A few months ago I got my hands on a NetAtmo weather station. (link) I had it setup and running for a few months now at home and its great. Both my wife an I use it constantly (especially when its really cold and really hot). I then came across a blog post from PRTG (link) where they wrote a little sensor application (PRTG NetAtmo Sensor Download) to gather NetAtmo weather stations data and record it into PRTG.
Its an easy install and setup just follow the guide and you can be up and running in 5 minutes. You can then setup custom thresholds for temperature, humidity, CO2 and levels of noise (or lack there of if things are too quite in the server room???)
What also handy is that you can add additional modules. So if your a small business or a large corporation that want to monitor physical environment of your remote offices and server room this is an easy and solution to build and then monitor.