Helpful? 0

Opinions on radiant ceiling heat?

I checked out a building yesterday that had heating mats like this one installed in four areas. Obviously it's electrical resistance heat, and there's an attic above so there's doubtless some loss into the attic, but these definitely make you feel warm, because your head is so close to the heat source. There was 1260 watts of heating installed in this area, along with 576 watts of fluorescent tubes. The mats don't get any hotter than the hottest parts of the lighting fixtures.

Any comments on this type of heating?

warm ceiling.jpg25.8 KB
Asked by David Meiland
Posted Tue, 01/31/2012 - 12:16
Edited Tue, 01/31/2012 - 12:16

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38 Answers

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1.
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David,
This type of heating has the same advantages of other forms of electric resistance heat, including electric resistance baseboard, electric mats under your tile floor, and electric resistance space heaters.

Some people prefer hot feet -- some people prefer a hot head. Everybody who uses this type of heat pays high fuel bills.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 01/31/2012 - 12:29

2.
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Dave,

Price Diffusers has a nice design guideline for using radiant ceiling panels on thier web site. You can get hot water panels. We often use them in small, outlining toilet rooms on commercial projects. I have never seen them in residential projects. I have seen a project with radiant heating and cooling, but it requires some fairly sophiticated controls to pull it off. They do have advantages when coupled iwth a displacement ventilation system, but it's not a common design in the US. Below is the link to the guidelines.

http://www.price-hvac.com/Catalog/Section_H/Radiant_Panels/RPM.aspx

Answered by Frank R.
Posted Tue, 01/31/2012 - 13:46

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Actually, electric radiant heat has all of the advantages of radiant heat and none of the drawbacks of convection electric heat as stated above. It's very comfortable and maintenance-free. It's also incorrect to state that you'll see higher heat bills. Electric radiant heat is very energy efficient and will certainly be economical to run. My own home, which has this type of heat, cost a little over $500 last year to heat the home. It's ~4,000 sq. ft. in a cold climate with lots of glass.

Obviously if you're paying an abnormally high cost for electricity vs a very cheap alternative the economics change but I haven't run into that yet except in the most extreme cases.

Answered by Steve Kilbride
Posted Mon, 02/06/2012 - 12:36

4.
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Steve,
Most parts of the country are paying about $1 a therm for natural gas. That's 100,000 Btu, or 29 kWh.

To make electric resistance heat competitive with natural gas, you'd have to have a rate of 3 cents a kwh. Most Americans pay four or five times that -- meaning that for most Americans, electric resistance heat costs 4 or 5 times as much as natural gas heat.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/06/2012 - 13:01

5.
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Martin,

I understand where you're coming from - it's a very common belief that you can equate a therm with the equivalent kilowatt and just multiply the costs to get a comparative answer, the truth is you simply can't. Radiant heat and convection heating are different approaches to space heating and they do not deliver the equivalent results. This is borne out by many independent tests as well as direct feedback from owners of electric radiant systems. There are many reasons for this. Some small, some larger, that when added together tip the scales hugely in favor of radiant heat. Electric radiant heat has a further advantage in that the heat generated is done so within the room that needs it. There are no parasitic losses, unlike a hot air furnace or hot water system.

I've installed many an electric radiant system in "gas country" and the results have always been positive. Alas, I've gone beyond the point of answering the Original Poster's question, and I don't wish to derail his thread. However I'd be happy to go into greater detail at another time, perhaps in another topic area that is more appropriate.

Answered by Steve Kilbride
Posted Mon, 02/06/2012 - 15:37

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Sorry, Steve, but a BTU is a BTU. You write that your theory is "borne out by many independent tests." Please cite a paper or study supporting your theory; I've never read one.

Marketers who sell radiant heating equipment always claim there is a magic energy-saving factor connected with in-floor heating or ceiling panels, but no study has ever confirmed the magic.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/06/2012 - 15:43

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Sorry, Martin, but there are plenty of studies out there. Here's the first one I ran across:
http://www.toolbase.org/PDF/CaseStudies/enerjoy_case_study.pdf

I have others, of course, but only in a pdf format. They, in turn, reference dozens of other studies. I can email those to you as I don't have a web-based link to share at the moment.

