construction

Matt Risinger covers installing a Zehnder ERV fresh-air system in a tight passive house, explaining balanced ventilation, the benefits of heat recovery and the costs involved.

A roughly 45-minute vintage US military instructional film that gives a comprehensive overview of celestial navigation, covering sextant use and the theory behind lines of position.

Tech Ingredients shows how to build flat panel speakers from exciters and foam board, with construction guidelines, measured SPL comparisons and a complete system playing music.