DIY Hydronic Floor Heating

[Vlad]

Originally Posted by Exeric

You are comparing apples to oranges. If you use staple up you must extensively insulate from below. Perhaps you did and just failed to mention it. There seems to be some confusion about this whole subject. If you mount pex from below without a heat spreader you won't have good heat conductivity to the floor. That's just physics. However, you can get away with it if the ratio of R value below to R above is high enough.

Heat doesn't just disappear because you have insulation from layers of subfloor above the pex. It has to go some where. If one has no insulation below it will just go down because the ratio of R value above and below isn't good. It will twke the easiest escape route. But even without a heat spreader if you increase the ratio high enough of R value below to that above it will still work well. But it might work more like a concrete floor in that it will take a long time for that heat to work through the upper layer(s) of flooring.

I myself would go for pex mounting below with a heat spreader so I wouldn't have to wait so long. If you didn't heavily insulate below without a spreader then that was probably a mistake.

"Heat doesn't just disappear because you have insulation from layers of subfloor above the pex. It has to go some where."

It can go back to pump leaving your place cold.

Also randen mentioned water temperature @ 100F this might be not enough for staple up. Increasing water temperature to 120-130 would change the game but using HP and water hotter then 100F is not going to be very efficient....

[AC_Hacker]

I have been looking into various heat spreader plate products and I was looking at an installation instruction sheet on this product:

I am including some text below, from the installation instructions, because it is in keeping with all of the informed theory I have come across, and also the experience of users who have lived with their hydronic installations, like Vlad and randen...

• Radiant Engineering does not recommend “staple-up” type systems. This method involves stapling the tubing directly to the sub-floor from below or suspending the tubing in the joist bay. These types of systems have a dramatically reduced output even at high water temperatures. The maximum output that these systems can achieve is generally 10-15 BTU/hr per sq. ft. at 180°-200°F. It would take approximately three times the amount of staple-up tubing to match the output of the tubing in the ThermoFin™.
• Additionally, the installers should be aware that floor coverings within a structure have a profound impact on the output of radiant floor heat. Carpeting (high Rvalue) will yield much lower BTU’s per square foot than tile (low R-value) under the same conditions.

It's interesting to note that the HDD for the area that the heat spreader product (shown above) is manufactured (and the installation instructions were written) is Bozeman, Montana, where the HDD = 9117.

* * *

Also, as a way to help this discussion, it would be very useful if each of us went to THIS URL and got a calculated average value of your heating degree days for the area you live in.

I think it would go a long way to clarify the heating problems each of us are facing.

When I ran the calculation, with a base temp of 68 degrees F (that's what I keep my house at in the winter), my average comes out to 5751 heating degree days.

[* AC_Hacker = Portland, Oregon, USA... Average Heating Degree Days = 5751, based on 68 degree F base temperature. *]

* * *

Also people seem to get hung up on the "radiant" thing when they're attempting to visualize how hydronic heating works...

So it might be good to remember that there are three modes of heat transfer simultaneously taking place in a hydronic system:

• radiation
• conduction
• convection

If you have held your hand near the side of a hot stove burner, you have experienced radiation, if you hold your hand above the stove burner, you have experienced convection, and if you place your hand directly on the stove burner, you have experienced conduction... and you should know at least a little bit about the efficiency of each heating mode.

* * *

On a totally different track, I acme across a radiant heating blog entry recently where some general contractors were discussing the problem of radiant floors working fine to keep a house warm, but never achieving the warm floor feeling that people expect in a radiant floor (not stated, it was because the insulation standards are getting higher, and the temp level of the floor doesn't need to be so high to keep a house comfortable).

The solution was to reduce the radiant heated area to just the part of the house where people would gather to spend quality time, like in the living room where the little ones could happily grovel about on the floor.

From the standpoint of fulfilling the radiant floor dream, it sounds great, but from an efficiency standpoint, it just makes me cringe.

Best,

-AC

[randen]

confession located by AC Hacker:
I've starred in the movie- I'm ripping out the thin plates under my lossy family room and am replacing them with extrusions to be able to keep up at design-condition, rather than boost the water temp above condensing range just for one room.

He may have been mis-lead as well. My supplier said oh just nail it up underneath about a ft apart and you'll be toasty warm. Hmm. Free advise is allways worth what you paid for it. However it made my education a lot of work and money to replace the non-functioning system. Looking at some of the suppiers still supporting the staple up augmented by plates I question the performances. Maybe we need to look at it like a old carbarated engine verses fuel injection. Uponor and warm board being newer and maybe a lot more effecient. Who here wouldn't like 50 mpg.

Randen

[AC_Hacker]

Originally Posted by randen

My supplier said oh just nail it up underneath about a ft apart and you'll be toasty warm. Hmm. Free advise is allways worth what you paid for it. However it made my education a lot of work and money to replace the non-functioning system. Looking at some of the suppiers still supporting the staple up augmented by plates I question the performances. Maybe we need to look at it like a old carbarated engine verses fuel injection. Uponor and warm board being newer and maybe a lot more effecient. Who here wouldn't like 50 mpg.

randen,

[* randen = Strathroy, Ontario, Canada... Average Heating Degree Days = 8002, based on 68 degree F base temperature. *]

You're absolutely right, we all want 50 mpg.

