Going With Under Floor Radiant, Have a Few Questions

 
TSox
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Post by TSox » Thu. Jan. 07, 2016 2:59 pm

Hello,
I'm still working on our foreclosed farmhouse and since the people that broke into it decided to cut out half of the copper finned baseboards, I made the decision to dive in and go with under floor radiant heat. I'll need to pull down the ceilings but I think I'll be happier in the long run. When I worked construction I put in quite a few of these systems in slabs but I have no experience with installing under floor joists.

I've talked to numerous people about this from DIY'ers that have done it, to Professionals. The information I get is so varied so I decided to see what you guys think. I've had someone that knows what they're doing come in and help me decide on the loop layout. It will consist of (4) 280' +/- loops for the upstairs and (4) 280'+/- loops for the downstairs. Each floor will be a zone. The basement will also be a zone but It will be heated with cast iron radiators. Water will be heated by my yellow flame stoker.

So far so good?

I did get some useful info from this thread Post by n0useforaname - Radiant Heat, Getting Nervous

After going back and forth on the install, I decided to spend the money on the heat transfer plates. I couldn't find anyone that wished they didn't have them but I did talk to one person that had to go back and add them afterwards because his boiler couldn't keep up. After the plates were added he hasn't had a problem so that tells me there is a little something to them.

My big question is about insulation. I'm getting conflicting info about insulating the ceilings under the second floor. Most people say it's not needed because the space below it will be heated but a few say I should insulate to keep from overheating the first floor. To be honest my budget is stretching thin and I'd like to go without it but I don't want to be kicking myself later.

What do you guys think?


 
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Rob R.
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Post by Rob R. » Sat. Jan. 09, 2016 3:56 pm

For best performance, you should insulate. The air gap between the insulation and the floor is important, and you want to limit the amount of air movement within the joist cavity.

Some people just use fiberglass insulation, since that offers sound reduction as well.

 
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cn670
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Post by cn670 » Sat. Jan. 09, 2016 4:33 pm

Don't skimp on insulation, I used reflectix for the reflective factor that will make your system work better. I purchased 4' x100' roles and cut them down to 17" or18" strips. Makes it easy for a 1 man install. For aluminum plates I made my own from aluminum coil stock and a homemade former to fit 1/2"pex. This saved me a ton of money but took time. When drilling holes for the pex I had a container of ice with water in it, I cooled the drill bit between every hole a cool bit cuts way longer .

 
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Post by Jesse584 » Sat. Jan. 09, 2016 5:14 pm

Tsox,
Here is a picture of my underfloor heat. I used the aluminum plates. Then placed fiberglass insulation uptight to the plates. My first and second floor is heated this way. The basement and garage have the PEX in the concrete. I built my house 15 years ago and the system works great! When ever we go to someone else's house to visit, my wife is always happy to come home to the warm floors!
I circulate the water 24/7. I use a 4 way mixing valve that changes the temperature of the water flowing through the floors based on outdoor and indoor temperatures. The original boiler I installed was a Buderus with Logamatic control. I later installed an
Axeman Anderson 130 Coal Boiler! I wish I had installed the AA 130 from day one!!
I would suggest you install insulation, that being said, my first floor was not insulated for 7 years untill I finished the basement, then I insulated. The system still worked fine for those 7 years and I honestly see no difference with the insulation installed.

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Post by Kenbod » Sat. Jan. 09, 2016 10:30 pm

I would tend to agree with what has been said so far. I'm a bit of a science nerd, so I'll add a few comments. First, insulation is good. It can help, and it almost never hurts. As said above, one member added insulation several years after he built and didn't note much difference. And that's what the science would suggest.

The hot tubing can surrender heat by convection, radiation, and conduction. With tubes secured by shiny aluminum plates, the primary transfer is overwhelmingly by conduction. The plates don't really allow convective gradiants. The radiation is an interesting topic. Aluminum is a great conductor but shiny metals have very low emissivity, ie: they don't emit/'radiate' heat well, even if they are hot. (Baseboard radiators depend on air current convection to warm the room.)

I would say that from a performance/efficiency/comfort/silence standpoint, the best option is pex in insulated concrete. Then comes pex in extruded aluminum plates. But there are practical and financial considerations in every job. That's where suspended tube, baseboard, and good old-fashioned radiators come in. There are literally millions of them out there working perfectly.

For reasons unrelated to the type of pex application you select, keep in mind that about 50% of heat loss is infiltation. Seal every leak you can. Good insulation doesn't fail, has no moving parts, and needs no maintenance.

 
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Post by n0useforaname » Tue. Jan. 12, 2016 10:11 am

I'll add a different perspective here... You said you are tearing out ceilings.. So will you be gluing drywall up after you are done? Or just using drop ceiling? Or??? Because IMO, if you are going to glue dry wall up to the joists, not sure I would bother with the insulation.. because those joists will still hold heat, and since it's the 2nd floor, the heat rising from the first 2 will probably be enough. But then again, if you are doing the plates and only fiberglass is required, it might be worth it.

