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.

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.

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.

Crawl-space insulation falling down, moisture building

Q.    We live in a home with a crawl space that is only about two feet tall. The insulation has all fallen down and sometimes we have a small area with a little water. We live just 3 blocks from the ocean and want to know what kind of insulation would be best for this situation.

We also have a lot of condensation in the attic. The plywood is wet and the nails drip water. Do you recommend a ridge vent? I would appreciate any advice you can give me as we are new to this area and don’t know what to do. Thank you.

A.    I assume that the crawl-space soil is bare and not covered with a 6-mil plastic vapor retarder. This is likely to be responsible in great part for the attic’s problem. It is also likely to be responsible for the insulation falling out between the floor joists; the paper vapor retarder holding it up may have rotted away.

I suggest you remove all the insulation batts. If they are in good shape and not soaking wet, and the paper vapor retarder is still sound, use them to insulate the walls of the crawl space. If they are wet and the paper is rotten, put them in heavy contractors trash bags and throw them away.

The first thing to do is to cover the crawl space floor with 6-mil plastic being careful to bring the plastic up the walls to the outside grade level. Since you have had some water seepage, install the plastic on the walls first by stapling it to the mudsill onto which the floor joists rest. Be sure that this plastic is wide enough to cover as much of the soil as possible.

Next, put another sheet of plastic on the ground from wall to wall, overlapping the plastic that is covering the walls as much as possible. This will prevent water from seeping onto the plastic where it cannot be absorbed by the soil. If the fiberglass batts are usable, staple one of their ends to the mudsill and let them hang down to the floor, bending them to cover the floor by a foot. Place bricks, stones or whatever you can find (except untreated wood) on the flat part of the batts against the walls to hold the insulation tightly. Use a stapler to staple the flanges of adjacent batts together.

But if the fiberglass batts are not useable, adhere 1-inch thick extruded polystyrene rigid insulation (blue, grey, pink or green, but no white expanded polystyrene beadboard) to the walls after cleaning them with a stiff brush. Apply daubs of StyroBond or polyurethane caulking to the concrete and press the insulation boards into the adhesive. Then staple plastic to the mudsill, covering the insulation following the instructions above.

Now check the grade outside and make sure it slopes away from the foundation.
Next, check for any convective paths from the living quarters into the attic and seal them up. If you can do the crawl space work and take care of any convection over the winter, wait to see what happens to the attic next winter after it has had a chance to dry over the summer. If you find new condensation, then more investigation will be needed to determine the best methods to ventilate the attic.

Dark line around rug next to outside walls

Q.    We have a house built on a cement slab about 4 to 6 inches above the ground at which point the vinyl siding starts. There is a dark line all around the edge of the rug that butts up against the outside walls. Is there a way to eliminate this problem? Vacuuming doesn’t cut it, and washing doesn’t seem to do much good either. Is it because the dirty air blows under the siding where it meets the slab and comes into the house with the dust?  Someone told me that we cannot caulk under the siding where it meets the cement slab because it would cause mildew. Is that true? When they put the vinyl siding on five years ago, I watched them wrap the house with Tyvek first.

I hope you understand what I’m trying to tell you; my description might leave a lot to be desired. Could we caulk from the inside before we get the new carpeting so we don’t repeat the same process with the new rug where it gets dirty along the outside edges? Or can we caulk under the siding on the outside to keep this dirty air from entering, if indeed this is what is causing it?

A.    Although it is possible that cold air is infiltrating at the joint of the concrete slab and wall framing, I think the most likely cause of the dark stain on the edges of the carpeting is due to the formation of mildew because the perimeter of the concrete is cold.

I see no reason why you can’t caulk the joint of the bottom plates of the walls and the concrete slab from both inside and out if there isn’t a sill sealer between them, as there should be. You should be able to tell if there is one by pulling the carpeting up along the edges and looking for it; it may be a black, shiny plastic covering cellulose; a strip of fiberglass insulation; a white or blue foam strip — or whatever is commonly used in your area. You can also check for air infiltration by holding the back of your hand or a lit candle as close as you can to the joint to see if you can feel cold air or see the flame flicker. Just be sure to pull the carpeting up and put something on the concrete to catch the drips from the candle.

If I am correct and the dark stains are caused by condensation and mildew formation because the slab is cold, the solution is to install rigid insulation against the outside of the slab. Dig down a couple of feet along the entire perimeter of the slab. Clean the concrete with a stiff brush, and water if needed; let it dry. Run a strip of polyurethane caulking or StyroBond at the top of the slab and put daubs of the same adhesive every few inches along the concrete all the way to the bottom of the excavation. Press in place a 1-inch thick rigid extruded polystyrene (Styrofoam blue board, pink Foamular or whatever is commonly used in your area).

Cover the insulation with half-inch thick pressure-treated plywood power-shot into the concrete or aluminum coil stock adhered with caulking or Styrobond, making sure that the insulation and its cover are properly flashed under the vinyl siding to keep water, dirt and other foreign objects from getting behind them. Backfill the trench, sloping the grade away from the slab and plant grass. An experienced carpenter should be able to do this easily.