not so cozy without. Add to this that there are outlying rooms which never get warm and a significant damp problem and you can see why we want to get out as soon as possible. I don't think it will harm the baby but it won't be the most pleasant.

How long does moddeling the house on PHPP take please beyondpassive. I am really up against the wall here as would say I have to start building before March.

I think I am heavilly swayed towards the use of an ICF structure in order to benefit from quick build, airtightness and good (if not amazing) U-values. My concern about damp penetration is still there but it isn't a deal-breaker. Your comments about thermal bridging are concerning. I may have to do some more research into it separately, would the insulated raft stop much?

Thanks for the advice on the insulated raft foundation Sinnerboy, I have researched it but haven't found anything of use. A few pictures but none that really explained what it was. They all seemed to talk about timber frame houses too, could you put concrete on them? It appears to be the same principle as the ICF but for under your feet, and is it not fitted as standard by the ICF Companies?

As to the consultant engineer issue for the concrete upper floors I have an architect who specified them originally (at my request) based on a cavity arrangement. Do I need a separate consultant engineer?

I decided long before I was due to build a house that if I ever did it would have underfloor heating as I just don't like rads or cold floors. The fact that they are more efficient (in principle) is just a bonus. In real terms I think the running costs will be close to the same as a rad system would be due to having it on longer but I can live with that. I plan to put UFH on both floors, (I have heard that oversize radiators can be used upstairs but one of the main advantages of UFH is getting rid of the things, I don't want even bigger ones!)

Solar is a definate as I have to have some sort of eco-friendly option and it seems the easiest (but is it enough). I still don't know what I would heat with it, the water supply or the central heating (or both)?

As to boiler options all the enviro friendly options appear to start at about €8000 and rise from there. Their energy efficiency ratings of 300%+ seem great, but if the fuel used to produce that efficiency (namely electricity) is twice the cost of alternatives it's hard to justify (at the moment). I may have to if my eco cert requires it.

I am also put off by horror stories of ASHP and Wood Burners which are nowhere near as efficient as they should be. I think the way to go if any is GSHP but then it's also the most expensive...sigh.

My current plan is to use an oil powered condensing boiler on a low heat setting to power the UFH because they are cheap and I can always rip it out later and install a Heat Pump option as it will use the same UFH pipes and all the rest of the development would be outside the house.

On to Hot water. I am still clueless on this subject. I am torn between combi boiler (but what happens if I do decide to use a Heat pump further down the line) and a cylinder (but would it be inefficient/ hold enogh water). Some sort of combination of the two seems ideal as that way you could use a smaller cylinder to save fuel and use the combi as a top up if the cylinder ran out....practicalities may be different.

Thanks also for the BFRC link Sinnerboy, once I have decided on the main construction method, windows are my next call.

With regard to the wind Turbine idea. The principle of free (electrical) energy is a very appealing one, especially as it would allow you to be very inefficient in your use of it. Electric underfloor heating would definately be viable and efficient if the electricity was free! Having said that it would not happen for atleast five years after finishing the build (prob more). For that reason I think I am going to work on the assumption that it will never happen as that should make my decisions at this stage much easier.

Right, that turned into another marathon e-mail and I have still missed bits! Thanks for all the feedback guys and keep it coming.

Regards,

Afro

imitation

afrofish wrote: »

With regard to the wind Turbine idea. The principle of free (electrical) energy is a very appealing one, especially as it would allow you to be very inefficient in your use of it. Electric underfloor heating would definately be viable and efficient if the electricity was free! Having said that it would not

Unless you get the turbine for free its not free electrcity, if you sell the electricity back its roughly a 10 year payback period. You may as well buy the power.

Electric UFH is inefficient compared to a GSHP, why not just use the electricity in that.

Some fast browsing and maths (could be off here !) shows that one electric UFH system is 150w per SQM, and one domestic turbine is 2500w, so you`ll only be able to power 16 sqr meters of electric ufh. Thats if the wind is blowing.

sinnerboy

You will need a structural engineer to prepare detailed design and check it the progress and quality of works on site of the structural elements . Your architect cannot do this .

