Our Cool Roof

One of the important considerations in building our green home is the kind of roof to choose.  We decided on a standing seam metal roof, which is somewhat unusual for residential homes in this area, but, there are a number of good reasons to choose a roof like this.  Although metal roofs are common on commercial buildings, you hardly ever see them on single family homes.  The reason?  They tend to cost more than a normal shingle roof, roughly double the cost.  Our particular roof is a Titan Cool Roof made by Custom-Bilt Metals.

First, the lifetime of a metal roof should be excellent- it should have no problem lasting 50 or more years.  Over the long run, the durability should make the extra cost a non-issue when amortized over the lifetime of the roof.

Second, we selected a "cool" roof, which refers not to its esthetics, but its heat-reflecting properties.  It has special coatings designed to reflect heat away from the house.  This leads to a reduction of the urban heat island effect and also reduces the air conditioning needs of the house (but it is counterbalanced by also letting less heat from the sun into the house in winter time).  To keep heat inside the house more effectively, we insulated both the upper rafters of the roof and the "floors" below the attic area.

Third, a standing seam metal roof allows for easy installation of solar panels.  Solar panels can be clipped onto the seams of the roof, reducing the number of roof penetrations needed to install panels.

Cool roof color choices we considered (from left to right):
Weathered Copper, Storm Gray, Old Town Gray

We ended up choosing Weathered Copper, which has a Solar Reflectance Index (SRI) of 34 and Thermal Emittance, E=0.85.

Here's what our roof looks like, with some solar panels (we have more panels on another part of the roof).

One of the most common questions people have about a metal roof is if it's noisy.  In our experience, we find that it is no more noisy than a standard shingle roof.  Because the roof is attached firmly to the underlayment layers of the roof, it doesn't vibrate or have any room to ping when water hits it.  The second common question is, if it's too shiny when the sun hits it.  Ours is not shiny at all, because it has a matte color coating that prevents excessive glare when the sun shines on it.  Overall, we are quite satisfied with our choice.

Choosing our Hot Water Heating System

If you're building a net-zero or green home, you need to pay attention to the energy details.  One of the largest sources of energy use in a home is the hot water heating system.  Thus, it is one of the key areas to consider  carefully.  There are a few likely candidates for hot water heating, and, if you're remodeling or building a net zero or green home these are the ones you'd most likely consider:

• Tankless on-demand electrical hot water heaters
• Solar thermal hot water heating system
• Hybrid heat pump hot water heater

Tankless on-demand electrical hot water heaters work by heating hot water as-needed, instantaneously using a small heating unit, when hot water is needed.  These can be gas or electric powered.  We investigated using an electrical unit since our home will be solar-powered and we wanted as much of our energy usage powered by electricity as possible.  One of the considerations is when doing Title-24 calculations you'll find that these systems are rated at a 0.9 energy factor for minimum efficiency, which is not that great.  That's because normal electrical resistance heating is not considered to be that efficient for Title 24 calculation purposes, even though there are potential real savings due to only heating water on demand.  Another consideration with tankless units is you may need several units in order to satisfy the load and also to reduce the time needed to run water before the warm water reaches the faucet (unless you're able to place one single hot water heater with sufficiently high heating capacity very close to all of the areas that need hot water).

Solar thermal hot water heating makes use of roof-mounted panels which heat waters held in pipes that are heated naturally by the sun to bring the temperature to a higher level so that the main hot water heater needs to do less heating work.  These systems require quite a bit of additional costs in terms of installing the panels and pipes and from my perspective, add more complexity.  Typically this may add a few thousand dollars to the cost of hot water heating systems (likely in the $1500 to $3500 range or higher [reference here]) so the cost-effectiveness of such a system may be hard to justify.  You may be able to get rebates and tax benefits from the system which can help offset some costs, depending on your area.

Finally, perhaps the most interesting system, and the choice we made, was a hybrid heat pump hot water heater.  These systems typically use electrical heating, however, they add a small, efficient air-source heat pump to the hot water tank which is able to make use of energy in the ambient air to generate heat more efficiently.  In fact, our Title 24 calculations show it has a 2.4 energy factor for minimum efficiency.  We chose the 50 gallon GE GeoSpring hot water heater which is one of the most efficient hot water heaters available.  Although it's more expensive than a standard electrical hot water heater (probably by about $600 to $1000 more), there are currently $300 Federal tax credits at this time,  and for instance in 2013 PG&E has a $500 rebate.  In other areas, other utility companies may also offer rebates which may offset the costs.  According to calculations from the GE web site, a standard electric hot water heater would use 4879 KWH per hear whereas the GeoSpring is estimated to use 1830 KWH per year [see calculator], which adds potentially several hundred dollars a year in electrical savings.  Also, the reduced electricity usage is an important consideration if you're sizing a solar panel system for generating your own electricity.  So far, it's working great and we have had no issues with it so far.

Sapele Wood Cabinets Arrive!

We've been waiting a long time to get to the finishing stage of our remodel.  One by one, the finishing items are arriving.  We just recently received our kitchen and bathroom cabinets.  Beautiful FSC Certified Sapele wood finish, euro-style (flat panel) cabinets.  Sapele ribbon-cut wood has a wonderful finish that must be seen in person to be fully appreciated.  Sapele is sometimes used to make musical instruments such as guitars.

Choosing Grass- U.C. Verde is it!

California is often plagued by droughts, and so choosing the right grass to grow in your lawn is actually a pretty important financial decision.  Lawns are notorious water sinks, and when you water your lawn you're essentially throwing money out the window.  Fortunately, people have been working to address this problem, and researchers at the University of California have cultivated an especially drought-tolerant, low water variant called U.C. Verde Buffalo Grass.  Buffalo grass is actually a native grass to the area, making it an ideal candidate.  U.C. Verde grass needs about 1/4 the water compared to other typical lawn grasses, making it a logical choice for the are.  Here's some more info on UC Verde.  And here's one blogger's experiences planting a UC Verde lawn and here's another successful UC Verde lawn.

Project Green Home: Passive House in Palo Alto

The Passive House movement is growing and a new Passive House is being built in Palo Alto.....  Passive House designs are ultra-energy-efficient homes with extremely tight energy performance characteristics.  The Project Green Home Blog gives the details of one family's process in building their Passive House, and includes interesting details on the choices they made, such as Selecting High Efficiency Windows.  The unique features of their home are detailed here.

The Minnie House: It Starts Here...

The building of the Minnie House is a great blog to follow. Steve is building a Rocio Romero LV Home in Pacifica. It's really great that he is blogging about the whole process including the costs of building a modern home in the bay area.

The Minnie House: It Starts Here...: "OK, the plan is to build an LV Home on a 7650 sq ft lot that I'm buying in Pacifica, a pretty, foggy seaside community about 15 miles and 15..."

Palo Alto Mitchell Park Library Green Building Elements

Palo Alto is building a fabulous green, modern library in Mitchell Park:
http://palf.org/libraries/mitchellpark/

It has some wonderful ideas incorporated in it to reduce water usage and energy usage and is aiming for LEED Gold certification.

Slideshare presentation here:

Palo Alto Mitchell Park Library Green Building Elements

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