"Rookie-at-home" wrote in message
...
I've just bought a new (over 40yrs old) home. It doesn't have A/C and
it becomes very warm during the day (+85F)

I've installed screened windows & doors (to allow for circulation) but
it still becomes very warm. I think the attic (crawl space) is
trapping heat. I don't have any exterior ceiling ventilation except
for soffit vents.

If not this, what else could be causing the heat to build up? How
best to fix?

Keep the sun out. Close the curtain, or blinds on the sunny side of the
house. Long term, plant shade trees, but it will take 10 or more years to
reap the benefits, but they can be considerable. Close windows or door that
are letting in the hot air from sidewalks or driveways. Vent the attic.
When the outdoor temperature drops, use a fan to draw the cooler air in and
push the hotter air out.