Clearing the air on radiant - (see our comprehensive list of research citations on radiant cooling and heating.)

On the Internet...

Facts

eHow

ok...there were so many unbelievable statements at this eHow article it's easier for us to advise readers to avoid any article that mentions 'polyurethane' pipes and 'floor furnaces' in the same breath. Pipes aren't made of polyurethane nor are floor furnaces even close to underfloor radiant systems. This is just bad information all around. Keep reading below for other amusing statements and claims..

On the Internet...

Facts

"On average, radiant floor heating systems deliver only about a maximum of 60% of their heat by radiation; the rest is mostly by convection."

If 60% is the majority - it is the "mostly" i.e. the heat transfer is mostly by radiation. We find the syntax in the internet statement interesting...see this link for heat transfer coefficients (HTC)...this difference between HTC values is based on the differences in convection and the amount of convection is a function of the enclosure performance, room geometry and surface temperatures and orientation of the panel (wall, floor, or ceiling). In high performance building there is less convection and more radiation which is why surface emissivity's can play a more important role when buildings don't leak. By definition, if the radiant component is 50% or more it is called a radiant system. In the absence of forced drafts (i.e., in space fans), radiant heating ceiling systems and radiant cooling floor systems are virtually free of any convective transfer due to reduced influence on air density, ergo they transfer almost all of their heat by radiation. Radiant floor heating and radiant ceiling cooling exchange between 50% and 60% of the energy via radiation.

On the Internet...

Facts

"The floor material then radiates off the heat into the cooler surrounding air" or "The air is warmed because of the radiating heat" or "Radiant heat is effective because it heats the air rather than blowing warm air throughout your home." or "heated wires in the floor that warm the air in the room above." or "With a radiant floor heating system, heat is even and warms the part of the room most used by people." or "it heats a room from the bottom up". or "It is efficient because it does not feature a fan blowing heat around the room; it heats from the bottom up, which warms the feet and body first." or "The real advantage of in-floor heating is it radiates heat back to your body." or "The air around you will be slightly cooler, but your own body will absorb the warmth generated through the heating system in the floor." or "they warm up the bottom half of the body making it feeling more comfortable and reducing the feelings of lethargy." 

For all practical discussions outside of academia, the radiant energy exchange within a building does not directly heat the 'air' molecules - it heats the surfaces in the room which in turn are in contact with the air...ergo the air becomes warm only because of the contact with warm surfaces vis-à-vis the conduction and convection process. The aggressiveness of the natural convection (i.e. air flow across a surface) is a function of the building enclosure, radiant panel orientation (wall, ceiling, or floor) and whether it is heated (emittance) or cooled (absorptance). For further discussions on this topic visit our page on heat transfer coefficients.  Furthermore, many people think radiant floor heating heats the body but (sans discussion on conduction heating the feet) this is not exactly the case, radiant heating systems provide comfort by warming the interior surfaces which reduces the temperature difference between your skin and the interior surfaces which in turn reduces the loss of body heat via radiation. You see its not necessarily the radiant heat you are absorbing - its the heat you are not losing which results in perceptions of comfort. Some people compare the warmth from the sun to the warmth of a heated floor but the sun and floor operate a two completely different electromagnetic wave lengths. Both provide thermal comfort but in different ways. Radiant cooling works in the opposite method by encouraging the loss of body heat via radiation...its the loss of heat from your body via radiation which provides the cool sensation. Learn more from our pages on thermal comfort.

On the Internet...

Facts

".hot water is circulated in the pipes and warms up the slab and slowly radiates heat into the space."

First, it isn't hot water -  in fact in a high performance home (< 10 Btu/hr/sf)  with conductive floors (tile, slate, concrete) and tight tube spacing (6" to 8" o.c.), the average water temperature is a nominal 85 deg F or very close to skin temperature and cooler than your core body temperature - tepid to warm - definitely not hot. The cooler the fluid in heating and warmer in cooling the better the plant efficiency through first and second laws of thermodynamics (also see our comments further down on exergy yes    "e-x-e-r-g-y" it is not a spelling mistake.). Second, the speed at which the slab warms up is a function  of the heating load, building mass, tube spacing, back losses to grade and flooring conductivity. With proper passive and active controls there is little significant difference between what one finds in a forced air heated home. Third, radiant energy travels at the speed of light - there is nothing slow about it.

