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.

 

[Enrgxprt]

A little late to this discussion, In the last building position I had, I was the project manager for a developer/builder, literally built 700+ houses over a 20 year span.
I was lucky, in 06 the owners asked if I wanted to goto an "insulation" class.. turns out it was BPI's building analyst.. then, shell, then heating, then what's this HERs, then Thermography, then passive.. all while I was still building houses.. we applied the knowledge gained from all of these certifications immediately. I had a great 5 years of building to see the differences. My takeaway is, you cant build it too tight If its actually ventilated right. Imagine a seesaw. When one end goes up the other side (being on a pivot) goes down. The side going down (infiltration) HAS to have the other go up. Now imagine this pivot to one side more than the other (lever) a great reduction in infiltration needs only a little more ventilation. In the thousands of homes I have tested, 80% did not meet code for adequate ventilation. Most times a simple fix, but what I saw was builders understand the tightness issue, but the trades failed on the execution of ventilation.

All of this and the 1 huge drawback for a tight homes with unconditioned basements was damp basements. Infiltration allowed the basements to dry out (up through the house) tight homes wouldn't let the basements moisture move up and out, mold on basement stair and drywall above boilers and staircase (within months) was common to ANYONE who did not install a basement dehumidifier.
Moving the thermal barrier from the basement ceiling to the basement walls and actively conditioning that space solved the problem. Next issue was atmospheric drafted heating equipment in the basement needed fresh air, build a boiler room. Next issue was that equipment with fresh air to the outside was in an unconditioned space (like it was before) so get fresh air kits for the burner intake shroud.

The point of all of this is all of the issues that come with more advanced technology have solutions (again more advanced solutions)

Someone said earlier that lack of air movement causes condensation. If they are talking about infiltration, I disagree. If they are talking about the simple act of air movement itself, I disagree.

Condensation needs humid air to move over a cold surface. Period. Full stop. If your seeing condensation you have 2 problems. Cold surfaces with air having too much moisture in it (RH) and a dew point being met. Full stop. You have to ask your self, why is the airs RH so high, or why is the surface so cold. Has absolutely nothing to do with lack of air movement unless the mechanical systems are failing, or there is a source of moisture that shouldn't be there, or the insulation is missing.

Back to the question of biggest areas for infiltration. In my life I have seen that any where a walls top plate meets an unconditioned space, that that wall needs a drywall gasket on the lower of the top 2 plates.

Its simple, does the top of that wall (exterior or partition) have fiberglass insulation above it? If yes, the drywall needs to be gasketed ( not caulked) to that top plate. Period. Full stop.

As the studs dry, a space is created between the drywall and plate. Every cavity, every bay now becomes a chimney to the unconditioned space above. While the space between the drywall and plate may only measure 1/16" I have see in existing homes 1/8-3/16"! Now multiply that by however many linear feet of top plate ( again, partition walls (x2) and exterior walls). The effective leakage area on that alone can easily be 5sq ft. Its like having a Windows open to the attic all winter long.

Most builders i now see are shocked when they try the gasket out for the 1st time. I have built and seen many traditional fiberglass insulated homes have blower door numbers lower than many spray foamed homes. Not always, but sometimes. Point is, that is in my opinion the biggest and best low hanging fruit...

 

[Inspector Gadget]

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.

I can concur.
Also, we've been finding a lot of contractors not cluing into the requirement to
1) have vapour barrier run behind demising walls
2) have vapour barrier continuous through concrete slabs (although this is admittedly minor)
3) seal electrical wire penetrations through studs going into exterior walls/ceilings
4) have vapour barrier (air barrier) sealed to windows.