Concrete House with Radiant

Ed Carr

Does anyone have experience with putting radiant in a concrete house? After extensive research, I'm planning on rebuilding my house (destroyed by fire this past Spring) using ICF (Insulated Concrete Form)technology. This is where the foundation to the roof eve is solid concrete that is poured into a preformed extruded polystyrolene form (except for window and door bucks that are placed in the form for rough openings). Concrete houses now make up 5% of the market and are virtually airtight (with blower tests in the .03 range compared to .78 on my old Victorian that burned). The energy efficiency of ICF homes are incredible, but I'm wary of how to size the radiant. Anyone out there have any practical experience with ICF construction?

Brian

ICF

Carl
I've done several ICF homes both Blue-Maxx & Nudura.As far as sizing the homes we are only allowed to use the R-value of the styrofoam (R-26) as apposed to the thermal mass R-value (45-50).If you use a modulating boiler then you will have your bases covered.

Good Luck
Brian

Jamie_6

Ed,

I have yet to do one but I do hope to. From what I understand, after the house has been assembled you have to place foam board down on top of all the floors, install all your radiant piping then repour concrete. As far as radiant tubing installation techniques it is quite simple.

Jamie

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joel_19

don't frett


My house is 13yold wood frame I think wood shood be banned as a construction material it stinks. I'd love a concrete and steel house. As my dad says, "You'll be able to heat that with a fart and a candle". It won't really matter much what you do. you could put the tubing 6" OC or 12 it will still work. Your hot water load will drive the boiler size more than the heat load.

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Constantin

ICF has a lot of promise

True, the homes are tight as a drum, have some thermal mass to keep things even, etc. Presumably, you've already selected an ERV or HRV to keep you healthy on the inside?

As far as the thermal load is concerned, the ICF construction is a bit like SIPs, I imagine. There is no question that vast areas of the stuff are impenetrable to air, etc. Yet the joints beteween floors, etc. is where I would focus my attention during construction because most homes are poured in a series of lifts, not all at once. IIRC, concrete should not be allowed to drop more than 4' within an ICF form or it may damage the ICF, rebar, or it may disaggregate.

Another thing to consider very carefully is infrastructure. Yes, you can carve out channels in the PS later but ideally, you'd route some of the bigger stuff in channels through the house before the concrete is poured. If it was my house, I'd have some large chases in the middle to carry electricity, heat, and cooling, etc.

My mums house in FL is concrete (though not ICF) and the visibility of infrastructure should be considered. Unlike traditional houses where you have 10-12" between floors to hide stuff in, concrete floors can be very thin due to the very high strength of reinforced concrete. However, any floor penetrations above will naturally appear in the space below (unless you install a dropped ceiling). Mum insisted on leaving the corrugated, galvanized zinc pour decks surfaces visible from below, which drove the infrastructure contractors nuts.

As far as sizing the radiant heat, if you're using PEX buried in concrete as it appears, then the standard ½" O₂-barrier PEX on 12" centers should do the trick. With up to 300' lengths, you should be able to minimize the number of manifolds you have to hide on the upper floors of your home. Furthermore, such a system will be capable of emitting far more energy per ft² than your house should be capable of losing.

So, as far as I am concerned, the transportation and emission of energy are not the issue, it's how you want to drive it. If you live in an area with city gas, a modulating, condening boiler makes the most sense. Mike T has shown some pretty amazing performance with his Vitodens, but other posts here from Munchkin, Ultra, and Trinity owners have also been ecstatic.

If you live in the NE and want to take a gamble with oil, a condensation- and shock-proof boiler like the Vitola makes a lot of sense. Or, you could go exotic and install a condensing boiler like the Monitor FCX. Either way, considering the tightness of your home and the efficiency of your insulation, you may find that there are few oil options small enough to be an efficient match to your system (i.e. where the max output of the boiler matches the design day needs).

Tim Doran

IFC & RFH

We have designed several of these and have had great success. As you are aware, the loads are very small and are very easy to accomodate. One issue is that the floors will not be as warm as they would be in a conventional home due to the decreased loads. Some planning as to traffic patterns and potential furniture placement may be useful. Once this is qusai understood a tube layout can be established to decrease the amount of heated floor which in turn increases the surface temperatures and gets us back to the warm feet that we all like.


Tim D.

S Davis

ICF Houses

I have done quite a few and have had good results they are getting very popular around the northwest, you will want to calculate your heatloss on actual R value not thermal performance, I have tried to get somthing in writing on their testing from ICF manufactorers and have had little luck, I do know that most of their testing was was done in areas that had large differences in day and nite temps to get the thermal performance that they claim.

