Radiant Floor Heating Staple up gone wrong, subfloor radiant heating, boilers

Radiant Floor Heating Staple up gone wrong, subfloor radiant heating, boilers

Radiant Floor Heating /Staple up gone wrong

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Question

QUESTION: In new construction over a crawlspace, our plumber installed radiant heating under a 400 sf floor by stapling the tubes to the joist and not the subfloor. I don’t understand how this could result in efficient heat transfer to the floor.

Also, all pictures I see in heating & HVAC textbooks and mfr websites show tubing stapled to subfloor and often with aluminum plates to further ensure transfer to the floor, so I don’t understand how this can be best practice.

And finally, this looks like almost as much work as stapling to the subfloor, so I don’t see how it reduces the plumber’s cost.

In an earlier question from a homeowner getting poor results from such an installation, you recommend R13 insulation and airtight joist space when this installation is done over a heated space. Mine is over a crawlspace.

Will you please help me understand how this will work and if I need to ask for rework?

I’m in westchester county, NY, east coast USA, at a latitude of about 40dgrees and elevation (I’m guessing) of about 30-50 feet above sea level. The radiant installation was done today. Project is largeley complete.

thanks in advance!

vin

ANSWER: Stapling PEX tubing directly to a sub-floor can result in annoying ticking noises. ( I know, I did it in my own house!)

Hanging the tubing from the floor joists with plastic pipe hangers cured this for my very early staple up.

If you run tubing under a sub-floor; pump hot water through it; insulate to assure more heat goes up than down; you will warm the floor. As for heating the space to design temperature e.g. 70 degrees; the more resistance you have to heat transfer the more heat (hotter water) and heating surface (emission plates) you will need to transfer the energy needed to meet the heat lost in the room above.

Both staple-up and suspended tube radiant systems (which I assume from your description your plumber is attempting here) require elevated water temperatures and careful design. In temperate climates or rooms where the floor is not the primary heat source, these systems can be a bargain. Where they are expected to do the impossible, nightmares await.

I have admonished many guests to this site to look for a contractor who volunteers a heat load analysis for their proposed project. This is the only way to know what the outcome of a particular design will be. You might ask your plumber for his analysis before going any farther.

If the crawl space is not ventilated, (in most cold climates they shouldn’t be) I treat it as a conditioned space, but R-19 is the minimum insulation used for sub-floor radiant floors.

QUESTION: Thank you so much for your prompt and very helpful reply!

First, you are so right about doing homework and expecting a load analysis from the plumber. We didn’t do these things and are now feeling insecure and concerned.

Fact is, radiant was an add-on to a bigger project and we ended up just using the contractor’s plumber who charged us an additional $6500 to install the tubing, manifold, pump and stat, and didn’t do an analysis and is refusing to install the insulation or emission plates. He says to get foil backed insulation and everything will be fine.

But this floor IS the sole heat source for this cathedral ceiling barnlike 400sf room over a crawlspace. And here in New England, we have winter. So it sounds to me like we’re setting up for the «nightmare» you refer to!

So I guess the followup question is: Given the plumber’s insistance that this will work just fine with nothing more than foil-backed insulation, ie, he’s not doing anything else, what can I do myself to ensure success?

Should I re-staple his PEX with emission plates to the subfloor? Is there an emission plate that works with the installation he did? Is there a better radiant barrier/reflector than the foil on the back of the insulation?

We just want it to work.

Thanks for being there for us, and for so many people who write to this board.

ANSWER: I feel your pain. I too stapled up tubing in my brother’s house about 13 years ago. I did a heat load and concluded that the wood floor, sub-floor, carpet pad and carpet were too thick. Resisting the heat applied to the sub-floor using a direct stapleup method.

I admonished my brother to tighten up the house with new windows, doors and more insulation. He did put in a new door (double french).

Needless to say the system got behind in cold weather. To make matters worse using metal staples (like paper staples only bigger) to attach PEX tubing to the bottom of a wood floor will cause the floor to ‘tick’ on startup; most annoying.

The answer in my particular case was to add the supplemental heat that the heat load analysis suggested; which took the form of European steel panel radiators; splendid! In the mean time I have experimented with all the common sub-floor radiant heating systems and found them all wanting for performance. However well engineered, they simply have to operate at elevated water temperatures in order to be responsive to calls for heat and keep up with heat loads. I still design and install them, but it is some of my most challenging work.

To your situation then. I did staple up bubble foil (one of its few useful applications) over my stapleup in order to gain the increased surface area and enhance the radiant heat factor of the tube. Much speculation has been done on the radiant factor but not much scientific investigation. Conduction will give you the highest output potential and can be enhanced by putting the

the tube as close to the floor as possible, thus the extruded aluminum heat tranfer plates which increase the heated surface area and increase conductance substantially

Your plumber is thinking of convection. To enhance convected (hot air movement) output it is widely accepted that the tube be suspended more or less between the joists and two inches below the sub-floor. I have several systems installed with common plastic pipe hangers nailed to the floor joists.