Insulated raft foundations couple very nicely with ICF . Not all companies offer both systems - this one does
http://www.aerobord.ie/supergrund.html
http://www.aerobord.ie/buildblock.html

This one doesnt
http://www.isoquick.de/en/bauverlauf.html

Untill you appoint a BER assessor you will run in circles as far as building fabric / services / ventilation is concerned.

It would take about a week to have a PHPP assessment prepared

For the sake of the rest of your life do NOT let temporary pressures cause you rush anything and risk making bad decisions . Build in haste , repent at leisure !

.

lynchysparks

hi afrofish
welcome to the wounderfull world of house or home building here my two cents worth

firstly you will never finish in the the time you expect or for the cost you expect so be prepared for dissapointment

now insulation insulation insulation you can never have enough under the floor in the cavitys on the walls ceilings roof attic everwhere insulate insulate only use kingspan or ballytherm boards (both made in cavvaan) if you can build the thermal envelope of the house with the highest u value you can you will reduce you heating load .get good windows with high perfomance units kells windows or gradys in mayo both exelent there are lots out there. build air tight or as tight as you can as for heat recovery get someone good to do it see to many systems that didnt work due to poor desgin and installtion or to noisey when running.
icf are fine but unless you or builder have used them before the learning curve is steep there is a few issues with them holding up concrete floors also plastering is very important to stop damp penatration . consider changing you roof to a hot roof construction like pasive house idea its a huge help to airtightness and a better thermal envlope. my susgestion is concrete block cavity construction pump the cavitys with silver beeds and use insutaled plaster board stuck to wall inside 50mm min and hot roof construction some other will dissagree but its a very cost effective way of building well insulated house
now electric under floor heating do not touch it!!!! its only ok for small bathrooms but to for whole house trust me on this
wind turbine unless you get one for free or as big as sean quins not worth the effort pay back to long you talked about a heat pump you would need a masive turbine to run it not practical in a domestic application and no wind no power
heating buy a big buffer tank with three coils slap as many solar panels on the roof as you can afford solar is the way to go for dhw.dont bother with a condising boiler not worth the money buy a bog standard for 600 quid its very hard to get the savings back on the condensing boiler and they cost 4k .heat pump on night rate are brill but beware make shure you buy from a good company lots of have a go plumbers selling h/p and they dont have any back eurotech have a very good system

i have work on house's in cavan with type of construction and heating systems 4000sq foot running costs under a 1000 euro for a year

wish you the best on you house post back on here let us know how you get on

soldsold

Worlds longest sentence!

Breaking it down a bit:

lynchysparks wrote: »

firstly you will never finish in the the time you expect or for the cost you expect so be prepared for dissapointment

Probably very true

lynchysparks wrote: »

insulate only use kingspan or ballytherm boards (both made in cavvaan)

Not good advice, these have there place but long term may not be as good as claimed, arent breathable and might trap moisture. EPS, Rockwool, Fibreglass, Hemp, Cellulose are all breathable to different degrees so in a breathable roof one of these should be chosen.

lynchysparks wrote: »

build air tight or as tight as you can as for heat recovery get someone good to do it see to many systems that didnt work due to poor desgin and installtion or to noisey when running.

Definitely airtightness to a tight level, HRV if you can afford it or get used to purging the house with fresh air for a few minutes twice a day. personally Im going for HRV for air quality and comfort

lynchysparks wrote: »

consider changing you roof to a hot roof construction like pasive house idea its a huge help to airtightness and a better thermal envlope.

Passive houses dont have hot roof constructions usually?

lynchysparks wrote: »

My susgestion is concrete block cavity construction pump the cavitys with silver beeds and use insutaled plaster board stuck to wall inside 50mm min and hot roof construction

Definitely agree with the advice to pump the cavities to stop the wind blowing your heat away, 50mm dry lining will be 38mm insulation with 12mm plasterboard. EPS insulated plasterboard can be got for around 15 euro per board delivered from NI, PU or PIR insulated boards are costly, and its suggested the performance after a few years might not be too different. Hot roof construction (warm room) is expensive, no question. If there is space available and the planners allow it, it will probably be cheaper to build a 2 storey with a cold roof than a bungalow or dormer of the same size floor area. Insulation on the flat can be built up easily with no extra structural cost and no breathability issues, whereas insulation in sloping rafters needs deeper more costly rafters and vapour barriers/ softboard, or similar. thats whats in my roof and Im happy to use the extra space but if on a tight budget a cold roof in a slightly bigger house footprint might make sense.

lynchysparks wrote: »

heating buy a big buffer tank with three coils slap as many solar panels on the roof as you can afford solar is the way to go for dhw.

