In article ,
"Ron" writes:
Hi I have a digital thermometer that has a sensor on the end of a long wire,
and can be switched to read the temperature of the sensor or the temperature
unit. If I put the sensor up the loft what would be a resonable temperature
difference between the room and the loft?

I.e I could use it to monitor the effectiveness of the insulation. At
present there is a difference of 2 degree centigrade however there is no
heating switched on at the moment.

I don't think that temperature difference alone will tell you
anything useful -- there are too many other variables in the
equation. If you say what the insulation is, how thick, and
the ceiling construction, there are various tables which will
allow you to calculate the U value.

Infra-red thermometers (look like small radar speed guns) are
better for searching for heat loss. You can check ceiling
temperatures and check for cold spots, which are where you
are losing heat (or from the outside of the heated area, check
for warm spots). I did this on a bitterly cold day. Most of
the ceiling was something like 22C (hotter than the average
room temperature because heat rises and it's insulated), but
the loft hatch was below 10C IIRC, as it had no insulation on
the back of it. This isn't a practical proposition with
temperature probes as they can't so easily measure things
like wall and ceiling temperatures.

--
Andrew Gabriel