In which I try to clear up some misconceptions.
I recently got in the middle of an interesting Twitter discussion including our favorite one tonne wonder, Rosalind Readhead, and a few architects and engineers who work in the Passive House world. Rosalind doesn't like the idea of airtight homes, and prefers more traditional methods of ventilation:
What I have seen with many air tight buildings is black mould. I keep my window open for fresh air circulation. We are not robots we are humans— Rosalind Readhead 🌍 (@Privatecarfree) December 19, 2019
I used to be the same, particularly in those years when I was active in heritage preservation, and my pitch was that we had much to learn about keeping warm or cool from old buildings. I described them as being "not relics from the past but templates for the future."
For a long time I believed that we should learn from Grandma's house, promoting traditional building technology like double-hung windows, high ceilings, big porches, lots of cross-ventilation. I liked thick masonry walls because of their thermal mass. I even liked gas stoves! In winter, I believed that the best solution for saving energy was to turn down the thermostat and put on a sweater.
Like almost everyone else in the industry (I trained and practiced as an architect) we made improvements. Add insulation. Get double glazed windows. Get better furnaces. Try to caulk up the leaks, but not too much because I needed that fresh air to keep the humidity down and prevent mold from growing on the cool walls. Lately, maybe add smart thermostats and a solar panel or two. There wasn't really much science to it, but it sort of worked. There were codes to tell me how much insulation I needed and where to put the poly vapor barrier and engineers to tell me how big my furnace should be, but that was kind of it.
But over the years, my views changed. For one thing, the climate changed; nights no longer cooled down as much and it got harder for people to live comfortably without air conditioning in summer. In winter, all those leaks through my brick walls and double hung windows meant I was burning more fossil fuels to keep warm.
I also realized that I was doing what transportation consultant Jarrett Walker has brilliantly labeled "elite projection." I had a brick house with big windows on a quiet street shaded by big trees, so of course, this is the perfect solution for everyone!
When in fact, Grandma's house isn't affordable and doesn't scale. This is why I have become such a fan of Passivhaus or Passive House. As I noted when I first wrote about my transformation:
If we are going to get people out of their cars, build cities that are walkable, cycleable and desirable for families, there has to be housing that is denser, comfortable, healthy and quiet. These days it also has to be resilient in the face of climate change and infrastructure breakdown. The way they built in Grandma’s day isn't going to cut it anymore.
With climate change, we are also getting changes in air quality, after decades of improvement as coal furnaces and smoking people were removed. The air quality outside can be worse than that inside. It's one reason that opening the window isn't always the best solution. Rosalind isn't alone in thinking that natural ventilation is better; it's still being marketed by companies like Velux who write:
"The contents of indoor air include gases, particles, biological waste and water vapour, which are all potential health hazards. It is recommended that you air out your home three to four times a day for at least 10 minutes at a time, with more than one window open. Also, air out your bedroom before you go to bed and when you get up in the morning."
But this is all so random. Our streets are full of PM2.5 particles and automobile exhaust. It can vary block to block, day to day. In a Passive House design, you can open the window if you want, but there is a mechanical ventilation system with filters that is not at all random. It gives you the fresh air you need all the time.
Yes highly insulated & airtight buildings have warmer internal surface temperatures (no cold bridges or uncontrolled draughts), but adequate ventilation is still essential, this assures that typically passivhaus homes have RH of air between 40-60% (mould doesn't like that) pic.twitter.com/c28R0iCBYQ— Juraj Mikurcik (@JurajMikurcik) December 19, 2019
Then there is Rosalind's concern about mold in airtight buildings. It's a problem; if you get high humidity and cold walls, you get mold. But in a Passive House design, the walls are warm thanks to their blanket of insulation and lack of thermal bridging, virtually the same temperature as the air. The humidity is controlled too, so you rarely see mold. And it has nothing to do with robotics, just science and a lot of insulation.
Rosalind also complains that airtight houses are overheated, when the WHO recommends 18 or 19°C temperature settings. But the World Health Organization, like most people, even professionals and mechanical contractors, do not understand temperature is just one factor in comfort. What matters just as much is Mean Radiant Temperature, the complex interplay between our skin and the walls surrounding us. If you have cold walls, you will turn up the heat to feel warmer, which means it can hold more moisture, which can then condense and feed more mold. Meanwhile, because you are losing heat to cold walls, you still feel chilled.
But finally, and most importantly, in her manifesto, Rosalind Readhead has called for Net Zero Carbon 2025. "A de-carbonisation programme that is less extractive, less resource intensive, low energy, quicker and less expensive to implement." But the route to decarbonization in building goes through Passivhaus. I have written before about how to do this,
The four radical steps we need to take to fight climate change:
- Radical Efficiency: This is the most important, far more so than Net Zero. The best way to achieve this is through the Passivhaus standard. Yes, air tightness is critical to it, but try it, you'll like it. As far as I am concerned, it should be the bare minimum standard if we are going to not fill that carbon bucket and break 1.5°.
- Radical Sufficiency: How much do you need? We have to build less stuff, extract fewer materials. We have to design the places we live and work so that we can get between them on foot or bike. But we also have to design them so that they are sufficiently resilient to adapt and protect us in changing conditions.
- Radical Simplicity: Another reason for going Passive House. It's simple and doesn't need any fancy technology or robots. Just lots of insulation and really careful, simple detailing, careful assembly. It is the ultimate in low tech design, just sitting there, passively storing heat or keeping it out. There are a few fans and filters for fresh air, but that's it.
- Radical Decarbonization: We have to build out of natural, renewable materials that store carbon, and minimize the upfront carbon emissions of everything we make or build. We also have to radically decarbonize our operating energy sources. We have to cut back on our use of fossil fuels to the point that the oil and gas companies are forced to leave it in the ground because there is so little demand. That means getting our homes off gas, and again, the best way to do that is Passivhaus.
Why am I standing on a Low Tech New Deal platform for the London Mayoral elections? We have years not decades to prepare. LTND Faster and cheaper to implement, less extractive and resource intensive. Getting the basics in place quickly. Focusing how the carbon budget is spent— Rosalind Readhead 🌍 (@Privatecarfree) December 19, 2019
I have spent the last year being inspired by Rosalind Readhead her one tonne lifestyle and her quixotic campaign for Mayor of London. She is a role model; I am actually going to be using it as a model for my Ryerson University lectures this year and trying to have my entire class do it. But we can never truly achieve a one tonne lifestyle unless we reduce our homes' energy consumption to Passive House levels.
We have an Extinction Rebellion because we are in a climate crisis. I don't know where it is going to end. But I have noted before where I think we have to start: with Passivhaus.
Every building must have a proven level of insulation, air tightness, design and component quality, so that people can live in a comfortable and safe environment in all kinds of conditions, even when the power goes out. This is because our houses have become lifeboats, and leaks may well be fatal.