Discussion: when it comes to "slow" to heat up...for some bizarre reason people must image letting their home get down to design conditions say -20 deg F. before turning it on and then see them selves standing there with a time clock to count how many hours it takes to heat the room up to comfort conditions. This is so far from reality it's almost silly. With one run of the mill strategy, as soon as the outdoor temperature drops below some preselected ambient temperature - say 65 deg F - an outdoor reset control wakes up from it's sleep mode and starts to monitor the interior and exterior conditions...if it continues to get cold outside and it shows up inside as drop in temperature - then it starts to manage the system fluid and heater by turning it on and ramping up the fluid temperature. So with a well designed system with proper controls you can maintain comfort all the way from 65 deg F down to -20 deg F without having to "wait" for the system...that is unless of course you enjoy starting your system at -20 deg F.

On the Internet...

Facts

"radiant heating is expensive" or "radiant cost a lot more than other systems" or "the most comfortable system is radiant but it's a lot more money".

Show us a big inefficient home with whacked out geometry in an extreme  climate with wicked temperature swings and a builder who doesn't want to do the system and we'll show you an expensive radiant system. That's it - that's as complicated as the economies get...price is always proportional to system complexity, building performance, climate and builder flexibility and confidence (which comes with skill which comes from practice). Give the experienced designer and skilled contractor a high performance enclosure (deals with the climate) with some normallacy in design (simple geometries) and we'll show you a low cost affordable radiant based HVAC system.

The exception is when over zealous designers use peoples homes as a blank canvas to express their mechanical artistry ... in this case - owners buy a 'one of a kind'  system for the 'one of a kind' price...talk with us at the forum on how to prevent this from happening to you.

Lastly, the term 'expensive' is a relative term - expensive to one is affordable to another. Consider millions of people stand in line at Starbucks day after day to pay $5.00 for a boutique cup of coffee...others spend thousands of dollars each year on their pets...and some spend more on outdoor decks, patio's and furniture than on their own HVAC systems...expensive shmensive...it's all about ones priorities.

Suggested reading: Are you paying too much for downgrades? and Do-it-yourself HVAC.

On the Internet...

Facts

radiant..."is not effective in energy efficient homes with really small heating loads because even a small amount floor heating can cause overheating due to the thermal mass effect."

 

We often see this statement associated with "popular science" experiments involving conventional construction practices rather than on low load energy efficient projects... never the less - using proper controls and systems typical of well designed projects mitigates overheating in all types of buildings in all types of climates.

Discussion: overheating in all buildings occurs with various combinations of enclosure performance, building mass, solar control, control over internal loads and control over the heating systems (and all types not just radiant). Poor control over one or more of these elements can prevent the occupants from shedding their internal body heat at a rate fast enough to feel comfortable.

Your options:  control the building by site orientation and choosing the proper combination and location of windows, insulation and mass; control the solar gain and internal gains; control the heating system or preferably - all of the above. Since the finger is pointed at radiant heating lets discuss the radiant by first talking about controls.

In high performance single zone homes (less than 10 Btu/hr/sf) with proper exterior shading and glazing with less than 20% window to wall ratios, there is little demonstrated benefit for having sophisticated radiant heating controls. A simple non electric thermostatic valve and analogue control on the heater or even a simple pulse width modulated (PWM) thermostats controlling the heat source is a suitable and effective solution.  In conventional housing with multiple zones and dynamic loads it is useful to modulate the temperature of the system fluid with in-space room feedback. Modulating the fluid temperature with what is known as weather compensators or indoor/outdoor controllers or reset controls is a tried and true technology having been in existence for  decades so this is not a "new" solution nor is it "high tech" nor are they "expensive"...put it this way,,,,weather compensators are like the cruise control on your car...they regulate your speed, control your fuel consumption and no proper car would be without one...likewise with radiant systems in some applications. Weekend engineers' who experiment without doing the research or by those who don't want to invest the money in controls and then blame the system for over and under heating tend to be the same folks who spend the rest of their life on the internet telling everyone about how bad radiant is. When you read this stuff on line what you need to read is, "I'm a weekend engineer and didn't do a proper job of researching building science nor paying for proper controls".

