First of all, is it really as comfortable as I'm led to believe? I've only toured one home with such a system and it was on a mild day so I don't know that it was really a good test of the heat output. I have to admit the floors under my stocking feet were toasty, even over the areas of the home that were carpeted. And what about carpet and radiant heat? Are you limited to thin carpet and thin padding less you block the heat? And if you do lay carpet must you run the circulating water at a much higher temp to defeat the carpet?

What about the differences in installation? I know there is under floor installation (staple up system?) and direct installation in the floor(installed in the subfloor such as Warmboard or installed in a concrete slab). As I understand it, the concrete slab installation will hold the heat longer (taking advantage of the thermal mass of the slab) - but takes longer to respond to thermostat settings. Is this true? Can anyone give feedback on their choice of system with pros and cons?

And finally, what happens in the event the tubes imbedded in the floor leak, come apart, rust, etc...or some other failure? I'm especially concerned about a failure in the slab installation. Wouldn't this require pulling up the floor coverings and jackhammering through the concrete to get to the failure? Provided you could even locate the point of failure?

I'm leaning towards building with SIPs so I hope to have a very well-insulated and weather tight structure if this makes a difference in selecting a radiant floor installation. I'd appreciate any comments and suggestions. Thanks.

The pex tubing contains the flowing water, but the heat has to be able to radiate, so hardwood, ceramic tile or other similar type flooring is used. Carpets act as an insulator, slowing the transfer of heat from the pex.

Pex has been around since the '60s and has proven itself reliable. It comes in very long coils, so you don't have to worry about unseen fittings. Any improper installation can cause the tubing to wear through, but it has an excellent track record.

Concrete takes longer to heat, but holds the heat longer, as you suspect.

It's not uncommon in the Northwest to use an electric boiler in conjunction with radiant heat. They are about the size of a suitcase and hang on a wall.

I have water/baseboard radiant heat, but if I could do it over, I'd use the "in floor" system.

Radiant in-floor is by far the most comfortable heat I've ever experienced. Period. Not only that; but it affords NO restrictions for vents, registers etc in regards to furntiure placement.

I did a staple-up installation. While more labor intensive than other ways; I did so as the cost was signifigantly less as I supplied the labor. As far as performance goes, slab is probably ideal ( thermally, not structurally or repair-wise ). A good staple up installation or the "Warmboard" types are probably very similar in performance; but again staple up has the lead here strictly from the standpoint of serviceability.

Embedded in a slab, yeah you're gonna be tearing up concrete IF you ever have a problem. You'll be tearing up flooring with Warmboard and such IF you've got a problem. With staple-up you can work from below; usually just pulling some insulation out. I've done exactly that; since I had the misfortune of driving a nail through my PEX . . . Duh !

PEX has a LONG history; believe Europe has used it since after around WW2 . . . it's lifetime is longer than you or me . . . .

I found it very effective to insulate by using Reflectix directly under the radiant tubing / plates; then below that rigid foam. Very good thermal barrier, clean and easy to put in, easy to remove IF you ever need to. The heck with f'glass etc . . . . and all that mess.

Hardwoods play just fine with it . . . and in fact become some of the thermal mass that helps it work well. Carpeting will impede transfer; you're better off without it though it will still work . . but just remember it becomes an insulator in the path that you WANT the heat to take . . . .

I use a Munchkin "boiler" . . very high efficiency condensing / modulating type . . which can also do your domestic hot water heating . . they ARE small . . and silent. There are other brands out there too that are very similar.

I bought all the materials for 1800 sq ft for $ 2500 back in '98 . . that may be a bit dated now; but again I did staple up / self install BECAUSE it was much less expensive. No special skills needed . . but a good bit of work. I'm in central New York state where it gets COLD . . . and have eight years on this system / hardwood floors throughout . . .and NO regrets of any kind. One interesting thing that happens . .. when it gets REALLY cold . . like below zero . . . the floors get "warmer" . . . nothing beats hopping out of the shower on a below zero day . . onto a nice warm tile floor . . . .

I did a write-up w/pix on my system a few years back; send me a REAL email adress to my member email and I can forward it along to you if you're interested.

Good luck . . . Bob

PEX is polyproplene. It is a durable plastic that will probably last longer than man. Battery cases are made of Polyproplene, Road signs are made of polyproplene, Barrels used in traffic bumpers are made of polyproplene. It is a soft yeilding plastic, that can flex.

