I know to use a certain type of carpet pad under the carpet to help conduct the heat better. But I am just curious if the floor-heat does a good job of heating the rooms under all types of flooring. We will have forced air heat for backup heat (and the furnace will be used for A/C in the summer months), but hoping that the in floor heat will do a good job of heating our home. We live in South Dakota and plan for 10-11 foot ceilings throughout the main level.

Depending on flooring and heat requirements, floor temp, thus output is influenced by tube size, circuit lengths, flow rate, tube spacing and water temp.

What are you planning to put under the basement slab to prevent that heat from going mostly down into the ground? You want a thermal break so the heat doesn't take the path of least resistance and simply go into Mother Earth.

-david

Since it appears that radiant will be your primary heat source, with force air backup, you need to ensure that the heat delivered to the room is sufficient to keep the room warm. With a carpeted floor, the rate of heat transfer to the room is half or less than a tile floor.

In addition, how the tubing is installed makes a profound difference in heat transfer. Installing it in a concrete slab with tile on it transfers heat the fastest/most effectively. Installing the tubing hanging under a wood floor with a carpet on top transfers heat very slowly/ineffectively.

The design will take into account the type of floor cover, the amount of tubing, the temperature of the circulating water etc.

For example, in a concrete slab with tile, you might be able to use 85F water circulating. With tubes under the floor, with tile, you might need 130F water. And with carpet, you might not get enough heat out with even 180F water.

As the other poster noted, in basement slabs, you have to be very careful about insulating sufficiently under the slab. I recently participated in a length discussion with a number of pros about this. All agreed that no insulation is a disaster. 1" is very inadequate. 4" or more (R-20) is really at least what you should be shooting for. And this was with a bare concrete floor. With a carpeted floor, you want to significantly increase this. Also, keep in mind that the bubble foil radiant barrier does not work when used in a slab application. If any radiant installers want to use this as your insulation, send them packing, as they don't know what they're doing. Also, you need to be 100% sure that the slab edge is properly insulated.

Since you noted that you're looking at 80% carpeted basement, if it were my own house, I would scrap the radiant and use baseboard heaters. Maybe just do radiant under the exposed portion, like if it were a bathroom.

-Ted

A friend has gas fired hydronic radiant in his whole bungalow and basement, but he did the gypsum slurry and laminate flooring except for their master bedroom. The floor is really nice and warm in -25C days, the basement is equally comfortable, and he even has slab heat in his garage. I'm jealous.....:)

If you want that much carpet, I concur, save the expense and just use forced air throughout with in floor heat in your bathroom. We used electric mats for ours.

First ….surface conditioning using pipes includes melting snow for runaways and bridges, freezing water for ice rinks and preventing ground frost in industrial food freezers - so warming up your flooring - although a legitimate concern for the uninitiated - is in fact child’s play for a competent radiant heat designer.

In regards to floorings….

All floor coverings have similar emissivity’s (you can use this word to impress your friends at the next wedding).

What does this mean? In plain language - it means that a carpeted floor, wood floor or bare concrete operating at the same surface temperature have almost identical surface outputs(if you want the techomuckymuck explanation let me know).

The differences between floor coverings has more to do with their resistance (R-value or the difference between a wind breaker or a down jacket) which means having to adjust the design fluid temperature in the pipes up or down, or increase or decrease the amount of pipe in the floor or both - all depending on the building load and choice of floor covering - the most important of these is building performance.
Why? Because building performance drives the surface temperature of the floor.

A high performance building (less than a nominal 12 Btu/hr sf) needs a low surface temperature - a low performance building – one that sucks - (> 20 Btu/hr sf) needs a high surface temperature. For magnitude - one Btu can be imagined as the amount of heat one match delivers…a really well build home under maximum load wouldn’t need to burn 12 matches every hour per square foot of floor.

Buildings that suck (lots of glass, poorly insulated, sloppy workmanship when it comes to air barriers) and have high R value floor coverings like carpets ( > 20 Btu/hr sf and R 2.0 ) need lots of pipe running at higher temperatures.

Buildings which don’t suck and use conductive floors (like tile, slate, stained concrete) need less pipe and or lower temperature…low temperature in heating = high efficiency in boilers and heat pumps.

However buildings which don’t suck (high performance) can successfully use carpet with less pipe and lower temperatures conversely buildings which do suck but use tile have to use lots of pipe at higher temperatures.

