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€100,000+ Just for Heating/Ventilation in New Build A1 Rated Passive House. Looking for Alternatives

  • 25-02-2022 9:49pm
    Registered Users Posts: 1,495 ✭✭✭

    Hi Guys,

    We've just started building work on a very large (450m2+) bungalow being built to passive (or better standards) which will be very well insulated and airtight.

    It's got a Building Energy Rating [kWh/m2 y] of 22, and U Values and airtightness levels well within passive house levels.

    Now obviously it is a very large house (it has high ceilings so a large volume) but it's heating requirements should be relatively low.

    It's clearly a very poor time to be building in terms of costs being high (one builder quoted €5,000+ per m2 to build it!) but one aspect that is really sticking out is the cost of the heating/cooling/ventilation which is coming in at over €100k installed.

    This seems more nuts as I figured by building a very well insulated/airtight house that it would have minimal heating requirements and so would not take much to heat.

    The current planned system has a main Nilan Air to Water heat pump for ventilation, heat recovery and production of domestic hot water. As the volume of the house is so big there is a separate MVHR unit also to handle air for the bedroom wing (it's an L shaped bungalow). We were planning to use underfloor heating throughout the house.

    Because the house also has a ton of south/west facing glass (these sides of the building are mainly windows) I'm quite worried about overheating. We're putting in external solar blinds on all these windows that should do a very good job of keeping the heat out to begin with but I want to also have a backup in case the house still gets too hot. The heat pump/MVHR in summer mode will provide 2kw of cooling but we were planning to either add an aircon unit (which can provide an extra 5kw of cooling) or potentially do ground source heating via boreholes instead of air to water and use that for cooling also.

    A final consideration is the house is going to have an absolute ton of solar panels on the roof (30kw+) so we're going to have a lot of excess electricity in the summer months. This might make some equipment like exhaust hot air systems for heating not worth buying as we'll have close to infinity electricity for heating water etc.

    Any of the providers of heat pumps etc seem to want to sell me very expensive systems which I'm wary of. I've no real interest in fancy technology, I just want to be able to keep the house as close to about 20 degrees in living rooms/18 in bedrooms year round so heating the house in winter and potentially cooling it in summer. I like the idea of the MVHR /ventilation in terms of keeping the air moving/fresh in the house and in theory I'd prefer to avoid a system that involves heating only through the air as I don't really like the idea of that.

    Just wondering if any of you had any ideas of how to achieve this without spending crazy money.

    I'd thought about maybe ditching the heat pump altogether, going with some form of simple electric heating such as these:

    I'd then obviously need somthing for water heating also and still need a MVHR system.

    Any thoughts on this would be much appreciated. As I say it just seems nuts to have to spend €100k+ on heating/ventilating a house when it should have minimal heating requirements. I'd imagine I could put in a cheap gas boiler, and keep the place toasty till well after I die for an awful lot less than 100k even with rising gas prices!

    Thanks in advance


  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    Cant help you on advice in what way to go, But is it the case of buy once, cry once? even at half the quote you gave to build the house its not a cheap one..

    As its a passive house, You'll need the MVHR for ventilation, And with that much solar pv.. well you could just use an immersion! (or something along the lines of the sunamp heat batteries, which also can be "charged" with a heatpump)

    Sure you suggested a gas boiler, they can run UFH fine too. Its the actual work of putting all the pipes down and all that fun stuff is the real cost but not the heat pump itself.

  • Registered Users Posts: 9,773 ✭✭✭antoinolachtnai

    What does your architect or adviser say?

  • Registered Users Posts: 1,495 ✭✭✭blobert

    Thanks, to be honest I have my doubts about "buy once, cry once" in terms of being extra annoyed if I pay loads for a fancy heating system only for it to have issues.

    The two new build houses I've lived in in the last 5-10 years have both had nothing but issues with a lot of the newer technology. In one the solar water heating never worked properly and the ongoing repairs to it cost way more than the system saved in heating. In the same house we had to replace the water pump within 3 years, the gate motor twice in less than 10 years, and several other systems broke within a few years. We're currently living in a 4 year old house (renting) while we build the above house and in the 3 months we've been there the water pump has broken, the gate motor has been replaced and the heating system has broken down twice. We might just have had bad luck but it does not bode well in terms of new house technology!

    I had a look at the Sunamp but they look expensive for what you get.