S Davis


Apex Radiant Heating

Ed Carr

Thermal Mass vs. R Values

Thank you to everyone who responded. I read each of the posts carefully, and the consensus is to design to the R value of the 3" inside/3" outside (total of R-26) of the extruded polystyrene without consideration of the R-50 thermal mass of the poured walls. By the way, I was planning to use wood joists (manufactured truss lumber held by T-cos on a ledger board bolted to the concrete) w/ 5/8" ply as opposed to a poured concrete floor. I was planning to spray the underside of the joists with Icyrene (sp?) sprayed foam insulation after the bx wiring and plumbing has been installed. Does anyone see anything wrong with this thought process. Seems like I'll be living in a big styrofoam coffee cup surrounded by 100 cu-yds of concrete mass. From reading posts, biggest challenge will be having to size oil boiler since gas is not available in my area. Finding an ICF contractor is also a problem as Long Island seems to be totally behind the curve with this type of new construction (although Dan Holohan's hails from a town about 20 miles southwest of me, so I guess LI has some bragging rights) LOL.

--Ed Carr

Ed Carr

Concrete Home info

For those reading this post who are interested in ICF, here are two links:

http://realtytimes.com/rtcpages/20010424_concrete.htm

http://www.rewardwalls.com/resbuild/rb_home.html

--Ed Carr

Weezbo

this is a bit off center from the heating aspect...

it is somewhat important though...electrical wires have certain temp ratings in free air and another in conduit, be that nm emt ridgid whatever..when one applies insulating foam to these wire "Tubings"it changes the rating as often as i have pointed this out it doesnt seem to make a dent and people continue to foam over the conduit...well just thought id roll it by you . i seriously dissagree with foaming electrical Heat Tapes also..

[Deleted User]

Wiring in conduit

I would definitely run wiring, phone lines, tv, etc in conduit with extra wires and extra conduit. I've never seen a house yet, where something didn't need changed or upgraded, or added in about 3-4 years.

Constantin

You're right, of course.

Our electrical contractor couldn't believe the specs at first. However, given the huge heat resistance of Corbond (and to a lesser degree Icynene), heat management becomes very, very important. With petrified dino-juice in the walls, if they ever go up in flames, you'll maybe have time to put on a hat and walk out the door.

In our house, every room in the house has it's own circuit breaker for outlets. The wiring is 12AWG with 15A breakers and 15A outlets. The outlets are usually placed in 6 foot increments around the room (up to 12' is allowed by code). Installing lots of outlets with thick cables is cheap insurance.

The lighting circuits are shared on 14AWG wires between rooms, though only up to 50% of the rating of the wire. This was a concession to the electrician (and our wallet) as because working with 12AWG can be pretty tough.

The low voltage wiring was chosen on the basis of minimizing the possibility of running out of bandwidth. Granted, these days everyone seems content with wireless networks, and who knows what the future holds. However, I decided to cover my bases anyway and have a structural wiring bundle going into every bedroom, office, expected study area, etc. These bundles contain 2x Cat5e wires, 2x quad-shield RG6 wires, and 2x MM fiber-optic strands.

While I have successfully installed whole-house low-voltage systems on a number of occasions, I left this one to a pro because I didn't have the time due to job constraints and because I'm not familiar yet with installing fiber-optic connectors (from what I have read, field installations can be quite challenging). Not that I expect to use the fiber-optic ports anytime soon...

Another point WRT wiring is avoiding Aluminum wiring. Yes, it can (theoretically) be made safe, the stuff is cheaper than Cu, etc. but in my mind the reward is not worth the risk of eventual arcing causing a fire. Heat ratings can also be maximized at comparatively little additional cost, so why not do it?

Unknown

depending on where he is, how much glass he's got, and how he's installing the tubing.

even if it is low loss, and they mostly are, if it's a gypcrete pour for example with low R floor coverings he's got to stick to 9" o.c. or tighter to avoid heat striping, which is worst in systems with low loads.

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Unknown

where are you located? if your heat load calcs show a very load heat load (and they may), consider going with radiant ceiling to save $$$. if the load is low the floors won't be too warm anyway.

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JohnWood1

Two thing to consider..........

Biggest factor you change with this style of construction is air changes per hour. At a .5 ACH on most homes, this is 30-50% of the heat loss! SO; if you get to the .3 level, you will need a much smaller heat source.

If you want the warm floor effect in this home, try using as little tube as possible, but place it in the areas where you want to feel in on your feet. Kitchen, Bath etc. This way you can heat the home at a higer average water temp than you would if you had tube in every sq ft of floor.

And make sure you install an HRV for controlled ventilation! yer health depends on it.

Most of all have fun!

jw