Solar has a very long payback but for convenience it can make good sense, especially if you use a good bit of hot water. For new builds you need some renewables so solar is a good buy.

lynchysparks wrote: »

dont bother with a condising boiler not worth the money buy a bog standard for 600 quid its very hard to get the savings back on the condensing boiler and they cost 4k .

Dont you have to put in a boiler with 90% plus efficiency in a new house now? Its condensing boilers so.

lynchysparks wrote: »

heat pump on night rate are brill but beware make shure you buy from a good company lots of have a go plumbers selling h/p and they dont have any back eurotech have a very good system

Why go to the expense of an expensive heating system? Eliminate the complexity of expensive heating through designing a simple structure with a small surface to volume ratio, put a lot of effort into making sure you have a continuous band of insulation wrapping the whole house, then add any design features you just have to have and put up with the extra heating load (velux, dormers, etc)

morning delight

afrofish wrote: »

I think I am heavilly swayed towards the use of an ICF structure in order to benefit from quick build, airtightness and good (if not amazing) U-values. My concern about damp penetration is still there but it isn't a deal-breaker. Your comments about thermal bridging are concerning.

Afro

Hi Afro

Sounds like you're under a bit of pressure there! At least when the baby arrives Spring will be here and hopefully the cottage will be a bit warmer.

I'm also currently looking at what system to build and was initially leaning towards ICF. One thing bugged me though. A good few bloggers noted they 'didn't have too many blow-outs' during the pour. Now forgive me if I'm wrong but any blow-out must surely act as a huge thermal bridge. And once a blow-out happens there is no way of reversing it (I don't think you could stop the pour, clear out the blocks and re-sit the blocks).

Another alternative that maybe worth considering is using SIPs (Structurally Insulated Panels). Seems like a great way to get insulation and airtightness guaranteed and quick! Not so sure how they compare on cost though. One rep has told me there is no problems getting a sound proof floor, or pouring screed on it for that matter.

Too many choices, too little time;)

Any way good luck and more importantly good luck with the new arrival!

morning delight

soldsold wrote: »

Worlds longest sentence!

I think Joyce used to write like that as well and there is no way I could get through either Ulysess or lynchysparks reply!:D

beyondpassive

morning delight wrote: »

I think Joyce used to write like that as well and there is no way I could get through either Ulysess or lynchysparks reply!:D

Or quoting Mark Twain, " I hadn't time to write you a short letter, so I wrote you a long one.".


My issue with ICF is that it is built on standard rising walls and the wall plate is not sufficiently closed off. This means that the inner concrete is not fully wrapped with insulation and cannot retain heat. Secondly, suspended concrete floors bridge the inner insulation layer. While the system certainly has its merits and had an improtant role as we transition from standard cavity to near passive spec and cold bridge reduction. It is not as effective as the 3 top options. namely:

1. 220-300 wide cavity with full fill bead and Vartry eng or graphite ties.
2. Structurally insulating breathable timber panel. Renderboard rainscreen.
3. External insulation on AAC block on flat.

morning delight

beyondpassive wrote: »

Or quoting Mark Twain, " I hadn't time to write you a short letter, so I wrote you a long one.".


My issue with ICF is that it is built on standard rising walls and the wall plate is not sufficiently closed off. This means that the inner concrete is not fully wrapped with insulation and cannot retain heat. Secondly, suspended concrete floors bridge the inner insulation layer. While the system certainly has its merits and had an improtant role as we transition from standard cavity to near passive spec and cold bridge reduction. It is not as effective as the 3 top options. namely:

1. 220-300 wide cavity with full fill bead and Vartry eng or graphite ties.
2. Structurally insulating breathable timber panel. Renderboard rainscreen.
3. External insulation on AAC block on flat.

