This question is under "Muskin Company" because we live in a Muskin home, but goes to all the other owners:

Has anyone else had difficulty controlling the humidity in their home? With the windows closed (summer or winter, no matter how humid it is outside), the relative humidity in our house rarely drops below 53%, even with the A/C on full blast. It's usually up around 60%.

When the temperature drops below 45º outside, we also get a tremendous amount of condensation on the window frames; so much so that water pools on the window sills and soaks into the drywall overnight, causing mold and mildew on the window sills (we had to have them sanded and re-painted this past summer, after just ONE winter in the home). I'm attaching a couple pictures of window frames/sills from last winter as examples.

We have a floor unit capable of handling more square feet than our house running at full power all day, and the relative humidity still stays at 50%. The only time it gets below 50% is when ALL the windows are open and it's less than 25% humidity outside. Obviously, that's not an option in the winter, and I want to address this before we go ahead and ruin all our window sills again.

Has anyone else had this problem? We've contacted the builder and River City Mechanical several times about this, and both of them say that our experience is normal. That can't be. I've never seen pooling water, or had such a difficult time getting the humidity down to a reasonable level in any house I've ever lived in.

Ben

This is what happens in Central Texas when you run the A/C so that it stays cold inside your home when it's hot as Hell outside. There shouldn't be much more than a 20° difference between outside and inside. Condensation is normal when the difference is much more than that.

What is what happens when you run the A/C? Running the A/C is the only thing that actually lowers the humidity, and we don't get condensation in the summer.

In the winter, we keep the heat at 67º.

Ben,

We had this issue last winter only mostly on the North facing 2nd level windows. Fortunately, not in the degree of causing warping and mold. I actually laid down a towel to catch the condensation to prevent any mold outbreak. We shall see what happens this winter. Incidentally, we've had no condensation this Summer. Our neighbors, the Ramirez's recently had mold and resealing of North facing 2nd level windows due to condensation. They were told it was due to improper sealing or lack of. You may want to ask if they are still having condensation issues.

I recently went on a construction tour and a builder educated me that aluminum windows (cheap and what builders are using now) were NOT a smart purchase due to the fact that they cause more condensation leading to warping and mold especially in the interior walls. Vinyl and wood are a better choice (more expensive), but would cut down on the condensation. A little condensation is normal though.

Marissa

We also have significant condensation in our house. The north facing second story during the winter and spring were the worst for us, too. Even though I made it a fairly regular routine to wipe up the condensation on the windows in the morning, we still had water/mildew/mold damage to the north window frame and sills.

I think Marissa is right about the window materials. In our previous 1950's era house, most of the house had wooden windows. In a room that was added later, aluminum windows were used on two sides of the house that also had wooden windows. During the winter, especially when the outside temperature dropped suddenly, lots of condensation would form on the aluminum window parts (which would then drip onto the wooden sill). Even though the whole house was at roughly the same humidity, we had very different results with different windows. It was quite rare for condensation to appear on the wooden windows, although it did happen from time to time.

Why? Aluminum conducts heat/cold very well. When it gets cold outside, the entire aluminum part gets cold, even the part inside your house. Some of this coolness transfers to your inside air in the immediate vicinity of the aluminum parts, cooling the air below the dew point (the temperature at which the water vapor in the air will condense). The more water vapor in your air, the higher the dew point and the more commonly you'll get condensation on even only mildly cool days.

One drawback of wooden windows is that they are very drafty. I don't think they would meet the Green Builder standards. Besides, just choosing different windows doesn't solve the the bigger problem. The water vapor is still in the house and can still lead to mold growth in walls, etc. As you move past 50 or 60% RH your risk for mold problems goes up quickly; the dew point is quite close to reasonable room temperatures. The only solution for this bigger problem is to reduce the moisture in the house. Per the link below, "It has been estimated that the typical family of four converts three gallons of water into water vapor per day. It takes only four to six pints of water to raise the relative humidity of a 1,000 sq. ft. house from 15 to 60 percent. "

It took some behavior changes on our part to get moisture under control in our house. We now use exhaust fans more aggressively (40 mins for shower, squeegee the shower walls after showering, always when using the cooktop), avoid leaving dishes soaking in water in the sink for extended intervals, cover pans of water while bringing them to a boil, close toilet lids, etc. We also bought a dehumidifier that we use to help from time to time, but be forewarned that dehumidifiers use power like crazy.

Lots of info:
http://www.fcs.uga.edu/pubs/current/B924.html

A handy chart of what generates how much moisture in your home on the last page:
http://extension.oregonstate.edu/catalog/pdf/ec/ec1437.pdf

Since I grew up in DC and Evan grew up on a bayou, we actually like humidity. But Miss Annette said my house was too humid, so I decided to pay attention.

It was 62% upstairs this morning. Alan and Bill attribute the problem to a combination of aluminum windows that promote condensation and the super effective insulation that keeps our hvac bills so low. So I opened three windows and now it is down to 46% three hours later. This is the lowest cost solution I could think of.

Now I just have to worry about Evan's allergies moving inside the house.

Well, I spoke with one of the chief inspectors at the residential building permit office… He said that there should not be that much condensation on the windows, even in a 5-star energy-efficient house. He also said that the HVAC system cannot have been designed properly (and the wrong types of windows were used) if the humidity is that difficult to control…

So I guess it's a bad design. I'll let you know what River City Mechanical says when they come out tomorrow.

I should have waited for Evan to get home. My post didn't get the whole issue. The aluminum windows are required by fire code because the GC houses are so close together. The firecodes and 5-star certification don't work together very well.

There is a third issue with air exchange in the AC system. We had ours fixed last winter. Maybe yours is still not exchanging properly and that would explain your levels of condensation.

I should have waited for Evan to get home. My post didn't get the whole issue. The aluminum windows are required by fire code because the GC houses are so close together. The firecodes and 5-star certification don't work together very well.

There is a third issue with air exchange in the AC system. We had ours fixed last winter. Maybe yours is still not exchanging properly and that would explain your levels of condensation.

I'm wondering if the seal in the windows in question might be bad. We moved here from an older home with single pane windows and had a LOT of condensation on the window sills there. We've had none of that here so that's what makes me wonder if the problem is the windows, rather than the HVAC.

I have little knowledge on this subject and am interested to know what you figure out.