Cheers,
Steve

Answered by Steve Kilbride
Posted Mon, 02/06/2012 - 16:15

8.
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Steve,
A quote from the study you linked to: "Because a portion of the energy savings with the Enerjoy system was related to room by room setback and the specific number and routines of the research home occupants, savings for other households may be different than those obtained in this study. ...
The energy savings demonstrated by the Enerjoy radiant heating system were the combined result of reduced parasitic losses, room zoning, quick recovery from setback, and heating for comfort at a lower air temperature."

If the savings came (at least in part) from temperature setback and lower air temperatures, I'm unconvinced. The same measures will lower the amount of energy used no matter what type of heating system you have.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 02/06/2012 - 16:29
Edited Mon, 02/06/2012 - 16:38.

9.
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Martin, my cautious opinion is that given a house heated to 68 with forced air and a house heated to 68 with radiant of any sort... the radiant will be more comfortable, because there's no moving air. A person with forced air will turn the stat up a little more to achieve the same level of comfort, using more energy.

Other than that, a BTU is a BTU.

Answered by David Meiland
Posted Mon, 02/06/2012 - 16:38

10.
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I agree with you David - sort of. Ducted-air systems (I prefer that to 'forced-air', which implies excessive pressure and velocity) need not have a wind-chill effect. Here in heat-pump country we learned a long time ago that low-velocity high-volume systems are the way to go, and they make for a great, easy to manage background system. Combine that with a nice radiant point source like a wood stove for cosy winter evenings and you have the best of both worlds. Kick the 'stat back to the mid-60's - who needs a hot bedroom? - and enjoy the extra punch of a focal heat source in the living room. But ceiling panel radiant? Not so much.

Answered by James Morgan
Posted Tue, 02/07/2012 - 10:20

11.
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Steve Kilbride, what do you pay for a KWH along with location and heating degree days? Superinsulated too? All rooms used or a few not? Your $500 would be impossible for me at 16 cents a KWH and I have just under 2000 sqft.

Sounds like you are doing well with your set up. $500 for winter heat is great.

Answered by aj builder, Upstate NY Zone 6a
Posted Tue, 02/07/2012 - 11:52
Edited Tue, 02/07/2012 - 11:58.

12.
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Martin-

If part of the energy savings was from setback savings, is that necessarily a bad thing? It's part of the advantage to having a radiant heat system like radiant ceiling heat where you can setback and turn the heat off and on much like a light switch due to rapid response times in the panels/array. ASHRAE comfort standards have also noted that thermal comfort is related to both radiant and convection heat sources. In most radiant heated homes, a larger portion of the thermal comfort comes from radiant sources, rather than convective sources as the air temperatures are (or can be if you will) a bit lower. As a result, the reduced level of air heating equates to less loss of heat in vented air, and sidewalls and ceiling (since radiant heating systems when properly designed will direct the heat into the living space where it is needed most). A well insulated room that utilizes radiant heating systems can save money over a gas system if used and designed properly.

Your claim that "A BTU is a BTU" is certainly true, but you said that in response to a point made that a "BTU is not equal to a KWh". If you look at a simple termperature response curve of a various radiant elements, you'll note that different efficiencies (measured in terms of radiated and convected J/KWh) can be obtained in via different designs. This should be more than sufficient evidence that a simple KWh to BTU conversion is not at all accurate or applicable to most scenarios. Again, there's a large difference between heating the same air mass (electrical vs gas central furnaces) and localized zone heating that relies more on radiant heat transfer than convected heat transfer, which is more efficient and is noted to equate also with higher levels of thermal comfort.

-Patrick Beebe-Sweet, MBA in Green Construction

Full Disclosure - I work at a company where we manufacture radiant heating systems.

Answered by Patrick Beebe-Sweet
Posted Tue, 02/07/2012 - 20:14

13.
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Patrick,
Most people don't want to live in a house with cold rooms that require occupants to turn on electric heating panels to get warm whenever they move to a different room. Especially since electricity the the most expensive fuel out there.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 02/07/2012 - 20:20

14.
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AJ Builder,

The $500 is based on 7 cents per kwh. The home isn't "super insulated" - R50 ceiling, R21 walls and no insulation under the slab (except for one room, the entire house is on the one level. And I have 400+ sq. ft. of glass facing north.

