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New build questions

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  • 29-07-2010 10:26am
    #1
    studdlymurphy
    Registered Users Posts: 827 ✭✭✭


    Hi All,
    Im just waiting on final planning to return good news and I have a few questions that I would like a little help with.
    Firstly I want to have solar water heating hoping that this will cover my hot water needs for the summer is this realistic? is it any use or just a gimmic? I cost it at about 5000euro and I could buy alot of electricity for 5000.
    Secondly I want to have 2 solid fuel stoves that will heat the house and water in the winter my plan for this is to have each shower fitted with a thermostatic shower and an electric shower for when that water is not hot enough is this a good idea?
    Thirdly is it possible to have under floot heating with solid fuel boilers as I know the radiators get very hot is there a way of not having the floor scalding hot?
    Finally the house is 2300sqft and I was hoping to have upstairs concrete floors instead of wodden joists what would be the extra cost of this approximatly


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    #2
    Quazzie
    Registered Users Posts: 28,887 ✭✭✭✭Quazzie


    studdlymurphy wrote: »
    Hi All,
    Im just waiting on final planning to return good news and I have a few questions that I would like a little help with.
    Firstly I want to have solar water heating hoping that this will cover my hot water needs for the summer is this realistic?
    I'm no expert on solar DWH systems but there are lots out there that use it to great effect. With everything else its about getting the right system and the right set up.
    studdlymurphy wrote: »
    is it any use or just a gimmic?
    No, it does work very effectively but again what you get out of it is what you put in, so research fully all options available to you before deciding on any one system.
    studdlymurphy wrote: »
    I cost it at about 5000euro and I could buy alot of electricity for 5000.
    You would, but Electricity rates will rise and as it does the payback period for solar will shorten.
    studdlymurphy wrote: »
    Secondly I want to have 2 solid fuel stoves that will heat the house and water in the winter my plan for this is to have each shower fitted with a thermostatic shower and an electric shower for when that water is not hot enough is this a good idea?
    Its possible but is it really necesary, would an immersion switch for your tank be a better option for the times when this is required.
    studdlymurphy wrote: »
    Thirdly is it possible to have under floot heating with solid fuel boilers as I know the radiators get very hot is there a way of not having the floor scalding hot?
    Solar and UFH to my knowledge use a much lower heat to heat the house. The thing with UFH is that you never need it scalding hot as its a much slower and generalized release of heat through the house. Radiators use far greater heat because they need to generate much greater localized heat for it to transmit across rooms etc, whereas with UFH the whole floor is liek a radiator so it doesn't need to reach such high temperatures. Ths means that using two different heat sources that supply at different levels will probably require a lot of complicated and expensive plumbing.
    studdlymurphy wrote: »
    Finally the house is 2300sqft and I was hoping to have upstairs concrete floors instead of wodden joists what would be the extra cost of this approximatly
    The cost is approx 125%-200% depending on what system you use. For me the deciding factor was never having to worry about creaking floorboards in the future. That alone was enough for me to go for Concrete floor upstairs rather than try combining a rad and UFH system.

    I think all the information I've supplied is correct but if there is anything wrong hopefully someone else will correct it.

    Best of luck with the build btw


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    #3
    gears
    Registered Users Posts: 758 ✭✭✭gears


    € 5000 seems very expensive for solar in a new build. If you take out the cost of a tank, which you will need any way and do a deal for installation with your plumber the net cost should be €1-€1.5 less, at a guess.


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    #4
    Viking House
    Registered Users Posts: 551 ✭✭✭Viking House


    Are you falling into the trap of concentrating on how to heat the house instead of concentrating on building the fabric properly? You can avoid the need for heat by super insulating, no cold bridges, v good windows and airtightness. Concrete is bad for the environment, use timber floors, you can easily make them quiet.


