# Heating house with solar panels OR geo therm & radiant heat.... anyone successful?  Low temp radiant



## Solar+Wood (Feb 23, 2011)

Anyone successful with heating a home or a small area with in-floor radiant heat using solar panels as the primary heating source?
How about geo-therm and in-floor radiant heating applications?

Any real world examples here?

Anyone I can PM or talk to?

I'm starting to re-evaluate all my options.

Thanks,
Solar+Wood


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## pyper (Feb 23, 2011)

I thought about it.

I looked up all the formulas and figured out how much heat I could reasonably collect, etc.

I decided that it probably wouldn't be worth it -- wood is inexpensive and more reliable (compared to solar)


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## Solar+Wood (Feb 23, 2011)

pyper said:
			
		

> I thought about it.
> 
> I looked up all the formulas and figured out how much heat I could reasonably collect, etc.
> 
> I decided that it probably wouldn't be worth it -- wood is inexpensive and more reliable (compared to solar)




Thanks for the info/opinion!

I understand, but do you know of ANY real world examples?  One of the members here mentioned a low temp application and I started to looking at the web for such setups and found a geo therm retro that fit the bill.  The one place I read said that underfloor staple-up apps would not work, but slabs would.  But I want to see if any end-users are around here using solar or, I guess, geo-therm.  Salesmen are an interesting bunch with the web of info they spin.  An end user/consumer is were I'd rather start and work my way back up that food chain to the supplier.

So.... anyone have or know someone with a solar setup that actually works primarily via solar?  
Anyone have or know someone with a geo-therm modified for an in-floor radiant application?

TIA!  
Prob the thickest headed dude on the forum    <g>


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## WhitePine (Feb 23, 2011)

Solar+Wood said:
			
		

> So.... anyone have or know someone with a solar setup that actually works primarily via solar?
> Anyone have or know someone with a geo-therm modified for an in-floor radiant application?
> 
> TIA!
> Prob the thickest headed dude on the forum    <g>



Well, we primarily heat with the sun. We built a passive solar house that needs no other energy source on a sunny day, but it sounds like you are trying to find a way to use the sun to heat an existing home. That's a different animal.

Post if details on our place would help.


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## Adios Pantalones (Feb 23, 2011)

A freind with a passive solar greenhouse attached on the South side of his house gets most of his heat from it in Deerfield, NH.  Very effective, but does rely on sun and doesn't help with solar storage I suppose.  He starts all his plants in it in the spring and stores a few things in the summer/winter, so it's triple duty. 

In the boiler room you'll find folks with solar heat plugged into their storage tanks- not a big modification to the wood boiler system, and plenty of DIY systems as well


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## benjamin (Feb 23, 2011)

Geo is a great match for slab heat as you've read. You'd be looking at a water to water heat pump, this could also heat DHW with the right controls. The only downside of water to water is no AC. I know of one system that uses a dryfloor system of some sort, no "mud" but it was built new and designed and owned by a geo installer.  He loves it.  Slab heat would be that much more efficient or cheaper to install.  

It's pretty easy to build a mostly solar heated home, more so in CO than WI, retrofitting one is much harder.  I have a passive solar home and solar collectors and have burned just over two cords of wood this winter.  The biggest advantage of the solar is limiting amount of time I burn.  I'd burn about the same amount of wood if I eliminated all of the south facing windows.  I started burning in mid December and had one fire on Feb 12, then again on the 20th, again today, and I'll either keep this going for two days or have to burn again in a few, then it looks like sun in the forecast and hopefully I'll be done.  

By all means examine all of your options, you'll probably find builditsolar.com the best reference out there even if you're going to eventually have all the work professionally done.


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## pring7 (Feb 23, 2011)

I heat my home partially with solar heated water.  I use evacuated tubes in a pressurized loop to heat a 200 gallon water tank.  Another pressurized loop sends the hot water up to a water coil next to my air handler.  When the water temp gets too low, or the inside/outside gradient is too much to overcome, the heat pump kicks in and sends warm air in through the system.  It works ok, but I am considering adding more solar collectors to the system to get more out of it.  

