p>Thanks for your question, and I would start here in general terms of efficiency in heat delivery - <strong>there is no great difference in the energy efficiency between air heated floors or hydronic (liquid) radiant floors, at least when they are heated with the same fuel.</strong> Meaning – a boiler heating water that is circulated through radiant tubing in a concrete floor will not be any more or less efficient that a boiler heating a water coil that blows air through a floor.</p> <p>The fuel source (gas, electricity, propane etc) will affect cost and efficiency, but differences in how you deliver heat isn’t as big a factor in determining efficiency. This page discusses the differences and pros and cons of each system – </p> <p><strong><a href="/guides/3203/air-heated-radiant-floors/" target="_blank">Radiant floors heated with air tubes</a></strong></p> <p>Moving into a solar solution though and choosing between a solar water heater and a solar air heater, there you would for sure have more variables in terms of the initial cost of the system, return on investment time, maintenance and lifespan. </p> <p>I assume you saw our page on <a href="/guides/3368/solar-air-heated-radiant-floor-kit-diy-problem-soils-expansive-clay-leed-passive-house-zne/   " target="_blank">solar air heated radiant slab on grade floor</a>. I would personally lean towards that because they address a lot of the issues that come up with solar thermal water heaters – read more here, which can have a lot of maintenance issues. The thermal solar air panels we installed in that <a href="/prefab-kit-homes/" target="_blank">prefab kit house</a> obviously don’t leak water, freezing is not a concern, and even summer overheating has been solved because that system has been adapted to generate solar hot water in summer in part to cool the system.</p> <p><a href="/guides/3296/all-about-solar-thermal-collectors/" target="_blank">Solar thermal water heaters can, in a bizarre twist, need to be covered often during summer to avoid overheating</a>. I hope this helps, check out those pages and if you have more questions let us know, but include your <a href="/guides/3521/climate-zones-map-usa-canada-construction/" target="_blank">climate zone</a> as well and we can better help you decide. </p> <p> </p