Radiant floor heat retrofit

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
Removing the big radiators out of my small rooms would be a huge improvement. Also, I'm thinking a huge improvement in comfort.

Looking for good resources to use to plan a hot water based in-floor retrofit.

I'll be going in through the bottom, easy access under the wood floors in the cellar.
 

festerw

Feeling the Heat
Nov 16, 2009
353
Cambridge Springs, PA
I did a retrofit a couple years ago in my house. If you have enough room do two runs of tubing in each joist bay, I only did one and you can definitely tell "hot spots" on the floor. I think the heat would dissipate better with two runs but I also have true 3/4" floor boards so that may be part of the issue.

Using a thermal barrier on the bottom of the joists makes a huge difference, I saw a 2 degree temperature rise with 25 degree outside temps with no other changes.

I'm using an old hot water tank as the heat source, 3/4 pipe to the manifold, 1/2 oxygen barrier pex. 3 zones with cheap Honeywell thermostats, Taco 007 circulators, and Taco SR503 switching relay.

I'm sure there are better ways to do it but this works pretty well down to single digit temps.
 
  • Like
Reactions: Easy Livin’ 3000

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
I did a retrofit a couple years ago in my house. If you have enough room do two runs of tubing in each joist bay, I only did one and you can definitely tell "hot spots" on the floor. I think the heat would dissipate better with two runs but I also have true 3/4" floor boards so that may be part of the issue.

Using a thermal barrier on the bottom of the joists makes a huge difference, I saw a 2 degree temperature rise with 25 degree outside temps with no other changes.

I'm using an old hot water tank as the heat source, 3/4 pipe to the manifold, 1/2 oxygen barrier pex. 3 zones with cheap Honeywell thermostats, Taco 007 circulators, and Taco SR503 switching relay.

I'm sure there are better ways to do it but this works pretty well down to single digit temps.
What did you use as the thermal barrier at the bottom of the joists?
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
6,935
Schenectady, NY
Have you considered dropping the water temp in your big radiators? It makes a huge difference in comfort.
 

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
It's kind of like foil, but much heavier and it has nylon reinforcements running through it.

I looked at the foil backed foam but it was way more expensive and unnecessary for my basement since it's useable space
Makes sense. Thanks!
 

peakbagger

Minister of Fire
Jul 11, 2008
4,605
Northern NH
FYI, do a bit of research before jumping in on this. If you have a "thick" flooring system the response of the system is going to be limited. If you have conventional wood flooring that is another consideration. The problem is that the floor system acts like insulation so the heat tends to flow into the space under the floor. That is why using radiant shields and insulation under the tubing is important but ultimately the thicker the floor the higher temp water you will need to run. Definitely avoid rugs or carpeting.

Once you go radiant in the floor, its set the thermostat and leave it there, no set back as the response of the system is quite slow. It works well in tight homes with tight windows but is less successful if you have a lot of heat loss in the wall and window system. Generally radiators are placed under windows as that is where the heat loss is and if they arent there you may start noticing drafts and cold spots near the windows. I have seen several references to folks having to install insulated blinds on their windows when they switched to radiant floor heating due to the combination of high infiltration and the cold windows causing it to be uncomfortable when sitting near the windows.
 

zrock

Minister of Fire
Dec 2, 2017
699
bc
Have you thought about upgrading your old rads to the newer more efficient and smaller rads?
 

zrock

Minister of Fire
Dec 2, 2017
699
bc
Google is your friend... you can get them similar to electric baseboards, slimline, wall mount, and everything in between

Sent from my SM-G903W using Tapatalk
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
6,935
Schenectady, NY
No comprende. They work hard to provide any heat as is.

A house needs a certain number of btus to stay at a certain temperature.

Many systems have the water temperature set at around 180-190F. They deliver this heat in short bursts.

The boiler turns on, blasts out heat, then turns off. You get an on/off effect that really isn't steady. Your body feels this.

Lower water temperature can deliver that heat with longer cycles at lower temperatures. It's what radiant heating systems do. Only its using the system you already have. The fewer on/off cycles give a more steady heat and the cycles are easier on the equipment.
 
  • Like
Reactions: Easy Livin’ 3000

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
A house needs a certain number of btus to stay at a certain temperature.

Many systems have the water temperature set at around 180-190F. They deliver this heat in short bursts.

The boiler turns on, blasts out heat, then turns off. You get an on/off effect that really isn't steady. Your body feels this.

Lower water temperature can deliver that heat with longer cycles at lower temperatures. It's what radiant heating systems do. Only its using the system you already have. The fewer on/off cycles give a more steady heat and the cycles are easier on the equipment.
Got it, thanks! I'll check it out, and see how it works.

Now I guess I'll have to figure out how to check the temp and adjust it.
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
6,935
Schenectady, NY
On older boilers there's an aqua stat. On newer boilers you have to adjust the computer program.
 
  • Like
Reactions: Easy Livin’ 3000

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
On older boilers there's an aqua stat. On newer boilers you have to adjust the computer program.
IMG_20181108_180721988.jpg


Do you think there's a digital computer adjustment in there?

I'm guessing it's the grey box. No adjustment on the outside, so I'll have to take the screw out to peek inside.

Analog, with a few miles on it, just the way I like it.
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
6,935
Schenectady, NY
Lol. Probably not too much in the way of a computer there.
 

jeanw

Feeling the Heat
Sep 23, 2008
314
ky
is that stuff same thing as "double bubble" Hubby called it?was used. under the metal roof. I don't call it double bubble I call it single bubble. I bought some real "Reflective "alum barrier with aluminum with bubbles on both sides. Bought it at a big old hdwe store years ago to wrap water heater etc.s. Still some of both left. just a saying and asking. Thanks y'all.
Oh we were supposed to do thermal radiant floor under the floor beneath the joist.
even bought the outside propane unit. Unfortunately Hubby gave away the "Lifetime " nice water htr.it would have held the water. as a storage tank for the Propane unit
It has never been used yet Just hanging on the outside of this place.. At least it's not in the sun prob full of wasp and spiders . also got lots of books on the subject too...