[Greenbuilding] "Succesful" Open Hydroinic Heating System

[Ward Edwards]

I installed radiant heat in my house in Ontario using an open system and 
a Tagaki tankless hot water heater.  The house is super-insulated with 
R40 in the walls and about R50 in the ceiling.  The house is built into 
the side of a hill and uses passive solar design with just under 10% of 
the floor space in south facing windows.  There is 3" of blue foam under 
the 3.5" slab.  The pipes (pex-al-pex) are spaced at 1' intervals. I 
have a wood stove for supplemental heat.  The heating system has a 
single manifold and 5 loops all on the same zone.

I have had no problems at all with my system which is controlled by a 
single air thermostat near the center of the house (which is mostly open 
concept).  The thermostat has a differential of .6C and is set at 20.5C. 
  If it is a sunny day, the heat will not come on during the day and the 
temperature gets to between 23C and 24C. I generally light a fire around 
2-3 hours after sunset before the thermostat kicks in.  The radiant heat 
will come on about 5 in the morning if it is in the -10C to -20C range 
and run for about 3 hours to satisfy the thermostat.  If it is overcast, 
the system will generally start up again about 3 or 4 in the afternoon.

If I am lazy and don't have a fire during the day, the floors are nice 
and toasty for most of the day, but if I have a fire, the floors will 
fall to room temperature during the evening.  The floors have never been 
uncomfortably cold, but I do wear slippers most of the time.

I use around 1500 liters of propane a year and about 3/4 of a cord of wood.

I have seen several members mention problems with the spacing of the 
pipes.  What are other people using?

Ward Edwards
ward at buildgreen.ca

Sacie Lambertson wrote:
> Our experience with an radiant heat system with material bought from
> Radiantec and installed by ourselves in a three inch concrete floor one inch
> below the surface, mirrors almost exactly Ken's in Montana.   We too heat
> with wood primarily.  We have a four zone system with inexpensive air
> thermostats sat at 60 degrees; the in-floor heat in two of the zones, about
> 1600 ft sq, and the majority of the main floor, almost never comes on
> because the wood heat takes care of those spaces (we have fewer HDD in NE
> Kansas than does Ken in Montana).  These rooms, btw have very high ceilings,
> large windows and are generally open to each other and we run fans during
> the winter  above the stove to distribute the wood heated air more evenly.
> We also wear sweaters indoors during the winter.
> 
> The radiant heat is run by a propane-fired DHW heater  which had to be
> undersized because the vent for it was spec'd at 3 inches.  The vent was
> buried in a concrete wall during the framing and before I figured out which
> DHW I would buy, so there's nothing that can be done about the need for one
> larger.  The person who designated these details also spec'd 3" under floor
> insulation for the main floor which according to Wat John also is
> insufficient.  I put R 20 under the basement floor but would go higher the
> next time and would use foam (rather than Roxul).
> 
> If we didn't have the wood stove, we would be SUTC.  Before next winter I
> will have built/installed a solar panel system to provide pre-heated water
> and this will make all the difference in both the amount of propane we use
> each year (around 400 gals for all our hot water needs--we have an tankless
> in the bathroom because the DHW could never provide sufficient hot water for
> everything) and will also make the radiant system more efficient.
> 
> The Radiantec system requires incoming water around 120 degrees, (which we
> can't maintain with our current DHW tank so the floors where there is
> radiant heat never feel nicely warm).  Five years ago we had no difficulty
> dealing with the Radiantec folks, found them courteous and willing to
> respond to our many questions.  The pumps and manifold system they sent us
> are of good quality as well.
> 
> I too would install the PEX closer together (there is a limit to its bending
> ability though).
> 
> Cheers,  Sacie
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