What is Really Essential During the Build of the Green House? (Lecture by Catherine Mohr)

Jul 26

E-learning, Green Architecture, Movies, Technology Add comments

This video shows a lecture by Dr. Catherine Mohr who is the Director of Medical Research at Intuitive Surgical, a high technology surgical robotics company that makes the da Vinci surgical robot. In addition, she is a Consulting Assistant Professor in the department of Surgery at Stanford School of Medicine. Dr. Mohr received her BS and MS in mechanical engineering from MIT, and has been involved with numerous startup companies in the areas of alternative energy transportation, computer aided design software, and medical devices. She is the author of numerous scientific publications, and the recipient of multiple design awards. Nevertheless, in this lecture Mohr disregards her profession and speaks about completely different topic. In a short, funny, data-packed talk she walks through all the geeky decisions she made when building a green new house – looking at real energy numbers, not hype. What choices matter most? Not the ones you think.

Mohr names herself a geek. She explains that she is an organic food-eating, carbon footprint-minimizing, robotic surgery geek. She adds that as a geek she really wanted to build green, but she was very suspicious of all of these well-meaning articles. She explains that in these articles people long on moral authority and short on data, tell how to do these kinds of things. So she decided to figure this out for herself. On the example of the paper towel she realized that sometimes the things that people least expect — the position in which they put the handle — have a bigger effect than any of those other things that they were trying to optimize.

The thought above was the leading one in design process of her new green house. She and her husband wanted to know, how green could they be? She explains that there are a thousand articles which tell how to make all these green trade-offs. And they are just as she suspected in telling them to optimize these little things around the edges and missing the elephant in the living room.

She explains that the average house has about 300 megawatt hours of embodied energy in it, this is the energy it takes to make it and they wanted to know how much better they could do this. And so, like many people, they started with a house on a lot. The first thing that most of people do is a demolition but it takes some energy. So they decided to deconstruct it, what allowed them to get some of energy back. Then they dug a big hole to put in a rainwater catchment tank to take their yard water independent. And then they poured a big foundation for passive solar. Thanks to that they can reduce the embodied energy by about 25 percent by using high fly ash concrete.

Then they went on to the first thing that was very surprising for them. If they put aluminum windows in this house, they would double the energy use right there. PVC is a little bit better, but still not as good as the wood that they chose. Then they put in plumbing, electrical and HVAC, and insulate whole house. She convinces that spray foam is an excellent insulator – it fills in all the cracks – but it is pretty high embodied energy, and, sprayed-in cellulose or blue jeans is a much lower energy alternative to that. They also used straw bale infill for their library, which has zero embodied energy. When it comes time to sheetrock, she explains that using EcoRock get about a quarter of the embodied energy of standard sheetrock.

After all that work they got to the finishes, the subject of all of those “go green” articles. She convinces that on the scale of a house they almost make no difference at all. Nevertheless, all the press is focused on that. Except for flooring. Because If people put carpeting in their house, it’s about a tenth of the embodied energy of the entire house, unless they use concrete or wood for a much lower embodied energy. So they add in the final construction energy, they add it all up, and they have built a house for less than half of the typical embodied energy for building a house like this.