Concrete floors with radiant

[Deleted]

So if everything goes as planned I'm going to start a building thread next week, but this question is begging an answer right now...

Would you buy a house with all radiant in concrete floors ? 

And how much in general do you think about resale when building? 

[ken a.k.a OMK]

Do you live in an area where it would be economical to heat the floors?

[zibazinski]

I've never seen that anywhere but bathrooms. Why is it that way?

[Deleted]

Radiant floors are supposed to be excellent and economical. The non concrete options for radiant are probably more energy efficient, but cost a lot more upfront.

We would build them that way Zib.

[GRG a/k/a goldenrulegirl]

Wouldn't that combo make repair and replacement difficult or am I misunderstanding how they fit together?

[Deleted]

Yes. If the radiant had an issue it would be encased in concrete so...

[teen persuasion]

Mar 16, 2016 21:31:45 GMT -5 GRG a/k/a goldenrulegirl said:

Wouldn't that combo make repair and replacement difficult or am I misunderstanding how they fit together?

Yeah, this would be my biggest worry.  I seem to remember This Old House doing some radiant floors, or looking at past trials with it, and saying that the earliest ones had problems with reactions between the metal piping and concrete.  Using modern PEX tubing might eliminate the issue, but how long has that been in use?

I like the concept of radiant heating and thermal mass in the concrete, but I also like adaptability and accessibility.

[teen persuasion]

How does it work on upper floors?  Is it just a thinset layer over the tubing on a traditional wood subfloor?  Or are you talking about in a full slab foundation?  Then again, I'm not used to houses on a slab, I'm used to full basements, too.

[GRG a/k/a goldenrulegirl]

I guess if it wasn't the only source of heat in a room I'd be down for toasty toes. And, that way, if repairs are too expensive/complicated, you can just not use it.

[Deleted]

Except for small loft space which would not be radiant, the house would be one floor. But the first floor would be over basement. Yes, 4 inch over subfloor.

The other issue is radiant concrete limits hardwood and carpet options. Again thinking resale.

[tskeeter]

Mar 16, 2016 21:30:17 GMT -5 oped said:

Radiant floors are supposed to be excellent and economical. The non concrete options for radiant are probably more energy efficient, but cost a lot more upfront.

We would build them that way Zib.

Based on my hundreds of hours of home construction research (watching home improvement shows), the most effective heat transfer method for radiant systems is to have a large mass of dense material, such as tile finished concrete, to transfer heat to the air.  That is the reason that when radiant heating systems are installed, the pex tubing carrying the warm water is often stapled to the wood subfloor, then encased in concrete.  Even if the concrete is subsequently covered with wood, carpet, etc.

[Deleted]

Actually the newest stuff I'm reading says thermal mass may be overload and the time /energy needed to heat mass requires much higher water temps for much longer than other options, and likely results in much less even heating... 

[tskeeter]

Mar 16, 2016 21:40:57 GMT -5 teen persuasion said:

Mar 16, 2016 21:31:45 GMT -5 GRG a/k/a goldenrulegirl said:

Wouldn't that combo make repair and replacement difficult or am I misunderstanding how they fit together?

Yeah, this would be my biggest worry.  I seem to remember This Old House doing some radiant floors, or looking at past trials with it, and saying that the earliest ones had problems with reactions between the metal piping and concrete.  Using modern PEX tubing might eliminate the issue, but how long has that been in use?

I like the concept of radiant heating and thermal mass in the concrete, but I also like adaptability and accessibility.

Replacing a radiant floor heating system would probably involve installing a hot water baseboard system.

[Deleted]

My parents have that in the entire lower level and the garage, it is awesome.  Except for one bedroom the flooring down there is all stone tile the same as I have, but theirs is always so cozy in the winter.  Mine feels cold and hard.

It's not their only heat source though, the other two levels don't have in floor heat.  They have a wood stove, a heat pump and a gas forced air furnace.  They like having options depending on what's cheapest at the time and back ups.

[Deleted]

There will be a masonry heater and fireplace as well... I think that's it?

[tskeeter]

Mar 16, 2016 21:45:35 GMT -5 teen persuasion said:

How does it work on upper floors?  Is it just a thinset layer over the tubing on a traditional wood subfloor?  Or are you talking about in a full slab foundation?  Then again, I'm not used to houses on a slab, I'm used to full basements, too.