Do you see the relationship? It’s not just about the flooring it’s about the system – the building (affects heating load – what you pay the utilities) – the flooring affects resistance) – the tube spacing (affects fluid temperature – affects efficiency) ….they’re all joined at the hip...it’s like girls going to the bathroom – one for all – all for one kind of stuff.

Buildings which don’t suck and use natural conductive floors tend to be more comfortable, have lower emissions of volatile organic compounds (better IAQ) and use significantly less energy…we have a rating scale for these homes…this example would get the AAA rating – the highest.

So if you want really good indoor air quality, and really low energy consumption and superb comfort – build a high performance home, with highly conductive radiant floors - low VOC finishes – connect the whole thing up to a condensing boiler /heat pump with zone control appliances and call it a day.

If you do a really really (yes really) good job with the building and make wise choices for flooring - you may be able to get rid of the forced air system and its refrigerant cooling altogether - at less than 10 Btu/hr/sf cooling load puts you into an heat recovery ventilator for ventilation, a ground water loop/ air exchanger for dehumidifying and radiant for floor cooling. Yippee…no refrigerant, low VOC’s, high efficiencies and great comfort…. (for those that freaked over the radiant cooling – calm down - reread the word "d-e-h-u-m-i-d-i-f-y-i-n-g"…. maintain less than 45% RH and keep floors above 66 deg F and voila you can put away the Valium for when the in laws come over).

Oh and one last thing…the biggest favor you can do for yourself and family is hire a competent designer / installer someone who has been certified by the Radiant Panel Association.

The latter you don’t want to mess with – a really good HVAC system - is part banker (influences what you pay each month to the utilities), part healthcare worker (air quality and comfort quality are directly related to health, learning and productivity) and part interior designer (affects what you feel, hear, see and smell plus affects materials and finishes).

Now go forth and set an example of how housing should be built in America.
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For those that want to study up on radiant design, Google "Radiant Design Guide" compare what you thought to be true to what is presented.

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Attachment (left hand side image) is used by designers to evaluate radiant heated homes against the AAA rating of a properly built home (less than 10 Btu/hr/sf) with radiant heating, conductive floors (R values less than 1.0 ft2●h●˚F/Btu) and low fluid temperatures (less than 90 deg F).

Right hand side image shows the combustion efficiency of a boiler based on return fluid temperatures..."A" rating from fluid temperatures from left hand image = low temp on the right image = high efficiency = happy home owner

The good - building a really efficient house is definitely the way to go. The better insulated and air sealed, the more stable the temperatures, and the less it will matter what type of heating system you use. As the poster noted: "It’s not just about the flooring it’s about the system – the building (affects heating load – what you pay the utilities) – the flooring affects resistance) – the tube spacing (affects fluid temperature – affects efficiency) ….they’re all joined at the hip"

I'm not sure what the comments about VOCs have to do with heating systems. I might be missing the author's point, but the implication I get from reading the posting is that somehow radiant heating helps reduce the VOCs in your home. I know that's not the poster's point, but the way it's mixed in with talk about radiant, it's quite misleading. To clarify, VOC levels are a function of materials used in the house and the fresh air ventilation rates.

As for radiant heating efficiency. There is a lot of controversy surrounding the efficiency of radiant systems. The industry claim is that you can set your thermostats lower because the heat radiates up from the floor, resulting in greater psychological and physiological warmth. In actual practice, the studies have had conflicting results. While it is true that in a low-temperature radiant installation, you can operate water heating equipment at more efficient temperatures, it's not true that it's a slam-dunk savings in all situations. This is particularly true in basement radiant slab installations where a fraction of your heat is going downward to heat the earth or out the edge of the slab. This can easily result in a 10-30% efficiency penalty, or more depending on the installation.

The comments about the emissivity of the floor material is a red herring. While the follow-up comment about the R-value of the floor material is valid. What matters is the ability of the system to transfer heat into the living space. Tubes in concrete, exposed, is most capable. Tubes hanging in the joist bay, under the wood floor under a carpet is a worst case scenario. It is simply not true that the floor material does not make a difference! Consider this - if you have a concrete floor and a carpet, both at 70F, which one will "feel" colder when you stand on it in bare feet? The feeling of "cold" that your feet pick up is due to the heat being more effectively transferred from your feet to the concrete floor than to the carpet. The thermal conductivity of the concrete is much higher than the carpet. The floor material makes a profound difference to the actual functioning of a radiant floor heating system.

