Radiant heat uses, designs, options:

Here Steven Bliss explains how to use radiant heat most comfortably, citing the ability to heat large areas to relatively low temperatures (rather than providing concentrated heat source), the evenness of radiant heat, and the importance of mass inside the structure to help keep temperatures even and comfortable through the thermostat cycling on and off where radiant heating systems are installed.

Steve describes relatively low-cost in-floor radiant heating systems using hot water as well as electric heating elements. In-drywall radiant heat products are also explained and described for ceiling use.

Our page top photo illustrates the heating boiler, circulators & mixing controls for a multi-zone radiant floor heating system installed during reconstruction of a home in Tivoli, NY.

Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.

Radiant Heat Use in buildings: when, why, how to use radiant heating

This article discusses the basics of radiant heat for auxiliary heating or basic heating in buildings, including strategies for using radiant heat.

The article also compares the costs of types of heating system use and we describe hydronic (hot water) radiant heat and electric radiant heat systems.

We describe typical installations of both hydronic tubing and electric radiant heat, including thin film electric radiant heat panels below several types of finish flooring.

Our photo above shows a radiant-heated concrete slab under construction in Two Harbors, MN in 2007.

• ADVANTAGES of RADIANT HEAT SYSTEMS
• DISADVANTAGES of RADIANT HEAT SYSTEMS
• FLOOR DAMAGE by RADIANT HEATING SYSTEMS
• RADIANT HEAT SYSTEM COSTS
• THIN FILM RADIANT HEATING SYSTEMS for Ceilings & Floors
• RADIANT HEAT PANEL & SYSTEM MANUFACTURERS

...

Advantages of radiant heating systems

• The radiant heating system is unobtrusive
  
  in fact not visible in the occupied space, saving floor space as well
• Radiant heating systems are quiet and clean
  
   and require little or no maintenance (depending on the heating source: an oil fired heating boiler supplying a radiant heated building will still require annual maintenance).
• Radiant heating systems save energy 
  
  compared with comparable convective heating systems where the same fuel is being used to produce btu's of heat. Savings accrue from lower air temperatures as well as the omission of duct or pipe heat losses in the system.
• Heating savings from radiant heat systems depends
  
   largely on the amount of thermostat set-back that the occupants find comfortable. Occupants of a radiant-heated building often are equally comfortable (compared with other heating methods) setting back the thermostat 5 degF - about a 20 to 25% savings on heating fuel expense.
• Radiant heat "feels special" 
  
  or "like being heated by the sun" - (an OPINION difficult to verify objectively).

   

...

Disadvantages of electric radiant heat systems

The radiant heat floor system boiler illustrated above was ultimately removed as the system was unable to heat the building were it was installed. Bad mistakes by the contractor meant that the radiant floor heating system was not usable and had to be abandoned.

• Extra ceiling or under-slab insulation

• Electricity can be the most expensive way to provide heat
  
   in some areas of the country. Check with your local utility company as special rates may be available for homes using electric heat.
  
  One of the many foul-ups of the contractor whose radiant heat system was described
  
  at RADIANT HEAT FLOOR MISTAKES was that he failed to install a separate electric meter to provide service to the building where the electric radiant heat system was installed (although the meter was included in the job specs ignored by the contractor), precluding the owners' ability to take advantage of lower electrical utility rates.
  
  The worst foul-up of the contractor whose radiant heat system was described in that article was that he buried the in-floor radiant tubing so deep in the floor slab that more heat was transmitted through the under-slab insulation than reached the occupied space - rendering the heating system not usable.
  
  Don't make this mistake.
  
  See SLAB INSULATION, RADIANT / PASSIVE SOLAR for under-slab and slab perimeter insulation specifications.

...

Floor Damage, Gaps, & Odor Complaints with Radiant Heat Installed under Wood Floors

We (DJF) have investigated a number of complaints of gaps opening between the boards of finished wood flooring and complaints of odors emitted from some types of tubing used in radiant floor heating systems.

Diagnosing gaps in finished wood flooring can be tricky, since these may appear with or without under-floor radiant heating systems installed, especially if the flooring is installed too quickly, without having adjusted its moisture level to that of the building. Installing wood flooring that is at too high a moisture level risks shrinkage and floor gaps as the building dries out.

In some cases that we investigated, flooring gaps appeared after an installer or owner pushed the radiant floor heating system to a temperature higher than recommended by the equipment and tubing manufacturers.

The temperature push was made in an attempt to "cook out" odors emitted from the radiant floor tubing when the heating system was first fired up.

...

Typical Cost of Radiant Heating Systems

The table above provides a typical fuel cost comparison for space heating.

Heating system costs are divided into installation or "first" costs, regular maintenance costs, and operating costs. Our photograph (left) shows two Therma-Ray electric radiant heat panels being installed in the ceiling of a 1960's home in Poughkeepsie, New York.

These panels were replacing previously damaged ceiling components. Be careful about cutting holes in drywall ceilings where electric radiant heating panels have been installed.

