in floor radiant heat- any first hand experience?

[goaliedad]

looking to install in floor radiant heat over an existing slab.

house built in late 60's. I assume no insulation under the slab. located in central/northern Michigan

currently heated with propane forced air heat- ducts in the attic. Furnace is from mid 1990, so I figure I will be replacing it soon anyway, plus the overhead heat is not very even.

I know about the foam panels to insulate the system and hold the pex lines. 

My questions are: is 2 inches of foam going to be enough of a thermal break? 

from what I have learned the pour over the lines/insulation only has to be about 5/16 inch over the top of the high points of the form. 
I am sure this is assuming some sort of finished floor will be installed. If we want to go with a polished concrete floor, what thickness would I be looking for?

In doing the remodel I have factored in raising the floor by 4 inches, so I have some room to work with.

Thoughts on heat source for the system? 

Any thoughts and input are welcome

[anwalt]

Now in Indiana.  Previously lived in Michigan, including 14 years 'above the bridge'.  

Built a garage addition in Indiana with radiant floor heat.  A nephew, Colorado resident, and an ME focused on structures for high end mountain housing remarked about my installing radiant that he does not like it because his feet sweat.  

The floor will be hot if the heat source is keeping up with a heat loss.  So, my guidance is to insulate well.  I have R20 in my walls, except the insulated 16ft garage door) R10 under the slab R50 above the ceiling.  I heat to 55oF.  

With radiant, sawdust is not blowing around the shop.

[TDKPE]

My in-laws have it in their summer house up here, built in 1961.  Slab floor throughout.

I don’t like it.  Takes too long to warm the house, and takes to long to stop warming the house.  Can’t use a programmable thermostat with the time it takes to feel a difference.  

Oh, and it’s leaking somewhere.  Don’t know where, but the water pressure will drop slowly if the supply valve is closed.

But that’s their system.  YMMV.

[blackhat]

I've installed dozens of them.  Without a heat loss calculation and a floor plan, I can't tell you if it is even feasible in your case.  More insulation below the heating layer means less heat loss to the ground, that's a good thing.  The higher the heat loss, the warmer the floor needs to be, that can be uncomfortable in extreme cases.

[jamesglenn]

I've installed dozens of them.  Without a heat loss calculation and a floor plan, I can't tell you if it is even feasible in your case.  More insulation below the heating layer means less heat loss to the ground, that's a good thing.  The higher the heat loss, the warmer the floor needs to be, that can be uncomfortable in extreme cases.

Exactly what Blackhat stated. Although I have not installed one, I have been involved in designing a lot. We use them for sidewalks, stairs and ramps on the exterior of our buildings which Owner's like because they use less salt and all that.

Anyway, another thing to consider is the concrete mix design, slab reinforcement and its positioning in respect to the radiant piping, even the concrete product being used. Mix design depends on the overall thickness as well as the minimum thickness at items encased within. Companies like Laticrete makes various products for numerous situations.

You also have to consider how much the grinding and polishing will remove in conjunction with the quality and how level the pour is.


Check out Uponor and maybe talk to someone there.

https://www.uponor-usa.com/?https://www....gJ0b_D_BwE

[measure once cut remeasure]

My in-laws have it in their summer house up here, built in 1961.  Slab floor throughout.

I don’t like it.  Takes too long to warm the house, and takes to long to stop warming the house.  Can’t use a programmable thermostat with the time it takes to feel a difference.  

Oh, and it’s leaking somewhere.  Don’t know where, but the water pressure will drop slowly if the supply valve is closed.

But that’s their system.  YMMV.

When I looked into radiant there were two schools of thought on insulating.  
1. Insulating provided a quicker warmup at the beginning of the heating season.  
2. Not insulating meant that you had to heat up the ground under the slab at the beginning of the heating season, but once heated it held the heat as a heat sink.  
In both cases insulating around the perimeter was recommended. 

I used R7 board under the whole slab.  

Radiant takes time to warm up and to cool down. Programable thermostats are not practical.  Beginning of heating season set the thermostat and leave it alone until spring.

Assuming the building is insulated, the floor should never be uncomfortably warm.

Radiant doesn't blow dust around, require duct work, or restricts where furniture can be placed.

Radiant requires a hard floor surface, carpet is out.

If the square footage isn't to big a high efficency hot water heater could be used as a heat source.  A hybrid water heater could be an option.  For a larger area a boiler. 


I average about 620 gallons of heating oil for a 2400 square foot house in upstate NY