Secondly,...if you don't want to mess with solar gains then (wait for it) don't give the solar energy a place to store itself... this is not that complicated...keep the short and long wave energy off and out of the building with external shading and reduced glazing areas (less than 20% window to wall ratio's) with an appropriate solar shading coefficient and use readily available off the shelf low mass flooring.

Conclusion: 100% of all over heating and under heating complaints in homes heated exclusively with furnaces did not have radiant floor heating to blame.

On the Internet...

Facts

"The heated pipes radiate energy into the slab which then heats the air" or" Radiant heat from the Pex hot water tubes in the concrete slab is sent out in a 360 degree pattern." or "This fluid picks up radiant heat coming from the ground."

Embedded or buried pipes or cables use conduction (not radiation) to heat the mass...energy in the form of electromagnetic waves are radiated (emitted) from or absorbed by surfaces. There is no temperature in the electromagnetic waves - only energy. In order for these electromagnetic energy waves to be converted to heat (measured by temperature) they must travel through a transparent space until they hit an opaque surface of a cooler temperature where they are absorbed. The absorption of the energy increase the molecular action in the surface which raises the temperature of the surface and through conduction heats the underlying mass.

On the Internet...

Facts

"to prevent overheating with very small loads, the slab has to be no more than a few degrees above room temperature which means the floor won't be warm to the touch in fact it may feel cool to the feet."

You have to differentiate between comfort and "warm to touch" or "cool to touch"...again decades ago, research discovered that people wearing normal foot wear prefer floor temperatures in and around 75 deg. F. In fact ASHRAE Standard 55 and ISO Standard 7730 both state for comfort, floors should be regulated between 66 deg F for cooling and 84 deg F for heating with 75 deg F being the optimum temperature. For those in bare feet or feet with light socks the limitations of the floor are also a function of the flooring itself. If 74 deg. F is necessary for comfort than this is a good thing. For further details see this link on floor temperatures  and see this discussion on having warm floors in high performance homes.

On the Internet...

Facts

with..."solar gain it may be possible with floor heating to be delivering excess heat causing overheating."

This is a twist on what we have already addressed but lets explore it further.

Have you ever placed an ordinary thermometer in the sunlight inside your home on a summer or winter day? What does it read and what does this tell you?

Here's one example: south facing double pane glazing, February 25th, 2011, Calgary, Ab., Canada - outdoor temperature -8 deg F (-22 deg C), floor temp = 88.5 deg F (31.4 deg C) WITHOUT floor heating.

Sans any discussion on window performances, it should tell you even without radiant floor heating the floors will get warm - so long as the floors see the sunshine they will warm up due primarily to the short wave radiation travelling through the windows. Throw in the long wave energy emitted from interior surfaces warmed by the short wave energy and you have a room heated with radiant energy without having embedded heating pipes.

Discussion: in a properly controlled high performance home under maximum load (no solar gain...middle of the night...wind howling...nasty cold), the floor temperature would be operated at a few degrees above a room temperature of 72 deg F., so lets say the floor is between 74 deg F and 76 deg F and if designed correctly maybe an average 80 deg F. fluid temperature...cooler than core body temperature and cooler than skin temperature but still comfortable ...recall you have your own internal heat source that generates at rest a nominal 360 Btu/hr - so in fact under normal conditions - you need to get rid of heat to stay comfortable...and by the way feet are a great place to shed heat due to the blood flow and conductive transfer with the floor...anyways the million dollar question is,  will you have that ooh ahh sensation of a really warm floor? No but it will be warmer than the floor in the same space heated with a furnace.

