DIY hydronic heating installation

[opiesche]

Hi all,

I've used this and other sites to get a lot of information before attempting my hydronic radiant (in-floor) installation, so I figured I'd give some back by making some information about the process, pitfalls, things that worked and didn't work, etc., available to others. I've started a blog on which I'll post about the process, including pictures, materials, etc.
What's currently on there is still very general, so bear with me as I dig through the hundreds of pictures taken during the installation, and post more. I should get around to providing a lot of info and tips over the next few days.

The Piesche family's home improvement adventures

Thanks,
Olaf

[AC_Hacker]

Originally Posted by opiesche

...so I figured I'd give some back by making some information about the process, pitfalls, things that worked and didn't work, etc., available to others...

Olaf,

Thanks for joining in the DIY party!

I'm about to do a small radiant project myself, starting real soon, so any info you offer will be extremely useful to me.

I'm about to start shopping for materials...

Best,

-AC_Hacker

[opiesche]

Good to hear! If you have any questions, feel free to ask here or on the blog, I'll do my best to help. There are a couple of potential pitfalls (nothing too scary) with the tubing I hope to get to post about tonight.

A couple of things to know before buying the materials:

-If you're looking at doing it the same way we did, just make sure the OSB/Plywood is thick enough to support the tubing and plates - 19/32 worked for us for 1/2" PEX tubing, but it might depend on the transfer plates. I ordered the plates first, then measured the depth of the groove in the plate with a slide rule, then decided on the carrier OSB.

-It may be a good idea to make a rough plan for how many loops are going where (see the 'Materials Calculation' post on my blog) on paper or whiteboard, so you know the length of the individual loops - this will help in getting the right length rolls of tubing and to minimize waste in both tubing and OSB

Good luck with your project - it's a chunk of work, but definitely worth it once the floors are nice and toasty

[natethebrown]

I am still a number of years away from building my dream house, so I am still deciding what type of conditioning systems I want to use. With that being said, I really enjoy getting inspired from seeing these type of projects.

[opiesche]

Originally Posted by natethebrown

I am still a number of years away from building my dream house, so I am still deciding what type of conditioning systems I want to use. With that being said, I really enjoy getting inspired from seeing these type of projects.

Glad to hear others are interested. As far as heating goes, there's not much that beats heated floors in terms of comfort and efficiency - I'm looking forward to mine in the winter!

[AC_Hacker]

I'm reading through your blog about your hydronic install...

How would you describe the length & severity of your heating season? Average information is important, but also the extremes that you have seen since you have lived in your house.

Does this average temperature chart seem to reflect your experience:

average temperature - Rohnert Park, CA

I also looked up your average Heating Degree Days for Rohnert Park, CA and the 5 year average, assuming that your base heating level is 65F, calculates out to 4172 heating degree days. This doesn't make any difference to you, but it might if someone was installing their own system, they could find out what the HDD was for their locale and compare it to your HDD and would have a rough idea if your design would work for them, too.

From what you have said so far, I assume that your house is built on a slab that has no insulation underneath, correct?

Regarding insulation, you said that your house was pretty well insulated...

• What exactly do you mean by that?
• Did you do the insulation yourself?
• What is the thickness of your outside walls?
• What kind of filling is in them?
• Do you have single pane/double pane/triple pane windows?
• Aluminum window sashes?
• Vinyl sashes?
• Wood sashes?
• Did you do any kind of a heat load analysis (similar to Manual-J)?
• Have you done a blower door test on your house?

In reading your blog, I saw that you didn't do any insulation UNDER your floor... and that you chose a thin foam underlayment to go OVER your floor, under your final flooring... Any thoughts on that?

