Seeking comments on open engineered trusses vs. closed trusses on staple up with dispersion plates installation.

Specifically, by open floor trusses I mean pre built engineered trusses with a top plate 2x4, bottom plate 2x4 and criss/cross 2x4's in between. Typically 16-18" tall

Closed trusses consist of a top plate and bottom plate with a closed ox board joiner, also typically 16-18" tall.

It would seem open trusses are much more difficult to to install insulation in and direct the heat up, even  though the plates are dispersing the heat to the sub floor?

The open truss will be considerably easier to install the radiant pex pipe, drilling 1 3/8 holes and weaving the pipe is not an easy task.
The heat transfer plates with the insulation will drive the heat upward.
Dan

As Dan indicated, open trusses would certainly make the install much easier. However, it sounds like this is for new construction? If so, why not use a more efficient Above-Floor assembly in lieu of Below-Floor? Is there another reason why you need to run high supply temps for the heating system?

Posted By sailawayrb on 21 Apr 2013 01:08 PM
As Dan indicated, open trusses would certainly make the install much easier. However, it sounds like this is for new construction?

If so, why not use a more efficient Above-Floor assembly in lieu of Below-Floor? Is there another reason why you need to run high supply temps for the heating system?

I am considering above floor also (yes this is new construction), possibly wamrboard or similar product, but I have not yet ascertained the cost per square foot of a warmboard type product, that coupled with the 2nd sub floor that would need to be installed above the warmboard and the costs keep inching up.

This will be coastal no Cal and it rarely drops to freezing in the winter (typical lows Dec - Feb are high 30s ~low 40s)

I am probably under the misunderstanding that closed trusses help in keeping the heat from escaping, that is what the insulation under the radiant is for.

Sorry, I don't understand the last question ("Is there another reason why you need to run high supply temps for the heating system?")

I guess my question is more around why you would choose to do Under-Floor which requires significantly higher supply temps to generate the required building heat gain as compared to Slab-on-Grade, Thin-Slab, or Above -Floor. Higher supply temps require more energy to achieve and also have higher parasitic heat loses. One would normally only consider Under-Floor for a remodel situation...where energy efficiency is traded for installation efficiency.

We use extruded plates regularly, in fact today, on new construction when we are not consulted before the trusses are ordered, necessitating a sub-floor system to meet the heat loads and contiguous floor levels.

there is no second subfloor required over a warmboard system.

We are using warmboard and love it. that said joist applications can be extremely effective and low temperature if your heat loads are low. Also, there are hybrid options that work if budget is more important.

We would second Rob's recommendation of using Warmboard for Above-Floor if you want to avoid doing Thin-Slab which certainly requires more installation savvy, but would likely be less cost.

We offer the RHT Floor panel system, a surface mounted system that apply s on top of your sub floor.
Considerably less cost than warmboard. (about 1/2)
Dan