Considering Radiant, but have some concerns

Andy58

Hi all,

I am in the process of GC'ing my home construction, and need to make a decision on the heat within a week or so, but my plumber has been talking me out of radiant, I just think he is unfamiliar with it. Anyway, I have a few concerns about my situation. I plan on stapling the pex under the sub floor and putting hardwood flooring on top of it.

I have read on a website(full of very useful radiant advice) that aluminum plates are unnecessary, he recommends creating a 2 inch airspace with Foil double bubble Foil, stapled into the joist, and then filling the rest of the joist with fiberglass. The lack of aluminum will slow the heating, but once the floor is heated, its irrelevant(in his opinion).

The other concern is that I am installing a high efficiency wood burning fireplace, I am worried that if I keep the fire going for a week, the floor will lose its heat, and then will take a couple of days to catch up once the fire goes out.

Also, what is the recommended water temperature for this application, I am also concerned about damage/warping of the wood floor?

Thanks in advance for the collective wisdom!!!

Andy

Zman

More Questions

Andy,

What region  are you in? Have you done a heat loss calc? These are both deciding factors for radiant design.

Carl

kcopp

You are getting....

some bad advice. I suppose you could not use the plates...but you will not be happy w/ how the system performs. This is especially true w/ hardwood. Yes the extruded are pricey but they distribute the heat well, allow you to use lower water temps and that means lower bills and greater comfort. The other really bad gimmick is the double bubble foil crap. The manufacturers lost a class action lawsuit w/ all the big claims they professed.... just use as thick a piece of fiberglass or the like and you will be much better off. Oh and w/ the plates you do NOT leave an air space.... One way to get around the fireplace issue is to install a floor sensor/control to keep the floor at an even temp all the time. I have done this w/ a couple of jobs.

Andy58

Ok, so whats the best way to go at this point

Thanks for reminding me that you get what you pay for, and if you pay online, your paying for a dream!!!



Anyway, I am doing the labor on the floor (and possibly the manifolds) myself, and the plumber is doing the boiler.



So, my new question is, what is the best way to install the system? I am doing a hardwood floor(3/4inch quarter sawn red oak, was told this holds up to the heat). I am trying to decide between,



A) mud and sleepers,

Wirsbo .05 inch plates and sleepers,

C) or a thinner.024inch plate that is a double U shape 12inch wide by 24 long(thinnner plate more surface area, and about 40% cheaper)



I plan on cutting plywood for the sleepers, I have a lot of spare time watching everyone else/professionals work, so this will give me something to do, and I have about 2-3 months time before this would be done.



I have a heat loss calculation from my Energy Star Compliance guy, and the house is going to be Energy Star Compliant, I am assuming that I take this to a pro to decide the loops, and the water temp. Although I was under the impression that if I had an adjustable manifold, and patience I could equalize the system myself. (Please don't mock my ignorance, I am a jack of all trades, and an optimist, I'm just not skilled or fast enough to make a living at contracting)



Thanks

Zman

Radiant Precision

I would strongly recommend the book "radiant precision". All of these  questions are related to the heat loss calcs of your building. Once you have determined your heat loss you will know what temp the floor will need to reach on your coldest day. From there you can decide what type of emitters you will need. Keep in mind, if you are using a mod/con boiler you want big emitters so you can run the boiler as cold as possible. Depending on your climate the savings in energy could be huge.Of your 3 choices I think it is likely a ford,chevy dodge question. All 3 properly installed will work the question is what is the cost and how comfortable are you with the installation.

CMadatMe

Regret

You will regret not using plates. That heat loss is more then likely not accurate if it wasn't done for radiant. Maybe this article will help you out in your decision.



http://www.radiantengineering.com/PlatelessInRadiantville.pdf

STEVEusaPA

Some thoughts

1. Your plumber should have someone at one of his supply houses who reps radiant products, who could design your system. If your plumber is unfamiliar with radiant it's a good time to get an education.

2. You will be unhappy if you fail to use the aluminum transfer plates.

3. Proper design before you start is imperative. You're going to need a different near boiler piping (prim/sec, mixing, maybe bypass, etc), and a different control strategy from what you plumber is probably used to.

4. You definately want to get the radiant design and temperature right with the hardwood.

You're probably spending some serious money and especially time on this project. Spend a little more to make sure before you have to go back and redo things.

Maybe even hire a consultant. There are a few on here. They can advise you on the best equipment, design, and control strategy so you systems runs great right from the start.

Someone asked, where are you located?

SWEI

useful radiant advice

I have read on a website(full of very useful radiant advice) that aluminum plates are unnecessary, he recommends creating a 2 inch airspace with Foil double bubble Foil, stapled into the joist, and then filling the rest of the joist with fiberglass. The lack of aluminum will slow the heating, but once the floor is heated, its irrelevant(in his opinion).



I am genuinely curious how these turdbags actually manage to sleep at night.  Sigenthaler article alludes to an ASHRAE project http://rp.ashrae.biz/page/rp-1036.pdf which put this issue to rest ten years ago.  See figure 16 on page 28 and note the first three points of conclusion:



•    The use of heat transfer plates dramatically increased the heat flux emitted from a radiant panel by better distributing the thermal load to the radiant surface. The difference in thermal delivery for a system with heat transfer plates to that without heat transfer plates provides designers practical data showing the power requirements and the potential delivery from like systems;



•    Varying the insulation depth below the radiant conduit provided the opportunity to compare the two configurations. The advantage to mounting an insulating material near the radiant surface is seen when comparing a system with heat transfer plates to that without. The experimental data shows that mounting the insulating material 2” below the radiant panel increases the time required to achieve steady-state operation for a radiant system with or without heat transfer plates;



•    The experimental data shows the use of heat transfer plates with a radiant system significantly increases the heat flux to the occupied environment. The mounting distance of an insulating material to the radiant element does not greatly affect the heat transfer characteristics of the radiant system when back losses are minimized or eliminated. The thermal resistance of the radiant panel system depends solely on the installation and construction materials;