My God aren't we all getting very literate!

I notice none of your perferred options have an external cavity. Being on the West coast I'm been instructed to go with the cavity.

Also the renderboard rainscreen. Is it not v expensive, upto 3 times more expensive than an external layer of standard block and render?!

This building lark is a mine field of choices....

beyondpassive

morning delight wrote: »

My God aren't we all getting very literate!

I notice none of your perferred options have an external cavity. Being on the West coast I'm been instructed to go with the cavity.

Also the renderboard rainscreen. Is it not v expensive, upto 3 times more expensive than an external layer of standard block and render?!

This building lark is a mine field of choices....

A few quotes sprinkled here and there are a good smokescreen for some big holes in my knowledge. As the man said The only thing more expensive than education is ignorance. Its a pain trying to get up to speed with the level of knowledge needed to make informed decisions about building in the current environment especially with whats coming down the line in terms of environmental legislation. Its a pity there isn't a good building research body in Ireland, that could provide answers to the many questions we have, and provide cost effective trainning in techniques needed for modern design and build.

Anyway, The rainscreen is a very definitely a cavity, If using renderpro rather than aquapanel the cost is substantially reduced. The full fill cavity is not a ventilated cavity but will still wick moisture outwards due to vapour pressure.

I agree you need to be very careful about moisture in the West of Ireland where average relative humidity is almost 90%. This rules out a large range of options, however with dynamic hygrothermal modeling, you can assess how any particular single layer (homogeneous) wall build up will perform over a certain period, using site weather data and a range of stress factors.

The biggest issue with moisture in houses in the west of ireland does not come from damp ingress but rather from internal surface condensation, caused no doubt from cold bridging. So I'd rather focus on maintaining continuity of insulation, good flashing and weatherproofing and then use the rule of having materials vapour resistance decrease as you move out through the build up of any homogeneous build up.

irishshadowfax

Greetings all, apologies I've nothing constructive to add to the thread- I just wanted to say thanks to all for the detailed posts, been very helpful so far. I'm at the same stage as you Afro; I have a bit more time on my side to be doing my research, so hopefully, I can contribute soon

Later, Ger

soldsold

beyondpassive wrote: »

The biggest issue with moisture in houses in the west of ireland does not come from damp ingress but rather from internal surface condensation, caused no doubt from cold bridging. So I'd rather focus on maintaining continuity of insulation, good flashing and weatherproofing and then use the rule of having materials vapour resistance decrease as you move out through the build up of any homogeneous build up.

Well summarised. I'll probably use this quote at some point when trying to spread the message of insulation, airtightness and prevention of cold bridging to people I meet that are building their own homes with very poor professional advice and zero research themselves.

I saw a house spec tonight on a tender website where a guy was considering underfloor insulation with 60mm kingspan under the floor and 25mm edge insulation. Seems crazy to me, I spent the last hour draughting an email to him to go through some of the basics of modern (and low cost) techniques to keep heat in, costs down and comfort up.

There is a growing amount of people that are slowly realising they have been conned into building to a low spec (the target being called the building regs, and the result being way off) or buying a low spec house!

creedp

To Soldsold

I was interested to hear you views on people buildling to low spec ostensibly to meet current standards. In my case I will shortly be commencing a self build - 2,800 sq ft. Originally my plan was a 100mm cavity with 50mm insulated drylining with 80mm PIR Kingspan in the ground floor. I will have underfloor heating.

I was advised to go with 150mm cavity and forget the internal insulation as it could cause condensation and also reduce thermal mass. When I asked about upgrading the ground floor insulation to 150mm PIR or EPS I was essentially laughed at by both engineer and builder. They both considered 80mm to be at much as was needed and anyway if I wanted more it would be at the cost of 1st floor ceiling height!

Would another solution here be to build the inner leaf with quinnlite blocks? Would there be any issues associated with building with quinnlite versus std blocks bearing in mind that I'm planning to have conc slabs for 1st floor?

I am also concerned about the cold bridging which will occur with underfloor heating when using std (non-insulated) foundations and only a 25mm perimeter insulating board. Is it possible to have a wider perimeter board if not going with internal insulation? I was told that a way around this is to dry line with 50mm insulaiton board and extend the boards down to the floor insulation before pouring the conc floor. Has anyone else done this and what would you views be on this approach?