  • Registered Users Posts: 1,495 ✭✭✭blobert

    Our architects were the ones that introduced us to the +€5000 per m2 builders so they are not great on the value for money side.

    I've spoken to another architect with more experience in passive houses who pointed us in the direction of the €100k option mentioned above but it seems to be a very niche market and very hard to get independent advice on things. I believe there are only about 40-50 certified passive houses in Ireland so it's a pretty tiny market.

    The other confusing aspect as I say is each of the sellers will say their own products/systems are great and everyone else's are rubbish. For example the ground source heating guys will say it's amazing/will last much longer, guys that focus on air to water will say ground source is terrible/overpriced/air to water is now better.

    So it's very tricky to get good advice on it.

  • Registered Users Posts: 45,247 ✭✭✭✭Bobeagleburger

    30kW+ worth of panels would be some system.

    That should nearly provide hot water all year by itself!

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  • Registered Users Posts: 9,773 ✭✭✭antoinolachtnai

    Not having strong advice is a big problem for you.

    I would at least look at the approach of putting in the ventilation and all the fabric elements (like ufh pipework) of the heating. But don’t put in a boiler or heat pump or controls (beyond what is necessary for the ventilation).

    then put in a few temperature loggers, and buy a few electric heaters and stick in the cupboard and see how you go. Since it’s a bungalow you can always upgrade the ventilation later and add air con if it is unavoidably required.

    it is not my area of knowledge at all but the volume of the house is not the only thing that should drive ventilation sizing. The level of occupancy also makes a difference. Maybe the sizing there can be revisited.

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    If it were up to me, I'd avoid very fancy expensive systems too. My initial thought was "**** ton of PV" 😁

    It can easily power aircon for free if it really gets hot in summer and it would quite likely provide near 100% of your hot water requirements on all but the darkest few days in winter, and even some room heating, for the rest, just use simple cheap electric heaters and immersion. If you spend €40k instead of €100k, that difference is more than a lifetime worth of extra spending on less efficient (read: simple) systems for heating

  • Registered Users Posts: 6,602 ✭✭✭El Gato De Negocios

    I am building currently, not passive standard but will be minimum of A2 rating.

    House is 2 storey, approx 2800 sq ft, air to water, UFH upstairs and downstairs with MHRV installed.

    For that alone, it's costing approx €25k.

    So for the size of your house plus the fact its a bungalow, €100k or thereabouts isn't all that surprising imo. You have fuckin massive floor space so the amount of pipe work and ducting required is huge, I'm also assuming that you will need a bigger than standard spec heat pump?

    Just on the solar panels. I was asking my plumber about them as we aren't having them. He reckons they are a waste of time because when you are getting the most benefit from them ie summer time, you need less heating / power so what's being generated is not being used alot of the time. Also, you are generating electricity but it has nowhere to go, batteries are ultimately crap and have a poor shelf life and are expensive to replace. That's anecdotal of course but maybe something to consider.

    If you think the heating system is expensive wait til you start looking at kitchens and tiles. 😭

  • Registered Users Posts: 2,411 ✭✭✭bullit_dodger

    I'd also jump on that bandwagon from unkel. The one thing that we know works pretty well is pv in terms of payback. It's a tried and tested platform. Sure in terms of "pure efficiency" heat pumps be they ground sourced or air sourced are more efficient, but the jury's out there (personally) for Heat pumps with me. That's not to say that you can't get a good result for 20-25 years with a Heat Pump, in fact considering the saturation of HP in Scandinavian countries it's clear the tech works. It's essentially a fridge in reverse, so 100+ years old tech :-)

    But they are expensive to install, and there's a certain risk associated with them. Is that risk a justifiable risk? It could be on a new build. For me I really wanted to adopt one, but my own gaff just isn't airtight enough.

    That PV for cooling though is a no brainer, if "over heating" is a concern. In the summer when it's hot, that's were you have a shed load of excess available and could easily have AC powered by that excess

    Ballparking in my mind 15-20Kwp or thereabouts, along with a 10Kwhr (min) and ideally 20Kwhr battery. Wouldn't think you'll break €25K. and you could install a regular condensing boiler.

  • Registered Users Posts: 6,805 ✭✭✭Alkers

    Am I missing something here?

    You're building a 450m2 house and think €100k is too much for the heating & ventilation? That's less than €225/m2 or less than 10% of typical build cost per m2 in Dublin currently (for bog standard spec).