Anyways...morning comes along and as soon as the sun hits the 74 deg F to 76 deg F floor, it starts raise the floor temperature - but only those surface areas that "see" (absorb) the shortwave morning sun radiation - as such the room operative temperature of 72 deg F begins to rise as well...so what happens next? Well the thermostats stops the flow of tepid water to the floor and after some period of time the floor surface is at or warmer than the fluid in the floor. Since hot travels to cold or in this case warmth to coolth (yes it's a real word) ...the floor warming system becomes a solar absorber and can cool the floor by sending the solar gain ( a temperature rise in the fluid)  to a colder part of the house...or you could turn the system off completely and let the sun take over the comfort in your space. All you have to do is remember warmth travels to coolth and if the sun makes the floor warmer than the fluid in the pipes...the floor system is not contributing to the overheating.

If you want to shed solar heat gain in winter...open up the windows...it didn't cost you anything to get it in the first place so it won't cost you to lose it...the greenhouse people figured this out centuries ago...if you don't want to manually manage it...reduce your window area, reduce the windows solar heat gain coefficient, use exterior shading and low mass floors...but don't blame the radiant floor ...unless of course you didn't control the incoming solar heat in which case it's still not the fault of the floor.

Conclusion: 100% of all over heating and under heating complaints in homes heated exclusively with furnaces did not have radiant floor heating to blame.

On the Internet...

Facts

"...radiant heating systems transforms cold floors and furniture into heat-omitting objects."

Heat is not "omitted" from warm objects it is "emitted" provided it has some place to be absorbed, reflected or transmitted. There is no radiant transfer between two bodies of the same temperature.

On the Internet...

Facts

"...the heat travels slowly upwards from the floor to the ceiling."

Radiant energy does not 'travel slowly' it travels at the 'speed of light'. The energy is converted to heat when it hits a solid object of a cooler temperature.

On the Internet...

Facts

"The best place for radiant heating is on the floor because heat rises." or "Heat rises so the whole room from floor to ceiling will heat up..." or "In-floor puts the heat where you are and not on the ceiling."

Heat doesn't rise...hot air does...radiant energy travels from hot to cold and in all directions...and heats the entire room not just the first 6 feet...if you don't get this basic principle try standing under a heat lamp...heat rising? No...if heat rose we would have to stand on top of the sun and put heat lamps on the floor...so just exactly where is the top of the sun? Radiant heating can be done from any surface, floor, ceilings and walls.

On the Internet...

Facts

"The best floor covering is tile or concrete because of its heat-conducting qualities. Wood floors or thick carpeting are insulators..."

The effectiveness of a surface as a radiator has nothing to do with its insulative qualities but rather with its emissivity. 99.99% of typical floor coverings have very high emissivity's ergo they all make good radiators. The insulating qualities affect only the fluid temperatures and pipe spacing.

On the Internet...

Facts

"...radiant heat can crack or otherwise damage fine wood flooring.", or "Radiant heat will cause solid hardwood flooring to dry out too much and cause it to crack and shrink apart."

Beans first law of radiant heated hardwood: 100% of all hardwood flooring complaints in buildings heated exclusively with forced air did not have radiant floor heating to blame. The primary cause of dimensional changes in wood is moisture not heat. If this messes with your head, ask a furniture craftsman schooled in the ways from the old country. See below for the difference between heat and temperature.

On the Internet...

Facts

"...a flexible plastic tubing called "PEX" -- a polyurethane.."

PEX is actually PE-X, an acronym for cross (X) linked polyethylene (PE). There are different types of PE-X designated by a letter which is an indicator of the method used to cross link the molecules, for example, PE-Xa, PE-Xb etc...

On the Internet...

Facts

"Comfort, in fact, is the No. 1 advantage (with radiant floor heating) with its warm-feet, cool-head environment."

There is no single ideal floor surface temperature for everyone and in all applications - as it depends on the heat loss of the room, the foot wear and the conductivity of the flooring and the occupants subjective view of comfort.

