Solar radiant heat project begins

   / Solar radiant heat project begins #31  
You have done your homework. Here is what Im up against. I put in all radiant floors in the basement of the new home. The basement is one giant room that I will just be using for storage and work area. I insulated well under the slab and the home is very well insulated in the roof and 6" walls. The basement is closed off from the rest of the house so heat cannot flow up a stairwell. As far as having hotter and cooler zones, I don't think there is any way I can do that with this setup. The home is a ranch with the main living floor about 3200 sq. ft. The ceiling's are all mainly 10' with 20' vaulted ceiling in the great room.

I did research this before the install, but couldn't find a home where this kind of setup is being used. It would be nice to know what problems I may encounter. Since the build is still going on I may be able to correct a problem before it occurs.

Also, Do you think the floors on the main floor will stay warm. I know the basement floors will be warm, but will that warmth transfer into the floor above it? It sure would be nice to have warm tile in the bathrooms.
 
   / Solar radiant heat project begins
  • Thread Starter
#32  
Looks good, but, I'm as confused as ever about in slab solar heat! Reckon I need to find a video describing how it flows, etc. I'm wanting to install some pipes through floor joists in my crawl space built house. I read something about that. More research...

Let me se if I can describe it without a picture.

First the floor loop. Imagine a circle of pipe, full of water. Somewhere in that circle is a pump to move the fluid and somewhere else there is a fire under a section of it. As the flow moves the water round and round the whole circle becomes hot. Now build a house over it and you have a radiant system.

Next the solar. Again a circle of pipe with a pump. This time, instead of a fire we have a solar panel. Circulate it in the sun and the loop becomes hot.

Back to the floor loop. Instead of a simple circle, imagine a fork shape somewhere in the loop. The water can take any one of several routes or prongs of the fork and then rejoin into one farther around the loop. It looks like your arm. The water comes down the arm and out through one of your fingers. Then into the end of another finger, further around the loop, and back up the arm. Now imagine each finger is under a room in the house. Each room has it's own loop or finger. This way we can balance the flows to heat different rooms to different temps because slower flow delivers less energy and higher flow delivers more.

To get the solar energy into the floor loop we add a heat exchanger into the floor circle. This is the same thing as if you laid two pipes next to each other and ran hot water through one and cold through the other. The two waters never mix, but the cooler one warms up from the heat of the other one, through conduction. A heat exchange.

Now lay out the loops of floor piping around the ground and pour concrete over them. A radiant heated floor. Or mount the pipes up under a wood subfloor and run hot water through them. A radiant floor.

Now arrange it so that the pump and fire come on with a thermostat and you can control it.

Now heat a tank with the solar instead of the floor and then circulate the tank water at night and you are using solar at night.

The concept is simple, but the details make it more difficult. Issues like freeze protection, proper tubing, pump sizing, manifolds to connect and balance the tubing and flow rates, and collector design.

The collector is very simple in design and much like the description of the radiant floor. A pipe comes into the box and forks into about 8 smaller tubes that run the length of the collector. They rejoin at the other end and exit the box. The tubes are attached to a black copper plate that absorbs the suns energy and conducts it to the tubes. Water in the tubes warms and travels out to your storage tank. Cooler water comes in and warmer water exits. Round and round until the sun sets or the tank is hot enough. The controller simply measures the temp of the collector plate and compares it to the storage tank. If the collector is warmer, the controller turns on the circulating pump. When the temps become equal, it turns off the pump.

It's nearly the same thing a thermostat does. But the thermostat measures a temp and compares it to a constant setting. Cooler and it turns on a system, warmer and it doesn't. Thermostats of a different type, aquastats, can be used to "decide" when solar heat is available or if the system must use backup heat.

The whole game is water flow at the right time and in the right circuit, managing temperatures, and keeping it from ever freezing no matter what kind of failure happens. The reward is the most comfortable heat delivery system there is at a very low cost of operation and nearly endless hot showers from the sun.
 
   / Solar radiant heat project begins
  • Thread Starter
#33  
Cartod,

Your basement looks very well designed and installed to me.

