On Sat, 13 Mar 2010 11:00:38 -0800 (PST), seani
wrote:

I'm thinking or replacing some fairly elderly (20+ years I believe)
hardwood double glazing including a large set if hinged patio doors.

I'm thinking about good quality triple glazed units in both cases. Am
I likely to see much of an improvement given the extra layer and the
passage of time?


You could consider just changing the glazing for Pilkington K glass
which is more efficient thermally than what you have and which will
cost less than what you have.