Several years ago in Dallas, we had a major problem with PEX based water pipes in homes. The connections would force the pipe to split. Several thousand homes were almost condemmed, because of impropper terminations of PEX. If terminations are made in open areas, the tubing will probably be fine. Nails, and sharp objects touching the tubing will cause problems, but nails and sharp objects also cause problems with electricity and copper pipe.

There are 2 types of PEX plumbing pipe. One is made for continuous heat. Use this type. The other type probably will work, but is not recommended for radiant systems.

Anything with a fluid inside will eventually leak. Waterpipes leak. The risk in concrete, is the same as any risk. In the event that it leaks, you fix the leak. It may need a $.50 repair coupling, and $2000 labor, but everything cost money for maintenance.

Radiant water is a good medium for solar water panels. This can reduce your heating operating costs. In my climate, a solar heat based system and hot water, will pay for it's self within 7-10 years. I only need heat for 3-4 months of the year. The cost is about 2/3 of geothermal. Radiant heat can be retrofitted if on a pier and beam foundation. Or if you have an exposed ceiling in your basement.

Radiant systems are more expensive than forced air systems. If done right, a forced air system is not drafty. You only feel air up close to the registers. If the registers are high on the wall or in the ceiling, you should never feel a draft. You should never hear the air movement. If you hear air, then the ducts are not right.

Yes, 1000 times yes.

As for leaking, it's possible, but pex has shown to be extremely leak resistant over long periods of time.

You probably won't need to worry about the tubing leaking in your life time, unless you manage to drive a nail through it.

If you do go with radiant, consider a liquid silicone solution for heat transfer.

Got a book somewhere in my collection from Dupont regarding the advantages of silicone in hot liquid applications.

Some of the advantages are no rust issues, no dissolved oxygen issues, higher density for more efficient heat transfer, won't freeze if left in the elements, and others that I have forgotten about.

Of all of the items mentioned, the safety of not freezing seems to be the greatest advantage, especially if you live in cold weather areas and worry about the heating system breaking down when you are away for extended periods of time.

Biggest downside is the initial cost for filling the system up which would probably be made up by saved pump costs and other things affected by plain water in the system.

Good luck!

Fairyprincess

Yes...but...

Radiant heating compensates for buildings inefficiencies by raising the temperature of the building mass, which reduces your body’s heat loss vis a vis radiant transfer. Why? Because of the nominal 400 Btu/hr your body needs to shed to stay comfortable, 50 to 60% of it is transferred via radiant at a met rate of 1.0 (low level activities such as sitting). If the body loses more than 400 Btu/hr it feels cold or chilled and this happens when the surfaces in the building are lower than your skin temperature. You can experiment with radiant sensation at home by standing in front of a cold window or a hot oven. By raising the building mass and thus the surface temperatures, you are reducing your body’s heat loss and thus improving your comfort.

But...you can achieve simlar comfort by improving the building efficiency.

Keep in mind that there are in all eight measurable metrics in studying thermal comfort. Floor surface temperature and radiant exchange are just part of the overall experience.

It should be noted that the radiant exchange in a space is why 99.99% of all thermostats sold for home heating and cooling are very poor ambassadors for the occupant to the mechanical system – they don’t measure the predominate radiant heat transfer between the occupant and the space.

Some manufactures are now producing what is called operative thermostats for improved comfort but these are not mainstream as yet. Competent designers and installers can simulate operative temperature with a matrix of sensors embedded in the building mass plus a single sensor for air temperature.

Incidentally CMHC radiant heating studies have found that though one can be comfortable at lower thermostats settings few if any actually operate their thermostats any differently from those using forced air.

As far as operating costs radiant in of itself does not cost anything to run – it’s the equipment it is connected to that requires power and fuel. Comparison studies by the DoE show there are little if any fuel saving between hot air or hot water systems in similar homes using similar combustion efficient equipment. There are some electrical savings with water-based systems due to lower power requirements moving water instead of air. However, properly designer radiant will make heat pumps, condensing boilers and chillers operate at their maximum efficiency. In most cases where occupants have experienced abnormal fuel and power cost associated with radiant it's because the building had construction flaws such as little, none or unsuitable underslab insulation including the use of bubble foil products. Other common flaws include unsealed and uninsulated trimmer and header joists.

