How Should You Insulate Your Attic?

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:

  1. The attic is the hottest part of the house in the summer and is cold in the winter
  2. Hot air rises up to the attic / cold falls drops into the living space
  3. Moisture rises and accumulates in the attic
  4. Central heating/AC systems and ductwork are often in the attic

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Why Doesn’t My Mini-split Heat Pump / Air Conditioner Work?

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!

Here’s what’s going on…

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Why do I have moisture in my walls?

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
  • The wall was built during a humid summer

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Attic insulation problems and solutions – Part 2

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!

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April showers bring May flowers, August storms bring…roof leaks!

Summer rains bring flooding

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:

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Ultimate attic insulation

Icy roof deck, not a good sign!

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!

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The best way to insulate your attic – part 2

Wow, where's that hole go?

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