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    #5
    beyondpassive
    Registered Users Posts: 558 ✭✭✭beyondpassive


    studdlymurphy wrote: »
    solar
    Solar has a long payback 11-13 years or so, but you'll need about 6sq.m for building reg compliance, so its not avoidable. No Brainer.
    studdlymurphy wrote: »
    stove
    There are grants for wood pellet stoves and boilers, so they are economical. Stoves can out put about 10kW to the cylinder and rads, they are rated at higher, but in practice with Irish wood and turf its hard to get the levels of performance stated by suppliers. Haulin wood and refilling the stove or boiler is a pain.
    A. Energy Efficiency
    The first priority if considering covering your winter heat load, would be to
    1.) limit building envelope heat losses.
    2.) limit your heating system distribution losses
    3.) limit ventilation heat losses and recover waste heat.
    You could aim for a half passive spec at the least at about 28 kWh's per meter square per annum for space heat and about 16 for hot water with the solar covering 40% of the annual load. For 220sq m house should give you heating bills of about €800 euro per annum if you were using oil only.

    B. System design.
    You need a heating system that is designed to suit the houses heat load, this can be done empirically rather than through rules of thumb or suck it and see approaches.
    Analysis would prob suggest having an oil boiler as back up instead of an emmersion to ramp the hot water up to 60 degrees every second day as a guard against Legionella. It would be worth using a 1000L tank to store heat from your stove back boiler and to make the most of sunshine on rare days in the shoulder months (spring/autumn). The heating system can be designed to incorporate a heat exchanger to heat the house from the hot water storage tank using low grade heat to feed underfloor or low heat rads.
    studdlymurphy wrote: »
    precast first floor
    (This may affect your ridge heights)
    If the house is correctly insulated and cold bridge free, the mass of the concrete slabs can enhance the thermal inertia of the building, evening out fluctuations in the heating cycle and giving stable comfort. Rather than blasting the house with heat twice a day, you just input a steady background heat. This works well with our uneven climate, the house acts like a Bat cave. This is also important in the day/night cycle.

    So the best plan of action to take is to use the Passive house approach to building and get some certainty instead of guesswork and heresay. Detail all junctions to be airtight and have continuity of insulation, this is critical especially at the floor wall junction. Doing a standard A3/B1 build is a false economy and will need more heat that the DEAP output suggests.

    Good Luck.


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    #6
    Out Of Order
    Registered Users Posts: 135 ✭✭Out Of Order


    Viking House wrote: »
    Concrete is bad for the environment, use timber floors, you can easily make them quiet.
    That's what I'm doing, what do you recommend for stopping the noise?


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    #7
    Viking House
    Registered Users Posts: 551 ✭✭✭Viking House


    The cheapest way would be to use a 25mm layer of HD Polystyrene between 2 layers of plywood with no fixings between the sheets of OSB. A double layer of plasterboard on the ceiling onto crossbattens could improve the build-up by 10dB.


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    #8
    ricman
    Closed Accounts Posts: 1,559 ✭✭✭ricman


    THE solar heating system is worth getting,if you are going away for 2 weeks,find some way to knock it off.IT can overheat if not used for 2 weeks,ask the installer about it, get install price from 2 companys for x amount of panels.LIKE new windows it takes over 6 years to payback the installation cost.on a average size house it should heat all the water,apart from say september to jan/febuary, it also depends on how many solar panels you fit.they are usually placed
    on the rear roof.


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    #9
    Poor Uncle Tom
    Registered Users Posts: 14,547 ✭✭✭✭Poor Uncle Tom


    ricman wrote: »
    THE solar heating system is worth getting,if you are going away for 2 weeks,find some way to knock it off.IT can overheat if not used for 2 weeks,ask the installer about it, get install price from 2 companys for x amount of panels.LIKE new windows it takes over 6 years to payback the installation cost.on a average size house it should heat all the water,apart from say september to jan/febuary, it also depends on how many solar panels you fit.they are usually placed
    on the rear roof.
    ?

    The panels are placed on the most southerly facing roof surface, whether that is front or rear or side.