As far as capital cost, over and above the radiant system for heating or sensible cooling, the occupant will need to have a system for addressing ventilation (exhaust and make up air), air filtration, and humidification or dehumidification (latent cooling) and a means of heating domestic water. If you were my client and this was your retirement home we would advise you budget between 10% to 15% of the construction cost for your COMPLETE radiant based HVAC system and this would include rough in for domestic plumbing…or if you do not want to invest this amount in mechanical heating and sensible cooling solutions then invest the difference in the building envelope. My experience is this usually freaks out the do it yourselfer, the mass track home builder, the person who has not done their homework on indoor environmental quality or those who have never experienced what we call "The Total Comfort System". Usually industry budgets 50% of what it should cost and as a result we have a population of people paying for inefficiencies, living in discomfort experiencing health issues related to building performance and quality.

If you want to do your own homework google ‘thermal comfort research’ and browse the reports. Also do a google search of "thermal comfort tools" or "Dr. Marsh's Comfort Calculator".

My office (8500 sf) and home (3200 sf) are examples of what we recommended to people exploring high quality environments. You can see both of these buildings and mechanical systems on line. A competent designer can help you choose the best heating plant based on capital and operating costs.

The short stokes: For every dollar you do not spend on the building efficiency and HVAC system you purchase varying levels of discomfort and inefficiencies.

[And what about carpet and radiant heat?]

Every material has a characteristic which tells us about its radiant capabilities. The word is called emissivity. Almost all floor coverings have emissivity values in excess of 0.9 ( 1.0 is the perfect emitter and absorber of radiant energy / 0.0 is the perfect reflector). As a result most floor coverings are all very good radiators. Incidentally the human skin has a nominal emissivity = 0.97 which makes it close to the perfect surface for absorbing and releasing radiant energy. Whomever one believes is responsible for creating humanity - they certainly knew about radiant transfer.

Short Strokes: Floor coverings influence the average fluid temperature, which is a function of the tube spacing. For a given R value above the tubes the closer the spacing the lower the fluid temperature. By the way there are carpet underlayments designed specifically for radiant heating. Use the web again to research this.

[What about the differences in installation?]
A qualified designer working with your architect and builder should make all of the evaluations and recommendations for installation type. The heating and cooling load, the mass of the building, and the operating temperatures between minimum and maximum loads which are functions of the tube spacing and floor R values are all part of a ‘system’. There are many combinations of floors/tube/controls making up different system – some may be better suited for your home. For example, a home standard constructed in a geographic area which experiences drastic temperature changes benefits from high responsive system like the Warmboard, or QuickTrac systems. Radiant systems are not air temperature responsive they respond to surface temperature changes, which are function of the building mass. Changing thermostat settings might be fine for air based systems but for radiant it’s a recipe for instability and discomfort. Ideally for good control the flow in the pipes should remain constant and the fluid temperature lowered or raised in response to changes in outdoor temperature. This is a big topic beyond the context of this forum but if you want to learn more let me know.

[And finally, what happens in the event the tubes imbedded in the floor leak, come apart, rust, etc...or some other failure?]

The evolution of PEX (PE = Polyethylene, X = crosslinking of molecules) began in 1933 in the ICI labs in England. ICI sold licenses to BASF and others following WWII. Hoechst (now Bassell) began long term testing in 1959 giving at that time a 50 plus year life expectancy. Today we know that it will last well over 100 years. It is a fascinating history and you can read about it in detail in an upcoming issue of HPAC Canada. It is a pipe with characteristic acceptable for use in industrial and military applications. In fact the home system will never operate even close to its maximum capabilities. There are PEX heated emergency helipads in -60 deg F artic climates in Canada and radiant cooled airports in Bangkok…your home is child’s play for the product. Damage is usually an installation issue and most often due to inexperienced installers or lack of communication between trades. Having said that, there exists four types of PEX (PEX-a, b, c or d) available with or without oxygen barriers. The choice between barriered and non-barriered is a separate topic and I can elaborate if requested. All combinations are produced for continuous heating or cooling. Some have better pipe and fitting characteristic then others. There are three brands in particular that use an extrusion method for a greater robust pipe and fitting combination as such you will pay more for these higher quality products. Keep in mind that the pipe and fittings represent the least cost components in the overall mechanical system and are the least accessible so PEX pipe and fittings is not where to save money on a project. I’ve not heard of the Dallas project but it sounds like part of a multiplayer Pex-Al-Pex product or part of the PolyB fiasco both not related to your basic PEX.

Short Strokes: Work with a certified designer and installer. RPA, HRAI and CHC are just a few certification bodies in North America.
If in the rare event, thermography is a acceptable method to locate failures in pipes.