Generally speaking, when wearing normal footwear -  floor surface temperatures are optimal around 75 deg F to 77 deg F...however keep in mind - air temperatures are not the same as surface temperatures - when we talk air - the smaller the air temperature difference between the ankles and head the more comfortable people will be (favoring warm below to cool above)...See our pages on skin and comfort and temperature stratification.

On the Internet...

Facts

"A wet system ..."

Refers to poured floors like cement or gypsum based topping systems - no one we know wants to live with a wet system....we suggest people use poured floor system instead of wet.

On the Internet...

Facts

"A dry system..."

Refers to sub floor systems installed under, in or on top of the sub floor, - no one we know wants to live with a dry system....we suggest people use subfloor system instead of dry.

On the Internet...

Facts

"Heat and temperature are essentially the same thing..."

No they are not - heat is a form of energy - temperature is not. Substances can have the same temperature but hold different amounts of heat. Temperature is an indicator of the speed of the molecules. You can apply more heat to speed up the molecules i.e. raise the temperature of the substance.

This is also a good place to point out that in reality there is no such thing as 'radiant heat'. I know it's used all the time but in reality, radiant is an electromagnetic energy wave without heat...the heat comes from the stimulation of molecules in a substance receiving the radiant energy.

On the Internet...

Facts

"The Romans invented radiant floor heating..."

Inhabitants of Asia (Korea and China) were the first by several thousands of years. Per building, Korea has the most radiant heating anywhere in the world. Northern Europe, Germany, Sweden, Denmark etc... come in second.

On the Internet...

Facts

"...the thicker the slab, the more it will heat up and radiate..."

Slab thickness has nothing to do with how well a concrete surface will radiate - this is a function of its emissivity. A thicker slab (yes) will hold more energy in the form heat but if the surface temperature of the slab is the same as all the surface temperatures in the room there will be no radiant transfer regardless of how thick the slab is or how much energy it holds.

On the Internet...

Facts

"So, a lot of people will install a foil double-poly reflective insulation. They use a barrier insulation under the slab and help keep the radiant heat moving up, not down." or "the portion of radiant heat being lost into the ground below."
 

There is no radiant heat transfer from the slab to the ground its conductive ergo there is no need for a reflective barrier. See our pages on reflective barriers and under slab insulation.

On the Internet...

Facts

The piping can be wrought iron, steel, copper or plastic, including polybutylene and polyethylene. The steel and wrought iron are typically only used for floors. They are too heavy for walls and ceilings.

Steel, iron, copper...these haven't been used in radiant systems for a long time and polybutylene hasn't been readily available in North America for well over a decade.

On the Internet...

Facts

"Warm air rises and much is lost, making forced air heating less energy efficient. Radiant heating works by transferring heat to objects, so when placed beneath wood flooring it heats the floor. Since less heat is lost through the air, radiant heating is more energy efficient than forced air heating systems."

All things being equal, radiant is more effective at conditioning people and spaces but it is not necessarily more efficient. Efficiency is a complex discussion because it involves other external systems and a few other terms such a exergy and efficacy- something most people are not familiar with...also there is an inverse relationship between building performance and the need for mechanical efficiency. The undeniable and undisputable fact is - is radiant is an enabler. It enables higher combustion and compression efficiency. But a lousy building with high efficiency boilers and heat pumps can still lose more heat than a good building with mid efficiency systems...ergo any statement about radiant being more efficient should be questioned for clarity - in most heating case it is difficult to scientifically support the statement unless there are mitigating circumstances. However, there can be significant electrical power conservation with radiant cooling systems. See below for efficiency claims and see this overview of energy, exergy, efficiency, entropy and efficacy or what we call the E5 factors.

On the Internet...

Facts

"Electric radiant floor heating is widely considered to be the most energy efficient heating process currently available."

Electricity generated by combustion processes can have as much as 70% losses between the point of generation and the home...i.e. of the 100 units of energy to produce electricity you get between 20 and 30 units at the plug - far from being the most energy efficient process. Hydro, geo or wind generated power - now that's a different story. See below for more efficiency claims.

On the Internet...

