Back to: The Home Renovation

With autumn upon us, cool nights have brought me the opportunity to get a good energy audit on the newly purchased home.  My expectations, as any of you who have read this know, were quite low.  And yet…the analysis of the building performance was quite good for a relatively recent, conventional construction, but not nearly poor enough to financially justify a deep energy retrofit or even get a tax break from the Efficiency Maine program.  Basically, the next step is a quandary that require a balance of conservation goals and savings objectives.

Here are some of the facts:

1.  The blower door test revealed an air removal rate of 1500 cubic feet per minute which translates to .30 air changes per hour.  That’s below the .35 rate at which ASHRAE recommends installing mechanical ventilation, such as the Venmar HRV EKO 1.5 (www.venmar.ca ) that we sell at Greenovations (www.seacoastgreenovations.com ).  This sounds good, and if you are judging a house by conventional standards, this is good.  But the bar set by conventional standards is far too low.  Based on the measure of tightness in our home, the size of it (2000sf) and the design (open concept cape), our home is already more efficient than 80% of the homes in New England.  Compared to a new built green home of the same layout, our house is an energy hog.  Here’s why.

A well-built, “green house” will have an extremely low air change rate, if any at all.  For example, a blower door test on a friends similarly designed house with sprayed in foam insulation tested (blower door) at 250 cubic feet per minute of air transfer.  I’m not even sure what the natural air change rate of that house, but for certain, it was nowhere close to the  ASHRAE  metric for installing mechanical ventilation.  You could fart in that house and without  mechanical you’d smell that fart for weeks.  Its need for mechanical ventilation is about 8 times greater than that of the home I just purchased.

2.  Infrared cameras revealed very few gaps in the insulation in our home.  The primary problem, revealed by the camera working in conjunction with the blower door test, was a lack of insulation around the rim joist between the first and second floor.  As well, the attic was insulated with a level of R-30 insulation in the attic, where a minimum of R-50 is recommended.  And finally, the insulation is fiberglass, which isn’t worth much at all.

3.  The cost/benefit problem:  The initial recommendations for improving the performance of the home are to:

·         Insulate the first floor rim joists

·         Weatherize and insulate the attic by pulling about 2’ of the fiberglass away from the top plate and spray foaming it and then placing 8 inches of paper blown cellulose over the top of that

·         Replacing the fiberglass between the ceiling of the drive under garage and the living room floor above it with paper cellulose

·         Insulating the rim joist along the foundation

·         Adding Dow Thermomax to the interior garage wall that meets with the exterior basement wall

All of this, done by an experienced professional would cost $5300 or more.  Based on a software calculation, these measures would lead only to a 13% reduction in energy use and a yearly savings of $200.  That’s a long payback period if you’re thinking of energy bill savings.  And if you’re thinking about reducing your carbon footprint, it’s just not that much.  Ultimately, this is an excellent example of the weakness of building to code.  Standard building codes, which mine followed, are not efficient.  It would have costed little more to make this home efficient.  It would have been a lot easier to energy retrofit, had it never passed code.  Unfortunately, millions of homes are built just like mine, and as people are becoming more energy conscious, they are finding out that the gains are too few for far too many dollars, unless they plan to live in their home for 30 years.  But who can do that with an economic system like ours that makes it hard for people to settle.  The dream of a nice house with a white picket fence was long ago subjugated by the forces of an RV lifestyle.

Another step that would significantly improve my homes performance would be to remove the siding, wrap the building in rigid foam board and replace the siding.  That too is a costly measure, a very costly one.

Unfortunately, our energy audit did not cover mechanicals very much, but never-the-less, the cost benefit analysis’ certainly helped me get a clear view of the whole picture.  As well, it gave be a basis for prioritizing other energy savings measures.

A.  We received a quote from two different solar thermal companies for installing a solar hot water system.  SEA Solar Store in Dover, New Hampshire gave us a quote for a Wagner flat plate solar collector that could produce enough hot water to save us 200 gallons or more of oil per year.  The price – about $10k.  But with Federal and State tax rebates, the final cost would be $6000; only $750 more than the insulation.  The previous occupants of our house used 785 gallons of oil a year.  With our two children we expect to use about the same amount after calculating the amount of energy required for our lifestyle.  (We: hang dry clothes, cold water laundry, 6 months a year I take cold showers, gray water system, no one home during the day, etc.).  Saving 200 gallons of oil per year through the solar system is a reduction of 30% of our boiler related carbon producing energy use.  As well, this represents a $500 yearly savings, far more than the basic insulation choices.

Now generally, I advocate for the reduction of energy demand through insulation and weatherization over renewable and other mechanically based efficiencies.  Most often, it is easier and more beneficial to reduce energy demand than to create new energy.   The low hanging fruit of good insulation and weatherization usually gains more energy savings than the amount of energy renewable can produce.  My house, however, is an example of how much “building to code” is failing home owners.  Had these homes been built smart, the reduced energy demand would far exceed the insulation steps and solar thermal installation I put on my house.  Without an energy audit, however, I may have spent a lot more on insulation and nothing on solar thermal.

I know, this is a long post, but I have one more step to pursue.

We will be improving the insulation in our attic and our rim joists, but not the garage ceiling.  The software program our energy auditor used showed little energy savings to this $2000 step. (About 2%.)  Combining the solar thermal with the other insulation steps could reduce our hot water and space conditioning costs by 40%.  Not bad.  We had also wanted to remove the existing, 80% efficient oil furnace to replace it with a 95% efficient wall hung propane boiler.  After calculating the btus per dollar we would get for each type of fuel ( oil generate 130,000btu – propane generates 95,000btu) and factoring in the efficiency rate of each, we found that the $8000 investment would not save us a single penny at today’s propane prices.  Now, propane is generally considered a cleaner product.  Though it is a petroleum distillate, when propane is burned it is not as dirty to the environment as oil.  One of the reasons we wanted to make the change.  But that is a lot of money for little gain in overall efficiency.  But damn it, I want to be “green”.  Well, another option revealed itself.

We can take that $2000 we’re not spending on insulation, forget about the new oil burner, and install a Rais wood stove (www.rais.com) for about $4000.  Rais makes the world most clean burning wood stoves.  We can use the wood stove to perform half the heating in our home and we can get our wood from a friend who has his own sustainable tree farm not far from here.  Provided we support smart forestry, that would be a very “green” way to go.  Our home would also get the addition of a very stylish product.

And there you have it…how an energy audit can assist you in making smart choices in your goals of creating a sustainable future.

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