Hey, guys i am in early stage on building my new home, whole house will be around 2800 SQ Feet plus basement, 5bdr 2and hlaf bath. My plan is to totally eliminate Oil its expensive and its sucks. I was thinking to do a radiant heating 3 stage, first floor 2nd floor and basement just berry the heating pipe in the concrete type of thing. On first and Second floor i was thinking to do http://www.sunboardpanel.com/ This. Now i will use electric water heater by GE probably go with 80 gallon version of this ge model - http://products.geappliances.com/appliance/gea-category/water-heaters I know electric in Long Island is expensive but my goal is to get solar by next year, the one that if you produce to much power ur meter is going backwards. So now my question can i use this two things and still have the water temp at 120F and have warm house? i dont know if i am saying it right, open water system? which is like my drinking water is in the floor and then it basically goes around and eventually going back to water heater? Let me know what u guys think...Thats my dream to have this type of system and install this Sun boards and make it work?

If you want to heat a house with solar, that means you need a heat pump, and not a tank heat pump water heater as they lack sufficient output to drive a radiant system and usually they are stealing their BTUs from the very space you're trying to heat. You would need, to do hydronic radiant, either a ground source heat pump or an air to water unit like the Daikin Altherma: neither of which are simple, cheap, DIY projects. I prefer the altherma as it removes a massive range of potential issues, but your mileage may vary. I'm not yet aware of any serious contenders for air to water heat pumps here in the US yet. Ground source can work but it's very expensive and a bad install can be a real nightmare; that must be closed loop in any case, at the very least.

You could do straight electric resistance using an electric boiler, but unless you are doing something damn near passive house construction it's unlikely to be economical. If you're serious about using solar to heat then the heat pump option, while expensive, will be cheaper than the solar panels it allows you to not buy. I just looked a smaller house up here in Maine for that comparison and the difference in required solar panels is around 10,000 KWH/year: that's about a 9kw array difference between a heat pump and an electric boiler.

Of course the FIRST solar to look at is passive solar design if you can. but you'll still need to deal with heat demands otherwise as well.

Never do an open system. Ever. That topic has been beaten to death many times so I wont' type much on it now. Basically it's only promoted by snake oil hucksters who don't actually care about people or their long term pocketbooks.

I've seen Sunboard, though I haven't used it. The aluminum is ok thickness and it's full coverage but my last sample did not show it to be well fitted. I have worked with Warmboard a lot over the years and I'm very happy with its performance and it would undeniably max out your 120 degree water temp limit, though whether it's necessary or not would depend on your heat loads and floor coverings.

You need to do a heat study my friend. A typical electric water heater has a pair of 4500W electric heating elements, only one of which runs at a time. 1KW/hr of electric = about 3400BTU/hr so a 4500W element will deliver around 15,400 BTU/hr. Unless you are throwing down some hefty coin on really good windows, it is possible you will shed that much heat per hour thru the windows alone in a 2800SQ/FT house during the winter.

I highly reccomend Borst Engineering's website and their free calculators. Look at the recent posts by sailawayrb she has put the links in those postings. It will take you a little bit to read thru the instructions, and you will have to review your plans to see floor space, wall area, window and door area and associated R or U values ect, for your planned construction. Once you have some info to plug into the program, it will give you an idea of the ammount of BTU/hr you will need to maintain a given temperature in your home. Unless you have real mild weather or are heavily above code for insulation and windows, 15Kbtu/hr probably isn't going to be enough and you will need a dedicated boiler capable of putting more energy into the water. Knowing this you can also get an idea of your electric costs. IE: If your calculated house used 15,400 BTU/HR, a 4500W element running constantly would maintain house temp. IF you pay 50 cents per KW/HR it would cost you $2.50 per hour, $60 per day, $1800 per month to heat your house... A heat pump type domestic water heater will definitely not cut it as the heat pump portion is very small and designed to maintain the tank at 120F more efficiently than an electric element cycling on and off. They still have electric elements to reheat the tank quickly. In heat pump mode, as mentioned, they rob heat from the area you are probably trying to heat.

