> Is it possible to retrofit these to burn H2 Yes and no. Yes in theory. But hydrogen burns much hotter, has a higher flame speed (spark -> boom!, not woosh!)

> Is it possible to retrofit these to burn H2 Yes and no. Yes in theory. But hydrogen burns much hotter, has a higher flame speed (spark -> boom!, not woosh!), and burns in a much greater range of concentrations in air, so leaks are...dangerous. Hydrogen is also very good at leaking. I wouldn't have it near my house. Edit: insulate and triple-glaze. Then you have a much smaller problem to solve, for both heating and cooling.