How \"Green\" is Radiant Heat?

Tim Fausch

I'm working on on brief editorial for the upcoming 2004 Radiant Flooring Guide that BNP is producing on behalf of RPA. I'd love some feedback from those of you who know the subject best. Some recipients of the 2004 Guide will include subscribers of Environmental Design + Construction magazine who are extremely focused on the environmental viability of the products they specify and install.

My question is, "How environmentally sound is radiant heating compared with other forms of heating - is it truly more energy efficient and does it provide a more healthy environment?

I'd like to include some pro and con arguments in the editorial. I appreciate whatever ideas you can contribute. Thanks!

Jerry Boulanger_2

Radiant floor heating can

be very helpful to 'green' designs because it will allow for high temperature drops in primary loops, which means smaller pipes, pumps, valves, etc. It will also allow the use of condensing boilers and make sure that they actually condense.

GMcD

Radiant systems

The "greenness" of radiant systems, both radiant heating and radiant cooling, are well documented in Europe where these systems have been used for a number of decades. There are substantial energy savings due to the use of thermal mass conditioning systems - ambient air temperatures can float to higher and lower limits since much of the temperature control is done by infrared radiation, saving air heating and cooling energy, and with the space "resultant temperature", human comfort is superior in a combined radiant temperature controlled space. As pointed out in the other post, the mechanical plant can take advantage of high efficiency equipment to generate the relatively low heating water temperatures for heating, and relatively high cooling water temperatures for radiant cooling.

I have a ton more info in my personal library as well as cost and operational data from functioning radiant slab cooling and heating buildings in my area. In Europe where radiant cooling and heating systems are much more common, the typical energy performance is usually 60-70% BELOW ASHRAE 90.1 levels. While some may argue that the costs of European buildings are much higher, and they tend to use higher quality materials and methods, the fact is that there are documented, constructed, operating radiant cooling/heating slab systems being used NOW in North America that do NOT cost any more than a conventional building. My background is mainly large commercial systems in terms of operational and capital cost data.

Other points: the PEX piping is somewhat recyclable, the radiant slab systems have a very low life cycle cost- little to no maintenance required, and they last the lifetime of the building, the concrete mix can make use of high fly-ash and other "sustainable concrete" mixes.

In terms of LEED points, radiant slab heating and cooling systems can contribute points to the Indoor Environment Quality section, the Energy and Atmosphere section, and Materials and Resources section of the LEED ratings.

alchemyinc

How Green Is Radiant Heat?

tie radiant into solar collectors and the low input temperatures needed to heat radiant floors becomes even "greener" the only drawback we find is customers run their heating systems more because of the "love facotr" of this incredible heat source. Not to mention Thermal envelopes contribute a great deal to heating costs...The house is a system and should be treated as such.

heatboy

Trick question, Tim

Radiant can, and should be, the ultimate "green" heating system. Unfortunately, that is seldom the case. I do service on radiant systems that have issues and have seen radiant installs that are less comfortable and use more fuel than a basic baseboard and, dare I say it, forced air.

This is my biggest concern with the radiant industry. Uninformed and uncaring contractors could really damage radiant's reputation. I'll bet every guy here could recount a story of a radiant system that was purchased by the owner because it was efficient, comfortable or "green" and has turned into a horror story.

I certainly hope I don't sound like Chicken Little. However, the world of radiant is currently built like a house of cards. Hopefully, we can still get a good foundation under it before .................

hb

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Dale

Data

You may want to consult the Canadian studies comparing different systems, they find that in comparable insulated houses there is no fuel savings with radiant compared to modern warm air, this weeks HVAC news freatured a story about the Ottawa house and said that the real MEASURED savings was the DC blowers. PE pipe is made from a feedstock from oil and that processing to produce the resins releases VOC's. Dan speaks of going to Europe and seeing normal housing using panel rads instead of infloor radiant, are you going to call panel rads radiant heat? I guess you could. Therms of gas per sq ft of house has been dropping for a long time, the problem now as far as greenness is the average sq' of new homes and the multiple bathes that have the hot water waiting to go to the 2 people who live there at night.

