Using far infrared heating for in-floor heating of a house
jonscholl
| Posted in Mechanicals on
I came across a product….Geo Dream carbon film …..at the GreenBuild 2015 Conference in Washington DC and I am interested in anyone’s comments about its use and performance. I have spoken with the North American supplier ….located in Vancouver BC… and some of their installers and everyone speaks very highly of the product and the fact that it can be used as the sole source of heating for the home. We are building an ICF home in Climate Zone 5 and are quite interested in using the product.
Comments welcome! Thanks.
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Replies
Jonathan,
This appears to be an in-floor heating system using electric-resistance cables instead of hydronic tubing.
I'm sure it works. As you probably know, electric-resistance heating is usually expensive to operate. But if you live somewhere with very low electricity rates, and you are building a house with very high levels of insulation, it might make sense.
A ductless minisplit will heat your house for about half or one-third as much electricity as these electric-resistance heaters.
Lots of dubious sounding claims. Suggests also installing minisplit if you want A/C, but then why use the film? They don't explain why it is any cheaper to operate than any other electric resistance heat. I'd want to ask someone who lives with this system to provide operating cost data.
If you are going to use electric resistance heat, and don't mind the cost, electric radiant floors are an OK thing to do, but they are more expensive than other kinds of electric resistance heat, and they share the efficiency disadvantages of other electric heat.
The main problem I see is that their website implies that this is something special and magical, when it's really quite ordinary. A concrete example of the degree to which their pitch is based on BS is that they like to emphasize that it's FAR infrared, but they also emphasize the similarity to the sun, which is near IR.
My understanding is that this is not a resistance heating product...it is indeed a FAR infrared product which was developed in Germany over 60 years ago and is widely used in Europe and Korean...among other places. My experience is that we in the USA are often quite slow to embrace other technologies that have been in service elsewhere in the world...because they are not "our norm". I don't use any "new" products without trying to do the proper research...which is why I am posting the question here at GBA. As such, I am looking for comments from people who have actually worked with the product or know about the technology. Thanks.
Jonathan,
Unless anyone can propose a different mechanism for the production of heat from electricity, I'm calling this electric resistance heat. Clearly, this system doesn't use a heat pump. It's not magic. These are warm electric wires, like the wires in your toaster.
Interesting points Dana regarding thermal mass. I appreciate that insight. What about using ICF's because it is a much stronger wall, it is a much tighter wall, it is a much quieter wall and once it is poured, it is already insulated to a R21. Plus it doesn't have all the problems associated with possible rot and mold that wood walls do. Those are the reasons we selected ICF's. Have I made a poor choice?
ALL radiant floor heating is in the far infrared- the notion that this product is somehow special in that regard is just silly. Even old-fashioned cast iron steam radiators operate in the far infrared. Korean ondol heating under floors is achieved by burning wood (or sometimes coal), not electric mats.
Electricity in Japan & Korea is expensive enough that in new construction heating with air source heat pumps or electric /gas/ kerosene space heaters is far more prevalent than under floor heating. (Under floor heating in luxury housing with gas-fired boilers happens in those countries, but rarely is it with electric mats.) Europeans tend to use either gas fired boilers or hydronic heat pumps for their low-temp radiator & radiant floor heating.
There is an argument that radiant heating buys more comfort at any given room temperature than air-delivered heat (true). Comfort is more about mean radiant temperature (MRT) than air temperature. But raising the room temperature several degrees using air-source heat pumps to achieve the same MRT as with a radiant floor/ceiling uses less than half the amount electricity than electric-resistance radiant, less than a third in Vancouver's temperate climate, as Martin correctly notes.
Using windows with a lower U-factor and higher R walls also improves the MRT in a room.
If the choice to use ICF is about lowering energy use due to the thermal mass, don't. There are very few zone 5 locations that will see even a 5% reduction in energy use. See the map in Figure 4 in this document:
https://cshub.mit.edu/sites/default/files/documents/ThermalMassBenefit_v10_13_0920.pdf
A minimalist 2.5" + 2.5" ICF is about 24% higher than code-min for mass walls in zone 5, and there are usually much cheaper ways to buy that much performance. There are many good reasons to build with concrete, but in a zone 5 location energy performance isn't one of those reasons.