• The installation cost for most radiant heating systems is between electric baseboard and conventional air or hydronic (hot water) heating systems.
• Electrical radiant heating systems, if that's how your radiant heating system works, requires the least maintenance - practically none.
• The fuel costs, if your radiant heat system uses electricity, will be higher than oil or gas in most areas of the country.

...

Thin Film Radiant Heating Systems for Ceilings & Floors - types, where to buy

An alternative to hydronic, tubing-based radiant heating systems that were discussed above, at TYPICAL COST of Radiant Heating Systems we cited electrical radiant heating systems including panels used in ceilings or floors. [See our photo above for an older version of electric heat in gypsum ceiling panels.]

These electric radiant floor heating systems use comparatively thin flexible heating film panels (IHS-CPF) that are wired to a dedicated electrical circuit and of course controlled by a room thermostat. Some radiant heat panel sources include:

• Calorique (West Wareham, MA 800 922-9276), produces thin film radiant heating panel systems used for interior building heating (ceilings or floors), snow melting, de-icing, drum and tank heating, agricultural uses, pet heating systems, and consumer end products.
• (866-786-1806) radiant heating floor panels, .45mm thick, claim to be the thinnest radiant heating panels currently available. CarbonicHeat radiant heating panels are intended for use under ceramic tile.
  
  Radiant heat floor system products are also available for use under Saltillo tile and natural stone flooring as well as below nail-down (or staple-down) wood flooring and engineered wood flooring products.
• ComfortTile adhesive-backed fiberglass mesh mats for radiant floor heating [manufacturer and distributor contact information needed - CONTACT us], used under ceramic tile or stone flooring.
• FloorHeat (Lansing MI, 888-265-5455) provides electric radiant heating mats ideal for small floor areas, 12-inch wide electric heating elements for under framed floors, as well as supporting plastic grid modules, heating plates, and PEX tubing for hydronic radiant heating system s. Systems are intended for use under carpeting, hardwood, laminate floors, or parquet flooring.
  
  FloorHeat produces low-voltage radiant heating panels that might fit certain low-voltage alternative energy-designed homes. These panels can also be used in roofing applications and can tolerate being penetrated by roofing nails.
• IdealHeat - see WarmRibbon flexible heating film ribbons and panels described below. [manufacturer and distributor contact information needed - CONTACT us],
• In-Slab radiant heat electric cable used in concrete slabs. [manufacturer and distributor contact information needed - CONTACT us],
• Nuheat electric radiant heat systems ( Richmond BC, Canada, 800-778-WARM (9276) ) for use under tile, stone, and laminate flooring, Nuheat Industries provides a cable system that permits custom layouts of heating elements as well as both standard and custom heating mats.
• ThermalMat electric radiant heat panels used under hardwoods, laminates, and engineered wood flooring; [manufacturer and distributor contact information needed - CONTACT us],
• Warm Ribbon Flexible Heating Film panels [manufacturer and distributor contact information needed - CONTACT us], very thin panels, used under a variety of finish floor products. WarmRibbon products include a crystalline ribbon heater that can be used both indoors and outdoors and is intended for carpeted or parquet-flooring finish floors.

Note on Avoiding or Insulating Heat Sources rather than Producing Heat:

Too many of the electric radiant heat flooring searches we made turned up advertising pages where writers collected sources a bit hastily. We include the content below to help readers sort out the products they want (radiant heat flooring materials) from other stuff.

HeatShield panels, (Valley Center, CA 800-750-3978 ) produces heat insulating panels - in case you need to shield from heat rather than to direct heat into a building area. Heatshield Radiant Heat Mats (Amazon.com) are sold in an adhesive-backed form used, for example, in the automotive industry.

Examples of Thin Film Radiant Heat Flooring Installations for Different Flooring Materials

The Calorique company provides radiant floor heating systems in several designs including specifically for use below laminate flooring, carpeting, vinyl tile, linoleum, and ceramic tile floors. Calorique's system uses individual thin film panels connected to a 30-A electrical circuit to provide heat below these types of floor materials. Calorique describes these radiant heat floor installation examples:

Radiant Heat below glued carpet, wood, vinyl, or linoleum floors in dry surroundings

• Finished floor surface: carpeting, wood, vinyl or linoleum (sheet flooring) with adhesive
• Self leveling flooring cement or latex compound at least 1/4"thick
• Thin film heating mats, electrical, wired per the manufacturer's instructions
• Floor surface: concrete slab or wood

Radiant Floor heat below floating type wood, laminate, or parquet flooring in dry surroundings

• Wood, laminate, or parquet finish flooring without use of an adhesive (typically mechanical clips or fasteners)
• Thin film heating mats, electrical, wired per the manufacturer's instructions
• Soft insulation material (see the manufacturer's specifications)
• Floor surface: concrete slab or wood

Radiant Floor heat below ceramic tiles in dry surroundings

• Ceramic tile finished floor surface
• Thin-set / grout / tile adhesive or mastic
• Thin film heating mats, electrical, wired per the manufacturer's instructions
• Hard insulating material (see the manufacturer's specifications)
• Floor surface: concrete slab or wood

Radiant Floor heat under tiles in wet surroundings

• Ceramic tile finished floor surface
• Thin-set / grout / tile adhesive or mastic
• Grounding net - recommended in wet surroundings, a grounding net (for safety) is installed directly above the heating mat
• Thin film heating mats, electrical, wired per the manufacturer's instructions
• Hard insulating material (see the manufacturer's specifications)
• Floor surface: concrete slab or woo

- Thanks to reader Jim O'Dowd for suggesting this resource.

