Legal Question in Real Estate Law in California

Re: Insulation rental law

Civil Code section 1941 et seq. are statutes intended to protect tenants from being stuck in leases for "untenantable" structures. 1941.1 is probably closest on point. It requires weather protection and certain working utilities. However, the weather protection and utilities requirements MAY stop at requiring rainproof and windproof walls and ceilings and a heating system capable of keeping all rooms at 70 deg. F. and delivering hot water at 110 deg. F.

I could not find any case or statute giving a tenant rights to cooling or insulation per se.

There are no doubt building codes specifying minimum "R" factor insulation for ceilings and walls, and probably some version of those codes was in effect in your community in 1975. However, it is far less clear that a tenant has a private right to enforce those codes against a landlord in a private civil lawsuit, or that a violation can be asserted as a defense to an unlawful detainer or rent-related lawsuit.

Finally, just because I couldn't find a case holding that a tenant can move out on ground of "untenantabiliy" when the interior temperature is 110 degrees doesn't mean a trial court couldn't so hold.

The Civil Code can be found on line at official and unofficial sites by using a search engine.