On the One Hand...
...the Proud Green Home at Serenbe has been a kind of Experimental House for High Performance Design and Construction. Some of the features, products and practices we're trying for the first time with this home, others we've used or done before, but they are still relatively new to the industry. To name just a few...
- ...a fairly sophisticated fresh-air ventilation system, also known as an ERV, Energy or Enthalpy Recovery Ventilator
- ...a Ducted Mini-Split heat pump system with ceiling and attic concealed air handlers
- ...roof mounted photovoltaics (PV) for site-generated solar power and domestic hot water
- ...flashing tape to air seal the envelope instead of caulk
- ...on-going energy monitoring by Southface Energy Institute
- ...a ventilated rainscreen product behind all lap siding for moisture control
- ...an insulated sheathing product at all exterior walls for thermal control
- ...advanced framing techniques throughout to conserve resources
- ...achieving "net-zero" energy consumption
- ...lots of energy modeling
- ...and the list goes on.
We're also attempting to certify the home through these programs:
On the other hand...
...the home is designed and constructed with very conventional construction materials and methods. We produced a set of construction documents and specifications. The foundation is a slab-on-grade. The walls are built with 2x6'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 wood Low-E windows with a low U-Value and SHGC (solar heat gain coefficient). None of this is out of the ordinary, or hard to get or difficult to do.
Details, details, details...
We've talked a lot about the construction details of this home, starting with a close look at the slab on grade foundation. In Part I of a series on the High Performance Details, we showed how to control the flow of moisture. In Part II, the control of heat flow, and in Part III, the control of air. All three of these are critical to the performance of a home, and not just at the foundation.
The above grade exterior walls and roof are just as important. In fact, the entire building envelope should be a continuous barrier to control moisture, heat and air. In other words, the house should be designed and built as a single system, where every detail effects the other. In a post about Designing a Perfect Wall, we talk about this and how an effective well-executed building envelope can minimize infiltration, heat loss, and moisture intrusion.
Drum Roll, Please!
Earlier this week, Jodi and I spent the day inspecting and testing the home that we worked very close with award-winning builder, Luis Imery of The Imery Group, to design, build and certify. The results of these tests showed that Luis and his sub-contractors executed the high performance details and specifications extremely well.
In April, we performed a blower door test of this home, and the results were excellent, then. We achieved 0.72 ach50 before the installation of drywall, which is about 10 times below the maximum allowed by the 2009 IECC. We mentioned in our blog post about the results that it was just above the maximum allowed infiltration rate of the Passive House standard of 0.6 ach50.
As a result of the testing on Monday, we are happy to report that...
...THE PROUD GREEN HOME HAS A FINAL INFILTRATION RATE OF 0.23 ACH50
This is 1/3 of Passive House maximum and 35 times tighter than the current energy code, the 2009 IECC.
...THE PROUD GREEN HOME HAS ACHIEVED A HERS INDEX OF -2
...THE PROUD GREEN HOME IS PROJECTED TO PRODUCE MORE ENERGY THAN THE HOMEOWNERS THAT LIVE IN IT WILL USE.
...THE DUCT WORK FOR EACH OF THE THREE MINI-SPLIT SYSTEMS IN THE PROUD GREEN HOME HAS A DUCT LEAKAGE RATE OF NO MORE THAN 4.8%
...THE PROUD GREEN HOME WILL BE CERTIFIED:
- EARTHCRAFT HOUSE PLATINUM
- ENERGY STAR, VERSION 3.0
- EPA INDOOR AIRPLUS
- EPA WATERSENSE
Well done, Imery Group!