Category Archives: Mold & Moisture

How to Install House Wrap around a Window

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Proper flashing detail around a window

Proper flashing detail around a window

When I head out around the countryside, I am frequently dismayed by all the examples of improper construction techniques. “There’s another house that’s going to rot out in a few years” I think to myself.

So, when I saw this new construction, I did a double-take. Did the contractor actually properly install the house-wrap (Typar or Tyvek) around the window? Amazing!

Let’s look at what they did right:

  1. They used Typar house wrap which is generally a better product than Tyvek. But installed correctly, each can do a fine job
  2. They installed the house wrap horizontally in long, continuous segments. This reduces the number of seams, which are potential failure points.
  3. They used the Typar tape for the seams. This is a little detail that is often missed. The house wrap is slippery material and using the wrong tape on the seams can lead to failure. Only the factory approved brand should be used whether it be Tyvek or Typar.
  4. *IMPORTANT* They sliced the wrap above the window and installed the top piece over the window’s nailing flange. This directs water properly. 90% of the installations are done without this detail which leads to water getting under the nailing flange!
  5. *IMPORTANT* They taped the wrap under the nailing flange and over the bottom sill. Again, this is critical for proper drainage. If water gets behind the window, it drips onto water-impervious Grace Vycor then drains out at the bottom flange. Most installers tape the bottom flange to the house wrap which traps water inside the wall.

So kudos to the builder. This home is much less likely to rot out than 90% of the other new constructions!

Why do you get Icicles on your roof?

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Icicles can do real damage to your home

Icicles can do real damage to your home

Here’s a winter quickie – icicles are a sign that snow is melting from a hot roof rather than a sunny day.

Since we’ve been talking about DIY energy audits, this is one of the easiest ways of seeing if you’re losing too much energy out your roof. If you’ve got lots of icicles or notice the snow melting unevenly, usually in vertical strips, then you are almost certain to have some major energy loss. Often, this can be fixed quite easily since the icicles and snow melt will tell you where the heat loss is. In fact, this works at least as well as the expensive thermal camera that we use in energy audits. I call it the 30 second energy audit! Continue reading →

Why do I have condensation in the middle of my windows?

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A Sure Sign of Collapsed Glass

Collapsed Glass Syndrome

I was recently visiting my brother and he pointed out a strange condensation effect he was having on some double glazed windows. Condensation formed in an oval pattern in the middle of the windows. This is really strange because condensation forms on the coldest parts of windows first. Thermal windows usually insulate best at their centers so condensation starts forming at the edges. But these windows were showing exactly the opposite condensation pattern as shown in the photo above.

Continue reading →

Insulating Basement Crawl Spaces

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Spray foam on crawlspace walls

Crawlspaces – those nasty, damp, moldy spaces under your home that you dread entering. They’re one of the least understood parts of a home and the source of countless problems. In this post, I’ll review some of the worst problems and how to avoid them.

Crawlspaces often have two big issues:

  1. Water / moisture – leading to mold and wood rot
  2. Cold / drafty – leading to uncomfortable conditions and wasted energy

Continue reading →

How NOT to insulate your house

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Sometimes insulation hides bigger problems.

The other day, I was talking with a friend of mine – an energy auditor who was a builder for decades. The topic came around to bad advice that “experts” give about insulating. It’s something that we both feel passionate about because homes get ruined and people get sick when innocent people follow this bad advice. We both adhere to a similar do no harm philosophy of  “if it’s worked for decades as-is, don’t mess it up!”

There’s a science to building and the tighter and more energy efficient you make a home, the more important it is that you do things “right.” It’s like the difference between making a log raft and a submarine. A log raft is leaky, but it’s forgiving because it floats by virtue of the logs. It doesn’t have to be water-tight. A submarine had better be water tight and structurally sound or you’re going to drown and get crushed by the intense pressures of the ocean.

Unfortunately, unlike boats and submarines, homes today are often built in the cheapest way possible, with little regard to physics. Renovations are even worse because people often hire unqualified “low-bid” contractors to do the work without realizing that the few thousand dollars that they save on construction may cost them tens of thousands to fix or even send them to the hospital due to mold or poor indoor air quality.

The problem is, people familiar with building science are extremely rare, as are the chances of finding a builder who knows how to make a healthy, energy efficient home. That’s why you’re here reading this now – you want to learn what not to do when insulating and how to do it right.

Continue reading →

Why do I have moisture in my walls?

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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

Continue reading →

Attic insulation problems and solutions – Part 2

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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!

Continue reading →