Hello all,

I have read with great interest the many threads on 3G, suppliers and prices but I still have a few queries unanswered.
I am building a small extension on the north side of the property; this will be a new kitchen/utility. The opening for the window in the new room is quite large at 2400mm wide by 1050mm high. Due to various constraints a sliding window would fit the bill just right. I envisage it to be made of 4 x 600 elements, with the 2 outer fixed and the two center ones sliding towards the edges (do I make myself clear??). I am planning on using 3G and have approached various manufacturers whose name I have found on this forum. But I am wondering if the seals around the moving parts will be airtight enough not ot negate the benefits of 3G?

I am also looking at possibly replacing my existing 2G which is 15 years old. It is a 4-16-4 unit and has BS5713 stamped in between the 2 panes. Does anyone know what were the minimum U value to achieve back then (Bearing in mind that these were replacement units already)? I have one very big window, 2950 long x 1500 high, south facing, which allows the sun to warm the room quite nicely. Would a replacement in 3G, which I understand restrict a little bit the passive heating effect, have much negative influence given the size of the window?
Many thanks in advance for your help.

Nicolas