Another good thing about the Borst calculator is that you can vary insulation values and get a real good idea of how much insulation increases will save you in energy costs. Typically insulation is the best bang for the buck, as installed insulation dosn't go up in cost like your energy bill is likley to do...

As mentioned, DO NOT mix your domestic water system and your radiant heating system. Keep these two systems separate for health reasons. The heating system if sealed will eventually shedd it's O2 and will remain relatively free of growth. If connected to domestic water it will continually injest gasses and eventually become contaminated. What you can do is use a heat exchanger to take heat from the radiant system boiler and put it into the domestic hot water heater, but the energy study may indicate a boiler temp that is lower than a desireable domestic water temp in which case this probably won't work very well.

There is a reason people use gas and oil. It's energy density usually gets you a greater BTU per dollar. A large heat pump can also beat straight resistance electric heating elements by a significant margine, but if it is cold where you are at, you may need to drill wells and put in a ground source system to provide a constant earth temp from deep below the ground for it to gather heat from, when the air temps are well below zero outside. The install costs for these type systems can be significant, but the operating costs are a fraction of straight electric resistance elements.

Of course all these are unknowable untill you have a better idea of how much energy you actually need.

Good Luck

Just to modify that slightly, here in cold climates it is generally cheaper to do electric boiler backup to an air to water unit than to go ground source. Not always, of course. But just because it's cold that doesn't mean geo is the only game.

I lived on LI for many years built a 2 story with basement 2800 sq

I used under the sub-floors aluminum reflectors with radiant, this was when you had to fab your own.

It worked great still does our oil bills were 1/3th everyone else s.

Now If I was still on LI I would build with SIPS and have a super insulated house with as much passive solar orientation as possible.

Skip the radiant maybe, get a few mini splits and your done, (compare the costs) I think the mini's win.

I guess the cost of the foundation & SIPS walls/roof is under $50,000

Some of these smaller homes are heated with hair dryer.

NRT rob, I agree, it depends on needs and climate. At some point you will have to move a lot of cold air thru the thing to harvest/concentrate enough BTU to heat the house. Or spend more time on the costly electric boiler. I guess it could also be an asthetic thing as no one really wants a blower that sounds like a small airplane running outside These problems become smaller if a lot of attention is paid to insulation quantity and details though.

The Sanden EcoCute air to water heat pump will soon be available in the US, but it's output is nowhere near up to the task of heating a 2800' conventionally insulated house at Long Island's ~+15F 99% outside design temp, and isn't sufficiently freeze-protected to handle a Polar Vortex low temp in L.I.. I know of one that is going into a PassiveHouse in Portland OR this year, but the load is pretty tiny, and the extreme cold temps are pretty temperate compare to L.I..

In new construction you have control over the heat load and orientation, and cutting the heat load in the design phase is a lot cheaper than later on.  Even if you don't take it to the PassiveHouse extremes, it's worth going way beyond code min.  Use the zone-4 row of Table 2 of this document as a rough guide, but also model the design in BeOpt to play "what if..." games with the various factors.

4Kw output(around 13KBTU) That might work for my house I wonder what the duty cycle is...

I wonder how the cost compares to just adding more PV solar panels and using resistance heat. No doubt that this would last longer.

PV would be horrendously expensive used for heat. Watts are watts regardless of the source. Takes a whole lot of panels on your roof to get even ONE KW which would net you 3400 BTU, and then only when the sun is shining. PV solar, if I recall correctly is only in the teens as far as efficiency in converting photons to electrons, and then only when oriented directly at the sun. It would also probably need a conversion to AC and a step up in voltage costing more in efficiency and hardware. Otherwise if left as low voltage DC, you would require very large copper to move the current to the heaters with less loss.