Looking at Figure 4, note that the temperate marine zone 3C of California sees the highest annual energy use benefits of building with high thermal mass, an artifact of the number of days per year when the outdoor temperature swings both above and below the desired indoor temperature. It even trumps the high diurnal temperature swings in the desert SW.
I have the same heating elements, but sold by a different vendor (Warmup), in my 550 sq ft studio in CZ6. It works well but as stated in the previous posts, it is simply resistant heating. No more no less. Operating costs are the same as any other variety of resistant heat, provided that you have adequate insulation under the floor. I've used the system through 3 to 4 winters. I chose the system because of the low install cost and because I didn't think that my intermittent use of the studio would justify the considerably higher initial expense of a minisplit. Furthermore, my off-use setpoint is about 52F and I felt that the minisplit wouldn't be as effective or efficient with the intermittent demand and the need for fluctuating temps. I'm pleased with the product for my current use. The system is able to step up the temp from 52F to 68F in about 45 minutes in most conditions. It has cost me a maximum of $100/month but, again, that's for sporadic use. If the space were kept at 70F 24-7 the minisplit would have been the better choice. The difference between this system and cable type infloor is that it can be installed simply under laminate flooring. The heating elements come in rolls and are thinner than a credit card. There aren't any cables in the mats. Copper tape spans each edge and delivers current to the carbon film is the heating element. Installation was straight forward and simple. The heating mats were developed and are manufactured by a company in S. Korea and rebranded by retailers in various countries. Note that in my experience the retailers have room to negotiate price.
Ed
Jonathan: Given that the industry is rife with exaggerated claims for the thermal benefits of ICF, I wanted to make it clear that the energy use benefit of the thermal mass is almost vanishingly small in most zone 5 locations. Whether the other benefits are going to be worth the up-charge for building with ICF is YOUR call- I have no basis for assessing whether it's a poor choice for you or not. ( If I lived in tornado alley or a hurricane zone the benefits might be commensurate with cost for me, but YMMV.) Just know going in that it's not dramatically better than code minimum from a thermal performance perspective.
If the cushy comfort of radiant floors are on the "must have" list there are ways to do that leveraged with hydronic heat pumps rather than resistance heating mats. In most locations the higher up charge for the heat pump systems will "pay off" in reduced operating costs within the lifecycle of the equipment, but there are some (rare) markets electricity is sufficiently dirt-cheap during off-peak hours that the financial math works in favor of a lower upfront cost resistance heating. The history of resistance radiant heating isn't a particularly great one from a longevity perspective. An electric boiler with hydronic radiation (including in-floor radiation) may make more lifecycle sense even in those situations where electricity is dirt cheap.
In a zone 5A location the latent & sensible air conditioning loads can add up to something as high or higher than the space heating load. The heating/cooling balance point in a minimal ICF can be in the 55-60F region, and the up-charge for a heat pump vs. a cooling-only solution isn't usually very much, and would give you the option of higher heating efficiency vs. higher floor temperatures.
In general, the crummier the house, the bigger the comfort upgrade of going with radiant floors. At low heating loads the temperature difference between the floor and the walls & ceilings isn't all that great, so if you have a low-load house most of the time the effect is pretty subtle. If it's worth paying extra for the barefoot comfort that's most noticeable at 5AM on the coldest day of the year that too is going to be up to you. In very high R houses it's sometimes "worth it" to have a radiant floor in the bathroom, but otherwise not so much. The wall temperatures on the interior side of an ICF are pretty uniform and not very cold even at design temp, but the window surfaces will be quite a bit colder. Sometimes there is more comfort value in bumping up window performance than warming up the floors. In most zone 5 ICF houses (or even code-min stick-built) the combined heat losses of code min windows are higher than the combined wall losses. Raising the temp of the window surface with U0.18-U0.20 decent but not super-performance triple-pane also improves MRT. And unlike radiant floors, using better windows lowers the loads.
BTW: If this house is in the US, you may be interested in estimating the relative carbon footprints of a resistance heating solution like radiant floor films & electric boilers vs. fossil-fired hydronic vs. ductless heat pump solutions:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/carbon-footprint-minisplits
A few interesting things I saw in the MIT study that Dana posted:
1) no matter where you live in the US, once heating loads are addressed, the next two biggest loads are Plug and DHW. I thought cooling would have been second in the South.
