Condensation BIG time on windows

I was inspecting several condominiums today in one complex and the windows condensate so much that there is mold growth noted at the side of the interior window framing. I looked at the AC and did the temp drops and they are acceptable. Humidity level within the house was at 51% and the temperature was 74 degrees. The condensation only occurs at the interior of the window. The windows are hurricane rated windows (thick) and the condos are about 4 years old.

The only thing I can think of is that there are cheap plastic blinds and the AC/Heat is pointed right at the windows and the when the heat or AC is activated it reached dew point, thus creating the condensation. There is no water staining at the windows at all indicating it is a leak from the exterior.

Could use some ideas…Now when thinking remember where i live is very different. I live in SW Florida which is almost a tropic climate. I gets to be about 75-80 degrees in the day and sometimes dips into the low 40’s at night. I can think of nothing else besides it reaches dew point and causes condensation.

Is there a cheap test for it? Like cover the window with plastic…something? Thanks for the help!

What type of windows? Single pane? Metal frame???

That was also my first though Joe, metal frame windows.

What temps did you have the night before and what time of day did you do the inspection? Was the condensation only on the metal framing? Pictures would help.

Also there are condensation ratings for windows also, meaning, what is their resistance to condensation. Find out what the manufacturer is and look up the specs.

Russell are they on the beach? What was the outside temp? If it was metal frames on the windows and they leaked air it could be due to condensation of exterior air being drawn through. Condos are notorious for stack effect depressurization even when little wind pressure is present they suck air out through vents that are common. This is the opposite of the ideal for our climate which would be interior pressurization with conditioned air.

I’m not using a pschrometric chart but going from a short cut I realized when doing IAQ work and commercial air balancing in the early 90’s.

With the indoor conditions you mention and no change in the absolute air moisture content, the dew point for that indoor air would be about 55 deg F, which the outdoor night temps fall below…so condensation would be expected on single pane glass /metal sash frames.

If you were there during the day when no one was home producing moisture, the indoor RH may even be higher in the evening due to after work showering, dinner cooking, dishwashing really pushing the windows to condensation.

They need to get rid of interior moisture by dehumidifying or venting moist air to the exterior hopefully to be replaced with drier air.

Yes they are metal framed windows. The owner stated they could feel a “draft” so the only thing I could think of on short notice was to get a hair dryer and blow it close to the frame and use thermal infrared and see if anything could be seen. The windows are single pane, but rather thich because they are hurricane rated tempered glass. With the blower on high, nothing was seen nor felt at the interior.

Dehumidifiying is what the HVAC systems here are suppose to do. They are electric split systems with a condensate drain line to the exterior.

I never knew there were condensation ratings on windows. Where would I find such info?

There is nothing practical that can be done to prevent condensation on metal frame windows in the winter. Move along.

Condensation ratings for windows? Any surface whose temperature drops below the surrounding air’s dew point can condense water. Metal frame windows are notorious for causing condensation because of their ability to transfer heat. If the outside temperature is below the inside air’s dew point, the window’s metal frame could drop below the indoor air’s dew point. The dew point of the air for the conditions you measured is around 59 degrees. I have a feeling that you could easily reach that outdoor temperature overnight in your area.

Air conditioning systems may help reduce indoor humidity levels, although not as efficiently as dehumidification systems. Further, the humidity-reducing ability of an air conditioning system varies depending on the air conditioning needs of a building. On the other hand, an over-sized air conditioning system can actually increase the humidity levels inside a building due to short-cycling of the air conditioning system. In a humid climates, such as Florida, short-cycling can really create humidity problems. You can sometimes tell buildings with humidity problems as soon as you enter them–they have cold, clammy air.

The way this problem is usually fixed is my replacing the windows with non-metal ones. Installation of storm windows might fix the problem; but that is a lot of money to put down on a questionable fix. If this problem occurs only part of the year, repairing it might not be cost-effective. That puts the ball in the owner’s court, or possibly the condo association’s court, depending on how it is set up. I think the best thing you can do is just call out the potential problem and site the metal window frame as a possible cause.

Thanks Matt…appreciate the input and the rest of the guys.