Thread: Moisture on Windows

I received a call from a client indicating that when cold weather came and the furnace came on the windows in the house had moisture on them.

Description of House:
Small Cape Cod, sitting on a slab, no basement. The square footage is around 1200 sq. ft. The house has vinyl siding and a new asphalt roof.

Heating Unit:
Forced air with one large return air grill in the living room. Each room has one six inch round air diffuser in the center of the ceiling.

Ventilation:
There are four large roof vents and gable vents in each side of the attic. There are no soffit vents, due to the small size of the soffits.

Attic Insulation:
There is minimum attic insulation.

A heating and ventilation contractor recommend installing soffit vents and attic insulation. I tend to disagree as I do not believe this is the cause of the moisture on the windows. I feel that the heat is staying along the ceiling and not reaching the outside walls. Any help in this matter would be appreciated.

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What material are the window frames?

Patrick
You did not say if the windows are dbl or single pane glass.
Either way, moisture on windows is caused when the surface of the window glass is below the dew point.
To reduce condensation raise the dew point.
Most often the easiest way to do this is to remove some of the humidity in the house.

Very common to see condensation form on windows and frames especially aluminum frames. These were common with the round diffusers in the ceilings.

In my reports, I notify the clients that moisture will condense on windows and/or frames when they are single glazed or metal framed. I also see condensation on the double-glazed windows that have a narrow airspace. The windows with an airspace that is 1/2 inch or wider generally don't. However, we have a fairly mild climate and your mileage may differ.

But, an improperly vented furnace also cause excess moisture in the house.

Originally Posted by Patrick McCaffery

Ventilation:
There are four large roof vents and gable vents in each side of the attic. There are no soffit vents, due to the small size of the soffits.

Attic Insulation:
There is minimum attic insulation.

A heating and ventilation contractor recommend installing soffit vents and attic insulation.

I would let the HVAC person start with that, as I am sure you recommended additional ventilation and additional insulation in your report ... right?

I would hope so.

In addition to window construction you need to verify if there is a large moisture source in that home.

Did you get any readings on interior temperature and humidity levels?

They running any ventless appliances?

There is a combination of window material. There are newer metal windows and there are older wooden windows. The windows with the most moisture are the older wooden windows.
There is no indication of other sources of moisture.
The house was a flip and I am not sure what the previous heating system consisted of. I would suspect it was baseboard heat, as there is no basement.
As to the attic ventialation, this is a older cape code with 6 inch soffits.
I did not do the original inspection, I was called in as an unbiase third party.
As indicated the forced air furnace is in the center of the house behind the living room wall. The only return air vent is in the living room going directly through to the furnace.

Seems strange that there's enough moisture in the house to leave condensation on all windows. I typically run into problems in say bedroom and bathroom areas. I agree with DavidR that you need to track down the source of all of this moisture. If there are no ventless appliances in the home, could there be an issue with the furnace venting properly?

Is there a gas range with some crazy lady cooking all day long with no exhuast system?

Are there exhaust fans in the bathrooms, and are they used during and after showering?

Are there 3 families living in a small rental house designed for a single family? I see so many issues with rental houses that my first question would be "is this a rental"

Did you say if the glazing was insulated? The frames are somewhat incidental to the glass. Metal with no thermal break will certainly condense with a suitable temperature difference, but uninsulated glass will always condense.
But like was said earlier, there could be 10 occupant related reasons. I've seen occupants set the heat on 85 and wonder why the windows ran with water.

JLMathis

Typically when I see this I find the whole house humidifier is turned all the way up. Water stains and active drips are often see on the windows and sometimes in ceiling corners. Was there a whole house humidifier installed?