2) Increasing the glazing from 5% to 15% and then 25% results in decreased energy consumption in cold climates. Without proper shading, the energy savings may come at a cost of overheating a few times during the shoulder seasons, but personally, I would rather have bigger windows and open the windows during the overheating days.
3) Regardless of diffusivity, the energy savings from building to PH standards over 2012 IEC in San Francisco (marine climate) is not very large. The energy savings are much greater in cold, hot/humid and even hot/dry. This makes me think it is somewhat ironic that PH has been so popular in the marine NW where I would assume the savings would be small like San Fran and the carbon savings even smaller considering how clean their energy supply is.
4) Keeping the footprint constant, annual energy consumption declines in all zones when increasing the height from 4 meters to 6 meters to 8 meters.
Jonathan: Those ARE the right take aways.
1: Air conditioning is seasonal, hot water heating is year-round, and higher in the winter than in the summer. Air conditioning is always leveraged with heat pump technology, but there is still a lot of resistance electric and fossil-burner heating, so even in cooling dominated climates the space heating energy use often exceeds the cooling energy use. The cost of the heating energy with fossil fuels in those climates is often much lower than the air conditioning costs, even when the total energy use for heating is higher.
2: Overglazing does lead to overheating, but it also increases the peak heating load even though it reduces energy use by the solar gains. There are comfort issues related to both the higher peak load and the overheating.
3: The PH standard isn't fully financially or carbon-footprint rational, but it's a standard. The carbon accounting methods used need serious (and far more frequent) updating to become relevant. California's Zero Net Energy requirement for residential buildings starting in 2020 will probably do far more for the world by 2022 than the cumulative impact of all PH houses in the world built by that date. PH houses in the temperate Pacific Northwest have almost no net impact on carbon emissions relative to 2012 code-min houses heated with heat pumps.
4: Multi-story buildings are more energy efficient than single story buildings for a variety of reasons, but living in a 5 story tower isn't exactly practical. :-)
Simplifying the model to a cube makes the analysis a lot easier for teasing this stuff out, but a real house is not a cube. But in general, the simpler the shape, the more energy efficient the house will be. Junior architect fascination with bump-outs and dormers is a bit misguided.
Jonathan, if the rep you met tried to convince you that the far infrared aspect makes this different from any other floor heat, the rep was either confused or lying. These certainly do produce far IR, but that is nothing special or notable. If you heat an object up a little warmer than room temperature, it emits far infrared thermal radiation. That happens regardless of what mechanism you use to heat the object. That's a possible way to heat a house, but if the heat is produced by electricity in a resistor, as is done in this product, it is ~3X less efficient than a heat pump. If efficiency is what you are after, mini-splits are a much better option. If you want heated floors, and efficiency, you can use hydronic floor heat with an air to water heat pump.
In case it is not clear, the 'far' in 'far infrared' is just the word far, not an acronym. Near IR is just a bit longer wavelength than red light; far IR has much longer wavelengths than red light. The difference is important for understanding some types of high performance windows, but it isn't very important for understanding heaters. As Dana notes, many types of heaters produce far IR. Very few produce near IR (heat lamps, quartz tube heaters and open fires). But human skin and clothing absorbs either one just fine.
Dana,
That is the best I have ever done interpreting anything produced by MIT!
Yes the seasonal factor of AC is what I forgot to factor in. I wonder if it still holds true for the deep south. I remember living in FL one year and we kept running the AC until Christmas.
I agree that PH is a standard and not the ultimate solution. PH is interesting for me because I think it is helping to move the ball in the right direction. PH adds a layer of professionalism and quality control to the equation. It also provides and avenue for quality builders to improve their skill set through the certification programs. That is good for everyone, whether they build PH or just PH lite. Even if certification or hitting the benchmarks are not the goal, but just incorporating the PH philosophy and techniques to get maybe 70% of the way there (which many will concede is probably close to the comfort and financial optimum level), we will improve our housing stock over and above current code and reduce our carbon footprint.
