I am building a passive solar home in northern Illinois (HDD 6500).  I really, really like the feel of radiant floor heating for comfort.  This would supplement the passive solar.  The house is 2000 sq ft and will be super insulated.  I'd like to put in PEX tubing in the unfinished basement and the unconditioned 2 car garage.  I'm also interested in a small ice/snow melt run in the concrete immediately outside the garage doors.  I'm guessing I will need a small wood-fired boiler.  I'd also like to take advantage of this for DHW.  Does this sound reasonable? 
I'd like to burn wood in a stove on the covered porch for some warmer of this space/aesthetics.   I don't know if there is any type of unit that exists that could go in this location and supply these needs.  Is there? 

Best to use an EPA qualified wood gasification for the heat as it could do everything you are asking. Also look at Crete-Heat , now comes in 3 " FMI see The Green Building Products Store.com

I design or re-design a wood-fired boiler/radiant system per week. You can do it, but ask your designer/contractor for references on snow melting systems as they are beyond the experience of most.

Take a look at the Empyre Elite 100, by pro-fab. Its an indoor gasification wood boiler and a do all for a 2000sq ft home, depending on your climate:

http://www.profab.org/products/prof...x.html

It takes a 24" full log with no need for it to be split.  I will heat the fluid in your floors as well as provide your domestic hot water.  Also has an electric backup option for the times you're away and not there to put wood in it.  Very high efficiency, can be installed indoors with your standard flue and very low emissions. Last I checked they're 6500$ and the usual spring 500$ mark down is in effect.  I priced one out recently and the electric backup system was 400$ extra..

By the way, this is just through my own research.  I have no part in this company nor have I used the product since its a little oversized for my heating requirements!

Posted By grish50 on 02 Mar 2011 08:54 PM
I'd like to burn wood in a stove on the covered porch for some warmer of this space/aesthetics.

Just out of curiosity, what other reasons do you have for wanting to go with a wood boiler? I'll offer some opinions/thoughts after I have a better feel for your thinking.

I too would like to use wood for supplemental heat. I have heated with wood for 33 years, using high efficiency catalytic stoves. Though I love wood heat - and I have lots of wood on my farm - I can not stand the dust it generates in the house. My original plan was to use an outside wood boiler to get the dust etc outside, but research on what was available changed my mind, as it is obvious the technology is not there yet. It seems the only way to get the wood boiler out of the house is to use a high efficiency one with lots of water for heat storage, and that does not appeal to me either.

Since I have always wanted a wood fired outdoor bread/pizza oven, and do much grilling outside during the summer, I am thinking now of building some kind of outdoor combination oven and grill combined with high mass, so you would just need a series of small hot fires, to get the thing up to temp. I also want to integrate a loop in the concrete mass that I can hook up to my in floor radiant, through a heat exchanger, to provide an additional way of inputting heat. Is there any practicable way to do this? Since the mass would be outside, is there some way to insulate it?

I am also looking out for an option to use wood to generate supplemental heat but sitll not able to get one appropriate solution for that which comes under my budget too








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Electric Heater

Check out this indoor wood gasification boiler:
http://www.hydro-to-heat-convertor.com/gasification.html
it's designed for high efficiency houmes

I agree with using a hot, clean, efficient burn and then water tanks to store the heat.

Jonr,
Where would you locate the water tanks, and how many gallons of storage/sq ft of house would you need? (assuming a well insulated and sealed house, but not super insulated, in the range of 20,000 btu/hr total heat loss)

-Rosalinda

The size of the water storage for wood boilers depends on the size of the boiler and what you want to accomplisch.
EN305 goes by 10 gallons per 2,600 BTU output of the boiler.
So a 100,000 BTU wood boiler would require a 385 gallons water storage. (100,000 / 2,600 * 10)
As an example: if you store the water at 180F and your supply/return water temperatures are 160/140F then you have a delta T of 180-140 = 40F
385gallons of water weighs 3,207Lbs (8.33Lbs/gallon)
This results that 385 gallons weighs 3,207 Lbs x 40F = 128,300 BTU's can be stored in this tank.
At a heat demand of 20,000 BTU/hr this will give you 128,300 / 20,000 = 6.4 hours of usefull storage.
If you want to accomplisch a much longer buffer for times that you are away from home you will need to multiply these numbers accordingly: 2 days = 24H will require 24 / 6.5 * 385 = 1,420 gallons of storage.
For high efficiency homes we typically put in a tank of 100 to 200 gallons.
Also storage tanks are expensive, around $1,000 per 100 gallons
If your temperatures are much lower, for instance for radiant floor heating, you can get a much longer storage time.

