radiant heat checking on a few facts

[keeney]

Besides the issue of growing stuff in your potable water whcih I will avoid debating, these are the other issues with an open vs. closed system:

An open system is not compatible with any anti-freeze.

An open system is typically run at water supply pressure of 50 to 100 PSI. Closed systems are typically under 20 PSI. The PEX is typically rated to 200 PSI, but at only 20 PSI, it is going to last forever.

An open system continuously introduces oxygen which means you have to use aluminum, copper, brass, or stainless fittings, pumps, valves, manifold, boiler, etc. The closed system can use cast-iron pumps, fittings, etc. However, the closed system then needs PEX with an oxygen barrier - the open system can use cheaper PEX tubing.

A closed system with needs an bac-flow prevention valve if its directly connected for filling / makeup water.

There are also hybrid systems where a water heater on the potable water side is used to heat potable water for domestic hot water. That hot water is also circulated through a heat exchanger to provide heat to the radiant system. The radiant system would eb a closed system with anti-freeze, etc.

- Rick

 

[KubotainNH]

Yes my system is an "open" system. The issue that would bring legionnaires' disease is either water that is stagnant or to low a water temp. My system has water running through it year round. In the summer it runs cold water when using the tap, shower etc. I also make sure the water temp is high enough to kill the bacteria. I did quite a bit of research on this so called disease but found very little real cases. I have a valve that limits the pressure in my system to 50 lbs, plenty for good pressure. I mentioned the anti-freeze and heat exchanger because I didn't think having anti-freeze heated in a boiler would be good for the boiler but it was only speculation. /forums/images/graemlins/crazy.gif

 

[Sigarms]

I'm talking strictly about a closed or open system pertaining to a hydronic heating system.

I could of misunderstood the statment, but I'm taking the statment as meaning that with a open system, you can run into serious health risks.

On that note, I would not design a radiant floor layout with an open system due to the PITA factor.

 

[JimMorrissey]

I used a raidant "blanket" under the slab. It was big rolls of thick insulation and was very easy to lay out....can't remember the name of the stuff. I then covered the blanket with wire mesh and zip tied the loops to the mesh. It was pretty easy and very effective. Next time (this coming spring) I will definitely run the loops at 8". With 12" loops I could feel the heat difference with my bare feet. If you can get 5/8, I'd do it. The more water you can move the less heat loss you'll have in the end of the line. Also as others have said, it is very important to insulate the edges of the slab. I used foam and cut the top of it at a 45 degree angle, this way the concrete covered up the last little bit a the top and you couldn't see the insulation. It just blended away. Sounds like all you need is one zone unless you want a toasty office or plan something for the space in the future.

The Web is a fantastic source of good and some bad info. Keep reading. One thing for sure is that you're going to love the radiant floors....It's an awesome way to heat.

 

[SPIKER]

I belive you have mistaken the terms "Open System" and "Closed System". in real terms what it actually is referning to is if the system is pressurized and has no dirrect contact with atmosphear anywhere in the system. a closed system is more of a steam type system and opperats continusly under pressure. boiler/hot water tank, PEX, pumps & Expansion tank and all are "At Pressure of 20~100+ PSI. and is a CLOSED system they DO get makeup water but only when the pressure dropps below the intake fill valves set point. (think of a check valve with city/house water on one side and the closed system on the ohter, the water can flow from city/house to the radiant system but NOT back. the PRESSURE in the PEX system stays constant due to requirement of a Expansion tank, and the AS NEEDED fill from the city water.

in an OPEN SYSTEM there is little or no real pressure in the boiler & piping system other than down stream of the pump where restriction to flow causes SOME pressure but usually only a few lbs. often these are typcial for outside wood boilers (term boiler is not really accurate but is often used.)
the open system requires lower water temps, 150~180 degs F any higher then and boil off of water results and the fill / intake is worked much harder. which means the cold water intake requires morew wood to warm it up. often there are simple float valves which regulat the water height inside the boiler.

