I received an excellent question today, in a nutshell it was: “Why is my house so humid that condensation is dripping from the ceiling?”
The questioner reminded me of all the times I’ve heard this question, both on this blog and when I was in the field, helping track down issues in people’s homes. Clearly this is serious issue that needs more attention because it leads to problems with a home’s health, comfort and efficiency – exactly the things I focus on! (I also wrote extensively on this in a previous article: “Cathedral Ceilings – Mold and Moisture”)
One of the hottest topics in energy efficiency and building science is “how should you insulate your attic?” Why? Simply put, the attic has more impact on your efficiency and comfort than any other single part of your home!
Let’s summarize why the attic is so important:
The attic is the hottest part of the house in the summer and is cold in the winter
Hot air rises up to the attic / cold falls drops into the living space
Moisture rises and accumulates in the attic
Central heating/AC systems and ductwork are often in the attic
I recently had an interesting question – a reader asked what could cause a Fujitsu mini-split air conditioner to cause the air to become *more* humid. In fact, they noted that the air became highly moisture laden and the house was just yucky humid.
I really scratched my head on this one because, from a physics standpoint, under “normal” conditions, this is impossible with a mini-split. Why? Because a mini-split system has an air handler unit in the house with the only connection to the outside (and outdoor humidity) is through a small hole in the wall where the electrical and refrigerant lines run. And yet it happened.
The questioner noted that multiple units were involved and that various parts of the electronics had been changed, and yet the problem persisted. He noted that he’d heard of a number of other people with the same problem. I admit, I was baffled!
Then it came to me. In fact, I had worked with an associate, helping them to track down this exact problem. While I can’t state with 100% certainty that the problems were the same, the symptoms are the same. In addition, I realized that my own home’s systems exhibited the same issues, but I automatically made the adjustments to make the systems work properly!
The inside of a wall filled with entrapped moisture
I just received a question that was too complex to answer quickly, and so interesting that it deserves an entire post. Unfortunately, it represents a situation that occurs far too often.
To summarize, the question came from a reader who opened a small hole in their wall and found condensation on the vapor barrier at the inner surface of the wall. The question is, what could cause this?
Here are some more clues:
The moisture was observed during the winter
The hole was cut in a south wall
The home has 3″ foam board sealed to the exterior wall
A 2×4 framed wall was built inside this wall and insulated with Roxul
A 6-mil poly vapor barrier was then applied just behind the inner sheet rock
They did not measure high moisture towards the outer wall
Fiberglass insulation against roof deck plus moisture = roof failure
In the first post, we looked at how adding insulation could lead to frozen pipes if the insulation was put in the wrong location. But, just like a sweater, if you put everything you want to be warm inside the insulation, you can keep your house and pipes happy and energy efficient.
This time, we’re looking at how to install insulation properly so that you don’t rot out your roof. Unfortunately, the photo above shows how not to insulate under your roof!
There’s nothing like a gentle Springtime rain. But Summer often brings us torrential downpours, and along with them, roof leaks, incredible moisture and mold!
A few days ago, we had record rainfalls in Eastern Pennsylvania – five inches of rain in some areas. This fortunately came after an extended dry spell, so the rivers didn’t flood this time. We got really lucky.
These heavy rains often bring high winds, fallen branches and roof damage. Sometimes, they’ll just lead to enough leaking for you to notice. Maybe there’s a discoloration on your ceiling or window jamb. Whatever the sign, please pay attention. Failure to deal with a “small” leak now can lead to thousands or tens of thousands of dollars of damage to your house later. Worse, the accompanying mold can pose a severe health/allergy risk.
When dealing with leaks, you need to take several steps in order to minimize the chance of more serious damage to your home:
In the first two posts of this overly wordy series, we saw a few ways to insulate an attic while avoiding some of the worst problems that can lead to moldy, rotten attics and roofs.
If you recall, the big problem is that moisture from the house rises up through the walls and all the little cracks around light fixtures, hatches, wiring, and the moisture condenses on cool surfaces. Over time, this will lead to mold growth and potentially, rotten roofs.
How do you know if you’ve got a problem? I’ll give you a hint – if you have ice forming under your roof like in this picture, you had better do something before you have to replace your roof!
In the first installment on attic insulation, I discussed why it can be dangerous to add insulation to your attic without air sealing the attic floor first. Moisture can slip through tiny cracks in the attic floor and lead to rotten roofs. Given this information, we walked through the process of finding and sealing all those insidious air leaks in your attic, some easy, some difficult. But finally, after fixing all these problems, you could lay more insulation down on your attic floor, more confident that doing so wouldn’t lead to a humid, moldy attic.
But what if there’s an easier way?
Whether you’re building a new house or retrofitting an older one, you can make life much easier on yourself by using professionally applied spray foam insulation that air seals and insulates in one shot. There are two ways of doing this, each with their own benefits and disadvantages. We’re going to review both methods. One is spraying foam on the attic floor, instead of using loose fill or batt insulation. The other is spraying foam under the roof deck. Continue reading →
Signs of moisture and air flow in fiberglass insulation
When you climb into an attic and see this, you know something is seriously wrong. In fact, if your home isn’t very old, your insulation should be clean like when it was installed. The reason you get black insulation like this is because air and moisture are moving through the insulation, and it’s acting like an air filter.
The reason I’m showing you this picture is because it’s an example of the wrong insulation being used for a job. I feel pretty strongly about this because I’ve seen numerous homes where fiberglass has been installed in open walls like this and in almost every case, the insulation was seriously compromised – it was buckling under its own weight or simply falling out of the wall cavity. Or, in cases like this, it was hiding a big hole in the wall that should have been air sealed.
Let’s walk through the different insulation types and compare their main attributes: R-value, ability to reduce air movement, suitability for retrofit applications, and other characteristics.
If you saw smoke coming from the wall, you’d call the fire department and evacuate the house. So why, when you see water dripping from the ceiling, do you put a bucket under it, and let it destroy your home just as surely as the fire would, just more slowly?
This is just a quick thought for the day. Water can be extremely damaging, but it seems so innocuous that people often ignore it until it destroys their home or their family’s health. Take every drip seriously – imagine that each drip is a puff of smoke coming from a hidden fire.