The nice thing about eastern NC is that we (normally) have a mild winter.  The bad thing is that when it is cold outside it is normally more overcast than a nice summer day.  I retrofitted a house that was built fairly recently.  If I were to build from scratch I would consider a similar system, but use radiant heat in the foundation.  I think that it would give the system a plenum and allow for more consistent heating.  I would definitely consider having about 4 collectors for a similar sized home (1500 sq ft.) and more water storage.  I think that you have more clear winter days and may do better in Colorado.  You should definitely have a backup system though in my opinion.  A small boiler like the Thermo-control model may be a good way to go.  http://www.thermocontrolheating.com/


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## PapaDave (Feb 23, 2011)

S+W, precaud has done some work with solar on his house. 
https://www.hearth.com/econtent/index.php/forums/viewthread/57663/
Check out http://www.builditsolar.com/index.htm for other ideas too.
HTH


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## jebatty (Feb 24, 2011)

The concept certainly is feasible. I mix-down to 100F supply for the radiant floor in my shop, floor set at 61F. Solar HW at 100F+ is within reach almost everywhere, even in N Minnesota. But, during the dead of winter we only get about 2 hours of enough sun to produce this kind of btu output, and often late Nov to early Jan is very cloudy. Fortunately, the sun returns and the clouds go away.


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## Solar+Wood (Feb 24, 2011)

Thanks folks.  Starting to read some of the info provided.  What confuses me is storage.  

I've used Garns spreadsheets to get an idea on storage and firings (using the sun as "firing" instead of wood).  I come up with their biggest unit which I think is 3,000 gallons.... again, if I want to sun-fire once a day.  The number of panels required for that would be very very expensive.  I'm wondering if I really need that much storage.  I was figuring half that originally.  I need to insulate more and do a heat loss calc either way..... so I guess I'll know after that.

The other option is a hybrid using something that burns fossil fuel.  Still need to super insulate and stop air infiltration.  Even thought of a Trumbe wall of some sort if I go forward with the addition to the cabin. 

Gonna take a break, my little head hurts today with all of this <g>.

Thanks again.


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## pyper (Feb 24, 2011)

Don't forget that your slab is storage. When you pump 100F water into a 50F slab, the water will give up it's heat really quickly. A lot of passive solar guys put up two layers of sheetrock as well, because it's good storage.


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## sesmith (Feb 25, 2011)

Solar+Wood said:
			
		

> Thanks folks.  Starting to read some of the info provided.  What confuses me is storage.
> 
> I've used Garns spreadsheets to get an idea on storage and firings (using the sun as "firing" instead of wood).  I come up with their biggest unit which I think is 3,000 gallons.... again, if I want to sun-fire once a day.  The number of panels required for that would be very very expensive.  I'm wondering if I really need that much storage.  I was figuring half that originally.  I need to insulate more and do a heat loss calc either way..... so I guess I'll know after that.
> 
> ...



You can first try calculating your homes heat loss here:

http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

Then see what more insulation will do for you:

http://www.builditsolar.com/References/Calculators/InsulUpgrd/InsulUpgrade.htm

You will find that adding insulation levels first will be the biggest bang for your buck.

That being said, you'll find a ton of information on solar space heating ideas here:

http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

I currently use a solar air heater that supplies about a quarter of our heat...this is with no storage other than the house.  You can do close to 100% solar, even in our area, which is lousy for solar, but the price goes up exponentially as you try to get a system that will supply all your needs around here.  FWIW, 3000gal of water storage is way overkill and would require somewhere around 1500 sq ft of solar panels to keep it fed.


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## WhitePine (Feb 25, 2011)

sesmith said:
			
		

> You can first try calculating your homes heat loss here:
> 
> http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm



Take a look at the HEED software available free from UCLA. I used it along with a commercial program to calculate the heat loss and gain figures for our passive solar home. It proved to be very accurate -- more so than the commercial program.