What Marc said. If you can make 120F-140F work, then you can use inexpensive polyethylene tanks - like $700 for 1000 gallons. EPDM lined ICF tanks are also possible (up to 165F).

I would be using the hot water for my radiant floor, so 120 to 140 f would work fine. Where would you have to put the tanks? I really don't want to take up the space in my house, and I don't want a wood burner in the house, so would I need an insulated outbuilding? Could the tanks go in the ground or would they lose too much heat?

-Rosalinda

For a small tank, I'd find somewhere to put it inside. But for a large one (the best way to go), I suppose you could build an outbuilding around the tank and then fill the entire building with cellulose or fiberglass (whichever is less expensive per actual R value). In the ground, perhaps SCIP construction would work - dig the hole, build a thick EPS foam box around the tank, then cover with fiber reinforced concrete to add strength. If it gets below 100F - go swimming.

If you have an outdoor wood gasification furnace you would hook a small flat plate heat exchanger to hot water tank. this would provide all the hot water needed for domestic and radiant useage. The circulator pump runs all the time, keeping the tank at 120 or whatever it is set for. Have sold hundreds of these systems.

Placed outside the house you have the risk of freezing, so you need to add a certain % of glycol to be safe.

Running water does not freeze. We have installed hundreds of outdoor wood furnaces without glycol. The pump is always pushing the water. I have personally had mine for 10 years, have gone away (no wood burning) and the pump kept it from freezing as I was gone for 3 months. I live in Maine

I don't have an outdoor wood gasification furnace, because they are not sufficiently efficient or ecologically clean for my tastes, and are also too expensive for just supplemental heat. I am thinking along the lines of building a multipurpose, high mass, outdoor wood fired, bread oven, pizza oven and grill, to which I would add piping to heat a closed loop system through a heat exchanger, to add supplemental heat when desired, to my radiant floor system. Yes I would need glycol for the loop. If I could integrate this wood heated thermal mass and heated water with water based heat storage (which would allow me to use insulated PEX to carry the water to the house) and maybe even toss in a greenhouse to the mix, even if I spent the same money as on just an outdoor furnace, I would have a more versatile system that would serve my needs better. It should also be more efficient, since it would be heated by small hot fires, rather than a long smoldering one. I already own a 10X12 greenhouse kit and could envision burying an insulated polyethylene storage tank underneath it, so heat loss from the tank would help heat the greenhouse, and the greenhouse would help keep the soil around the tank dry.
-Rosalinda

A couple of problems, Rosalinda. You'd have to jerry-rig the heat exchanger in the oven, and the result is usually inefficient and perhaps dangerous as well. Most of the heat likely will go up the flue. To get 60 percent to 70 percent output in hydronic requires a sophisticated stove design. And mass would be a hindrance. If the masonry is 20 degrees when you fire the oven, for example, it could take most of the first burn to reheat it. Finally, the gravitational pull of the couch is in direct proportion to the difficulty involved in lighting that fire. That pull may be insurmountable if the task requires wading through snow.

That said, I share your disdain for OWB and your yen for an outdoor oven. May I suggest AAC as the perfect medium: http://www.readersdigest.co.za/build-an-outdoor-oven Naturally insulating, easy to shape. Assembly with wood screws and thinset mortar. Quite durable after an application of stucco.

"Finally, the gravitational pull of the couch is in direct proportion to the difficulty involved in lighting that fire. That pull may be insurmountable if the task requires wading through snow."

I love that!!!! Laughed out loud

This is the one that got me thinking.... always a dangerous thing

http://www.motherearthnews.com/Do-It-Yourself/Build-An-All-In-One-Outdoor-Oven-Stove-Grill-And-Smoker.aspx
-Rosalinda