Martin Holladay from Green Building Advisor talks about the pros and cons of the Passivhaus standard. He also explains why he believes the German standard is not the best approach for the North American climate.
Interview with Martin Holladay
He started out as a builder and remodeler, building single family homes, additions and renovations in Northern Vermont in the United States.
About 15 years ago he got into publishing, first as an editor at the Journal of Light Construction and then later at Energy Design Update.
Martin built his first house in 1974
Martin's First House was a Learning House
Martin describes the first house he built for himself and how it followed passive solar principles. It was not an airtight construction though.
He calls this a ‘classic hippy house' in the sense that it was thrown together with found materials and inexpensive items that he picked up from the dump.
The Solar Years
Martin explains some of the history of how green building advanced through the years.
As early as the 1940s, MIT researchers were looking at different ways of collecting solar energy.
Active solar systems used pumps and blowers as well as some mechanism for storing solar heat.
Martins says: “If it was a solar air system the heat was usually stored in a rock bin, usually in the basement which was literally a large bin of rocks through which heated air would be blown. Then the air would later be blown through the rocks on a cold night and some of the heat would be gathered up that way or more commonly in large tanks of water. And solar collectors on the roof, water collectors or air collectors would – with means of pumps or blowers – transfer this heat to the storage system.”
Passive Solar Homes
Passive solar houses aimed to use the design of the house to maximise solar gain and not use pumps or blowers.
With most of the windows on the south side of the house and fewer on the north, Martin says these houses heated up quite nicely on a clear sunny day.
There were drawbacks though. They lost a tremendous amount of heat on cold winter nights because of the large amounts of south facing glazing. So they had the reputation of being uncomfortably hot on sunny days and uncomfortably cold at night!
The Saskatchewan Conservation House was built in 1977
The Saskatchewan Conservation House was a Breakthrough
Instead of just gathering solar energy, this house also experimented with super insulation. So it was a house that was built on airtight principles and was tested at about 0.6 air changes per hour at 50 pascals.
It had R40 walls, R60 ceilings and used triple-glazed windows. Clearly these types of specifications have been recommended ever since in cold northern climates (for super insulated houses).
In 1985 The Superinsulated Home Book (affiliate link) was released and a whole movement advocating super insulated houses took off.
The Traditional Approach to Passive Solar Home Design was Abandoned or Modified
Martin explains that at this stage there were two opposing views of the best way to build a low energy house.
“The traditional passive solar people thought that you could get there by collecting lots of energy and the super insulation people thought that collection of energy was not really the issue. The issue was building a tight enough envelope that you didn’t lose energy and on balance I think the super insulated group has been proven correct and a lot of the early ideas of so-called solar house design have long since been abandoned or modified.”
The Passivhaus Standard Requires Cold Climate Builders to Invest in an Extraordinary Amount of Insulation
Martin believes that the goals for annual energy use required by the Passivhaus standard – the most famous of which is 15 kWh per m2 per year – are fairly arbitrary.
He continues: “By pegging an energy budget on the standard he [Dr Feist] required cold climate builders to invest an extraordinary amount of money in insulation that will never foreseeably be recovered in any possible energy savings.
“When true believers in the US started copying the Germans using the Central European standard in our climates they were ending up with 14 inches of rigid foam under their concrete slabs, they were ending up with R100 insulation in their attics and they were sometimes paying $6,000 or $10,000 for reducing tiny amounts of annual energy use that could easily have been supplied by a $400 solar panel producing electricity. It was this kind of absurdity that created a backlash in North America.”
For this reason Martin says the Passivhaus standard has no global validity.
The More Insulation You Use, The Less Effective it Becomes
Insulating infinitely does not make sense, so there will be a point where it is no longer cost effective.
For example, doubling the thickness of the insulation will cut the heat loss in half, but each time it's doubled it'll mean spending more and saving less energy.
We can only estimate how much to spend on insulation.
Martin explains: “You guess at the lifespan of the building, you guess future energy costs, you put a dollar figure on the amount of energy you will pay over the lifetime of the building and you try not to spend more on insulation than will ever be saved in energy.”
Global Warming Mitigation Efforts Need to be Cost Effective
While it could be argued that very thick insulation saves the planet, if this is only includes houses for the wealthy – that are extraordinarily expensive – this is probably not a wise investment.
Money should be focussed where it has the greatest potential to reduce CO2 levels.
Passivhaus is Not a Religion
While Martin praises the Passivhaus standard for focussing on the right things, he says it's not a religion and it shouldn’t be blindly followed.
He also hopes that it doesn’t become enshrined into building codes because it takes away flexibility from builders.
There Needs to be a Massive Investment in Renewable Energy
In order to preserve the planet for our kids, it is a must that we become free of fossil fuels.
This means a huge investment in photovoltaic arrays, wind turbines, tidal energy (to some extent) and so on.
Local Communities Need to Embrace Renewable Energy
Martin is troubled by the fact that in the US it is becoming increasingly difficult to site renewable energy installations.
This is because local interests oppose wind turbines and in some cases PV installations as well because they are afraid that it will be a blot on the landscape. Unfortunately this comes at a time when we need to be moving at a faster pace, not a slower pace.
Efficient New Homes Alone Will Not Impact Our Climate Crisis
The timetable for building new homes is an entirely different timetable from the one required by our climate crisis.
Martin stresses we have to get a handle on this crisis within the next 10 or 15 years, or we are very much in trouble.
So building new super insulated homes does not address this issue. It is weatherization (or retrofitting) of existing homes that will be most significant.
There are clearly many other things that could be done outside construction.
1. Juraj Mikurcik asked, “What’s the biggest barrier in the uptake of large-scale, multi family Passivhaus in the US?”
2. David Cummings asked,”What are your thoughts on the marriage between natural building and Passivhaus and embodied energy?”
3. Thomas Langley asked, “Is it better to pay the extra money to go all the way to Passivhaus standard or do as builders all recommend and compromise on airtightness to save money?”
Our Question for the Comments Section
Is getting Passivhaus certification important for your project?
New York, New York – Las Vegas
Back From New Media Expo
I've been in the United States on a business trip to attend New Media Expo. It was very worthwhile and I met some amazing people who are also trying to change the world for the better with their blogs, podcasts and online videos. Unfortunately at the end of the conference, perhaps due to information overload and a lack of sleep, I had a psychotic episode and ended up in hospital.
Although I want to tell you this story (if you're interested) I did not feel that the House Planning Help Podcast was the right place to do it. Luckily, Ellory Wells, invited me onto his podcast and I shared the tale with him.
My Empty Flight Back from Las Vegas
I said in the introduction to this podcast that I was shocked by how few people were on my plane travelling between Las Vegas and London Gatwick. Here is the proof! This photo was taken in the air and has not been doctored.
There must be a better way of organising flights so that planes are always at capacity?