It might be useful if you shared a little more of your hydronic heating story...

Maybe a bit about your house, heated floor area, it's insulation (attic, walls, floor), windows, etc. and what you tried that didn't work and what you have come up with that does work (including tubing spacing, plates, floor coverings. etc.). Are you able to use any solar to heat your house? As I recall you have a commercially installed heat pump for your house, right? Is it ASHP or GSHP? Is it heating air or hydronic?

Best,

-AC

[randen]

AC Hacker Wrote:

It might be useful if you shared a little more of your hydronic heating story...

Maybe a bit about your house, heated floor area, it's insulation (attic, walls, floor), windows, etc. and what you tried that didn't work and what you have come up with that does work (including tubing spacing, plates, floor coverings. etc.). Are you able to use any solar to heat your house? As I recall you have a commercially installed heat pump for your house, right? Is it ASHP or GSHP? Is it heating air or hydronic?

Very soon I will do a little artical that may help someone else on their quest for the free heat. Yes the house is heated with solar and the back-up is Geo-Thermal. The goal was half the space heating load with solar. I would say we are pretty much there. Of cource it depends on the season. We added some more panel area and during peak heat some of the heat energy is returning to the panels in otherwords my heat-exchanger isn't big enough. Its on my to-do list this fall. Its odd to think of justifying the cost of a larger plate type heat exchanger that will be more than half the cost of a years heat.!!

If anyone is considering slab infloor heat you can't beat it for comfort. In an artical above contractors were saying the floor may be effective even if you don't feel the floor warm. (was the job done correctly??) Here in the winter with wind and cold weather -22 Deg C. we have the floor at about 32 Deg C which is warm for the feet and the inside air temp 23 deg C. Maybe a little high floor temp but the room is 17' with lots of glass. During most time the floor temp is 24-28 Deg C. and you still have warm feet. I don't know what the contractors are talking about.

1. Solar will work
2. Insulate beyond well
3. In-floor is the cadilac

Randen

[Vlad]

Originally Posted by randen

confession located by AC Hacker:
I've starred in the movie- I'm ripping out the thin plates under my lossy family room and am replacing them with extrusions to be able to keep up at design-condition, rather than boost the water temp above condensing range just for one room.

He may have been mis-lead as well. My supplier said oh just nail it up underneath about a ft apart and you'll be toasty warm. Hmm. Free advise is allways worth what you paid for it. However it made my education a lot of work and money to replace the non-functioning system. Looking at some of the suppiers still supporting the staple up augmented by plates I question the performances. Maybe we need to look at it like a old carbarated engine verses fuel injection. Uponor and warm board being newer and maybe a lot more effecient. Who here wouldn't like 50 mpg.

Randen

What about your ventilation system? Do you have any? The problem with radiant floor heating is you still have to bring fresh air because there is no air circulation.

This was the main reason for me making ground loop. When outside is colder then inside (most of the time of the year in BC Canada) you have to heat up fresh outside air before you push it inside.

In your case if for whatever reason part of the house is still cold even you maxed up circulation and temperature (in your case 100F) you can compensate this temperature loss by adding more warm air to this area (or heat it up more).

[AC_Hacker]

Originally Posted by randen

In an artical above contractors were saying the floor may be effective even if you don't feel the floor warm. (was the job done correctly??) Here in the winter with wind and cold weather -22 Deg C. we have the floor at about 32 Deg C which is warm for the feet and the inside air temp 23 deg C. Maybe a little high floor temp but the room is 17' with lots of glass. During most time the floor temp is 24-28 Deg C. and you still have warm feet. I don't know what the contractors are talking about.

randen,

HERE is an article that addresses this issue in detail. It has to do with a very high performance house and also how the body perceives warmth, it is all well covered in the article.

Vlad has also reported that his house was warm and comfortable during the coldest periods of the season, but the floors didn't actually feel warm to the touch.

I've been to visit Vlad, and he has tight 6" walls filled with mineral wool, double pane throughout the house, R-50 roof, and he has done the most amazing job of sealing against infiltration I have ever seen. His floors are above sub-floor construction, and only require 95 degree water to keep his house warm.

His HDD is about 6489, your is about 8002... that could be part of the story, too.

Best,

-AC

[randen]

Vlad wrote:
What about your ventilation system? Do you have any? The problem with radiant floor heating is you still have to bring fresh air because there is no air circulation.

Yes my home is air infiltration tight 1.9 ACH @ 50 kpa and we do have a air exchange unit 2 speed. This is a whole home system that has designated ducts which exchange areas were moisture and or services need to be intensified such as the bathroom. We have a smart home system which by way of occupant sensing, say in the bathroom, turns the exchange unit to high speed exchanging the air to fresh quickly and after a set time returns to a slow speed constant.
One little problem during the really cold weather. The unit can become over whelmed. The incoming air is extremely cold and the heatexchanger cannot warm the the air coming in enough and the living areas start to cool. During these days we turn it off.

