We're installing Warmboard which is a subfloor with channels for the hydronic and an aluminum plate on top to spread the heat. Looking forward to seeing how well it works.
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Subfloor and Hydronic Heating
- Thread starter mspohr
- Start date
SageBrush
REJECT Fascism
Sounds like it should work well so long as the pipes and plate stay in contact, although I personally just avoid walking around barefoot in the winter and the peeps keep their bodies warmed to a comfortable temperature. I see no reason to heat concrete, or floors for that matter.
Warmboard is wood subfloor with channels for hydronic tubes and aluminium sheet to spread the heat.
I assume you do heat you home. Heat rising from the floor is most comfortable.
SageBrush
REJECT Fascism
Do you use the seat heater in your car ? Why does it exist in the first place ?
After all, you can simply just heat up the cabin.
Exactly!
Heating the seat gives heat rising from below which is much more comfortable and efficient than heating the entire cabin. Same as floor hydronic heat.
SageBrush
REJECT Fascism
The seat has a low heat capacity, and the heating is restricted to ~ 30 cm x 30 cm surface. Moreover, it is off when you are not sitting in the car in the winter and it heats you up directly instead of the entire car.
Night and day
Just goes to show how efficient it is. Only used when you need it and just a small patch heats your butt and your body.
On one of my early long distance winter trips, I was running low on charge heading home. Turned off cabin heat and left the seat heater on. Arrived home with 7 miles range and kept comfortably warm.
SageBrush
REJECT Fascism
"It" is not efficient -- we are talking about resistance heating.
The system efficiency occurs because the heat goes where we want it and little where else.
That is why I am not a fan of hydronic heating. Waaay too much heat goes where we could not care less. The same criticism can be leveled at just about any 'whole house' heating system, but hydronic heating has the added curse of heating up a large thermal mass.
As an advocate of the butt and heating pad approach to winter comfort, I've been shopping for battery powered vests. Crappy resistance heating, but *so*, *so* localized
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Intuitively what SageBrush says makes sense. Do we have efficiency data? Anyone with a good comparative link of different home heating methods?
Was thinking the other day on this when put my hands over the toaster when toasting up some bread. Used a lot of energy but very targeted. Probably an efficient application for toasting bread. But in terms of being used to heat my house at a larger scale, that doesn’t seem like an efficient idea.
Thinking even if this could be done with a heat pump instead of resistive heating, most of the heat gets wasted into local hard structures where it’s not needed. Rather it needs to be rapidly convected through the air onto the humans quickly before lost into the walls, floor, ceiling, etc.
Was thinking the other day on this when put my hands over the toaster when toasting up some bread. Used a lot of energy but very targeted. Probably an efficient application for toasting bread. But in terms of being used to heat my house at a larger scale, that doesn’t seem like an efficient idea.
Thinking even if this could be done with a heat pump instead of resistive heating, most of the heat gets wasted into local hard structures where it’s not needed. Rather it needs to be rapidly convected through the air onto the humans quickly before lost into the walls, floor, ceiling, etc.
SageBrush
REJECT Fascism
Yep. This is the same reason we have become big fans of our toaster oven, rather than use the large oven. This works well for a 2 person family because the toaster oven is just the right size.
The heat pump has at least one, and perhaps 2 big advantages over hydronic:
1. It's a heat pump ! The hydronic heat source may not be
2. The heat pump is heating up the air (hopefully near you.) The hydronic is heating the floor thermal mass first, and then the floor is radiating/convecting to the house. If the foundation is not really well insulated the floor sends part of its heat to the house interior and part to Earth. All.winter.long
As Michael said, people like the hydronic vibe. But from an efficiency standpoint it usually sucks. It can be a smart(er) choice if it is part of an integrated heating solution that takes advantage of water to store PV energy for time-shifting. The general design scheme is then PV + a *huge* HP water tank + hydronics. Done right, the domestic hot water and winter heat conditioning is all PV. I'm not a fan though because I still have the summer to contend with and whole house conditioning is ... so wasteful.
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The most important thing for hydronic heating is to keep it completely inside the conditioned space and not let it thermally couple into a useless thermal mass like a concrete slab.
As a luxury feature, I installed resistive electric tile floor heating on the lower level tile floors that were installed on concrete slab. They are not intended to heat the space, but rather provide a warmer surface under foot in the winter. It was also installed with a thermal break layer on top of the concrete so that the slab would not just absorb all the heat. We rarely use it and just wear slippers instead.