It runs on your PC or Mac rather than on a web site. Your data is saved on your hard drive making it easy to do what if scenarios. It has built in weather data for California, but the instructions tell you how to use it for any location. 

http://www.energy-design-tools.aud.ucla.edu/heed/


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## Seasoned Oak (Feb 25, 2011)

Solar+Wood said:
			
		

> Anyone successful with heating a home or a small area with in-floor radiant heat using solar panels as the primary heating source?
> How about geo-therm and in-floor radiant heating applications?
> 
> Any real world examples here?
> ...


I get about 12-14 hours heat on sunny winter days even with very cold outside temps with a south facing windowed room. Pretty much heats a 3000 SF poorly insulated house for that time period. Id like to build on this with more insulation and possibly adding ET solar collectors and a water storage system. A great setup would be a wood gasification boiler and storage to feed radiant floor heat . Solar and wood are a great combination IMO


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## Como (Feb 26, 2011)

I also looked at this, I am in an area of high solar and high heat demand.

Good for hot water, would make a small contribution for space heating.

I f you have a very low heat demand, very tight building then it could make a good contribution, but passive solar works better as a design concept. In that sort of structure, the heat loads are so low that radiant floor is overkill.


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## Rhone (Mar 14, 2011)

I don't know what you're looking for. 

Geothermal: Best for hot and warm humid climates, not as good for cold.  When used for cooling the heat it generates can go into your water tank or a preheater so you cool your house and heat your domestic hot water at the same time for a 2 for 1 on investment.  When used for heating, the cold it generates can't be used so one only gets 1 for 1 so it's best cooling ones house as much as possible not heating.  The cheapest is typically an extra deep well with 2 walls, the geothermal and your drinking water is sucked up the middle pipe and geothermal dumps back to the same well but to the outer pipe where it circulates downward (warming or cooling) and gets sucked back up for drinking or geothermal.  That isn't allowed in a few states, some don't allow water used in a heating system to dump into water you drink.  For heating a gallon of oil (including inefficiencies) produces 40.7kW of heat and previously cost $1.89/gallon when I last ran the numbers (that's a long time ago).  With my electric costing $0.21/kW the same 40.7kW of heat costs $8.55 using electric.  Since geothermal is 300% efficient, cut that by a third and Geothermal cost $2.85 in the end to produce the same 40.7kW of heat as someone does paying $1.89 for oil.  Aka... not good for heating dominated climates, especially with power plants buring coal to deliver it.  I have 2 friends that chose geothermal... one wishes they did solar instead and the other won't tell me how much their electric bill is.  Today rerunning the numbers with oil costing $3.59/gallon and my electric is $0.23 geothermal wins compared to oil, $3.59 vs. $3.12 for the same 40.7kW but I think it's because electric hasn't jumped yet.  Since I live in an environment of 7-8 months of heating and like 7 days of cooling geothermal isn't especially attractive, but that's because I can't use it for its strength.  Change it around and put it in a place with 5-8 months of cooling and in humid environments where swamp coolers can't work and it's going to shine like a superstar compared to the other cooling alternatives (window AC, etc.).  

Solar, I have more experience.  I have 3 panels on my roof I use for domestic hot water, I've had it 3-4 years now.  My in-laws have 8 solar panels on their solar house which they built in 1983, our best friends have 40 evacuated solar tubes, and a coworker has 30 evacuated solar tubes.   I don't recommend evacuated tube solar for heating/hot water, don't recommend photovoltaic (the kind that makes electricity), I do recommend the flat panel collectors (the 4x8 ones).  Let me know if you want to know why.  I wish I'd gotten 3 more panels so I could use it for both heating & hot water, because I really hate spending as much time as I do burning wood.  I hate bringing wood in, I hate stacking it, I hate clearing paths in snow to it, I hate the ash, I hate the bugs.  Most of all, I hate when it's 35-50F outside and sunny and I'm spending an hour bringing in wood getting a fire going, dealing with ash, kindling, knowing had I three more panels I could let it heat my house and not have to deal with wood.  My inlaws with the 8 solar panels (central VT) have all the hot water they need and only burn 1/2 cord of wood/year.  They don't need to burn even that much they like their house to be 75F+.  

