Your right I should use my reading glasses when I use a Psychometric Chart.
At 37 degrees the glass temperature reaching dew point is more likely. Dry
bulb wet bulb temps with my background were use to calculate superheat or
For the 1st year, there will be excess humidity in the building
materials in the new house ... it'll likely calm down about in the 2nd
year ... that was my experience. In the meantime, if you don't have
power ventilation, you'll have to make do somehow ... crack a window
open maybe. In my case, the new house attached to the old house, so I
put an opening at the top of the adjoining wall letting that excess
humidity go into the dry, leaky old house next door ... an excellent
The colder an environment, the more noticable the mositure of new
construction. Ventilatiojn schems like an HRV will work overtime the
first winter after new construction in a cold climate. The next winter
they can over ventilate to the point people want to add humidifiers
Not yet, but the good news is that the problem is gone. Here is what I
I had my wife circulate the air by opening the back door for fresh air
and put the fan "on" instead of "auto". By the time I got back from
work, I had to clean up the water but I haven't seen the problem again
for last few days. I also got two hygrometers, one analog and one
digital, and they had ranged between 35% to 42% at given moment. Even
with the wide range I think I was still at near "dry" condition.
I believe the main problem was the rapid drop in temperature in
addition to new construction in first winter. I took the reading in
bathroom when I took a shower and it was at 53% (highest). I ran the
bathroom fan for about 30 minutes and it went down to 33%. I think I'm
gonna use the fan during shower during winter.
There is a lot of moisture of construction in a new home, and a lot of
the energy efficiency windows may have what can appear to be high
R-values, but this tends to be for the centre of the glass. The frames
can short circuit a lot of heat and sometimes they may have metal
spacers separating the panes of glass. Metal frames would be just
asking for it.
U-shaped condensation patterns are common as the windows are a lot
colder around the edges than in the middle of the glass.
New homes can be fairly air tight, and in the winter the people can
become their own humdifiers, but this is more common in the North.
You may have to ventilate a lot during this first winter. Hopefully you
have bathroom fans vented to the outside. As an experiment try cracking
open one window and running a bathroom fan steady to see if the dry air
can drop your RH enough to stop the condensation.
Getting the glass warmer will help too. Try keeping the drapes open at
night, this keeps the windows a little warmer. Bay windows are always
the most prone to the condensation.
If running a fan during the cold weather does not lower the RH, maybe
check that you are not creating the moisture yourself. Lots of plants
being watered, simmering foods for a long time, hang drying clothes
inside the house etc.
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