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Cost of renewable energy.

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  • 30-08-2014 6:17pm
    #1
    cork2
    Registered Users Posts: 291 ✭✭


    Everybody is probably going to criticise me for posting this but I am very serious about this. I'm currently working on 3 houses which are at first fixing stage and they are just going about getting wiring and piping in place for solar, geothermal, air to water and air recovery systems. In talking to guys fitting and and selling these systems I have a couple of question. How easy is it to get replacement filters for air recovery units, due to the fact there is no make or model number on two of the units I've seen and I got a smart assed answer. How do you clean the ducts out as all commercial systems have sponge balls you pull through the duct lines to sweep them of dust which could be released back into the air, basically I was told where to go. Finally the big one, how long does it take roughly for these things to pay for themselves and how much to run them, I wouldn't be too fussy about paying for itself because that's down to how well you use it but I want to know what it costs to power these units and run them and nobody will tell me, it's my opinion they don't know what the cost is! I also believe and again I'm going to be slated for this but it's my opinion airtightness is blown all out of proportion. It's more about selling membranes and tapes than airtightness. If you're trades take care there isn't the need for half of it. I recently witness a house where there was a shot of silicone put in every conduit in the house, a line of airtight expanding foam around the windows and a squirt of foam around the wires dropping from the ceiling. they grey coated the walls and that was that. No tape, no paste, no gomits, no membrane and when the test was done they got a near perfect result. Again this thread isn't to cause trouble, I'm merely trying to figure out if I'm the only one that thinks money could be better spent in a build!


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    #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    On one hand you suggest the guys fitting the systems don't understand them, then On the other, your outline of an air-tight install (without result figures )is questionable. Imo the quality of building comes down to three distinct (unfortunately quiet separate) factors : design , install & user.

    The air-tightness silicone & foam used near electrics- they were the correct fire rating?

    Filters for the system should be considered at design stage and the homeowner aware of the cost & maintenance requirements.

    payback of renewables should be worked at design stage and now involves a specialist and then requires good well trained/ knowledgable installers( the ones you've spoken to should be able to answer your questions or point to a spec/professional who does know)

    Good design & good constructors are equally important. I'm sure you Will appreciate that things can go wrong or not work very well when shortcuts in design or construction are taken.

    questionable building control regs and counter intuitive building regs need to be factored into this also.


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    #3
    MicktheMan
    Registered Users Posts: 2,825 ✭✭✭MicktheMan


    cork2 wrote: »
    Finally the big one, how long does it take roughly for these things to pay for themselves and how much to run them,

    Why do they need to pay for themselves? They are there to do a job.
    I have never seen a pay back calc done for a roof. Why - because it has a specific function. Why do other necessary elements that go into a building require to pay for themselves?
    Do you have a vacuum cleaner? Is so why? How long does it need to pay for itself?

    cork2 wrote: »
    I also believe and again I'm going to be slated for this but it's my opinion airtightness is blown all out of proportion. It's more about selling membranes and tapes than airtightness. If you're trades take care there isn't the need for half of it. I recently witness a house where there was a shot of silicone put in every conduit in the house, a line of airtight expanding foam around the windows and a squirt of foam around the wires dropping from the ceiling. they grey coated the walls and that was that. No tape, no paste, no gomits, no membrane and when the test was done they got a near perfect result.
    Airtightness, in the irish context, is critical to achieving a comfortable and affordable to heat home (now and for the lifetime of the building). Period. It is in fact more important to achieve a good level of airtightness (and appropriate ventilation) than to superinsulate a house. Why? Our temperate but very windy climate.
    Your example of not using specific air tightness products to achieve a satisfactory test result is all good and well but how will the same building score in the test in 5, 10, 20, 40 years time? Expanding foam, silicon etc wont last the test of time. Proprietary products will. You get what you pay for.:)


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    #4
    cork2
    Registered Users Posts: 291 ✭✭cork2


    I don't have the result figures from the airtightness test to hand but I will get them during the week. All silicone and foam used near electrics was correctly fire rated and evidence of this was provided and approved by the engineer used in the build. I completely agree with what you say about systems effectiveness coming down to design, user and installer and I think design and installer are the two main factors which on some sites can be seriously flawed. If these things aren't worked into the design of a house first day they can't work. I'm currently working in a house where half the house will have air recovery and the other half won't because there is no way to work the ducts through the steel frame which intersects the house. I mean what I know about these system is very limited but I would have thought to be effective it should be an al or nothing job!


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    #5
    cork2
    Registered Users Posts: 291 ✭✭cork2


    MicktheMan wrote: »
    Why do they need to pay for themselves? They are there to do a job.
    I have never seen a pay back calc done for a roof. Why - because it has a specific function. Why do other necessary elements that go into a building require to pay for themselves?
    Do you have a vacuum cleaner? Is so why? How long does it need to pay for itself?