As a luxury feature, I installed resistive electric tile floor heating on the lower level tile floors that were installed on concrete slab. They are not intended to heat the space, but rather provide a warmer surface under foot in the winter. It was also installed with a thermal break layer on top of the concrete so that the slab would not just absorb all the heat. We rarely use it and just wear slippers instead.
Twelve years with hydronic in concrete slab here in Maine. The floor heat is actually secondary to electric cooker as heat source and when the sun shines even that is too much so the floor is not used much. Before a storm—and probable power outage—I turn the hydronic up to warm all that useless thermal mass and bring in extra wood for the wood stove so the place stays warm for a few days. If I were building again I’d use heat pumps with battery backup and skip the hydronic; warm floors are nice but I definitely bought more than it is worth.
The real issue with hydonic heating IMO is that in a modern tight house, the floor doesn't get all that warm. The heat loss of the house is low enough that a slightly warm floor heats the house which doesn't do much for your feet. From an efficiency standpoint, there is some benefit to hydronic (moving heat in fluid easier than moving heat in air) but it generally isn't worth the cost.
A comfortable house comes from stable temperatures which comes from good insulation/windows/air infiltration.
Now - if your house is old or built with poor insulation, then a warm floor feels really good and will not overheat the house.
The thermodynamics of an uninsulated car with large single pane glass is a different animal than even an old house.
Most of the time, putting your money into the envelope and solar panels and then buying a cheap heat pump moving air is the cheapest path to a comfortable net zero energy zero house.
A comfortable house comes from stable temperatures which comes from good insulation/windows/air infiltration.
Now - if your house is old or built with poor insulation, then a warm floor feels really good and will not overheat the house.
The thermodynamics of an uninsulated car with large single pane glass is a different animal than even an old house.
Most of the time, putting your money into the envelope and solar panels and then buying a cheap heat pump moving air is the cheapest path to a comfortable net zero energy zero house.
SageBrush
REJECT Fascism
A heat pump does not move air other than over the coils and you still have to solve in-house air quality, but otherwise I agree with your statement
I just want to add my 2 cents: We installed hydronic heating 17 years ago and absolutely love it. We looked at the Warmboard product, but instead rolled our own system for costs. We put down 1/40" aluminum sheets on subfloor, and then cut 5/8" plywood into 8" strips with bevel, and put down the 1/2" pipe with silicone along the edges screwing the strips down snug to hold the pipes down against the metal.
With an outdoor reset system we really can't tell what the temperature is outside, it is simply always comfortable and stable inside. Well except for the tile floors in the bathrooms: if they feel warm to your feet then it is quite cold outside.
I guess I don't understand people here using term 'heat pump'. You can (we do) use a heat pump to heat the water just as easily as heating air for a forced air or minisplit system.
But using the water to distribute that heat through the house is far better in my opinion than blowing hot air on/off. Quieter, more comfortable and supposedly more efficient (~20%), at least that's what we were told doing the research 20 years ago. We have tall ceilings and in a forced air system, the hottest air would simply rise and heat the ceiling, the absolutely last place we want to be the warmest place in the house. So that does let us turn down the thermostat, keeping the things closer to the floor at a comfortable temp and not the ceiling.
In a This Old House show I watched a few months ago (the net zero remodel last season) there were using the hydronic system to also redistribute solar gain heat from the sun-warmed rooms to the cooler north side rooms. This kind of self regulation of heat delivery is built in. The colder rooms will suck more heat from the pipes than the warmer rooms simply due to thermogradiant. Forced air delivering N cubic feet of 100deg air per room can't do that, at least not without room level thermostats and motorized vent controls.
While ours is simply on wood subfloors, usually heating a large thermal mass is the whole point--it is much more comfortable. Most hydronic systems are installed in concrete for that reason. Nowadays, you can thermally decouple the slab from the ground well enough you aren't losing much out that way.
Anyways, that's our experience. I do hate forced air systems for the noise and blowing air. Always have. And doing it ourselves wasn't more expensive. Granted, the systems are pricey if you hire people to do it all but that would appear to us to be the only downside.
With an outdoor reset system we really can't tell what the temperature is outside, it is simply always comfortable and stable inside. Well except for the tile floors in the bathrooms: if they feel warm to your feet then it is quite cold outside.
