For those who are building and considering the pluses and minus of air conditioning (A/C) installation in your LIVP, let me contribute my experience.  When I was building, I got to the point when adding one more system (ex, A/C) represented more work, longer delays until flying, more money, more weight, and more hassles.  I justified my decision not to install air conditioning based on ambient temperatures at altitude, efficiency of the third intercooler, where I expected to fly, abilty to divert warm turbo air prior to pressurization, etc.  In the end, these were not good reasaons to defer the A/C installation.

When I started flying I realized the temps entering the cabin where uncomfortably high if ambient temperature was >50*F, the solar heating inside the cabin is significant, the comfort of non-pilot passengers (who tolerate much less inconvenience) was compromised by added cabin stuffiness, and ground operations prior to reaching cooler outside air was really steamy at times (helped somewhat by opening the door a crack, despite the tornado of air).

I installed an A/C after the first year (details available separately), and must now acknowledge that it is a very important comfort item in the plane.  Passenger comfort, pilot comfort, ground operations comfort, cruise comfort, sunny days and overcasat day comfort, even winter comfort when clear skies and solar heating exceeds personal minimums.

So, for you builders who were like me, I encourage you to take a page from my retrospective lesson book and consider installing the A/C while it's easier, while the engine and airframe are not finished.

My contribution to the heritage of experimental builders.

Jeff Liegner
N334P