...

Current manufacturers of radiant heat ceiling and other radiant heating panels include

Photo below: radiant heat being installed in a building ceiling using pre-fabricated THERMA-RAY electric radiant heat panels.

• Calorique Radiant Heating Floor & Ceiling Systems, Calorique LLC, 2380 Cranberry Highway, West Wareham, MA 02576 USA, Tel: 800 922-9276, produces thin film radiant heating panel systems used for interior building heating (ceilings or floors), snow melting, de-icing, drum and tank heaitng, agricultural uses, pet heating systems, and consumer end products. The company provides radiant floor heating systems in several designs including specifically for use below laminate flooring, carpeting, and tile floors. - Thanks to reader Jim O'Dowd for suggesting this resource.
• Danfoss Radiant heating panels (rolled) - sold ghrough Grainger, Supplyhouse.com and other supopliers
• Dayton Radiant Electric Ceiling Panels - sold through Grainger.com and other suppliers, these are recessed or surface-mounted individual heater panels
• Envi 220v Electric hardwired radiant heating
• FloorHeat 3130 Sovereign Drive, Lansing, MI 48911, 888-265-5455, Email: info@FloorHeatCompany.com) radiant floor heating panels
• Heatshield Panels, 27354 Valley Center Road, Valley Center, California 92082 USA, 800-750-3978
• Herschel Infrared Heat Panels - UK Company
• LuxHeat radiatn floor heating mat systems
• Nuheat Industries, 3105 - 6900 Graybar Road, Richmond, BC Canada V6W 0A5, electric radiant heat systems for use under tile, stone, and laminate flooring, Web: nuheat.com Tel: 800-778-WARM (9276) Email: info@nuheat.com
• Qmark Electric Ceiling Panels - sold through Grainger.com and other suppliers,
• QuietWarmth electric under-floor heating panels
• ThermoSoft electric radiant heat panels and ThermoFilm mats for electric in-floor heating
• Vevor Radiant Panels (floor panels)
• Warmboard Radiant Floor Heating Systems

 

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

...

Original article

Links to the original article in PDF form immediately below

• RADIANT HEAT USE Part 1 [PDF] - Radiant Heat: how it works and when to use it.
  
  use your browser's back button to return to this page
• RADIANT HEAT USE - part 2 [PDF]
• RADIANT HEAT USE - part 3 [PDF]

CONTACT us to suggest other types or suppliers of radiant heating systems and equipment.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles.

Radiant Heat Installation & Operation & Temperature Guides

These references, studies, guidelines on radiant heat temperatures, heat losses, etc. are now found

at RADIANT HEAT TEMPERATURES

 

Thank you to our readers for their generous comments

Radiant heat experience

I appreciate your site. This kind of discussion is very helpful. I have been struggling for over 3 years with an incompetently installed hydronic system.

My system pumps 180 degree water to concrete slap, under wood foors and radiant wall heaters on three floors in a 106 year old wood house. (Jan 7, 2013) john

...

Hello Mod and >>Thank You<< for the opportunity you've provide me and other readers to learn from your expertise!

I've been reading your site since you first started and remain amazed and thankful. On 2018-01-09 by Ar

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Experienced in-floor heating installer in the U.K. gives advice

I have been installing in-floor heating in the U.K. for over 25 years, and fixing poorly installed systems a few times a year.The most sucesfull way we found was a three stage process.

Stage 1. a concrete slab is poured leaving 4" from the eventual finnished surface.

Stage 2. 2" foil covered polystrene, laid on top foil side up, with an upstand at the edges. Mesh next, with 1/2"'Pex' oxygen barrier pipe tied to the mesh.

Stage 3. a 2"concrete screed.

The pipework is kept under pressure the whole time. On start up the temperature is kept low and increased daily until the design temperature is achieved.
The final floor covering is installed after 30 days.

This type of system is used in homes ,schools,hospitals, senior's homes. It was also used in London's British musuem, North American building where is is linked to hot and chilled water system's to keep exhibits a constant temperature.

One of the reason's it is used so much here is that health and safety is requiring radiators to be boxed in to prevent burns to the young and the elderly.
If I had the choice it would be in floor heating in my house every time.
Stay warm (Jan 6, 2013) Tony 

 

Radiant heat flooring & snow melting installer in Minneapolis comments on why contractors put the tubing too deep

We design and install radiant floor and snow melting systems here in Minneapolis. Good people are out there, but you have to ask the right questions. There is simply no substitute for experience and design software. If your contractor can't produce a sample heat load, and pictures of similar installations, you need a new contractor.

