I just finished making some windows for a new shed/workshop I’m building (see attached). I followed the YouTube series by Bradshaw Joinery called “Oak Casement Window” in which a guy designs and builds a double-glazed oak window. He uses a lot of industrial machinery but the series is good to get an idea of the design and build principles. The first video in particular is very useful as it walks through the design drawings in detail. A modern window has a lot of technical features to control water (e.g. drip edges, grooves to prevent capillary action, drainage holes, and of course rubber seals) which you might not be familiar with if you (like me) are building a window for the first time.

As Larry said, you may need to make sure thermal performance meets local building regulations if you’re going to install them in a dwelling (mine is and outbuilding so not subject to those rules, but I still want it to be warm inside). My windows are simple single-casement designs with standard 28mm double glazed units. I don’t have machinery to cut large rebates and couldn’t work out a good way to do it with hand tools so I formed them by attaching stops with screws and glue (unfortunately the stain finish I used has highlighted the screw plugs which were previously quite subtle). They’re a bit rustic looking but overall I’m very pleased with them. Next time I’d glue on the stops using clamps rather than screws.

I’d say that window-making is definitely achievable for an amateur woodworker, although I’d advise practicing on an outbuilding window or a cheap pine prototype before making a start with expensive hardwood.