I was also looking at the insulated foundation system used by Aeroboard Springvale which seemed to be a very good solution to the cold bridging problem. Has anyone any experience with this option? Is is straightforward to install and could any builder (i.e. one that doesn't seem to want to embrace the concept of high levels of insulation) install it ? Another question here would be whether this option would cost significantly more that going with the traditional approach of with non insulated foundation and rising walls? Is there any other approach that could be taken to reduce the cold bridging problem associated with the cavity build?

I'm sorry for the meandering nature of this message. I am seriously confused at this point with all the issues/options out there and would really appreciate any views/comments.

imitation

Those insulating blocks by a certain billionaire are quite expensive, when I looked into it I believe it came out at twice the price of dry lining. It also requires a different method of plastering, which I believe isnt too commonly done in Ireland, I would be a bit concerned about the finish myself. I dont think there load bearing potential is as great as regular blocks, but thats a question for an engineer.

soldsold

imitation wrote: »

Those insulating blocks by a certain billionaire are quite expensive, when I looked into it I believe it came out at twice the price of dry lining. It also requires a different method of plastering, which I believe isnt too commonly done in Ireland, I would be a bit concerned about the finish myself. I dont think there load bearing potential is as great as regular blocks, but thats a question for an engineer.

The AAC blocks are a touch over twice the price of standard dense blocks, you use 20 per square meter on the flat so this will add around 10 euro per sq meter to the bill, manufacture is in Northern Ireland so VAT might not come into the equation if your blocklayer supplies and fits.

My engineer had no issue with the loadbearing strength of the 5N AAC blocks but this is up to your engineer to calculate or seek guidance from the manufacturer.

The blocks are certainly not liked by plasterers by all accounts, Ive not heard of a different plastering method being used so cant comment on this. I used AAC blocks sparingly around cold bridge areas, the blocks definitely feel warmer than the surrounding dense blocks when touched (before plastering)

soldsold

creedp wrote: »

1. Originally my plan was a 100mm cavity with 50mm insulated drylining with 80mm PIR Kingspan in the ground floor.

2. I will have underfloor heating.

3. I was advised to go with 150mm cavity and forget the internal insulation as it could cause condensation and also reduce thermal mass.

4. When I asked about upgrading the ground floor insulation to 150mm PIR or EPS I was essentially laughed at by both engineer and builder.

5. They both considered 80mm to be at much as was needed and anyway if I wanted more it would be at the cost of 1st floor ceiling height!

6. Would another solution here be to build the inner leaf with quinnlite blocks? Would there be any issues associated with building with quinnlite versus std blocks bearing in mind that I'm planning to have conc slabs for 1st floor?

7. I am also concerned about the cold bridging which will occur with underfloor heating when using std (non-insulated) foundations and only a 25mm perimeter insulating board. Is it possible to have a wider perimeter board if not going with internal insulation? I was told that a way around this is to dry line with 50mm insulaiton board and extend the boards down to the floor insulation before pouring the conc floor. Has anyone else done this and what would you views be on this approach?

8. I was also looking at the insulated foundation system used by Aeroboard Springvale which seemed to be a very good solution to the cold bridging problem. Has anyone any experience with this option? Is is straightforward to install and could any builder (i.e. one that doesn't seem to want to embrace the concept of high levels of insulation) install it ? Another question here would be whether this option would cost significantly more that going with the traditional approach of with non insulated foundation and rising walls? Is there any other approach that could be taken to reduce the cold bridging problem associated with the cavity build?

9. I'm sorry for the meandering nature of this message. I am seriously confused at this point with all the issues/options out there and would really appreciate any views/comments.

Hi,

My views:

1. That sounds like a reasonable spec before you factor in wall ties, gaps behind the insulation boards in the cavity, gaps between the insulation boards in the cavity, bridging of the drylining at the hollowcore and where internal insulation where interior walls meet exterior. Also I was at a house recently where insulated plasterboards were up and the skim coat just done, and there were a lot of draughts coming in through the blockwork at sockets etc.

