Adding insulation hopefully will fix the AC issue

My boyfriend bought a rental property and that is all he wants to talk about.

Unfortunately his property is a total hunk of junk.

He has to make a lot of expensive repairs. In order to save money, he is doing it himself. The biggest issue is that the roof with the house has pitiful amounts of insulation. Apparently the air from outside can leak into the house easily. In the winter it is freezing cold and in the summer it is sweltering. Since it is August, everyone has been complaining to him about the air conditioner not working well. My boyfriend thinks if he fixes the insulation, the AC will be fine. Right now all the air the cooling system produces is leaking outside. How can the air conditioner expect to achieve the thermostat setting? Right now the tenants are dealing with 80 degree indoor temperatures. It is easy to blame the AC for not working right. I am hoping that after the home becomes air tight the cooling system can achieve whole home temperature control. If not, the tenants are right and the AC system is the problem. My boyfriend then will have to take it apart, clean it and deduce if there is a repair. He might even need to call a professional cooling business to give it some love. Who knows though. Perhaps the issue is more simple than I think it is. Maybe the August weather is unusually hot and no cooling system can keep up with it. So adding new insulation and cooling tune up is not necessary.

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