We want to build a solarium in Ontario, what do you think of heating it with a radiant floor and wood stove?

A solarium or sunroom in a cold climate would be a nice addition of living space, but it will not add heat to your home. I’m just putting that out there because It is a common mistake thinking a solarium will heat a home; that is one thing that it will not do. It will in reality devour energy for heating and cooling. For a better explanation of that, see our page all about sunrooms in cold climates – 

Solariums in cold climates won't heat your home

The biggest problem with a solarium in a cold climate like Ontario is that the moment the sun goes down, the temperatures inside will plummet. And in summer they can become unbearably hot. Despite the obvious appeal of basking in sunshine in your home, the amount of time a sunroom is actually a ‘comfortable’ environment is eclipsed by the amount of time they are either too warm or too cold. 

Your mention of a radiant floor and a wood stove would for sure improve the winter comfort, but please go into this with eyes wide open knowing that building an 800-1000 square foot glass box in a Canadian winter if going to need an awful lot of heat.

So back to your original question – yes a radiant floor is a great idea, Have a look here at our air heated radiant floor page, this design has a lot of thermal mass which would be great for balancing heat. The wood stove would be a nice addition, but you wouldn’t really need both. And a few questions to you -  will it have southern exposure? Is there shading like trees around it? and were you planning a full glass roof?