Sunday, April 27, 2008

Solar Home on the Wash Park Home Tour

Our personal residence, a "solar Denver Square", built in 2004, is on this year's East Wash Park Home Tour.

This annual event is the biggest fundraiser for Steele Elementary.

Things to look for:
1. High SGHC glass used on the south side.
2. "Poor man's terrazo" diamond-ground and stained concrete floors for thermal mass.
3. Rare indoor swamp cooler that serves as a humidifier in the winter.
4. Infloor radiant heat.
5. On demand hot water.
6. Near-zero exterior maintenance.
7. Low-water landscaping.



“The Substation House”



Green Features

  1. Site is at the south end of the block which allowed unrestricted access to the sun. (little to no shading)

  1. Passive Solar : Large window area on the south walls of the house. The interior temperature swings somewhat because of the heat gain from the sun. After a sunny day the living room temperature will be 68, and early in the morning, it will be 64. A room temperature of 65 feels quite comfortable because the house isn’t drafty and the walls and windows are relatively warm compared to older homes.

  1. Minimized window area on east, north, and west. On the north, to save heat in winter, on the E & W to reduce heat gain in summer and shoulder seasons. Most of the E & W windows are shaded for the same reason.

  1. South window glazing is a special low-e coating with a high solar heat gain coefficient (SHGC) to maximize heat gain in winter. This keeps the space heating cost to $20/month for the main house in the 4 coldest months.

  1. Stained concrete floors provide thermal mass to “save up” daytime heat until nighttime. This process is unregulated and occurs naturally and automatically. 2” thick concrete was poured on the first and second floors. The basement slab is 6” to prevent cracking due to somewhat expansive soil. Similarly, the concrete floors help keep the house cool on hot summer afternoons

  1. Large window well on the south side provides more heat and light than usually found in a basement.

  1. Structural Insulated Panels (SIPs) used for wall and roof construction. SIPs can be described as stressed-skin foam panels. They provide a high R-value and ensure a tight heated envelope (reduced unwanted air leakage). Having a SIP roof and no conventional attic trusses make the attic livable space for very low cost.

  1. Unique indoor-mounted evaporative cooler uses 5 times less energy than A/C for summertime cooling. The airflow is reversed thru the cooler in winter, using the HEPA air filter, thereby serving as the humidifier. The indoor location of the evaporative cooler allows easier maintenance. Denver is one of the best places on the continent for evaporative cooling.

  1. Medium-high efficiency boiler for the in-floor radiant back-up heat and domestic hot water. The boiler is “direct vent” to eliminate the possibility of CO entering the house. The combustion air is sucked in directly from the outside, and blown outside after combustion. The radiant in-floor heat system was installed by Advanced Hydronics. Because the home uses such little backup space heat, this boiler was the best choice at the time.

  1. 3.3 KW photovoltaic system mounted on the garage roof feeds power back on to the grid when it is generating more electricity than the home is using.

  1. The pre-existing red brick building was saved and re-purposed as the home office/shop. (It still has poor energy performance, but a brick insulation retrofit experiment is ongoing. This is a city-wide problem needing a solution ASAP.) Side note: this building was originally built in the late 40’s to store a huge bank of lead-acid batteries. These batteries were part of the electrical grid for the Denver Tramway system.

  1. The SIP construction allowed the easy finishing of the attic space, providing a very useful 3rd floor bonus room. (Conventionally built homes have vented attics, which are hot in summer, and cold in winter, and the single largest cause of heat loss and heat gain.) Design flaw #1: Kevin’s experience with finished attics led him to believe that the 3rd floor wouldn’t need any heat. The assumption was that the heat from below would migrate up. It turned out that the house is comfortable at only 65F, so very little heat migrates up at that low of a temperature, and the third floor needs some heat at times.

  1. Exterior below grade basement/foundation insulation. This is a really important detail that is rarely done correctly in new construction. The result is the basement zone stays at 64 degrees in the winter without any heat from the boiler.

  1. No wood or gas fireplaces. Although we like the ambiance of fireplaces, any room with a fireplace would overheat quickly in this house.

  1. Hot water “D’mand” pump. In each bathroom, the doorbell button summons hot water to the fixtures by turning on a pump for a few seconds. This is much quicker than turning on the faucet or shower and waiting for hot water to reach it. This also saves lots of water. This type of demand system is considered superior to timed recirculation systems that waste heat when hot water isn’t called for in the bathrooms.

  1. Note on “passive solar cooling”: In the summer, the large double doors on the third floor can be opened at night along with the basement windows. Although over 1000 cubic feet per minute of air then naturally flows up through the house, it’s still not enough cooling effect for the two hottest months of summer. Denver’s climate has changed enough to generally require active cooling.

  1. Low maintenance items:

a. Brick and stucco exterior.

b. 75 year stone coated steel shingles. They are much lighter and more hailproof than solid roof tiles.

c. Minimal painted exterior wood surfaces

d. Concrete floors have no maintenance, only cleaning.

e. Minimal roof penetrations mean fewer future roof leaks, and less air leakage. There is no fake chimney that is still put on most new homes. The joint between a chimney and the roof is the single largest source of roof leaks.

f. Low maintenance landscaping, wood mulch for weed control

18. Low Water Landscaping: Although there is a bluegrass play area, the rest of this large lot uses xeriscaping and a drip system for irrigation. Summertime water usage is usually under 10,000 gallons per month.