Answered by Steve Kilbride
Posted Wed, 02/08/2012 - 16:14

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Here's an excerpt from a paper I have (which references many other studies).

"B. Radiant heaters vs. convective heaters
Radiant and convective heating systems produce different thermal comfort environments and generally differ in energy consumption due to their nature of heat delivery or removal. Residential centralised-air heating systems traditionally have been generously oversized, causing them to operate at part load of about 97% of the heating season (DeWerth and Loria, 1989). To save energy, a centrally-heated home (e.g. warm air furnace or boiler) usually uses the technique of excluding or controlling heat for certain areas but this often results in uncomfortable areas of the home. In this case, one solution to increase the overall comfort and reduce energy consumption at the same time is to provide a source of supplemental heat to those areas being occupied at one moment and exclude or lower the overall supply of central heat. Residential in-space heaters were then introduced in the 1970‟s to solve the problem of energy shortage. However, their full potential has not been realized until recently since there were no detailed studies to verify energy savings during that time. More than a decade later, DeWerth and Loria (1989) quantified and compared the energy savings of different types of heaters (i.e. radiant: gas-fired unvented and vented; convective: vented and direct-vent) as supplemental (for centralised air-heating) or sole source of heat for 2 types of home: a 1950‟s home and a modern home. Results showed that the in-space heaters used less energy (gas or electric) than the central system, e.g. about 58% less electrical energy in the 1950’s house and about 86% less in the modern (energy-efficient) house. Comparing both radiant-type and convective-type in-space heaters showed that using the radiant-type saved more than its counterpart, i.e. 25% more in the 1950‟s house and 10% more in the modern house.

Numerous researches on radiant heating systems have followed then, mostly evaluating the advantages and disadvantages of this type of heating system and comparing with the traditional
convective heating system. In general, these studies proved that radiant heating systems offer the potential of (1) reduced heating unit sizes (due to reduced heat load and peak load), (2) reduced
energy consumption (Zmeureanu et al., 1988; Howell and Suryanarayana, 1990; Imanari et al., 1999; Petras and Kalus, 2000; Miriel et al., 2002; Feng et al., 2006) and (3) favorable tie-in
capabilities with low-temperature and low-intensity energy sources such as solar systems and heat pumps (Kilkis et al., 1995) (4) while maintaining acceptable thermal comfort (Imanari et al.,
1999). Compared to convective heaters, radiant heaters may be operated at a lower air temperature (Hart, 1981; Zmeureanu et al., 1988; Howell and Suryanarayana, 1990; Kalisperis et al.,
1990; Ling and Deffenbaugh, 1990) because the radiant heat from the heater falls directly (or indirectly through surfaces) on the occupants thus producing more comfortable conditions. This
means that radiant heating systems increase the mean radiant temperature (MRT; average room surface temperature) to which occupants are exposed, thereby allowing comfort at lower
temperatures. Thus, it is possible to maintain the air temperature by 5°C lower compared to classical methods at the same comfort level (Dudkiewicz and Jezowiecki, 2009).

On the other hand, a convective heating system produces an environment where the air temperature is greater than the MRT in space. For this reason, infiltration losses are greater than in radiant
heating systems (Hart, 1981; Zmeureanu et al., 1988) which is not favorable since air infiltration rate in a building is one of the significant factors affecting energy use and comfort (DeWerth and Loria,
1989). Moreover, there would be higher air temperature gradients due to the higher air temperature brought into the space which consequently gives higher temperature at the ceiling (due to the hot air‟s lower density) than at the floor (Howell and Suryanarayana, 1990; Ghaddar and Salam, 2006). Since the overall thermal comfort sensation tend to decrease with an increase in the magnitude of
environmental thermal non-uniformity (Sakoi et al., 2007), higher air temperature gradients can also lead to a lack of spatial uniformity of thermal comfort in the given space (Kalisperis et al. 1990).
Conventional systems that uses air as the transport medium has lower (maximum) potential for delivering sufficient heating/ cooling since it is limited to the thermal capacity of the air and its ability
to transfer thermal energy (thermal conductivity and air flow rate) to or from a surface (Ardehali et al., 2004). Thus convective heating systems typically respond slower especially to step (temperature)
changes (Berglund et a., 1982) and a rise in air temperature by 1°C could mean a 6% increase in energy consumption (Roth et al., 2007). "

Answered by Steve Kilbride
Posted Wed, 02/08/2012 - 16:18
Edited Wed, 02/08/2012 - 16:20.

