Houses are notoriously leaky.  In fact, Energy Star reports that in general, homeowners could save 20% on their heating and cooling bills with proper air sealing. 

DC row homes with their turn of the century construction details and changes due to age are even more difficult to effectively air seal than more modern homes.

Conceptual air sealing back to the box…

Let’s take a review our insulation strategy for a moment… 

Think of the house as a box…the box has a top, four sides and a bottom.  The best insulation strategy is to not only insulate all six sides of that box but connect all the seams of the insulation to make the it continuous. That is the ideal that we try to achieve.

When it comes to air sealing, we want to create a continuous air seal on all six sides of the box.  This is usually done at the insulation layer.  It is also very common to have multiple air seal layers.

However, through experience, we know that DC row homes with their turn of the century construction details and changes due to age are more difficult to create this conceptual “air sealed box” effectively because it becomes more difficult to connect and seal all the transitions of materials that make up the box.   

For example, some of the air sealing challenges we deal with are:

•  Cracks in brick walls with wind whistling right in, or connecting with the neighbors

•  Random holes and openings, to the outside, and to neighbors

•  Openings that are no longer plumb nor square, making windows and doors difficult to install properly

•  Band joists that have gaps behind them for hot and cold air

•  Extensive water damage to roofing, rotting joists, evaporated studs, etc

•  Termite damage that needs to be dealt with

•  Existing concrete that is a mess, cracked and unlevel leaving gaps for air and water

•  Non-level floors that make it difficult to seal

•  Tight spaces that require “creative” installation of equipment

•  Existing plaster that has gaps to brick

•  Brick walls that porous and therefore inherently leaky of air

•   …the list is endless, really

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Airsealing the top of the box…the second floor ceiling

We use an airtight drywall approach to seal the top floor ceiling.  This includes:

•  Pre-blocking at the ceiling joist level to give the drywall something to attach to at the edges

•  Sprayfoaming any large gaps that exist at corners and trimming prior to drywall install

•  Gluing the drywall to all the ceiling joists

•  Screwing the drywall (no nails)

•  Caulking any penetrations for lights, electrical boxes, etc

Airsealing the sides of the box…the walls

We have a few different materials that we deal with on the party walls.

Brick

Exposed brick in the basement…brick walls are leaky, cracks or no cracks.  To effectively air seal them, we either laminate them with drywall (as we did at the stairs) or use track and stud.  The trick is, the drywall needs to go in before the stairs or walls in order get a continuous airseal along the entire wall.

Brick in the joist bays…we fit the bays with insulation and spray foam the backs and sides to air seal not only the pockets where the joists sit, but also the bricks themselves. 

Brick gaps left by removed walls are sealed with rigid insulation and spray foam. Brick gaps due to water damage are sealed with rigid insulation and spray foam

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Plaster

Plaster walls…are laminated with drywall. 

The top edge where they meet the joists are sprayfoamed, then caulked and then mud and taped.

The laminated sheet rockseams are caulked.

The bottom edge where they meet the existing floor are sprayfoamed, then caulked and finished.​

Wood

All stud seams are either sprayfoamed or caulked or a combination of both.

All points where wood meets the sheathing are caulked.

The sill plate and top plates are caulked to the floor and other framing.

Openings for new windows and doors get the royal treatment

First, the snow and ice bitumen is installed to the sill and exterior sheathing. Second, they are set in a bed of caulk and fastened in place. Third, if necessary, backer rod is installed in gaps. Fourth they are caulked around the window.​

Windows

Openings that had widows before get a different royal treatment…

The original windows had the sash weight assembly still installed in the wall.  That assembly is removed, and a new wood “box” installed to give the windows a new point of attachment.  However, this “box” is smaller than the original windows and there is a large >2-3” gap that you can see through to the outside that needs to be filled. We place rigid insulation and then spray foam to seal those large holes.​

Mechanical penetrations

Are spray foamed/fire stopped.

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Outside air sealing

Exterior rigid board is tape sealed.

Band joists…at the front wall of the home the first floor joist is usually close (within an inch or so) of the front brick wall.  That inch or so gap is a thermal bridge, and a place where hot or cold air sits.  We drill holes in that joist and fill that gap with spray foam.  You can see in this picture where there are two drill holes that have sprayfoam coming out of them.

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