Pex or hanging unit

[Jack72]

Whats better pex under the floor or the hanging unit?

Just wondering if anyone has tried this???

I have a 10 yr old 2300 square foot house 3 bedroom 2 1/2 bath   with a 4ft crawl insulated all the way around the outside perimeter in the joist bays.          I would like to have warmer floors my house has carpet in bedrooms     Tile and hardwood everywhere else bathrooms kitchen hallway etc.             

My question is       What is makes better sence  heating up the whole crawlspace or adding pex where the tile and hardwood is???????            I know it would be cheaper with the hanging unit but I dont know how well it would do than the more direct pex under the floor???   Also have 6mil plastic down and pee gravel on top of that and all outside vents are insulated and sealed.

  I have a e-1450 by the way        your comments and help  are appreciated       Thanks Jack

[Holmes]

If you want the hanging unit to warm up the floors you walk on you will need to keep the crawl space temperature between 90 and 100 degrees.  In the long run it would be better to install the pex tubing than to keep the crawl space that hot.

[Raider Bill]

I think "thehardway" replied to a very similar thread a couple years ago concerning pex and wood / concrete floors. I don't know who started the thread or what it started out as but it would be well worth finding and reading it or if finding fails ask him again. He is very knowledgeable and descriptive.
If I have time I will look.

[Raider Bill]

https://forestryforum.com/board/index.php/topic,50481.0/all.html

Good discussion here about it. Not the one I was thinking of though still looking..

[Jack72]

Okay thanks Raider Bill and           Holmes

[scsmith42]

Jack, I have radiant heating in the floor of my shop.  It's the best heating that there is, IMO.

[Ford_man]

I have been thinking of doing the pex under the floor. My idea was to fasten the pex directly to the floor then use either roll insulation or have an insulation co spray the under side with foam. The foam will seal up any cracks and can be put on any thickness that you want.

[clif]

It is my opinion that if you do not run the pex in concrete, you are not getting max efficiency out of the system. Think masonry stove versus metal stove.  When the fire goes out which stays warmer longer. How long and how far will heat radiate out from contact on the tangent of the pex tubing by a piece of wood or the air temperature.  Will it work? Yes, but how efficient will it be?  Clif   Oh, they do make a metal plate that has pex attached that attaches to the bottom of your sub floor I think it is expensive though.  I would think if you really wanted heated floors, that with the brain power I have seen here on the FF a workable solution could be a collective effort.   Just off the top of my head:  maybe attach the pex to the bottom of the sub floor then figure a way to inject concrete.  Or make some wooden troughs that fit between the joists that would have pex and concrete in them and splice them together as you set them.  Some one up in the far north or south might have time to cogitate  on this.

[snowstorm]

I have been thinking of doing the pex under the floor. My idea was to fasten the pex directly to the floor then use either roll insulation or have an insulation co spray the under side with foam. The foam will seal up any cracks and can be put on any thickness that you want.

i did my own in floor heat several years ago. a few things would do different. i used 3/4" pex 1/2" would be easier to work with. some of the plastic clips to hold the pex up broke like almost everone of that brand. replace the nails with screws. i used taco oo7 pumps with check valves. no check valve on the one going to the water heater. staple bubble foil insulation covering everything between the floor stringers. floor temp can be in the high 80's or what ever you want.

[John Mc]

When building out house, we put blueboard over the subfloor, put in sleepers, laid in the pex, poured lightweight concrete between the sleepers, then nailed down our hardwood floors. In areas with tile floors, we didn't need the sleepers. Works very well, and has some thermal mass to help with heating efficiency. That's not really an option in an existing house.

Our neighbors built their floors normally, then tacked up the pex under them, between the joists, and put what looked like foil-backed bubble wrap up under the pex. They had a semi-finished basement, so there was not a big heat differential between the basement and the house (max 10 or 15 degrees F). I don't know if you'd want higher R-value insulation over a crawlspace or not?

