Glass is what makes a compact interior feel generous and what loses the most heat. Both facts are settled by orientation before they are settled by specification.
Orientation decides more than the glazing unit
A large opening facing south gains heat all winter and overheats in July; the same opening facing north gives even light and no gain at all. Deciding which elevation carries the glass is free on the drawing and impossible afterwards.
In practice most compact plans want the main glazing towards the view and the evening light, with a smaller high window opposite for cross light. That combination reads as space; one big window alone reads as a corridor.
Triple glazing is not automatic
Triple units cut heat loss and add weight — roughly 30 kg per square metre against 20 for double. On a transported building that weight has to be carried by the frame and lifted by the crane, so it is a structural decision as much as a thermal one.
In a mild coastal climate double glazing with a good coating can be the better trade. In an alpine or Scandinavian winter, triple pays back and also removes the cold draught you feel standing next to a large pane.
Shading belongs outside the glass
Once solar radiation is through the pane it is inside the house, and an internal blind only converts it to radiant heat. External shading — a roof overhang, a shutter, a screen — stops it before it arrives and is several times more effective.
A fixed overhang sized for the summer sun angle still lets the low winter sun in. That is the cheapest climate control in the project and it costs nothing but a drawing note.
Opening lights are a ventilation question
Fixed glass is cheaper and tighter, and a house with no openable window relies entirely on mechanical ventilation. At minimum, put an opening light at each end of the plan so the house can be purged on a warm evening.
A rooflight over the loft does more for summer comfort than any wall window: warm air leaves at the highest point, and that is the one place it collects.
Frames, seals and the coastal case
Aluminium-clad timber gives a warm inside face and a maintenance-free outside one, and it is the usual answer for a house that travels. All-timber frames need the same attention as timber cladding; all-PVC frames move more than the opening they sit in.
Near the sea, ask specifically about the ironmongery finish. Handles and hinges corrode long before the frame does, and replacing them on a sealed unit is not a five-minute job.