You are here:

Radiant Floor Heating/1950s House with Radiant Ceiling & possible floor?


QUESTION: Hello Morgan -
We're hoping you can offer some suggestions/expertise!  We recently purchased a home in michigan that was built in 1950. It's a large ranch on a slab.  We'd like to understand if an old abandoned radiant system in the ceiling (and perhaps in floor?) might be worth further investigation and if it's worth looking into.

After cleaning out all the insulation in the attic, we discovered a beautiful radiant network in the ceiling, looks very well done and in immaculate condition but was "abandoned" at some point when previous owners put in baseboard (not the original owners).  The baseboard was done very poorly (in the 1980s or 90s) using orange flex line (Entran 3) vs copper for all the drops from the main located in the ceiling.  We also discovered valves in removable panels located in several closets that seem abandoned. The copper pipes come from the ceiling down the walls into their valve then into the floor. We really don't know what happens when the copper pipes enter the floor (some closets have 1 pipe, others 2 and I think one closet with 3 pipes and one of the 3 going into the floor is a bigger diameter maybe 3/4 vs 1/2) - could this be a radiant flooring system too?

1. Any guess or idea what the abandoned valves in the closets with pipes going into slab control? Could it be leading to an abandoned radiant floor system or Is there a way to determine what the valves/pipes do once they enter the slab?
2. Any good tests or locators to determine location of pipes in slab and ceiling network along with integrity to see if there are any cracks/leaks or worth restoring?
3. After cleaning out the attic insulation, we put in a hot roof foam system for a "conditioned" attic...the abandoned radiant system in attic is now easily accessible and visible - would it be worth pursuing further for restoration - is it efficient? Are there questions/experts you would recommend with knowledge to help determine condition and most economical approach?
4. Our boiler for the "new" (1980s?) baseboard we believe is 300 btu...we were told it needed a good cleaning and maybe replacement...potential options:
a.) Buy new boiler and keep entran 3 hoses (but baseboards look to be in rough shape - may need to buy new covers...any suggestions?)
b.) Buy new boiler and replace entran 3 hoses
c.) put in "split" forced air system in conditioned attic space which would also provide AC
d.) Try to continue to investigate abandoned ceiling (and maybe floor?) radiant system and possibly restore...would it be difficult/costly?  Best approach?
e.) We really don't like the baseboards...ideally we would like to go either forced air or restore the original ceiling (and floor?) system but would like to know what would be most efficient and provide best comfort in long run.

I could supply photos if it would help.
thank you in advance for any thoughts/suggestions!

ANSWER: Hello Tony,

You have described a radiant ceiling system made "popular" just after WWII.

A plumber set up a Jig (table) below the ceiling to be "radiated" and meticulously formed a radiant panel using soft copper tubing fixing the finished serpentine panel to the ceiling joists and typically ran the "tails" down to the boiler through an inside wall.

The plasters, in the days before drywall, would then nail wire and plaster the ceiling as normal.

The plumbers knew then, as we do now, that the finished panel should be served with water temperatures no higher than 120F to keep the cement-lime plaster from calcifying under extreme temperatures. I have seen some evidence of this as well as streaking typically following copper tubing as it fans out across the ceiling. This is almost always the result of someone tinkering with the mixing valve requisite and present in all the systems I have consulted on.

If the supply water temperature is carefully controlled with mixing or straight outdoor reset available on all condensing boiler made today, these old radiant ceiling will last another 70 years or so.

I would like to address comfort and efficiency while we are on the subject. As you related it is not readily apparent where all those pipes go. I myself was recently confused while in a neighborhood here in the Minneapolis area (Richfield, MN) where a young couple called to see if I could help with heating their cold basement.

They told me they had radiant floors on the main level and my handy infrared thermometer did in fact confirm that the floors and the ceiling were 72F with the thermostat set to 70. This affirmed my experience with radiant floors in general and I was not made aware until further inquiries, and careful examination revealed the truth. The ceiling were in fact radiated and the comfort unparalleled.

I recommend salvaging these old plaster ceiling radiant systems whenever possible since you will not have any more comfortable heat nor be able to preserve the original floor covering without fear of output limiting water temperatures (a radiant ceiling will likely have the potential for 3-times the output of the equivalent radiant floor even with the limiting factor of calcification).

