PGH at Serenbe is 90% Tighter than Energy Code – Before Drywall!!

proud green home super tight 0.72 ach50 0.055 ELR blower door test earth craft lg squared incBefore drywall was installed, I tested the infiltration (air leakage) at the Proud Green Home (PGH) at Serenbe, and the home achieved 0.72 ach50, or 0.055 ELR (more on these numbers in a minute). In other words, it’s really tight!!! The 2009 International Residential Energy Code (IECC), which is adopted in most states, requires an infiltration rate of 7.0 ach50 or less. That’s seven-point-zero. That makes the Proud Green Home 89.8% tighter than a house built to the 2009 code. The 2012 IECC, which is slowly being adopted across the country (January, 2014 in Georgia), will require homes to be 3.0 ach50. That means the PGH will be 76% tighter than a 2012 code-built house.

Gobledygook! What is ach50 and ELR?

ACH50: Air Changes per Hour at 50 Pascals.

ELR: Envelope Leakage Ratio

Pascals is a measurement of pressure, named after the French physicist (among other things), Blaise Pascal. 50 Pascals is equivalent to the house having a 20 mph wind blowing on all surfaces of the home. This is a standard used in the home performance industry to measure air leakage in a home. Using a blower door, the house is put under 50 Pascals of negative pressure, and a manometer (pressure gauge) spits out a result in CFM50 (Cubic Feet per Minute at 50 Pascals), which tells us approximately how much air is being pulled in through any gaps or cracks.

For ACH 50, we take that cfm50 number and plug it in to a formula, based on volume, and we get numbers like 7 ach50, 3 ach50, or 0.72 ach50!! Some feel this is not the best way to determine leakage, so there are plenty of others, like ELR.

ELR is a ratio of the amount of air leakage (cfm50) and the square footage of the building envelope (SFBE). ELR is taught and promoted by Southface Energy Institute, and is considered by many in the home performance industry, as a more accurate way to measure leakage.

In plain English, the house has a hole that is about 5.5″ x 5.5″, and it’s about 33,000 cubic feet. If this home were built to just meet the 2009 Energy Code, that hole would be 17″ x 17″.

For a good discussion on different ways to measure leakage, and the basics of a blower door, check out this post by Martin Holladay, on Green Building Advisor.

Designing and Building a Perfect Wall Atlanta, Georgia_Cementitious Lap Siding Proud Green HomeHow did we do it? 

We have been posting videos on the construction of the PGH, showing some of the air sealing techniques, including using flashing tape at all joints between framing members, installing BASF open-cell spray foam in all the wall and roof cavities, and using ZIP System R Sheathing on the walls and their Roof Sheathing on the roof. We’ve also talked about the building envelope construction including the foundation and above grade walls. All of these best practices and products resulted in a pretty tight structure.

Designing a home is about architecture and building science. It’s about the house as a system, where everything affects everything. For two separate Georgia homes, and for two separate builders, we have designed homes that have achieved below 1.0 ach50. The first one, the Grant Park Residence, tested at 0.77 ach50 at the final inspection for ENERGY STAR Certification. We also designed a third Georgia home that achieved less than 3.0 ach50, without the use of spray foam or ZIP System.

We’re currently working on projects now where the homeowners are interested in the same (or better) performance so they can have low energy consumption, increased comfort and indoor air quality, and long term durability. We’re seeing a trend…

Built Tight, Ventilate Right

It’s a really good idea to design and build for a home as tight as possible. Doing so brings with it the need to provide fresh air for the people in the home, because oxygen-rich outside air is being kept from getting inside. In an earlier post, I showed you the Zenhnder America whole-house ventilation system (ERV) installed to bring in, and distribute, fresh air to the occupants. It’s one of the most sophisticated systems on the market, and it’s designed to keep a very well-balanced amount of fresh air through a fresh air supply in each room, and exhaust outlets in bathrooms and kitchen. It is also equipped with humidistat and other controls to help keep the relative humidity at acceptable levels.

On Site at the PGH: VIDEO

Here is a quick video of me at the PGH just after the blower door test during the EarthCraft Pre-Drywall Inspection, explain the test and the results. I’m a bit camera shy, so if I repeat myself or sound nervous, that’s why. (who would have thought, I was the main character in my 8th grade acting class!)


written by Chris Laumer-Giddens

16 Responses so far.

  1. Great design Chris and looks like a very well done application of BASF Enertite by Vis Viva Energy!

  2. Paul Wells says:

    Yes it’s a great number! Even better when the doors have not been fully adjusted and allow even more infiltration. I can’t wait to see the final number.

  3. Thanks, Kelly! That was one of the best applications I have seen. VIS VIVA pays attention and gets the job done right the first time. Very pleased with them, the application, and the product. Enertite is impressive… Thanks!

  4. Exactly, Paul! We have a few other penetrations to fill, as well, and we’re anxious to see what fine tuning it will do to the leakage rate! I’m guessing it won’t be dramatic, since the rate is already very low, but it will be interesting to see. Thanks!

  5. Terry L. Walker, Architect says:

    Nice photo. It reveals what appears to be a lateral forces problem. What is the depth of this wall cavity?

  6. Richard Beyer says:

    What standards are you using for IAQ?

  7. Mike Dandar says:

    I finished a 3000 sq ft house last fall that tested .31 ACH 50 I. Southwest MN.

  8. Good work…What is the air barrier material that is shown in your videos installed over your floor sheathing?

  9. David: That is a floor protection material called KleenWrap. It’s used to protect sub-floor, or finish floor, from damage during construction. We mainly got it to protect our slab on grade because the finish floor is going to be stained concrete. We went ahead and put it upstairs where we have Advantech sheathing. Between the amount of visitors, contractors and events that we’ve had there, it really came in handy.

    Here’s more info:

    We also used it during the renovation of our condo. Really helpful…

  10. Richard Beyer says:

    Did you test for TVOC prior to closing the walls in? What did you use for air exchangers and how is the humidity controlled from it’s use? Did you use the assistance of a third party inspector to quantify the foam installed or did you really only on the foam applicator?

  11. […] weeks ago we reported that the Proud Green Home at Serenbe, built by the Imery Group, achieved a blower door (air leakage) test result of 0.70 ach50 […]

  12. […] is a slab-on-grade. The walls are built with 2×6′s at 24″ o.c., and filled with open-cell spray foam insulation. The roof and floors are made from pre-engineered wood I-Joists, and the windows are aluminum-clad […]

  13. […] a HERS rating (some call it an energy audit) on the home. The rating includes diagnostic testing (air leakage in the home (blower door test) and it’s duct system (duct tester)), visual inspections, and energy […]

  14. […] infiltration rate of the building enclosure on this home, before drywall, was measured at 0.98 ach50 (air changes […]

  15. […] of the High Performance Tiny House is less than 0.2 ach50, or 0.001 ELR (Envleope Leakage Ratio). We’ve done it before. We will do it […]

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