Moisture builds up after new windows installed

Q.  I live in a 40-year-old ranch and had new windows installed 3 years ago. Since they were put in a fair amount of condensation builds up within the house during the winter months. I run a dehumidifier to cut down on the amount of moisture build up on the windows but it still persists. The bottom of the windows have become dark with mold where the wood meets the glass.

Condensation inside new windows
Condensation inside new windows

Any suggestions on how to get more air circulation in the house to eliminate the excess moisture?

A.  Your old windows were quite leaky, allowing more air exchanges than the new ones. So moisture generated by your family and its habits (the number of people living in the house, the house size, length of showers, type of cooking, etc.),  water-loving plants, pets, firewood stored in the basement, clothes dried on racks, etc.) will accumulate and, when the dew point is reached on the window glass, condensation occurs.

You need to lower the inside relative humidity by changing some of the things that keep it too high. Ventilate the house often by opening windows on milder days, or run bathroom and kitchen fans for long period of time (be careful, though that the use of the fans depressurizing the house does not cause backdrafting of the heating appliance — this would draw carbon monoxide into the house.)

Or you can choose to have one or more room-size air-to-air heat exchangers, or a full-house one, installed.

Meanwhile, remove the mold on the bottom rail of the window sashes with a toothbrush dipped in a mixture of equal parts household bleach and water.

Condensation leaks from new concrete porch

Q.  We added a room and porch to our house last summer. The porch is covered and the room beneath it is heated. The porch is cement and the problem is that it constantly leaks water. I have 2-inch thick Styrofoam insulation on the ceiling of the room, but as soon as you touch the boards, water runs off. Is there any way to prevent this water (condensation) leak?

Also, the outside walls are split-faced blocks, which were painted red and over the summer white has run over the painted surface. I am not sure if this is from the mortar or the blocks. Can anything be done to prevent this from happening again if we re-paint the split-face blocks?

A.    If the concrete porch floor was poured onto a ribbed steel form, the rigid Styrofoam insulation boards cannot prevent condensation from forming. To be effective at preventing condensation, the Styrofoam would have to be glued tightly to a smooth concrete surface. The best solution may be to replace the Styrofoam with sprayed-on, closed-cell polyurethane insulation, unless you have a way to inject canned foam into the open slots until you fill them completely.

If the white you mention on the red-painted, split-faced blocks is powdery, it is efflorescence, and it is caused by salts in the masonry leached out by moisture, which leaves the salts high and dry after the water evaporates. Remove it with a stiff bristle brush. Solving the condensation problem may also eliminate this one if the excess moisture in the room is absorbing the salts and moving to the outside.

Water forms on new basement walls

Q.   Our new house has water on some of the basement walls. The builder says it is condensation from humidity. It is on the above ground portion of the concrete basement walls. Is this common with new construction?

A.    Yes, it is. Concrete exudes a lot of water because it requires about twice as much water to pour it in place for it to cure properly.

It takes one to two heating seasons for the excess moisture generated by the entire construction process to dry. In your case, the moisture appears only at the top of the concrete walls because it is colder above grade than it is below.

Painting over mold stains

Q.    We had a new home built and after we closed, we noticed spotty areas of mold on the ceiling of our unfinished basement. Either the wood used already had the mold on it or it occurred during the construction process when they closed up the basement without adequately drying it out. The builder was pretty responsive and hired a mold remediation company to clean it up. After they completed their process we were left with “mold stains” on the wood. It is a year later and there is not further growth. Should we paint these areas? We do not want any problems selling the house in the future.

A.    The mold developed because of the high level of moisture exuding from the concrete and other components of the building process. You are fortunate in having had a responsible contractor who took care of the problem. You certainly can paint the basement ceiling to make it more attractive. Prime first with a stain blocker like B-I-N.

Ice forms inside of storm door

Q.    I purchased a storm door and had it professionally installed last summer. My problem is on snowy or frigid days, a sheet of ice forms on the inside of the storm door. I looked at the neighbors storm doors and no one else has this problem. Also, on occasion there is condensation on the inside of the storm door that I dry with paper towels. Would you have any suggestions?

A.    The problem you have is usually caused by the storm door being tighter than the primary door. You should allow some air leakage around the storm door by adjusting the bottom weatherstripping. Or you could increase the weatherstripping of the primary door.