16.
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Steve, Interesting info. My electric is over twice yours. So for here NG with radiant panels... and very small radiant pellet stove acting like your radiant panels...

Many interesting posts... enjoying the debate

Answered by aj builder, Upstate NY Zone 6a
Posted Wed, 02/08/2012 - 19:58

17.
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Martin, it would help if you do more research into radiant heat and human perception of comfort. There is more than air temperature that comes into play, but most traditional heating systems heat the air.

Example: Take two houses in the winter both heated to 68 degrees. Does a person experience the same comfort in both?

Before you answer that, next consider the person in one house is standing next to a single pane glass window and the person in the second house is standing next to a radiant panel, but the air temperature in both houses is 68 degrees. Now who is more comfortable?

Of course the person standing next to the radiant panel is more comfortable, which means you CANNOT just compare air temperatures and do BTU calculations based on electric and gas. The human body is a radiator and it is also a detector of radiant heat. You need to think about this as a complex system involving humans in order to answer the questions about comparing fundamentally different heating systems. It is NOT all about heating air. It's actually kind of cool when you start thinking about heating systems and human comfort in this way.

I apologize for sounding preachy but it might help if you check out this book: http://www.pexsupply.com/RPA-HydronicRadiant-Hydronic-Radiant-Heating-Da... I think it's also available on Amazon. I also suggest you get in touch with John Siegenthaler who is a guru in this area and he can walk you through all of the technical considerations. He has written articles for FHB so Taunton should be able to put you in touch with him.

This is his classic book on Amazon http://www.amazon.com/Modern-Hydronic-Heating-Residential-Commercial/dp/... Use the "Look Inside" feature on Amazon and read the First Pages. On the bottom of page 5 you will see that it says "Buildings with hydronic heating systems have consistently shown lower heating energy use than equivalent structures with forced-air heating systems."

Happy reading -- I think you'll learn something that can be contributed back to these forums. It would be great if John writes a blog post to generate a good discussion here.

Cheers,
Billy

Answered by William Geary
Posted Thu, 02/09/2012 - 00:00
Edited Thu, 02/09/2012 - 00:10.

18.
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As for studies showing that it is cheaper to heat a house with radiant heat, please refer to a Fine Homebuilding article printed in 1992. The article was written by the Research Chairman of the ASHRAE Radiant Heating and Cooling Technical Committee. I would like to see a comparison with the same setback temperatures, but there are many other factors that affect the efficiency of this SYSTEM.
Billy

See:
http://www.radiantec.com/why/technical-explanation.php

Partial quote:
"Studies conducted by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) indicate that with radiant heating systems people can be comfortable at temperatures 6°F to 8°F lower than with convective systems. Forced-air and baseboard (whether electric or hot-water) heating systems are convective systems because they use air as the primary heat-transfer medium.
* * *
When applied to the sizing of a radiant system, conventional heat-loss analysis often includes a reduction in design temperature from 70°F to 65°F and a 10% to 25% reduction in building air infiltration, exfiltration, stratification and glass heat loss. The average 65°F radiant comfort temperature with 59°F day/night setback should reduce building heat load by 25% to 35% over convective systems."

Richard D. Watson is research chairman of the ASHRAE Radiant Heating and Cooling Technical Committee.

Answered by William Geary
Posted Thu, 02/09/2012 - 00:22
Edited Thu, 02/09/2012 - 00:23.

19.
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Here's another study involving radiant ceiling panels:
http://oikos.com/esb/37/radiant.html

"Researchers at the NAHB Research Center found that heating a home with ceiling-mounted radiant panels produced energy savings of 33 percent compared to a heat pump and 52 percent compared to baseboard heaters. The research project, completed in May 1994, was sponsored by the U.S. Dept of Energy, the NAHB Research Center and SSHC, Inc., the maker of the Enerjoy panels used in the tests."