Uni R

How Green Is Radiant Heat?

Do you want to balance your article off with a really green perspective?


You may want to point out that many of the houses that radiant goes into are never what could be considered green. With some radiant installs you have a pair of human beings living in over 5,000 SqFt of perfectly heated living space when most of the world's population don't have adequate shelter. This tints the "green" aspect significantly. If everyone was to consume the amount of resources to create and maintain this style of housing, how long would the world last?


Wool sweaters are green. Better-designed homes, allowing more utility in smaller spaces, thereby requiring fewer natural resources to build and operate, would be green.


Snow melt systems, houses with 10s of corners, radiant decks around outdoor hot tubs, and keeping 7 electric zone circulators running 24 hours a day most months of the year should never be thought of as green. Do we ever look at the full electrical costs for operating complex heating systems? That would be interesting actually. Could you draw that part out? The Europeans factor it in to their rating while we North Americans would say that adding a circulator for another zone will allow savings by running that zone at a lower temp, but at the end of the day are the additional KwHrs covered even if this actually happens?


Distributing heat through water, is more efficient than distributing heat using air. Saving energy makes you greener, but a 100% efficiency heating system is only 100% efficient at burning valuable resources to replace lost heat. Houses will always leak energy, and having an efficient heat replacement tool on a really large leaking home may sound green, and one could talk about cutting heating bills in half and all but it is still wasteful which is not green. The Wall is very good at reminding everyone about the envelope all the time (insulate before upgrading etc.) and this is where the green enters the picture. The heating system is there to make up for the deficiencies of the envelope. It's like having brakes on a car. The brakes aren't really there to stop the car. The true benefit with brakes is that they allow us to drive faster safely!


Radiant has two definite green advantages over air. It can incorporate solar more easily (and solar really should be part of systems that are anywhere well south of the 60th) and it works better with condensing technology due to more efficient delivery mode.


This should be a very interesting article... heck it could be multiple chapters if you wanted it to be. The best of luck with writing it Tim.

Ted_5

If you use the right boiler

look at www.viessmann-us.com and look at thier environmental statement. 90% of their boilers meet or exceed max. Co. and Nox. emmisions anywhere in the world!
The Vitodens is less then 10ppm on both Co. and Nox. and at the same time it is 94.2% AFUE. That is as green as it gets in boilers or anyother gas burning appliance!!

Ted

Uni R

This article is right on the target...

http://www.energy.state.or.us/res/tax/Radiant.htm

Mark Eatherton1

Well written article...

however, he, like many other people including radiant floor heating contractors, are fixated on the floor. Look up, look sideways. Radiant walls and ceilings hold a greater potential for inexpensive radiant comfort in a super efficient home. Couple that with an active solar interface, ground source heat pump, super efficient condensing technology or even a hydrogen fuel cell generator and you have the utmost in environmentally friendly systems. It overcomes the problems associated with thermally over loading slabs, provides almost immediate reaction to heat flux demands, and provides an alternative for radiant cooling, which has the outward appearance of being technically viable in the immediate future.

Sometimes we get so focused on warm floors that we forget the alternative surfaces.

I visited the folks at the Habitat For Humanity home that we did the radiant walls in, and they said their home was the most comfortable they had ever lived in, and trust me, they've lived in a lot of homes.

Soon, the NREL folks will be able to spit out some useful data about the energy consumption between this home and two other comparable home in the immediate vacinity.

Radiant floors are not the only way to satisfy human comfort needs. Most people that I've met that have radiant ceilings think they have radiant floors to because the floor is comfortable, which comes from the normal energy flow scenario. Heat flows from hot to cold in an effort to balance itself out. If the ceiling is 100 degress F and the floor is 70, the flow is from the ceiling to the floor and the floor temp will rise to a comfortable condition.