As for tubing depth in a 4" slab. Much has been made of this interesting 'model', most especially by self-professed experts following John Siegenthaler's (my personal Hydronic Hero)interesting study. Unfortunately, this is a pour example of real hydronic radiant slab-on-ground installation as is this the this story of tubing installed in an un-insulated footer.

This is not your slab or anybody's for that matter. Few put floor covering over new slab-on-ground radiant floors but those who do would likely not need 35 btu/sq ft. unless the they live here in Minnesota and left the windows open in January.

The first number then at 15 btuh/sq.ft. would be reasonable and then only only under "design" conditions, less than 2% of the heating season here in Minnesota. The rest of the season it simply doesn't matter. First, 2" of XPS is the current under-slab insulation of choice in most cold climates as it stands up to foot traffic and also meets the accepted standard of 5 times the heat flux to ground.

Second, the design water temperatures and tube spacing are completely arbitrary.

The insulation below the slab has everything to do with the year round ground temperature, the indoor, outdoor design temperature, the design water temperature and the heat loads dictated by building construction and climate. Response time is also factored in and of little consequence when weather sensitive controls are employed.

Furthermore, Ziggy uses 12" O.C. spacing, which is common but by no means certain.

If he used 8" O.C. the response time would be decreased along with the average water temperature, downward heat flux and consequent cost of this current standard.

The reason PEX tubing is placed at the bottom of nearly every residential and light commercial slab in the country is simple.

It is much harder (more expensive) and dangerous (easy to hit with a saw or fastener) to raise by pulling or set PEX on chairs. Folks in South Dakota bury their PEX to "charge" theirs slabs with cheap off-peak electricity (Mar 15, 2014) Morgan Audetat 

Reply:

Thanks Morgan, I agree;

The horrible radiant heat intallation we describe was in fact in a Minnesota home.

But let's keep in mind that a significant number of homeowners in Minnesota do not live near a large city where experts are available, and at least some contractors in MN make the same mistake as that of contractors all over the world, being unable to recognize the limits of their own ability and expertise.

The SNAFU contractor did beautiful carpentry work but was frankly both incompetent and a bit of a bully when it came to other areas outside his expertise. The customer doesn't even understand that more expertise is needed - until too late.

 

Radiant heat design in Canada - Will high radiant heat tubing weaken the strength of my floor slab?

I am planning to build a garage with floor heating and this article really guides me well. What of the streght of the slab surface when tubing is only 2 inches or less from this surface?

Would it weaken the structure? Ex: vehicle garage, tooling etc.. (Jan 7, 2013) Patrick Morin of Qc Canada

Reply:

A reinforced concrete slab or fibre reinforced slab with radiant heat tubing 2" from the slab surface has not been a source of reported structural issues that we've heard. Here is some research that's related.

• Al-Homoud, Dr, and S. Mohammad. "Performance characteristics and practical applications of common building thermal insulation materials." Building and environment 40, no. 3 (2005): 353-366.
• Behnood, Ali, and Masoud Ghandehari. "Comparison of compressive and splitting tensile strength of high-strength concrete with and without polypropylene fibers heated to high temperatures." Fire Safety Journal 44, no. 8 (2009): 1015-1022.
• Desoto, S., and L. A. Glenn. "An analog method for the solution of unsteady radiant heat-transfer problems with combined conduction and convection." Journal of Spacecraft and Rockets 3, no. 2 (1966): 224-230.
• Farid, M., and W. J. Kong. "Underfloor heating with latent heat storage." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 215, no. 5 (2001): 601-609.
• Han, Sang Heon, Daejun Chang, and Chang Young Kim. "A numerical analysis of slab heating characteristics in a walking beam type reheating furnace." International Journal of Heat and Mass Transfer 53, no. 19 (2010): 3855-3861.
• Mingqing, Sun, Mu Xinying, Wang Xiaoying, Hou Zuofu, and Li Zhuoqiu. "Experimental studies on the indoor electrical floor heating system with carbon black mortar slabs." Energy and Buildings 40, no. 6 (2008): 1094-1100.
• Sugiyama, S., M. Nishimura, and H. Watanabe. "Transient temperature response of composite slabs." International Journal of Heat and Mass Transfer 17, no. 8 (1974): 875-883.
• Yehia, Sherif, and Christopher Y. Tuan. "Conductive concrete overlay for bridge deck deicing." ACI Materials Journal 96, no. 3 (1999).
• Zhao, Hong-Ming, Song-Gen Wang, Zhi-Min Wu, and Guang-Jie Che. "Concrete slab installed with carbon fiber heating wire for bridge deck deicing." Journal of Transportation Engineering 136, no. 6 (2009): 500-509.

