Adding 220 sq ft radiant to existing system

spacoli

Hi to all.



 Just some back ground first. I have a nat gas mod/con boiler connected to the old cast rads and old iron pipe. It's working well. The past winter the boiler fires at 135 degrees at 20 degrees outside. But naturally it would fire higher if needed. I have a separate zone T  and the relay ready.



I just built a four season room off the back of the house over existing concrete slab.The room will have a gas fireplace to heat it and would heat it just fine, but I thought I would try radiant to keep the temp decent instead of solely relying on a inefficient gas fireplace.   I framed up the floor with pt lumber  to level the floor out from the old sloping concrete.  I plan on spraying closed cell foam.Then lay a foil backed reflective barrier in each floor cavity leaving enough room for 1/2" pex loops before I lay the sub floor.



My question(s) 



Does the above sound okay?



What  is the best way to make the connection (controls,valves?) to the other zone I have ready?



Thanks

kcopp

If that is....

where you are why no get a few pieces of Warmboard to put in. Now you are not doing a reverse staple up set up. The response time will be a lot less....

Zman

I have concerns

I think the response time is a concern. I also am not certain the air space is big enough. How will you secure the tubes so it doesn't sound like snakes under the floor?

The idea of sections of warm floor is good. You could also figure out a way to retrofit joist trak.

It sounds like you could control it with a zone circulator. If you post a picture of the boiler piping it would help

Carl

RobG

Radiant Floor

Why not put down 1" of extruded polystyrene in between the 2x4's and then staple down the pex and do a concrete over-pour? It seems like the easiest way to me.

Rob

Jack

How about

insulate with the ridged foam, tubing, light weight aggregate pour, 1/4" cement board and ceramic/stone tile. That would eliminate any noise and improve the response time.

Gordy

Why not

Insulate floor with 2" foam, and deck with 3/4" plywood then do a sleeper radiant set up with plates.



Gordy

spacoli

Limited budget

Thanks for all your great ideas, but I'm working with a very limited budget and I already have the closed cell foam Dow froth pak for free from my workplace that has shut down. This will serve the same purpose as rigid foam and has a high r- value per inch.



I was planning on securing the pex with the long plastic staples used for foam board. This closed cell foam set up pretty firm.



I have a second zone piped with a shut off ready for a circulator  and a three zone relay.



I understand some of the concerns, but I'm not looking for the perfect set up. I just want to take advantage of some materials that I already have to work with and make the best of it. If i can get some heat out of the pex under the floor and not have to heat the room solely with the gas fireplace I want to do it. Don't get me wrong, if I'm wasting my time and this won't heat the room, I won't do it.



How much air space should I leave? My space varies (2 1/4"-3 1/2" next to the house to 5"-6" out at the exterior wall) because of the sloping concrete.



Thanks for all the help.

spacoli

Concrete pour

Okay, I think I misunderstood  the concrete pour suggestions. I was thinking all the framing would have to be removed and pour a new floor.



I was doing some more research after posting my reply. I came across an installation video using a concrete mix over a shallow floor build up similar to mine.



So I think this sounds good as long as I can get the right mix at a home center and mix/pour myself.



Questions: What type of mix do I get?  How much space between the foam/reflective barrier and the top of the joist for concrete?



Thanks

RobG

Concrete overpour

Since you already have the foam, and if it's PSI strength will suffice. Pour it inside the framed area of the floor leaving it no less than 1 1\2" below the top of the 2x4s. Staple down your tubing and pour the concrete into the bays. You can level it very easily by dragging a board across the the top of the 2x4s. Having only 1 1/2" of concrete to heat through you should have pretty good response time depending on the flooring you choose. You have to do a heat loss of course to ensure the radiant will suffice to heat the room. I would not bother with the bubble foil, you want your concrete to be in contact with the finished floor.

Rob 

Zman

Great plan

I was thinking the same thing and saw Rob's post. You could probably go as thin as 1". Any medium weight concrete should do, just don't use anything lightweight as it will insulate.I would just pick up some regular concrete mix and do it on site. Be sure to use pex with an O2 barrier. It sounds like you could do it with a 300' roll. You will get much better performance if you do two loops of 150' as opposed to one longer loop, 300' will technically work.

STEVEusaPA

I still like....

Kcopp's suggestion:  looks like you need 5 or 6 pieces of 4x8, t & g, 1 1/8" warmboard.  It costs a little more, but after deducting the price of 3/4 t&g, I think it's well worth it, much easier, much less labor intensive.  And you get a better job.

spacoli

Thanks

Thanks for all the input.



