BOX WINDOW PELMETS
Let me begin by stating that I am not a carpenter or any trade related to that line of work. I am in fact a retired accountant.
We live in a very cool climate region of NSW and while we have block out curtains we have noticed that some heat still escapes. The reason of course is that hear rises and drifts across the ceiling until it finds an avenue of escape, behind the curtains and through the glass windows.
To prevent this loss I decided to install pelmets. Now custom made pelmets are very expensive and only covered the front of the curtains and not the top. Solution, install complete wrap around pelmets.
These were easy enough to make and the cost to “seal” the windows in our lounge, kitchen and dining rooms was less than a single prefabricated metal pelmet which as I stated did not cover the tops of the curtains


PHOTO 2
PHOTO 4
Photo 1 a finished box pelmet
The materials used are milled pine for the tops of the pelmets, the sides are also pine wood, in this case moulded to blend into other furniture.

Photo 2 , corner detail showing the small amount of putty required.
The mitred corners were cut using a drop saw to ensure a 45degree angle.
A note on my personal experience here, wood of all kinds is of course a natural product and will warp. The degree may vary from non-existent to extreme, avoid extreme. I found that even with precise measurements of the elements of my pelmets (top and three sides, the pelmets are designed for wrap around curtains). There came a point at which some putty was required. There are many types of this product available, I found one that matches the colour of the pine wood.
The box pelmets were finished with Sikkens (again to match existing window furniture)

Photo 3, box pelmet covering the insulating block out curtains.

Photo 4 revealing the wrap around effect.
I can honestly say that installing these box pelmets over the windows of our has made the house warmer by reducing heat loss. Easy enough for anybody with modest skills like mine.