Ceiling Radiant retrofit

GMcD

If you lay the pex tubing directly on the back of the drywall ceiling and then "mud-in" the pex tubing to the surface you will get much better conduction and won't have to run the radiant water temp as high compared to a "lay-on" application. Another alternative would be to glue down metal heat transfer plates to trap the tubing against the ceiling and insure best conductance to the ceiling surface. Then insulate the heck out of each rafter bay and lay some more on top of that. Check to make sure the headers and feeder pipes to the pex system are all well insulated as well.

Albany Chris

I have read Dan's radiant book and searched the wall, but haven't been able to find my answer. So to the wall I go!
I am planning to retrofit my house with radiant heat on the first floor using trays or staple up in the basement rafters. Then I was thinking about the second floor and wondered whether I could do the same thing in the attic floor...? Can I pull the insulation and set the tubing against the ceiling sheetrock, maybe in trays? Obviously insulating with a gap and reflective foil. Is this such an obvious solution that I don't see it mentioned? Or don't I see it mentioned because it is such a bad idea?

Would you folks recommend antifreeze? I live in ALbany NY, and have pretty reliable power.

Thanks so much for any input!

Chris

[Deleted User]

I saw a system once...

that was done by a plumber back in the 40's. He took 1/2" copper pipe 8" n center in the ceiling rafter bays, on top of the sheet rock, covered the pipes with heavy duty aluminum foil, then covered it with rock wool insulation and VIOLA, radiant ceilings. When I spoke to the homeowner (recently new) about the comfort level, she said it was the most comfortable home she'd lived in.

I say go for it. Forget about the air gap if you go conductive though.

ME

pitman9

This method is covered in the RPA's Radiant Basics manual

http://www.radiantpanelassociation.org/i4a/store/category.cfm?category_id=1#Product1

Albany Chris

Ordered the book

Thanks, ordered the book already.

hr

I've done

a wall from behind, but it had plywood under the sheetrock to screw to. I have also done an exposed ceiling in my home and a shop by attaching plates from below.

I would get some Radiant Engineering U fin, snap in copper tube in straight lengths, then lay it on the sheetrock. Use pex connectors on the ends so you don't have to solder against the 'rock.

Insulate as the others mentioned.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

jerry scharf_3

works for me



I have randiant engineering thin fin in three ceilings and one wall. I worked out a slightly different installation method. I cut some 2x3s and dadoed in a pair of slots to carry the tubing part of the thin fin. I stapled the thin fin onto the cross members to build a nice frame, then nailed the frame onto the studs so it was against the sheetrock. Since you have the ceilings in place, you would run the tubing into the thin fin before nailing it in place.

Like the others said, insulation will be a key. Skip the air space and reflective barrier. If you can use anything else, skip the fiberglass as well (can have convective currents form inside.) Make sure you insulate over the ceiling joists as well as between them. If it were me, I would go with XPS betwen the studs and rock wool rolled the opposite direction on top.

jerry

Albany Chris

Response to feedback so far

Thanks for the feedback so far.

Some of my thoughts - I definitely want to use PEX instead of copper so that it hopefully won't burst if it freezes. And lets face it, over a 50 year life, we will have a multiday power outage someday. Any thoughts as to whether trays would make the PEX more likey to burst since it limits it's ability to expand due to the tight fit in the notch of the tray?

Some good feedback on insulation, I will definitely cover the joists - though the real risk will be at the soffit vents. I will have to pay close attention to those when I get up there.

Why isn't this done more often? Seems like a relatively easy way to convert a second floor from scorched air to hydronic. In my house I would say it is easier than retrofitting baseboards.

Unknown

You should be using PEX-AL-PEX to limit expansion, and extruded plates in ceilings are overkill.. I would save some bucks and use lightweight plates. If you do drop the money on the extruded plates though, then regular PEX is ok as the plate hold tightly enough to limit expansion.

Burst resistance is nice, but if you are worried about long power outages, you need to either put in a backup generator, or use antifreeze anyway. PEX is burst *resistant*, not immune.

We use radiant ceiling a lot instead of baseboard hybrid systems. Sure is nice not having a high temp demand on the system. But too many people get stuck at "wait, heat rises, right?" and never look into it further.

Gordy

Wow !

Do they miss out!

Tom_35

straight copper lengths and pex ends??

Hot Rod,

What is the reason for using the copper for the straight runs in lieu of pex? We certainly don't have the experience you have with this and that is the reason for the question.

From a simple mind, I can see that there are numerous chances for future problems with this---mechanical joints in the ceiling, more cost with the copper/pex fittings, more labor, copper more likely to freeze than pex.

Again, not doubting what you say...just need your further input.

Thanks,

Tom Atchley

[Deleted User]

Good question....

Why DON'T more people do ceilings than floors...

Lord knows, IU've tried to promote it, but get that "heat rises", or "doesn't your head get hot and your legs get cold?" blank stare. I assure them that a pproperly controled system would keep them 98% as comfortable as a radiant floor system, but other than myself, have had no takers.

I've often said that the two biggest overlooked retrofit potentials for existing houses is ceilings and walls. Easy to refrofit too. No trip hazzards, freedom of floor finishes, no output deductions for unheated floor space under cabinets, and so on and so forth.

Maybe, if we DEMAND that our customers use rad ceilings, they will. Another advantage to doing tube in ceilings is that you can get some cooling from them too. Just have to be cognizant of the dew point and know how best to control the production of condensation.

I think you will see more trends towards it once a few companies introduce thier cooling controls packages.

It makes perfect sense.

I've had some older homes with the radiant ceiling, and the owner thought they had radiant floors. Didn't figure it out until they went to install a new skylight in the master bedroom, and found pipes, lots of little ones in the ceiling plaster... "Jeeze, and I thought I had radiant floors..."

The comfort level is just a great. Remember, we're "adjusting" the MRT to the needs of the occupants, based on real time needs.


Like Gordy says, "They don't know what they're missing"

ME

hr

Hi Tom

this was an experimental system My goal was to turn that whole exposed ceiling into a big panel radiator. It had 12" of blown insulation on top and I did not want to disturb that. Hense the below ceiling application.

If you want to see some INSTANT heat response, try copper in ThermoFin. Being copper is an excellent conductor, vs pex as an excellent insulator, the heat transfer difference and responce is incrediable.

I agree, I would not want to bury that many fittings in a covered application. The PAP loop ends allowed expansion and allowed me to prefaball the copper in fin on the floor. I did this whole install working alone, so logestics were important.

Stick some copper in heat transfer plates when you have time to play. You will be amazed at the difference

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"