Blower Door testing

[tmurray]

The IRC allows recirculator hoods, and hoods are not even a requirement in a SFR.

So, there are solutions, just the IRC doesn't make them mandatory.

 

[jar546]

So, there are solutions, just the IRC doesn't make them mandatory.

Correct.

 

[Wooly]

The hardest home to pass a Blower Door Test is a slab on grade.

Keep in mind that the BDT is measuring the square inches of open gaps to the outside of a home. If I'm running the BDT and you open a window, I can look at my CFM numbers on my manometer and tell you how far open you made that window.

The BDT is based on the volume (cubic Ft) of the entire thermal envelope of the home and the amount of CFM leaving it at -50PA.

Slab on grade has 1/2 the volume of a home with a standard basement, therefore has 1/2 the amount of allowable airflow for the BDT to pass.

Slab on grad also tends to punch the HVAC plenum through the ceiling and turn the ceiling into Swiss cheese with supply registers.

I tell builders when building slab on grade to put a bead of liquid flashing on both sides of the sill-seal foam gasket before the sill-plate is installed. This creates a much better bond and can be the difference between passing and failing. Without doing this method first, caulking around the entire interior perimeter of the home is the only way they've been able pass. This can be very ugly if the floors and baseboard have already been installed.

I often see zero air-sealing where the plenum exits into the attic through the ceiling, and I rarely see the supply resisters properly air-sealed to the floor of the attic. Unsealed flues and AC line-sets are also contributing to failures, in addition to bath-fans, walk-up attic stairs without thermal covers installed, poorly constructed attic hatches, plumbing/HVAC chases from the attic that lead all the way to the basement, and electrical penetrations left unsealed or sealed from the interior of the home not the attic-side.

Can-lights are also neglected often times as far as air-sealing is concerned.

The bond-joist in the basement is definitely one of the biggest sources for air-infiltration in a standard stick build home.

Insulation companies that flash batt the joist-ends and try to use can foam along the sill-plate have a hard time passing at 4<ach@-50Pa.

Some of this has to do with the quality of the framing too. If the drywall isn't sitting flush to the framing, all sorts of gaps happen along the wall-tops in the attic allowing attic air to infiltrate into the open wall cavities while running the BDT.

Slab on grade is inherently difficult since your volume to exposed surface area is so skewed. That why the code is slowly changing to equivalent leakage area. That's the only correct blower door number not ACH50.

 

[Wooly]

The two most expensive things people have in life come with no owners or instruction manuals, kids and houses. But yet I got a pictogram instruction with the bottle opener I just bought!?!?!

 

[Energystar]

You guys need to get with the 21st century. The IRC has required blower door testing since 2012. Zones 3-8 were then required to be 3 ACH50 or less. It also required whole-house ventilation.

Spending extra money to seal a home so that one must then spend still more money to ventilate it may at first seem parodoxical. However, a home is not smart enough to breathe on its own. Leakage is mainly driven by temperature difference and/or wind. In order for ventilation to occur, there must be an opening and a pressure difference across it. In a leaky home without forced ventilation when the weather is moderate as in the spring or fall, the home will suffocate. During extreme weather, ventilation will be maximized leading to loss of comfort and high energy bills. Some people like to open their windows during the shoulder months but unfortunately this is when allergens are at their peak (pollen, mold, etc.).

The amount of ventilation required by code to keep a home healthy is trivial—typical around 60 cfm continuous. It is much heathier to seal the home and force this modest amount of air that is dependable 24/7.

Our homes range from about 0.7 to 2 ACH. In average to large sized homes we install ERVs. In small ones we use an inline fan in the attic with a speed control. In either case, we pull the air out of the bathrooms thereby negating the need for bath fans. Each bath needs 20 cfm continuous which is normally very close to the code required ventilation amount. No more worrying about those teenagers forgetting to run the bath fan during hot, 30 minute showers.

In my experience, the source of leakage that is most commonly overlooked is through interior walls and openings in the ceiling, i.e., fixtures and smoke alarms. Interior walls are full of switches an outlets. Air also leaks through the base of the walls. From here it simply passes between the top plates and drywall through the insulation and into the attic. Builders around here foam or caulk these areas and have little trouble passing the 3.0 BDT.