Also be aware of the flywheel effect. Large, heavy masses take a while to speed up and slow down. The same with thermal masses, like concrete slabs. They have a capacity of holding lots of energy. Because of this, they take a lot of energy to bring up to temperature. With a forced air heating system or conventional baseboard heaters, you can set the temperature back at night or when you leave for the day, saving considerable energy. With a high mass radiant system, it takes a lot more heating energy to get the slab up to temperature, so it is slower to respond. This applies to the time it takes to cool down also. Quoting from the EERE website: "Thick concrete slab systems have high heat capacity and are ideal for storing heat from solar energy systems, which have a fluctuating heat output. The downside of the thick slabs is their slow thermal response time, which makes strategies such as night or daytime setbacks difficult if not impossible. Most experts recommend maintaining a constant temperature in homes with these heating systems."

This is particularly problematic in the spring and fall, when it may be in the 40's at night but sunny and in the 60's during the day. Ask people with radiant systems about their comfort in these situations and you'll find a fair number who are dissatisfied with the comfort. This is a good reason to keep a forced air system for heating as well as the radiant. Use the forced air for primary heating during mild weather and radiant when it's colder.

The healthyheating describes this on their website under "myths". Unfortunately, the way it's discussed is highly misleading. Radiant heating systems do NOT act like heat lamps. Heat lamps operate at very high temperatures and have essentially zero heatup time. Heat lamps do work by radiant heating. In floor systems do not. They operate at very low temperatures and can take considerable time to warm up and cool down. Depending on the design, this can be many hours. Quoting from the EERE website: "Despite their name, radiant floor heating systems also depend heavily on convection, the natural circulation of heat within a room, caused by heat rising from the floor. Radiant floor heating systems are significantly different than the radiant panels used in walls and ceilings."

I don't want to seem negative on in-floor heating systems. I like them and use them in my own tiled bathroom floors. But you need to know that it is not "child's play", even for a competent installer, due to complicating factors.

Tile, slate, natural woods, concrete etc…generally have lower VOC emissions than other types of flooring but these floorings are also perceived to be cooler not because of the surface temperature but because of the thermal conductivity and its affect on comfort. See my comments below.

As for radiant heating efficiency.

Here’s a parody we did a while back on how silly it has become:

At a dinner party...
Guest #1, Hey ...does anyone know if radiant reduces your heating costs?
Guest #2, I’ve heard it can dramatically reduce your home heating costs
Guest #3, my neighbour has it and she says it will reduce heating bills by as much as 28 per cent.
Guest # 1, Wow you can save 10-30 percent on your monthly heating bills
Guest # 2, probably more like fuel savings of 15-20%
Guest # 4, No way it’s higher than that, the sales guy at the trade show said it can result in energy savings of 10 percent to 40 percent.
Guest #5, I’ve heard of 40% but 20% is the minimum.
Guest #1, so at the very least I could save 20%?
Guest # 3, more like 30%.
Guest #1, wow between 30% and 40% - that’s incredible.
Guest #5, look what it says here on the internet (on his new I-phone) energy savings of 30 percent to 50 percent
Guest #1, wow 50%! No kidding!
Guest #6, News paper the other day said it was as much as 75%.
Guest #1, is that the minimum savings?
Guest #6, I think so.
Guest #7, you mean it could be higher?
Guest # 2, dramatically higher.

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At this rate…someday…radiant will pay you and it won’t cost you a dime…yes- be careful of what you read.

The efficiency doesn’t come from radiant itself but from the fluid temperatures it can operate at.

Running a boiler at 160 deg F for 84% efficiency or one at 90 deg F for 97% efficiency doesn’t happen by accident – it requires a low temperature heating system such as radiant...note - this doesn't mean you can't achieve these efficiencies with forced air - you can - but not for the same electrical use - moving air vs moving water. Do a search of DOE Habitat for Humanity Radiant verse Forced Air.

Having said that, in high performance homes there is little energy consumption to begin with so it becomes a moot comparison…but this is not the case with cooling loads where there can be significant electrical savings. Let me know if you want to explain this.

The study you are referring to was done by CMHC, here is the document:
http://www.cmhc-schl.gc.ca/odpub/pdf/62675.pdf

Here is one of several studies on underslab insulation and radiant systems, This one by Dr. Straube at the University of Waterloo:
http://www.civil.uwaterloo.ca/BEG/Downloads/Insulation_Study.pdf

This link will take you to a review of insulation scams:
http://www.healthyheating.com/Page 55/Page_55_o_bldg_sys.htm

[It is simply not true that the floor material does not make a difference!]

