EcoRenovator  

Go Back   EcoRenovator > Improvements > Renovations & New Construction
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 10-10-12, 07:16 PM   #1
dumkat
Lurking Renovator
 
Join Date: Oct 2012
Location: London, Ontario
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
Default Hydronic floor heating

We have an old home with a floor that has no sub floor. We will be removing the plaster from the ceilings below the the second floor and already have access to the floors of the main floor from the cellar.

My question is, what is the best approach to installing pex tubing to heat these floors?

Do we add a psuedo-subfloor in between the joists?

dumkat is offline   Reply With Quote
Old 10-10-12, 08:57 PM   #2
Daox
Administrator
 
Daox's Avatar
 
Join Date: Aug 2008
Location: Germantown, WI
Posts: 5,471
Thanks: 1,110
Thanked 367 Times in 298 Posts
Default

Hello Dumkat, welcome to the site!

Typically, stapling the tubing under the subfloor is not a very efficient way of heating. But, considering that you don't have a subfloor, the best option might just be to staple up pex tubing to the flooring with heat spreaders on them. You definitely want the tubes in good contact with the flooring so the heat can be transferred as good as possible. Do you have any pictures that might help us out?
__________________
Current project -
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Daox is offline   Reply With Quote
Old 10-11-12, 07:44 PM   #3
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Get a thick aluminum heat pan from Rehau or Warmboard and have the spacing at most every 8". Then put 3.5" min of rockwool right up against it, then drywall. You can put a radiant barrier but it is of limited value.
Mikesolar is offline   Reply With Quote
Old 10-12-12, 11:24 AM   #4
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by Mikesolar View Post
Get a thick aluminum heat pan from Rehau or Warmboard and have the spacing at most every 8". Then put 3.5" min of rockwool right up against it, then drywall. You can put a radiant barrier but it is of limited value.
Mikesolar,

I'm pretty sure Warmboard is fixed at 12" centers...

(* Please let me know if I'm wrong. *)

Roth Panel is spaced at 8", very good design.

Best,

-AC_Hacker
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 10-14-12, 03:23 PM   #5
Minimac
Lurking Renovator
 
Join Date: Oct 2012
Location: Upstate NY
Posts: 29
Thanks: 7
Thanked 2 Times in 1 Post
Default

It's been my experience that there are much better ways to do this-especially in an older home - than using Pex. Pex itself is cheap but by the time your done with a mixing valve, clips, pans, manifolds, etc., it isn't inexpensive. IMHO, a much better way is to run fin tube(without enclosures) in the space between the floor joists. Even if you only do every other joist, you'll end up with a well heated floor. I divert a line off of a return before it goes back to the boiler and hit 4 or 5 joist spaces, then back to the boiler return line for that loop.
You're pulling heat from the return that would normally just dump back to the boiler. Your heating line should be leaving the boiler @ somewhere between 180*-190* and even if it's returning at 140*, that's better than you can do with Pex.
I don't mean to offend anyone,especially in my first post here, but to me, Pex is glorified garden hose.
Minimac is offline   Reply With Quote
Old 10-14-12, 03:53 PM   #6
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Quote:
Originally Posted by Minimac View Post
It's been my experience that there are much better ways to do this-especially in an older home - than using Pex. Pex itself is cheap but by the time your done with a mixing valve, clips, pans, manifolds, etc., it isn't inexpensive. IMHO, a much better way is to run fin tube(without enclosures) in the space between the floor joists. Even if you only do every other joist, you'll end up with a well heated floor. I divert a line off of a return before it goes back to the boiler and hit 4 or 5 joist spaces, then back to the boiler return line for that loop.
You're pulling heat from the return that would normally just dump back to the boiler. Your heating line should be leaving the boiler @ somewhere between 180*-190* and even if it's returning at 140*, that's better than you can do with Pex.
I don't mean to offend anyone,especially in my first post here, but to me, Pex is glorified garden hose.
Boilers are not intended to have such as high dT (20F is the norm and 30F for commercial DHW boilers is norm) and any boiler that needs to run at 180F is not as efficient as can be. Copper fin boilers will have more expansion than designed for if they run at such as spread. Not good for cast iron either.

The goal with any heating system is to run as low temp as possible to be efficient. That said, I once did 20 houses using copper fins as you talk of, and they were up in Fort Francis, Ontario (-40C no problem) and run off a water heater. We placed them in the perimeter joist spaces and let them radiate up. They were low energy houses and I can't remember how many feet of fin tube there was per house but it worked (it was 20 years ago).

PEX has its place which to me is in an embedded slab although I have used it for almost everything short of steam. Wirsbo tubing (Uponor now) used to talk about taking a piece of PEX (in the late 60s when it was developed) and
which was placed in a steam heat test at steam pressure. Every month it was removed and measured and since that first test till the mid 90s when I talked to them, it had lost 5% of its wall thickness. This is an extreme example of how a good cross linked tubing can be so in a floor application at 100-120F..........no worries. The biggest issue is O2 barrier.
Mikesolar is offline   Reply With Quote
Old 10-14-12, 04:12 PM   #7
Minimac
Lurking Renovator
 
Join Date: Oct 2012
Location: Upstate NY
Posts: 29
Thanks: 7
Thanked 2 Times in 1 Post
Default

Your a much braver man than any I know if you'd use Pex in a steam application!
Minimac is offline   Reply With Quote
Old 10-14-12, 07:01 PM   #8
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Quote:
Originally Posted by Minimac View Post
Your a much braver man than any I know if you'd use Pex in a steam application!
Oh, I wouldn't use it for steam. That was just for their testing.
Mikesolar is offline   Reply With Quote
Old 10-16-12, 06:47 PM   #9
Minimac
Lurking Renovator
 
Join Date: Oct 2012
Location: Upstate NY
Posts: 29
Thanks: 7
Thanked 2 Times in 1 Post
Default

I would agree that in a slab, it could work fine. I just think that, in the case of the OP and an old home, there are much better and cost effective options. Look at the manufacturers temp ratings on the tubing. High efficiency isn't worth much if it isn't cost effective. The goal of any heating system is to keep you warm when it's cold. If it can be done cost effectively, so much the better!

Last edited by Minimac; 10-16-12 at 06:53 PM..
Minimac is offline   Reply With Quote
Old 10-18-12, 08:34 PM   #10
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by Minimac View Post
High efficiency isn't worth much if it isn't cost effective.
If you take a look at energy prices, and the steep increase in prices, it is clear that "cost effective" is a moving target, with a pretty short life.

A cost effective installation done today may not be so desirable in 10 years, when energy prices may have risen sharply.


The life of a car is fairly short, when compared to the life of a house. There are a large number of houses that were poorly insulated and used lower efficiency heating systems, even when better insulation and more efficient heating systems were available. But they were built to be "cost effective". At the time, it seemed prudent to build them that way, now they are a burden to heat.

As a home owner, or a builder the "cost effective" measure needs to be observed to be competitive.

However, some countries do not leave everything to the market place... Some of the Scandinavian countries, for instance have mandated insulation standards that are much higher than ours. If someone can't afford the standards, the government can help them.

Many of the folks here at EcoRenovator volunteer to install much higher than standard (cost effective) levels of insulation, and heating systems that are more efficient than is 'reasonable'.

You might even say that there is a friendly competition in that regard going on.

Best,

-AC_Hacker

__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:27 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design