Frost in the Attic Has an Obvious Cause
If you've ever seen frost in the attic in winter, it's pretty to easy to understand why it's happening. It's the same thing that causes morning dew on the grass, frost on the exposed half of my car, or water…
moisture
3 Important Facts About Dew Point Temperature
That photo above is the bottom side an air conditioner in a crawl space on Hilton Head Island, South Carolina. Those droplets tell us something important: A property of the air in that crawl space aligned with a property of…
When Is the Humidity Low Enough to Open the Windows?
Relative humidity is such a confusing way to talk about moisture in the air. I've been hammering on this point for a decade in this blog, covering it in several different ways. (See the related articles below for more.) But…
6 Options for Ventilating Homes in Humid Climates
Ventilating homes in any climate has its challenges. In Duluth, Minnesota, it's the extremely cold weather in winter, which leads to extremely dry air when you bring it indoors. In Phoenix, Arizona, it's the extremely hot weather in summer, which…
Why You Probably Need an ERV, Not an HRV
One of the most frequently asked questions regarding the type of balanced ventilation devices known as the energy recovery ventilator (ERV) and the heat recovery ventilator (HRV) is: "Can I get that in red?" OK, not really. Everyone knows that…
Measuring the Efficiency of a Room Dehumidifier
A few months ago, I wrote about the confusing world of dehumidifier capacity. That quantity tells you how much water a dehumidifier will produce in a given amount of time. Here in the US, we use pints per day, but…
Condensation on Storm Windows: A Lesson in Condensing Surfaces
It's been muggy in Atlanta this week. We've had dew point temperatures in the low to mid 70s Fahrenheit. I live in a 60 year old house, so the combination of high humidity and air conditioning can mean condensation. Currently…
Building Science Term of the Week: Ratio Rule
The purpose of my Building Science Term of the Week feature is to provide a basic definition of a term you may have heard without going into all the whys and wherefores. Last week I probably went a little overboard…
An Insulated Sheathing for Building Enclosure Control Freaks
Building enclosure control freaks know that a good exterior sheathing can make a huge difference in performance. Controlling the flows of moisture, air, and heat requires good control layers. A lot of materials and methods will get you there, but…
Building Science Term of the Week: Grains of Water
Every area of building science has its jargon. And I'm not just talking about the acronyms, initials, and abbreviations that get thrown around casually. I've been making a list of the most interesting, useful, or stupefying BS terms and giving…