floating floor over radiant heat?

[tenaciousJay]

I am in the process of buying a house with radiant heat + fireplace inserts only - no air ducts at all. This seems to be a good idea as far as not having to work around ducts (my current house is lousy with them) but I want to double-check that I won't get into trouble building up over the radiant floor (will be done like the Silva Productions' floor - don't want to lose too much vertical space). My home inspector said that it wouldn't be a problem, it would just slow down the time to heat the room.

I do have the option of using the garage (2 car with extra space in back) if it is problematic but I'd rather leave that area free for cars, and also it has less isolation because the basement room is mostly underground on one side and the garage is mostly aboveground.

thanks,

Jay

[knightfly]

I don't see any reason that wouldn't work fine - one BIG difference - if your floor is radiant heated, you should NOT use any kind of vapor barrier. And, unless you'll be moving in 4-5 years, look for EPDM rubber of around 60 Duro instead of neoprene - longevity is 2-3 times as good as neoprene. Auralex U-boats are EPDM, one of the reasons they seem expensive.

You should still put rockwool or rigid fiberglass between the flat-laid joists though, floor resonance problems otherwise... Steve

[rod gervais]

I am in the process of buying a house with radiant heat + fireplace inserts only - no air ducts at all. This seems to be a good idea as far as not having to work around ducts (my current house is lousy with them) but I want to double-check that I won't get into trouble building up over the radiant floor (will be done like the Silva Productions' floor - don't want to lose too much vertical space). My home inspector said that it wouldn't be a problem, it would just slow down the time to heat the room.

Your home inspector doesn't have a clue........ constructing a floor over this will do a lot more than that "Just slow down the time to heat the room)

Underfloor (or underslab) systems are designed specifically for the floor covering above.

If someone has insight they may look at possibilities for the future - such as sizing for a wood floor today - but allowing for the added insulation for adding carpet down the road.

But the material above the floor is an intergal part of the design of these systems. For example - a system designed to provide heat (specifically) for a ceramic tile floor will not produce enough btu's to heat the same space with padding and carpet. This is not a guess on my part - this is a fact. I have specified and designed these systems in the past.

In your case - adding a floated floor above - will delay the time that the systems takes to bring the new upper deck assembly to termperature from the time that the thermostat calls for heat.

The system has piping sized - with a particular water temperature - to overcome the thermal resistance of the existing floor and covering, and as you introduce additional coverings above that surface - you lose heat during the transfer process. The only way to overcome the additional losses are to increase the BTU output of the system.

You do this by increasing the water temperature (assuming that the system design is not already at the maximum temperature of the system) and (or) increasing flow to maintain water temperatures.

Once again - if the piping is sized larger than it needs to be, this may be possible - and you will just live with the additional costs associated with heating that area due to the loss of thermal radiation through the additional layers.......... but if it is NOT SIZED larg enough - you cannot possibly produce enought BTU output to over come the additional losses.

Heating the interior of a building is very much like sound isolation.

The more I put in the way of a sound - the more i block it's passage through a wall.

The more i put in the way of my heat source - the more i block it's passage into the space that needs it.

Tis simple to understand - not quite as simple to implement.

Good luck,

Rod

[tenaciousJay]

Thanks Rod. I had similar thoughts which is why I'm asking here. The garage is not ideal but would be workable it it's going to be a big problem.

Tell me if my thinking is flawed here (and it probably is) but if the new floor above is insulated (with no vapor barrier - water isn't a problem here anyway), won't that trap some heat under the floor, so the pipes will not shed as much heat as they would for a large open room? In effect, aren't I insulating the slab and keeping it warm in that area?

And if the room above is heated through some secondary method - ventilation to the room next door with a fireplace or even a space heater (not to mention tube amps), won't that also slow the heat loss from the slab?

I appreciate your comments and experience Rod, hope I'm not coming off as argumentative, I just want to understand the effect on the system as much as possible. I suppose I'll need to bring in an expert to look at my boiler in any case; I've got the name of the best local guy.