The concrete used to encase radiant heat tubing is a light weight concrete, as concrete goes.  It has a lot of air whipped into it, much like whipping egg whites to make meringue.  You might have to beef up the house framing some, to support the additional weight.  But, radiant heating systems are often installed on the main floor of houses that have basements, so weight isn't a show stopping obstacle.

[Deleted]

Ok. Bigger question, if anyone knowledgable. The walls will be 6 inch concrete and 6 inch stone. Do I need radiant in that kind of mass? Will it really save a lot energy Wise? I think it would be more comfortable heat...

[tskeeter]

Mar 16, 2016 22:37:34 GMT -5 oped said:

Ok. Bigger question, if anyone knowledgable. The walls will be 6 inch concrete and 6 inch stone. Do I need radiant in that kind of mass? Will it really save a lot energy Wise? I think it would be more comfortable heat...

One of the primary advantages of radiant floor heat is that the heat stratification has the heat where the people are.  Warmest at the floor and cooling off as you approach the ceiling.  Other types of heating, it's warmest at the ceiling and coolest at the floor, where your feet are.  Radiant floor heating is also more evenly distributed throughout the house.  Forced air and hot water tend to create warm spots and temperature swings.  Swings in the range of 10 degrees between heating/cooling cycles.  Since cement heats and cools more slowly, the temperature swings aren't as pronounced and you don't have warm spots next to registers and cold spots elsewhere.

The rate of heat loss in your house will depend a lot on how it is constructed.  Solid, poured concrete with a stone veneer will transfer heat fairly quickly as compared to concrete block or poured concrete with a thermal break, or concrete with a thermal break under the stone veneer.  The thermal mass of the concrete and stone will heat up and cool down more slowly than some other materials, but an extended period of hot or cold weather will change the interior temp of an unconditioned building, regardless of what it is built of.  Remember, those great Flemish tapestries were used to help insulate the walls of stone buildings.

[marvholly]

I have an old family friend who built his place about 1960 w/this type of heat. He does have various types of floring including tile, linoleum & carpet.

To the best of my knowledge there has NOT been a big issue in all these years.

[wvugurl26]

Heated floors are awesome. I hate cold floors. My feet get so ice cold in the winter even with shoes and socks on.

[teen persuasion]

Mar 16, 2016 22:37:34 GMT -5 oped said:

Ok. Bigger question, if anyone knowledgable. The walls will be 6 inch concrete and 6 inch stone. Do I need radiant in that kind of mass? Will it really save a lot energy Wise? I think it would be more comfortable heat...

So 12" thick walls?  That's a lot of thermal mass, which takes time to heat/cool.  This will make temp swings slower, which may be good or bad.  If you want to warm up the house, it will take time to heat all that mass up.  You can heat the air inside, but if surfaces are cooler they will absorb heat until things equalize.  Same concept for cooling.  As long as you are prepared to keep a more or less constant temp, you are probably ok.

You can calculate how slowly/quickly heat transfers thru a given medium of known thickness.  No, I don't know the calculation, but it is out there somewhere.  Will the house be designed/situated to take advantage of natural heating/cooling?  Some people try to optimise the thermal mass/thickness to time when heat absorbed from sunshine reaches the interior: walls heat throughout the day, and warmth reaches the interior surface for night.  By morning walls are beginning to cool, but the sun is up to warm the interior thru windows.  Reverse thoughts for summer: overhangs shade windows to prevent daytime heating, deciduous trees shade walls, and night cooled mass cools during the day.

[GRG a/k/a goldenrulegirl]

(GRG is taking notes.  So many very bright people on these boards!  I may not know the math, but I LOVE the analysis!!)

[milee]

Mar 17, 2016 7:01:53 GMT -5 teen persuasion said:

Mar 16, 2016 22:37:34 GMT -5 oped said:

Ok. Bigger question, if anyone knowledgable. The walls will be 6 inch concrete and 6 inch stone. Do I need radiant in that kind of mass? Will it really save a lot energy Wise? I think it would be more comfortable heat...