Sorry can’t help you out there – you need to hit the books. The heat transfer coefficient for radiant floors is a nominal 2 Btu/hr/sf /deg F of which 50% is radiant and 50% is convective. It matters not what the flooring is…the only affect the conductivity has on the occupants is the perceived feeling of comfort not the heat exchange to the space…start your studies by reading the research of Dr. Fanger and Dr. Olesen. Also purchase a copy of ASHRAE 55-2004, Thermal Environmental Conditions for Human Occupancy…and if you’re really eager to learn obtain a copy of ASHRAE 876 TRP, Impact of Surface Characteristics on Radiant Panel Output by University of Illinois at Urbana-Champaign

[Also be aware of the flywheel effect]

Study "Thermally Activated Building Systems" or TABS.

[With a high mass radiant system, it takes a lot more heating energy to get the slab up to temperature, so it is slower to respond.]

One has to differentiate between thermal lag and thermal response… There are many types of systems all with different thermal lags…read this report: ASHRAE Research Project 1036, Develop Simplified Methodology to Determine Heat Transfer Design Impacts Associated with Common Installation Alternatives for Radiant Conduit, here’s the link. Note the response times.
http://www.ngml.ksu.edu/research/project_archive/project_archive_publications/ashrae/1036_final_report.pdf

[situations and you'll find a fair number who are dissatisfied with the comfort. This is a good reason to keep a forced air system for heating as well as the radiant. Use the forced air for primary heating during mild weather]

Nope….dissatisfied with comfort is either poor design , poor design with poor controls, building flaws or all of the above. A competent designer considers all of these. Here in Calgary, where we get major swings in temperature, we use the ventilation system as a means of trimming the
loads…you don’t need a full forced air system.

I am very familiar with the EERE stuff … you’ll have to dig a lot deeper to come to appreciate the knowledge, experience to properly apply radiant to any project.

"you’ll have to dig a lot deeper to come to appreciate the knowledge, experience to properly apply radiant to any project."

Exactly. As my primary warning to the OP stated: "This is not a trivial application and should be approached with a proper design or you will be disappointed with the performance."

"dissatisfied with comfort is either poor design , poor design with poor controls, building flaws or all of the above. A competent designer considers all of these."

Exactly. you have to design everything properly in order to get satisfactory performance. Very few HVAC contractors are qualified to do this correctly. The vast majority (maybe all) of the installations I've seen in my area are flawed. Implementation is where reality meets theory. When the OP gets quotes from local HVAC companies to do the install and one says $10k, another $15k and $30k, and they all appear to offer the same service, you know which one likely get the job. And then there will be yet another black eye for the radiant industry. Hopefully, through all these discussions, the OP, and others, will come to understand the value of a fully qualified installer and will be willing to pay to have the job done right, by a certified, experienced professional.

Aside from the technical stuff, there are also major cultural challenges to overcome.

The first cultural challenge is North Americans have this inherent belief that if it wasn’t invented here it hasn’t been invented. Early writings about heated earth go back well before 6000 B.C. in Asia with early floor heating system uncovered in Korea and China dating to c. 2500 B.C. - in other words - thousands of years before the Greeks and Romans (who usually get the credit). It influenced cultural norms like whether you took your footwear off (Koreans socialize on the heated floor so soiled footwear was not permitted)…and clothing….the Chinese wear a tighter garment because they tend to socialize above floors on raised heated surfaces…the Koreans a looser garment.

Regardless both the Roman Empire and Asian Dynasty’s adopted radiant heating as norm. The difference between Asia (Korea in particular) and Rome was when Rome died so did the use of floor heating but the Koreans have always used it - today well over 90% of Korean construction projects use some form of floor heating.

In Europe radiant didn’t make reappearance until the 18th century in greenhouses and later with the first patent for water based systems given to Prof. Barker in the U.K. in c. 1901. Americans think it was Frank Lloyd Write who invented radiant but it wasn’t…he was like the Romans…borrowed what others were doing and applied it to his projects.

So the first cultural lessons North Americans need to learn is stop trying to turn everything into a Popular Science experiment…radiant is one of the oldest forms of heating and it has been well established in Asia and Europe...they’ve already gone through h the pain so we don’t have to…unless of course you like pain.