I don't know if you looked at Vlad's hydronic install yet, but he built his own house (6" walls filled with mineral wool, 2x pane windows, highly effective infiltration prevention) and he did a similar install to yours, with just a few differences. His house is three stories tall, so it is somewhat more of a cube than your single level house (ranch I would assume). Since his 'cube-ish' would have lower surface area per unit volume, it would favor lower heat loss, too. Anyway his water feed temperatures are running about 95F to 100F, as I recall, which is astoundingly good, especially considering that he lives just outside Vancouver, Canada where his average HDD is about 5481 which is a fair bit higher than yours.

By the way, you haven't gone into any detail as to how you plan to get the heat into the water... and how you plan on regulating temperature/

I will be very interested to see how your system performs as winter comes to visit us. Please keep us posted!

Good work, Olaf... it's a big job that should last the rest of your life.

Best,

-AC_Hacker

[opiesche]

All good questions! I'll need to collate some of the info and add it to my blog

Our house was built in 1984 on a crawlspace with posts in concrete. I'ts a two story with four betrooms and two baths upstairs. Underneath is packed dirt. When I said the house is pretty well insulated, I meant 6" exterior walls with fiberglass roll insulation. I didn't do it myself, but have opened some of the walls (to run new power outlets), and that's what I've found in two of the exterior walls. The windows are relatively new (late 90s or so), and are double pane vinyl. The attic is insulated with about 6" of loose fill fiberglass (something I plan to augment with additional batts in the future).

We didn't do a full heating load analysis - our estimate came from the fact that my parents' house sees temperatures at least 35 degrees below what we experience in winter. They've got double the density of heating loops, and similar insulation, and about the same water temperature (they have in-slab loops over a basement though). So we figured that half the density would work fine for us with the relatively mild temperatures we're seeing.
Your information about average temperatures seems roughly correct. There's a couple of weeks or so when the temps occasionally drop below 30 for a few hours (between 3 and 5am), but that's the worst we see.

We've never done a blower test, but the house seems reasonably infiltration proof from the fact that it's the front door doesn't easily slam if all windows are closed.

We haven't yet done any underfloor insulation, which is still on our list of things to do (I'll probably hire a few students from the nearby colleges to help because I don't fancy the idea of scooting around on my back in a 15" crawl space for several hours :P). It'll likely be fiberglass batts with tension wire to hold them in. The foam underlayment of course insulates a little, so I plan on insulating very well in the crawlspace to offset that.

As for the water (this is still upcoming, as I haven't actually hooked it up yet), I'm going back and forth between a dedicated 30 or 40gal natural gas water heater (the total water in the system is about 25 gallons for the 1/2" PEX) and an air source heat pump. The water heater is going to be much cheaper and should be pretty efficient, although not as efficient as a heat pump of course. I think it'll strike a pretty good balance between upfront and runtime costs.

Since I've got only 9 or 10mm of the bamboo flooring and the thin underlayment on between feet and heating, I figure 80 to 85 degree water temperature should be sufficient, but that and the flow rate is something I can play with and fine tune to the needs of the rooms. Regulating the temperature is likely going to be done just with the water heater itself - I'll set it so that the temp ends up about 85 degrees (a thermometer in the feed line to the manifold should do the trick) and the water will be pumped from there directly to the loops. That way I don't have to mess with a second cold water line and a mixing valve.

Edit: I haven't thought too much about the thermostat yet. I figure I'll regulate the system by outside temperature - if it drops below a certain level, it turns on the pump. It'll take some experimenting to find the right setting, but should work. Since I don't have the tubing in concrete or other large thermal mass, there should be relatively little delay between turning on the pump and the floors warming up.


Do you have any input on the above setup? I'd appreciate additional ideas!

[AC_Hacker]

Originally Posted by opiesche

...I meant 6" exterior walls with fiberglass roll insulation. I didn't do it myself, but have opened some of the walls (to run new power outlets), and that's what I've found in two of the exterior walls. The windows are relatively new (late 90s or so), and are double pane vinyl. The attic is insulated with about 6" of loose fill fiberglass (something I plan to augment with additional batts in the future).