And the biggest problem is, everyone does it differently.. Some people use fiberglass, others use denim, some use bubble wrap, some go inside the joist, some staple under, some run 1 piece down each joist, some run 2, some run 4, etc... the list is endless. But here is the thing.. I haven't talked to ONE person yet who said their system does not work.. everyone seems to be happy with what they have. The local guy here said "it's really hard to screw up radiant heat.. it's very forgiving".. and I can understand that. If you have 1300' of pex running beneath your floors with 140 degree water in them... your house is gonna be warm whether you have plates, insulation, or not. I know efficiency is another thing, but... I was always told once things get "up to heat"... maintaining that is super easy.

 
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Post by waldo lemieux » Tue. Jan. 12, 2016 10:32 am

Ill say that if you cant do plates and insulation , skip the plates. When installing the loops make sure the hottest water is going to the coldest spots, ie. outside walls , entrances and if you can under bathrooms. Too, if you have an area where there is a large number of tubes comming to and from the boiler, I usually insulate those to eliminate the hotspot as well as effectively shrinking the length of the loop.


 
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Post by TSox » Tue. Jan. 12, 2016 11:08 am

Thank you to everyone for the replies!

The ceilings will be drywall which is where my question comes from. Insulation makes sense on outside walls but one thing I didn't really consider was the sound reduction. The house will be hardwood flooring throughout so the investment in some fiberglass insulation may be worth it for that alone.

I hate to tell those of you that have used the "reflective" insulation products but you're much better off with good old fiberglass or foam board than these "reflective" radiant insulations. Certain types of heat can be reflected well. Radiant heat is not one of them. It all comes down to understanding how the heat is being transferred from the Pex tubing to the floor. The heat is not being "reflected" into the floor, it's being radiated into it. The reflective radiant barriers are nothing more than marketing hype and really does not help the system much if any. These companies use false engineering to try and sell overpriced aluminum foil and bubble wrap. There are even several Federal lawsuits over this and some companies have been run out of business for false marketing. The real R value to these types of products is in the R2 range at a maximum. They're better than nothing but not by much and certainly not worth what they cost compared to REAL insulation.

Just a few articles I pulled up on this. There are 100's if not 1000's of them.

http://www.nlcpr.com/Deceptions2.php

http://www.healthyheating.com/Page%2055/Page_55_o_bldg_sys.htm#.VpUhFup0yB8

http://www.greenbuildingadvisor.com/blogs/dept/musings/beware-r-value-crooks

 
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Post by n0useforaname » Tue. Jan. 12, 2016 11:24 am

I'm not saying you are wrong by any means, but I read some of those studies, and most of them are putting the bubble foil like a 1/2 away from the pex... which is a HUGE no no. Every article, instruction, and person I talked to said it has to be at least 4 inches or more away, or the radiant heat will actually go through it...

Either way... like I stated above, whether you use fiberglass, denim, bubble foil, or none... you still have 120-140 degree water flowing through your floors... so the chances of your setup not working, are slim to none.

 
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Post by Lu47Dan » Tue. Jan. 12, 2016 12:23 pm

Insulation under the tubing is a good idea as it will stop the radiant heat from warming the ceiling of the room below ot and help prevent the flow of heat upwards into the upstairs.
I helped a friend remodel his families farm house when he bought it off his parents. There was no insulation in any of the first floor ceilings, he could remember that the second floor was always warmer than the first when he was a kid, even with both doors closed at the top of the stairs. He went with radiant floor heating and insulation under it and now can control the temperatures of the rooms upstairs. He also had all the exterior walls spray foamed to cut down on the air infiltration. He cut the heat costs way down and is now running a Wood Gasification boiler to heat his house, he has about 60 acres of woodlot on his property so it does make sense for him to burn wood.
Dan.

 
TSox
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Post by TSox » Tue. Jan. 12, 2016 1:33 pm

n0useforaname wrote:I'm not saying you are wrong by any means, but I read some of those studies, and most of them are putting the bubble foil like a 1/2 away from the pex... which is a HUGE no no. Every article, instruction, and person I talked to said it has to be at least 4 inches or more away, or the radiant heat will actually go through it...

