Radient floor Pex under plywood ..insulation thoughts?

Tore out a bunch of pink fiberglass insulation from my basement ceiling to access the tubing. What insulation do most folks use in this type of application? Would prefer to use something that won't get wrecked if that zone leaks somewhere. Thanks Ron

For that type of radiant I have always seen it insulated with fiberglass bats. Rockwool would handle a leak better, but is more expensive. If the whole job is already insulated with fiberglass I would stick with that.

We tore my brothers out when he had to replace the tubing and when we put it back up it was Blue styrofoam. Fiberglass sucks. For many reasons.

When I was plumbing we always used foil.... sometimes foil faced fiberglass, other times foil bubble wrap alone, or bubble wrap under some other insulation. The foil must be a minimum of 2" below the tubing.

The foil faced bubble wrap works good until it gets dusty on top.

I used precut reflective bubble wrap to insulate the floor joists. While when it gets dusty it reduces the radiant reflectance, it still makes a captured convection to be trapped in the joist cavity and directed at the floor above rather than the basement , which still obtains some of the leaking heat which for us is fine as by coincidence everything balances out quite well a two space for one installation idea. I also have a drop acoustical tile ceiling which capture more heat. Dont put your wi fi router up there as i did as it gets too hot for it , in my opinion

I am installing radiant pex in my house next spring, then finishing the downstairs ceiling with white tin, was thinking of just using the cheap foil faced stuff… thoughts?

The placement and type of insulation depends upon whether or aluminum transfer plates are used. I used Uponor plates which are heavier extruded plates (they are not cheap) which are first screwed to the underside of the floor and afterwards the pex is pushed/pounded in with a rubber mallet. Uponor specifically states that fiberglass insulation should be placed directly against the plates and tight to the floor. I have the radiant system under wood look ceramic tile on a ditra mat throughout the house except for the bedrooms where I have copper fin baseboard. The radiant zone consists of 9 loops of 1/2" pex none being longer than 275 feet. I have R 30 unfaced fiberglass in my 2x10 floor joists and 1/2" polyiso foam board on the bottom of the joists in the basement. ***It is critical to insulation properly against the rim joists as heat goes to cold and will migrate outwards. I cut 1 1/2" polystrene foam and place it in the joist bays against the rim joists. I have an EFM 520DF with primary/secondary piping and am heating my 2100 square foot rancher burning no more than 5 tons YEAR ROUND------including our domestic hot water. Finally, once you have radiant you won't want any other type of system although cast iron baseboard is also excellent----I actually have a 2 foot section of Burnham cast iron BB behind my toilets as part of the radiant loops in our bathrooms as you can't place the pex too close to the wax seals. Feel free to pm me with any questions and I want to wish you and everyone on this great forum a Merry Christmas and a happy, healthy, and safe new year.

This is what I plan on using, I have fully insulated rim joist with 2” foam board spray foamed in already.

KLook wrote: ↑

Fri. Dec. 17, 2021 7:00 pm

We tore my brothers out when he had to replace the tubing and when we put it back up it was Blue styrofoam. Fiberglass sucks. For many reasons.

what kind of tubing was it that required removal?

It was the Goodyear rubber hose that had a class action lawsuit filed and won. Sure was easy to put in with a staple gun but it became hard and brittle and sprung many leaks. Luckily? for him, it was a crawlspace not a finished basement under it.

KLook wrote: ↑

Fri. Dec. 24, 2021 9:04 am

It was the Goodyear rubber hose that had a class action lawsuit filed and won. Sure was easy to put in with a staple gun but it became hard and brittle and sprung many leaks. Luckily? for him, it was a crawlspace not a finished basement under it.

My grandfather has something extremely similar in his house that is just stapled in with like fence staples.. same stuff?

Yes, it should be replaced. It is just a matter of time.

Goodyear made it and it was called Entran II and there was an Entran 3 and a lawsuit.