Thinking outside the box...

ME

Radiant Wizard

\"Radiant Heat\"

Radiant Wizard

\"Radiant Heat\"

Is the most efficient way to heat a space hands down. I don't care what this study says or that study says. How about what a heatloss says. Without a doubt a space that is heated with radiant has approximately a 35 percent less heat loss than any other form of heat. Everyone here seems to not be able to get that through their head. It's a fact. You cannot change it. Get over it. You need less energy (btu's) to heat the same identical space, period. The question in this thread should be. Which "COMPLETE" heating system is the most efficent? Now you can argue, applications, boilers and control strategies.

So, as far as I'm concerned you can take studies and do the same thing with them as AFUE ratings. Use them as toilet paper because they don't mean anything. They are just another way to confuse the public, which by the way, are the consumers of the products and systems we sell.

So, why don't those of you whom cannot get this simple anwser to a question that you think needs a grant and a room of professors and interns to figure out, go back to the basics. It all starts with a heat loss.

heatboy

There is little doubt........

that the Vitodens sets new standards for every measurable standard, Ted. I feel confident enough to say that my projects are as "green" as they come (for the budget presented). For the most part though, the, and I use this word loosely, systems I see installed, are no more fuel efficient and a few are actually worse, than any other standard stuff. Just saying that radiant is the greenest, most efficient and comfortable heating with this broad brush being used here is silly. Ideally, there is nothing better.

hb

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GMcD

Radiant surfaces

Absolutely right. There are actual functioning examples of this approach in the Pacific NW and in the harsh climate of Calgary, Alberta. Gleneagles Community Centre in West Vancouver has tilt-up concrete walls as well as cast-in-place concrete floors which are radiant slab cooling and heating. The mechanical plant is a geothermal heat pump set and the ventilation is a 100% outdoor air displacement ventilation system served by heat recovery units. It's been operating for a year now, and is "the most comfortable building" the staff has worked in. And, it was not built at a "premium cost", and the energy use is half of what a comparable "conventional" system building would use. Granted we have a mild climate here in the Pacific NW, but the ICT Building at the University of Calgary has all of the building spaces climate controlled by overhead radiant cooling slabs (8 storeys, 150,000 SF) with an air system delivering basic treated outdoor air for ventilation purposes only. The perimeter offices are equipped with supplemental heating/cooling augmentation from the air system, mainly because the designers did not push as strongly as they could have for higher performance glazing. The higher cost glazing would have been easily offset by the savings in mechanical and electrical systems costs. Another example in the NE area is Enermodal Engineering's Earth Rangers Conservation Centre which is complete and operating by now- a large radiant cooling/heating slab system with displacement ventilation in Ontario, Canada. So these systems are not constrained by severe climates. Even humid climate applications of radiant cooling can be achieved, with proper design and a building physics engineering approach.

The North American obsession with "air temperature control" flies in the face of the rest of the world where the "resultant temperature" and decoupling the ventilation system from the temperature control system is what the answer is for low energy, superior indoor comfort conditions.

Lloyd Nichols

An example of the difference

is the calculated heat needed for a new 7 bay, 8,500 GSF town highway garage here in central NH. The consulting engineers estimate for unit heaters is 59% more than for radiant floor heat. Apparently, the difference really shows when a high volume structure of this type is involved. To make this building even greener, serious consideration is being given to the use of very high efficiency wood pellet boilers. These boilers have very low emissions and run in the 88 to 90 percent efficiency range. Not a residential heating example but, significant I think.

Lloyd

Uni R

An example of the difference

That's a great example of the difference but it is also a perfect example of a difficult to heat structure (which would not make for a "green" home. The major point in the article was that if the structure holds heat well enough, the perfect heating system becomes less and less of a factor and it becomes very much harder to recoup the additional savings in energy from the increased investment in mechanical systems.


Wizard,
There is nobody here who doesn't think that radiant is the most efficient was to deliver heat. What the original poster requested was some pros and cons.