Heating the basement will heat the upper floors. But it will be subtle and difficult to control. The bathroom floor should have it's own loops and thermostat, as should the other areas of the house. All areas have different use patterns and benefit from being their own zones.

Just to clarify, a "zone" is a thermostatically controlled area. A "loop" is a circuit of tubing in a zone. Zones can have any number of loops.

Rooms should have their own loops or be their own zones because they have different uses and different heat losses. Never, for instance, have a loop heat the kitchen and a bedroom. Each should have their own. Each floor level has it's own thermostat and each area, such as the Master bedroom, has it's own thermostat. But the living room and the kitchen can be on the same thermostat and have different loops. Loops are limited in the area they serve because they can only be so long before they are too restrictive. 1/2 Inch PEX (5/8" OD) is limited to about 300 linear feet, so it will only heat about 200 sq. ft. or so, depending on spacing and distance from the manifold. Typical spacing is 12" on center with 6" in the bathrooms and near the entry. Nine inches works even better than twelve inches, but is harder to work with during a pour. I used 3/4" PEX (7/8" OD) in my house because it is very tough and I could make longer loops.
 
Last edited:
   / Solar radiant heat project begins #34  
Cartod,

Your basement looks very well designed and installed to me.

Heating the basement will heat the upper floors. But it will be subtle and difficult to control. The bathroom floor should have it's own loops and thermostat, as should the other areas of the house. All areas have different use patterns and benefit from being their own zones.

Just to clarify, a "zone" is a thermostatically controlled area. A "loop" is a circuit of tubing in a zone. Zones can have any number of loops.

Rooms should have their own loops or be their own zones because they have different uses and different heat losses. Never, for instance, have a loop heat the kitchen and a bedroom. Each should have their own. Each floor level has it's own thermostat and each area, such as the Master bedroom, has it's own thermostat. But the living room and the kitchen can be on the same thermostat and have different loops. Loops are limited in the area they serve because they can only be so long before they are too restrictive. 1/2 Inch PEX (5/8" OD) is limited to about 300 linear feet, so it will only heat about 200 sq. ft. or so, depending on spacing and distance from the manifold. Typical spacing is 12" on center with 6" in the bathrooms and near the entry. Nine inches works even better than twelve inches, but is harder to work with during a pour. I used 3/4" PEX (7/8" OD) in my house because it is very tough and I could make longer loops.
Well, if you are correct and rooms need "zones" and there "own loops" it was all for nothing because I didn't do that.
I heated the entire basement and was hoping that the basement transfers the warmth to the entire home.
The basement has separate zones but those separate zones on the floor below won't transmit to "zones" on the main floor. I can always add tubing under the main floor in the floor joists but I'm gonna give it a year with just a hot basement first. I sure hope this was not all for nothing.

Keep in mind also that my outdoor wood boiler is 500,000 btu's designed to heat 10,000 sq ft. The indoor backup boiler is 300,000 BTU's.

Hope it works this way!

001_zps8a3e1a25.jpg
 
Last edited:
   / Solar radiant heat project begins #35  
We are building our home this year and I am considering radiant heat in the basement with a geothermal heat pump for the heat source. Any idea how much additional it costs to add the radiant heat?

Also, can you put carpet over the floor or will it insulate it too much from the radiant heat?
 
   / Solar radiant heat project begins #36  
We are building our home this year and I am considering radiant heat in the basement with a geothermal heat pump for the heat source. Any idea how much additional it costs to add the radiant heat?

Also, can you put carpet over the floor or will it insulate it too much from the radiant heat?
The radiant heat install is cheap when you pour it in the slab ($1.00 more per sq ft I think ). The geothermal is expensive and will take several years to recoup your investment. For me it was just not there yet.

The carpet question is a good one and will be waiting for a response, I would think that the heat would radiate right through the carpet.
 
   / Solar radiant heat project begins #37  
the radiant heat install is cheap when you pour it in the slab, the geothermal is very expensive and will take several years to recoup your investment.

With current rebates through our coop and 30% tax credits, geothermal is really not much more expensive than a good high efficiency gas system around here. If you don't mind me asking, do you know what the additional was for the radiant heat in your house? 3k? 5k?

