Reposted from i.e., the Center for Energy and Environment's Innovation Exchange blog --


Even though the walls of an apartment look solid, air buoyancy and pressure differences between interior spaces cause air to move between rooms and even to other units in the building. And as it travels within a building, air pollutants such as secondhand smoke (SHS) can find their way from one unit to another. Stack, wind, and exhaust fan effects are all interior air driving forces that affect the migration of SHS within a multifamily apartment building.

In winter, for instance, the heated air inside the building has a lower density than the colder outside air. Think about a hot air balloon: warm air rises. Because of its buoyancy, the warm indoor air tends to rise and escape out of the top of the building. This air movement draws cold outside air in through the lower part of the building. Watch the Winter Stack Effect animation below to see how as the interior air rises, SHS migrates with it from lower to upper apartment units.

In summer, the opposite airflow occurs. The conditioned indoor air is cooler and denser, and therefore tends to flow towards the lower half of the building. Warm outside air is drawn into the upper half of the building. As you can see in the Summer Stack Effect visualization below, the interior air movement entrains SHS from higher to lower units.

Whatever the temperature, when air flows from a high pressure area to a lower pressure area, it creates wind. And when wind impinges on a building, the interior air tends to flow from the windward side to the leeward side, i.e. from high pressure to low pressure. Our Wind Effect animation shows how air carries SHS as wind pushes it from one unit to an adjoining unit.

In addition to the weather, mechanical factors can affect indoor air movement. In the next animation, you can watch as an exhaust fan sucks air out of a room, mechanically lowering its pressure. This create a pressure difference between the room and its surrounding areas. Since air flows from high pressure to low pressure spaces, air from the adjoining rooms is drawn into the room where the exhaust fan is running. Our final visualization shows how the Exhaust Fan Effect can entrain SHS from an adjoining unit below.

We hope that our animations will improve your understanding of the air driving forces in buildings and how they affect secondhand smoke transfer between apartments. Feel free to link to or embed these videos from this blog post, our resource page, or our YouTube site.

The motion graphics animations were designed and produced by Huma Saqib.

Related posts:
> 1,000 Words: Combi System Animations

Indoor Air Quality and Energy Efficiency: Part 1

Views: 277


You need to be a member of Home Energy Pros to add comments!

Join Home Energy Pros

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Robyn Smith replied to Chris Woods's discussion Looking to purchase Minneapolis Blower door system- Model 3 with DG-700 in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Chris, I replied to you via email yesterday. I have what you are looking for!! Minneapolis…"
19 hours ago
Profile IconJohn Gillis, William C Gilbert, Brian Breckin and 4 more joined Home Energy Pros
22 hours ago
Paul Scheckel posted a blog post

Energy Ambassadors: Cuba and Vermont

Last winter i had the pleasure of hosting a Cuban colleague for a week in Vermont. We toured the…See More
Linda Wigington commented on David Eggleton's group 1000 Home Challenge
"Two more projects have recently been approved as 1000 Home CHallenge candidates. We welcome Eric…"
Colin Genge posted events
Craig McManus replied to Timothy Renz's discussion Vinyl batt to metal frame ware house
"How can I air seal a metal building in the south to keep out humid air which is causing mold? Will…"
Tom White posted a video
Profile IconJeshurun and Chris Woods joined allen p tanner's group

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service