Blower Door testing

[Blower Door Expert]

For those of you who are on the fence about Blower Door testing, please keep in mind that a home can be too tight.

I've been performing Blower Door tests since 2012, and I own one of the largest Blower Door companies in Michigan. I also hold a 2 hr seminar worth 4 credits for recertifying Code Officials and Building Inspectors on Blower Doors and Duct Leakage testing.

Not only do 20-25% of the builders my state have a problem passing the BDT at our current requirement of 4 or less air changes per hour@-50Pa (2015 IECC), but more and more I'm running into people being their own GC and building their home far too tight without having any mechanical ventilation installed.

i.e. HRV or ERV. These types of mechanical ventilation will provide the necessary amounts of air changes per Hr needed to prevent moisture buildup. I see them for sale at big box stores for around $1,000.00 (probably $2,500 installed professionally).

Because these types of homebuilders spared no expense and hired the best framers, best drywallers, and best spray foam technician's they could find, their home are testing out far below 2 air changes per Hr, and often time less than that, and this is when there is a major problem.

As we live, breath, bathe, clean, and cook in our homes; we create moisture. If you don't have enough air changes per hour or mechanical ventilation, moisture build up in between the drywall and air-barrier. I'm guessing you can decide what happens next.

Without a BDT there is no way to determine how tight the thermal envelop is, and if there's no mechanical ventilation to help alleviate the moisture levels, a "sick house syndrome" will happen, unfortunately this syndrome is only found out AFTER the occupants in the home have been hurt by the moisture issues.

Forget about the Energy aspect of this test because this is more of a health and safety issue than anything else.

I see Officials posting on here about not being able to find a BDT contractor.

bpi.org will provide a certified technician in every State.

 

[jar546]

I am one of those who believe a home can be too tight and cause air quality issues inside the home. Thanks for posting this and I look forward to more information from an industry expert.

 

[Blower Door Expert]

I am one of those who believe a home can be too tight and cause air quality issues inside the home. Thanks for posting this and I look forward to more information from an industry expert.

Any questions I can help you out with, please ask away..

 

[jar546]

What are the most common blower door test failures and why?

 

[Gregg Harris]

Air leakage from wall penetrations and ceilings, light outlets and switches wiring from floor to floor etc. Natural draft appliances, attic fans, windows, exterior walls.

 

[Yankee Chronicler]

Forget about the Energy aspect of this test because this is more of a health and safety issue than anything else.

But we can't forget about the energy aspect, because it's in the code. The code requires tight houses. If that means adding mechanical ventilation, then it means adding mechanical ventilation.

Are you advising us to ignore the energy provisions in the IRC?

 

[tmurray]

I would disagree that a building can be too tight. It can be so tight it requires mechanical ventilation, but that is not "too tight" in my mind.

FYI mechanical ventilation is required in all buildings in Canada where they are occupied in the winter. We have houses being build below 1 ACH fairly consistently by builders and are not detecting air quality issues when the proper mechanical systems are installed.

I worry when we say that buildings "can be too tight" the public misconstrues this to mean that there is no solution for this. There are solutions for tight buildings.

 

[tmurray]

Air leakage from wall penetrations and ceilings, light outlets and switches wiring from floor to floor etc. Natural draft appliances, attic fans, windows, exterior walls.

Electrical boxes and bathroom fans were the ones that I used to find all the time.

We are a heating climate, so vapour barrier goes on the inside. This is what is typically treated as the plane of air tightness in most buildings as well. We would do a great job of running vapour barrier around electrical boxes and bathroom fans, but forget to seal where the wiring and ductwork penetrated the vapour barrier.

 

[jar546]

A house that’s too tight can absolutely cause issues when HVAC systems aren’t running year-round. In areas without AC, or during mild weather, there’s no forced air movement, and stagnant air can lead to condensation inside walls. Not everyone wants to open windows, so passive ventilation, like trickle vents, passive stack systems, or dedicated fresh air intakes, needs to be part of the solution. Just saying “mechanical ventilation solves it” ignores real-world scenarios where HVAC isn’t always running.

 

[steveray]

Electrical boxes and bathroom fans were the ones that I used to find all the time.

We are a heating climate, so vapour barrier goes on the inside. This is what is typically treated as the plane of air tightness in most buildings as well. We would do a great job of running vapour barrier around electrical boxes and bathroom fans, but forget to seal where the wiring and ductwork penetrated the vapour barrier.

Good thing the 2021 IECC requires NEM OS4 marked and gasketed boxes....

 

[tmurray]

A house that’s too tight can absolutely cause issues when HVAC systems aren’t running year-round. In areas without AC, or during mild weather, there’s no forced air movement, and stagnant air can lead to condensation inside walls. Not everyone wants to open windows, so passive ventilation, like trickle vents, passive stack systems, or dedicated fresh air intakes, needs to be part of the solution. Just saying “mechanical ventilation solves it” ignores real-world scenarios where HVAC isn’t always running.

I'm not sure I understand your "HVAC isn't always running statement". In Canada, mechanical ventilation operates based on the relative humidity in the building, regardless of the space conditioning operating or not. Is ventilation for buildings in the US not provided on an on demand basis? How would that work? Scheduling? Only when space conditioning systems are running?

When we've found issues with indoor contaminates in very tight buildings, the problem tends to be poorly sized and/or installed ventilation units.

 

[mtlogcabin]

Just saying “mechanical ventilation solves it” ignores real-world scenarios where HVAC isn’t always running.

