system
A chat on subreddit /r/NoStupidQuestions
human
My dad insulated our house while it was being built! It paid off for years
gpt
He's lucky.  A lot of contractors won't allow you on site to do your own work.  I imagine it's a liability for them.  Also, if you upgrade the insulation on your own too much, you run the risk of having an oversized HVAC system which could lead to problems like mold.

My friend was having a house built and he asked if he could install CAT 6 cabling.  The contractor basically said, "I can't let you do that but we get off work at 3pm."