    Airtightness, in the irish context, is critical to achieving a comfortable and affordable to heat home (now and for the lifetime of the building). Period. It is in fact more important to achieve a good level of airtightness (and appropriate ventilation) than to superinsulate a house. Why? Our temperate but very windy climate.
    Your example of not using specific air tightness products to achieve a satisfactory test result is all good and well but how will the same building score in the test in 5, 10, 20, 40 years time? Expanding foam, silicon etc wont last the test of time. Proprietary products will. You get what you pay for.:)

    Of course they need to pay for themselves! If you get 20 years out of a roof leak free I think you could say it paid for itself. It's much easier to determine a roof paying for itself than a vacuum cleaner. Such a product would come down to what kind of material your cleaning, how often your using it for and for how long your using it ;)

    I admit I don't know the life span of silicone, but the expanded foam is an actual airtightness product and a specific airtight grade of foam, therefore whether you use a vast array of products or not that particular product still has the same life span. What is the calculated lifespan of the glue on airtightness tape? or the lifespan of airtight acoustic sealant?? Maybe you pay too much for what you get? I'm just coming from the point of view of what I plan to do in my own house when I build it in a year or twos time, from a professional point of view, any building I go into someone else will have designed the airtightness layer and I will fit whatever small aspect I'm asked to fit to a high standard and in the manner expected of me. I am actually considering doing one of the fitters courses just to learn more as I am genuinely interested in learning about it.


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    #6
    MicktheMan
    Registered Users Posts: 2,825 ✭✭✭MicktheMan


    cork2 wrote: »
    Of course they need to pay for themselves! If you get 20 years out of a roof leak free I think you could say it paid for itself. It's much easier to determine a roof paying for itself than a vacuum cleaner. Such a product would come down to what kind of material your cleaning, how often your using it for and for how long your using it ;)
    So then what is the formula to show that a roof pays for itself over its useful life?
    The reason I threw in the vacuum example is because it's not strictly necessary in a house as its function can be achieved by other means, but it is a more convenient and efficient (time wise) way of sweeping floors

    cork2 wrote: »
    I admit I don't know the life span of silicone, but the expanded foam is an actual airtightness product and a specific airtight grade of foam, therefore whether you use a vast array of products or not that particular product still has the same life span. What is the calculated lifespan of the glue on airtightness tape? or the lifespan of airtight acoustic sealant?? Maybe you pay too much for what you get? I'm just coming from the point of view of what I plan to do in my own house when I build it in a year or twos time, from a professional point of view, any building I go into someone else will have designed the airtightness layer and I will fit whatever small aspect I'm asked to fit to a high standard and in the manner expected of me. I am actually considering doing one of the fitters courses just to learn more as I am genuinely interested in learning about it.
    Proprietary airtightness tapes have a guarantee of at least 40 years as does the mastic. I don't know of any foams with these specs (if they do perhaps you would send me a pm with details).
    Yes they are expensive now but as with everything, the more they become the norm and are used more widely, this should effect prices positively.

    The thing is that if you design and construct a good building fabric wrt airtightness, thermal bridging, insulation etc, then the real economic benefit is in the significantly reduced cost of installing and running a very simple and efficient heating system.
    And also don't forget the unquantifiable thermal comfort benefits to the occupants.


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    #7
    cork2
    Registered Users Posts: 291 ✭✭cork2


    MicktheMan wrote: »
    So then what is the formula to show that a roof pays for itself over its useful life?
    The reason I threw in the vacuum example is because it's not strictly necessary in a house as its function can be achieved by other means, but it is a more convenient and efficient (time wise) way of sweeping floors



    Proprietary airtightness tapes have a guarantee of at least 40 years as does the mastic. I don't know of any foams with these specs (if they do perhaps you would send me a pm with details).
    Yes they are expensive now but as with everything, the more they become the norm and are used more widely, this should effect prices positively.

    The thing is that if you design and construct a good building fabric wrt airtightness, thermal bridging, insulation etc, then the real economic benefit is in the significantly reduced cost of installing and running a very simple and efficient heating system.
    And also don't forget the unquantifiable thermal comfort benefits to the occupants.

    A formula doesn't exist for such a thing. The answer is defined using education and experience in the given area combined with common sense! If I construct a flat roof for you and you choose a roof covering with a life expectancy of 15 years and you get 25 or 30 years of it problem free before it begins to show signs of wear and tear well then that roof has paid for itself. My original point about things paying for themselves was that if these systems save you 100euro a year in heating but costs 200 euro a year to run, service and maintain them well then n my opinion it would be a waste of money. Air recovery is a good example I'm told by a man who used to fit these systems in the U.S and Canada for a long time that the unit you bolt to the wall outside which is similar to an air conditioning unit is in no way cost effective to run and will have a serious impact on your esb bill. He also says the most important thing in Ireland is to get a piece of paper stating the lifespan of this unit as he says most he has seen here are infact units made for light commercial work where they would be running almost continually and just being adjusted higher and lower and he reckons after 3 or 4 years you will see a lot of them wearing out due to continual switching on and off.

    I suppose to answer my questions as apposed to talking to installers on building sites I should be talking to individuals who have build such houses and have been living in them for a year or two.


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    #8
    fclauson
    Registered Users Posts: 1,691 ✭✭✭fclauson


    Using the roof example - I installed MHRV for comfort - which does not have a fixed price - a dry head from the rain also is a comfort thing again has no fixed price.

    When looked at an overall package a Passive Certified House will pay for itself in two ways
    1 - low running costs - my total heating and hot water bill is around €1.2 per SqM per annum). My HRV (from memory as it was two years ago I did the calcs) costs around €1 per SqM per annum
    2 - comfort - price from €0 to €100 per Sqm per annum !!!!! based on a number of factors including feedback from family members

    We live on a windy site - but who cares - our house sits at around 21C day, night, morning, evening, spring, autumn, +20C outside, -10C outside.


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