Condensation on exterior stone patio
Txhome
| Posted in Energy Efficiency and Durability on
This may be the wrong area to ask this, if so, sorry. But, I live in North Texas where the temperature can swing from significantly from day-to-day and the humidity can sit at around around 70% with very little wind.
The problem is it creates heavy condensation on my 3 sided smooth stone tile patio. I don’t have problems with freezing temperatures creating ice. But above freezing the water creates a major problem when trying to walk on the surface. Lots of slipping around. I have a fan that helps but I’d like to try and prevent the the formation.
Any suggestions? Thanks in advance.
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Replies
V Larson,
This type of condensation happens whenever you get a spell of warm, humid weather after a prolonged cold spell. I noticed the phenomenon recently on my garage slab, when the weather warmed up after a hard freeze.
In theory, you could limit the phenomenon by installing a layer of rigid foam between the stone tiles and the substrate. The foam insulation would keep the tiles warmer, and separate them from the cold ground below. But I don't think such an expensive solution is worth implementing.
The ground in N TX isn't really all that cold, and the near-surface dirt under the slab will be about the same temp as the weekly average outdoor temp, which is almost always above the overnight dew point. (The deep subsoil temps are in the 60s, and after a long summer the temp a foot or two down is probably north of 70F.) Insulating under the slab is likely to make the problem worse, not better.
In TX it's more likely that the dew is caused by the surface of patio slab becoming colder than the night-air by radiating it's heat to the (radiationally cold) night sky, not conductivity to the sub-soil. An awning/shade over the patio would likely limit the amount of dew on the patio- the dew would form on the radiation-cooled awning instead, and at least some of the heat radiating off the slab would be reflected or re-radiated back to the slab.
It's pretty common for high-emissivity roofs to drop 5-10F below the ambient air temperatures on those clear nights that create the big diurnal swings. The patio presents a higher-mass version of the same issue. Were it a more porous/absorptive type of stone you may never see liquid water on these heavy-dew nights, but that could probably be tested with a few square pieces of sand-stone or limestone laid atop the patio. You could also test the proposed thermal-isolation with foam solution using a square of the same stone laid atop a piece of foam placed on the patio. Stone sealer treatments to protect against staining would likely aggravate the problem by limiting the rate of capillary draw of dew into the stone.
I thought there were some concrete/stone sealer products that were marketed as a 'slip reduction' application?
I have walked on some sidewalks in the past that looked shiny/glossy - and had a very odd, super grippy feeling in front of some commercial buildings in MN.