Below all of these sub-floor systems insulation must be applied (typically an R19-3.5″ of fiberglass). An R value below the tubing equal to ten times the R value installed above is a very conservative number but in every case precludes the use of bubble foil as the exclusive insulator in all radiant floor jobs.

So lets start at the beginning and get a designer like myself to run a computor generated heat load analysis so we know what we need before we start trying to find it!

You are all very welcome.

on the joists

QUESTION: Thanks again, and if anybody asks me about radiant I will SHOUT at them to do their homework and seek out a person like YOU who would be contentious enough to actually plan the job and explain what’s going to be installed and how it’s going to work.

The attached picture shows what was installed and I don’t see how this could possibly be efficient. And now he tells me insulation isn’t included in his price.

I’m just going to order aluminum transfer plates and take care of it myself after I install the flooring (taking advantage of the hoses’ distance from the subfloor). As you can see from the picture, there’s enough tubing in the loop at the end that I should easily be able to do this, and also plenty of room for R38.

Now that I’m researching new boilers (did I mention that there’s suddenly water all over the floor dripping out of the furnace?), I’m realizing that running domestic through the radiant tubes using a separate indirect-fired heater with my oil furnace is probably about the best I can do with oil heat. Unfortunately, we’ve got non-potable Pex installed and even though I’m going to be rehanging it, I can’t bring myself to throw it out completely!

No need to reply (unless you see some red flags here!); just wanted to keep you apprised since you were so helpful!

Thanks again

vin

Answer

Natural gas if you can get it. We compete with the world for oil and should save it for cars in the short term.

As for potable water PEX: combination space heating and domestic hot water heating is not acceptable. When you buy your new boiler and indirect fired water heater you will be all set.

Lacking a heat load analysis, extruded aluminum heat emission plates such as those available Climate Trak from Viega, Rehau’s heavy transfer plates or Uponor’s Joist Track will give you the most output at the lowest operating temperature for sub-floor applications.

You are on the right path and I would like to say that I am disappointed in your «professional» as his conduct reflects poorly on the industry and truly dedicated professionals every where.

I tell all my customers: when it comes to comfort systems bypass the general contractor whenever possible. Contact a heating contractor personally and direct your general to work with your man. After all, it is your money and your comfort.

Radiant Floor Heating /Staple up gone wrong

Advertisement

Question

QUESTION: In new construction over a crawlspace, our plumber installed radiant heating under a 400 sf floor by stapling the tubes to the joist and not the subfloor. I don’t understand how this could result in efficient heat transfer to the floor.

Also, all pictures I see in heating & HVAC textbooks and mfr websites show tubing stapled to subfloor and often with aluminum plates to further ensure transfer to the floor, so I don’t understand how this can be best practice.

And finally, this looks like almost as much work as stapling to the subfloor, so I don’t see how it reduces the plumber’s cost.

In an earlier question from a homeowner getting poor results from such an installation, you recommend R13 insulation and airtight joist space when this installation is done over a heated space. Mine is over a crawlspace.

Will you please help me understand how this will work and if I need to ask for rework?

I’m in westchester county, NY, east coast USA, at a latitude of about 40dgrees and elevation (I’m guessing) of about 30-50 feet above sea level. The radiant installation was done today. Project is largeley complete.

thanks in advance!

vin

ANSWER: Stapling PEX tubing directly to a sub-floor can result in annoying ticking noises. ( I know, I did it in my own house!)

Hanging the tubing from the floor joists with plastic pipe hangers cured this for my very early staple up.

If you run tubing under a sub-floor; pump hot water through it; insulate to assure more heat goes up than down; you will warm the floor. As for heating the space to design temperature e.g. 70 degrees; the more resistance you have to heat transfer the more heat (hotter water) and heating surface (emission plates) you will need to transfer the energy needed to meet the heat lost in the room above.

Both staple-up and suspended tube radiant systems (which I assume from your description your plumber is attempting here) require elevated water temperatures and careful design. In temperate climates or rooms where the floor is not the primary heat source, these systems can be a bargain. Where they are expected to do the impossible, nightmares await.

I have admonished many guests to this site to look for a contractor who volunteers a heat load analysis for their proposed project. This is the only way to know what the outcome of a particular design will be. You might ask your plumber for his analysis before going any farther.

If the crawl space is not ventilated, (in most cold climates they shouldn’t be) I treat it as a conditioned space, but R-19 is the minimum insulation used for sub-floor radiant floors.

QUESTION: Thank you so much for your prompt and very helpful reply!