Or the home owner/landlord will not repair the HRV or ERV units when they fail to operate.

 

[jar546]

I'm not sure I understand your "HVAC isn't always running statement". In Canada, mechanical ventilation operates based on the relative humidity in the building, regardless of the space conditioning operating or not. Is ventilation for buildings in the US not provided on an on demand basis? How would that work? Scheduling? Only when space conditioning systems are running?

When we've found issues with indoor contaminates in very tight buildings, the problem tends to be poorly sized and/or installed ventilation units.

Cooking and cleaning create a lot of contaminants in the building, and not all cooking creates moisture, sometimes just smoke. Relying on relative humidity alone is not all encompassing of all situations.

 

[tmurray]

Cooking and cleaning create a lot of contaminants in the building, and not all cooking creates moisture, sometimes just smoke. Relying on relative humidity alone is not all encompassing of all situations.

You mean like this?

9.32.3.7. Supplemental Exhaust
(See Note A-9.32.3.7.)
1) Except as provided in Sentences (2) and (3), a supplemental exhaust fan with a
rated capacity not less than 50 L/s shall be installed in each kitchen.
2) A supplemental exhaust fan is not required in a kitchen where the only exhaust
air intake for the principal ventilation fan is located in that kitchen.
3) A supplemental exhaust fan is not required in a kitchen where the principal
ventilation fan draws from that kitchen and other rooms, provided
a) the principal ventilation fan can be switched to a high exhaust rate equal
to not less than 2.5 times the minimum normal operating exhaust capacity
specified in Table 9.32.3.3., and
b) the high exhaust rate of the principal ventilation fan, as described in
Clause (a), is activated by a manual switch in the kitchen labeled “KITCHEN
EXHAUST.”

 

[Joe.B]

In my opinion it is better to design systems that don't rely on mechanical and/or maintenance to make it last. This is the reason CA and many other states won't switch to the IPC. The UPC requires a system that works without reliance on parts that can fail.

I am definitely one to say, "houses can be too tight" and I don't believe that it has to be one or the other. Spending a bunch of extra money and using toxic materials (foam) to increase the energy efficiency, and then having to add ventilation seems bass ackwards to me. There are great systems that are engineered to be energy efficient and keep homes heathy.

 

[jar546]

You mean like this?

9.32.3.7. Supplemental Exhaust
(See Note A-9.32.3.7.)
1) Except as provided in Sentences (2) and (3), a supplemental exhaust fan with a
rated capacity not less than 50 L/s shall be installed in each kitchen.
2) A supplemental exhaust fan is not required in a kitchen where the only exhaust
air intake for the principal ventilation fan is located in that kitchen.
3) A supplemental exhaust fan is not required in a kitchen where the principal
ventilation fan draws from that kitchen and other rooms, provided
a) the principal ventilation fan can be switched to a high exhaust rate equal
to not less than 2.5 times the minimum normal operating exhaust capacity
specified in Table 9.32.3.3., and
b) the high exhaust rate of the principal ventilation fan, as described in
Clause (a), is activated by a manual switch in the kitchen labeled “KITCHEN
EXHAUST.”

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

 

[steveray]

I believe the Mech ventilation has been required since the 2015 IRC......Somewhere around 5ACH of building leakage.......

 

[SCBO1]

Cooking and cleaning create a lot of contaminants in the building, and not all cooking creates moisture, sometimes just smoke. Relying on relative humidity alone is not all encompassing of all situations.

Hay grandpa what's for supper! "Love smellin me some bacon bein cooked in the morning!

 

[SCBO1]

In these parts, blower door test anywhere from $250.00 - $450.00, then add the Radon test and a radon fan set-up @ $750+

No sprinkler requirement here but the contractor has to ask his customer if they want it, not sure how that works when building a spec house? Haven't seen any signed waivers submitted.

Contractors still bitchin about bathroom fan venting through the sidewall or roof, "Why can't we vent it into the attic!".
I've actually seen what venting a dryer vent into an attic can do, first sign was the dryer laying out in the driveway, second sign is the drywall looks like its about to fall on your head and it had little black spots. Home owner wanted to know "what caused that to the ceiling?" Can you show me your dryer, yeh, I just got a new one, my old one shoot craps!

 

[mtlogcabin]

"Why can't we vent it into the attic!".

For the same reason you can't vent it out through a vented soffit.

 

[jar546]

I know that photo well.

 

[Blower Door Expert]

But we can't forget about the energy aspect, because it's in the code. The code requires tight houses. If that means adding mechanical ventilation, then it means adding mechanical ventilation.

Are you advising us to ignore the energy provisions in the IRC?

Absolutely not, and far otherwise.
Having been an independent third-party performing BDT's on new construction for the past 10 years in MI.

I often run across plenty of pushback from builders and officials who seem to think that the BDT is as menial as gutter inspections.

I only wanted to bring light to the importance of testing, not just for the Energy Code, but for the "sick Home syndrome" that may put people in jeopardy.

There are also many jurisdictions here that don't enforce the BDT code at all. Or allow insulation companies to perform (or pretend to preform) the test themselves.

I realize the caveat "where required by the code official, the BDT shall be conducted by a certified independent third-party", but for me that's like saying a plumber can flush a toilet and call their work "good".

 

[Blower Door Expert]

What are the most common blower door test failures and why?

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.

 

[Blower Door Expert]

For the same reason you can't vent it out through a vented soffit.
View attachment 15247

At least they didn't use cardboard baffles.