We have noticed a very significant decrease in site speed with each new blog post or K2 item that is added. When evaluating the home page of the site using various speed performance analyzers (such as Google page speed insights and Pingdom), we noticed that K2 images are being loaded or are contributing to the page load time even on pages that contain NO K2 Content.

Is there a reason all our K2 images (in media/k2/items/cache directory) contribute to load time even on non-K2 pages?

The site is Joomla 3.5.1
K2 Version 2.7
PHP 5.5.30

Update:
Disabling all K2 items in the Extension manager brought the Google speed test score from 40 to 77; Pingdom reported a 19 second decrease in load time and 7.8mb decrease in page size when K2 was disabled (both measuring the home page which contains no K2 content).

Can you elaborate further? Perhaps with screenshots?

I just evaluated a new site under development via pingdom with dozens articles all with large main images - only the image for that article was loaded.

When I evaluate the home page via Pingdom, the result returns 445 requests, many of which are K2 images in the directory /media/k2/items/cache. In the screen shot (imgur.com/Jgq8mWd), you can ID them by the "_S" in the filename. However, none of these K2 images are on the home page in anyway.

Similarly, if I run another, non-k2 page (www.savoirfaire-us.com/savoir-faire-services/digital-marketing/seo) through Pingdom, I have 396 requests (and a load time of 24.6s).

When I turn off K2, these pages have load times of 2 to 2.5 seconds.

For some reason, the site is slow and is making requests for images that belong to K2 items that are not even on the page.

I've just tested on a few more K2.7 sites on non-k2 pages and have not been able to replicate.

But you've loaded a module that has classes 'k2ItemsBlock k2ListsModule' on that last link you sent.

It's responsible for the majority of those images being loaded. It looks like it's got an override applied too.

So my guess is you have a module you're using that's loaded on all pages, but because it's being loaded in an off-canvas position, you're not seeing it on the page.

In fact, it's your blog archive module.

When I force your offcanvas to display, you see this:

www.dropbox.com/s/mvyrp8rofvmf4fi/Screenshot%202016-05-24%2010.00.04.png?dl=0

Note the super-tiny inset scroll bar.

Also, if this helps:

www.dropbox.com/s/xslfqmbvwixo8jy/Screenshot%202016-05-24%2010.01.50.png?dl=0

A HUGE HUGE HUGE THANK YOU! I have no idea how that got published to that module position (unless one of my content people did it)! You saved me from my client wanting to switch to WordPress.

A pleasure mate :)