[I'm leaning towards building with SIPs … if this makes a difference in selecting a radiant floor installation.]

Yes it will make a difference to your perception of ‘warm floors’. The more efficient the home the less heat is required from the floor which means your floors may be comfortable but not necessarily warm to the touch. This occurs ‘around’ loads less than 20 Btu/hr/sf.

As far as freezing...take two identical homes – one heated with forced air and the other with a water based radiant system. Put both into a electromechanical failure mode. Which home will freeze up first and what will be the first thing to burst? The radiant heated home gives the occupant and their contents a safety factor but for added insurance for areas where fuel and power failures are common or where the home is unoccupied for long periods of time, a suitable mix of propylene glycol and water can be used. By the way if its just a fuel failure, where the power is still present, its possible using the circulators (pumps) to move heat from one area of the home to others further extending the safety factor.

100 year lifespan of pex doesn't give me much comfort.

Please tell us more about Radiant Cooled. Is this direct cooled
or radiant to air cooling?

Thanks
Chris

???

Why not?

That's as good, if not better, than any other product currently on the market.

Here is an exercise for those who want to compare products. Call up a local pipe supplier and ask them for a written warranty for copper, steel and PEX. Let us know what you find. Don't be surprised to find no warranty for copper or steel but 25 years plus for PEX and yet the general public would think otherwise.

On radiant cooling…it important to understand the difference between latent and sensible cooling, long and short wave radiation and the role of convective heat transfer.

Sensible radiant cooling is partially what you feel when you walk into an underground parkade in the hot summer months or what you feel when you walk into the freezer section at your local supermarket. In both cases your warm body will release energy via radiation to the cooler surfaces and that’s one of the metrics which contributes to your cooling comfort. Radiant cooling is the oldest form of comfort conditioning – ask the cave dwellers of years gone by.

Sensible loads are both long and short wave radiation, which comes from solar gains, lights, motors (washing machines, dryers, ceiling fans etc), compressors (freezers and fridges), resistance elements (stoves and ovens), electronics (TV, stereos, computers) and your body. Basically all things inside your home which use electricity and contribute to the cooling load. A radiant floor can absorb as much as a nominal 30 Btu/hr/sf of direct short wave solar radiation and an additional nominal 14 Btu/hr/sf of long wave radiation. Excluding discussion on short wave radiation, ceilings and walls have a higher capacity for cooling (radiant and convective) because of the air buoyancy effect. There is no or little convective cooling with radiant floors.

To prevent condensation the humidity must be regulated (dehumidified) to a nominal 40% rh and the floor temperature maintained above 66 deg F (for comfort and dew point) - which is regulate by the tube spacing and fluid temperature and a function of the floor R value and sensible cooling load . This is not a problem for commercial projects but for housing it is a problem and it’s called the human factor…kids (and spouses) leaving window and doors open. Radiant cooling for residential applications requires a more mature, educated and responsible occupant.

A Google search on radiant cooling will further serve your curiosity.

The Dallas fiasco was with the connectors. Installers did not have a clue and made connections inside of walls. Many homes had burst pipes inside of the walls. Had the connections been made outside of the walls, the problem would have been less severe. Until recently, gas service line was Poly pipe to the outside of the house, then black iron inside. I have seen several homes recently with poly pipe into the attic.

The usage of poly does not bother me as much as when it is not protected from damage. The pipe in question only needed someone to fall on top of the pipe header, and it could have caused problems. Copper and Iron pipe are more durable. With this said, Dad and I, laid an iron sewer in the 1960's. The rubber connectors had a 50 year guarantee. The company is gone, and so are the connectors. Roots are getting into the pipe. So much for guarantees. It has only been about 40 years.

Flexible poly pipe is used in many critical usages. It seems to work fine, when installed correctly. Last week, I found a copper joint that was leaking. If soldered properly, it should never leak. The house was about 15 years old, and it was leaking. So much for copper fittings that just about everyone can sweat.

Automobile batteries use Poly cases. It is very durable, with the exception of direct sunlight. Battery manufacturers never expected batteries to lie in the sun until they rot. It happens. Poly can have a catalyst added that prevents the pipe from rotting in direct sunlight.

I briefly toyed with the idea of using PEX for heating supply and return lines for a second boiler installation in my house. It would have saved me countless hours of labor and several hundred dollars in material savings, but I decided to go with copper lines. They'll probably be there when the house rots away in a few centuries, and because I just don't trust "plastic". But that doesn't take away from your interesting essay.

