Question about an idea I have about radiant hydro heat.

[markandkristi]

 I was looking on a website the other day, Builditsolar.com I believe and there was a post on there about a guy that made a PEX radiator inside his wall for radiant wall heat. I had heard of radiant floor heat but not this and havent really found much info about people doing the radiant wall heat but it did get me to thinking. I am considering making a solar hot water pre-heater/heater and maybe running it through the walls in similar radiator fashion to provide extra heat. The area I would do this I dont expect it to just carry the load but would definately supplement the heating. Then I thought if hot water inside the hose could provide heat, I wonder if cold water could provide cool in the summer. What I had in mind was having a valve right before the solar water heater, in the winter you could route the heated water thru the PEX pipes in the wall if wanted or bypass all together, and in the summer have the unheated water flow thru the walls before it was heated. The water would be circulated without a pump and instead when water would be used which would be several times a day. Just wondering if in the summer if the cooler water wouild cool the wall down to act as a thermal mass? Any input on this topic would be greatly appreciated. It just sounds like it could work in theory. Thanks.

[RP]

Unless you live in the arid desert, condensation is going to give you a serious mold problem on and in your walls.  This is also why slab heat systems won't work for cooling either.

[tanner0441]

Hi

Many years ago I put a 1Kw resistance pad behind the plaster on a brick internal dividing wall, this radiated heat into my hallway and was detectable from the other side of the wall. So it helped for heating, but if you deliberately cool a brick wall below ambient and that drops below the dew point, then that wall will absorb the moisture from the air, it may lower the humidity but I doubt it will give any cooling, and as stated the best case situation could be mould, worst case could be any plaster on the wall degrading and falling off.

For heating I think it could be a lot of work, for cooling I think it is a none starter.  Remember AC units have a condensation tray under the evaporator, what would you do with up to 2ltrs an hour of condensate in a brick wall.

just my opinion...

Brian

[Photon]

Hi guys, i work in this area so thought i would give two pence worth.

Both heating and cooling can be provided from radiant slab systems, it is however more typical to incorporate in floor slabs or even ceiling slabs. The hydronic coils are typically embedded in minimum 100mm conc fixed to insulation.
There are typically no issues with condensation as surface temperatures in cooling mode would not drop below say 18 deg C.
The thermal mass provided allows for both heat and coolth to be radiated into the space. In a lightweight structure subjected to high external swings in temperature it is a good solution maintaining favourable thermal comfort.

I have designed quite a few of these systems which are coupled to typically ground source heat pumps in europe and australia. It is possible to couple a slab system with solar however for heating the benefits are minimal given the mismatch between solar gain and heat load.
In saying that i designed  2 buildings which incorporate nocturnal cooling, basically cooling a floor slab using solar running at nighttime to reject heat to cloudless sky. If you have un-glazed solar panels (pool heaters which drain back) it is possible.

There is more to it than that but it should give you food for thought.
Wikipedia 'Trombe Wall` it is based on air movement through walls but the principles are similar.

Hope this helps