Abri - open or closed

[plod]

Anybody have any ideas whether the water warms more quickly with the abri open or closed when the sun is shining strongly?

[Just Chris]

The water warms considerably faster with the abri closed in our experience.

With it open, breezes across the surface continually cool the water which evaporates into space.  With the abri closed, any evaporation condenses onto the plexiglass when the outside temperature cools overnight.  Also, of course, the water retains the heat overnight with the abri closed.  We also experienced the water getting too warm last year (32 degrees), so to regulate temperature we open and close the abri at intervals.  On really hot days it gets too warm under the abri anyway, so pushing it back and swimming in the open air is much more pleasant.

Chris

[plod]

We always have it closed at night, but I had it open to clean a few days ago when the sun was out and it seemed that it warmed up appreciably. Might be just a feeling and I have no scientific basis for it.

[oliveau]

I generally keep mine closed, as it reduces heat loss from the wind, and keeps the dust and muck out. However, when it's really sunny I tend to open a couple of panels about 6" to reduce the condensation, as i think the water warms better if the plexiglass is clear.