Changing windows from woodenframe to PVC u

[Hedge]

I'm not sure that I'm asking this question in the right place, but my displays are on my window sills, and in the next month, we are replacing our windows with PVCu instead of the current softwood and leaky frames. Both of them have or will have double glazed units in them. We are also going from grid leading to plain panes.

What I am wondering is will the lack of drafts affect my growing of orchids? the new frames will have trickle vents.

Also, will the lack of leading make much difference to actual light levels?

I currently grow a range of Phals, Oncidium alliance intergenerics and Phal type Dendrobiums on or near to the windows. My Paphs are further back into the room.