 

Radiant Heat Installation Details by a radiant heat contractor in Calgary, Canada

I have been a contractor for over 60 years and have had experience with in slab, on grade heating,n my ohouse which had a substantial walkout lower levelThis house was bult in
Calgary,Alberta, Canada and we can experience temperatures to the mid -30 degrees.

I have read your comments with much interest and agree with many of your recomendations however I think there are some hole in the procedures and while there is osme expense
entailed in implimenting them the pay back in savings is very short,I suspect 3-4 years.

My experience is thatthe foundation insulation on the exterior of the wall is the first line of defence in that it minimizes the thermal transfer through the foundation wall which then finds its way up to the wall plate on the exterior wall.

I also insulated the inteior of the foundation wall to prevent thermal transfer to the slab and the subsequent cooling effect on the lines closest to the wall.

I agree with the depths of the piping at 2" but anything less than that could reult in cracking in the upper portion of the slab.

An additional measure I incorporated was to cover the exterior insulation with heavy gauge poly to a depth of 6 feet and carried it out 6 feet from the foundation.

This had a dual purpose in that it kept the moisture away from the foundation but also eliminated moisture from the surrounding soil which mitigated the freezing of the soil snd the subsequent cooling effect under the slab area

We were in the house for 10 years and never had the thermostat set above 15 degrees celsius in that area and it kept the area quite liveable.

My water souce was a25 gal electric water heater with an expansion tank and an in line tranfer pump. in the 10 years of use I did not experience any isues that require attention.PS I am c urrently designing a siliar sys (Aug 23, 2012) Edward Wyatt

 

Electrical contractor reports on radiant heating system performance, insulation requirements

I have been in the electrical construction biz for over 30 years. Residential, commercial, and industrial. I do all my own HVAC work for myself, not for hire as I'm not certified. But, I have a very good working knowledge of how these systems opperate, and have installed the various electrics for so many HVAC systems in different types of buildings. Here in Southwestern PA, I have seen "in-floor" radiant heat installed many times.

It has been my experience that whether or not there is floor heat installed, the contractors I have whitnessed always installed 2" rigid foam insulation along the perimeter walls down to a depth of 4 feet, then the same insulation 4 feet in, towards the center of the building. Then, bar, mesh and chairs to hold the steel at a certain depth in the pour.

For radiant heat, the entire area is insulated with at least 2" foam. To me, this is a "no-brainer"!!!

If you have ever gone camping, and had to sleep on the ground, or floor of a tent without any insulation, then you should realize that you NEVER can get warmed up. Your body heat is conducted into the ground. I know first hand the level of incompetence some contractors have. I have gone rounds trying to explain things about my trade to "hard heads", the arrogant, bully mentality some so-called experts have.

Sad thing is that these people have the ability to convince the unexperienced owners that their way is the right way, and ultimately the owner gets screwed in the end.

Trying to re-coup their money, or part of it in court proceedings is usually a waste of time. If I see something is wrong at a job by another trade, I will bring it to the owners attention. I know that if I were the owner I would want to know. Hopefully as more states adopt building codes, and require inspections, this type of thing won't happen.

But people are always looking for a deal. Cheap is never any good, and, if you don't know something, then get a second opinion, or third, or fourth. When in doubt, STOP the construction till ALL your questions are answered. (May 3, 2012) marc stayduhar marcsayduhar@yahoo

 

High radiant floor slab heating bills due to deep tubing or wrong temperature setting?

My son installed his floor system, Pex in concrete, and lives in Arkansas. He has high heat bills and I told him to set his thermostat closer to the floor at 68-70 and leave it on starting in October. He has it placed up on the wall with the regular thermostat, heat pump, and leaves it set at 70. He also is away for several days at time and will shut down the system to "save electric" which I have told him not to do.

The house is 1600 sq ft in northern Arkansas and has insulated slab and was built with Styrofoam blocks filled with concrete, 12 inches thick. Cooling cost is minimal, but heating is in neighborhood of double or triple.

I have "harped", as parents do, to not turn it off, start it earlier, he sometimes waits till December, and move the thermostat to sense the warm floor and not the room temperature as the room will follow the floor temperature eventually.

Maybe not move the thermostat down, but lower the room temperature setting so you get the same effect, but am I right or wrong on other counts? (Apr 25, 2014) anonymous

Reply:

Anon,

Previously I agreed with you thinking that the cost to re-heat cold stuff pushed up the heating total cost but more recent studies argue the opposite.

I think some diagnostics might be helpful. If we knew more details about how the slab was built, how it was insulated from the earth, and how deep the tubing is in the slab we could form an opinion. If his builder, like mine, was a love when it came to radiant slab basics, then we might have to make some changes to obtain economical heat.

Why does the return temperature on our radiant heated floor vary so much?

The return water temperature on my floor heat varies 15 to 20 degrees.

The thermostat is calling for heat, so the circulator is running.

Is it possible that the circulator is slowing down sometimes?

