The message
from "dennis@home" contains these words:

In the real world you have to take into account the heat capacity to work
out how long it takes to reheat the house, not the heat loss. I.e. your
simple model doesn't work.

Time is not really an issue unless the heating system is inadequate. It
is the quantity of energy required to reheat the house that matters and
that depends on how much has been lost.

--
Roger Chapman