[rod gervais]

Thanks Rod. I had similar thoughts which is why I'm asking here. The garage is not ideal but would be workable it it's going to be a big problem.

Tell me if my thinking is flawed here (and it probably is) but if the new floor above is insulated (with no vapor barrier - water isn't a problem here anyway), won't that trap some heat under the floor, so the pipes will not shed as much heat as they would for a large open room? In effect, aren't I insulating the slab and keeping it warm in that area?

I must be dense here......... because I don't get this at all. The issue is not the keeping of the slab warm........... it's getting the heat from the slab into the room.

What do you gain by locking the heat in the slab?

By this do you mean that it won't expend as much energy if the slab stays warm?........... if that's what you mean the answer is no - because the slab temperature has nothing to do with the room temperature........

Suppose I can raise the room temperature (in 5 minutes) 3 degrees with the design you have and 30 degree outside air temperatures.

Now I insulate above the slab - and if i run the system it takes me 3 hours to raise the temp 3 degrees in 30 degree outside air....... did i just save money because my return loop temperature is one or 2 degrees higher than normal?.

Nope - the bottom line is that it will take more BTU output to get heat into the space (although i can pretty much promise you that it won't be possible the way it's designed.) And anyway you look at it - more BTU is more money.

And if the room above is heated through some secondary method - ventilation to the room next door with a fireplace or even a space heater (not to mention tube amps), won't that also slow the heat loss from the slab?

Once again - i don't understand what your mind is picturing - what do you mean by "slow the heat loss from the slab" ?????????? Generating (paying for) heat that you CAN NOT use is (In my mind - but then again I might be crazy) just plain silly.

Maybe it's possible for you to unhook the loop for that area and then reinstall a new loop where it belongs - which is either ontop of (best location) or just directly below (the only 2nd choice) the deck of your newly build elevated isolated floor.

Then if you ever wanted to rip it out you could just reconnect the old PEX tubing.

By the way - what's wrong with your boiler that you need someone to check it out?

Rod

[tenaciousJay]

I'm very sorry I'm not being more clear about this.

My main questions are in order of importance:

1. (Most important) Will building up over a radiant heat floor damage the heating system in any way? Overload the capacity of the boiler? Cause giant tidal waves to crash into New York?

2. Will affect the heating of the rest of the house?

3. Can it also heat the studio area?

4. (Least important) Will I be losing heating efficiency, paying extra $ for heating? (becomes more and more important the more money I'm wasting)

Thanks Rod. I had similar thoughts which is why I'm asking here. The garage is not ideal but would be workable it it's going to be a big problem.

Tell me if my thinking is flawed here (and it probably is) but if the new floor above is insulated (with no vapor barrier - water isn't a problem here anyway), won't that trap some heat under the floor, so the pipes will not shed as much heat as they would for a large open room? In effect, aren't I insulating the slab and keeping it warm in that area?

I must be dense here......... because I don't get this at all. The issue is not the keeping of the slab warm........... it's getting the heat from the slab into the room.

Don't worry, I'm pretty sure I'm the dense one here
If the slab is warm, it heats the rest of the basement even if it's not getting into the studio rooms (question #2). I would also think that it wouldn't tax the boiler; the water would just return through the loop hotter than it would've if it had a cold room to shed the heat to (question #1).

What do you gain by locking the heat in the slab?

By this do you mean that it won't expend as much energy if the slab stays warm?........... if that's what you mean the answer is no - because the slab temperature has nothing to do with the room temperature........

OK, you lost me there with that last sentence, Rod. Are you talking about the studio rooms in particular or the whole house? Because it seems to me that the slab temperature and the room temperature are directly related.

Suppose I can raise the room temperature (in 5 minutes) 3 degrees with the design you have and 30 degree outside air temperatures.

Now I insulate above the slab - and if i run the system it takes me 3 hours to raise the temp 3 degrees in 30 degree outside air....... did i just save money because my return loop temperature is one or 2 degrees higher than normal?.

I think so, or at least not losing money (question #4), because that hotter water will get combined with the other water and re-circulated around the basement (possibly the whole house), heating the areas that aren't built over. So that is heat that doesn't need to be generated.