    If you're even considering spending €5,000 per m2 on the overall build, €100k seems pretty reasonable in the scheme of things and there are likely other areas in which you can easily save that kind of money. Shave 20m2 off of your design and you've paid for your heating system while only reducing your overall space by 4%, which you won't notice.

    What percentage of overall cost would you expect the heating & ventilation to come in at?

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  • Registered Users Posts: 6,177 ✭✭✭Ubbquittious

    Not that long ago you could build a decent size house for 100k.

    Now prices are all inflated because some fcuking muppet in the greens signing a document years ago and some other pen pushers from comfy Dublin offices foisting their will upon everyone. Pack of cnuts

    It's just to ensure the 100,000 leaves your pocket and you spend the remainder of your life paying bank interest on it.

  • Registered Users Posts: 984 ✭✭✭Still stihl waters 3

    You could, but with outdated and substandard insulation and heating by todays standards, I'm not a huge fan of some of the newer tech but building a mansion that'll cost well over a million at the worst possible time regarding prices etc and complaining about the price of something so important in achieving passive status seems silly, no one needs a 450 sq meter house imo but if they want to build it more power to them.

    The OP asks " just wondering if anyone has any ideas on how to achieve this without spending crazy money" I have an idea, build a smaller house that won't cost crazy money

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 8,095 Mod ✭✭✭✭Jonathan

    This is the Renewable Energies forum. If you want to discuss politics, the Politics forum is here.

  • Registered Users Posts: 1,495 ✭✭✭blobert

    Thanks, that could be an option though I'm not sure if it would mess up our compliance/BER certification if we don't have a heating system, I'm guessing with the massive amount of solar might mean we'd be ok. We'd need to put in the ventilation now but as you say we could hold off on the heating till we see how we are.

  • Registered Users Posts: 1,495 ✭✭✭blobert

    Thank Unkel,

    Yep, my thinking was our big excess of summer electricity would be easily able to power any air con needed for cooling.

    I know some German passive houses don't bother with underfloor heating at all and just use low wattage electric heaters.

    I was thinking if you just had some manner of electric immersion mainly powered by solar, a ventilation system/maybe with air con for cooling and some sort of cheaper heating such as the panels you could avoid the heat pump altogether and the costs of all the underfloor piping for it (which is significant)

    That said I suspect the underfloor heating is going to give a much nicer even heat than a couple of panel heaters.

    I had thought somthing like this could be good in terms of having a larger heating area:

    But I don't think it will work with our house as it's coning to be all concrete walls with external insulation and this seems to need stud walls with insulation right beside the panels.

    I'd agree with your sentiments that the potential savings on a simpler system will likely more than make up for it being less efficient.

  • Registered Users Posts: 1,495 ✭✭✭blobert

    Thanks, I'm not planning to pay €5000 per m2, closer to €3,000

    While we're building a very large house we're looking to do so as cost effectively as possible and this just stood out as a very high figure so I thought it might be an area that could be saved on. Especially, as I say as we're spending quite a bit to have the house well insulated/airtight so it seems odd you'd then need to pay a huge amount for a complex system to heat it when it's heating requirements should be fairly low.

  • Registered Users Posts: 64,693 ✭✭✭✭unkel

    I have no idea when it comes to modern heating / cooling / ventilation systems, but I do know what solar PV can do for you. Some stuff might surprise you. There are simple immersion diverters that automatically send electricity from your solar PV that you are not using, directly to your hot water immersion. A system like that costs not much more than €500. Including labour. Yes, that cheap. If you put up say a 20-30kwp array and have a 1000l well insulated tank, then I'd say 95% of your hot water could come from those PV panels.

    Another consideration is that heating your house with cheap and environmentally friendly night rate electricity (already over 50% from fully renewable zero emissions wind in Ireland at the moment and going up every year), that's a system you can get away with in a very well insulated house, even from simple cheap heaters, is only a bit more more expensive than using gas / oil. Obviously a lot more expensive than using modern heatpumps, but without any of the huge up front costs

  • Registered Users Posts: 297 ✭✭spose

    You can also add heating to the heat recovery like these…

    I’d definitely focus on the air con. Summer bypass on the mhrv is not really active cooling from my experience. For us with well insulated dormer and not too much glass it can’t keep the temp down during warm spells

  • Registered Users Posts: 2,730 ✭✭✭yankinlk

    the discussion of needing air con in Ireland amuses me. Where do ye all live that its getting that hot? open a window or a door ffs.

