Want advice on woodstove/radiant heat floor

[Guest]

For years we heated with wood (in another location) and we were tired of the effort. So no woodstove in the new house, instead an oil fired radiant heat floor.(tubing in gypcrete.)
  Now we generate a lot of nice dry hardwood scrap in the biz. With oil going skyhigh we are thinking of installing a wood stove. We looked at a "scan" a Danish stove and at about $2100 for the stove and another $2500 with piping and install it is a bit pricey.    Any suggestions?  
    We would like something to heat 2200 square feet of well insulated house. It would be nice to have a clean modern look to the stove, and it would be REALLY nice to have some option to pre-heat water to flow thru the existing radiant tubing as the heat is so nice and even.   We have not found a wood stove with any kind od water heating jacket.

[K Frame]

You're getting into really specialized territory when you want to hook a wood stove into an existing oil or gas fired boiler system.

As for the stove, you're going to pay a lot for just about any wood stove. $2100 for the stove doesn't sound all that pricey, given what I've seen. $2,500 for the piping may be good or bad, depending on how much work it is to install it.

Your best bet is to get as many bids as possible.

When you add a water jacket to the stove (and there are those with water jackets) you start losing the clean, modern lines.

Look at Jotul stoves. I think they're among the best looking.

[Leatherneck]

Have you got a fireplace? Inserts are fairly reasonable and very effective. We've heated a 2300 sq. ft. house entirely with the insert for years. We use about 8-10 cords of cured hardwood a year.

If no fireplace, you'll need to install a triple-wall stainless steel chimney and use a freestanding stove.

I've always liked the ability to get close to a real hot heat source on cold days. So do the dogs!

TC

[m1911owner]

There exist wood-fired boilers that can be used in a radiant-heating system.  I found at least two or three a few years back in a Google search, but I haven't bookmarked them.

For radiant floors, there's a really good alternative to Gypcrete at www.warmboard.com" target="_blank">www.warmboard.com.    It's a bit pricey, but it avoids most of the drawbacks of Gypcrete, like high thermal mass causing slow response time, and difficulty of using some types of flooring.  Warmboard is a system that uses 4'x8' sheets of 1-1/8" plywood subflooring with an aluminum sheet over the top, which is grooved to receive 1/2" PEX or PEX-AL-PEX tubing on 12" centers.  This is used to construct the subfloor in the same way you would install a normal subfloor.  People in the radiant industry who have used this system say that it has the highest thermal efficiency and best responsiveness of any radiant floor system out there.

Edited to add: A wood-fired boiler is usually used with a fairly large storage tank to store the heated water, which tends to come at a rather uneven rate from the boiler.  (As I remember, those boilers do have a certain amount of ability to modulate the the fire by controlling the amount of air, but, as I recall, the level of control is somewhat limited.  So you need a buffer tank.)  You then use an injection piping system to extract the amount of heat you need from the buffer tank.

Edited again to add: I reread you original post, and realized that the house already exists.  I'd read the last paragraph too fast and had thought you were preparing to build a house.  So the information on Warmboards is obviously not relevant to what you are doing.

One of the beauties of a hydronic heating system is that you can feed it with hot water from many different kinds of sources.  So it shouldn't be too hard to add a wood-fired boiler into your existing system.

With all the controls that Tekmar was www.tekmarcontrols.com" target="_blank">www.tekmarcontrols.com, you can probably put together a control system that will take whatever heat you have from the wood boiler, and then suplement from the oil-fired boiler only when you're not getting enough energy from the wood boiler.

I Googled "wood boiler", and here are the first three results.  There appeared to be quite a few more, as well

www.freeheatmachine.com" target="_blank">www.freeheatmachine.com
www.woodboilers.com" target="_blank">www.woodboilers.com
www.centralboiler.com" target="_blank">www.centralboiler.com

[K Frame]

A wood-fired boiler isn't a clean, modern looking woodstove, though...