I have not drunk the entire glass of Kool-Aid, maybe half the glass, but I still plan on getting my next house certified, as well as completing my PH certifications for Builder, Consultant and Tradesperson. It probably is over-kill, but if I decide to do this again for someone else, I would rather start from a position of having reached the PH standard and then be able to see where it makes sense to dial it back to achieve an optimum trade-off between cost/comfort/carbon.
I agree that simplifying the design goes a long way towards efficiency and it actually saves money. We don't all have to live in a four-square cube, but if only you could see all the roof-lines and bump-outs of the homes in my area. All I see are thermal bridges and air leakage and frankly most of these designs look ugly to me. I am starting to think architects get paid by the number of planes their designs have.
Very late to the game here - Everyone has supplied detail in abundance, so I can only offer an overview of why I elected not use in floor radiant and how it has been to live with my choice of wall mounted radiant cove heaters. Simplest version - installed cost, flexibility of control, freedom of flooring choices, no need for air conditioning, dead silent operating sound and a highly divided floor plan that didn't play well with mini-splits.
Results have been a very evenly heated house in a high altitude cz6. Everyone gets their own thermostat to control and while the electric usage is relatively horrendous, the translation into BTUs used has been very close to design parameters. I don't anticipate any maintenance on the heating system and should anything fail, it is on the wall not under the floor. A window average of .21U, R40 walls and R50+ roof kept heat loss loads in the 6.5 BTUs per sf at a design point well below zero. These have proven critical to the success of making the house comfortable to be in.
In looking at different forms of in-floor radiant heat, calculations showed that none of the embedded wire or film types needed to cover more than a fraction of any room to provide design max BTU load (plus a margin). Distributing strips of heat in the room was a possible approach, but I was concerned about the flooring undergoing differential expansion or feeling very spotty under tile. The films admittedly claim a max of 84 degrees but I never purchased any samples to test. Most relevant are the 40-50BTUs (12-15W) per sf ratings shown for most systems For my design, the max load in the "worst" room was the kitchen with almost 25% glass relative to floor area, requiring approx 11 BTU sf at lowest temp design point.
Obviously the heat source would cycle in need set by thermostats but a 200sf room completely set with film or wire could need 3000 watts available. With multiple rooms the electrical panel can get pretty full fast. Cost was the final straw given that wire systems typically need to be embedded in thinset under tile (Under subfloor types exist) and some film types require an oversheet between it and floating floors, no option for nailed strip flooring. Placed cost of materials alone ranged from 3.60 to 10 dollars a square foot translating into potentially many thousands of infloor heat dollars. The cove heaters range from just under to not far over 100 dollars a unit. Electrical costs per locality. For us the propane option was not a good choice.
I have gone on too long at this point, but I will say that well insulated walls and windows have worked well with the cove heaters at keeping all surfaces and floors at desired room temperatures. Any money spent on walls and windows would be money well spent. Low losses will help to make all surfaces inside comfortable since they all equalize close to the desired temp you set. Our previous home (with forced air heat and ordinary batt insulation) suffered from very cool exterior walls most of the heating year. The discomfort of sitting near an exterior wall made pushing up the thermostat a spousal flash point, but over heating the air was the only way to stop feeling the chill. There is no cozy "warm feet" anywhere in the new house which was expected per comments made in earlier postings. However, I can sit near walls and windows with the thermostat 4-5 degrees lower than I use to and no more fights over the thermostat. As others noted, a floor that feels warm to your feet can only be useful in a poorly insulated house.
More observations on request now that we have been in it through the winter.
This product doesn't seem to be exactly what it is promising. It also consumes alot of energy. Might I suggest a product I recently just used for my basement called the truheat system. It is a low voltage system which heats an aluminum strip. Installation was a breeze and the energy consumption isn't that high at all!
Even more marketing fluff. This is just another infloor electric radiant heating system. High voltage or low voltage, it doesn't matter. The kilowatt-hours of electricity put in are directly proportional to the Btu's put out. No more, no less. Whether or not their system is cheaper and/or easier to install can be debated. But their claim to use less energy to produce the same amount of heat is absolute bunk.
I would consider the "Floor_it_right" reply to a 4 year old post more spam than "marketing fluff".