Zen Grid Framework version 4 (zgf5) themes are built to be fast.
A large amount of the zgf5 rebuild was focussed on creating a flexible and fast framework that was able to yield powerful page speed results more or less out of the box. Being able to create a fast and optimised website has traditionally been a complicated process with factors including server configuration, content and template optimisation being the major factors in determining how fast your site loads in the browser.