I got my system from http://www.radiantsolar.com/solar_packages_and_pricing.php the one with the 3 panels & tank.  Fortunately the controller they sent is capable of heating and their instructions had me using pipe sized for heating & domestic hot water so I could technically add the 3 panels.  I figure in the end the system I got cost me around $7,000 (when copper prices were through the roof) and I got about $3,300 back.  I originally calculated around $450-$500/year return but with oil jumping it's now around $700/year.  

I concluded today for just fuel it would cost...
$55000+ to heat with straight electricity
$2,469/year to heat with oil ($3.59/gallon)
$2,200 with geothermal (I suspect it's going to jump shortly)
$700/year to heat with wood (or probably around $75-$100 if you do it yourself)
$39/year to heat with solar + 1/4th of one of the above (around here in cloudy New England solar can cover about 75% of ones needs retrofitting so 25% is needed for something else)

Wood is probably the cheapest to install up front and can be really cheap if you get & split the wood yourself but the above only accounts for heating.  There's some value to the time & effort with wood.  Solar costs me -$700/year technically because solar gives free (or mostly free) hot water all year long saving me money.  I'd really consider solar, if you have forced hot water solar will heat your house in spring & fall (but you'll probably need to supplement in winter without Radiant floor heating) and get you free hot water all year long, and there's incentives from the government.  In New England where I live many of the houses have forced hot water baseboard heating.  That doesn't matter much with solar compared to radiant becase here the dead of winter is always cloudy so even if you HAD radiant floor heating you're not going to get much out of it except in Spring & Fall anyway... which should be enough to get the temps baseboards work at.  

Makes me really think again about how much I want 3 more panels.  It would cost me about $3000 and I'd get $1,100 back.  There are worse things one could spend a couple grand on (like wood


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## Seasoned Oak (Mar 15, 2011)

Rhonemas
What is it you DONT like about Evacuated tube solar?


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## Solar+Wood (Mar 15, 2011)

Rhonemas said:
			
		

> I don't know what you're looking for.
> 
> 
> Solar, I have more experience.  I have 3 panels on my roof I use for domestic hot water, I've had it 3-4 years now.  My in-laws have 8 solar panels on their solar house which they built in 1983, our best friends have 40 evacuated solar tubes, and a coworker has 30 evacuated solar tubes.   I don't recommend evacuated tube solar for heating/hot water, don't recommend photovoltaic (the kind that makes electricity), I do recommend the flat panel collectors (the 4x8 ones).  Let me know if you want to know why.


------------------------

Rhonemas:

Appreciate your thoughts.  Still reading about this stuff on the other site many here have suggested and re-evaluating all.

Iâ€™d really like to know more about your friends and family heating their house with the evacuated tubes.  I assume itâ€™s hydronic/in-floor radiant heat and really tight homes.   Would like to know what they like, dislike and would do different if they had to do it all again. 

Also would like to know why you like the flat panel heaters for solar heating and not the evacuated tube types. 

PM me if you want.

Best regards,
Solar+Wood


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## snowleopard (Mar 16, 2011)

Found this article and thought you might be interested: http://www.newsminer.com/view/full_...s-home-in-the-winter?instance=home_lead_story 

 Note the angle of the solar panels--that's oriented towards the winter sun.  The article addresses storage..  

Here's the other article referenced in the story: 
http://www.newsminer.com/view/full_...ep-Fairbanks-home-toasty-with-almost-no-fuel? 

Here's the Cold Climate Housing Research Center referenced in the article: http://www.cchrc.org/


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## Exmasonite (Mar 16, 2011)

Rhonemas-

Not to derail the thread but can you give some reasons for not liking photovoltaic?  

We have a log home in New England and have debated looking into solar power.  We heat about 70% with wood and are happy with it.  our biggest issue is electricity.  Looking to be a little more eco friendly/energy independent.  We just got the house in the fall so haven't looked into it seriously yet but was debating having some contractors come out to do an assessment this spring.  

Again, feel free to PM me if you get a chance or post here... sorry to the OP for the tangent.