Not too bad... but as we in this forum have found out, the R-ratings for various insulations are determined in lab conditions with NO INFILTRATION. This means that if you have a wall with holes for power wires and outlets, you will get infiltration and you will not get the full insulation that you have paid for. Some homes are now being built with a separate, inside, 2" utility partition, an all power and water intrusions and power outlet and switch installations take place there, leaving the insulated wall intact and air-tight to work to maximum effect.

...Just saying that things can be much better than they have been in the past... because in the future it may be very important.

Originally Posted by opiesche

We didn't do a full heating load analysis - our estimate came from the fact that my parents' house sees temperatures at least 35 degrees below what we experience in winter. They've got double the density of heating loops, and similar insulation, and about the same water temperature (they have in-slab loops over a basement though). So we figured that half the density would work fine for us with the relatively mild temperatures we're seeing.

I'm sure that your new system will work just fine... you will be warm and comfortable and rightly, proud of your new installation.

But some of us here are trying to go beyond that and are eagerly venturing into the realm of 'diminishing returns'. As you surly know, when you DIY, some projects that when hired out, might not 'pencil out' in a favorable fashion, and when done DIY, they actually become not only do-able but quite desirable. For instance, I assume that your parents in Germany are using pipe spacings at around 6", or whatever the metric equivalent is... it does make sense to widen the spacings to 12" inches in your locale because your weather is so much milder, and with natural gas dropping in price, tighter spacings would not pay off in your lifetime.

However, if you had used the same spacings as your parents, it would open up the possibility of using low intensity heating to it's best advantage. Low intensity heating could be something like solar heating, where feed water only occasionally gets up to the temperature level that you can rely on with natural gas.

Also, another low intensity method, heat pump systems greatly benefit from higher efficiency floors, as they don't need to raise the temperature as high to warm the home to a comfortable level, and thus don't have to do as much work. The benefit to you is much lower power bills.

Originally Posted by opiesche

Your information about average temperatures seems roughly correct. There's a couple of weeks or so when the temps occasionally drop below 30 for a few hours (between 3 and 5am), but that's the worst we see.

We've never done a blower test, but the house seems reasonably infiltration proof from the fact that it's the front door doesn't easily slam if all windows are closed.

This all sounds very good!

Originally Posted by opiesche

We haven't yet done any underfloor insulation, which is still on our list of things to do (I'll probably hire a few students from the nearby colleges to help because I don't fancy the idea of scooting around on my back in a 15" crawl space for several hours :P). It'll likely be fiberglass batts with tension wire to hold them in. The foam underlayment of course insulates a little, so I plan on insulating very well in the crawlspace to offset that.

I have one of those crawl space insulation jobs coming up too, and I'm not looking forward to it.

But when you mentioned the foam underlayment, is it over or under your hydronic floor?

Originally Posted by opiesche

As for the water (this is still upcoming, as I haven't actually hooked it up yet), I'm going back and forth between a dedicated 30 or 40gal natural gas water heater (the total water in the system is about 25 gallons for the 1/2" PEX) and an air source heat pump. The water heater is going to be much cheaper and should be pretty efficient, although not as efficient as a heat pump of course. I think it'll strike a pretty good balance between upfront and runtime costs.

If you go with a larger size water heater (maybe even bigger than 40 gal), it will reduce the frequency of the 'heat-up' cycles. There is an efficiency curve that describes each firing of your water heater... the efficiency increases in the beginning of the firing, and levels off until the end of the cycle. By having fewer and longer firings, you will reduce the overall lower efficiency part of the cycle.

Originally Posted by opiesche

Since I've got only 9 or 10mm of the bamboo flooring and the thin underlayment on between feet and heating, I figure 80 to 85 degree water temperature should be sufficient, but that and the flow rate is something I can play with and fine tune to the needs of the rooms. Regulating the temperature is likely going to be done just with the water heater itself - I'll set it so that the temp ends up about 85 degrees (a thermometer in the feed line to the manifold should do the trick) and the water will be pumped from there directly to the loops. That way I don't have to mess with a second cold water line and a mixing valve.

