Hi there Currently doing reno for my resale 4 room HDB. Going to change all windows but was told that PE certification is required. Cost of engaging a PE about $3K plus. I have called up a few contractors, some say required, some don't. One of them who said it is required told me that it is due to the tempered glass panel at the bottom of the windows. A pic of my windows for ref: Anyone can advice? Thanks!