Posted by: Scott McCullough | August 1, 2013

PHI Tight

Yesterday we received our final Energy Star Certification Report, which includes an air leakage report, a fuel summary, and our HER score.  In all there are very encouraging numbers, and other not so encouraging numbers.

A somewhat disappointing number was our HER score of 44.  This means that our home consumes 44% of what a home built to today’s building code would consume.  This is very different from the unofficial goal that Jess and I have of being net zero while not using fossil fuels on-site.  The fact that all of our appliances are run by electricity including our radiant floor boiler contributed to significant penalties compared to if our appliances were fueled by propane or natural gas.

In reality we will rely much more on our wood stove for heat than the Energy Star software can reflect.  We have radiant heat on our basement and first floors, but we will likely only use the basement at a low setting and use the wood stove for the rest of the house.  We have an electric clothes dryer, but for half of the year we hang our clothes outside on a line to dry.  We have a conventional electric oven in the Kitchen though hope to use our wood stove oven as much as possible.

One encouraging number reported was our air leakage rate of 0.51 ACH @50 pascals, which is 15% tighter than the Passive House Institute standard of 0.60!  As described in previous blog posts, we did use a number of air tight building methods including Zip System sheathing and tape, rubber sill seal, foam seal and rubber gaskets for doors and windows, foam and taping of shell penetrations.  Possibly even more important was that the type of house we built may have ended up having the large role in controlling air leakage that we anticipated.  The timber frame wrapped in multiple layers of continuous insulation created a redundancy where a leak in one layer is covered by the following layer.

Despite the somewhat disappointing HER score we did manage to max out our rebate amount at $4000.  Without the PV system our score would have been 60.  So in addition to the state, federal, and utility rebates we received; at $100 per point we are getting another $1600 for the system.  Total system gross cost $17,719 – state rebate $3,750 – NHEC rebate $2,500 – Federal tax rebate $5,315 – Energy Star bonus $1600 = Total system net cost of $4,554.  At 12.4 cents per kW that is a 7 year payback.

Every new home should be seeking Energy Star Certification.  As long as your not cutting corners, meeting the requirements is easy and the amount of documentation needed is minimal as compared to other certifications such as LEED.  And compared to other certification programs, Energy Star pays you and not the other way around.


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