How much for radiant heat

[Drew Cutter]

Looking at doing two rooms in the house with solar radiant heat . Do I
need fewer solar panels to do this then to power the whole house ? Can
radiant heat be used to heat the whole house . The two rooms are on the
first floor.

 

[Ecnerwal]

Looking at doing two rooms in the house with solar radiant heat . Do I
need fewer solar panels to do this then to power the whole house ? Can
radiant heat be used to heat the whole house . The two rooms are on the
first floor.

Depends if you do it smart or stupid. Smart is solar thermal collectors
heating fluid that gets pumped around the floors (and/or a storage
tank). Then all you need is a small solar electric panel (if you want it
to be "all solar" or to work when the grid is out - otherwise just use
the grid if you have it, it's cheaper) for the pumping. This is pretty
efficient and cost effective. If you need backup heat it's easily
arranged.

Stupid is electric resistance heat driven by solar electric panels. This
is the option for people who don't care how much it costs. Solar
electric is very expensive. Solar thermal is not.

 

[Paul]

Looking at doing two rooms in the house with solar radiant heat . Do I
need fewer solar panels to do this then to power the whole house ? Can
radiant heat be used to heat the whole house . The two rooms are on the
first floor.

My first guess is yes, fewer panels for two rooms versus more rooms.
You could heat the whole house, but you imply that it is two story.
The upper floors are sometimes done with baseboard heaters that require
higher temperatures. If you just heat the downstairs floor the temperature
can be lower. The place at Tahoe ran 140F downstairs for the foundation
and 180F for the upstairs baseboards. The 140F is in the range of lower cost
flat plate solar thermal panels. The 180F is more in the range of evacuated
tube
collectors can can run $2000 per panel.
Obviously, if you are heating the slab during the day as well as storing
the
heat in water tanks you can continue heating at night from the water tanks.
But the water gets cooler as it is recirculated and the effectiveness is
reduced. You would have to talk to someone that has done it. Nick Pine
is a good source of info on this and sometimes posts here.

 

[Drew Cutter]

You gave sound advice. Any good source of info for further research ?

 

[Ecnerwal]

Any good source of info for further research ?

Solar-oriented radiant heat (eastern Canada):

http://www.thermo-dynamics.com

Radiant heat, DIY focus, with some solar options mentioned (Vermont):

http://www.radiantcompany.com/

 

[Drew Cutter]

This doesn't sound too bad , $$ wise. The ripping the floor up and
putting concrete might be different.

 

[Ecnerwal]

This doesn't sound too bad , $$ wise. The ripping the floor up and
putting concrete might be different.

It's obviously easier to put in when pouring a slab the first time. So
much so that it's not a bad idea to consider putting tubing in any time
you pour a slab, if there's the slightest chance you might ever want to
heat the space the slab is under.

If it's a floor on joists, you can run around in the basement or crawl
space and attach the tubing (and aluminum heat spreaders, if you feel
the need) to the underside without ripping up the floor (you might need
to rip down the ceiling if the basement is finished).

When retrofitting, there are multiple options to simply build up from
the current floor, rather than "ripping it up", unless you have an
inflexible need to keep the floor height exactly the same. Depending on
the floor you have, you might also be able to cut grooves into the
flooring to run tubing in, and build up only a tiny amount.

But it's probably not the way to go if you were not planning to redo the
floors - baseboard fin-tube units or radiators are much easier to add or
retrofit than in-floor radiant is. I've seen some radiant installations
in the walls (or extending into the lower part of the walls), but again,
not very cost-effective if not planning to redo the walls.

Often the first most cost-effective route (if you have no solar heat
now) is to set up to heat your domestic hot water - you use that all
year round, and it's easy to integrate. Hot air collectors for winter
heat are often the next most cost-effective. This discussion is heading
a bit off-topic for alt.solar.photovoltaic, might make more sense to
move it to alt.solar.thermal

 

[Cosmopolite]

This doesn't sound too bad , $$ wise. The ripping the floor up and
putting concrete might be different.

You may not have to rip up the floor. I will be doing this by laying
down 1"x1" sleepers every 8", with .5" Kitec tubing between, foil on
original floor, .5" ply, painted flat black on underside, over the
sleepers and laminate flooring over that. The space will be a sort of
space heating with hydronic as heat source. Foil and black paint to keep
downward radiant losses at a minimum. I made a test panel and found
that there was a large difference in temp. between the sleeper area and
the " open" area, but I think this will be bridged on long term basis,
test was short.


''''''''''''''''''''''''''''''''''''''''''''''''''
| | | | | |
| | 0 | | 0 | |

 

[Drew Cutter]

Then your saying that you don't need to use concrete to lay the piping .

 

[Drew Cutter]

Wow . This is good news. Hate to be the person doing this for the family
room. Very Tight crawl space. I was able to do it when i was 10. I
think you just save a few dollars. I will direct the question on thermal
newsgroup. Thanks.

 

[Cosmopolite]

Then your saying that you don't need to use concrete to lay the piping .

No, you don't. Concrete is a better thermal mass, but I would not
pour it over floor joists that were not designed for the weight and
stiffness. I will use short pieces of lefover plastic strapping as
clamps to hold the tubing down. ( 3" long, drill .06" holes close to
each end and use short, large head nails )

 

[[email protected]]

...I will be doing this by laying down 1"x1" sleepers every 8", with
.5" Kitec tubing between, foil on original floor, .5" ply, painted flat
black on underside...

Where are the sleepers and foil? The 0.5" tubing sounds too small for
good flow, with too little heat exchange surface, and the black paint
doesn't sound useful, unless you have sun in your basement, shining up.

I made a test panel and found that there was a large difference in temp.
between the sleeper area and the " open" area, but I think this will be
bridged on long term basis, test was short.

Don't bet on it. You might have better results with warm air or fin-tubes
under the floor, and foil below that.

''''''''''''''''''''''''''''''''''''''''''''''''''
| | | | | |
| | 0 | | 0 | |

Then again, IMO, radiant first floors don't fit well with solar heat,
economically-speaking. Better to heat with a sunspace and some sort of
mass or fin-tubes in the living space under the ceiling to both collect
and distribute heat, with no rooftop hydronic panels.

Nick

 

[Cosmopolite]

Where are the sleepers and foil? The 0.5" tubing sounds too small for
good flow, with too little heat exchange surface, and the black paint
doesn't sound useful, unless you have sun in your basement, shining up.




Don't bet on it. You might have better results with warm air or fin-tubes
under the floor, and foil below that.




Then again, IMO, radiant first floors don't fit well with solar heat,
economically-speaking. Better to heat with a sunspace and some sort of
mass or fin-tubes in the living space under the ceiling to both collect
and distribute heat, with no rooftop hydronic panels.

Nick

Ten feet to the south of my house is a two and half story house which
blocks all direct sunlight. Fifty feet to the east is my garage which
has the only clear southern exposure.