Whole Home Remodel/Expansion Part 3: Building an Airtight Addition – Blower Door Testing

What was once simply empty space above the garage (read more here) has now been completely framed out. Entering the space, the homeowners can now see where their new office, bathroom and guest bedroom will be. It’s starting to come together!

In our last blog, we discussed framing and insulation. The next step is to make sure the new addition is properly sealed from the elements using a high-tech vapor barrier. We want to keep moisture OUT and any heated or cooled air produced by our heat pump/mini splits IN.

We used Majrex by SIGA as our barrier. What’s interesting about this product is that it has tiny pores in the membrane that actually change shape. As the weather gets warmer in the summer, the pores open up to allow moisture to escape—which keeps mold from growing in the walls. In the winter, the pores close up to keep moisture from getting in. When we’re building new construction it’s a lot easier to seal spaces, but in remodels like this one, we’re adapting to existing conditions. In the end, Majrex will ensure that the new rooms above the garage will be sealed up tight.

Here’s the SIGA Majrex vapor barrier installed on the walls and the ceiling. The seams are taped and you can see where the heat pump will soon be installed in the ceiling. The heat pump (also known as a mini split) will provide BOTH heat in the winter and air conditioning in the summer.

Once the vapor barrier is installed and all the seams and edges of the windows are taped, we conducted a blower door test to see how well we had done sealing. We installed a temporary door at the entrance of the new addition. At the bottom of the door, a large fan pulls air out of the space, lowering the pressure inside the room. Measuring the pressure differences allows us to determine how “tight” the room is.

Here we are setting up for the blower door test.

Next, we reverse the fan and blow air INTO the room. We then use a smoke gun tool, which emits a thin wisp of smoke, and run the tool along any windows and seams around the room. The smoke is drawn towards any holes or gaps and shows us just where we need more tape or sealant.

Click the image to watch our YouTube video of the blower door test and how we seal up any holes we find.

Once the test is complete and any gaps are filled, we can move forward with construction of the walls. When the project is completed, the homeowners can be confident that they aren’t losing heated or cooled air from their new living space!

Using the smoke gun around the edges of the windows to make sure no air is escaping.