When the return temp. is between 110 and 115 degrees enerything is great, but it drops to around 100 degrees and the rooms stay cool. On 2021-11-27 by William F McGinnes

by Inspectapedia Com Moderator - Causes of radiant heat floor temperature variation and supporting research

@William F McGinnes,

If there are multiple heating zones being served by one circulator, then the return temperature might indeed very depending on whether one or more than one zone valve is open.

Variations in the return temperature of the water in your radiant heat floor system, in my OPINION, most probably reflect variations in the heating load in the heated space. The heating load variations in turn would include at least things like

• The level of occupancy of rooms
• People opening or closing windows and doors
• Outdoor temperature - controlled by adding an outdoor temperature sensor to your system
• Solar gain

In addition, if the amount of radiant heat tubing or number of loops under your floors is a bit marginal, in cold weather you may find that the floors are not warm enough.

Also of course, the rate of heat loss from the occupied and heated spaces in your home will vary considerably as outdoor temperatures change. When it's colder outside the rate of heat loss increases.

Some useful research on your question is at

• RADIANT HEAT - topic home
• Olesen, Bjarne W. RADIANT FLOOR HEATING in THEORY and PRACTICE [PDF] ASHRAE journal 44, no. 7 (2002): 19-26. - local copy saved as Radiant-Floor-Heating-Olesen-ASHRAE.pdf
  
  Excerpts pertinent to your question:
  
  As shown in the previously mentioned studies and as demonstrated by Olesen,5 there are seldom problems with radiant asymmetry from cold windows in modern buildings. Using ANSI/ASHRAE Standard 55-1992, Thermal Environmental Conditions for Human Occupancy4 and the ASHRAE Handbook— Fundamentals,3 it is possible at the design stage to evaluate the risk for discomfort due to radiant temperature asymmetry.
  
  Downdraft from cold surfaces (windows) is another factor that may cause discomfort.
  
  The main thermal comfort problem, which may occur in wellinsulated buildings, is large variations in the room temperature due to changes in internal loads from occupants, lighting, equipment or direct sunlight.
  
  The low heat loss in well-insulated buildings means that changes in internal loads have a higher impact on the room temperature than in buildings with standard insulation.
  
  The influence depends on the thermal mass of the building and the controllability of the heating system.

 

Where do I find repair wire for electric radiant heat in a ceiling?

@InspectApedia Publisher, problem is that I can’t find the heat wire manufacturer. All I have is the picture of that wire & can’t seem to find any other info on it or if I need to solder or use a butt slice to reconnect wire. Any other info that you have would be appreciated. Thanks

I’m trying to find radiant heat wire that was used in ceilings I heard around the 1960’s. Single conductor with thick insulation. Looks like a size 22awg wire from a home in California. Looking for a replacement wire that I could use to splice into. It is stapled onto drywall then gets mudded to hide in ceiling.

Photo: UL listed electric wire for radiant heat system, identified as (UL) E-25612 90°C

This Q&A were posted originally

at OLD ELECTRICAL WIRING TYPES  On 2023-04-17 by Alex -

by InspectApedia Publisher (mod) - repair kit & instructions for fixing damaged electric radiant heat cables or wires

@Alex,

I was not sufficiently clear in my earlier answer suggesting that you're looking at a wire splice whose connections need to be approved & safe as well.

There are literally dozens of manufacturers of electric radiant heat wire manufacturers whose products can be installed in a ceiling or used to repair broken radiant heat wire in a ceiling.

I'll paste screen shots giving an example, simply searching for "electric radiant heat ceiling wire" and of radiant heat electric cable repair kits.

You'll want to contact the manufacturers directly to ask for advice about code-approved and electrical- and fire-safe connections when repairing such wiring.

The concern is that using typical electrical wire connectors may lead to a failure as wire used for radiant electric heating goes through so many temperature cycles and heating variations.

The good news is that electric radiant heat cable manufacturers also make wire or cable connection and repair kits.

For example, NuHeat offers a radiant heat cable repair kit and repair instructions.

I'll post a photo of the repair kit and a link to radiant electric heat repair instructions above.

 

Below: example of sources of electric wire cable used for electric radiant heat systems.

See these

• NUHEAT RADIANT ELECTRIC HEAT CABLE REPAIR KIT INSTRUCTIONS [PDF] NuHeat Corp., nVent Thermal Management, 3210 – 6900 Graybar Road, Richmond, BC, Canada V6W 0A5 Tel: 1-800-778-9276 (WARM) Web: www.nuheat.com/
  
  
• FYI see our articles on radiant heating starting at
  
  RADIANT HEAT - home

 

How Can We Find out if the Radiant Heat System is Usable in the Home We're Buying?

Situation: Currently in escrow on a home built in 1978. Home inspector only recommended further evaluation of the home's radiant heat.

A prior owner installed central A/C and heat. There is no known broiler, pump or any such device visible for the radiant heat, but there are analog knobs on the walls in each room to control it. Not sure if it is operable or safe.

Question: What is the method for determining:

A) Is it safe to operate?

B) Is it electric or hydronic?

C) If installed to a home on a raised foundation if it runs in the floors or the walls?