What about it?

Go on to any search engine and type in the following: copper plumbing pinhole leak.

You'll get a lot of hits for mid-line leaks in copper pipes.

Copper pipe is wonderful stuff. It's easy to work with, doesn't require a large number of expensive speciality tools, and it's relatively durable.

But it ages, and as a metal it's reactive.

The problems with using copper pipe in radiant applications, especially in in-slab applications, are well known.

Large swaths of Europe were rebuilt after WW II using early pex piping. Many of these systems are still in daily use with few reported problems.

Am I saying that pex is perfect? Nope.

But I am saying that pex's qualities and durability are well known factors now, and judging by what we're seeing so far, I don't doubt for a moment the 100 year lifespan.

However, with acidic city or well water, copper is not a good choice because of pinhole leaks caused by low PH water.

Filled with 60 deg F water and heated to 180 deg F would cause a 200 ft length to expand by [(180 - 60)/10] x 2 x 1.1 = 26 inches. That is the reason why I wouldn’t use PEX for S & R lines on high temperature devices. Too much expansion and contraction.

In radiant applications in concrete the expansion is less since the operating temperatures are lower plus any stress created by the expansion are absorbed by the walls of the pipe since it is held firm in place by the concrete. The amount of this stress is too low to affect the integrity of PEX pipe.

How did we go from radiant heating systems to potable water systems?

Unfortunately, pinhole leaks in copper apparently aren't restricted to areas where the water is acidic, either. Far more prevalent in those areas where the water is acidic, but certainly not unknown in areas where the PH is more basic.

Maybe some other people in the forum could share their experience with pinhole leaks in supply and return lines only.

That's the entire problem with leaking copper pipes in radiant slabs, isn't it? Pinholes developing in the pipes?

Granted, those pinholes apparently start on the outside and work their way in (instead of inside and work their way out as on potable water systems). Maybe I'm guilty of using the term incorrectly and being too general in my comments.

But the failure rate among copper tubed, concrete slab radiant floors has been significant. Many of the floors in the Levittown communities started leaking within 30 years of installation.

My choice of using copper piping is for feed and return lines on a baseboard system. That was all I ever said. My second system if for baseboard heat and I did forget to say that, but at that point the posting had turned to pex tubing and away from strictly radiant heating.

Let's blame healthyheating. :)

It blows.

And not the good kind of blows.

It’s hard for the traditional HVAC person to separate indoor air quality from indoor comfort quality. They are, yes, part of the overall indoor environmental quality equation but they are in fact two separate metrics with different requirements. That’s why we have ASHRAE Standard 62 Ventilation for Acceptable Indoor Air Quality and ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy. Both of these industry standards reference each other but they are also very clear that they do not and can not address each other’s parameters. Air systems are very good at what they do [ventilation, filtration,(de)humidification, heat recovery] but they cannot effectively address the all important radiant exchange which is a controlling factor in comfort. Again emphasizing that the radiant component can be controlled with an architectural and/or a mechanical solution.

razl, radiant systems are used in all types of small and large buildings from dog kennels, motor homes to high rises. There are no concerns that have not already been addresses a thousand times before. A certified designer can address your specific requirements. If you want to do some basic research on architectural and mechanical requirements browse through the various images found at the link below. Please note this is a large .pdf image file and can take up to 45 to 60 seconds to load. But once it's up you can zoom in and out to see the details.

As far as hot water heating in general, there are literally millions of hot water heated projects with or without glycol. Just take a look at any downtown core in America in a heating climate. In our -10 deg F to -60 deg F provincial neighborhood it’s virtually impossible to count how many hot water projects have glycol…they are everywhere one looks. Most are piped in copper or steel. The exception is radiant floors or snow ice melting systems, which are 99% PEX.

[As I said before, I do believe that radiant gives off a more comfortable heat.]
It’s interesting and very common to refer to mechanical systems ‘giving off heat’ as opposed to talking about mechanical systems used in heating to prevent the body from giving off its own heat or in cooling to encourage the body to shed its heat…same thing really just a humanistic way of looking at it.

[…thank you…] My pleasure.