Facts

"brand x insulation forces the heat from the radiant heat system up to the floor's surface." or, "brand x insulations help to retain the heat generated by the radiant heating system blocking it from escaping into the ground." or "Reflects cold back into the ground."

Under slab insulation does not force heat up to the floor surface nor block it from going down nor does it reflect cold nor is the heat within a concrete slab being transferred by radiation...insulation is resistance...it slows or impedes the flow of energy in the form of heat travelling from hot to cold via conduction...radiation only comes to play at the uppermost surface of the floor. Learn more about reflective insulation scams.

On the Internet...

Facts

"...savings associated with the use of radiant floor heating range from 10% - 40% on utility bills." or "it saves 30 percent in energy costs", or "Radiant heat can save up to 50% in total heating cost " or " can save up to 15% on heating bills ..." or "...saves 20 to 40 % on monthly heating ..." or "you can save 10-30 percent on your monthly heating bills" or "can save 40% off your heating bill" or " can save consumers as much as 50% in energy usage"  or " radiant floor heating systems that should be up to 80 percent more energy efficient." or "They are typically 40 percent more efficient "...and this next one is our favorite claim of all time..."All radiant heat systems are 100 percent efficient at any capacity."

There is so much anecdotal claims floating around you can pretty much find whatever you want for savings depending on what source you want to believe...the reality is  - there is no formal independent scientific residential research that we are aware of that supports any of these claims...so here again are the facts...radiant is an enabler...and by that we mean that radiant enables condensing boilers, chillers or heat pumps to operate at their maximum efficiency - that's it. If you have a lousy house nothing is going to save you from high energy bills but what you will get is maximum performance from your radiant system while the building loses lots of heat. If you want to reduce your heating bills first build a high performance building and then get the maximum efficiency from your heating system by using low temperature radiant heating. (caveat...in cooling - scientific research and practical applications have  demonstrated significant electrical power conservation when radiant cooling is used with dedicated outdoor air systems).

On the Internet...

Facts

"...anything that can insulate the floor also reduces or slows the heat entering the space from the floor system. This in turn increases fuel consumption."

This is only partially true. Fuel consumption is a function of many things including building performance, boiler over and under sizing, types of controls,  tube spacing and fluid temperatures. Floor coverings and their corresponding R-value are compensated for by tube spacing which influences fluid temperatures (in heating, more tube  =  lower temperature = better efficiency, in cooling more tube = higher temperatures = better efficiency). A correctly designed carpeted floor can operate at the same effectiveness and efficiency as a poorly designed wood or tiled floor.

On the Internet...

Facts

"However, in humid climates, problems with over-cooling the floor could lead to wet slippery surfaces and fungus growth."

There it is again, a failure to communicate the differences between latent and sensible heat and controlling absolute moisture and dew points...see our pages on radiant cooling.

On the Internet...

Facts

"The radiant floor heating will save the most energy." or "it saves energy"...

You can't save what you have not used or as pointed out by the International Energy Association, "This claim (saves energy)...conflicts with the first law of thermodynamics stating that the total amount of energy is conserved even though forms of energy may change from one to another." In layman's term you can't create nor destroy energy ergo it cannot be saved not even by radiant floor heating systems. For a thorough study read about "exergy, entropy, energy and conservation ."

On the Internet...

Facts

"It can lower the allergens in your home by eighty percent!" or "Radiant heating will also keep your home free of air-contaminants, bacteria and dust." or "There is no hot air being blown around as with traditional systems, so no dusty sneezes."

While there are some environmental benefits to using radiant, lowering allergens by 80% or keeping your home, "free of air-contaminants, bacteria and dust" are not ones that we can find supported by research. We love to know where these came from...to get the facts read our featured article on the health effects of low temperature radiant heating systems.

On the Internet...

Facts

"radiant heating is only for new construction." or "retrofitting radiant is too difficult..." or " you have to rip up floors to have radiant heating."