D) Is it still operating (functional)?

E) What type of professional would service or inspect this system? - On 2017-05-30 by Diana -

Reply by (mod) - How do we determine if electric radiant heat is working & safe to use?

Diana,

Sounds as if the home inspector took an easy way out. I would think he would have told you if there was a functional or not functional heating Source in the house.

Just saying evaluate further is a little vague.

It's possible that the heat is or was electric radiant floor heat but I really can't know from your text.

An inspector with a little bit of experience ought to be able to look at the controls and try turning them on to see if the floors get warm.

She can also use an IR scanner or similar tool to look for leaks in the radiant heat tubing (if it's hot water radiant heat) and to confirm the uniformity of heat across floor surfaces regardless of the heating source.

If the radiant heat is done by electrical cables those circuits should be clearly marked in the electrical panel or sub panel.

If the radiant heat is by a boiler, the inspection of the radiant heat boiler itself is not at all esoteric and should have been done b your home inspector. Now that he fell down on that job you'll have to hire a heating service contractor to inspector and report to you on the boiler condition.

Radiant heat was incorrectly installed, too hot, and my floors cracked.

I have radiant heating in my indoor concrete floor. I understand that my boiler system was installed incorrectly and water temperatures of 180 was running through the tubing ..

My concrete floor is severely cracked ... what is the maximum temp of water for the tubing and what concerns should I have with regard to damage to tubing ...life of tubing ...

Should it be replaced. Please let me know if there are any other concerns I might have
thank you for you time - On 2016-04-27 by Susan

Reply by (mod) - radiant heat "caused" cracks in concrete floor?

Sorry to hear this trouble, Susan, and surprised that radiant heat would cause the floor to crack. Perhaps you first want to get some help with diagnosing the cracking cause: is it in the pattern of the tubing or at stress points or is there foundation settlement, or slab heaving or something else?

About the tubing: take a look at the tubing where it is exposed to view.

Armed with the brand name and tubing model name we can look up the manufacturer's temperature rating. It may be that though 180 was too hot, the tubing may be un-damaged.

Post a photo so that we can see more of what's going on.

 

Do we need the auto or fan setting on the thermostat when using electric radiant heat

Can you tell me the proper FAN setting on my thermostat to make our radiant heat ceilings work properl?

Reply by (mod) - NO

Anon

Presuming your heating system is only providing heat the FAN setting should be irrelevant as it ought not be connected to anything.

I'd use AUTO or HEAT if there is a HEAT position.

See FAN ON AUTO MAN THERMOSTAT SWITCH for articles that include the thermostat settings.

Can I install poles to hold up a wall unit under radiant heated ceilings?

we have radiant heat- do I put it on auto or fan in the winter
Can I use poles to support a wall unit under radiant heat ceilings?

I just moved into a condo with radiant heat ceilings. I want to install 4(four) One inch (1") by one inch poles to support a wall unit system . The poles would be about 13 inches away from the walls and 32 inches apart.

Cabinets fit I between the poles and get bolted to the poles. The walls serve as support since the units are flush with the wall. The system was designed by the architect George Nelson and was sold in the 1970s by Omni.

Please advise as to the safety or danger to the heating ceiling.
Thank you - On 2014-10-29 by Aimee -

Reply by (mod) -

A friction-mounted pole that simplyis held in place by spring pressure won't harm the radiant heat ceiling systemn, but

Watch out: do not drill holes in the ceilings to install other supports before the exact location of the radiant heat ceiling panels and circuts have been mapped - the risk is that you cut a wire, break the heating system, or get shocked.

Why did our radiant heat ceiling system stop working in two rooms?

The
ceil heat has stopped working in two rooms of my house... also one of my light fixtures has stopped working also.

Could this be related to the heat not working? I have tested the wires and electricity is getting to the thermostat and the light fixture. What could be my problem? On 2014-03-16 by Anonymous -

Reply by (mod) - how to fix an electric ceiling heat system that stopped working

Anon:

If the ceiling heat in the rooms where you have not heat is on the same circuit and controlled by the same thermostat as in rooms where you do have heat then most likely the radiant circuit for those rooms has been damaged or interrupted. That can happen by someone driving a nail, walking in the attic, or more seriously, by overheating of the system.

But the fact that sonme lights are off too tells us

1. That there probably a circuit breaker that has tripped off: check your electrical panel for one or more tripped breakers

2. The ceiling heat system may be improperly wired, overloading one circuit by putting too many heating circuts PLUS light fixtures on one circuit

3. There could simply be a loose or broken connector in the circuit - your electrician will check circuit continuity and if needed, inspect the connections in each of the electrical wiring junction boxes in the circuit

No heat in radiant floors after we ran out of oil

We ran out of oil last friday and the oil company came and restarted the furnace. However we just realized that our rooms with the radiant heat flooring aren't working. What do I need to do? - On 2014-03-08 by Dana

Reply by (mod) - radiant heat working in some rooms, not others - check for air bound hot water lines

Dana,

If you have heat in some rooms but not others, the problem is not likely to be the oil burner itself.