Phil_8

Green Radiant Heat

Tim,

Several years ago (perhaps 4 yrs.) P&M magazine dedicated one monthly issue to radiant. In that issue was an example of radiant heat solution somewhere in the Rocky Mountains that was off the power grid. The complete control system (including circulators) was designed to draw minimum electrical current provided by deep cycle batteries and that were charged via solar panels. Great article. The boiler was actually placed in a small structure outside the house that looked just like an out-house. In fact, I think the picture of that "outhouse" was on the cover of the magazine. Wish I had kept that that article.

Also look up Siggy's article a few years ago in P&M on external supplemental wood boilers. He discusses how wood has to burn hard and fast to get the maximum BTUs from each cord and how to size a "heat storage tank".

Mark Eatherton1

Mike Tierney...

of Aspen Solar fame did the deed. He can be reached at www.Aspensolar.com

ME

Phil_8

Tierny & Seigenthaler

Mike Tierny and John Seigenthaler should collaborate on a book "Green Radiant". With power outages becoming more frequent and longer lasting, such a book showing the design details/options of a low current draw, solar powered control system with wood fueled backup and heat storage tanks would be awsome.

Unknown

What is green

If you really want green you need to stop using fossil fuels. Nuclear energy on the surface appears to be green until you have to dipose of the spent fuel rods so that eliminates elctric heating where electricty is the fuel used to heat a building.

Here is a real green job.

Solar panels and heated water storage tanks to provide the nergy needed for any water system.

The problem there in lies with the amount of solar radiation availible for the location that a building is in there fore a boiler or another source of energy is needed to heat the stored water.

How cost efetive is an installation of this type?

I read an article about ten years ago where an engineer built a house in Minnesota where his annual fuel consumption was about $200.00 per year.

The system he installed at that time comprised of radiant wall panels, a heat sink under the house that was built of concrete and epoxy lined. The heat sink held 10,000 gallons of water and was filled with ignious rock. The sloar collectors heated water to about 130 degrees F and was circulated through the tank that held the igneous rock.

Water was drawn from the tank and circulated to the radiant wall panels and a heat exchanger to make domestic hot water.

There was enough energy stored in the tank to heat the building for about two weeks if the weather did not permit the solar collectors from reheating the water in the tank.

The only way you can call a building green is not to use the fuels we use today for our comfort.

A greener building is a building that is well insulated, and built to absorb energy from the sun but that causes another problem. If you absorb energy from the sun you may have cool the building thereby using electricty.

Until the United States of America begins to use efficient fuel cells to produce electricty to heat and cool buildings we will not have green buildings.

Think about this one.

Two people build a house. The house is 4,000 sq.ft. They need to heat and cool the house a very efficient heating and cooling plant is installed in the building and the heated temperatires are at 70 degrees and cooling temperatures are at 75 degrees. Assume the energy bill for this high efficiency building runs about $1700.00 a year.


I owned an old house that was 1750 sq. ft. Five people lived in it my energy bill was $2100.00 per year.

Here is the green answer.

2 people consumed $850.00 per year each in energy for comfort.

5 people consumed $425.00 per year each in energy for comfort.

Which house do you think is greener.

And here is the age old question. What came first the chicken or the egg?


Jake

Uni R

The Egg

Jake,

The first of those two that would have had the DNA of a chicken would have been the egg. It's parents were close but would not have had the DNA of a chicken. We can't cure the common cold yet but we can resolve that question.

One other thing to think about is how much energy and resources it takes to create the house and then ammortize that with the annual impact.

frank s

I agree..the egg

If you look at Darwins theory of evolution, the answer is simple, which is what we should All do with radiant .....keep it simple

Tim Gardner

The article about the $200 per year house in Minnesota sounds interesting. Do you recall the name and/or source of the article?

Thanks,
Tim

Uni R

For the concept you may want to read this...

www.sb.luth.se/~bon/bon/IEA/eia.pdf