I am playing in my head (again) with some, off the wall, experimental, theoretical, ideas about radiant heat flow through  building, and looking for some assistance.

Having no experiance with radiant, there are some ideas that some of you may be able to quantify or explain why they are flawed.  These are not actual in use designs, but more theoretical questions about heat movement through slabs etc.

If this discussion interests you, please email me @ [email protected]

Thanks,

Bill

I would just go ahead and ask. Anyone not interested can not read your thread.

Ok I will throw a couple out there.. In a new home with Slab on grade, we are not planning Radiant for several reasons, but with the cost of pex I plan on putting the the pex in for potential future use possibly with Alternative solar collector systems.

But in the mean time, this will have pretty decent Passive solar, with uncovered concrete floors. My Thought is, would there be value in orienting the piping in north/south zones, and using a small circulating pump, transferring the heat from the warm south edge to the cooler northern portion? is there a big enough temperature difference to make it worthwhile? Then if we do hook it up to a system in the future would it not make sense to reverse the flow in order to "dump" the heat in the northern portion first, thereby not dumping excess heat into the sun warmed slab on the south side?

#2 We are installing a Very efficient fireplace, and I plan on having it mounted in a Mass wall in the center of the room, 12 inches thick, 7 feet wide, and ceiling high. Would it be effective to pace PEX in the mass wall surrounding the fireplace, down into the floor, keeping it insulated in the floor.
Then the thought was to route the pipe through the floor to the bedroom and bathroom leaving it exposed in the concrete there, to "dump the heat". then route it back to the fireplace exposed. The loop aroung the fireplace could be about 8 loops. This would move heat from the fireplace which has excess, to an area far from it with little physical energy use. Feasible?

IIRC, these things have all been discussed in other threads. IMO, skip the mass wall and store heat in a water tank. If you want to better distribute passive solar heat, your #1 need is substantial air circulation. It's not like all that radiant solar heat stays nicely in the slab.

#2 We are installing a Very efficient fireplace

A very efficient fireplace will be sealed and put the heat in the room, not into the wall. If you want to move the heat elsewhere, get a model that has the capability for "zoned" heating. A fan to move the warm air out to a remote zone isn't much energy.

As for your passive solar, you have to know how much insolation you are expecting and whether or not there will be any warmth to move.

You haven't mentioned where your passive solar is.

And, I will second jonr's remark on air circulation.

They make both gas and electric fireplaces that have blower motors on them to push the heated air into the room instead of venting right out via the flue.

Or if you really want to retain 100% of all the heat, get an electric fireplace that is NOT VENTED and 100% of the heated air is pushed right into the room via a blower motor. No flue needed:

These put out 4,700 & 5,000 BTU's per hour:

LED Fireplace

Napoleon Electric Fireplaces


I wouldn't use it as the PRIMARY source of heat but as a supplemental source of heat, if needed. Some have a nice feature that allows you to display the LED flame but WITHOUT having heat, so it's more ambiance. I've seen these LED fireplaces in person and they look VERY real. Even standing right next to it, it appears real.

We actually have a fireplace now that we plan on using the same model again. (quadrafire 7100)It does have the capability of remote air distribution, and we plan on using that. However they tend to still produce almost more heat than necessary in the primary area. The mass wall is also a design element so it would be there anyway, which is why I would use it as a storage medium rather than water. The fireplace will be set back a few inches to expose the concrete in front of the firebox,to collect heat. Gas or electric fireplaces are out. We have a never ending supply of free firewood. Air movement will be the primary method of moving heat in the home, the floor idea was just to assist in that. Took me back to laying on the concrete at the pool as a Kid. May not move enough heat to justify the electricity to run the pump.

After some thought, you are right, due to the space configuration it makes more sense to move the passive heated air, than try to move the heat before it escapes the concrete. The mass wall still seems feasible though, especially on cool nights after the fire dies down.

However they tend to still produce almost more heat than necessary in the primary area.

I have a Quadrafire 7100. You can fire it 36 hours straight and it does not make the cement block enclosure feel any warmer than the surrounding room. Having a mass wall by the fireplace will not provide a source of heat any more than simply having the mass to help modulate room temperature over a longer time frame. You would have to get the room itself uncomfortably warm to have enough heat to move somewhere else.

In what geographic area is your passive solar?

I have always oriented the tubing so it could distribute the heat in passive houses and it works well so i wouldn't dismiss that approach that quickly. Most passive houses have lots of open spaces so a bit of airflow will help too and as HRVs are needed, this is the way to go IMHO. Having the tubing installed gives you the options anyway.

ICF, when we installed our 7100 we put a granite covered solid concrete hearth in front. the hearth gets pretty hot and holds heat well. That is where I got the idea for the mass wall storage. the front of the fireplace would be sunken back into the wall about 3 to 4 inches, thereby exposing the concrete to the hot face of the firebox.
We will also have a large concrete hearth.

I do plan on using the remote ducts this time, (Currently I don't as it was a retrofit) Think I should put them under the slab?

The Building location is central Oregon. Bend area.

Mike, there will be a lot of open space, my question is, do you feel the benefit of moving the heat in the slab will warrant the electricity to operate the circulation pump?

the hearth gets pretty hot and holds heat wel

Yes. That's where the fireplace blows out the hot air. There might be some radiant effect, too.  Do you want the heat in your house or in the concrete so you can get it out with tubing and a pump? If your hardwork is properly insulated, it should warm up to room temperature and help modulate the indoor temp. Yes, maybe a little hotter if it is right near the fireplace, but there is no point in creating an inefficient system. If you want a radiant system warmed by the fireplace, I understand there are a few models available from abroad that heat water directly.