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On Submarines and Building Science

A House Is Like A Submarine. The Air Barrier Must Be Continuous To Prevent Infiltration.

A house is like a submarine. The air barrier must be continuous to prevent infiltration.Imagine designing and building a submarine. What’s the most important thing you have to do? Keep the sailors alive! How do you do that? By making sure that when the sub dives below the surface, no water leaks in. The submarine needs to have a completely robust water barrier, right?

Imagine designing and building a submarine. What’s the most important thing you have to do? Keep the sailors alive! How do you do that? By making sure that when the sub dives below the surface, no water leaks in. The submarine needs to have a completely robust water barrier, right?

Now, imagine you’re building or remodeling a house. One of the things that building science tells us is that a house should have a really good air barrier. It doesn’t have to be quite as robust as a submarine’s water barrier because the consequences aren’t usually as immediate.

I say ‘usually’ because a car running in the garage can kill people within hours. Even when it’s not so quick, though, relying on random leaks for ‘fresh air’ is a bad ventilation strategy. The air that leaks in from the moldy crawl space, the dirty attic, and the toxic garage is anything but fresh. A house does NOT need to breathe. That’s a myth. The people inside the house need to breathe.

In the design phase, some architects know that there’s a simple trick they can use to check for continuity of the air barrier. They should be able to trace the air barrier around the entire house without lifting their pencil from the paper. Any gaps where they jump from air barrier material to non-air barrier material are design flaws that need to be addressed.

During construction or remodeling, you can walk around the house with your submarine goggles on. Think of the house as a submarine and look for any places where the offending fluid (in this case air) might leak in. If you’re building a new home, you have a chance to do it right from the beginning.

With existing homes, the leaks are plentiful. Look for the big holes first when starting your air sealing duties. If stopping air leaks into your home really were as important as stopping water leaks into a submarine, most likely you’d have been a goner long ago.


Photo of submarine by southtopia from, used under a Creative Commons license.

This Post Has 6 Comments

  1. I often use the same analogy
    I often use the same analogy with clients and in presentations. I tell people that their homes should be as leaky as submarines. It usually gets their attention.

  2. Carl: When
    Carl: When you put it to them that way, I don’t see how it could NOT get their attention.

  3. It is a good analogy. I was
    It is a good analogy. I was on a diesel electric and it did leak; but water wasn’t the problem. It was the air. The insulation was asbestos, the gyro floated on mercury, the batteries gave off hydrogen and diesel fuel didn’t help either. However, these didn’t matter. The crew was well trained, we had backups on all systems, and nobody got on those boats unless they had a sense of humor.  
    Getting back to the analogy. If you are going to tell someone, their house should be tighter than a submarine then you better back that up with materials and air systems equivalent to the testing protocol for airborne toxins in a modern submarine.

  4. hmmm…Does a submarine
    hmmm…Does a submarine really need a Water Barrier…or an Air Barrier? 
    Are you trying to keep the water out?… or keep the air In?…or both? 
    On a Submarine… must “the Barrier” always be “complete”? 
    Can’t there sometimes be an open portal in the bottom of a sub?…as seen on TV? 
    so… even on a submarine…location of the barrier/boundary matters too? 

  5. Allison, 

    That is a good analogy to try to get people to see the need for barriers (air, moisture, pressure) to seperate the interior environment from the exterior environment. 
    Two other examples I talk about are airliners and the space station. 
    There are more windows in an airliner than the normal house and they seal them as well as all the rivets in the exterior skin (cladding). 
    Considering the space station, they must have good barriers in place to seperate the environments or the results would be tragic. The explanation of ventilation of the HVAC systems for submarines, airliners, and the space station. You don’t open the windows in an airliner at 39,000 feet to get fresh air, the periscope of a submarine does not penetrate the ice cap and bring fresh air into the submarine, and there is no air hose running from Houston up to the space station to supply fresh air. Yes the HVAC systems for scubbing, filtering, etc. the air in these examples are much more complicated and expensive,but a solid air barrier with exhaust return ventilation in a building (residential, commercial, or industial) connected to the HVAC system is the best plan for any climate zone. By the way, how many different climate zones can an airliner or submarine operate in without problems? The answer is any climate zone as they have the proper barriers in place. 
    Another nice article Allison. I’m still proud of you and pulling for 6 balls. 

  6. George R.:
    George R.: Yes, indeed the materials and methods you use to attain a tight house are important. I’ve written other articles here in the blog that cover some of that. Also, let me clarify that I’m not saying houses should be built as tight as a submarine because that’s not really possible with the materials we use. My main point was to provide a helpful of way of thinking of a house so that you can see the air barrier – or lack of it. 
    John B.: I was just using the submarine analogy to get you thinking about the air barrier of a house. Yes, there are all kinds of differences between the two, but if a home designer or builder thinks like a submarine designer or builder, the home will have a better air barrier. 
    Gene W.: Thanks! Airplanes and space stations also make good analogies.

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