How to become an air control freak!
This post will attempt to get everyone on board with the idea of being an air control freak, and becoming one will give you one of the biggest bangs for your buck in energy savings. We obviously do not want to stop all air from coming into the home. In fact, ventilation is crucial to healthy indoor air quality.
We just want control.
On the interior of the home there are lots of ways that homeowners and home inspectors can actually see evidence of heat loss—or more accurately—air movement. While the title of the post is an attempt to convey that the science of this topic is a little more complicated than I want to get into in this post, I will simply lump all of these mechanisms into “ghosting” for simplification. For a more technical review of all of these mechanisms see: Thermal Tracking: How to Diagnose Indoor Wall or Ceiling Ghosting Stains.
Ghosting at the edges of carpet where air is coming and going in and out of the building is one such example.
Part of the reason this is complicated is because “ghosting” does not always mean heat loss or gain—it typically indicates areas of more or less air movement in relation to warmer or cooler surfaces—or just plain air movement. Ghosting where air is moving around poorly weather-stripped doors is another example.
Ghosting can give away missing insulation above a ceiling,
or even no insulation at all.
Ghosting can show where air is moving in and out of the home at an attic or crawl space access hatch—the carpet is merely filtering the air.
On the exterior of the home one can also find similar ghosting where air is moving in and out of the building.
Air always has dust particles in it and over time it will build up in these areas creating these various shadows of air movement. You can’t see the air but you can see where it moves.
Sometimes it is not dust particles that give us an indication of air movement and heat loss, as can be seen in the frost patterns on this building.
At a recent inspection I had another example of a “visual representation” of heat loss. This time it was not so much by signs of air movement, but a combination of conduction and air movement. It was a cold day and moisture had condensed all over the siding of the buildings. There were four buildings each with four apartments. The north sides of all four buildings—the north sides of all of the apartments—looked like the following picture.
The dry area under each window is where an in-wall, forced-air, electric heater is located. Every window looked like this—whether the heater was on or not. Most were not on at the time of inspection; in fact one was not even functional.
This is an example of where the energy code, as a “minimum” standard, falls a bit short of “best practice.” If the entire cavity was filled with duct it would be required to be insulated to the level of the rest of the wall, but an item like a pipe, electrical outlets or these small heaters are considered minor breaches of requirements and the walls are not required to be insulated behind the heaters—or at least not to the level of the rest of the wall.
One of the questions I frequently am asked is, why can’t these spaces be the means of bringing fresh air into the home? The simple reason—and there are more complicated reasons—is that these bypasses work 24/7—far more than is necessary if we maintain control.
What signs of air leakage can you find around your home?
By Charles Buell, Real Estate Inspections in Seattle
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