Open system for hydronic rediant heat ?
I am considering radiant heat for a family room. I believe it would be basically simple to use electric mats, under the tile or under the flooring I’m not sure? I have began to look into it and am seeking some comparison between the long term cost of electricity (knowing how inefficent it is) and hydronic heated by natural gas. It gets difficult given the peaking cost of gas in the heating and the fairly satable cost of electricity. Aside from that, I understand there are extra benefits in using hydronic in an “open system” as cold water can run through in the summer cooling the floors. Has anyone used an “open hydronic system” and can give me any idea of costs or problems involved. Are there any studies, government or otherwise, that might compare the different systems.
Thanks, Pat
Replies
Is this new constuction or retro-fit?
What kind of heat do you have in the house now?
Do you need a new water heater anyway?
Sometimes you're better off, if you just need baseline floor heat, to go electric. That's if the existing room is already heated and you just want some extra comfort.
How much do you pay per Kwh?
On the cooling side, most of what I've read says that a cool floor in a hot humid envoronment will also be a wet floor. Depends on the temperature of the in-coming water and the relative humidity of your climate on a summer day.
Edited 1/28/2004 10:05:29 AM ET by johnnyd
"of electricity (knowing how inefficent it is) and hydronic heated by natural gas."
Actually electricity is almost 100% efficent.
While gas heat is about 80-92% and then slightly less after you factor energy and losses to circulate it to where it is needed.
"I understand there are extra benefits in using hydronic in an "open system" as cold water can run through in the summer cooling the floors."
Unless you are in a very dry climate, the desert S.W., you can't get much cooling with getting condensation on the floor.
IMO, open hydronic systems are potentially dangerous. The potential problem is stagnant water, combined with the ability of PEX to support a bio-film.
This is the same logic that has been applied in codes that disallow a long 'dead leg' pipe on a potable water system. No circulation leads to nasty stuff growing. Will fresh water regularly circulate through every zone in the summer? How will you ensure this? Open systems are actually illegal in some areas.
While the scientists and other experts argue about the health risks, I would suggest paying a little more to add a heat exchanger.
As mentioned, running uncontrolled cold water through a 'heating' system will cause condensation at the dew point. You could get wet floors, buckled floors, or even mold/mildew.
I was disappointed by the article in the latest FHB that shows an open system with no comment. This is not the industry accepted 'best practice', just the approach advocated by a certain vendor.
Wow, thanks guys for the quick responces. The wet floor might be an issue, a good point, given that we intend to tile the floor and have a rug in the middle. I could see a possible mildew issue here.
There seems to be debate on the efficency of electricity?
I heat my home with a forced air natural gas furnace and condition with electric central air.
Thanks again, Pat
Once the electricity is at your house, it's 100% efficient, what you're referring to as inefficiency....coal/nuclear plants with BIG infrastructrue, inefficient delivery systems, monopolies etc.... I don't have an opinion on that, BUT,
Whether to go for natural gas hydronic or electric radiant still has alot to do with whether this is NEW construction or existing...will this family room be an add-on or is it already there? in the basement?
If an add-on, what kind of construction? This is important because the heating system you choose will have a bearing on the design of the family room IF you are adding on.
If the room is already there, the design of the heating system needs to take into account the design of the existing space....on a slab, over an accessible crawl space or basement, will door threshhold hieghts be a problem if you put a hydronic in over the subfloor, etc etc.
Thanks for the help guys. I would like if someone knows of any study on life expectancy of electric radiant mats, in general, or manufacture to manufacture comparison.
Edited 1/28/2004 5:41:41 PM ET by Pat
If you can easily get to the joist spaces, why not consider staple up hydronic tubing (like PEX) with or without aluminum plates? Then add a new HWH dedicated to the hydronics, or tap into your current HWH. Plates, manifold, circulator pump, valves, etc.
There are some really good threads on all this forum via the search function.
Edited 1/28/2004 1:48:07 PM ET by johnnyd
EFFIECENCY has a very simple, but exact definition.
It is the amount of useful energy that you get out of a system compared with the amount of energy that you put into it. It is as simple as that.
With electrical resistive heating you get all of that energy out that you pay for except for a minute loss for any wires that might be run in uncondicitioned space. It does not matter if it is in the form of infloor radiat heat, baseboard heat, or an electric furnace.
With a gas furence you only get 80-90+ percent of the energy that is put into it and the remainder goes up the vent in the form of waste heat.
You can get the efficency of the "raw" energy sources to useful heat in the house. But that is really not usefull for several reasons.
COST EFFECTNESS is a completely different animal. And that gets into two different parts. Operating cost and life cycle cost.
Now operating cost very "simple". Cost of fuel x the efficiency of the system. The "simple" part is trying to average out swings in the fuel cost and predict where they are going to be in the future.
Life cycle cost incude the cost of purchaning the equipment, installing it, and maintaining it.
Electric resistive heating is very cheap in equpment prices.
Then you get into how is the space going to be used. If you want to maintain it 24x7 you will need a lot more energy than if you are only going to use that room once a week when you have company.
And it will vary if you can tap into existing hot water source or installing from scratch.
And to add confusion there are forms of electric hydronic heat. Heat pumps are used to supply the hot water.
FWIW department:
Electrical energy consumption in the US in 2003 (estimated): 3,677 billion Kwh
US electrical plant breakdown: 52% coal fired, 21% nuclear, 16% natural gas, 7% hydro, 2% oil, 1% other
For the first half of 2003, average retail price of electricity in US was 7.16 cents per Kwh
Of the total energy inputs into the electrical system it was estimated that in 2000, 66% was lost in energy conversion, 3% was lost in transmission, and 31% was consumed.
From US DOE figures...
http://www.eia.doe.gov/emeu/cabs/usa.html
http://www.localpower.org/pdf/wadebrochure1.pdf
60% lost in the [overall] distribution has been widely quoted.
That is one of the reasons why we are seeing more and more heavy users like grocery stores and warehouse clubs going to small onsite natural gas generators.
Some believe that the technology will soon exist to make extremely efficient electric generators scaled for individual homes, rendering centralized generation obsolete.
Sounds too good to be true, so I'm skeptical.
I can't remember what thesethings are called, power pac, energy pacs, something likethat. Small hydrogen generators which use hydrogen and oxygen and catalyze them to create energy and water. It is said that soon cell phones will be powered by these things. Ahnald has a Hummer powered by one. Should be smaller than a Munchkin boiler and produce extremely efficient and cheap electricity.
Stef