Unlike their radiant slab cousins, (see Levit Town radiant, Frank Lloyd Wright radiant), radiant ceiling seem last even longer than the typical 50 years seen in the old copper or steel embedded concrete floors.

As for efficiency; if properly set up with outdoor reset and appropriate back insulation there is hardly anything as efficient as a hydronic radiant ceiling driven by a condensing boiler or heat pump.

As I have stated before, the only folks who live with baseboard are those that can't afford to be truly comfortable and those that have forced air heating.

As with every properly designed heating system, new or retrofit, it all starts with an ACCA Manual 'J' heat load performed on radiant dedicated software. In your case a rarely found radiant ceiling design module is a must.

---------- FOLLOW-UP ----------

copper going into slab
copper going into slab  

close up of pipes leading to slab
close up of pipes lead  
QUESTION: Hi Morgan - thanks for the quick reply and time! So if I understand correctly, you would definitely recommend restoring the ceiling radiant (we thought it was sorta strange since heat rises and wondered how well the room below would actually heat)... Do you suspect that we have radiant heated floors also?  (Would they have not done the ceiling without doing the floors?) I've attached a couple pictures of the pipes leading into the flooring. Could you please let us know your thoughts on if this looks like we would most likely have pipes in our slab too?    

thanks again, really appreciate your expertise!

Badger Radiant Ceilings
Badger Radiant Ceiling  
I recommend testing with air pressure all old hydronic radiant heating systems to 30 psi for 24 hrs. If the test is good, or the leaks repaired and retested with positive results, a hydronic radiant ceiling system will likely last many decades longer. We use the Fernox Power Flush method on all of our hydronic heating systems, new and old. This assures the inside heat transfer areas are transfer heat efficiently and lowers the risk of the heat transfer fluid attacking the copper pipe or other system components.

Water chemistry for a new boiler, manifold actuators and pumps has to be right if reliability, longevity and experience are important to you.

If the radiant ceiling is functional, or even portions thereof, we can model the working areas and determine with some accuracy the expected output, ergo comfort, of the radiant ceiling after renovation.

It is unlikely that the floor is radiated since the potential output of a radiant ceiling is more than double that of a radiant floor.

Though I am too young to have pictures of the original radiant ceilings I have attached a picture of a recent remodel in which we used new panels; also an option in your situation should you find your current system unserviceable.  

Radiant Floor Heating

All Answers

Answers by Expert:

Ask Experts


Morgan M. Audetat


Radiant panel heating design, including floors and ceilings, European wall panels and snow melting for residential and light commercial buildings..............................................................-Master of Steam and Hot Water,City of Minneapolis....................................................--- Master Plumber, State of Minnesota...........


30 years..... Charter Board Member - Radiant Panel Association, former manufacturer of condensing boilers, former national distributor of radiant floor products, son and apprentice of mechanical & plumbing contractor. Current mechanical/plumbing contractor specializing in hydronic based, integrated HVAC systems. Radiant floor heating/cooling. Snow Melting. Condensing Boilers. Indirect water heaters. System design, consulting and technical training world-wide. Licensed contractor, designer, installer and consultant.

B.S. University WI 1981 CONTINUING EDUCATION: Viessmann Condensing boiler and Solar water heating certification 2010, N.D.S.U. Lead Worker RRP certification 2010, Knight condensing boiler certification 2009, Wrightsoft Manual J CAD certification 2009, RPA Designer & Installer Certification 2008, Nate Hydronic/Forced Air Certification 2008, Uponor/Wirsbo advanced design school certification 2007, Buderus Wall-hung certification 2007, Power Limited License (low voltage controls) 40 CE credits 2005, Basic Hydronic Certification IPEX & Northern Alberta Institute of Technology 1998, Charter Board Member - Radiant Panel Association 1994, Residential Off-Electric to Hydronic Conversion Heating School Canadian Hydronics Council 1994, B&G Little Red School House 1993, Rood Utilities (now Auburn Technical Institute) Oil Burner School 1993 ,Tekmar Controls residential and commercial 1993, Division Manager and Advanced Hydronic Seminar Instructor for the first Exclusively Hydronic Radiant Floor Distributor in the USA 1990, Hydronic Radiant Heating Association Workshop participant with Richard c. Bourne, PE spring 1988, Master Plumbing, Hydronic, Solar Course Red Rocks Community College 1987.

Awards and Honors
2009 System Showcase Award - Radiant Panel Association

©2017 All rights reserved.