Billy

Answered by William Geary
Posted Thu, 02/09/2012 - 00:29

20.
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William,
First of all, your lectures about mean radiant temperatures and comfort are condescending. Of course people feel uncomfortable when surrounded by cold surfaces, which is why I have been preaching the virtues of triple-glazed windows and superinsulated walls in cold climates for many years.

Many of your observations apply only to poorly insulated, leaky buildings, rather than the tight, very well insulated buildings advocated on this website.

Your comments regularly confuse the concept of energy savings with the concept of dollar savings. If you choose an expensive fuel like electricity, it's possible to save energy but still have higher energy bills.

The main problem with your proposal -- to lower the air temperature setting of the thermostat and depend on electric ceiling panels to warm people -- is that people don't stay put, unless they are working on an assembly line in a cold factory (where radiant panels probably make sense). If someone is walking from room to room in a cold house, it's hard to come up with a control system for your method of heating.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 02/09/2012 - 05:41

21.
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Here's a brief study of assessing clains of lower thermostat settings in hones with radiant floor heat done by CMHC http://www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/01-106-e.html

They found slightly higher settings in the radiant heat homes and concluded:
"This research shows that homeowners with radiant in-floor heating systems do not set their thermostats significantly lower than homeowners with other types of heating systems.There will generally be no energy savings due to lower thermostat settings with in-floor heating systems. Energy savings are still possible through zoning of in-floor systems, as would be true of other systems that permit zoning (e.g. baseboards, radiators, etc."

Answered by Michael Blasnik
Posted Thu, 02/09/2012 - 08:34

22.
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Martin,

Why do you say this is my proposal? "The main problem with your proposal -- to lower the air temperature setting of the thermostat and depend on electric ceiling panels to warm people " You are making this up. Show me where I proposed this.

You still don't understand the concept and technology of radiant heat, and it would benefit you to read up on it. The fact that you equate electric radiant heat with electric resistance strip heating demonstrates an ignorance of the basic concept of *RADIANT* heat. You act as if people are concocting magic when they discuss radiant heat but standing in the sun on a cold day should provide ample evidence that radiant heat is fundamentally different from heating the air, and the fact is this method of heat transfer to the human body is fairly efficient.

Most radiant heating systems are in the floor, and last time I checked most occupants of a house are near the floor.

I am sorry this feels condescending to you, but the way you put down anyone who tries to explain radiant heat to you comes off as condescending and uninformed. Be open to learning.

And don't confuse radiant versus forced air heat with electric versus gas fuel supply. Depending on gas and electric prices a gas furnace is likely much cheaper to run than an electric furnace, and a gas boiler is likely much cheaper to run than an electric boiler for hydronic radiant. But you cannot compare forced air gas heat with electric radiant based on the cost of electricity and gas alone. It is not that simple minded.

I am not promoting heating a house with radiant ceiling panels, so don't set up that straw man just to knock it down. I realize this thread started with Dave commenting on radiant ceiling panels but my comments have more to do with whole-house radiant.

Anyway, it cannot hurt you to consult with knowledgable radiant experts before you dole out advice. There's no downside to that. I'm really not trying to start a Riversong battle -- just trying to shed some light where you are misinformed. (I might not have this totally right either, because this is very complex, but I am all for learning where I might be wrong. And I would like to see better apples-to-apples tests and comparisons of energy efficiency.)

Billy

Answered by William Geary
Posted Thu, 02/09/2012 - 09:30
Edited Thu, 02/09/2012 - 09:40.

23.
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William,
At no point have I ever confused electric radiant ceiling panels with electric resistance baseboards -- I know the difference. But I also know that both use electric resistance heating elements.

And yes, I find your assumption that I don't understand radiant heat -- whether from the sun, a wood stove, or one of your electric resistance panels -- to be somewhat condescending.

Michael -- thanks for citing the research from Canada.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 02/09/2012 - 09:43

24.
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Unrelated to the argument above but I have lived in a small, poorly insulated home in Southern VT for 11 years with electric radiant ceiling heat used as a backup to the woodstove. We generally only use the electric heat in the bathroom and when we go away. Or if heat loving relatives visit. Otherwise we keep it on 55 degrees to keep the house from getting too cold when we are at work. For this purpose it seems to be a simple and cost effective option and adds less than $200 to our electric bill per year. we have no heat bill other than gas for the 4 chainsaw.

