Building a solid oak front door but thickness might be too thin

[Johan-]

I will be building a front door in an upcoming project. I would have preferred to make them half-French, but the equipment I have limits the finished thickness of the door leaf to 58mm. Most doors manufactured groove milled for Nordic climates are built to 67mm and more. I don't think the strength difference between 58mm and 67mm is crucial since the locks will be class 3. The side pieces will be made of 6(+2) laminated strips with alternating grains, totaling 120mm finished thickness with 67mm dowels.

The question is, what do you think the difference would be in terms of thermal value?

 

[anders07]

If you insert a glass pane, it will have the worst U-value... There is thinner, more efficient insulation you can use and also use metal for strength to keep the thickness down.

 

[Johan-]

Thanks for the comment and the info. I initially thought about installing the glass myself, but I will have to order an energy cassette for the small opening at the top to allow light into the hallway. There will be room for a 2mm thick metal sheet between the mirrors, as well as a 3mm foiled floor insulation on each side of the sheet. I assume the metal sheet hardly contributes to the heat value in a positive way!?