Damp, Cold Off Grid Cabin - Heating

Hey all,

So this past weekend, I successfully installed a small off-grid solar system in the family cabin on Vancouver Island. Sufficiently sized to run some lights, a small TV/Satellite and the vacuum once in a while. It's got me thinking about the next solar project...

The cabin itself is used about half the year from April/May through to about October with the summer months seeing the majority of the use. The place is a 30 y/o log cabin, without a great deal of insulation. It's heated today with wood -- we have a Cast Iron Woodstove in the kitchen, an ancient (but effective) airtight stove in the basement, and an extremely non-efficient fireplace in the livingroom (we are considering converting this to a wood insert). No air movement or air handling systems.

The basement of the cabin is a walk-out, concrete slab on grade. The basement is very cold and damp feeling given the amount of rain we get out this way. The cabin is about 1000 sqft per level and that includes the basement, main floor, and loft.

We are trying to figure out the best way to get some heat into the basement so that the cabin is a little warmer -- this past weekend the external air temperature was in the mid to high 50's but in the basement you could still see your breath. We find that after the cabin has been sitting empty, it can take a day or more to take the interior chill off the place. Would love to have a system that can keep the chill off permanently so we arrive to a warmer place (not 70 degrees, just not freezing).

I was thinking a relatively efficient (however, costly) method for taking the chill off the basement year round would be to install radiant in-floor heating (powered by solar collectors) in a section of the basement floor over the existing slab using a product like this one (http://www.thermalboard.info/). I could do half to 3/4 of the basement floor with relative ease as it's unfinished today. Might also be able to take advantage of the hot water to supplement our propane hot-water tank. Also provides an option for heating the main floor as the joists are exposed to access to the underside of the main floor is simple.

Another cheaper alternative would be to replace some of the basement windows with solar window heaters. The basement is south facing, however, windows are under a deck and there is quite a bit of shading to the south. Adding solar windows to the upper area is a no-go because of the logs. Not sure if it would be effective.

Anyhow, is there a better method? We're not looking to use a method here as a permanent full time heating solution -- simply to take the chill off and augment the wood heat sources we have...