Making Sense of Passive Home Design
One of the newest environmental hot-buttons is Passive Home Design. Actually, nothing new. Architect’s designs today hearken back to ancient times when our ancestors paid attention to their environment, chose caves facing south, overhangs on the west, with heavy exterior ramparts and internal temperature moderation.
The late 1800s brought us numerous engineering feats that would minimize the need for passive energy conservation design. We have today a resurgence of “passive design” features. What’s old is new again, just like furniture and architecture. While ancient in application, it takes on new meaning in our climate energy mitigation.
The objective of passive design is to maintain comfortable living temperature in our homes and workplaces that reduce, if not eliminate, the need for auxiliary heating or cooling which typically accounts for up to 40% of our energy uses. California is less disposed to wide temperature fluctuations, but nonetheless it is a big energy hog. In the simplest terms, passive design is:
proper solar orientation,
robust exterior envelope, and
minimized energy consumption.
Today this applies to all new home construction, where it’s easier to install from the beginning, but it can also apply to existing homes, 60 to 100 years old, and even multifamily apartments.
There are some who would like to codify “Passive Design”, like LEED which was popularized in the 2000s. While still applicable to commercial, LEED has fallen from grace by creating punch lists of sometimes elusive objectives that simply don’t work for everybody. Like America’s diverse population, every home and apartment is different. So, the best path is to look at all your options, choose the best for you and maintain the course.
We here in the North Bay are extremely lucky. Our temperature range is free of freezing and extreme heat…… Well, maybe not until this year. But it shows how important orientation, envelope and reducing energy can be. There are thousands of tricks and here are just a few often overlooked.
Even in existing homes, adding overhead exterior awnings, not decorative canvas junk, over south and west facing windows can add wonders to home energy conservation even with older low insulated windows. While exchanging old windows with new high performance units is best, as a general rule, stopping the solar heat from entering the structure before it hits the window or structure is always true. Outer metal screens, metal or wood awnings, all contribute to energy conservation while maintaining our beloved North Bay views.
We can discuss insulation all day but checking, caulking and filling all wall and window gaps can save up to 15% of your energy losses regardless of building age. Even if your house insulation is 50 to 70 years old, it can still work for you.
Of course, our homes creating energy as we are using them, both living and cooking. A big deal is heat recovery. A key is being able to recycle and re-circulate the air, removing heat and pollination. Naturally, in the winter, our heat is going to the attic, but it could also be recycled in a heat pump to save energy. Even existing homes can have heat pump units that can reduce energy consumption from 47% down to as little as 12%. When looking at heat pumps or furnaces, ask about ERV, Energy Recovery and Ventilation. They should be at 90% efficiency.
As a general rule, mechanical fan air circulation is the most effective form of air conditioning. Our bodies are built to detect moving air before picking up temperature changes. Whenever possible, use and install ceiling fans.
One of those little things often overlooked is whole house attic fans. Sucking all that heat out of that upper cavity in the summer and even in warm sunny winter days can help enormously. There are solar attic fans, but they don’t generate enough energy to really drive a good attic fan when required by the temperature. Power supplements are essential.
We could go on forever, but the simple truth about Passive Home Design is thoughtful solar and envelope protection while reducing energy usage will make our homes and the planet more livable. You don’t need a magician or even an architect, only and intuitive vision of where you want to be. Go for it.
Chris d Craiker AIA/NCARB has been designing passive, sustainable homes for over 40 years