Blower Door Test at NHND to the Pond

This week the HERS rater conducted the blower door test on the New House Next Door to the Pond. This tests the air-tightness of the building envelope and measures the number of air changes per hour and is now required for all new construction in NYS. The NHND to the Pond scored a respectable 49 HERS Index rating and 1350cfm50 during the test.

Older homes, built before building wraps or board sheathing or wall board or spray foam insulation can be very porous in terms of outside, un-conditioned air getting in and inside conditioned (heated or cooled) air escaping out. You might think of this as a "drafty" or "leaky" building. And that was the "norm" for many years in construction.

Nowadays we try to decrease our usage of energy and minimize our impact on the environment (or minimize our financial costs - different impetus for different folks, for sure...) and the newest IECC (International Energy Conservation Code) has forced all but historic buildings to meet more stringent insulation and air-tightness standards so they will use less energy to be heated and cooled.

I've always designed my projects to be "green" and while I haven't sought certification by LEED (Leadership in Energy & Environmental Design) or Energy Star, I have always detailed my buildings to be as environmentally friendly as construction can be, sometimes teaching the contractor or inspector about construction details I've learned about in building science classes.  Being "green" usually means creating the best "building envelope" (line separating inside from outside) we can to keep the building's energy usage down to a minimum. (Rather than all the myriad of other "green" ideas, like Forest Stewardship Certified lumber, or reusing materials from deconstructed buildings, or considering the embodied energy of materials/products we build with, or specifying low water-usage fixtures or low-wattage lighting/appliances, or thinking about other sustainable materials, like wool or cotton insulation batting, etc.)

CI layer visible just outside of framing

Recently that's included continuous insulation.  And often the use of spray foam insulation at key trick spots, like the rim joist. Slab edge insulation and the best windows you can afford all help, along with a lot of insulation in the roof/attic. Click here to see an older post about insulation: 2014/02/insulation-phase-1

HRV (on the right) takes heat out of the air before expelling it out of building

When you start getting a super tight building envelope, you need to introduce mechanical ventilation to ensure healthy indoor air. It may seem counter-intuitive (why not just let the building breath???) but the science shows that tight buildings with (continuous running, even) mechanical ventilation systems use less energy. Click here to read an older post about Heat Recovery Ventilators (HRVs) http://cwb-architect.blogspot.com/2014/06/air.html

Insulated Cellar Access

Whoops! Not quite finished yet!

During the test and other check-point inspections potential problem areas were discovered and some were remediated.  The cellar door access was basically a hole in the building envelope, so an insulated interior stud wall was constructed for the insulated, weather-striped door to be installed into. Also it was found that the continuous insulation and finish specified under the cantilevered floor areas was never installed. When that is complete, our numbers might be even better!

Here is the bright & colorful HERS Index graphic: