Daniel is wondering whether to install his own insulation batts in his ceiling. I did it once. I was young and fit. Now I am not young and fit, but regardless, I wouldn't do it again for other reasons.
I can't recall the weather at the time but I doubt I would have installed batts on a hot day. Nevertheless, the ceiling space was boiling hot. I had tried to seal my skin with clothing to prevent the 'itchys', when the glass fibres that float off the batts and get on your skin and irritate it. I also wore a handkerchief over my mouth to prevent inhalation of fibres.
R pushed the packs of batts up to me in the ceiling and I cut the packs open and the batts sprang out. It was easy enough to fit the batts where the ceiling space was large, but it was very difficult to get the batts into position around the edges of where the roof came down to ceiling level. Crawling in a roof with glass fibre batts is damn hard. Then there is always the risk of missing your footing and plunging a leg through the ceiling. Although I had a lead lamp suspended, there were lots of dark areas and if I was between the light and where I was going, my body blocked the light. Professionals would have removed roof tiles to get the batts in and provide light.
So, it was damn hard work but the worst was yet to come. My clothing did not prevent glass fibres finding their way to my skin and I believe they cause tiny but invisible cuts in your skin. I can't remember how long the itching took to stop, but it was not pleasant at all.
The insulation made a big difference to the interior of our house and the heating and cooling needed but I would not recommend an inexperienced amateur to install their own home fibre batt insulation.