On 05/12/2014 22:13, Andrew Gabriel wrote:
In article ,
john t west writes:
Looking at how some people are protecting their Green Houses against the
frost, i was surprised how tiny the flames were on the paraffin heaters
in the green houses. They were hardly giving off any heat at all.

I was told its not about the 'Heat', but the fact that the flame changes
the 'relative humidity' in the air'.

Could anyone explain fairly simply, how this actually works? Thanks

In a slightly different context, someone I know has a large garage
they want to use for storage. As expected for an unheated detached
building, anything left in it gets damp and rusty, even though the
building is watertight and the building fabric itself isn't damp.

I have been running an experiment for over a month now, recording
the internal temperature and humidity, and the outside temperature
and humidity, to try and understand why things get damp in an
outbuilding. I have also added some heating, and what surprised me
was how little heating is required to reduce the relative humidity
inside the garage by quite a bit. I found it quite simple to control
a heater to limit the internal relative humidity to, say, 80%, but
I don't know if this is low enough to prevent timber and furnishings
getting to smell damp, or steel from rusting (or even if controlling
the max humidity is the right thing to do).

When I have more data and understand more of the relationships
between the various parameters, I'll write a blog on it.

The heater I use is a 1kW oil filled electric radiator (what I had
to hand), reduced to 500W by half-wave rectifying the supply to it.
I haven't analysed the figures in detail, but at a quick glance,
it's running with a 30% duty cycle when outdoor humidity is almost
100%RH, which is going to be around 150W equivalent. In comparison,
a gas pilot light is about 250W, and I'm guessing the parafin flame
is going to be in this same ball-park.

For more than a year now most of my downstairs furniture has been out in
my unheated barn/garage/workshop which is attached to my house. The barn
has damp wall and several minor roof leaks most of which don't get past
the upper floor. Tools do go rusty over time so I thought I would check
the current RH. Surprised to find it was only a fraction over 70%.
Outside is currently 89% and has mostly been in that region for more
than a month. Unfortunately I have no previous data so can't tell
whether that just happens to be an abnormally low reading.

The main reason why the furniture has been out there so long is that
what started off as a relatively minor house refurbishment the principal
part of which was replacing a damp concrete floor has now turned into a
major financial disaster the root cause of which was the unexpected
necessity of replacing all the roof timbers, and I do mean all, and then
installing a loft where there was no loft before so that the roof could
be insulated to something like modern standards. And yes I do have a
completion certificate for the roof.

The spare bedroom that I used to use as a drying room was always a
little damp and had a dehumidifier to keep the RH down to 70% was at 50%
RH when I moved the meter to the barn this morning. Oh yes and the bad
smell which I always thought was due to the unwashed clothes that also
lurked in there has gone as well. That end wall was obviously a lot
damper than I had previously thought even though only about 1 foot
projects above the attached barn's roof line.

Anyone know where I can dispose of some really manky old oak beams for
money? They must still have some strength left as they were supporting
20 tons of Yorkshire stone slates.

--
Roger Chapman