Answered by Robert Swinburne
Posted Thu, 02/09/2012 - 11:17
Edited Thu, 02/09/2012 - 11:18.

25.
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Martin,

In your first post you said:

"This type of heating has the same advantages of other forms of electric resistance heat, including electric resistance baseboard, electric mats under your tile floor, and electric resistance space heaters.

Some people prefer hot feet -- some people prefer a hot head. Everybody who uses this type of heat pays high fuel bills."

Clearly you are confusing radiant heat (electric heat under tile floors) with electric resistance heating by lumping them all in the same category. Maybe you didn't intend to do so, but this is what you wrote.

I don't understand why you keep painting me as an advocate of using ceiling electric radiant panels as the sole source for heating homes. I am not. Maybe we are getting away from the initial topic, but just to be clear the focus of my comments are:

- radiant heating versus forced air heat to produce a given comfort level for human occupants
- comparing electric and gas on the same type of heating system is simple and easy, but it is different from the trickier question of comparing gas forced air heat to electric radiant heat
- apples-to-apples energy use comparisons between a home heated strictly with radiant heat and the same or "equaivalent" home heated with forced air heat -- by the way, the studies that have been performed by true professionals in this area are useful and instructive but it bothers me if they did not apply the same variables (such as setback controls) to each type of heating system.

I am looking for some truth here and am always open to learning new things. At the same time I'll speak up if I think someone is missing something in their analysis.

Billy

Answered by William Geary
Posted Thu, 02/09/2012 - 14:11

26.
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To David (if you haven't lost interest),

1. Electric radiant ceiling panels do fail, and I've also seen them partially fail. Now there's a daunting and expensive repair for you.
2. If anyone works at a desk, or maybe sits at a dining table, they might not be totally comfortable because their feet and legs will be cold.

Answered by Kevin Dickson, MSME
Posted Fri, 02/10/2012 - 20:39

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Kevin, still here and reading all with interest. In this particular installation, warm ceilings probably work great. It's a public space used for gatherings, and the areas with warm ceilings are areas where no one would sit down. The main hall, where the seating areas are, is heated via forced air.

Answered by David Meiland
Posted Fri, 02/10/2012 - 21:19

28.
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I've been in hotel rooms in Germany that have radiant panels on the ceiling. They are comfortable but I think floor heat works better. They may be good for retrofit.

Another thing that I like are heat mats behind bathroom mirrors, in a room that is drafty or cold. Warmly Yours sells them for mirrors and they are inexpensive. I don't know about the economics but you get a really nice warmth from them in the morning when you are shaving, plus they de-fog the mirror. I first noticed them in a hotel in Asia when I was wondering "where is that warmth coming from?!"

I put them behind the mirror in our master bath but we don't use them much because the walls are warm (good insulation) and the bath fan gets rid of the steam from the shower.

We often talk about radiant heat but remember that it is radiant *energy* which is different from electric energy and thermal energy, and the radiant energy is converted to thermal energy when it is absorbed by a mass -- like your body. Sorry for drifting off on a tangent...

Billy

Answered by William Geary
Posted Fri, 02/10/2012 - 21:58

29.
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Just noticed this discussion.
I live in a house with radiant ceiling heat in VT. It was built in 1970 and came with the house. THere is a different zone for every room. We use the bathroom zone in the winter but otherwise we keep it at 50 degrees and heat with wood. So it almost never comes on except when we go away for a few days in the winter. Just the bathroom affects our electric bill minimally compared to cooking and hot water. (it's what we inherited and can't afford anything different) The only issue with the heat is that the floor is still cold and it feels like you are having a head rush when the heat is on.

Answered by Robert Swinburne
Posted Mon, 10/29/2012 - 11:44

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Robert,
You wrote, "Just noticed this discussion...."

I beg to differ, Robert. You posted a similar comment on this page on Feb. 9, 2012. It was comment #24.

I know, I know... that was months ago...

Answered by Martin Holladay, GBA Advisor
Posted Mon, 10/29/2012 - 12:06

31.
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There you go again.

