HELP! Underfloor Radiant insulation methods

rwhtg

With underfloor radiant installed with aluminum plates what is the preferred insulation method? 3/4” advantec subfloor, tile floor membrane ( no cement backer board) mortar and tile entire radiant area.

Foil faced fiberglass with a 2-3” air gap? ( I’ve read foil faced isn’t really a benefit in this application nor is an air gap for convection. Seeing how we are mainly relying on the plates for conduction)

Unfaced fiberglass pushed up to subfloor?

No insulation?

* I’ve had foil faced R19 with air gap installed since spring of 2017. Viessmann CU3A, HF40, a fridge, and a dehumidifier are the only appliances in the basement. House is moderately weatherized. Basement temps have been 70 deg F or higher all four seasons.....noticeably higher temp when you open the door at the top of the stairs. House maintains 67-69 deg F

Recently uninsulated basement ceiling due to a mouse problem. Basement temps now 65-67 deg F......I would have expected they stayed the same or increased. House temp staying consistent, floor temps feel the same to bare/ stocking feet.

I’m considering NOT reinsulating the basement ceiling. Any thoughts would be greatly appreciated!

kcopp

What type of aluminum plates? Are they the extruded heavy duty plates? or the thin "beer can" plates? The heavy duty ones are the best option. What water temps are you running through the tubing? Did you get a lot of plates in there or are there gaps?
No insulation is not an option. Don't leave an air gap if they are the good plates. You are looking for conduction through the plates to the floor.

Dave H_2

You need to insulate. It may be OK now, but when the load gets higher (colder out) you end up with one system trying to heat two different spaces and the basement will win by being warmer than the first floor.

Foil faced ain't gonna get you much "reflection" of the radiant energy. For one, the foil must be high quality aluminum, super shiny and clean to reflect the radiant. Unfortunately when foil faced insulation is made, none of that is met.

No air gap if using the heavy extruded plates, you want conduction to heat the floor which then will heat the room.
Some of the thinner plates use the air gap to "supplement and even" the surface temps of the floor. Check with manufacturer on their recommendation.

Dave H.

rwhtg

Dave H_2 said:

You need to insulate. It may be OK now, but when the load gets higher (colder out) you end up with one system trying to heat two different spaces and the basement will win by being warmer than the first floor.

Foil faced ain't gonna get you much "reflection" of the radiant energy. For one, the foil must be high quality aluminum, super shiny and clean to reflect the radiant. Unfortunately when foil faced insulation is made, none of that is met.

No air gap if using the heavy extruded plates, you want conduction to heat the floor which then will heat the room.
Some of the thinner plates use the air gap to "supplement and even" the surface temps of the floor. Check with manufacturer on their recommendation.

Dave H.

Plates are viega. Yes “heavy duty”. water temps are low. We just had a couple low teen and single digit nights here in southeastern ct. supply temps have been under 105. I don’t think I’ve seen temps above 110 in the past 2 winters.

hcpatel78

Hi RWHTG,
My name is Hiren and just joined this group... I am planning to do Radiant (Under Joist) for my colonial house (1000 sq. ft) I am going to install with noritz CB199 combi boiler. Do you mind to share your install (hydronic) pictures with me for my guideline?
my email is "hcpatel78@gmail.com"
Thank you in advance...