Radiant Slab or Stemwall/Crawlspace

[Believer]

I can't decide between these alternatives for my Kansas timber frame.  I like the radiant and passive solar heating aspects of a slab on grade.  I also like the aesthetics of wood floors.  I would enjoy reading other's experiences of slabs and crawlspace/wood floors.  I'm not considering a full basement because of the site conditions.  Also, I'm not planning any ducting for AC.

[Thehardway]

Believer,

There are advantages/disadvanteges to both.  I built a 24"D X 20"W footer above grade, (just removed sod/topsoil), then infilled with gravel.  I then leveled the gravel,  installed 2" of EPS over the gravel placed a 6" square mesh grid on the foam, tied 1/2" Pex to the grid with plastic zip ties and then poured a 5" floating slab.  The exterior walls (ICF) sit on the footer rather than the floor.  I then backfilled around the exterior of the footer to get it below frost level.  This got me above the surrounding grade for drainage and gave me a massive amount of thermal bank under the isolated floor.  We did porcelain tile floors over the slab on the first floor.

The disadvantage I found is that there is still a need for AC in the summer and dehumidification in the winter (to keep windows from sweating) which can not be accomplished with the radiant floors.  I met this need with a ductless mini split heat pump and a dehumidifier.  My heating loads are very minimal.  I don't as of yet have a good economical source for heating the water for the radiant floor system although I have experimented with using my domestic hot water heater.  The radiant floor heat is much more comfortable than a ducted forced air system.  The ductless HP system is much more efficient than a central A/C system.

I am not a big fan of crawlspaces.  They lend themselves to cold drafty floors. The only virtue they have in my mind is accessibility and even that is questionable.

With a floating insulated slab, there is no reason you can't do hardwood or wood laminate floors.  If I were to do it over again, I would consider floating slab with wood floors and a high velocity air system (mini ducts in concrete) in conjunction with a DX Geothermal heat pump.   This eliminates metal ductwork and insulating them. It provides warm floors and a method of circulating air and is ultra efficient.

[LittleJohn]

BELIEVER

There is no reason you can't put wood floors over a radiant slab; you just have to be careful and watch your water temps.  Gerenally you don't want the surface of concrete to hot or it can warp the floors.

In regards to excessive moisture, it can happen in any radiant system; GARAGES IN WINTER, are the worst snow melts off car and stays in air unless vented or dehumidified

[sprucebunny]

I have a radiant isolated slab 6" thick downstairs (all garage and entry) and radiant floor with vinyl on it up stairs (living area). I have a real furnace. It worked great until the price of oil got too high. Now, I run it once or twice a week for 4 hours and have a woodstove and air circulation system. The mass of the concrete floor will absorb heat from the air.
Personally, I would not want wood floors over the cement because of moisture and expansion issues but I'd put the same vinyl wood-looking planks that I have upstairs on cement. Or tile or flagstones.

I would not have a crawlspace. It offers no mass and they are hard to work in.

[Thehardway]

Believer,

If you can give us a littel more info about the area and climate you are proposing to build in, what type of building envelope you plan to build it, and if it will be occupied all the time, that would allow us to give more specifics.  Thermal mass can be a wonderful thing unless this is just a weekend getaway/vacation home.  Wood can be Used over concrete as mentioned but due to the poor conduction of wood it is not terribly efficient as a radiator over concrete.  That doesn't mean it is impossible or can't be done it just requires more thought and attention to detail.

[Believer]

Well the location is east central Kansas, about 50 miles north of Wichita.  I plan on small  timber frame that we will live in, retired. I think the climate is referred to as mixed humid. Thinking now I'll wrap, strap, and live edge lap.  Haven't decided on the roof yet.  I really want to do a green roof (engineered soil and planted), but that requires a low pitch so I'd give up any second level.  I also want to put Rumsford fireplace in and a wood cook stove in the kitchen.  I'd like to build this myself, not all of it but as much as I can do physically and skillfully.  I was going to ask, Hard way, if you could describe your envisioned high velocity mini ducts in more detail, I.e., a system description.  Thanks

[Holmes]

 A masonry heater will give better heat for a home than a rumsford fireplace.

[WmFritz]

A masonry heater will give better heat for a home than a rumsford fireplace.

I agree... one of these gives off some great heat and fairly inexpensive to build.

http://www.permies.com/wood-burning-stoves.html

[Thehardway]

Well the location is east central Kansas, about 50 miles north of Wichita.  I plan on small  timber frame that we will live in, retired. I think the climate is referred to as mixed humid. Thinking now I'll wrap, strap, and live edge lap.  Haven't decided on the roof yet.  I really want to do a green roof (engineered soil and planted), but that requires a low pitch so I'd give up any second level.  I also want to put Rumsford fireplace in and a wood cook stove in the kitchen.  I'd like to build this myself, not all of it but as much as I can do physically and skillfully.  I was going to ask, Hard way, if you could describe your envisioned high velocity mini ducts in more detail, I.e., a system description.  Thanks

Here is a link to a website should tell you most of what you want to know about mini-ducts or High Velocity ducted systems. http://spacepak.com/small-duct-high-velocity-central-air.asp

I would envision placing ducts at floor for heating in winter and at ceiling for cooling in summer. This could be done under slab or in wall. the ducts are about 2" in dia" and are flexible tubing.  This should work great in Kansas. What are your power rates like?

A Rumsford is nice if you like enjoying an open flame but they can be a bit tricky to build and get right.  If your house is built tight, you will need to supply make up combustion air for any type of indoor wood burning. Failure to do so will cause smoking, creosote buildup and other issues worst amongst them oxygen depletion and possibly death.  Also chimney construction, location, height and sun exposure can impact the quality of burn be sure you are well versed or advised.  Old timers did not have tight homes so the consequnces of their actions were not as pronounced.  Life was simpler but you had to chop more wood and wear your long johns and sleeping cap to bed.

A masonry heater is a good option and can be cheap or expensive depending the route you go.