Good selection of nice doors in that area. Sunrise, Soft-Lite, and Okna (all in vinyl) are available.

Great advice above. I'd add, that since your primary concern is energy efficiency, a comparison of u factor and air infiltration ratings (independently tested) would be wise. Vinyl doors are going to be a bit more airtight if the appearance is acceptable to you.

Great, thank you both!

What would be a good source of independent information in order to do those comparisons? I found nothing on patio doors on Consumers Reports, unfortunately.

We have discussed the CR debate here before and while a useful tool on some things, I don't think that windows and doors fall into that category. Best thing is probably talk to some local contractors and window/door specialists.

Thank you, @Windows.

When I referenced the independent testing, it is in with regard to the thermal ratings as tested by the nfrc (nfrc.org), and the structural ratings tested by an ANSI certified laboratory, including air infiltration and design pressure. A source like Consumer Reports will be far more subjective than certified testing data, along with other inconsistencies as WoW alluded to.

Our wood/aluminum clad Marvin sliders are performing pretty poorly after 20 years. I keep trying to find someone who will try to make them work better, give them a tune-up, whatever -- no one seems interested in taking on that challenge. So we will probably have to replace them.

What is the nature of the malfunction? Some pictures and a description might get you some feedback and suggestions.