Airtightness is for Everyone
As a company built on airtightness, we have always pushed the building industry and building codes toward progressively tighter and tighter building goals. Because even at “just” 3.0ACH50, increasing the airtightness of the building envelope will make a huge difference for the comfort and the energy efficiency of projects built to current code. These minimum code requirements are there to not only warrant the safety of the construction, but also to lower energy usage that will help achieve climate protection goals – while making buildings more comfortable and resilient.
Several states require that contractors comply with such air tightness requirements and verify them with a blower door test: Maryland (3.0ACH50), Massachusetts (3.0ACH50), Georgia (7.0ACH50), Illinois (5.0ACH50), Florida (starts in 2017), Washington (Effective Leakage Area-based). [Let us know if we missed your state so we can add it here.]
Now New York State is following in their footsteps and making blower door tests obligatory starting on October 3, 2016. This is a positive step forward. Thankfully, NY is not watering down the requirement to 5 air changes, as some parts of the industry had requested before the IECC 2015 was adopted.
We know that building to 3.0ACH50 is possible for contractors that pay sufficient attention to details, such as using gaskets around pipes and cables, taping sheathing, using good quality weather resistive barriers with taped overlaps, connecting all window openings with the right tape, and using INTELLO Plus as an interior air barrier. Last but not least, the floors and ceilings must be continuously connected to the air barrier. If these steps are taken, houses should easily pass this code requirement.
Details of Testing Procedures
New York State code adds some interesting notes in their supplement to the IECC 2015 (download it here) for the blower door test and how it is conducted, which clarify how the NYS code wants you to interpret ASTM E779/E1827:
- Exterior doors/windows closed, but not further sealed
- Dampers of exhaust, intake, make-up air, backdraft, and flue dampers shall be closed, but not sealed beyond intended infiltration control measures
- Interior doors shall be open, if installed at the time of the test
- Exterior openings for the continuous ventilation system and heat recovery ventilators shall be closed and sealed (which makes sense as it is included in the energy model, and doesn’t result in additional leakage)
- Heating and cooling systems, if installed at the time of the test, shall be turned off
- Supply and return registers, if installed at the time of the test, shall be fully open
- Testing can only be done after all penetrations of the building thermal envelope have been made
The code official can require an approved 3rd party to the the test and a written report in NYS. It is not completely clear what an approved 3rd party is, but a PE or RA would certainly make the cut. The code official might consider BPI/RESNET rater or Certified Passive House Consultant/Designer as an equal too, but that is not explicitly stated.
The report adds a few interesting additional requirements:
- Floor area per ANSI Z65 (pretty much enclosed floor area from exterior of the wall) + areas less then 5′ in height. However it doesn’t provide guidance regarding ceiling heights or calculating volume, albeit that should be pretty self explanatory.
- NYS requests that the blower door test is of the air volume lost at internal pressurization of 0.2 inches w.g. (50Pa). We take this to imply that the test is done with pressurizing the building. This would be rather odd as most blower door tests only depressurize the building and we expect this not be interpreted this way by the Authorities Having Jurisdiction (AHJ).
Additional Options for Multi-Unit Compliance
Addition of R402.4.1.3 – Optional testing procedure for buildings with two or more dwelling units
Beside testing the entire building envelope to 3.0ACH50 (in which case the units need to be fully connected and pressure equalized), this section allows for each unit to be tested as well for ‘enclosure area leakage’ of 0.3CFM50. The enclosure surface area is defined as equal to the sum of the areas of all elements separating the unit from the exterior, as well as the adjacent units or unconditioned space (floor, walls and ceilings).
The testing is only allowed after all penetrations in the building thermal envelope. However this could mean that some of the apartment enclosure penetrations still have to be made – we would suggest to the approved testing agency and the AHJ to make it a requirement to test only after all penetrations have been made in the enclosure surface area. The other requirements are the same as listed above for the whole project blower door test.
Building with more then seven dwelling units
If buildings have seven or more units – then if approved by AHJ you can group sample sets of not more than seven testing units and common rooms in sample sets.
- Each sample set shall contain testing units that are representatives of all dwelling unit types and all other conditioned occupied spaces.
- If all testing units in the first sample set tested are below 0.3 CFM/sf – the remaining sample sets shall be permitted to be tested at a rate of one testing unit per sample set.
- If any testing unit tested in accordance with paragraph 2 does not meet 0.3CFM/sf enclosure area – then two additional testing units in the sample set shall be tested.
- If any testing units tests in paragraph 3 is not below 0.3CFM/sf, then all units in the sample set have to be tested – as well as all units in the subsequent sample set (if any)
- If the samples set tested in paragraph 4 have air leakage rate below 0.3 CFM/SF – subsequent set are again to be tested per paragraph 2, where approved by AHJ.
What does 0.3CFm/sf enclosure area mean – compared to 3.0ACH50?
As we have stated before, enclosure area leakage is not equal to measuring air leakage of the conditioned volume of air. We need to make sure that the conditioned air stays inside, as this is the air we use and the space conditioning we pay for. By splitting up the options into an ACH50 test but then giving a second option to do an (apartment) enclosure test makes things more complicated. This leakage is not really related to heat loss, because temperature in apartments on either side of dividing enclosures are similar. The leakage that occurs through these enclosure areas should be deducted from the entire leakage of the unit/building envelope, if we want to compare apples to apples, and to answer which metric (3.0ACH50) or (0.3CFM/SF50 building enclosure leakage) or 0.3CFM/SF 50 enclosure surface area
As a consequence, the insulation and comfort in the building will be far less than what NYS intended to achieve with this code. We encourage NYS and all AHJ to reconsider this multi-unit blower door methodology, or if they do accept the multi-unit test methods from R402.4.1 – to require 0.15CFM/SF50 or even 0.1CFm/SF50 (for very large buildings) of enclosure surface area leakage to prevent the large discrepancies between the intended 3.0ACH50 and the CFM/SF method, while maintaining the option to test units individually as the code intended. While not forcing blower door testing of the entire envelope at once for large buildings with exterior accessed apartments.
Additional note – Mandatory tenant separation walls
Fire separations between dwelling units in two-family dwellings and multiple single-family dwellings (townhouses) shall be insulated to no less than R-10 and the walls shall be air sealed in accordance with Section R402.4. of this chapter.
This is an nice addition to deal with indoor air quality (second hand smoke, cooking odors etc), by air sealing these walls properly. However we are unsure if the R-10 insulated walls will save much energy and be a good use of insulation material for that purpose. The walls will be mostly adiabatic, since temperatures on either side will be similar. However, heavy fibrous insulation is useful for sound transmission reduction, so it would be good to keep it for that purpose.