The frame to the dormer is now up and the Internorm window and doors went in today.  More on the doors later, but  the window is triple glazed with a venetian blind mounted externally and a further fourth pane of glass to enclose the blind and keep it isolated from the weather.  In the winter the blind can be stowed away to maximise solar gain but in the summer when overheating is the issue the blind can be lowered and because it’s on the outside of the triple glazing it will be highly effective (unlike an internal blind).  The blind can also provide privacy and the fourth pane can be opened to allow for cleaning and easy replacement of the blind should it be required.  It’s a very neat and tidy solution to an awkward problem and does away with complicated and expensive external shading solutions.  Detailed with Intello for airtightness and Purenit to sills for cold bridging.