Insulation and Air Infiltration Prevention
The envelope of the house was insulated by virtue of the structural systems we used—Insulated Concrete Forms (ICFs) for the foundation and lower level and Structural Insulated Panels (SIPS) for the upper walls and roof. And Weathershield windows and doors have a very low U-Value, which is the measure of thermal conductivity. The lower the U-Value, the better.
All this is great, but it’s not enough to ensure that no air can seep into the house. Here are the additional measures we have taken on all exterior walls:
- Sprayed foam in all exterior cavities and crevices from the lower level to the attic.
- On top of the foam, installed traditional fiberglass insulation.
- Sprayed foam around exterior electrical outlets and switches.
- Sprayed foam around all windows and doors.
Part of the LEED® certification process is verification inspections by an expert called a LEED for Homes® Green Rater. The insulation was inspected and we passed with flying colors! The house will have one more field test just before we move in to our home. The Green Rater will conduct a blower door test which will measure any envelope air leakage and identify the location so that it can be corrected.
Now, you may well ask, if the house is that air tight, how can you breathe? The answer: by installing an Energy Recovery Ventilator (ERV). We’ll cover that in our next article which will include a discussion of indoor air quality.
Our interior walls, are insulated with Roxul,® an inorganic material with 40% recycled content. Roxul® actually helps in earning points toward our LEED® certification because of its characteristics:
- non-combustible and chemically inert which helps indoor air quality,
- resistant to mold and bacteria
- does not sustain pests and vermin
- provides excellent sound absorption.
Heating and Cooling
It makes sense that if a home’s envelope is very tight, the energy efficiency increases. That’s one of the major reasons LEED® certified homes use less energy. The heating and cooling system must be sized properly. I mentioned in the first article that our HVAC (Heating, Ventilation and Air Conditioning) load has been calculated at 3 ½ tons. A house the size of ours, without the measures we have taken to ensure a tight envelope, would typically be calculated at around 12 tons!! Having a much smaller system has saved us “tons” of money!
But what HVAC system to choose? Because we did not want a traditional heating and cooling system based on fossil fuels, we chose a geo-thermal system. Geo-thermal is a water to air heat pump which uses the moderate and constant ground temperature as its source of energy to heat and cool and provide domestic hot water. It is a tried and true technology, and the predominant choice as an alternative system to those which are fossil fuels-based. It qualifies for the 30% federal tax credit. Our system would be more cost effective because we could install ground pipes horizontally rather than in deep wells.
However, in August, our plans unexpectedly changed when I spoke with an environmental engineer from California. California, with it’s sky-high electrical rates, is very innovative in increasing energy efficiency. That might be a lesson for us all, but that’s another discussion! In any case, he told me about a relatively new system manufactured by Daikin called Altherma. He believes, as do other mechanical contractors we’ve spoken with, that this system will eventually replace geo-thermal in the United States! They maintain that the system is as efficient as geo-thermal, has the same environmental benefits and life expectancy, but costs far less to install. Quite a claim!
Well, we were intrigued but there was a problem. While this system has been widely used in Europe since 2006 with over 50,000 systems installed, the product is comparatively unknown in the U.S. except for some test sites and relatively few installations. We researched, consulted, and ultimately decided to be the first new, single family home on the east coast to install Altherma! We could only do it because we have, as a partner, an adventurous mechanical contractor, with a sound reputation for high quality, who was willing to embrace this new (to the U.S.) technology.
Why, you might ask, would we want to be guinea pigs? Because we are interested in using and promoting affordable, green technology. Geo-thermal systems are out of the price range for many people, especially when wells need to be drilled. Daikin Altherma is half that cost while still being a solid environmental choice. And it ends up being only about 15-20% more expensive than a fossil fuel system.
- What is Daikin Altherma? I asked a Daikin engineer in Texas to explain the system in layman’s terms. It is an outdoor air to water heat pump which extracts heat as energy from the outside air. The heat pump extracts the energy at a certain temperature, increases that temperature, and transfers it inside through refrigerant piping to the Hydrobox. The Hydrobox heats the water that then circulates and heats the home through low temperature radiators, floor radiant heat or fan coil units. By reversing the process, the system cools the home in summer.
- What does Daikin Altherma do? It uses a renewable resource (outside air) to heat, cool, and produce domestic hot water. The hot water tank, available in either 50 or 80 gallons, contains two heating elements: a heat exchanger at the bottom where the hot water from the Hydrobox circulates and an extra 3 kilowatt electric heater at the top which serves as a booster as needed.
- What makes Daikin Altherma a better choice? What really separates the Altherma heat pump from others is its unique inverter compressor technology. It adjusts the speed of the compressor to suit the heating or cooling demand. Therefore, the system rarely operates at full capacity, and consumes only the energy actually needed.
This results in three major environmental accomplishments:
- High percentage of energy from renewable source. Daikin Altherma gets 66-80% of its energy from the outside air, a higher percentage than other heat pumps, because of the efficiency of the inverter principle (referred to above). For every 1 kilowatt of electricity consumed, it generates 3-5 kilowatts of heat or air conditioning! That’s a good return on investment!