2. This obviously means your floor insulation is far more critical than normal. Convection brings heat upwards as hot air rises, but any hot surface touching a cold one wont worry if its above or below. You really need to think of this like you think of the hot water tank in the hotpress - 80mm of insulation bonded tightly and no gaps, and the hotpress is still warm from heat escaping. You put 80mm floor insulation down with lots of gaps and the heat will get through. Also PU insulation is not great in a wet environment, and is expensive. The floor is the one place where depth is not an issue unless the foundations/ subfloor are in.

3. Nothing wrong with this idea, except that thermal mass is not all its cracked up to be, it really depends on the usage of the house. Check out the article on thermal mass on constructireland recently (I think), the conclusion was that it doesnt really make a lot of difference to most houses in energy use. Yes it holds heat, but also loses heat through walls leaking heat into foundations etc, also drylining a 150mm cavity should be very safe condensation wise, as the inner leaf wont get too cold, being protected by 150mm insulation

As an exercise I worked out the cost of my 225mm cavity pumped with ecobead, its 77 euro per m2 including sand, cement, DPC, wallties etc etc.

4. Not surprised there, See the attached image of the traditional way to insulate underground heating pipes (from my garage to the house). 4 degree difference in the ground around the pipes, and the ground the pipes was heating up. This is what your builder and engineer want you to build. Some would say get a new builder and engineer, but my take on it was that its my house, this is what I want to build, this is why, and if you want to do it to my spec you get the job. A little education goes a long way. I'll be taking up the heating pipes by the way when the extension is done.

5. Is your subfloor in? If it is, they are right, but maybe a stock brick or soap bar will lift the hollowcore enough to give extra space. I believe there is a tolerance allowed by planners on the overall height (my roofer told me 500mm) but I could well be wrong?

6. Your engineer will need to andwer this, you may need 150mm blocks, or blocks on the flat, the manufacturers told me they recommend 150mm AAC blocks if holding up hollowcore. It also depends on the hollowcore - Will you have a structural screed on top? Is it 6 inch solid or 6 inch hollow or 4 inch solid slab? Its not a problem, just needs to be designed correctly.

7. Yes you can insulate the edges better than 25mm. Beyondpassive was my advisor when I was planning so to be fair I dont want to give away info he has spent time and money working out - I took the idea that getting an analysis done on the insulation/ structure/ return on investment/ heat load calculations that a PHPP analysis would give was going to be good value for money, and I think it definitely was. Every situation is different, if I had dormer windows Id need to figure out how to insulate these for example.

8. I used AAC blocks as part of my foundation build so sorry cant comment on an insulated raft solution. Someone else will probably give their opinions here, or you could search as I know its been discussed before

9. Everyone who wants to get the spec right goes through the same head scratching. Ive realised that there are lots of systems out there that are selling because they all have their plus and minus points. If I had to build a timberframe house or an externally insulated house I wouldnt be too upset as they both have advantages. In the end you have to just pick your choice of build and your spec and go for it. For me, thick walls (window seat) and soundproofing plus a mistrust of timberframe which Im getting over plus the DIY friendly aspects of cavity wall/ strip foundations pushed me that way.

Hope this hasnt confused you more! In an ideal world your engineer would be able to advise you, but we are a few years to early to hope for this yet. Any of the regular posters here that are qualified Engineers/ Architects etc would be able to provide this service, but unfortunately the greater pool of construction professionals dont believe in airtightness/ insulation/ future proofing so are still doing things the old way.

creedp

Thanks Soldsold for the detailed response ... much food for thought which I will try and absorb before having a further session with engineer and builder. Btw I haven't commenced the foundations yet so I should have plenty of flexibility with underfloor insulation. Interesting though that the builder wasn't so helpful when I put same question to him!

It would seem that the insulated drylining of external walls is probably an easier solution that use of Quinnlite blocks .. or more to the point my builder might have less resistance to the idea .. if the condensation/mould issue is not a concern. One further point, the build incorporates a single storey room with vaulted ceiling on eastern side of house - given no concrete 1st floor, would it be straightforward to use 100mm quinnlite blocks for this part of build and stay with std block with drylining for the main house.

Thanks again for all coments