Nope - the bottom line is that it will take more BTU output to get heat into the space (although i can pretty much promise you that it won't be possible the way it's designed.) And anyway you look at it - more BTU is more money.

So if it's not possible (question #3) to heat the studio from underneath this way, then the heat will still permeate the entire slab and warm the rest of the basement (and somewhat rise to the upstairs as well), right? And any hot water still gets circulated to the rest of the basement. And as long as the thermostat isn't in the studio it won't keep trying to heat an area that is cooler than the rest of the basement.

And if the room above is heated through some secondary method - ventilation to the room next door with a fireplace or even a space heater (not to mention tube amps), won't that also slow the heat loss from the slab?

Once again - i don't understand what your mind is picturing - what do you mean by "slow the heat loss from the slab" ?????????? Generating (paying for) heat that you CAN NOT use is (In my mind - but then again I might be crazy) just plain silly.

But that heat will still be used in the rest of the basement I think (see above answer). Maybe there will be some waste but in my mind in won't be significant; it's not like I'm running the pipe outside where it heats nothing and the water comes back around cold.

Maybe it's possible for you to unhook the loop for that area and then reinstall a new loop where it belongs - which is either ontop of (best location) or just directly below (the only 2nd choice) the deck of your newly build elevated isolated floor.

Then if you ever wanted to rip it out you could just reconnect the old PEX tubing.

By the way - what's wrong with your boiler that you need someone to check it out?

Rod

The pipes are embedded in the concrete slab; I don't think I want to try to move them.

I figured the boiler/radiant heat dude (supposedly the expert around here) would be able to tell me if I would be putting too much of a load on my system (question #1) and give me more info than my inspector because he deals with this stuff all the time.

Once again thanks for your time Rod.

Jay

[rod gervais]

1. (Most important) Will building up over a radiant heat floor damage the heating system in any way? Overload the capacity of the boiler? Cause giant tidal waves to crash into New York?

Jay,

Building up over this will not cause any overload or damage to the system.

2. Will affect the heating of the rest of the house?

No it will not.

3. Can it also heat the studio area?

No - if you cover it over the way you have discussed it will not be able to heat the studio - it won't work through an additional deck assembly.

4. (Least important) Will I be losing heating efficiency, paying extra $ for heating? (becomes more and more important the more money I'm wasting)

Yes - and i will explain that below.

If the slab is warm, it heats the rest of the basement even if it's not getting into the studio rooms (question #2). I would also think that it wouldn't tax the boiler; the water would just return through the loop hotter than it would've if it had a cold room to shed the heat to (question #1).

Nope - this is why it will cost you more money.

The entire area will just waste heat - it won't travel to the outlying areas - this because to do so it would have to change the laws of physics.

Heat doesn't travel to colder areas - it is cold that invades heat......... That's why ice cubes freeze from the outside in - and human beings the same way.

So there is no way for this heated slab to spread out that energy in order to heat the surrounding cooler slab. (the surrounding slabds are cooler because they immeadiately lose heat through radiation - they aren't covered by anything keeping the warm longer).

If you trap the heat by constructing the isolated floor - all you will do is make the ground under the slab a little warmer a little deeper than normal (and that only for a very short time - see below for more info on how the system works with higher than expected return water temps) - but ALL OF THE ENERGY SPENT TO HEAT THE SLAB BELOW THE FLOOR WILL BE WASTED ENERGY. And then - you will still have to spend the money again - in one form or another - to heat the space above that deck area - and thus - your energy costs will have to rise.

I think so, or at least not losing money (question #4), because that hotter water will get combined with the other water and re-circulated around the basement (possibly the whole house), heating the areas that aren't built over. So that is heat that doesn't need to be generated.

Nope - that is heat that has ALREADY BEEN GENERATED THAT IS LOST IN THE GROUND - THE REMAINDER OF THE HOUSE GAINS NO BENEFIT FROM IT.