  • Registered Users Posts: 13,234 ✭✭✭✭fits

    In a passive house if there’s a lot of solar gain there can be an argument for air con. My house can get very hot even in winter.

    oP have you considered a smaller house?

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  • Registered Users Posts: 110 ✭✭Scoopsire

    If the house u-values and airtightness levels are at passive level standard then the other key elements of a passive build should be factored into the design, an analysis undertaken using PHPP software by a Passive house designer would probably provide answers to your over heating concerns as well as the level of heating required.

    Passive certification has a limit on how many hours per year a house can exceed 25°C, with many passive designs incorporating external shading to address overheating.

    Best of luck with it!

  • Registered Users Posts: 9,238 ✭✭✭markpb

    I’ve lived in three different apartments that could have done with some kind of active cooling. All of them had south-facing, floor-to-ceiling windows with no Bris soleil or other architectural features to block the direct sun. Opening a door or window isn’t going to help much in that case unless you can open another one on the opposite side to create a cross-breeze.

    The first apartment where I experienced that would regularly reach 28 degrees in summer with the windows open and the blinds closed all day long. It was a single-aspect apartment so the windows didn’t create a cross-draft.

    The second was situated about 400m from the M50 so leaving the balcony door open meant that you couldn’t carry on a conversation inside without subtitles.

    The third was a triple-aspect apartment on the 11th floor so you could get a nice breeze going but if you stepped either side of the path of the breeze, the rooms were still very hot.

  • Moderators, Home & Garden Moderators Posts: 5,752 Mod ✭✭✭✭graememk

    80's bungalow here, Massive windows all round, have to keep telling the mrs to keep the curtains closed and windows closed, your only letting the heat in!

    We're mostly out during the day so the darkness isnt a big deal.

    Still think about getting some sort of portable aircon to at least cool the bedroom or something.

    we got a break last summer, the sea mist rolled in late afternoon most days and kept it fairly cool.

    Anyways, Waaaay off topic lol.

    Heatpumps help the BER rating a lot. (or a non labeled boiler hurts BER a lot too!) Say the house needs 10 kWh per m2 to heat, (which is the heart of the BER anyway) and old boiler is 60% efficient so you actually use 40% more "raw" energy so 14kWh, put in a condensing boiler, and that is reduced to 10%

    As heatpumps are 3-400% efficient, that takes down the required energy to heat it, so more like 2-3kwh per m2

    (ive picked numbers out of the air for easy counting)

    eg my house is a C3, It prob would be a B if i had a condensing boiler, and the ber assessor just ignored the solid fuel stove that does a lot of the actual heating.

  • Registered Users Posts: 1,702 ✭✭✭poker--addict

    It might be too late, but given the size of the project and financial outlay, I'd be engaging another architect or advisor. If your system is not correctly sized and balanced the energy usage (on going cost) and capability of the system can quickly compound into a huge issue and spend (ask me how I know!!).

    Even 10k for proper advice here could have decent ROI. Disappointing performance from your current advisor.


  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF

    Do you live in a passive house?

    OP can you just confirm, have a you carried out any software assessment associated with the Passivhaus certification process?

    if so what is the w/m2k expected for this 450m2 macmanson?

  • Registered Users Posts: 13,234 ✭✭✭✭fits

    No but it is as close as possible to the standard without incurring the additional expense to get to that standard.

  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF

    As close as possible to what? you’ve no bench mark, if you’re not calculating the house to the passive house software, then where did the 22w/m2k/yr come from? The BER software? If so why not take any reference to passive house out of the thread?

    450m2 bungalow. If the cost is shocking you loose 100m2 ..saving you twice the cost of heating/ventilation (not clear on how this figure was reached)

  • Registered Users Posts: 13,234 ✭✭✭✭fits

    You are making assumptions here that are wrong @BryanF our house was designed by a passivhaus architect and the software was used. But our house is not certified passive not least because it is linked to a 200 year old building.

    the solar gain in our not passive house is mainly a problem at this time of year when the sun is lower in the sky and the trees not yet in leaf to provide shading.

  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF

    Made assumptions after asking and not getting answer. Still not clear what your asking in this thread, to me the 450m2 bungalow?? is what’s throwing thing off with regards to heating & ventilation costs

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  • Registered Users Posts: 611 ✭✭✭MakersMark

    A 5000 sq ft bungalow is possibly the least inefficient house you could build in this country.

    As you're finding out!