The most popular green feature, after Solar and Rainwater,  I get asked about is Geothermal HVAC systems.  There has been a lot of discussion about the cost and cost benefit of geothermal systems.

There is no doubt that geothermal systems are expensive.  That is why it is especially important to maximize the energy efficiency in the building envelope – insulation and windows, prior to considering Geothermal.

Having said that there are numerous advantages to geothermal that a standard system cannot match.

What is Geothermal

A geothermal heat pump HVAC system and a standard heat pump HVAC system are essentially the same.  You have the same ductwork, you have the same heat exchanging coil and fan inside, and the same compressor.

Where they differ is in the media that they utilize to exchange/store the excess heat or cold.

In a conventional heat pump system, the system relies on exchanging the temperature with the outside air, which varies widely depending on the season.

As the outside temperature gets hotter the unit gets less efficient, and as the temperature gets closer to freezing the unit for all practical purposes stops working completely, rather relying on electric heat strips to provide hot air, while the outside unit heats itself up to thaw several times an hour!

Water is always a better heat transfer media than air.
In a geothermal heat pump, the system works with the earth’s relatively stable temperature of around 68 degrees year round.  In Austin this is accomplished with drilling 250-300 foot deep wells, usually one well per ton of HVAC capacity.

These wellheads need to be stand alone, not tied into water wells, foundation piers, or anything else.  As over time they can require maintenance and need to be accessible.

The system runs a closed loop of water through these wellheads, storing the excess heat during the summer and then extracting that heat during the winter.

Cost
As with all things, pricing varies from individual system to system.  A good rule of thumb is between $7,000-8,000 per ton for a new system including ductwork, etc. 

A high efficiency heat pump can run around $4,000-5,000 per ton.

Until the end of 2016, there is a 30% federal tax credit (1-1 credit).  Apparently the IRS recently revised this to state that ductwork and backup heating are not included in the credit.

Heat Saturation
There is a lot of discussion about geothermal systems failing do to heat saturation.  A properly installed system should not fail due to the heat saturation of the ground around the wellheads.  This is accomplished by simply spacing the wellheads further apart and drilling the wellheads deeper.

Over 1,000,000 geothermal (or ground-source) heat pumps are used in U.S. residential, commercial and government buildings. And each year, U.S. homeowners install approximately 50,000+ geothermal heat pumps. As with any system proper maintenance of the compressor and water pump is important to the longevity of the system.

If you have questions about geothermal systems

Contact James Mcgee, Stan’s Heating and Air 512-929-9393
or Tom Rundberg All-Year Heating and Cooling 512-836-2222

Additional Benefits
Beyond the cost and expected payback.   There are some additional benefits that are hard to quantify. 

1.  If your goal is to have a Net-Zero home, or you are considering Solar Energy, than you should consider geothermal.  It is very hard to compete with the efficiency of the unit, especially with the current efforts by Utility companies to make Solar less attractive.
2. A geothermal system can be tied into your hot water heater, essentially providing free hot water anytime the system is in cooling mode.  In Austin from May-October.
3. There are systems that have been in operation for over 30 years.  Expected life span is 20+ years.
   
4. There can be no outside unit.  If you are tired of hearing your outside A/C compressor running day and night, the geothermal unit is considerably quieter.  Although newer quality heat pumps are quite a bit quieter as well.

In 2012 the City of Austin developed the Value of Solar Tariff or VOS, and set 12.8 cents as the amount it would credit consumers for the solar you produce on your roof (you pay for 100% of all the electricity you use regardless if it is provided by AE or produced on your roof).  In 2014 AE dropped the VOS to 10.8 cents, with no city council approval and no input from consumers. 

For 2015 the City Council is finally having a public discussion about the VOS.  In June I spoke at the City Council Committee on Austin Energy.

Two improvements are being proposed by Austin Energy.

1.       Any annual credit gained from a homeowners rooftop solar panels will be rolled over from year to year rather than zeroed out.

2.       The VOS will now be a rolling average of the previous four (4) years, and VOS for the current year, based on a complex formula.  For 2015 the underlying VOS is going down from 10.8 cents to 10.0 cents, but because it is now a rolling average the 2015 VOS will be set at 11.3 cents.  Based on the rolling average the 2016 VOS is projected to be 10.9 and 2017 will be 10.7.  2018 although not included could be around 10.3, all the while NG prices are rising.

Austin Energy’s General Manger, Larry Weiss and VP Deborah Kimberly presented the 2015 update to the VOS to the City Council. 

During the first presentation, about the overall Power Supply Adjustment (PSA) Austin Energy talked about how they were going to have to raise everyone's PSA because the cost of Natural Gas is going up.
And then 15 minutes later in the second presentation about the VOS, AE talked about how the VOS was going to go down because the guaranteed price of NG used in the formal was going down.

