I just finished a fantastic week at the ACI conference in Austin!! Affordable Comfort, Inc., founded in 1986, is an organization whose mission is to advance the performance of residential buildings through unbiased education. They bring conferences and seminars to places across the country and we were lucky enough to host them this year!
During this phenomenal conference last week I attended 12 seminars, all with deep subject matter and relevance to building science. One seminar, presented by 2 women from New Orleans who have developed a “wash and wear” home they call Green Dream. A home that can be washed, dried out and moved into after a severe flood like the aftermath of hurricane Katrina.
Another seminar was by a woman from Germany who developed “Passive House”, a concept of building a comfortable home that does not need mechanical heating and cooling.
Another about deep energy retrofits; reducing energy consumption in existing homes by 70-90% and challenging North American homeowners to retrofit thier homes in the 1000 Home Challenge as prototypes for others to follow.
You can see this is not about solar panels and rain water collection. There is not a “one size fits all” green building answer to each individual home, budget or family. However, we can go back to the basics and put this simple prescriptive scope into place:
Design – a proper design positioned correctly to solar orientation and with a modest square footage (meaning not 4000 heated square feet!) These free design basics make more difference than money spent on green building materials and devices.
Air sealing – the type of material used is not as important as applying a complete seal to create a tight house. An experienced air sealing professional will know where all of the tricky spots are, every gap is not obvious and every gap must be sealed. Using SIPs , ICF and spray foam insulation can make this process simpler.
Insulation – again, the type of material not as important as the need for a total fill application at the outside envelope of the home. Batt insulation is capable of a total fill application but not as likely because a proper installation is not very simple or common. Blown in cellulose or blown fiber glass will give you a total fill at a good price. Spray foam, while more expensive, will give you a total fill plus provide the air barrier needed. For our climate, insulation must be installed not at the ceiling but at the rafters, creating a sealed attic.
Mechanicals – the type is not as important as the proper sizing and quality of installation. A Manual J is critical in proper sizing of your heating and cooling. With out it, your contractor is guessing and will likely guess high rather than low. This means your system will short cycle costing you money and comfort. Factor in great design, air sealing and insulation; you will likely need much less tonnage than you would think.
Air quality – Can a home be too tight? The answer is no! A tight home is best because instead of having air forced in from dusty attics and floor crevices through air leaks in the envelope we are controlling the air exchanged either by mechanical or passive means. We choose the source of fresh air.
Now we have an incredible, energy efficient green home!! But, even with this quality green design and construction we still have big energy thieves in our home. Three of the biggest are:
Thief #1 – Thermal bridging
Thermal bridging is any variation in the thermal envelope such as windows, unsealed vents or conductive material. Quality, smartly placed windows, good air sealing and insulation will help. What’s left is the building materials them selves, the studs and the slab. In conventional framing, the wood studs and roof framing at R-2 create gaps in the insulation and will conduct heat through the thermal envelope: Thermal Bridging! There are many extreme ways to combat thermal bridging but the most reasonable I have found is to wrap your exterior walls with rigid foam board insulation. This breaks the thermal bridge except for the screws. Insulate the bottom and sides of your slab with Extruded Poly Styrene.
Thief #2 – Phantom load
When you have an appliance or devise plugged in, even when not in use it can still draw power from the outlet. This extra load can be huge, up to 25% in a conventional home, 50% or more in a green home!!! You can use your electric meter to experiment with how much power a device is drawing by taking a reading, then unplugging the device and reading the difference. You can also buy a Kill-A-Watt device to save you a few steps. One of the simplest things to do is use a power strip in each room to “detach” several devices from the power source. Turn off the power strip when leaving the room.
Thief #3 – YOU!
We are the bad guys and if we have sloppy green living habits, we can make a negative impact on our energy bill and the environment. The things that make a difference are obvious: thermostat settings, CFL’s vs. incandescent bulbs, how many computers are plugged in and left running, improperly maintained equipment, using old or inefficient appliances etc…
Here is case study of 11 identical Habitat for Humanity homes in a row with identical orientation, all built with some sustainable features and with solar. The only variation is the people living inside. The difference in energy bill goes from -$40.00 up to $1200.00 per year! WOW, what an enlightening picture!
We can do more good (or bad) than we realize. Clearly YOU can make a difference!!!
Finally, do not think of solar first! This is one of the final elements to install on your home but you must do the proper design and construction or retrofit first. How much PV do you want to buy to compensate for a leaky house, poor insulation and sloppy green living? Building science first, cool green gadgets second!