Warmboard vs Viega for radiant heat retrofit

rjainms

Retrofitting a 3000 sq ft 2-story 1970s house, roughly 1500 sqft per floor. Currently has forced air, retrofitting to radiant heat, on both floors.

Local contractors use either Warmboard or Viega. Its probably best to have the contractor use the panel they are most comfortable with. But any comments on which is preferable?

Thanks!

hot_rod

Properly sized and installed either will do a great job.

Have you looked at samples of each?

WB R is a 13/16"thick ply with aluminum cover, it takes 1/2" pex.

The Viega panels are much thinner have the transfer plate below and use 5/16" tube.

So be aware of the additional thickness added to the floor. It will mess with door openings, base trim, and stair rise, assuming you have stairs.

Pros and cons. The Viega is nice for retrofit as it doesn't add much to the floor height. Loops will be much shorter, so more runs to a manifold.

WB with a continuous aluminum upper layer really moves the heat nicely, very even floor temperatures. You do need to consider the thickness plus the floor covering. 1/2" tube but at a 12" oc I believe.

STEVEusaPA

Might want them to price it up both ways. Warmboard is the most expensive.
I just got these delivered https://www.sunboardpanel.com/ to my house. I'm going to use them for a 600 sqft family room. They were 1/2 the price of Warmboard.

rjainms

Thanks Hot Rod and Steve for the responses!

I did see the height difference, which makes the Viega attractive.  

But somewhere I read that the thinner tube with the Viega means that there is less water flow so it takes longer to heat up (response time is more) and also you have to run the water at a higher temp.  Also the tubing is a less standard size so harder to get parts etc. So over the long run the extra expense with Warmboard is offset by better performance and lower running costs.

Thanks for the pointer to Sunboard.  Looks like they have different panel thicknesses and different tubing sizes. @STEVEusaPA which one did you use?

@hot_rod, what difference does the shorter loop length make?

hot_rod

On large square footage areas you end up with more loops, and trips back to the manifold location with the smaller tube.

275- 300' is acceptable for 1/2" pex loop lengths.

I would stay away from any system that is particleboard, even MDF. If it gets any amount of spilled or leaked water on it, it tends to expand and come apart.

The two you are looking at are actual plywood based, durable and they hold nails well, if you use any nail down hardwood.

Code requires no more than 3/8"difference on stair tread rise. And beyond that it is something you can really fell walking the steps, called a tripper.

Lay a piece of 1/2" plywood on one of your stair treads and walk in in the dark

Alan (California Radiant) Forbes

But somewhere I read that the thinner tube with the Viega means that there is less water flow so it takes longer to heat up (response time is more) and also you have to run the water at a higher temp. Also the tubing is a less standard size so harder to get parts etc. So over the long run the extra expense with Warmboard is offset by better performance and lower running costs.

Both are great products. The Viega advantage is that it's 5/16" thinner than Warmboard-R which is often important on retrofits and the tubing is a lot easier to handle.

I've never heard that response time is slower and that you have to run higher water temperatures. If that is so, I don't think you would notice, especially with a mod-con boiler and outdoor reset.

Rich_49

Just to be clear , Sunboard offers both plywood and composite product . Sunboard performs as well as either mentioned product .