What a great name for a recent presentation by James Bill of Zero Impact Architecture at a Build It Green East Bay Guild meeting. The presentation brought some really wonderful insight into the "Passive House" which I would like to share with you here. A "Passive House" is a house that does not require a furnace and uses the saved heat from occupants and appliances to heat the home. Yup. No furnace. Of course, it was the Germans who came up with the concept (who else?) and the European Union has already built 20,000 of these homes. We have about a dozen. That gets slightly embarrassing so, moving on...
The 5&1/2 lightbulbs is basically a metaphor for the amount of energy required to heat this passive house on a very cold day. Like, the coldest day of the year. It equates to about 545 watts heating 750 square foot house. Context? The standard amount is 10 watts per square foot to heat a standard home (see heat calculator). So that would be more like 7,500 watts to heat this home using traditional methods (yikes, and that's a fairly small space). That's almost a 14-fold difference!
Just to note, the average home in America is about 1,500 square feet in size. So, yeah, that would be 15,000 watts. Remember, this is just to heat the house on a very cold day, not for the entire month. Which is why PG&E actually details bills with kilo-watts as the numbers just get too darn big.
Even more amazing is this passive homes requires 0 watts if the sun has been shining (stores that energy up in those solar panels). Beat that, space heater.
So, how did they do it?
First and foremost, with green building it is all about SEALING. Gotta seal up all those gaps - you know, the gaps between boards and such where all those bursts of cold air come seeping through. You would be amazed at how much energy is wasted simply because homes aren't properly sealed and insulated.
Second, they designed and constructed the house very carefully so that cold air isn't seeping in via rooftop or foundation either; adding in extra layers for insulation on all sides.
Side note: ***Even though you are sealing up a house really well you also have to make sure that the house is well-ventilated otherwise you get air-quality issues and pressure problems. The balance between the two is tricky and requires good knowledge of design and systems. It is also paramount to comfort.***
Third, add in your awesome technology: the integrated solar-mechanical system. This requires extensive modeling of systems, climate and other factors to arrive at a functioning integration which will not only harvest and store solar energy properly but will also allow for proper distribution and usage. Not for the faint-of-heart or the mathematically-challenged! This system heats up the water which can then contribute to heating the house itself. Yeah, we do need the hot water still. Yummy, precious hot water.
Finally, they added in all other green elements (which are a given now in green homes) such as sustainably-harvested wood (this is know as FSC lumber or Forest Stewardship Council-certified), fly ash instead of concrete, radon elimination, recycled content and no-to-low VOC adhesives, and water conservation functions to use less water and utilize gray water. All those acronyms can be disconcerting and I will cover these concepts more in later blogs. For now, just know these types of construction methods are important for the health of the environment as well as you. Trust me. <wink>
Now, this is not to say that they didn't run into some obstacles in this project but overall the point is that this is the type of work that is needed to drive a future in green homes. I'm happy to see that the SF Bay Area is really taking a LEED (get it?) on manifesting the green movement in the U.S. I now leave you with a mind-blowing concept of living with no heater and a very bad pun. Happy heating!
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