I'm very interested to see how it all works out. One thing we very badly need is a database of performance from DIY installs.

Originally Posted by opiesche

Edit: I haven't thought too much about the thermostat yet. I figure I'll regulate the system by outside temperature - if it drops below a certain level, it turns on the pump. It'll take some experimenting to find the right setting, but should work. Since I don't have the tubing in concrete or other large thermal mass, there should be relatively little delay between turning on the pump and the floors warming up.

There are dual-sensor thermostats that are specially designed for hydronic heating, for applications exactly like yours. They cost maybe $200 or so. They even have an adjustable setting to find-tune for the thermal mass of your house, so that there is minimum over-shoot or under-shoot.

So, that's my take on it. I must confess that I have not put a hydronic system into my house yet, but I have been obsessively studying hydronic radiant floor systems for almost a decade. I am very interested in low intensity heat, as I am convinced that the future lies in that direction.

I'm hoping that Vlad will chime in here, as he has done a very good job in his house, and he has no shortage of opinions. He did not go the 'utility wall' approach when he built his house, but he did compensate with post-construction infiltration sealing that was phenomenally thorough... I've never seen anything like it.

Best,

-AC_Hacker

[opiesche]

Originally Posted by AC_Hacker

For instance, I assume that your parents in Germany are using pipe spacings at around 6", or whatever the metric equivalent is... [
However, if you had used the same spacings as your parents, it would open up the possibility of using low intensity heating to it's best advantage. Low intensity heating could be something like solar heating, where feed water only occasionally gets up to the temperature level that you can rely on with natural gas.

Interesting that you mention this. You're correct about the pipe spacing (it's almost exactly 6" for the room interior). One thought I've been playing with is, later on, installing solar water heating panels - water could go from the tubing returns into the panels (at an estimated 3F or so less than the feed temperature) to be preheated before being dumped back into the water heater. I'm a bit unclear as to how to control the temperature and prevent it from getting too high for the floors, short of using a mixing valve with cold water though.

What sort of temperatures can one expect from solar panels? If my estimates turn out to be good and 85 degree water is enough for our heating needs, is there a possibility to go only with solar heated water and turn the gas heater off altogether?

Originally Posted by AC_Hacker

But when you mentioned the foam underlayment, is it over or under your hydronic floor?

It's on top of the hydronic system, between it and the hardwood floor. It was primarily to keep the floor quiet and comfortable to walk on - it's only about 1mm thick, so its insulation value is relatively small. Good crawlspace insulation is still a must, of course

Originally Posted by AC_Hacker

If you go with a larger size water heater (maybe even bigger than 40 gal), it will reduce the frequency of the 'heat-up' cycles. There is an efficiency curve that describes each firing of your water heater... the efficiency increases in the beginning of the firing, and levels off until the end of the cycle. By having fewer and longer firings, you will reduce the overall lower efficiency part of the cycle.

That's great information to have, thanks! I was wondering what size would be best and had a hunch that bigger would be better - sounds like basically, the smaller the heater, the more it'll be running, so I'll try to go with a larger option.

Originally Posted by AC_Hacker

I'm very interested to see how it all works out. One thing we very badly need is a database of performance from DIY installs.

While it's still reasonably warm outside, I can take a no-heating run of measurements (maybe this weekend) during the day and at night. Days are currently between 78 and 82, nights between 52 and 65, so I could get a series of temperatures in, say, 2-hour intervals or so of interior and exterior temperature without heating.
Then, when the heating system is active, I could do the same, while correlating it with water feed and return temperatures. Is there any other data that would be useful?

Originally Posted by AC_Hacker

There are dual-sensor thermostats that are specially designed for hydronic heating, for applications exactly like yours. They cost maybe $200 or so. They even have an adjustable setting to find-tune for the thermal mass of your house, so that there is minimum over-shoot or under-shoot.