However when a radiant floor heat is off for a time it's possible that a control seized or that a loop has become air-bound.

Ask for a service call to determine if a control is not working or if there is another heat problem with just that zone.

Details of diagnosing and fixing this problem are

at AIR-BOUND HEATING SYSTEMS

Keep us posted.

DF

How can I Assess the condition of electric radiant heated ceilings ?

Hi,

I am buying a condo with electric radiant heated ceilings. The property is currently bank owned so I don't know anything more about the heating than that (other than that each room is independently controlled). From my reading so far I am unclear on whether there are different kinds of electric radiant heat ceilings or if it's all pretty much the same.

I understand that I cannot puncture the ceiling in any way, but would pressure damage it as well? I would like to use a portable dance pole sometimes, which is basically a very big tension rod.

The top does have a 16" diameter dome to spread the pressure over a greater area, but it only contacts the ceiling at the edge where there is a ring of silicone. I worry that the wires might be damaged by being pressed between the pole and the joist, since there has to be enough pressure to withstand lateral forces on the pole.

Would it make a difference if I put it up only when I wanted to use it versus leaving it up most of the time? I was so excited to be moving someplace with enough room to have a pole of my own until I realized just how big of a deal it is to damage these heating systems. I would rather keep using the poles at the gym than cause thousands of dollars in damage to my home (and investment). - On 2012-05-07 by Katie -

--- and ---

1960 era All Electric Apartment needs details on heating method, condition, etc.

Just moved into an 1960 era "All Electric Apartment" in Southern California. Wondering

1) What type of Electric heating system my unit probably has

2) Is there a general guideline to caculate kWh usage and thus understand usage better (& potential problems)?

2) Any tips on How to save on heater usage?

a) Been told that best to turn heater breakers off when not using (myth or fact)?

3) Any maintenance that would help

a) Like Replace Manual Thermostats with modern LCD Timer Type?

b) Breakers?

I have a two bedroom apartment with 3 Separate Thermostats in all rooms. - On 2011-12-14 by Anon

Reply by (mod) - How to Evaluate Radiant Heat in an Older Building

1960-era all electric and Katie:

1. Type of heating: we cannot know what type of heat your all electric apartment has without more information: there may be (typical) electric baseboard heaters, or there may be radiant in floor or in ceiling, or less likely even an electric boiler powering hot water heat or water to air heat.

Take a look for heat radiating devices, take some sharp photos and send them to us (see the CONTACT link at top, left, bottom of our web pages) and I can comment further.

2. I'll research and reply to this later

3. The first and easiest thing you can do to save on heating cost with electric heating is to manually or automatically set back the temperature at night or when you are out of the apartment.

You may want to install automatic programmable thermostats so that you can set and forget the setbacks,

WATCH OUT: some electric heat systems use a high voltage thermostat that is wall-mounted or may be mounted right on an electric baseboard unit. If your apartment uses that type of heat control, the standard low-voltage programmable thermostat sold at building supply stores won't work.

You do not need to turn OFF a heater when it's not in use as long as the thermostat is keeping the heater off. Off is off, whether the "off" state is specified by the thermostat or by a circuit breaker. The only exception is a very small electricity usage to power thermostats themselves.

3. If your heaters use a finned system to heat air (take a look behind the covers of electric baseboards for example) gently vacuum off dust and trash that may be blocking airflow, and don't block the air entry points at the bottom of baseboard heaters by thick carpeting or anything else.

Take a look at our articles on electric heat, saving on heat energy, etc. beginning with the article titled "ELECTRIC HEAT" found near the top left of this page.

...

Continue reading at RADIANT HEAT AIR BOUND or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Radiant Heating System Articles

• RADIANT HEAT - home
  • CARPETING IMPACT on RADIANT HEAT FLOOR
  • DRIVEWAY & WALK DE-ICING SYSTEMS
  • RADIANT HEAT AIR BOUND
  • RADIANT HEAT CONTROLS
  • RADIANT HEAT DEFECTS LIST
  • RADIANT HEAT DESIGN & INSTALLATION MANUALS
  • RADIANT HEAT INSTALLATION - Dream Home Guide, 1950s
  • RADIANT HEAT MISTAKES
  • RADIANT HEAT TEMPERATURES
  • RADIANT HEAT TEMPERATURE CONTROL / MIXING VALVES
  • RADIANT HEAT TEMPERATURE NIGHT SETBACK
  • RADIANT SLAB FLOORING CHOICES
  • RADIANT SLAB TROUBLESHOOTING
  • RADIANT SLAB TUBING & FLUID CHOICES
  • RADIANT SLAB TUBING LEAKS
  • SLAB INSULATION, RADIANT / PASSIVE SOLAR
  • THIN FILM RADIANT HEATING SYSTEMS for Ceilings & Floors
  • WOOD FLOOR RADIANT HEAT
  • WOOD FLOOR RADIANT HEAT DAMAGE

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