Energy Value Houses

Here are the 5 winners of the 2010 Energy Value Housing Award.  Details are at the NAHB Research Center (a subsidiary of the National Association of Home Builders) web site.

What strikes me is that these houses look like “normal” houses, appear to cost about the same to construct and have so much better energy efficiency.

[Update 8/21/10: see details on the AZ house, 1st photo below, at end of this entry]

AZ, $97/sqft, 0.2 ACH50

TX, $165/sqft, 0.16 ACH50

MO, $167/sqft, 1.17 ACH50

MI, $198/sqft, 1.24 ACH50

AR, $/sqft not avail, 1.1 ACH50

In the pictures  I  included the building cost per sq ft and the ACH50 number; that is the number of air changes per hour when the house is pressurized/depressurized at 50pascals with a blower door.

Comparing construction costs is of course very difficult.  “Normal” houses range from $80 to $200 per sq ft.  The five houses in this list range from $97 to $198 (with one where no price is indicated), so they fall into that normal range.  Of course the range in normal construction depends on all sorts of factors like level of fit-out (e.g. a plain kitchen vs. a granite counter, high end cabinets etc. etc.) and external appearance and trim items.  You can see the obvious differences in the photographs.  The other difficulty in comparing construction costs is that these houses are one-off projects with commercial and academic sponsors.  The unique nature of the building will increase costs but the sponsorship will hide some other costs such as research and design.

The ACH50 numbers range from 0.16 to 1.24.  That is way below the existing median of 8, and the target level, under existing programs, of 5.  Leaky old houses can get to 12 or so.   These featured houses are so much better!  It proves that even with stick built construction you can build a tight house.  Of course at that level of tightness you need additional mechanical ventilation.   Three of the houses state that they have Heat Recovery or Energy Recovery ventilators (HRV/ERV).  I am sure the other two have similar systems, just not listed them.

It can’t be soon enough when houses like this are the standard expected by new home owners.

[Update 8/21/2010]

I have had some further information from the owner of the Arizona house – at the top of the winners list above.  They love the house, and by the end of the year it will certainly be a plus- energy or “LTZNE” house (less than zero net energy).

The chart shows Heating and Cooling degree days (HDD, CDD) supplied by the local weather station.  The black line represents the power that the panels produce – which became operational a little less than a year ago.  The yellow line shows actual consumption. Clearly, the area between the curves in the winter months is less than the area between the curves for summer months – meaning that by year end this will almost definitely be a LTZNE house.

The house has 27 solar panels on the roof and a solar hot water heater (with electric assist).  The owner has had no electricity bills for two months now.  They have a balance of about $150 that will roll over to pay for the more energy-consuming months (and when the daylight hours are shorter).

Leave a Reply