- A high Coefficient of Performance (COP). COP is the ratio of the output heat and the energy used by the heat pump compressor. The Daikin Altherma heat pump boiler has a COP of 3 to 5, which means that the pump delivers 3 to 5 times more energy than it uses!
- Low CO2 emissions. Daikin Altherma typically reduces CO2 emissions by 30-50% compared to traditional heating systems.
That’s the story of Daikin Altherma as I understand it. We are comfortable in our decision to integrate this new technology into our home and we sincerely welcome mechanical contractors, the skeptical, the curious and the adventurous, to come by and see it for themselves.
Solar Thermal System
We hesitated to install a solar thermal system for heating hot water because Daikin Altherma does a pretty good job of producing domestic hot water. However, our goal is to reduce fossil fuel energy consumption as much we can. Our adventurous mechanical contractor recommended Viessmann, a German company, whose system has been successfully used with Daikin Altherma in Europe. We have a good southern exposure on our roof where two solar thermal panels are installed, and, with the 30% tax credit, it was affordable.
The Viessmann system will produce domestic hot water or supplement the radiant heating system in our lower level slab. Because the Europeans are so far ahead of us in alternative, renewable energy, it is not surprising that Viessmann makes solar panels with high solar yields without using toxic heating liquids. And the panels integrate into our slate roofing system.
So, our solar thermal system will produce approximately 75% of our domestic hot water needs at no additional cost and with no pollution! Daikin Altherma will supply the rest. While the return on investment may be 10-15 years, this is a substantial advancement of our environmental goals, not all of which are measured in dollars returned.
We had considered, and rejected, using a wind turbine for the generation of electricity because the options we looked at for residential use had more drawbacks than advantages. They were very big and expensive, noisy, a danger to birds which fly into the blades, and not terribly efficient in producing energy. We decided we would wait on new photo-voltaic technology to develop and get cheaper.
But, along came a wind turbine that eliminates the drawbacks and produces more energy: The Honeywell Wind Turbine, manufactured by WindTronics, which developed a “Blade Tip Power System.” I spoke with a representative of the Michigan-based company. He explained that their engineers wanted to find a way to increase the energy output from turbines. They achieved their goal. Their wind turbine begins generating energy with winds as low as 2 miles per hour compared to the traditional turbines which require 7.5 mph winds. Here’s how:
- Starts generating power at lower speeds because it has no gears. The traditional turbine generates power through a central gear and rotor, which creates resistance, and requires higher wind speed to begin turning. Without gears, this resistance is eliminated. Traditional turbines turn a generator. The Honeywell Turbine becomes the generator!
- Creates more energy because the blades were designed differently. The Honeywell blades are “fatter” and shorter than the thin, long blades we’re used to seeing. Winds come into contact with fat blades at the perimeter or “at the tips.” Hence, no gears required.
Happily, in the process of achieving their goal, the drawbacks of traditional turbines were eliminated:
- Quiet operation—Noise is reduced and vibration eliminated because the blades are shorter wind is deflected very differently, and they are stabilized so they don’t flex. This results in noise levels less than 35 decibels (according to a government web site, a library whisper is 40 decibels).
- Save the birds—The copper coil assemblies at the tips, where the energy is created, needed to be covered. So the engineers enclosed the blades with a nylon wheel. This had the wonderful consequence of making the turning turbine wheel visible and distinguishable to wildlife. The traditional turbine, when turning, becomes virtually invisible to birds.
- Low maintenance—Because they are no moving parts, there is almost no maintenance
- Lower cost—The Honeywell Wind Turbine, installed, is about half the cost of traditional turbines and is eligible for the 30% federal tax credit with no limit. Some states and local utilities also offer credits and rebates.
- Extra Benefit—By hooking up this turbine to dedicated electrical circuits, it can serve as a back-up generator when the power goes out! The Smart Box controller stores power generated by the turbine.
The wind turbine should be about 33’ high with no obstruction to the prevailing winds. Because we are on a cliff, we will be able to install ours on a pole on the ground. They can also be installed on the roof of a home. The turbine itself is 6 feet in diameter and weighs 170 pounds.
We are in a Class 3 wind zone, considered moderate, with average wind speeds between 8–12 miles per hour. However, given that we are on a 40’ cliff overlooking a wide expanse of the Potomac River, we anticipate average wind speeds higher than that. But even at the lower speeds, it is predicted that the Honeywell Wind Turbine will provide 2–3,000 kilowatts of electricity per year in a Class 3 wind zone. A typical U.S. household consumes 10,000 kilowatts per year. That means this turbine could generate 20-30% of annual electricity! Because of the additional energy efficient features we’ve incorporated into our home, our percentage could be
For anyone considering alternative energy for electricity, this new wind turbine, backed by the reputation and name “Honeywell” will provide a much faster return on investment than either a traditional turbine, or a photo-voltaic system. Good news for the pocketbook and the environment! Perhaps it’s time for more of us to consider “owning the wind”!
In the next, and final article tracking the building of our green home, we will talk about the materials and systems which ensure high indoor air quality, an important element to healthful living. We’ll also feature our energy-efficient appliances, “green” fireplaces, and our extensive use of LED lighting, a technology ready for prime time!