Solar heated water can be collected and stored to be used when needed as, solar heated air is real time.
Being that your heating needs are mostly at night, and domestic hot water is always used, I would thing solar water would be the better way to go.

Nothing beats radiant heat for comfort either

Thanks. I was thinking the same thing - If I can set up a system to heat water, couldn't it provide heat for radiant heating too. But I think Gary has mentioned that solar water heaters are the least efficient solar option. So I'm wondering if the inefficiency would preclude a system that need to heat water for the tap as well as water for a radiant system.

umm i have actually heard that solar water heating is the MOST efficient solar option.

great. do you have any links for information?

Hi gary -

Several of the outfits installing solar water heating systems around here have told me that the cost of installing a system that also uses solar heated water in a radiant heat system is too high to be viable; i.e. normal solar hot water systems won't produce enough hot water for radiant heating, especially at night, so that you'd need to quadruple the collector area and storage capacity to run both systems. One guy told me that even if I tried to minimize my usage thru efficient zoning, the cost of the equipment is so muich greater that I'd still be better off reinstalling my forced air system run on natural gas. Any ideas?

Thanks, Gary. My original plan was to build a solar forced air heater. The problem is storage. Out here I only use heating at night. It seems any system to store the heat would be just as complicated as a solar water/radiant heating system.

Insulation is a challenge. My circa 1920 house has over 40 original leaded glass windows. Except for the attic, I suspect there's no insulation anywhere. Replacing the windows would very expensive. Maybe I should just reinstall my NG forced air system? I'd get in and out for under $5K.

Hi, Anyone have any good links regarding DIY solar water heating. I want to add a rooftop pre-heat system to feed
my standard gas water heater.

We will do the work ourselves and would love to hear from
others that have knowledge.

bukzin ~ check out the links Gary provided. Lots of info there.

Also check in at the Mother Earth News site. Solar has been their thing for decades. One link attached but look through the site for more info.

Also google for 'batch hot water', lots of sites, but solar batch heating is so simple that you may get bored.

Here is a link that might be useful: solar heating

Hello, I have been givin 4, 3x7 water heating panels.And would like to use them as a forced air system.

Anyone have an idea what type & size blower I will need to push the air thru the 1" copper pipe in the panels And into the house? (about a 90ft push!)

Thanks for any help.

You can't push air through a 1" pipe unless you use a compressor, but the cost to operate besides the noise would far exceed the energy gained.

You option is to circulate a fluid through them with a coil whether it is a fan coil unit, terminal unit, coil in duct or radiant tube.