"Everybody who uses this type of heat pays high fuel bills."

Of course this statement is nonsense, but then, your prejudice against radiant heating, of any kind, should be obvious to the most casual reader of this otherwise accurate and useful site.

Naturally, there is no valid argument against raising mean radiant temperatures for comfort. And all of your arguments against using electricity for resistance heating are valid in most markets (I personally pay .045 cent/kW).

The question really is, how best to deliver that comfort? Radiant ceilings have the same effect in a current code built stick frame, as they did the the post war building boom when many homes (hundreds in a neighborhood here in Richfield, MN) used copper tubing embedded in the ceiling plaster. Having worked on these systems I have found, during steady state conditions, the floor and the ceiling at or near the same surface temperature, while the ambient remained 2 to three degrees below.

In one of our more recent design/build radiant systems we radiated the slab in the basement and the ceiling for the main floor at the same design water temperature - 110F° ,which of course modulates with outdoor air temperatures having an average design water temperature made for heat pump or condensing boiler. We used a condensing water heater for combined efficiency.

"Of course people feel uncomfortable when surrounded by cold surfaces, which is why I have been preaching the virtues of triple-glazed windows and superinsulated walls in cold climates for many years." "Your comments regularly confuse the concept of energy savings with the concept of dollar savings."

I agree with your first statement, but it is contradicted by the second. Since we have already exceeded building code and comfort expectations with a well insulated house and argon filled thermal pane windows, everything added subtracts from ROI and diminishing returns are the only guarantee. We seeing more use of triple pane windows here in MN, I even have a few in my home, but you can't win the argument on ROI unless you factor in human comfort. Just so with hydronic radiant heating.

By the way, I heated 2200 s.f. of well insulated living space last month (December) for less than $100.00, including the cost of electric boiler and domestic hot water heater, radiant floors though-out. This is not a high heating bill for Minneapolis.

Answered by Morgan Audetat
Posted Wed, 01/16/2013 - 14:21
Edited Wed, 01/16/2013 - 15:01.

32.
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Morgan,
If one's electricity rate is unusually low -- as yours is, at 4 cents a kWh -- there is little incentive to find an efficient way to use electricity. That's why you are happy to use electric resistance heat -- because your electricity is so cheap.

In most of the country, we can't afford to use electric resistance heat. Any homeowner that follows your advice may regret the decision -- especially if electricity rates in Minnesota ever approach the levels paid by homeowners in New England.

Answered by Martin Holladay, GBA Advisor
Posted Wed, 01/16/2013 - 14:33

33.
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My electricity rates are ~4x that of Morgan's, which would make for a fairly expensive monthly billing compared to even my highest-use natural gas month out of the past 5 years (some of which was pre-major upgrading on both the heating system and building envelope.)

When the delivery systems are similar a BTU is a BTU. Swapping in a condensing gas boiler for an electric boiler would indeed be far cheaper (and greener) for most of us.

Different systems have differing system-efficiencies- with differing fractions of distribution loss. The electric radiant mats have VERY low distribution losses (a few percent, mostly in the line to low volage conversion electronics). Hydronic systems also have pretty low distribution losses, and almost all of those losses accrue inside of conditioned space and are not fully "lost" during periods of real heat load, even if they're not heating the exact zone calling for heat. Only when the boiler and distribution plumbing are in uninsulated unconditioned space does that loss add up to much. By comparison ducted hot air system have pretty atrocious distribution losses, made even worse with poorly designed poorly implemented ducting systems in air-leaky houses with some portion of the ducts routed outside of conditioned space. A worst-case hot air system could be running under 50% net efficiency due to high air-handler-driven infiltration. But even a gas-burning 50%-er would not make electric radiant mats a more cost-effective solution in most markets. (But ductless heat pumps sure could change it up!)

Answered by Dana Dorsett
Posted Wed, 01/16/2013 - 17:29

34.
Helpful? 0

I could add to the canadian study and confirm in our second fully heated winter, that floor radiant heating does not mean lower thermostat settings at all.

I read about it, and anticipated that we d be comfortable with lower temp,
But we usually keep it at around 22c depending on the rooms ( light switch height thermostats on walls)

Though settings could be somewhat lower for other folks as we like to wear not much more than light clothes and everybody is bare feet.