[cfabe]

Most of the 'old tech' wood boilers are rather crude. To modulate the fire the adjust the draft, and when the stove 'turns on' to a heat demand, there is typically a lot of cresote built up in the firebox and flue that burns of releasing a huge plume of nasty smoke. Also, most are open system boilers meaning that the water can absorb oxygen from the air, which means your boiler and pipes can corrode over time.

There are some 'better' wood boilers, one name that comes to mind is Tarm, they sell some sort of wood gasification boiler that's supposed to be very clean burning and efficnet.

I believe you can also get combination wood and natural gas or oil boilers, but if you've already got a system in place that may not be of interest to you.

[zahc]

My parents and grandparents have had a Central Boiler outdoor woodstove for decades now. No complaints. My grandparents interfaced thiers with thier existing forced air heat by fitting a simple heat exchanger and turning off the gas. My parents put radiant floor heat in their log house. Radiant floor heat is the best way to heat a house, period. The boiler only needs attention every 3-4 days in the summer (it heats their hot water too), and once a day in the coldest winter.

[Guest]

Thank for the info. i think that oil/wood combo boiler is interesting, though I still think I would like to be able to cosy up to a nice fire. (glass window woodstove.)

[Tallpine]

We heat our whole house (about 2000 sq ft) with an old "Blazer" wood stove through Montana winters.  All the wood (so far) has come right off our own land.  It's hard work (you get warmed at least twice ) and it's messy, but it works.  Little electric fans help circulate the warmth around the house, and when you're really cold you just back up to the stove until your britches start smoking

[280plus]

Take a look at "soapstone" woodstoves. I don't know if they make any that heat water but they are attractive and very efficient. They'll get you in the $2000 - $3000 range IIRC. No piping though, that's just for the stove.

Are you "resetting" the boiler? That means as the outdoor temp goes down the boiler water temp goes up proportionately. So that on warmer days you don't HAVE to run the boiler all the way up to 180*. That will save you some fuel. You MUST keep your boiler return water up above 140* if it is cast iron though, due to flue gases possibly condensing in the chimney and causing corrsion problems with the boiler.

How are you mixing down (or tempering) the water going to the floors? Are you using the boiler to make your domestic hot water also?

As far as oxgen rot caused by open systems, the solution is to have NO ferrous (iron / steel)parts in the system. Bronze pumps instead of cast iron, copper pipe instead of steel, etc.

here's one link to a company I'm familiar with. The part about them being friendly and helpful is very true!  

http://www.woodstove.com/

Google "soapstone wood stoves" and you'll find more.

good luck!

[Guest]

280 plus- We are useing a closed system with pex tubeng in gyprete with an oxygen barrier tubing.We have a buderus oil boiler with a water tank below and have a heat exchanger to heat the domestic hot water. The water temp for the floor is controled thru a mixing valve.  The system runs extremely cleanly, the burner is a blower unit with a short side wall stack.
  We have been using it since we built the house, about 9 years. Some comments- The heat is great, the themal mass in the floor is really nice when we lose power - the house can sit 5 or 6 hours and still be warm. Plus is takes almost no power to run the system, just a few watts for the pumps and blower. I would put in an air handling system as well, should I ever do this again, because it would be nice for humidity control and fresh air. One side effect of the side wall exhaust- the heating oil is full of sulpher- so the condensate on the side of the house is -yes, sulpheric acid and is chewing up my aluminum gutter and the galvanised nail heads. Also, the blower is noisy, I would use a draft system in the future.
 
 Anyway, I think a wood stove would be good , cause I have a steady supply of dry hardwood scraps., and I think the price of oil is going to go nowhere but up. And I already paid for the wood scraps! The stove I was looking at was a Scan, it had the soapstone sides. A very clean modern design- an old potbelly style or victorian look would be way out of place in this home.

[280plus]

Cool, you should be able to crank the buderus down pretty low then I guess. Depending on the model they can take pretty much cold water into the return and not suffer. +1 on the drawbacks of side venting. I hate that stuff. For the reasons you mention and the fact that IMHO there's too may moving parts and switches to depend on. Gravity is SOOO much simpler. I actually refuse to put them in and have turned away jobs where they want them. Regardless of the brand, soapstone is a good way to go. I am partial to those Vermont ones though.