there are many brands of tubing one of the better has multi layers, such as "Pex-Al-Pex" (as name implies it is a layer of PEX tubing and a layer of Aluminum tubing then a 2nd layer of PEX. ) these are typical of BARRIER tubing (which lets in/out none of the O2 so steel can be used in the stytem. typically a steel hot water tank and cast pumps.) open systems need to use brass, S.S. and Plastic componets to prevent rust problems.


typical system starts with a good base of rock/gravel, followed up by sand/pea gravel then all compacted. adding a vapor barrier on top of the compacted base. there can be several ways to proceed. you can use Poly Styrene, (styro-foam boards) or Foil-Bubble-Poly insulation all in conjunction with the the vapor barrier, taping seams as you go.

lay the tubing onto a 6x6 mesh grid and keep the runs 300' or less in lenght and runs 1' or closer together. (typically 6~8" for first 4' away from outside walls then 1' for the rest. this is for in concrete systems under floor systems where wood floor is used then the PEX is stapled to the flooring by means of the AL plates typically.

like others stated plastic clips can be used but wire ties to the 6x6' re-mesh is much simpler and faster as well as cheaper.

once the pex is laid & held down pressure test the system! leave pressure ON the system when pouring crete over it. the pressure inside will help it stay un-collapsed if it get stepped on.

also like stated make sure you have detailed drawings of WHERE the PEX is at incase you ever need to drill to mount a vice ect.

one good mail order place for PEX is farmtec I spent almost $2k for mine and I got 2000' of 1/2" and 600 of 1" PEX-AL-PEX as well as 4 rolls of the 8'x100' foil-bubble-bubble-Polly insulation. not bad and I got a free pair of wool gloves /forums/images/graemlins/wink.gif lol


Mark M
/forums/images/graemlins/crazy.gif /forums/images/graemlins/ooo.gif

 

[woodlot]

SIG - please check with RPA on their position re: radient systems that are intrigrated with potable water.

 

[robison]

</font><font color="blue" class="small">( Base - stone or sand?

In our new home we have radiant heat in the concrete slab and in the wood subfloor for the floor above.

In the slab we used gravel under the concrete. The outer ten feet of floor was insulated w/ foam boards. Then we put down the metal mesh and tied the pex tubing to the mesh before pouring the floor.

In 1/3 of the first floor the concrete is finished and it's the floor. In the rest of the floor we have 2x2 with 3/4 ply above, covered in carpet. The radiant heat works equally well through both floors but the temp needs to be a bit higher on the carpet areas.


Has anyone used the aliumium plates yet?
Also there are many radiant heat people recommend using aliumium plates they claim they increase heat transfer by 30 %. This same company advertised 1130 sq feet of tubing was over $3000 which seems high for the tubing to me when it is 37 cents a foot.

We use aluminum plates to staple the pex tubing to the wood floor on the 2nd floor. The plates are spaced closer together at the outside wall ends, 2 feet apart in the middle. Seems to work well but if I did it again I'd do plates everywhere under the bathrooms and other spots you might want warmer than other places.



Also what type of tubing has everyone used?
I have a plumber friend and I can do some of the work myself for the radaint heat. IT does not seem that hard to lay tubing.

We bought our tubing and parts from Radiantec in Vermont. They were good to work with.

When doing some of the labor yourslef what has it cost you per sq foot to install radiant heat? http://www.astrofoil.net/ASTROFOIL.ASTRO-WHITE.concrete.html
please exclude the boiler cost

The parts were no expenxive at all, perhaps $5,000 for 6,000 sq/ft of heated floor. The labor is the killer if you have to hire it out. Also the boiler can be 4-5k. I recommend a Weil Mclain modulating boiler.


