Radiant in floor heating

[Jochen]

What is your experience with radiant in floor heating systems and what kind of systems do you use/recommend to heat the water-glycol based medium? And does it make sense to have such a system in the basement only and use otherwise a wood stove on the first floor?

Jochen

[n74tg]

My limited experience involves several visits and several hours spent at a house in Alberta, Canada that had in-floor radiant heat. 

I wasn't particularly impressed with in-floor heating as, at least to me, the feeling of being warmed from the bottom-up felt weird and fairly uncomfortable.  It was as if my feet were quite warm; in fact, too warm; such that we all had to wear house shoes at all times, while at the same time everything else on me was of more reasonable temperature.  But now, as I think about it more, all of me was probably too hot.

Now, as this was Canada, in the winter, outside temp probably near 10 degF, a couple of feet of snow on the ground, they may have just had the inside temp too high ( I don't remember seeing a thermostat).

It also may have been (at least partly) that this in-floor system was a home-made system consisting of radial rings of PVC embedded in the concrete slab.  As the house was octagon shaped most of the radial rings went thru multiple rooms.  Granted they did have a manual manifold & valve system to control individual rings. 

But, hey, I was only there for a couple of hours on each of two visits, so I was in no position to modify any temp/valve settings in an attempt to make it more comfortable for me.

Hope this helps.

[JRR]

I have friends near Torgau Germany who have built new houses that have radiant electric-fueled hot-water systems.  Have spent some winter days and nights in both homes.  Very comfortable.  The individual heating loops allowed different temps in various parts of the house.  A bathroom was usually kept near sauna-like (mostly for my wife), the bedrooms comfortably cool, while the main living area was usually moderately warm ... one of the guys had built his own glass enclosed fire place and was proudly using it to cheer up and warm up the living-dining area.

I studied one of the water heating/distribution systems in one of the two houses.  I think both houses were similar.  There was a utility room that was filled with the potable hot water system and the separate radiant heat hot-water system.  The electric water heating system seemed to be patterned after systems that used other fuels:  One main "boiler", a myriad of pumps and control valves, a pre-mixing chamber for each loop (to dilute the hi-temp water to a controlled temp), and a high-tech house-wide programmable controller ... to my mind, all too much overkill and unneeded expense.

I would expect a more effective approach, is to take advantage of the unique nature of electricity (a very controllable fuel requiring no combustion venting).  I see each loop having its own small(er) electric heater, one pump, one simple thermostatic controller, NO control valves ... NO premixing, each loop heater is used only when its loop has a demand, and shuts off when the loop temp set-point is reached.  This should be much less cost to install and operate as there is no central high costing, energy wasting, boiler.  Very high water temperatures need never be reached, this should save a bundle!  If convenient, the heating units and pumps could all still be centralized ... or, they could be distributed ... whatever the planner wants.

BTW, I recently saw in Costco some small hot water heater pumps and timer controllers ... the type that are used to distribute potable hot water around the house ... making it instantly available at the tap.  This pump system could be useful for radiant heat systems, I believe.  Just over $100, IIRC.

[brian_nj]

I have installed all types of radiant heating systems through the years. Everything from standard baseboard to in floor systems. I would say that 90% of the owners that I have dealt with who are not happy with their system are that way due to poor installation practices by their contractor. Over all a radiant heating system is in my opinion one of the best solutions out there especially if you can offset its energy consumption with solar collectors. There are a couple of questions I have that will allow me to give you better answers.

1. What state is the home being built in (climate reasons)
2. Is this a full time residence or vacation home?
3. Do you plan on having air conditioning in the home?


As far as heating the water/glycol mix which is only needed in cold climates or when the system will be turned off for prolonged periods of time in winter the only option I would suggest is a true boiler (not a hot water heater) The glycol mix is hard on components and greatly shortens their life expectancy. Most modern boilers are available with stainless steel heat exchangers which will slow the corrosion considerably (it will not stop it) The glycol is also verry tough on the circulator pumps and their seals.

If you have any questions I would be happy to help.

[Jochen]

.... There are a couple of questions I have that will allow me to give you better answers.

1. What state is the home being built in (climate reasons)
2. Is this a full time residence or vacation home?
3. Do you plan on having air conditioning in the home?

If you have any questions I would be happy to help.

Brian,

Thanks so far,

1. We are building in Nova Scotia/Canada. So it can get really cold over extended periods.
2. The house is planed as a full time residence
3. And absolute no air conditioning is planed. There is simple no need for that.

We will built John's Solar Saltbox which has a 24' x 36' footprint. And we are planning to built it over a full basement. Basement walls will be built out of ICF's for added insulation value.

Jochen

[JRR]

Comfortable room temp is somewhere in the 60F's or 70F's ... depends on the person.  No one needs boiling water temperatures in the radiant floor loops ... so why the "boiler"?   (OK, OK, I understand the rationale for a boiler if the fuel is wood, coal, oil, gas, etc, etc ... I just don't understand "why a boiler?" if the fuel is electricity.)

I've got an old 1970 six cylinder Ford truck that demonstrates that a regular steel impeller pump can last quite a while in a (Prestone) ethylene glycol solution ... as long as the water temp is not "boiling".  If the temperature of the water never exceeded , say, 100F ... any common metal would last a very long time in a Prestone solution ... ethylene or propylene.

But if we could accept a heating system that operates at such a "low" temperature ...no longer needing "boiling point elevation" offered by auto antifreezes  ... would we need either gylcols, or even methanol??  ... why not corn whisky?  Keeps me rust-free.

I realize that I need to install my own low-temp radiant system to prove (or disprove) my theory ... and I have begun the task.  If I can just ever finish the thing!

