[stop50]

So Germany can build insulated windows that fit into historic houses, but in san fransisco its impossible?

[vinniepukh]

Insulated windows are possible albeit extremely expensive in SF.

They need to be:

1.) wooden 2.) vertically opening 3.) same style as the old windows

The windows the OP posted are 100% illegal since they do not fit the character of existing windows (wooden and vertical).