    Also, the solar heating system for any house should be fully designed for that house before installation begins, this system can then be priced from several suppliers.

    The payback period is going to depend on the amount spent on the system, the size of the system and the use got from that system, over and above the use of other hot water and central heating methods used and can not be generically stated as being 6 years or 7 years.

    Incorporating a heat dump is important if the system is going to stagnate for any period of time in order to prolong the lifespan of the components.


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    #10
    ricman
    Closed Accounts Posts: 1,559 ✭✭✭ricman


    SOME people just get a solar system installed to mostly heat the hot water for showers or taps, as you,d need a large system to heat a house.AND the amount of power ,heat generated declines in the autumn/winter.I,M not saying its not possible to heat a house with solar power ,but you would need a oil/gas central heating system for the winter .The design of the heat dump is important as solar panels work as long as there is sunlight, i,m assuming most people go away for 1 or 2 weeks on holidays each year .


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    #11
    soldsold
    Registered Users Posts: 552 ✭✭✭soldsold


    Viking House wrote: »
    The cheapest way would be to use a 25mm layer of HD Polystyrene between 2 layers of plywood with no fixings between the sheets of OSB. A double layer of plasterboard on the ceiling onto crossbattens could improve the build-up by 10dB.

    Has this been tested (EPS between plywood sheets)? Any link to the test/ STC values?
    Timberframe floors can be designed to very good soundproofing levels but this usually involves decoupling the structure, which the above doesn't do.

    Soundproofing is very complex, and something that looks like it should work probably wont!.

    Carpet stops impact sounds from being produced, Resilient channels (metal isolation tracks, they look like dropped metal ceilings) help to isolate different parts of the structure from each other so the sound vibrations cant get across the gap, and mass (eg two layers of plasterboard) provide a barrier to the sound waves.

    But using a tried and tested build is the only way you can be sure you are not wasting money.


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    #12
    studdlymurphy
    Registered Users Posts: 827 ✭✭✭studdlymurphy


    The solar system is not to heat the house I only want it for the taps and thormostatic showers. Will this give enough hot water for summer? Ill have a couple of solid fuel stoves in the house that will be used for heating in the winter. What size tank should I use? Also is it better to have the normal hot press or would it make more sense water pressure wise to have the tank in the attic to give it more height?
    Cheers again


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    #13
    ricman
    Closed Accounts Posts: 1,559 ✭✭✭ricman


    see here
    http://en.wikipedia.org/wiki/Solar_water_heating#Considerations_during_the_installation_of_a_solar_water_heating_.28SWH.29_system
    how many panels are you getting, how big are they?


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    #14
    studdlymurphy
    Registered Users Posts: 827 ✭✭✭studdlymurphy


    Not sure haw many panels I will need. Im planning on having a pretty big tank 500litres or even more. How many panels would be needed for this.
    Does anyone know the average summer/winter temps the systems will heat the water up to?


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    #15
    ricman
    Closed Accounts Posts: 1,559 ✭✭✭ricman


    SAYS HERE 2 to 3 panels enough for 3-5 people, using a 300litre tank
    see <SNIP> that,ll heat the water at least 9 months of the year.



    Mod edit: ricman please read the forum charter. Thanks


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    #16
    Viking House
    Registered Users Posts: 551 ✭✭✭Viking House


    soldsold wrote: »
    Has this been tested (EPS between plywood sheets)? Any link to the test/ STC values?
    Timberframe floors can be designed to very good soundproofing levels but this usually involves decoupling the structure, which the above doesn't do.

    The structure is decoulped. Here are some links, you can see the effect of the second layer of plasterboard and the layer of crossbattens under the joists. A concrete floor is about 45dB so its easy to improve on that. http://www.paroc.com/channels/com/building+insulation/solutions/intermediate+floors/partition+timber+floor.asp
    http://www.paroc.com/channels/com/building+insulation/solutions/partition+walls/partition+walls+with+wooden+studs.asp


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