This is a pole barn and it is a t shape the stem of the t is 30 x 40 and then the top part of the t is 28 X 90 with a 20 foot over hang which nothing will done right now. The barn is up and we need to add the floor. I plan on having r21 in the walls and as much insultation as I can blow in the ceiling I hope to get about R44. This is going to be a boarding kennel with the kennels in the center of the top part of the t for diagram go to the following link http://207.234.238.110/kenlayout.html

I used r50 in the attic and 8 inch walls, fully insulated. Not sure of the r value of the walls but it's pretty good.

I am very happy with the results we obtained.

 

[mlinnane]

You guys have been great for ideas. But I have been doing so more research and for what I can find you do not need to use the blue from board around the edges if you use a Radiant barrier which insulations as well as reflective insulation system that offers a permanent way to reduce energy costs. Radiant barrier insulation systems reflect radiant heat energy instead of trying to absorb it. the following web site
http://www.radiantbarrier.com/tempshield_double_bubble_double_.htm
has more doc. But I have called and email and they said there is no need to use the blue form board. Also you cup this along the edge like you do a pie crust. There are also blankets that have like r15 and have the barrier. IT would seem to me a great deal less work and offer less heat loose.
I just had 5 loads of crusher run brought to level off the barn on the part we need to fill in. I could of use stone but this section was built up about 5 feet when I did site work for barn when it was built a year ago and I wish to really pack the crusher run. Before I start I have to place two pipes in the ground for septic one to a dry well and then also about 6 pipes in the ground for utility room for electric, water, heat pipe, phones and satellite jacks for TV and internet. I really do not want to drill holes in concrete later. Then we will fill in with the crusher run and use a compactor. Then we will lay down radiant barrier and then the squares and then start the tubing. this barn is going to be a kennel and we will do the slab in three sections the stem of the T we will do first. this part of the slab will be level this area will be 30 x 40. The top part of the T will done in two parts. 28 x 45 and 28 x45. All of the floowing will have radiant heat. [image]http://207.234.238.110/kenlayout.html[/image]

 

[dmccarty]

michelle,

You might want to be careful with the crusher run. Our house has a concrete slab floor. The high side of the house was five feet above grade. Normally this would have required a crawl space. I despise crawl spaces. Our builder put in 67 stone to fill the up the space so we could pour the slab. The 67 stone is supposed to automagically compact to 95% or there abouts. No compaction was done on our fill and the floor has not moved. Our build is/was a PE so you might want to ask in a PE in your area how to do this.

I built a foundation out of retaining wall blocks and ABC gravel. I think ABC and your crush and run are similar. My fill has settled a good inch with maybe a foot or so of fill. I did not compact though.

You might be able to use 67 stone which is larger stone with no fines and not have to compact the fill.

If you have not done so check out the forums for JLC Online and Fine Homebuilding. I have read some discussions that were very heated, pun intended, /forums/images/graemlins/grin.gif regarding radient barriers.

We wanted to put in radient heating in the floor of our slab but for our area it did not make money sense to do this. But we did insulate with rigid insulation under the slab. I think we put in XPS with a R10 value. Seems to work for our climate. You might need more given you location. I found Joseph Lstiburek book on Mixed Climates worth its weight in gold. He has a book for Cold Climates that you might find interesting. He has a company called Building Science Corp out of Westford Mass. They have a website with good info.

I HIGHLY recommend his books. I put in foundation details from his books in our plans and they work.

Later,
Dan

 

[Farwell]

Question? Why do you despise crawl spaces? I will not have a house that is built on a slab because I want access to all of my plumbing pipes, drain pipes, electrical wiring, communication wiring, etc. There are horror stories about plumbing breaks under slab floors and the expense and inconvenience of having them repaired. I have lived in houses that had a very small crawl space and that was bad to work in but a well sized crawl space is great if you want or need to upgrade your utilities. I now have a full basement and am in hamburger heaven. Radiant heat can be added to the floors of a house that has a crawl space.
Just curious.
Farwell