[brian_nj]

JRR

Your thoughts are valid on the low temp radiant floor system and they are done all the time (mostly solar collectors) The problem with the antifreeze used in home heating system loops is it is polypropylene glycol. while it is a lot more environmentally friendly it is also a lot more corrosive. The normal home boiler heating system runs in the 160 to 180 degree range so the antifreeze is not used to raise the boiling point at all. It is there for freeze protection. I agree the old automotive antifreeze could and has demonstrated that it will last a long time in a system the problem from a home system is that it is against EPA regulations to use it in that application.

As for electric heaters used to heat the home I can not recommend this in any climate. It is the most inefficient form of heat generation out there. It also has the least possibility of being able to supply heat to the home in a power failure or other situation where having a remote cabin might be of some use.

Brian
PS I like the wiskey idea for the loops but I might have a problem with running the loops dry by consumin my heating source

[brian_nj]

1. We are building in Nova Scotia/Canada. So it can get really cold over extended periods.
2. The house is planed as a full time residence
3. And absolute no air conditioning is planed. There is simple no need for that.

We will built John's Solar Saltbox which has a 24' x 36' footprint. And we are planning to built it over a full basement. Basement walls will be built out of ICF's for added insulation value.

In your region I would take a couple of precautions with a boiler system. The first is I would make sure to go with  Grundfos or Tetco stainless steel circulator pumps. they are a lot more corrosion resistant for the modern antifreeze solutions. I would also have who ever is installing the system add a control to turn the circulator pumps on in case of a flame failure (system not heating) as a added protection from the cold.  Being that you are going to live in the home there are less concerns with freezing as you will notice if the heat is out but we all like to vacation from time to time so better to be prepared. Also make sure your installer puts in isolation valves on both sides of the boiler so that the system can be purged of air with a pump and not just the little air traps that so many systems use. Air trapped in the system is one of the most common reasons for radiant systems to have cold spots.

Lastly I would recommend getting a refractometer so that you can test your level of protection at least once a year, with the systems installed today the use of auto fill valves is common and every time they add water to keep the system topped off they dilute the antifreeze a little and over time and before you know it you do not have the protection you think you do.

[Jochen]

Brian,

Again many thanks! I have another couple of month looking into the Radiant In-floor Heating Thing before we will start digging in May. Currently we are heating our two houses only with wood and love it! So Moni is only looking for a little bit more creature comfort while away and as a back up heat. If I can't convince myself I maybe just put the tubes in the slab and wait and see what will come up or cross my mind.

In Nova Scotia our Power Provider is offering a special rate if you use Electrical Thermal Storage Systems. And this include Radiant In-floor Heating as well. According to them, for in-floor hydronic systems, two 40 or 60 gallon domestic water heaters suited for space heating tied in parallel, with element sizes ranging from 4.5 kW to 6 kW, are often adequate.

Jochen

[JRR]

JRR

I agree the old automotive antifreeze could and has demonstrated that it will last a long time in a system the problem from a home system is that it is against EPA regulations to use it in that application.  [/i]

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I did not know this ... that the EPA restricts the use of ethylene glycol in home heating ... sad ... but it doesn't surprise me.  "Big Brother" looking after us!
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"As for electric heaters used to heat the home I can not recommend this in any climate. It is the most inefficient form of heat generation out there. It also has the least possibility of being able to supply heat to the home in a power failure or other situation where having a remote cabin might be of some use.

Brian "
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Since there is no waste combustion heat to go up the chimney in an electric system, it will actually be the most efficient.  However, electricity is for the home owner, the most expensive fuel in this country.  Not so, in some other countries ... but we excel in corporate/bureacratic greed and poor energy planning.  Point well taken about power failures.

[bobtheengineer]

As far as electricy goes, it really depends on what your electric rates are.  I know out here in North Dakota, we can get off peak for about $0.04/kwh.  You can't even touch that with any fossil fuel.  Off-peak electric is perfect for a radiant floor heat system.  Some people even use electric resistant coils, in the slab for heat.  There are also some other parts of the country where electricity is also pretty cheap, the northwest and the Tennessee Valley come to mind.  It all comes down to how much you want to pay.  Each service that you have into your house, costs money, whether you use it or not.  Yes, with electric you are out of luck, when the power lines go down, but you are also out of luck, with any furnace that uses electricity, propane, nat gas, fuel oil etc.. they all use electricity to run.

[MountainDon]

Yes, with electric you are out of luck, when the power lines go down, but you are also out of luck, with any furnace that uses electricity, propane, nat gas, fuel oil etc.. they all use electricity to run.

BUT, if you have your own standby generator you can at least drive the fan or pump every so often and keep everything from freezing.  That's a big IF, most folks do not have one, or enough fuel to run it unless it's natural or propane gas fired as well.

[glenn kangiser]

Big Brother and his grid friends will leave you shivering in the cold.

I'll stick with my woodstove.

[brian_nj]

Yes, with electric you are out of luck, when the power lines go down, but you are also out of luck, with any furnace that uses electricity, propane, nat gas, fuel oil etc.. they all use electricity to run.

Yes and no I can heat a home with a boiler system with no electricity using only natural convection. It is not the most efficient or even but it can be done. The system uses a thermopyle to create the DC voltage that the system needs to control the gas valve and safety devices in the unit. I would never recomend this option either. What I am doing is a thermopyle boiler with a  circulator pumps that are run off a small solar system each circulator only needs 84 watts to run and as long as a bypass is installed around the circulator pumps you still have the option to use it on no power (the pumps work like shut off valves blocking the natural circulation)


JRR - I think the good old boys in Washington have put their hands into way too much myself! And you are correct on the efficiency of electric being almost 100% and I guess that would make it a viable option in some regions.