radient heat floor in basement slab - suggestions? learned opinions?

[Mia]

We are still building our hillside home, with the walk-out basement to the west.  The basement walls were poured about 6.5 years ago.  House was all dried in about 3 years ago, we have electricty run to the house & plumbing roughed in.  (a little more than roughed-in - we have a working toilet, hot & cold running water, shower, working kitchen sink)

Basement is still dirt & gravel.  I hope we finally get the slab poured next summer. 
My husband & I talked about having radient heat in the basement slab.  He thinks that would be an efficient & thrifty way to heat the whole house, since heat rises.  The main living area is upstairs.  We could put vents in the upstairs floor & could incorporate fans to circulate the warm air upstairs.

I am not convinced that it would be efficient, or thrifty.  If we had generous winter sun (we do have good southern exposure), we could use solar heat to heat the liquid in the tubes in the floor.  But we have very little winter sun in the Northwest, so we would have to use an electric water heater.  Electricity isn't cheap.  (Don't suggest natural gas, no gas lines in our neighborhood.)  So I am not convinced that heating the basement floor will keep the upstairs comfortable.

Anybody have any experience or advice to share?   Thanks.

[MountainDon]

Are there any local examples of radiant installations that work well?  Ones that don't work well?

[Mia]

There are a few homes with radiant heat floors.  I read a newspaper article about one a few years ago.  But in that home the slab was the main floor.
I suppose I could do a Google search to find out about radiant heat floors around here. 
I am just trying to figure out if heating the basement floor is going to make the upstairs comfortable.  Installing the tubing will be a lot of work & we have to do it ourselves cuz money is running out.  And we are in our early sixties - some hard work is a lot harder than it was even 10 years ago.

[MountainDon]

I'm no means an expert on radiant floors. However, I have to wonder about the efficacy of using a basement floor to warm the upstairs to a comfortable level. Somehow does "feel" right to me.

[Mia]

That is my thought too.  I don't think that putting a radiant heat system in the basement slab would be the best use of our time & other limited resources.  Now I just have to convice my husband!
We do plan to have a woodstove in the main living area.  We have heated with wood for years in our house in town (Portland).  And we'll take advantage of passive solar heat when we can.
Maybe we'll have a propane furnace someday.

[Native_NM]

Don't rule it out completely.  Pex is pretty cheap and adds little to the cost of the pour.  I saw an article on a system that was used as a supplemental in a similar situation.  The radiant system was designed to lower the total load required.  There is an article floating around on a cheap solar batch radiant system.  It uses pex, two old water heaters and some black paint and an old sliding glass door. The system heats the slab to a constant temp which doesn't keep the house toasty but reduced the wood required substantially.  It might be on YouTube.  A roll of tube is $130; cheap alternative. 

If you can pour the slab with the pex, you can come back later and add rest. Just a thought. 

[Native_NM]

One more thought - my cousin in Alaska has no hot water system other than a recapture system off the stove.  It's copper tubing and an insulated copper tank. A lot of heat goes up the chimney that can be captured.

[JRR]

......, since heat rises.  ......

That's a familiar old, but misleading, statement.  Heat does not only "rise", it goes in all directions.  (From any mass that is above absolute-zero temp.)  And it goes equally in all directions unless something hinders the flow.  So unless there is some intervention, such as insulation, there is a good chance much of the radiant slab heat you pay for will go downward into the earth.  I would think a slab, followed by a vapor/gas barrier, followed by rigid insulation ... with the flooring and radiant system atop all of that ... is the way to go.

The old adage would be more accurate if written; "Heated air rises".

[NM_Shooter]

This would not be a great way to heat the upper floor.  There is just too much thermal sink in the walls of the basement as well as in the walls of the floor above. 

You could heat the room above by doing this, but it would make the basement area uncomfortably hot. 

[Canvasman]

I can't say you will heat the whole upstairs. It will make the floor warmer, and if you wish to use basement will make it comfortable also.
Picture of my slab, you must put foam board down, high density, laying tubing not hard, unroll it not pull off coil.

Eric

[mgramann]

If you don't plan to use the basement as a living area, you would be better off adding the pex directly to the underside of the 1st floor....

...but, as others have said here, it isn't too much more to add pex to the floor-it's the insulation underneath that gets pricey.

[Mia]

Thanks, all.
Native_NM, I will look for the article on the solar batch radiant system.  Maybe Mother Earth News also will have some information.  We aren't planning to use the basement slab to actually heat the upstairs, just to reduce the amount of firewood we need to use, like you said.
I think that we could not get away with recapturing heat that goes up the wood stove chimney.  Local codes are pretty strict about wood stove chimneys.

We will use the basement rooms, undecided how.  Basicly 2 big rooms.  The north room will probaby be a wood shop.  or motorcycle shop.  south room could be the library, maybe, or a gathering room.  or a guest room.  or all those uses, probably at different times.

So, I expect that we will put insulation under the slab & pex tubing in the slab.  But more research is required.  (We certainly wouldn't heat the slab without insulation under it - we know better than that!)

[flyingvan]

Have you considered something like this?  I don't know how much southern exposure you have, but this is more direct and passive way to use solar heat.http://www.northerntool.com/shop/tools/product_200328805_200328805

[John Raabe]

Using a heated basement slab to heat an upper floor is not a good idea and would be very expensive to run, especially with a resistance electric water heater or boiler. Basements are almost always best zoned differently from the main living floor. Often it even makes sense to insulate the upper floor joists, especially when there are no living spaces in the basement.

If you are all electric you might consider installing a mini-split heat pump, especially if you will have an open style plan. This might work well on the main floor. Your proposed uses for the basement rooms suggest easy on/off heat for the times they will be used. Electric resistance wall heaters or water filled baseboards come to mind.

PS Mia: You may want to edit your profile and take out the Yabb reference. You can put in your general location so we know something about your site.

[Mia]

Thanks for the info.
John, I do like that mini-split heat pump.  We will look at doing something like that when we have more money.
Just the woodstove in the mean time.  Well, we will have 3 or 4 wall heaters, I don't think the county will let us have just a wood stove for heat.
The main living area, the upstairs, is about 1170 sq feet, pretty much open.
I've got to send some pix one of these daze.  But it always takes me a long time to figure out how to send photos & we are busy building now.

[John Raabe]

We heated with our wood stove for over 25 years - well there was an electric resistance furnace installed for code but that could cost $300/mo to run. We also ran space heaters and wall heaters in more remote parts of the house (still do). But now that we have the mini-split heat pump our power bill is running about 15% less than last year and we aren't spending $400-500/yr for delivered wood. When I was younger and loved cutting, splitting and stacking wood the stove was pretty inexpensive, but not the for last 10 years as my hair turned gray.

I don't know about your OR utility, but our WA state Puget Power company gave us a $1,200 rebate check which lowered the installed cost to under $3,700.

PS - About posting photos into forum threads. If you have a smart phone with a data plan and a camera, there is an inexpensive app that will post photos directly from your phone/camera into the forum post. See http://countryplans.com/smf/index.php?topic=10503.msg164039#new

As more and more people get capable phones this will be much easier and faster than the Photobucket type work around we have now.

[Rob_O]

I expect that we will put insulation under the slab & pex tubing in the slab.  (We certainly wouldn't heat the slab without insulation under it - we know better than that!)

I found some good information on pouring a slab floor here http://www.buildingscience.com/documents/information-sheets/slab-edge-insulation. Isolate the slab like they show in Figure 2 and the heat you put in the floor doesn't get bled off to the earth-