You could get a lot more heat with a lot less hardware with direct solar to water collectors such as evacuated solar tubes. Then just enough PV to power the circ pump. Direct collectors are far more efficient at turning photons into heat. Also heat made in excess to your needs could fairly easily be stored for use after the sun goes down, lessening the need for the boiler to be called on to maintain temps.

jonr is talking about netzero type strategies, not heating in real time with solar which is a waste of time with any kind of solar. If you have net metering or buy back programs in your state though, you can use summer collection to pay winter heating bills. Using a heat pump!

Well, when someone doesn't mention net zero and uses PV and resistance heating in the same sentence, it's not too hard to make that interpretation, LOL! However, I am glad we all agree that the ROI of using PV for resistance heating is not yet mainstream yet…

Sorry didn't catch the net metering part. That would be a do-able method, but still initially costly. Without subsidies however that method doesn't really pay off either IMO.

I have fielded this same type question on several occasions over the years(PV direct to heat), so I guess I just snapped It is amazing the number of people who have no clue how much energy they actually consume...

It seems to me you have natural gas at less than one dollar per therm. If this is the case, driving your radiant floors and heating copious amounts of DHW with a condensing boiler will lower your fuel bills while payback and ROI will exceed anything you can do with electrical power, from any source, period. Low NOx, low SOx and no acid rain. GREEN by any reasonable standard.

I guess I'll have to answer my own question.

I estimate that the EcoCute will pull about 2.5kw of heat out of the air and cost about $4k. So $1.60 per "free" watt. PV solar panels can cost $.80/watt and it turns out that driving resistance heat can be done with a simple circuit (a PWM regulator - no batteries, no inverters, no especially thick wires). Additional net metering is also an option (but it requires a larger inverter). So it comes down to how many hours/day each system runs. Depends on the household, but for domestic hot water, the number can be well under the number of hours that the sun shines.

There may be lots of better options, but that wasn't my question.

Jon
Are you talking about a lot of small heaters AT the panels? Because it takes really big wire to move DC at any useable current. If I am going to pump water to the roof, I would rather just pump it to a flat or evat tube panel. PV's also don't like short circuit loads/overloads as it forces them to dissipate heat internally, so some sort of cutout circuitry would be needed IMO to preserve the service life of the panel. A fixed resistance heater would provide a constant load to a varying PV supply, so low sun conditions the panel would be overloaded. PV's are also only at their peak efficiency at a certain output voltage, refered to as the Maximum Power Point. You need a smart controller to get the most out of them. You still arn't going to get around the overall low efficiency of the PV panels, and would require a large collector area to get any useable output... I personally have never seen anyone do it, and the math most definitely steers me in another direction...

oops

FWIW there are "reasonable standards" by which natural gas is not green at all there Morgan... methane offgassing, fracking, and it's not zero emissions it's low emission, to say nothing of the long term unsustainability of it. Recyclable solar panels have a lot of green benefit over burning hydrocarbons of any kind until we get to a point where we're synthesizing hydrocarbons with green energy and making it a closed loop system...

As you know, I am pragmatic.

Dreaming is good, science is wonderful, but if you want a warm house and a hot shower you have to pay for it. The market place clearly is leaning to natural gas. They killed the coal industry with it and we regularly cut natural gas bills in half using condensing boilers. For new construction insulation and heat recovery is the answer, at which point the heat source becomes less of a diminishing factor. An ERV with integrated dehumidification is the clear answer here. Maybe a PV panel for lighting. But people still want a hot shower, condensing NG is the practical, all-be-it relatively green answer.

I don't see many Passive House or Net Zero houses in cold climates. My goals are bigger and available to the average, or slightly above average person.

Sure, there are plenty of pragmatic arguments, no dissention there. I just don't like greenwashing. Natural gas is better than coal or oil, but that's not a very high bar to beat.
It might be the 'greenEST' option someone can afford. But that doesn't make it green.

Be aware in New York and a few other states, many people can get solar on their roof for free (F-R-E-E), with a power purchase agreement locking in your electrical rate lower than grid cost right now. Combine that with a heat pump and you're doing about the best we can do these days from the green perspective at a price that should be affordable to most.