First, you are so right about doing homework and expecting a load analysis from the plumber. We didn’t do these things and are now feeling insecure and concerned.

Fact is, radiant was an add-on to a bigger project and we ended up just using the contractor’s plumber who charged us an additional $6500 to install the tubing, manifold, pump and stat, and didn’t do an analysis and is refusing to install the insulation or emission plates. He says to get foil backed insulation and everything will be fine.

But this floor IS the sole heat source for this cathedral ceiling barnlike 400sf room over a crawlspace. And here in New England, we have winter. So it sounds to me like we’re setting up for the «nightmare» you refer to!

So I guess the followup question is: Given the plumber’s insistance that this will work just fine with nothing more than foil-backed insulation, ie, he’s not doing anything else, what can I do myself to ensure success?

Should I re-staple his PEX with emission plates to the subfloor? Is there an emission plate that works with the installation he did? Is there a better radiant barrier/reflector than the foil on the back of the insulation?

We just want it to work.

Thanks for being there for us, and for so many people who write to this board.

ANSWER: I feel your pain. I too stapled up tubing in my brother’s house about 13 years ago. I did a heat load and concluded that the wood floor, sub-floor, carpet pad and carpet were too thick. Resisting the heat applied to the sub-floor using a direct stapleup method.

I admonished my brother to tighten up the house with new windows, doors and more insulation. He did put in a new door (double french).

Needless to say the system got behind in cold weather. To make matters worse using metal staples (like paper staples only bigger) to attach PEX tubing to the bottom of a wood floor will cause the floor to ‘tick’ on startup; most annoying.

The answer in my particular case was to add the supplemental heat that the heat load analysis suggested; which took the form of European steel panel radiators; splendid! In the mean time I have experimented with all the common sub-floor radiant heating systems and found them all wanting for performance. However well engineered, they simply have to operate at elevated water temperatures in order to be responsive to calls for heat and keep up with heat loads. I still design and install them, but it is some of my most challenging work.

To your situation then. I did staple up bubble foil (one of its few useful applications) over my stapleup in order to gain the increased surface area and enhance the radiant heat factor of the tube. Much speculation has been done on the radiant factor but not much scientific investigation. Conduction will give you the highest output potential and can be enhanced by putting the

the tube as close to the floor as possible, thus the extruded aluminum heat tranfer plates which increase the heated surface area and increase conductance substantially

Your plumber is thinking of convection. To enhance convected (hot air movement) output it is widely accepted that the tube be suspended more or less between the joists and two inches below the sub-floor. I have several systems installed with common plastic pipe hangers nailed to the floor joists.

Below all of these sub-floor systems insulation must be applied (typically an R19-3.5″ of fiberglass). An R value below the tubing equal to ten times the R value installed above is a very conservative number but in every case precludes the use of bubble foil as the exclusive insulator in all radiant floor jobs.

So lets start at the beginning and get a designer like myself to run a computor generated heat load analysis so we know what we need before we start trying to find it!

You are all very welcome.

on the joists

QUESTION: Thanks again, and if anybody asks me about radiant I will SHOUT at them to do their homework and seek out a person like YOU who would be contentious enough to actually plan the job and explain what’s going to be installed and how it’s going to work.

The attached picture shows what was installed and I don’t see how this could possibly be efficient. And now he tells me insulation isn’t included in his price.

I’m just going to order aluminum transfer plates and take care of it myself after I install the flooring (taking advantage of the hoses’ distance from the subfloor). As you can see from the picture, there’s enough tubing in the loop at the end that I should easily be able to do this, and also plenty of room for R38.

Now that I’m researching new boilers (did I mention that there’s suddenly water all over the floor dripping out of the furnace?), I’m realizing that running domestic through the radiant tubes using a separate indirect-fired heater with my oil furnace is probably about the best I can do with oil heat. Unfortunately, we’ve got non-potable Pex installed and even though I’m going to be rehanging it, I can’t bring myself to throw it out completely!

No need to reply (unless you see some red flags here!); just wanted to keep you apprised since you were so helpful!

Thanks again

vin

Answer

Natural gas if you can get it. We compete with the world for oil and should save it for cars in the short term.

As for potable water PEX: combination space heating and domestic hot water heating is not acceptable. When you buy your new boiler and indirect fired water heater you will be all set.

Lacking a heat load analysis, extruded aluminum heat emission plates such as those available Climate Trak from Viega, Rehau’s heavy transfer plates or Uponor’s Joist Track will give you the most output at the lowest operating temperature for sub-floor applications.

You are on the right path and I would like to say that I am disappointed in your «professional» as his conduct reflects poorly on the industry and truly dedicated professionals every where.

I tell all my customers: when it comes to comfort systems bypass the general contractor whenever possible. Contact a heating contractor personally and direct your general to work with your man. After all, it is your money and your comfort.


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