I hadn't thought about the possibility of the spray in foam until reading it here. I don't know much about the foam, but I know you'd want to make sure your pex was up tight against the flooring above... if the foam gets between the flooring and the pex, you're insulating the flooring from your heat.

[beenthere]

John

When building out house.....

That is a fancy out house.  :      ;D

[John Mc]

John

When building out house.....

That is a fancy out house.  :      ;D

Wow. A pretty simple typo can really change the meaning of a sentence, can't it?

[Don_Papenburg]

Yep and it sounds like a big out house ;D

Staple up works fine . Use 1/2 " pex on 6" centers  , keep the runs of tube close to 200' .  use Thermax type insulation(Aluminum foil faced foam board) with a 1" gap from the tube so you have some reflected heat . Then you can insulate with cheaper insulation . The more insulation the better.

[John Mc]

Yep and it sounds like a big out house ;D

And if we ever decide to go with renewable energy, we can heat the water with methane...

[Corley5]

  I put a Modine 60,000 BTU heater in the basement to keep things warm while work continues on the addition.  The hanging heater keeps the place fairly warm.  The addition is 24X32 two stories with 10' ceilings on both floors and a 24X24 basement with an 8' ceiling.  The original part of the house is 24X48 with 8' ceilings on a crawl space with baseboard hydronic heat.   
  I've got all the materials on site for the install except the insulation which is on order and should be here this week.  The plan is to install 2 runs of 1/2" pex al pex in each joist bay using Peter Mangone standoff staples.  The circuits will be kept to no more than 250' and will be fed from and returned to distribution manifolds with flow controls and meters to balance the circuits.  Three speed Grundfos pumps will be used for circulators.  For insulation under the tubing I ordered R-19 fiberglass with foil facing instead of paper.  It'll be installed with the foil up to reflect the heat up into the floor.  This was cheaper than buying both insulation and the aluminum bubble foil stuff.  The joist are 2X10s so the R-19 will give a 4" dead air space next to the floor.  The subfloor is 3/4" OSB and she plans to have carpetting  ;) ;D  I hope it works  ;) :D ;D   

[Holmes]

  Corley5  It will work as long as the end of the bays is WELL insulated from the outside cold.  Holmes

[Jack72]

  I put a Modine 60,000 BTU heater in the basement to keep things warm while work continues on the addition.  The hanging heater keeps the place fairly warm.  The addition is 24X32 two stories with 10' ceilings on both floors and a 24X24 basement with an 8' ceiling.  The original part of the house is 24X48 with 8' ceilings on a crawl space with baseboard hydronic heat.   
  I've got all the materials on site for the install except the insulation which is on order and should be here this week.  The plan is to install 2 runs of 1/2" pex al pex in each joist bay using Peter Mangone standoff staples.  The circuits will be kept to no more than 250' and will be fed from and returned to distribution manifolds with flow controls and meters to balance the circuits.  Three speed Grundfos pumps will be used for circulators.  For insulation under the tubing I ordered R-19 fiberglass with foil facing instead of paper.  It'll be installed with the foil up to reflect the heat up into the floor.  This was cheaper than buying both insulation and the aluminum bubble foil stuff.  The joist are 2X10s so the R-19 will give a 4" dead air space next to the floor.  The subfloor is 3/4" OSB and she plans to have carpetting  ;) ;D  I hope it works  ;) :D ;D

Corley 
I one thing I was told about the carpet is the padding that is used there is a certain type of pad that is used for radient heat under the floor app  so it lets your heat through better   Thats one thing you might want to research before you install new carpet.    Regular padding acts as a insulator and wont let your heat through as well.       Thats what I was told anyway   Thanks for your reply           Jack

[Corley5]

  There's R-38 insulation all around the external area of the floor system both in the bays and at the ends of the house and these areas have been checked for drafts     Should be good there. 
  I'll check into the special carpet padding.  I've read that carpet is harder to get the heat through than tile or wood.  A deep shag isn't an option  ;) ;D ;D  Thanks for the tips   

[den]

Here is a lot of info pertaining to PEX, 100 pages.

http://www.radiantdesigninstitute.com/