call usoir come in and take a lock at this stuff. san francisco heritage which has their main office on goth. franklin street has a large library of preservation technology. the planning department has a library that effects this. there is a lot of resources available. >> on line. the planning department has bulletins on line. >> may an add briefly to that resource in san francisco. i'm on the committee of architectural heritage we are putting together lectures of old house issues. we go to homes with a certain problem and address that issue and how to fix it it's geared at homeowners that have these problems. >> we the building department issues weekly calendar of all trainings we can come up with in the san francisco area. we will post that on your training website as well. >> okay. question here? >> you are advocating fresh air for your buildings health what about the houses that have sealedat iings no gable vents that's trapped air and moisture. >> the building codes have almost always required vent laugz in your attics. there is