The second cultural lesson has to do with what Americans believe to be an appropriate amount for HVAC systems. The building industry has done a fantastic job convinvcing consumers that a nominal 4% to 6% of the construction cost should be in the HVAC system. What they have failed to point out is that 4% to 6% is based on minimum standards – it buys you the bare bones…i.e. its like making sure you have seat belts to ensure your safety but it doesn’t mean that the car has to be efficient and comfortable…so 4% to 6% won’t buy you efficiency and it won’t meet the benchmark in healthy comfortable environments – because…wait for it….it-doesn’t-have-to. Americans need to learn that at 4% to 6% we are paying for downgrades and most people will never know the difference until they have lived in a home that is not based on how it looks but how it feels. It’s like discovering you’ve been riding a donkey thinking its normal when everyone else has been riding horses.

The third cultural difference is how consumers have been led to believe that healthcare and architecture (and under it, interior design and mechanical systems) are separate elements. There not – they are one in the same. Did you know that North America spends almost identical amount on respiratory health care as it does on HVAC systems?

Anyways one can see it’s a very fascinating topic and in scope beyond the format of an internet chat forum – just know that there is a growing number who strongly believe that if we spent more money on better indoor environments which includes interior design and HVAC systems we would spend less on healthcare….just a hunch.
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If readers wish to have literary references and information sources for any of the materials above let me know before the end of the week - after that its back to work.

However, I thought that the radiant heat designer (assuming I find a good one) would accommodate the design for the flooring surface, windows in the room and other variables -- by increasing tubing spacing and water temp needed for that particular room. And if we have separate thermostat controls for the rooms with special circumstances that the radiant heat would still be a really good option. We do plan to insulate as well/much as we can afford and build well -- 2x6, plug holes, etc...

Can I just have the system designed by Radiantec or something? Are they competent to design a system?

I am concerned about the Spring/Fall --taking a long time to heat up and all that stuff. What about that Warmboard product that is supposed to be so great? They adverstise less heat up time...

There are more manufactures of pipes, boiler and controls and radiant accessories than there are auto manufacturers –you’ll get (have got) paralysis through analysis and if you take responsibility of choosing one component over another - rest assured - you’ll be responsible for that choice - you have to ask yourself , "do I have the skills to make these choices?" Most don’t.

Our advice to consumers sit down with your fellow inhabitants and define what you expect from your environment – think about what you want to hear (or don’t want to hear like air blowing around, squeaky pipes, toilets flushing and draining etc…), smell (or don’t want to smell like mould, ozone, methane, staleness), and feel (or don’t want to feel like cold floors, drafts, hot/cold spots) (forget for the time being about what you want to see – it just screws up the decision making for really good environments) – then define what you want to consume for electricity and gas (not what you want to pay – but consume) – then hold the builder and sub trades accountable to your expectations – unless you are skilled designer – your expectations will be the only thing you are in control of (put them in writing)…it’s a process which has worked for some maybe it will work for you.

To find a good contractor:

In Canada: We strongly recommend using contractors who have passed college programs such as those by NAIT, BCIT and has also been certified by the Heating, Refrigeration, Air Conditioning Institute of Canada ( http://www.hrai.ca) and the Canadian Institute of Plumbing and Heating ( http://www.ciph.com) - contact these organizations for contractors in your area.

In the United States: We strongly recommend using designers and contractors who have been certified by the Radiant Panel Association (http://www.radiantpanelassociation.org) - contact these organizations for contractors in your area.

Additionally, if you can find contractors who have also been factory cross trained by leading companies like Uponor (www.uponor.ca and www.uponor-usa.com), you’ll have eliminated 80% of the bad apples.

Last but not least, call the manufacturer up and ask them who their local wholesalers/distributors are then call the distributor and rep and get recommendations from them…

If you find an individual who is industry certified and factory trained and recommended by the distribution chain – you’ll now be working with the top 5% of the industry best.

You would be well advised to ignore most of the information offered by your peers and settle for a local professional.

You will never receive a 'free' design from any competent professional: if they sell something over the Internet, they design to the product. 'Open' systems are out and should make anyone suspicious of the advocate.

Drop me a line and I will design the system or refer you to some one who is qualified and find a local contractor if necessary.

Your basic plan is sound and achievable.

Thanks for your offer of help. I will email you. Your website was very informative!

I used to live in Bloomington and Eden Prairie -- how is the snow up there? :)