So 12" thick walls?  That's a lot of thermal mass, which takes time to heat/cool.  

Our house in Phoenix was an old adobe house with 2' thick walls. The blocks to make the walls were made of the earth they dug out to make the basement, or they made the basement in the area from which the dirt was excavated... chicken/egg. It was interesting. And yes, it did stay much cooler in the Phoenix summers than did any other types of walls.

[swamp]

I have radiant heat in the new section of my house. It's under laminate.

I have seen too many instances of a problem with the radiant heat in the concrete to do that. If there is an issue, you have to tear up the concrete. If there is an issue with mine, you go into the crawl space, pull down the insulation, and there it is.

I like the radiant heat so much that I am considering putting it into the whole house.

[mroped]

Ok, these is how is gonna be:
- basement/underground structure built using ICF(insulated concrete forms) of 8" concrete thickness but the forms that you pour the concrete in are 2"5/8 thick on each side.
-first floor& gable ends are the same deal but in 6" concrete walls.
Estimated R value-43 so the walls are super efficient, super insulated. For those that understand the lingo- concrete is 3500 psi special mix with 5-6% entrapped air reinforced with no 4 (1/2") bar at 18" horizontal and probably 36-48" vertically.
Natural stone veneer-6" thickness will be placed just from grade to roof overhangs.mthat adds at least another R4-5 on it.

The floors
- basement is partially full- about 1200 SF from which 700 will have I floor heating.
- first floor- suspended on 14" engineered joists, ZIP wall subfloor, heat reflecting barrier - probably just a standard double bubble heat shield.
-PEX lining splitting zones for each room so it is easier to adjust accordingly.
The PEX lines will be attached to a 4x6 WW grid in 12" apart loops.
there will be a separate heating zone for each bedroom, one LR one kitchen and one for each bathroom so we will end up with about 9 different zones on the first floor. I will use the hallway for access in and out to each zone.
- concrete floor- 3 1/2" most likely 25-2800 psi with air. The floor will be sealed and dyed.

There is the possibility of having the concrete placed at diferent thicknesses as to accommodate for floor finishes - wood, tile but I'm still looking into it. In those areas I might eliminate the wire grid, set the PEX off the floor and place about 2.5" of concrete. That would give me enough room for floor finishes.
For tile you need about 1/2" and for wood about 1".
Just certain areas would be plain concrete then. But that option I'm still looking into!

PEX lines for in floor heating have been used in Europe since the 80s. For placement in concrete the PEX has a three layer construction with an oxygen barrier to prevent the chemicals in concrete from corroding it.
Once you have the lines in the floor, when the concrete hardens you practically have a continuous cavity going on so even if there is a pin hole in it, it could still be used in emergencies. Remember the fact the lines are not placed on the subfloor but floated inside the concrete mass. The heat barrier on top of the subfloor is placed as to reflect the heat from the concrete mass and direct it the other way.

Any suggestions on how it could be done differently or any questions as to why am I doing certain things.

I would love to do Warmbord, unfortunately that is an expensive option. Priced it yesterday at $7.59/SF for the board only and about another $1.50-$1.75 for the PEX and manifold. Then you have to think about finished floors too!

[8 Bit WWBG]

I stayed briefly in an apartment that had radiant heat under the floor and it was the most comfortable place I think I've ever been!  As was said, it's comfortable heat where you need it.  I slept so well because I wasn't having roasted air blown at me drying out my nostrils.  I am trying to remember what the floor was made of.  I wonder if it was tile.

And it looks like radiant cooling isn't too far off.  Oh man... if I never needed an HVAC again!

[Deleted]

So we decided to do radiant under floors, not in concrete, not warm board just make our own space something like this. I think it will be efficient enough for our needs.

[teen persuasion]

Would you do some kind of radiant barrier below, to reflect heat up where you want it, rather than also heating the basement incidentally?  What kind of finish floors?

[Deleted]

Oh yep, should have mentioned that an aluminum sheeting like reflective barrier underneath. Mix of flooring. No carpet. Hate carpet. Wood can go right over, tile would obviously need a thin additional subfloor... Or alternately we could groove and sink tubing under and section we wanted to tile...

[8 Bit WWBG]

Oh man, you're making me jealous!