One of the lowest cost, easiest and most effective ways of retrofitting radiant heat is to use the walls. If that messes with your head ask yourself why your cat or dog finds sleeping in front of a window (a wall you can see through) so comfortable...hmmm it might just be the radiant heat...who knew?  Integrating radiant into wainscoting is just one creative way of adding the beauty of woodwork and the comfort of radiant. See our pages on retrofitting radiant into existing buildings.

On the Internet...

Facts

"Floor heating comes in three varieties: electric, hydraulic (liquid), and air-based systems."

Hydraulic? Try hydronic...semantics yes but this page is about how myths get started and spread...people read hydraulic from an expert and they think brake fluid. Is "hydronic" any better - no...but it's the correct term.

On the Internet...

Facts

"glowing floor heating systems."

Glowing? Lets put this into perspective, the surface temperatures of a wood stove is over 400 degrees F with interior temperatures over 1,000 degrees F and still these temperatures are too low to glow...(pun intended)...floor heating operates below 90 deg F surface temperatures...far below glowing temperatures.  We get what the writer is trying to do - it's actually nice to think of warm floors as glowing - but if the floor were glowing - your house would be on fire.

On the Internet...

Facts

Heating the entire slab may result in a condition known as "hot foot".  Your feet and ankles are not accustomed to standing on a warm surface.  

Another twist on the above "glowing floor heating system"...once again the control of floor heating temperatures are specified in ASHRAE Standard 55 - Thermal Environmental Conditions for Human Occupancy. There is no "glowing floor" or "hot foot" unless the system has been designed and installed by amateurs. See this article on do it yourself HVAC.

On the Internet...

Facts

"Among the advantages of (radiant) are the absence of any air flow from the outdoors that has to be heated, as is the case with many forced air systems."

We're not sure if the writer was referring to exfiltration/infiltration (leakage) or ventilation (to replace exhaust air from fans) regardless both are heating loads which are independent of the type of comfort system. See dedicated outdoor air systems.

On the Internet...

Facts

"...uses a lower thermostat setting as compared to forced air system thereby lowering your energy bills."  

All things being equal, it is possible in standard construction, to theoretically achieve comfort levels with lower thermostats settings in spaces conditioned with radiant, however there is a report by CHMC stating that even though people could use a lower setting few occupants actually do. In high performance homes (<10 Btu/hr/sf) this argument becomes a moot point as the building envelope solves the energy use and minimizes the cold surface effect on the operative temperature.

On the Internet...

Facts

"radiant heating...is costly to install, and maintaining the system can be difficult."

The cost and maintenance of any mechanical system is inversely related to the complexity and efficiency of the architecture. A high performance home built to R2000 (Canada) or Passivhaus (German) standards have very simple and affordable systems.

On the Internet...

Facts

"..if you set your thermostat to about 68 degrees, the room will likely heat up to about 72 degrees. This is because the heat is sustained through the mass, so the higher the surface is heated, the lower you need to keep the boiler temperature."

Surface and boiler temperatures are set from the tube spacing, floor conductivity and heat loss.  A high performance home with conductive floors and tight tube spacing can operate at very low surface and boiler temperatures resulting in very high combustion efficiencies.

On the Internet...

Facts

"Hydronic radiant floor heating systems use boiling water in the pipes to generate heat..."

Water is not boiled in a hydronic system. A high performance home with conductive floors with tight tube spacing the temperature of the water is similar to the core temperatures found in your own body, i.e. 85 deg F to 100 deg F.

On the Internet...

Facts

Hydronic radiant floor heating systems are also environmentally friendly as they have an option of recycling your used water. In fact, it is also a part of purifying your water where the water is brought to a boil.

That statement is by far the most bizarre statement we have come across....Fact: hydronic radiant floor heating systems do not recycle your used water and are not part of purifying water for domestic use. Read here about using domestic water heaters for space heating.

On the Internet...

Facts

"The heat energy that is created by warm water, flows through pipes..."

Heat 'is' energy and its not created by warm water flow - energy in the form of heat is transferred into the water through the heat exchanger of the boiler or heat pump.

more to come...if you want us to look at a questionable statement let us know at the forum.