Either way... like I stated above, whether you use fiberglass, denim, bubble foil, or none... you still have 120-140 degree water flowing through your floors... so the chances of your setup not working, are slim to none.
I'm not disagreeing with you. I was commenting on the reflective foil that people use either with bubbles or without. Like I said, they work to a point and are better than nothing but the R value is so low why bother? Radiant heating doesn't "reflect" off of a shiny surface very well like infrared heat would, or at least this is how it was explained to me. An insulation tech gave us a demonstration once when I poured concrete for a living. He used heated water tubing in two boxes filled with concrete and two pieces of 1" foam board as the insulation underneath. One had a foil backing to supposedly "refect the heat back up and the other had a plain white vinyl backing. The thermal transfer (which is what we're discussing here) between the two was virtually identical using a temp gun. The reflective foil didn't really have an effect. The real gain you see with it is a slight vapor barrier keeping the heat from migrating where you don't want it. As I said before, there are much more effective and cheaper was to do that. I would think in this application, the air gap is needed no matter what type of insulation you use? You would want that air circulating under the joists but not down, correct?

 
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Post by waldo lemieux » Tue. Jan. 12, 2016 2:10 pm

TSox wrote: Certain types of heat can be reflected well. Radiant heat is not one of them. It all comes down to understanding how the heat is being transferred from the Pex tubing to the floor.
:nono:

http://www.engineersedge.com/industrial-equipment/infrared-ir-radiant-heating.htm

As you can read they are one in the same. The distinction your missing is that the underfloor pex is making very much radiant heat, you need mass as mentioned in the article. Plastic pipe wont give off a great deal of radiant energy. It will conduct heat to the air, aluminum plates ( then to the air) or a concrete slab which will then and only then produce any measurable / usable radiant heat. Staple up or aluminum plates really rely on conductive heat to an air layer ( 3">4") wich then conducts to the subfloor/ finish floor which will then conduct and radiate (limited by its mass) heat to your living space...... or not if you wish.

 
TSox
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Post by TSox » Tue. Jan. 12, 2016 3:15 pm

waldo lemieux wrote:
TSox wrote: Certain types of heat can be reflected well. Radiant heat is not one of them. It all comes down to understanding how the heat is being transferred from the Pex tubing to the floor.
:nono:

http://www.engineersedge.com/industrial-equipment/infrared-ir-radiant-heating.htm

As you can read they are one in the same. The distinction your missing is that the underfloor pex is making very much radiant heat, you need mass as mentioned in the article. Plastic pipe wont give off a great deal of radiant energy. It will conduct heat to the air, aluminum plates ( then to the air) or a concrete slab which will then and only then produce any measurable / usable radiant heat. Staple up or aluminum plates really rely on conductive heat to an air layer ( 3">4") wich then conducts to the subfloor/ finish floor which will then conduct and radiate (limited by its mass) heat to your living space...... or not if you wish.
:?
I'm no Engineer so maybe I'm not great at explaining my thought but I believe the article you posted is exactly what I am saying? I understand how radiant heat systems work. The heat "conducts" into objects of mass to create the heat for the room. Insulation is an object with low conductivity there forces the heat where you want it or away from where you don't. Reflective foil doesn't have any mass therefore it doesn't work this way.

That is the whole reason for the initial question. Heat always moves from hot to cold so if the first floor is heated, the second floor "should" be the direction the heat flows when called for. Regardless, I think the noise reduction along with the heat benefit will be worth the investment in some fiberglass insulation.

As usual this isn't a place I can save a buck :lol:

 
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Post by joeblack5 » Thu. Jan. 14, 2016 12:46 pm

I used 3/4 pex with oxygen barrier against the bottom of the oak 1" subfloor. Then there is another 1" oak tongue and groove floor. I wanted 3/4 so that I could have more flow with a smaller pump. Also the larger circumference radiates more. Did not use aluminum plates. Increased the length of the run by zig zagging it in between floor joists. Later I read that sometimes pex in aluminum makes sound because of the different expansion / contraction ratio of pex versus aluminum.
The temperature difference between the floor right above the PEX and halfway is 79 F versus 66F.
At some locations I used reflectics at 2" spacing below the PEX and the spread in temperature gets less. So it does help a little.
water temp at boiler 140F and 120 F and where it enters the house 135 and 125.

Later J

 
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Post by n0useforaname » Thu. Jan. 14, 2016 12:58 pm

joeblack5 wrote:I used 3/4 pex with oxygen barrier against the bottom of the oak 1" subfloor. Then there is another 1" oak tongue and groove floor. I wanted 3/4 so that I could have more flow with a smaller pump. Also the larger circumference radiates more. Did not use aluminum plates. Increased the length of the run by zig zagging it in between floor joists. Later I read that sometimes pex in aluminum makes sound because of the different expansion / contraction ratio of pex versus aluminum.
The temperature difference between the floor right above the PEX and halfway is 79 F versus 66F.
At some locations I used reflectics at 2" spacing below the PEX and the spread in temperature gets less. So it does help a little.
water temp at boiler 140F and 120 F and where it enters the house 135 and 125.

Later J


So you didn't do a loop in between joists, you just literally zig zagged one run? I"m assuming it keeps your house nice and warm?


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