I guess I don't understand people here using term 'heat pump'. You can (we do) use a heat pump to heat the water just as easily as heating air for a forced air or minisplit system.
But using the water to distribute that heat through the house is far better in my opinion than blowing hot air on/off. Quieter, more comfortable and supposedly more efficient (~20%), at least that's what we were told doing the research 20 years ago. We have tall ceilings and in a forced air system, the hottest air would simply rise and heat the ceiling, the absolutely last place we want to be the warmest place in the house. So that does let us turn down the thermostat, keeping the things closer to the floor at a comfortable temp and not the ceiling.
In a This Old House show I watched a few months ago (the net zero remodel last season) there were using the hydronic system to also redistribute solar gain heat from the sun-warmed rooms to the cooler north side rooms. This kind of self regulation of heat delivery is built in. The colder rooms will suck more heat from the pipes than the warmer rooms simply due to thermogradiant. Forced air delivering N cubic feet of 100deg air per room can't do that, at least not without room level thermostats and motorized vent controls.
While ours is simply on wood subfloors, usually heating a large thermal mass is the whole point--it is much more comfortable. Most hydronic systems are installed in concrete for that reason. Nowadays, you can thermally decouple the slab from the ground well enough you aren't losing much out that way.
Anyways, that's our experience. I do hate forced air systems for the noise and blowing air. Always have. And doing it ourselves wasn't more expensive. Granted, the systems are pricey if you hire people to do it all but that would appear to us to be the only downside.
We have an infinitely variable speed air sourced central heating pump. Except when asking the system to run at max capacity to get to a significantly different desired temperature goal, it's running at a fraction of maximum air flow and whisper quiet - you don't know it is on when maintaining goal temperature.
BriansTesla
Old school meets new tech
I put hydronic heating in the concrete floor of my house built 23 years ago. Currently powered with a $250 instant electric hot water heater. Very stable, clean and comfortable heat with the 23yo windows etc. Also have a masonry wood heater instead of a fireplace that works well when the power goes out. I would do hydronic heat again. The only disadvantage is that you can't turn it off and on and expect it to catch up quickly.
The vast majority of hydronic systems do not use a heat pump. A heat pump is very specific term that involves using a compressor and electricity (typically) to move heat around. Hydronics usually use a fuel or resistance electricity. You absolutely can use a heat pump but it isn't a very common product and because of that is a bit more expensive than a air-air heat pump. In a minority of the country are houses built without a/c so the duplicative system costs a lot of money even DIY.
For that money, you can buy a lot of solar panels....
There are lots of poorly designed forced air systems. You shouldn't write off forced air because of it. It is like writing off EVs because the Leaf battery life was so poor. I don't even have a staged unit and I can't notice the air moving. And I live in NC, so a/c runs more often anyway.
Hydronic heat by resistance electricity is not clean. At least not compared to using a heat pump. If everyone in the PNW moved to heat pumps, there would be plenty of hydro to charge cars. Every kwh matters even in the PNW.
For that money, you can buy a lot of solar panels....
There are lots of poorly designed forced air systems. You shouldn't write off forced air because of it. It is like writing off EVs because the Leaf battery life was so poor. I don't even have a staged unit and I can't notice the air moving. And I live in NC, so a/c runs more often anyway.
Hydronic heat by resistance electricity is not clean. At least not compared to using a heat pump. If everyone in the PNW moved to heat pumps, there would be plenty of hydro to charge cars. Every kwh matters even in the PNW.
SageBrush
REJECT Fascism
You just summed up PassivHaus in a sentence: Take the money that would otherwise have been spent on a traditional whole house conditioning furnace + AC, and spend it instead on PV, heat exchange, home envelope, and heat pumps. You spend ~ the same upfront but save big time on energy costs thereafter and the home air quality is *much* better
Well actually hydronic heating has been around since the Romans. And the reality is there is NOTHING more comfortable. I built it into our house and there is nothing like getting up in the morning and walking on warm tiles. And with tall ceilings it is most efficient way to heat. You don't have to worry about hearing the forced air go on while you are sleeping. And finally, it allows you to design the AC on your HVAC system solely for the AC so you can have your vents and returns placed optimally. Thus you are also more comfortable in the summer with no hot spots.
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