Your house is going to be beautiful by the way!
 
   / Solar radiant heat project begins #38  
With current rebates through our coop and 30% tax credits, geothermal is really not much more expensive than a good high efficiency gas system around here. If you don't mind me asking, do you know what the additional was for the radiant heat in your house? 3k? 5k?

Your house is going to be beautiful by the way!
Radiant in the home was about 4k. Geothermal was about 17k. The rebates were not enough to make a difference. Look closely at geothermal before you shell out the cash.
 
   / Solar radiant heat project begins #39  
Radiant in the home was about 4k. Geothermal was about 17k. The rebates were not enough to make a difference. Look closely at geothermal before you shell out the cash.

Thanks for the info!
 
   / Solar radiant heat project begins #40  
I've done something very similar in my barn. But I'm having a bit of a hard time wrapping my head around how to finish off the install and actually get the heat working.

Details:

I built a 28x42 barn a couple of years ago. Did all the work myself so I'm just getting to finishing off some of the details. The floor is a 6-8 slab poured over 2" Owens-Corning Foamular industrial (high compressive strength) foam - with a vapor barrier on top of that. There are four loops of tubing in the floor for radiant heating. I used 5/8" Wirsbo oxygen barrier tubing that was specified as being good for in-slab installs. I also ran tubing over to areas where two smaller rooms will be located in the structure - one for an office and one for a bathroom. My intent was to use radiant panels on the walls in these rooms to heat them.

The barn is connected to my house with approx 100ft of Thermopex (PEX inside of an insulated tube) - this stuff is normally used to connect an outside wood boiler to a house. I'm using it to connect the barn to the house - so I can drive the heating in the barn by using the NG boiler I have in the house. Or - alternatively possibly heat both the barn and the house with heat gathered either from solar panels or an indoor wood or pellet boiler in the garage. The Thermopex is 1" diameter.

My problem is this - I'm trying to figure out how best to finally connect all of this and get it working.

Basically what I'll have is a boiler in the house that is currently driving cast iron baseboards - so the water temp it is supplying is hotter than the in-slab radiant would normally be run. The current boiler I have is a newer boiler (only about 2-3 years old) - but it's a lower efficiency unit - only about 85%. Once the whole house and heating system are complete - I will likely go back and evaluate whether or not going to a more high-efficiency boiler would be worth the cost. For the time being - I'd like to stick with this boiler.

In the barn I put in four loops of PEX in the floor - I'd like to segment the loops into two zones - front and back (two in each) - and be able to control those separately because the rear part of the barn will likely be kept hotter than the front as it's the shop area. But I'm only thinking of like a 10 degree difference. I might keep the front "zone" at say 40F normally - and keep the rear "zone" at 50 - so I could warm it up to a comfortable working temp more easily.

I understand that radiant slab heating is very slow to come up to temp so I'm thinking I might supplement with some wall mount radiant panels - or something like a Modine fan forced hot water heater in each zone to jump the heat up more quickly.

Is hooking this all up a simple matter of just creating another zone off of my existing boiler setup (it's currently a single zone - but when I re-do the heating in the house it it will likely end up as four zones) - getting some mixing valves and manifolds to supply the radiant zones in the floor with lower temp water - and then using the higher temp water to supply the radiant panels and/or Modine type units I'll use in the rooms and as supplemental heaters?

I want to plumb this up so that adding the additional heat sources (either solar or wood boiler) - could just be added later by just hooking up to the system and not entailing a re-engineering of anything.

Should I be using heat exchangers to isolate any portions of this entire system from other portions of the system?
 

Tractor & Equipment Auctions

2000 Mercedes-Benz S-Class Sedan (A50324)
2000 Mercedes-Benz...
Toro Z Master Mower (A50322)
Toro Z Master...
2008 International 8600 T/A Day Cab Truck Tractor (A48081)
2008 International...
Bush Hog Mod. 300 - 14 3 pt Blade (A50514)
Bush Hog Mod. 300...
2018 CATERPILLAR 249D TRACKED SKID (A51222)
2018 CATERPILLAR...
Great Plaines 2400 Tt (A50514)
Great Plaines 2400...
 
Top