So lets assume that without current light drafts in the house due to a few current problems
( still feels 10 times less air movement that in our prior central heated house )
21c will probably be the ideal setting here.

This said, our house has approx 5k sq ft of electrical in slab floor heating
Every room has its own thermostat and dedicated circuits
Heating will be expensive but comfort is not comparable to anything we ve experienced in the past

I find my house has way too many drafts rigt now, and i still get same comment about comfort from every visitors ( hosted 5 partys during holidays!!! )

I ve personally visited a housenwith ceiling radiant panels, andi didnt like it
Felt like i was starting a cold with a slight hot head
From above heating feels very,good on a cold terrace though

The floor keeps in between 21c and 27c
And it is just perfect here
Very stable with 5" concrete on steel deck slabs
( electrical,wire is buried at the bottom, would preferred a mid slab but it was to complex to install that way)

But at the end, i will still install heatpump mini splits to cool, so with the effeciency difference, they will see alot of use in the off winter months heating period.

Is it smart to still consider anything other than heat pump system ??
I dont think so anymore unless someone can come up with something with similar COP and simpler installation.
Distribution is only a matter of planning.

Btw Martin, fuels costs are way to high here to consider anything else than fire or electricity,
Hell nothing else than electricity is even available here and i am less than 1 hour from montreal.
We pay 0.075$ kw/h. ( just received my bill ;)
But if id have access to natural gaz at a better than electricity, i d still consider it.
( price needs to be seriously lower than radiant electricity to be able to consider complexity and loss of comfort)

My 2 kw/h

Answered by Jin Kazama
Posted Wed, 01/16/2013 - 20:48

35.
Helpful? 0

It is clearly a waste of time to have a difference of opinion in this forum.

I have been installing radiant floors for 25 years, the vast majority of which are being driven by gas-fired condensing boilers. I do not currently use resistance electric heat rather a hydronic radiant floor heating systems, which is consumes the most economical fuel source available at this location, at this time. It is a unique feature of hydronic heating that one can change his mind. With wood, coal, propane, solar thermal, oil, ground source. air to air heat pumps and waste oil systems in all of N.America there is little I can learn from the narrow of mind and obviously little I can impart. So I depart and leave you to your bliss.

Answered by Morgan Audetat
Posted Thu, 01/17/2013 - 21:36

36.
Helpful? 0

Morgan :
1- i agree that hydronic is the best of both world, except in its isntallation complexity and potential problems/maintenance ... that is why i personally chosed electrical, but again
my location makes a difference, because 1 electricity is ok priced here and 2, i do not have access to any other fuel sources :(
But had i know better, i'd still would've consider heat pumps as main heat source because of the cost difference vs resistance.

Here in Quebec, alot of folks have access to free wood (only need to chop it down and store it )
and we see alot of infloor water heating systems with both electrical and wood stove heat sources.
( but i don't like spiders and dirt in the house :p )

2- what are you talking about there ?? waste of time ??
you seem like an experienced person judging from internet info :
http://www.badgerboilerservice.com/ etc ..
why the hurry to leave ?

Answered by Jin Kazama
Posted Thu, 01/17/2013 - 23:47

37.
Helpful? 0

The best way for one to reduce their energy consumption is to use electric radiant ceiling heat. The most practical thing for homeowner is to use radiant heaters to heat the ceiling mounts. The hardware of this device is mounted over the head making it very practical for homeowner living in small houses. This is a good alternative to houses with central heating system.

Answered by Greg Pittman
Posted Fri, 01/18/2013 - 07:03

38.
Helpful? 0

Greg Pittman: might i use the ?????

personally, i liked better multiple baseboard heaters than overhead ceiling, unless with a pretty high ceiling ( 11ft + ) .that might change things .

But how does it affect energy consumption ??
resistance heating is resistance heating ..the difference in heat distribution might affect how people setup thermostat and the total energy use ..but unltimately not by much.
( i don't see how it would change anythign beyond +-5% )

Now hydronic radiant is something else .. as you choose energy source.

Answered by Jin Kazama
Posted Fri, 01/18/2013 - 11:02

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