Do Airtight Houses Need Makeup Air?
When you turn on an exhaust fan, it blows air from inside the house to the outdoors. That air leaving the house will be matched by an equal amount of air coming in from outside. The more airtight the house…
air leakage
How to Avoid the Flaw in Structural Insulated Panel Construction
Before 2001, the biggest construction project I had ever taken on was a bookcase. My most complicated project was probably the mahogany lamp table I built in tenth grade shop class. (I still have it!) Then I decided to build…
Will a Heat Pump Work in an Old House?
The question of heat pumps in old houses is coming up a lot lately. With the great electrification upon us, heat pumps are quickly becoming the number one choice for space heating. In fact, data from the Air-Conditioning, Heating, and…
What’s the Deal With Exfiltration?
When you first start learning building science, you may run into this thing called exfiltration. It's not a widely used word, even among those of us who work in the world of building science. We learn about it and then…
Can Duct Sealing Lead to Condensation?
When can doing something good for your house turn into something bad? Hmmm. There are way too many answers to that question, so let me narrow it down. Is it possible to make your ducts more airtight, a good thing,…
The Ol’ Beer Can Pressure Crunch
Air has weight. Air can move things, like giant wind turbine blades. Air can also crush things. I first got to see the power of air in my introductory physics class in college. The professor, Dr. Jeffrey Trahan, showed the…
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…
Bad Advice About Indoor Humidity in Cold Weather
It's that time of year again. The cold weather has begun here in the Northern Hemisphere, and people are talking about raising the humidity of the indoor air. I'm certainly no fan of bone-dry air, having experienced too much of…
Where Should the Air Barrier Be Located?
Where to put the air barrier may seem obvious, but this question has many dimensions…literally. Let's look at the question of air barrier location from three perspectives. First, building assemblies are three-dimensional. The air barrier can go on the inside,…
We Need Higher Ventilation Rates. But How High?
The COVID-19 pandemic has changed a lot of things, including my view on higher ventilation rates. A few years ago, Joe Lstiburek of Building Science Corporation pushed hard for lower ventilation rates. He believed ASHRAE's residential ventilation standard (62.2) resulted…