We have about 2000 sft. of heated concrete floor thats performance has been stellar. We sense the temp of the floor with cheapy electronic thermastats (for each zone) that I have removed the thermister and placed in in a shallow hole drilled in the concrete floor between the tubes. The tubing avalible to us was Kitec 5/8" ID. placed 1 ft apart. The floor is 6" thick with 2" of high density foam beneth. Around the edge and inside the foundation is 1 foam.

The heated concrete floors short-coming/advantage is the time it takes to react. Pumping warm water thru at 42 deg C (Geo-Thermal upper limit) takes about 4 hrs to raise 1-2 deg C. The up-side thats alot of stored heat. With the solar heated water since its a little hotter most times it heats marginally faster. The stored heat in the concrete is the reason solar heating is highly effective for space heating. The sun essentionally warms a big rock all day to release that heat into the living space all night to hopfully be recharged the next day.

If I was to construct again I would place solar heat loop in the floor 6" from the heat pump floor loop. The second loop would be for solar hot water only and this would eliminate the losses associated in heat exchangers. It would be better if the heated glycol/water would give its heat energy directly to the concrete battery.

The compatibility of the solar hot water and heated concrete floor is amazingly great. The ROI on the extra cost of a solar installation is maybe a little clouded, but as mentioned before as the cost of energy goes up and we chase the mode of heating being fuel oil to natural gas to electrical as the cost of energy favours one over the other. Solar harvesting will always be FREE.

Randen

[berniebenz]

Originally Posted by randen

Yes my home is air infiltration tight 1.9 ACH @ 50 kpa and we do have a air exchange unit 2 speed. This is a whole home system that has designated ducts which exchange areas were moisture and or services need to be intensified such as the bathroom. We have a smart home system which by way of occupant sensing, say in the bathroom, turns the exchange unit to high speed exchanging the air to fresh quickly and after a set time returns to a slow speed constant.
One little problem during the really cold weather. The unit can become over whelmed. The incoming air is extremely cold and the heatexchanger cannot warm the the air coming in enough and the living areas start to cool. During these days we turn it off.
Randen

I also have a tight 2000sf home also having a small air exchange unit for the same purpose, single speed manual on/off and seldom used as not needed for moisture control in Nevada’s dry air. (Not big farters either!)

Originally Posted by randen

We have about 2000 sft. of heated concrete floor thats performance has been stellar. We sense the temp of the floor with cheapy electronic thermastats (for each zone) that I have removed the thermister and placed in in a shallow hole drilled in the concrete floor between the tubes. The tubing avalible to us was Kitec 5/8" ID. placed 1 ft apart. The floor is 6" thick with 2" of high density foam beneth. Around the edge and inside the foundation is 1 foam.
Randen

My 15 year old single story radiant floor is divided into two zones, carpeted bedrooms and the rest bare limestone tile, for obvious reasons. The floor uses approx. 200’ lengths of ⅜”ID PB tubing on 6” centers stapled to ¾” ply sub floor over crawl space, covered with 1¾” self leveling poured gypcrete. No additional heat dispersion, floor coverings are laid directly on the gypcrete surface.

I use conventional air thermostats 5’ off the floor one for each of the 2 zones controlling the on/off zone circ pumps. Thus, slab temperature is what ever is required to achieve the comfort air temp of 68 to 70 deg, limited by the capacity of an internal HX in the propane fired condensing DHWH. (Soon to be supplemented with an A7 airtap thru an external HX.) During the coldest subzero periods I increase the DHW from 120 to 135deg.

Originally Posted by randen

The heated concrete floors short-coming/advantage is the time it takes to react. Pumping warm water thru at 42 deg C (Geo-Thermal upper limit) takes about 4 hrs to raise 1-2 deg C. The up-side thats alot of stored heat. With the solar heated water since its a little hotter most times it heats marginally faster. The stored heat in the concrete is the reason solar heating is highly effective for space heating. The sun essentionally warms a big rock all day to release that heat into the living space all night to hopfully be recharged the next day.
Randen

Thus, the system runs at constant air temp, shutting down on mild days with solar gain thru large window area. We never adjust the thermostats during the heating season unless leaving for several days. Takes over nite to warm up from 55deg. If I were 20 years younger than my 83, I’d add a dual source HPWH and eliminate the propane.

[Vlad]

Originally Posted by randen

Vlad wrote:
What about your ventilation system? Do you have any? The problem with radiant floor heating is you still have to bring fresh air because there is no air circulation.

Yes my home is air infiltration tight 1.9 ACH @ 50 kpa and we do have a air exchange unit 2 speed. This is a whole home system that has designated ducts which exchange areas were moisture and or services need to be intensified such as the bathroom. We have a smart home system which by way of occupant sensing, say in the bathroom, turns the exchange unit to high speed exchanging the air to fresh quickly and after a set time returns to a slow speed constant.
One little problem during the really cold weather. The unit can become over whelmed. The incoming air is extremely cold and the heatexchanger cannot warm the the air coming in enough and the living areas start to cool. During these days we turn it off.

But there is one more question. You do have a very sophisticated exhaust system with recovery benefits, but do you have an air delivery system distributing air in every room?