So if it's not possible (question #3) to heat the studio from underneath this way, then the heat will still permeate the entire slab and warm the rest of the basement (and somewhat rise to the upstairs as well), right? And any hot water still gets circulated to the rest of the basement. And as long as the thermostat isn't in the studio it won't keep trying to heat an area that is cooler than the rest of the basement.

Again - refer to the answer above - what is lost under the new floor is lost - it will contribute to nothing. And if it is on the same loop as the rest of the basement and thus raises the return temp of the water - that will only make the automatic mixing valve - which wants the water temp to be a constant set degree - sensing it's higher - to add return water to the mix in order to lower the water temperature which will (in turn) cause the remaining area to heat more slowly,,,,, these systems are very tricky.

And if the room above is heated through some secondary method - ventilation to the room next door with a fireplace or even a space heater (not to mention tube amps), won't that also slow the heat loss from the slab?

Nope - not in the least............. the room above - once you finish the isolation you require for this - will never come into play for this room.

But that heat will still be used in the rest of the basement I think (see above answer). Maybe there will be some waste but in my mind in won't be significant; it's not like I'm running the pipe outside where it heats nothing and the water comes back around cold.

Not outside where it heats nothing - rather - inside where it heats nothing.

Nothing is nothing - no matter where it's located.

The pipes are embedded in the concrete slab; I don't think I want to try to move them.

I am not talking about moving them. Before they enter the slab they are connected to a small manifold - and if you disconnect them from that - you could install a new loop for your elevated deck. They aren't removed - just temporarily abandoned in place.

Understand that with these systems each loop handles a relatively small area - and you can possible isolate the area under your new floor - and if you then install new piping in that new floor - your heating costs would then go down.

This because the amount of heat required to maintain your studio will be less (due to the super insulating value of the isolated construction).

I figured the boiler/radiant heat dude (supposedly the expert around here) would be able to tell me if I would be putting too much of a load on my system (question #1) and give me more info than my inspector because he deals with this stuff all the time.

You can't put any more load on your system unless you expand the heating area with the system. Covering up the system does not increase the load - it simply creates wasted energy due to that which doesn't heat the house.

Rod

[tenaciousJay]

Thanks Rod, I understand now.

For some reason I wasn't thinking that the earth under the slab got heated as well; I was just thinking it heated up and out. doh!

So my options are to:
- build over as is, and see little or no heat in the studio for the energy expended for that area of the floor, or:
- figure out which zone(s) cover that area, disconnect them and connect a new set of pipes that will be properly placed just below the (new) studio floor.

The only other question I have is if the new set of pipes would transmit noise through the house. They have to be above the insulation, right? It seems like sound would travel pretty well through the metal pipes (and the water in them I suppose), which would be a problem.

Actually I also wonder if I have the room for a new set of pipes with the floor slats laid flat (got to do it that way - ceiling is 7'2", drummer is 6'5").

Once again I appreciate your patience. And sorry for the delay, we're incredibly busy trying to prep our current house for sale now that we've bought our new place.

Jay

[rod gervais]

The only other question I have is if the new set of pipes would transmit noise through the house. They have to be above the insulation, right? It seems like sound would travel pretty well through the metal pipes (and the water in them I suppose), which would be a problem.

Jay,

Actually - this type of system is done with PEX tubing (cross linked plastic tubing) and not copper pipes.

Copper is a poor choice for this due to the fact that there are serious problems with it relating to oxygen diffusion. Copper pipe deteriorates quckly with a system like this - and would be a big problem with concrete surround.

The PEX is also a very quiet system.

Actually I also wonder if I have the room for a new set of pipes with the floor slats laid flat (got to do it that way - ceiling is 7'2", drummer is 6'5").

Actually - this system is pretty cool based on it's options. One of which is installation above the wood deck. It's done with a series of premanufactured panels that lock in the tubing. Although if you purchase just a few of these - you can make your own fairly inexpensively with standard particle board. You then just install your floor covering over that.

So with a 3/8" ID tubing and 3/4" wood flooring - you would only lose an additional 1 1/4" of ceiling height.


Rod