Council Member Laura Morrison and Chris Riley asked the majority of the questions, and they noted the above disconnect in NG pricing.   They talked about the need for the VOS to reflect the huge increase in the ERCOT Offer Cap from $3,000 per MWH in 2012 to $7,000 on June 1, 2014 and then $9,000 on June 1, 2015.

In 2013 the final features of the home a 9.2kw solar array and a rain water catchment system were added to complete the journey of energy independence started in 2003.  We have been entirely Net-Zero since 3/15/2013, in-fact returning 2,190 kwh to the utility grid.

The cascading design of the home fits well with this extremely difficult lot.  This design also saved all the major Oaks by radiating off of the main living area, creating a multitude of unique outdoor living spaces.

The unique details of this home abound with warmth and whimsy, maintaining the character of the owners while considering the impact to the environment.

Designing a home in our hot/humid climate to include passive solar techniques is difficult.   However, several design techniques incorporated in this house work well, including natural day-lighting and ventilation through a "one room width" design strategy and two "thermal chimneys."  The home is oriented to the Northeast and heavily shaded with trees, so much so that there are no roof areas available for Solar PV.  Two ground mount structures were designed to accommodate the 18.4kw of on-site Solar PV.

The building envelope of this Net-Zero home combines three different techniques; 20” thick Cast Earth Walls constructed from limestone screenings (waste product) and decomposed granite; 10” thick R-26 Perform Wall ICF, and conventionally framed spray-foam walls. 

The roof system of 9.5” of spray foam creates a conditioned attic that helps the efficiency of the mechanical equipment, and reduces dust/allergens.

The home is conditioned with a Geothermal HVAC system and an Infinity Heat Pump.  We are also experimenting with a Solar Thermal radiant heat flooring system in the Great Room.  Water Heating is preheated with the waste heat removed by the Geothermal during the summer.

Other Sustainable principles include; salvaged trusses, 100yr old French doors, salvaged cabinets, a rain water catchment system, and an abundance of native plants.

One of the discussions that comes up in almost every client meeting, when discussing Sustainable Design Principles is solar panels.  The question is “Is producing electricity with solar panels on our roof cost effective,” and the answer is finally YES!

Cost
The cost of installing solar panels varies from installer, according to David Dixon of Native, the cost for a system with a standard inverter is around $3.00 per watt.  And a system with a micro-inverter is around $3.20 per watt.

Rebates
Austin Energy is rebating $1.25 per watt, on a first come first serve basis.

You may qualify for a 30% federal tax credit to install a solar PV system, including labor costs. Visit the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy for federal incentives information.

How many panels

How many solar panels will you need?  That’s a tough question.  It depends heavily on your overall goals.  Most homeowners install between 6kw and 9kw of solar panels, however, if you are trying to get to where you are producing the majority of your own electricity you might need as much as 15-18kw.

If we take the 9kw system as an example, the cost after Austin Energy’s rebate and the federal tax credit is around $11,000.  The system will produce about 13,000 kw per year, saving you somewhere around $1,300 per year, so about an 8.5 year payback.

The fight against rooftop solar
Recently a new dialogue about rooftop solar is occurring across the country.  It to complex an issue to discuss here, yet you should be aware of it prior to making the decision to invest in solar panels.

I always say “you can’t overcome an inefficient house with solar.”   Invest in making your home as energy efficient as possible and then consider solar.

In 2012 the City of Austin developed the Value of Solar Tariff or VOS, and set 12.8 cents as the amount it would credit consumers for the solar you produce on your roof (you pay for 100% of all the electricity you use regardless if it is provided by AE or produced on your own roof). 

In 2014 AE dropped the VOS to 10.8 cents, with no city council approval and no input from consumers.   This change affected every solar consumer's expected payback by 15-20%.

There is nothing to prevent AE from lowering the VOS further in future years, and with the growing effort of utilities throughout the country to minimize and discourage rooftop solar, there is every likelihood that they will.

The mountains of Angel Fire, New Mexico are the backdrop for this wonderful 4 bedroom custom home.  Built in 2004 by well renowned builder Ray Renfroe of Blue-Ray Homes.

The mountain home nestled within towering pines was inspired by the southwestern architecture of the region, with a decidedly modern design appeal.  The home has an open living concept and numerous unique features, including vaulted pine ceilings, ‘vega and latilla’ ceilings, kiva-style fireplace, and smooth diamond plaster finish in the great room.

Recently rated 5-stars by the Austin Energy Green Building Program, 125 Clubhouse Drive, is a southwestern style inspired home for Ed and Benita Johnson, my parents.  The home was designed to be a modern take on their love of Southwestern Mountain living.

The Design Concept for the project, was to design a home meeting the ascetic of the client, yet include as many sustainable features as allowed by their budget.

 A metal roof, geothermal HVAC, and Marvin Integrity Windows were principle elements of the home.  A Northeastern orientation, large overhangs, and awning over East and West windows were some of the passive solar design elements.  We did 9.5" of spray foam at the roof deck, and a combination of 1" of high density foam and 2.5" of low density foam in the walls.