The Folly of Suburban Greenfield Development

Green building in Denver isn't just about the home itself.  The location of the house can be four times more important for the carbon footprint, making it the single most important topic for this blog and for cities in general.  We're not alone in this opinion.  The TED prize has announced next year's winner, The City 2.0.

So what to do with all the land that the big builders have reserved for exurban single family homes?  Apparently the farmers are buying it back at a steep discount for farming

If this topic gets you agitated, then read this article from Atlantic Cities.   It's loaded with links to important studies that support a greener homebuilding paradigm*:

http://www.theatlanticcities.com/housing/2011/12/missing-link-climate-change-single-family-suburban-homes/650/

* the greener paradigm doesn't involve electric cars and photovoltaics in the exurbs.  My favorite study is the one that shows people are happier if they can walk, not drive, for daily life.

Lighting Efficiency Summary, 2011

This list is taken directly from a Martin Holladay article at GBA:

Here are some relative lamp efficiencies:

• "Indancescent bulbs produce about 14 to 17 lumens per watt.
• Low-cost LEDs produce about 15 to 25 lumens per watt.
• High-quality LEDs produce about 40 to 70 lumens per watt.
• CFLs produce about 48 to 60 lumens per watt.
• T-5 and T-8 linear fluorescent tubes produce about 98 to 105 lumens per watt."

And I just found this increased efficiency LED bulb that kicks out 94.4 lumens/watt:

  

http://www.amazon.com/Incandescent-Replacement-Illumination-G7-Power/dp/B005FU5406/ref=pd_cp_hi_3

Even though in the article Martin states:

• "For now, screw-based CFLs are the best bulb choice for residential lighting.", I think LEDs have just reached the tipping point. 

How Does the Demise of Big Builder Magazine Relate to Southwest Denver?

As I've been saying for a while, destroying greenfields in exurbs is a business model that is slowing down and may end for a long time.

A symptom of this is the announcement of the end of Big Builder Magazine.

If there are any Big Builder types thinking of what next to do with their lives, here's an idea:

Start a land bank in SW Denver, where there are hundreds of homes available for $50k to $100k.  These prices don't seem to be going up any time very soon, but they are very competitive with the cost of greenfield lots.  Throw in the fact that they are eight times closer to the jobs and entertainment of Denver's city center, and you start to think they may eventually be worth a lot more than those far-flung lots.

Now add in some recent pro-density changes in Denver's zoning code, and you have a pretty compelling business model.

2011 LED Lighting Update

At $10, LED light bulbs finally make sense for your most-used fixtures.

For green home designers, it means you should stick with medium base fixtures everywhere.  The LEDs also operate plenty cool enough for those small closets with shelves.  I'm not sure how you will convince the building inspectors, but when incandescent bulbs are illegal, that should solve the problem.

Some folks aren't fully convinced:  http://www.greenbuildingadvisor.com/blogs/dept/green-communities/let-there-be-light-gu24-base-cfls-and-leds#post_comments

But these holdouts won't be promoting CFLs much longer.   Economics and common sense will bring them around.

And remember, CFLs still suck

Important New Solar Tank from Bradford White

Bradford White now has a natural gas backup solar tank available for single tank SDHW systems.

Here's the description:

http://www.bradfordwhite.com/images/shared/pdfs/specsheets/507-B.pdf

This means that the old solar rule "You must have a two tank system if your backup is a gas fired tank-style water heater" is now wrong.

Single tank systems ALWAYS win the efficiency and cost contests in every report I've ever seen.  There is less area for heat loss, less dollars spent on tanks, less real estate occupied.  

But here's the most important (but least obvious) advantage of a single tank system-- if there is solar heat available, it rises up to the portion of the tank that is normally heated with the backup source.   Now the heat loss of the backup tank is made up by solar, not gas or electric.  In a two tank system, a recirculation pump or thermosiphon would be required to accomplish the same thing.

In theory, I like this new tank.  It works simply by placing the temperature sensor higher up in the tank.  That means the lower half of the tank will be cool until solar is available.  What seems  a little magical is how does the heat reach the top of the tank without heating the bottom of the tank, since the burner is still at the bottom?

Well, in an 80 gallon tank, let's just say the burner has heated the top 40-60 gallons by 6am.  Now everyone in the household takes their morning shower and uses 40 gallons.  Since the thermostat is high up in the tank, it doesn't see the new cold water that is now in the bottom of the tank.   The burner doesn't come on, and solar will heat up the bottom of the tank, and if there is excess solar heat for the day, it rises up and helps keep the burner off all night as well.

This latter effect is significant for tank-style natural gas water heaters, because they typically lose 30% -43% of their heat per day to the room they are in.  You definitely want to replace that standby heatloss with solar if possible.  Single tank design is the easiest and best way.

There is one missing piece to the puzzle for winter and low solar days.   If the top of the tank finally drops below the thermostat setpoint, the burner will fire until the thermostat is satisfied.   Since the heat reaching the thermostat must travel through the lower part of the tank, the “solar” section of the tank will be hotter than necessary.   Hot water in a solar tank always hurts solar efficiency.   B-W doesn’t report by how much, and I think somebody needs to find out.   Otherwise, solar curmudgeons will never be convinced to use this tank.

Matt Carlson of Sunnovations is also recommending single tank systems:
http://www.sunnovations.com/sites/default/files/Sunnovations_Newsletter_August2010.pdf

Heat Pump Water Heaters Redux

Michael Chandler at the GBA reports that manufacturers are on the verge of releasing "split" heat pump water heaters:

http://www.greenbuildingadvisor.com/blogs/dept/green-building-blog/stuff-i-learned-joe-lstiburek-s-house

This is great news for those of us who just couldn't figure out where to put one of today's non-split HPWH:

http://greenbuildingindenver.blogspot.com/2009/08/heat-pump-hot-water-heater.html

What's the Greenest Foundation System for a New House in Denver?

The conventional wisdom in cold climates for basements (since we stopped hand-digging them) has been "if you need to go down 4' for a crawlspace foundation, why not just dig another 4' and throw in a basement? The marginal costs are very low per square foot, definitely less than building the second floor. Historically, however, unfinished basement square footage is not allowed in the multiple listing service database.

Habitat for Humanity in the Denver area even takes some criticism because they usually choose volunteer safety over basements. No one can get hurt by accidentally falling into a crawlspace foundation. For the same reason, they have eschewed the second floor until recently as vacant land has become scarcer.

My cost analyses, however, are showing me that a frost-protected monolithic slab is more cost-effective than a basement as long as the land is cheap. Once the price of land reaches about $20/sq. ft., then a basement may be required by the homebuying market.  In other words, the neighborhood is so expensive that the buyers expect the extra square footage of a basement.

The tipping point in favor of slab-on-grade over crawlspace is that the slab can be the finished floor. Stained concrete is still trendy, bulletproof, and saves at least $3/sq.ft. on your floor system.

My concrete floor is six years old, had zero maintenance*, and looks just like the day we moved in.

The thermal mass and the way it buffers the temperature is just a bonus.

Unfortunately, slabs are all but incompatible with modular construction.   Houses from modular builders always have a wooden joist floor system for shipping rigidity, so there's no opportunity for a slab floor.

A Slab is green because:

A slab is much easier and less expensive to insulate properly than a crawlspace or a  basement.

No ventilation required, and no water problems if it's a few inches above grade.   It uses less money and resources to construct.   It has less chance of failure or air quality problems.

The biggest drawback is the lack of easy remodeling.

*Cleaning is not maintenance.