[However, now that furnace efficencies are topping out, the hvac industry is now focusing on improving IAQ (which radiant heating does not address).]
See the various links below on efficiencies (allow a bit of time for some to laod). Here in Canada, we’ve been focusing on IAQ since the 70’s but our motive to legislate ventilation and thus IAQ came from Europe. It came to a head when we launched the R2000 Housing Program, which revealed how quickly people can become sick in unventilated highly efficient homes. So we are required to ventilate mechanically our homes regardless of the heating system. It’s why HRV’s and radiant systems are common practice in this and other countries…again separating the ventilation from the heating.

[Many health orginazations are also focusing on the issue of Indoor Air Quality ]
Yes it is attracting attention.
See this link IAQ Report from California and this from the Healthy Indoor Partnership. You will see global collaboration from various industry groups on this topic over the next few years.

[Also, ...rates on the rise, heating efficency is more importiant now that ever...and hot water dont come close. I would be interested in any links you could provide.]
This excerpt from the ASHRAE Green Guide, The Design, Construction, and Operation of Sustainable Buildings may interest you… "…it is important to understand that properly distributed air to heat and cool spaces in a building is less efficient, from an energy usage perspective than using hydronic or steam distribution." The 55,000 members of ASHRAE meet twice a year and encourage opposing views so if you know something they don’t, they’d be happy to hear what you have to say.

In the meantime, here are two documents to get you started.
See page 6 and 7 of the Schenectady Habitat for Humanity Research Project, Forced Air vs Radiant and the Energy Consumption Characteristics of
Commercial Building HVAC Systems Volume III: Energy Savings Potential The latter document is for commercial projects but the principles are the same. There are little savings in heating (using combustion) but radiant cooling with dedicated outdoor ventilation systems have major electrical savings as shown in the report.

You should also keep your eye on this NRCan Radiant vs Forced Air Research Project.

My guess they will conclude what the Schenectady Project discovered. No differences in energy use (again combustion) but higher levels of comfort with the radiant system.

Probably one of the best sites in the world to visits is the International Energy Association Exergy pages:
General Page
Library of Downloads

Ultimately building efficiency is more important that mechanical and electrical efficiency.

In other words, the most efficient HVAC system is the one, which never runs.

________________________

On the evacuated tube collectors, in another career I specified them in a 1989/90 American Science Foundation Project in the Antartic. It was a joint US/Canadian mission with VisionWall suppling high performance windows, Atco Structures the buildings and we designed and supplied the solar heating systems. Best resource is Thermomax who hold(held)the patents and make the tubes for many others.

There are off the shelf residential boilers with combustion efficiencies of 98% at 30% loads down to 95% at 100 % loads when operating between 85 deg F to 105 deg F - which are common temperatures for radiant systems in energy efficient homes. Have your suppliers source them out.

These boilers have A.F.U.E. ratings as high as 95% or another way is to say that at 95%, 5% of the heat released from the combustion does not end up in the water.

I am not a combustion expert by any means so unless my understanding of heat exchange is skewed it seems to me the heat exchange between combustion gases and a water (boiler) or air (furnace) exchanger would be a function of the product characteristics on either side of the exchanger. These characteristics would be the specific heat (heat capacity x density), change in temperature (LMTD), the flow rates plus the conductivity and design of the exchanger itself.

Since the products of combustion would be the same for a furnace or boiler it is a moot point of discussion other than to define, what percentage of the heat released does not get transferred over. In other words a A.F.U.E. rated 95% furnace or a A.F.U.E. 95% boiler when fed equal quantities of energy, which gets released in the form of heat, would both have 5% of the heat being non recoverable. If owners of the furnace or boiler were charged on what was non-recoverable their gas bills would be the same. So if this is true then what’s left is power consumption and for a given heat load, compared to boilers, furnaces must move considerable more volume across the exchanger because air has a significantly lower density and heat capacity and thus one of the reason for larger motor horsepower. This is one of the reasons why researchers find (when loads and effcienicesi are similar) there is no noticeable difference in fuel costs and only a slight savings in power with the boiler system. It’s also why, if you have read the reports above, radiant cooling systems with dedicated outdoor air systems have significantly lower power bills (up to a nominal 60% less) since the air is not used for sensible cooling, the volume of air moved for ventilation and latent cooling can be drastically reduced (depends on project geography) which reduces the power load.

I am here to learn as well from you and others who can contribute to this discussion - it would be great to hear your thoughts.
___________________________

The link below from Washington State University is a very simplified but fun tool to play with.

Text Source

Tomas is a difficult man to reach but if you wish to explore the topic detail I can try to arrange it.

Contact me via my profile.