Heating and ventilating a finished basement

Q.    We have done some renovation in our basement. We have installed a washroom, created two work stations, and left an open space for other recreational purposes. We have also enclosed an area that has the water tank (we have well water and septic system) that is used for the storage of pots, pans and other miscellaneous items. We are faced with two major concerns and seek your advice on the following:

  1. How do we provide ventilation as well as heat to the basement area? (No vents were installed at construction.)
  2. The walls of the storage area that was Sheetrocked and painted has begun to mildew and it is spreading over most of the base of the walls. What corrective action is recommended to cure this problem?

We should add that although this storage area had no vents, prior to the installation of Sheetrock and painting, there was no seeping or visible water marks on the walls in the area.

If you could provide your expert advice on how we could handle the concerns mentioned we would be very appreciative.

A.    You do not need ventilation in a basement; opening windows in summer would create a bad moisture problem.

Heat should be provided with an extension of your present heating system. If you have a hydronic (hot water) system, a separate zone for the basement is the best solution. If you have a warm-air system, heat ducts should be installed properly (not simply cut out of a main in the basement). Ducts should be run down to the floor with multi-directional grilles. An experienced HVAC contractor will know how to do this.

Mildew that has developed at the base of the walls tells you that you have a very high relative humidity and you need to operate a dehumidifier in the warm months of the year. Select one with a large enough capacity to handle the cubic footage of the basement and keep all doors to the various spaces open, but if this is not possible and you need to keep doors closed to some of the spaces, you may need more than one dehumidifier.

Condensation from bathroom vents

Q.    We have been frustrated with water leaks that have stained our ceiling for about two years. The house is 20 years old, 2-story with finished basement. The roof was replaced about three years ago. At that same time we decided to create additional usable attic space with access from the second floor and plywood on top of the blown insulation. We vented the two upstairs bathrooms and dryer to the outside rather than into the attic as was present when we purchased the house 10 years ago.

We believe that we had initial problems with flashing but the handyman who helps us has corrected that problem. Additional leaks this winter have been traced to excessive condensation in the vent pipe rather than from the roof. A note: Several members of the family love long showers (as long as 20 to 30 minutes) and so the amount of steam from these showers is substantial.

The exhaust fans for the two bathrooms were tied together into one roof vent. Our only solution this winter has been to disconnect the vents and put them into a bucket in the attic that we empty every four to six weeks (with two to three gallons of water). With this temporary solution for the winter we have stopped additional ceiling stains.

How do we prevent this problem short of limiting shower duration? We have considered the possibility that a horizontal vent may lead to less condensation but don’t want to spend the time and effort on that solution if this will not correct our problem.

A.    From your description, the bathroom vents were terminating through the roof. So condensation would run right back into the ceiling, usually where the fan is. Tying two bath vents into one is a mistake. What often happens is that the moisture generated in one bathroom returns into the other one, especially with a near vertical installation. You have temporarily solved the problem by disconnecting the vents.

The best solution is to replace the vents with schedule 20 drain pipes (one for each bathroom and with the bell ends toward the fans). Keep the pipes as close to the attic insulation or floor  as you can but give them a slight slope to the outside by using small wood blocks of decreasing thickness.

Terminate them through individual hooded aluminum or plastic wall jacks, preferably on the south side of the house if it is the shortest run. Avoid louvered plastic jacks, as they are prone to breakage. Snug fiberglass batts on each side of the pipes and place another set of batts on top. Properly insulated, condensation will be reduced and drain to the outside.

Moisture from basement of new house

Q.    The foundation of our house was built last November, and the house is now complete. There is water on some of the basement walls. The builder says it is condensation from humidity. It is on the top of concrete basement walls for the above-ground portion. Is this common with new construction?

A.    In this case, I agree with your builder. There is a lot of moisture in a new house, particularly in concrete, which is poured with twice the amount of water it really needs for curing. This additional water is needed to make the concrete workable.

Your house was built over the winter and the condensation manifests itself on the coldest parts of the concrete – those above ground. The condensation should clear as the weather warms up but keep in mind that it often take a couple of heating seasons for all the moisture from construction to evaporate. Do ventilate as much as possible.

You didn’t say where your house is. If it is in an area without air-conditioning and you rely on open windows in summer, it may even take longer as the very moist summer air is not conducive to much evaporation.