Again, great info! These would be measuring both exterior and interior and decide turn on and off based on both measurements, I assume?


Thanks for the advice, it's much appreciated. It's good to be able to have a conversation about this sort of thing as I install and tune the system to avoid some of the inevitable pitfalls


Olaf

[AC_Hacker]

Originally Posted by opiesche

Interesting that you mention this. You're correct about the pipe spacing (it's almost exactly 6" for the room interior). One thought I've been playing with is, later on, installing solar water heating panels - water could go from the tubing returns into the panels (at an estimated 3F or so less than the feed temperature) to be preheated before being dumped back into the water heater. I'm a bit unclear as to how to control the temperature and prevent it from getting too high for the floors, short of using a mixing valve with cold water though.

There are several approaches to the temperature control issue. In Europe where hydronic floors are usually high mass, the most used approach is to have the pumps circulating continuously, and the temperature of the water is continuously changed to maintain the desired set point. In this case, your heat stays on all the time, day and night and a night-time set back is not applicable due to the very large mass.

In the US, even with high mass floors, pumping is intermittent as is heating.

But low mass floors are not at all uncommon in the US, as you can attest. So, night time set back would be possible, due to lower thermal mass. With a low mass floor, your 'buffer tank' would be your thermal mass, and in your case, if you are using a water heater, it is your buffer tank, too.

Vlad had a very interesting, and complex controller that sensed outside temp and inside temp, and because he was using the same water heater for domestic hot water water and floor heating (the floor water was kept separate from the domestic hot water by using a heat exchanger), his controller would admit shots of hot water into the circulating floor water, as needed to maintain comfort.

Originally Posted by opiesche

What sort of temperatures can one expect from solar panels? If my estimates turn out to be good and 85 degree water is enough for our heating needs, is there a possibility to go only with solar heated water and turn the gas heater off altogether?

You should go on over to Build It Solar and check around. Gary lives in Colorado, as I recall, and is using solar for heating with gas back up.. and he has radiant floors just like you built. He's pretty good about keeping records.

Originally Posted by opiesche

That's great information to have, thanks! I was wondering what size would be best and had a hunch that bigger would be better - sounds like basically, the smaller the heater, the more it'll be running, so I'll try to go with a larger option.

This is the kind of thing that you'd be best to find out locally. You might ask a local hydronics outfit, they probably won't be too insulted if you ask them for advice.

Originally Posted by opiesche

While it's still reasonably warm outside, I can take a no-heating run of measurements (maybe this weekend) during the day and at night. Days are currently between 78 and 82, nights between 52 and 65, so I could get a series of temperatures in, say, 2-hour intervals or so of interior and exterior temperature without heating. Then, when the heating system is active, I could do the same, while correlating it with water feed and return temperatures. Is there any other data that would be useful?

Well, one thing you could record is what temperature outside, with no heat and no cooling, makes your house a comfortable temperature (say about 68 to 72) inside? So lower comfortable would be the temperature you plan to heat it at in the winter, and higher comfortable would be the temp a little bit before you wish that the AC was running. So you're looking for the outside temps that produce the inside temps you like. This could be useful to you later.

Otherwise, just wait until the heating season gets rolling and record the temperature of the water that goes into your floors to provide heat and the temperature of the water coming back from the floors. at first the difference between these temps will be big, but then the difference will stabilize... this will give you an indication of the efficiency of your floors. Vlad ran some kind of design program for his floors and the program indicated that his water temp should be about 115 F, as I recall. He said that if he had kept the floors at 115 F he would have cooked his family. So he dialed it back to between 90 and 95, as I recall. He really did a very good job of insulating... curiously he said that his system keeps his house comfortably warm, but the floors don't feel warm. I take that to mean that he has really cut his heat loss way down.

Vlad, where are you, we need your input!

Best,

-AC