Staple up insulation question?

sy308

Hi, I am running 4 zones in my radiant system. One zone is in basement floor, two zones are first floor, one zone is bathrooms on second floor. House is under construction. The first floor zones each have high ceilings. I want to maximize floor heat in those two areas and am considering supplementing my staple up with additional insulation or plates. Right now we are using staple up bubble sheets but actually I am not sure they are installed correctly. Perhaps a correct installation will be a better start. Checking the floor temps with an IR thermometer gives notable hot and cool spots, varying by 2-3 degrees. Maximum temp of the subflooring is around 78 F with water temps of 135-140. Dealer set this currently, not me. They told me not to change anything.

When I am in the basement, I notice the bubble wrap is not installed uniformly. Some areas have 1" gaps at the end of the joist bays and the spacing to the subfloor varies but looks like it is 2" at the most in the center and flat on the edges. The bubble is often stapled to the subflooring, not the joists. In some instances the wrap must be touching the tubes.

Questions:

1. Is not the bubble wrap supposed to be oriented so that the joist bay has a several inch horizontal spacing to the subflooring (ie, 2-3")?
2. Should the bubble wrap be stapled to the vertical joists to yield the most uniform air space with the ends stapled flat and closing all other gaps?
3. How much of a gap should be seen from staple to staple holding the tubes in place? If not uniform, does it matter much?
4. If I add plates, how much effect would I see in variation of floor temps as I measure accross the floor? How much of a drop in temps are typical when carpet is added?
5. Should I plan on additional fiberglass insulation on top of the bubbles? How much will this enhance the performance and reduce the hot spots? Is there a written book or source for this information?

Thanks.

cruizer

Do a search

On this site, your questions have been answered many times.

Plates will spread the heat more uniformly across the floor. It will also allow your system to run at a lower temperature, therefore using less energy.

Use fiberglass insulation and press it up againt the tubing/plates/sublooor. This will force the heat directly upwards, and it will not wander around in your floor joists.

Many tests have shown the most effective staple-up systems use plates. Other tests have shown that bubble foil insulation generally doesn't do a whole lot. Again, do a search, those test results are running around on here too.

hr

Do you

have a heat load calc for the various rooms. The number you want NEED id the BTU/ square ft/ hr that is needed to heat the space.

With this info you can determine to best method for your installation.

Most heat loss programs will tell you when additional supplemental heat is need in the various zones.

Various test results show the plates will allow better conduction heat transfer. you may or may not chose to use them based on the BTU requirements. or possibly in some areas and not others. you may just add plates around the coldest perimeter areas.

The load numbers will better help you to decide.

I've yet to see an overinsulated staple up system Critical, and most overlooked, is the rim joist area. Foam blocks and expending foam is a good detail for this area.

hot rod

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Mike T., Swampeast MO

Bare-tube staple-up and suspended systems don't have much (if any) physical contact between the tube and the floor. The general insulation logic with these systems is to essentially create little convective "chambers" in the joist space.

The "chambers" should be sealed as fully as possible--not good if the insulation doesn't reach all the way to the ends of the bays. The rim joists at the ends of the bays should be very well insulated--rigid insulation is good for this--if a bit difficult to install.

In theory, about 2" of air space is left below the tube. This can be much easier said than done as you see...

The reflective bubble wrap, in theory, bouces some radiant energy from the tube back to the floor and the joists--again the practice more complicated than the theory--particularly as the surface gets covered in dust and reflects much less.

I believe that a good rule of thumb is to have a five times greater r-value below than above the panel. ¾" plywood has an r-value of about 0.8 and a thin carpet/pad combo come in around R-1.3 at a minimum. Staple-up without plates adds another R-2.7 or so at 8" centers. So, you have a panel r-value of about 4.8 and need at least R-24 below. (Note these are very nominal estimates.) Bubble foil has an r-value a bit larger than its thickness would imply, NOWHERE near R-24. You DEFINITELY need more insulation below the floor--LOTS more!

I have no idea of either the outside or inside temperature (nor if your insulation/weatherization is complete) so really can't comment about the floor temps you measure. Staple-up systems typically have very low temp variance across the floor because they rely on convection. Put carpet with an R-value of about 1.3 on top and the temp will probably drop around 6 degrees. Of course I don't know what control system is being used either...

You said "the dealer set the boiler temp". Are the people installing the heating system familar with radiant heat? Was a thorough heat loss calculation made?

Again, it's impossible to know much about your system with just a short message, but IMHO, the numbers you're quoting and the observations you've made don't seem very good...

Extruded aluminum plates that grip the tube tightly and completely as possible are wonderful. When using plates of this sort you insulate directly against them as they use conduction--not convection.