condensation

musingsheader image

Condensation on Car Windshields

There are four types of window condensation, and each calls for a different fix

Posted on Feb 2 2018 by Martin Holladay
prime

A surprising number of people don’t understand the causes of condensation. If you ask a stranger on the sidewalk, “Does condensation happen when cold air encounters a warm surface, or when warm air encounters a cold surface?,” many people will shrug their shoulders.

Here’s an example of this type of confusion: When drivers see condensation on their windshield during the summer, they are often unsure of the best remedy. Should they turn on the heater or the air conditioner?

Let’s look at four different scenarios.


Tags: , , , , , , , , ,

Image Credits:

  1. Jessica Merz - Flickr

building-scienceheader image

Adjusting Bath Fan Use in Winter

Do you really need to run it when you shower?

Posted on Jan 24 2018 by Allison A. Bailes III, PhD
prime

You may have heard or read somewhere that you should run your bathroom exhaust fan whenever you take a shower and then let it run for a while after you're done with the shower. Showers increase the humidity in the bathroom. Sometimes it gets high enough to cause condensation to appear on the mirror and other surfaces in the bathroom. And that can result in mold growth.

So you should always run your bath fan when you shower. Or so they say.


Tags: , , , , ,

Image Credits:

  1. Energy Vanguard

building-scienceheader image

Four Sources of Crawl Space Moisture

To stop moisture problems in vented crawl spaces, you have to know where the moisture comes from

Posted on Oct 11 2017 by Allison A. Bailes III, PhD
prime

Here in the southeastern U.S., we have a lot of crawl spaces. Most are vented. Even most new ones are vented. It's not because it's the best way to keep them dry. That's certainly not true. We have enough research on crawl spaces to know better. No, they're vented because foundation vents got into the code decades ago and, once there, they’ve been difficult to dislodge.

So if you have a vented crawl space, especially in a humid climate, it most likely has moisture problems. And where does that moisture come from? Let's take a look.


Tags: , , , ,

Image Credits:

  1. Energy Vanguard

building-scienceheader image

Is It Possible to Get Condensation on a Sponge?

A little building science puzzler on moisture and the properties of materials

Posted on Sep 13 2017 by Allison A. Bailes III, PhD
prime

I recently taught a class called What the Duct!? at the Builders' Boot Camp in Virginia. Paul Francisco was one of the other instructors (teaching about indoor air quality), and on the last evening at dinner, our conversation turned to building science. (Imagine that!)


Tags: , , , , , , ,

Image Credits:

  1. Image #1: Gosheshe - Flickr.com
  2. Image #2: Energy Vanguard
  3. Image #3: Professor Chris Timusk

building-scienceheader image

An Interesting Moisture Problem in a Trendy Restaurant

Observations by astute diners give clues as to the source

Posted on Sep 6 2017 by Allison A. Bailes III, PhD
prime

I've got the curse, you know. I can't walk into a building and not check out what's going on with ductwork, windows, and anything else that lets me apply what I know about building science.

Recently, I went to lunch at a trendy restaurant near Emory University and of course looked up at the ceiling. You can see what caught my attention in photo at right. The restaurant is only three or four years old, so I've been watching this problem get worse for a while now.

I have a few ideas about what's happening here. Do you?


Tags: , , , ,

Image Credits:

  1. All photos: Energy Vanguard

building-scienceheader image

Buried Ducts Allowed in 2018 Energy Code

The keys are duct leakage, R-values, and the vapor barrier

Posted on Feb 15 2017 by Allison A. Bailes III, PhD
prime

Water vapor from the air condenses on air conditioning ducts in humid climates. It's as normal as poorly insulated bonus rooms making occupants uncomfortable or cigarettes causing lung cancer. Condensation on ducts is most common in crawl spaces and basements, where the air is more likely to have a higher dew point.


Tags: , , , ,

Image Credits:

  1. Energy Vanguard
  2. D. Mallay, Home Energy Research Labs, Building America research report

QA-spotlightheader image

Indoor Condensation Plagues This Chicago Home

Is there a way to prevent the formation of frost or droplets of water on some of the ceilings in this home?

Posted on Jan 2 2017 by Scott Gibson

Pat Andersen and her husband have been diligent about energy upgrades and maintenance on their 33-year-old Chicago home. They've sealed air leaks in the attic floor, replaced leaky windows, and checked the airtightness of the house with a blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas..

But one problem remains: condensation in the form or water droplets or frost on some ceilings on the second floor. Andersen would love to find a solution.


Tags: , ,

musingsheader image

Worries About Trapping Moisture

While some types of wall assemblies and roof assemblies are risky, many worries about ‘trapping moisture’ are baseless

Posted on Dec 2 2016 by Martin Holladay
prime

A significant number of questions posted by readers on the GBAGreenBuildingAdvisor.com site are variations of, “Will this wall detail (or roof detail) trap moisture?”

When I entered “trap moisture” into the GBA search box, I got 182 results. The search terms “trapping moisture” yielded another 104 results. Clearly, there is a high level of concern around the issue.


Tags: , , , ,

Image Credits:

  1. Kontrol

musingsheader image

Preventing Water Entry Into a Home

To lower your home’s indoor relative humidity, you need to address all sources of water entry

Posted on Jan 15 2016 by Martin Holladay
prime

If it is designed well, the thermal envelope of your home should control the flow of heat, air, and moisture. Unfortunately, the floors, walls, and ceilings of older buildings are often leaky: they leak heat, they leak air, and they leak moisture.

If you are building a new house, you have the opportunity to control the flow of heat, air, and moisture through your home’s building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials.. The result will be a durable, comfortable building that doesn’t cost much to heat and cool.


Tags: , , , , , ,

Image Credits:

  1. Martin Holladay

building-scienceheader image

Preventing Accidental Dehumidification

A lesson for winter on dew points and condensing surfaces

Posted on Dec 2 2015 by Allison A. Bailes III, PhD
prime

"Oops! The house just had an accident. Whose turn is it to clean it up?"

Yep. We're entering the season of accidental dehumidification. If you've got windows that start collecting water, like the one shown here, you're a victim of accidental dehumidification. It's not something you want in a building.


Tags: , , ,

Image Credits:

  1. Energy Vanguard

Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!

Syndicate content