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## Solar+Wood (Mar 16, 2011)

Thanks!  I'll read those today.
.
.
.



			
				snowleopard said:
			
		

> Found this article and thought you might be interested: http://www.newsminer.com/view/full_...s-home-in-the-winter?instance=home_lead_story
> 
> Note the angle of the solar panels--that's oriented towards the winter sun.  The article addresses storage..
> 
> ...


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## 4acrefarm (Mar 16, 2011)

This summer I built hot air colectors on the back of the house. They work OK. They pull air out of the basement and send it to the coldest room in the house. It is fan forced with a snap disc switch triger.

I want to  build hot water panels to intigrate into my wood / radiant setup. I want to run 1000 galons of storage and 300sf of flat panel. I plan on making my own panels out of pex.

The reasons I would not evac-tubes 

1 price

2snow will not melt off them because of their low temp

3 frost same problem as snow.

when it is cold you tend to get these conditions.


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## benjamin (Mar 17, 2011)

4acrefarm said:
			
		

> The reasons I would not evac-tubes
> 
> 1 price
> 
> ...



Evacuated tubes are a high tech way to provide a low tech solution, kinda like using nuclear energy to boil water. From what I understand they are "efficient" at producing higher temperature water at lower light levels. Flat plate collectors are so much cheaper that the efficiency is irrelevant compared to the btu/$. 

PV is amazing technology if your other option is trucking in propane to run a generator or a fridge, but if you have grid power then there is essentially no payback, even if you don't figure in maintenance. 

The Alaskan Passivehouse articles were another example of dubious affordability. $100,000 in equipment and still burning wood, propane and diesel??? and they call that affordable??? The first article mentioned bringing the costs down for future homes, the problem is that as long as energy is expensive then copper will be too, when energy is cheap copper will still be too expensive for most people to afford to use it to absorb solar energy. 

I agree with the idea of combining solar and wood with mass for cold climates. The advantages of that combination are shortening the burning season and much greater comfort and convenience. The designs in the article are certainly state of the art, but I think they're pushing the envelope way beyond what will ever catch on in the real world.


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## Como (Mar 17, 2011)

He went through 170 gallons of propane â€” counting appliances â€” and expects to consume 20-30 gallons of diesel this year.

If I had not read the article I could have got a somewhat distorted view.

And the other house did not have the toys that the second guy obviously liked. And you forgot to take of the rebates.


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## benjamin (Mar 17, 2011)

And two cords of wood with 22" walls?!?

I didn't "forget" to take off the rebates because I paid for them.

I like the articles and designs.  If you can make it work in Fairbanks you can make it work just about anywhere, and if the price tag drops enough it might actually make sense for some areas.


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## snowleopard (Mar 17, 2011)

benjamin said:
			
		

> 4acrefarm said:
> 
> 
> 
> ...


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## snowleopard (Mar 17, 2011)

benjamin said:
			
		

> And two cords of wood with 22" walls?!?
> 
> I didn't "forget" to take off the rebates because I paid for them.
> 
> I like the articles and designs.  If you can make it work in Fairbanks you can make it work just about anywhere, and if the price tag drops enough it might actually make sense for some areas.



The Fairbanks climate and building conditions are benificent compared with some of the conditions in rural Alaska.   There's a quote attributed to a King Islander: â€œBefore the missionaries came, we lived underground in sod houses and laid away our dead on the tundra. . . . Now we live above ground and bury our dead. - and we haven't been warm since.â€   I've been in some old underground houses--homes, rather-- that could be just about heated with body heat.  HUD houses are now typical of housing in villages, and residents are moving to urban areas because they can no longer afford the cost of heating these places (2x4 walls with the wind whistling underneath, not sited towards sun).  

I was at a local building supply store last week looking at new toilets.  This vendor sells package houses that can be trucked, barged, or flown into rural villages, towns, and off-road hub cities, complete down to the last nail you need, like the old Sears houses.  I was looking at toilets, and was told of their .8/1.28 deal-flush "This is the one we're putting in our package houses."  The bottom line is driving that decision.  Green makes sense and cents, in this case, and I for one am cheered by this.


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