The warm board sounds like a good system, but I already have the decking from my work place also.  I would need 7- 8 sheets.  The concrete sounds like a good idea and will cost around $125. - $150. at the most.



The reflective foil backing is not bubble foil. It's just a foil backing  rf/voc barrier ripstop material. I wanted to install on top of the foam and staple to the side of the framing, then lay the pex on top.

kcopp

another option....

is to get a really good sized used CI radiator to put in there w/ a TRV... it would match the house. no extra mixing. less money and time.

Gordy

I would make sure

You wire nail some cleats in the concrete floor next to those joists mid span, and shim/ nail the joists to the cleats. Those PT 2x4's are going to twist, and bow causing the floor to buckle guaranteed.



Gordy

spacoli

I was planning on doing that.

My original plan was 2x6 for the floor, but I had to use 2x4 to keep some extra ceiling height. I need to frame down the ceiling also to get R-30 in there. I'm going to use my 2x4 cut offs to shim or scab blocks to sure up the floor.



Thanks for looking out for the weekend warriors.

spacoli

Two loops

I had come up with around 350' of pex that does not include bends.  I have a 500' roll.



I'm guessing I need two circulators with two smaller loops? Could you explain what the benefit is with two smaller loops vs. one larger?



Although I don't see me hooking this up to my system right away. My original question had to do with what do I need to hook this up (valves, controls, circulator (s))?



Do I need another t-stat in this new room? Probably be a good idea.



I have an HVAC engineer friend I'm meeting with Saturday. He is very busy and it's the first time chance he could see me. He does large commercial buildings, so usually he has to "downsize" his thinking cap when dealing with me. He had helped me with my system when I installed it. I'm sure he will do a heat loss and size my circulator and loops. I'm sure he will have answers for me also.



Thanks

spacoli

Update..... pex loops run

Well I spent the day running the two loops. I joist spacing was perfect for running the two loops right up the center then directly to the two ends with the supply, then worked my way back to the center with the return.  When terminated to a circulator the pipe lengths should be almost exact.   What I did was temporarily tape the pex down as I did my loops. Then I stapled down some 16g galvanized wire over the joist.  Then I cut all the tape and zip tied the pex  on 8" centers. This also brought the pex within 1/8" to 1/4" to the bottom of the sub floor.



Over all I think it's turning out well for an armature job.



I have been doing some research and found one installation using sand instead of concrete to fill the cavities. I also read sand is a insulator and will not conduct the heat as good as the concrete. Since my pex is up high now, do you think I can get away with filling the cavities with sand instead of concrete? It would be allot simpler and the sand would actually help insulate the floor more below the pex.



All thoughts and opinions are greatly appreciated.



Thanks  

RobG

Finished floor

What type of finished floor are you going to put down? I would definitely pour concrete, no sand! I can't tell from the photos how much depth you have below the sleepers. Concrete will transfer heat much more efficiently.

Rob

Paul Pollets

Foil up??

Why put a foil-faced product in contact with a concrete or drypack mortar pour? The concrete products will react to the aluminum.

spacoli

Amature

I just had some that I got for free and laid it down.



 What will happen to the concrete of foil?

spacoli

Finish floor

OSB sub floor;, then we want to do tile eventually. The depth varies (1"-3") because of the sloping concrete below. I want to fill in the deeper areas with sand to save on concrete. Some areas will be concrete only because it's shallow. 

kcopp

NO SAND.....

waste of time....it will insulate and stop proper heat transfer. I would leave it as is and just run higher water temps though. w/o plates you don't have a lot of choice. What did you use for insulation?

spacoli

Insulation

1"-2" of closed cell spray foam over old concrete slab and then 3/4" rigid foam board. I'm figuring I have an R-10 at the least and R-16 at the most.



What higher temp. are you talking? My boiler has hit 135 degrees at 20 degree outside temp. over this past winter. I would rather keep the temp. low with a mixing valve and add concrete if that's what needs done.

spacoli

Pex length difference question

After running the pex where it will be terminated, I looked on the pex foot markings and figured up each circuit length. One is 237' and the other is 243'.   Even though they were run identical , some how I have around a 6' difference between the two. I thought they would be closer then this. I figured they are within 3% of each other. Does this pose any problem with the flow between the two? 

spacoli

heat loss

I used the slant fin heat loss program and come up with 10,000 btu loss. In the floor I used thin concrete slab with 3/4" pine floor and vinyl flooring. Vinyl floor seems to have less resistance than tile and that's what my wife really wants. The water temp is 123*.



The tubing amount on the program is 38' shorter than what I figure I used (237' + 243' = 480 .



Can anyone recommend a circulator size based on these calculations, pipe lengths and typical connection to manifold,mixing valve and circulator ?