Learning from Passivhaus Building

The people of Green Building Store (UK) have generously produced and published a freely available online movie about some of the challenges they faced in a Passivhaus construction project in the UK. Though I am wary of taking on the Passivhaus standard as is (reservations I’ve written about in posts about Passivehaus and Rural Studio) I am also trying to be careful not to pour the baby out with the water. There is a lot of common sense in Passivhaus and much of it is excellently communicated in this movie. You can view all the parts here or possibly start with this embedded video and then continue to each consequent part:

So, with much curiosity and interest I watched the movie (reviewing some of the chapters numerous times) and made some notes of things that I hope to incorporate into our building process. This list does not include the core-issues of Passivhaus construction (insulation, minimal thermal bridging, air-tightness, ventilation and passive solar gain) which deserve careful context and consideration – especially when it comes to hemp-lime construction which introduces unique qualities to both the construction process and the resulting structure.

Design & Details

It is invaluable to spend time designing and paying attention to details before the actual construction process. Construction is an established process and skill which carries with it a taken-for-granted attitude. Professionals have a way of doing things and will prefer to do things the way they’re used to doing them – which may lead to cutting corners in design and to on-site improvisation.

This can be destructive in a project where new standards of building, new materials and new techniques are involved. Taking the time to plan things in advance, to drawing diagrams & making calculations creates a thoughtful path towards a desirable result. Of course it is inevitable that unforeseen challenges will arise during construction and that some changes and improvisation will be required – in which case a plan gives some indication of how far you’ve deviated and what you need to do to get back on track.

Special attention should be given to details. I’ve been working on a wall-to-floor detail for weeks – compiling all the information and knowledge I have come across, reconsidering it in the context of hemp-construction, our house design, minimizing costs, minimizing the use of concrete and relying on locally available materials. There is no ready-made template for what we are doing, there are many options to choose from, there are many considerationt to incorporate. We could take the easy path and hire foundation contractors and let them do their thing – but that would lead away from the kind of warm, pleasant, ecological and efficient house we hope to live in and bring us to the standard cold and humid house that contractors have been building in Romania for may years.

Team Work

A typical construction process tends isolate and compartmentalize knowledge and skills. We would consult with an architect to design our house. Then we would pass the plans to an structural engineer who would need to figure out how to support our house. Then we would pass the architectural and structural engineering plans to a heating engineer who will try to provide an adequate heating solution within the existing constraints.

This kind of approach can lead to an inefficient process and an inefficient house. A good engineer can provide a structural solution to meet almost any need – but at what price? How much extra work, materials, construction effort and waste may be required to implement the engineered solution? Similarly a heating engineer can theoretically heat any space – the question is how expensive and complicated will the system be and how much energy will it consume? This is a brute force approach.

We are trying to put together a team that will work together during all phases of the project. We’d like everyone to be there to provide input at every stage of the project. We’d like the architect to provide input on choosing good land and on siting of the house on it. We’d like the structural engineer to make suggestions on architectural decisions that may lead to simpler and more efficient construction using less materials. We’d like a heating-engineer to review the size of our spaces and to make suggestion that may improve the energy-efficiency of the house.

It takes integrated and out-of-the-box thinking to create the kind of integration that leads to a house that facilitates an “eco” existence.

Opening Details

I have been wondering about how to go about properly insulating openinsg like windows and doors. The movie offered some very useful tips about these issues and these are the ones I noted:

  • Windows should be placed at the center (depth) of the wall.
  • Windows should open inwards – placing the thicker part of the frame on the outside for better insulation.
  • Special sealing tape (such as Pro Clima Contega FC) should be applied between the rough structural opening and the internal wall and then covered by the the internal render.
  • Special sealing tape (such as Pro Clima Tescon) should be applied between the window frame and the rough structural openings.
  • A concrete slab should not extend to the door opening to prevent heat loss through it.
  • The door opening slab requires an insulated and weather resistant material (such as fiberglass).

A big thank you to the people at Green Building Company. This movie has been very educative and helpful.

Passivhaus

Introduction

Passivhaus is one of the terms out there in eco-green-sustaintable building land. It may look like its spelled wrong but that’s because its originally from Germany. It represents a very strict and high standard of energy efficiency in a building. It isn’t (yet) an official requirement or standard but it is gathering momentum as an unspoken standard.

There are three complementary core ideas behind the idea of a Passivhaus:

  1. Complete and thorough thermal insulation of the house which prevents conductivity of heat from the inside-out or the outside-in.
  2. Complete air-tightness which prevents exchange of heat through air leaks (windows, doors, pipes, chimneys … every opening needs to be sealed!).
  3. An efficient ventilation system that both exchanges air (from the outside and the otherwise airtight house) and does so without losing heat.

This is one of those images that is better then a thousand words. The apartment building on the left is standard/traditional building while the apartment building on the right is built according to the Passivhaus standard. That’s the bottom line of Passivhaus – keeping the heat from escaping means you need to expend less energy to heat the inside.

Extreme!?

I have come across Passivhaus numerous times in recent weeks and my recurring personal impression is that it is too extreme:

  • It seems like more of an academic indulgence then a practical construction practice.
  • It’s objective and success is measured in a single number – the amount of energy needed to heat a square-meter of space.
  • It demands rigorous builing disciplines which require uncompromised excellence in construction.
  • It demands the use of specialized insulation materials which can be expensive (especially if you consider the ecological foot-print involved in manufacturing them).
  • It creates a house that demands constant attention, maintenance and proper use by its residents (every window opened and every hole drilled in the wall is a potential energy hazard).

All of which results in a delicately balanced system: if it isn’t absolutely sealed, perfectly ventilated by a carefully installed system and properly used it just won’t work. There is no room for error. This maybe OK in a scientific experiment but not so for life, nature and people.

In any case it doesn’t feel right for us: we have a limited budget, average construction capabilities, standard building materials, etc. We are going to do the best that we can with what we have. It’s an 80/20 kind of thing – where 20% of the effort takes you 80% of the way you need to go and it would take another 80% of effort to go the rest of the way. We’re aiming for a good middleground – pushing the limits of what we have – but that, by definition, is not enough to go for 100%. Passivhaus is uncompromising, but we live in a reality which demands compromise.

“A passivehouse is cost-effective when the combined capitalized costs (construction, including design and installed equipment, plus operating costs for 30 years) do not exceed those of an average new home.”

Source: PassiveHouse.com

I am hesitant to relate to this statement as that may give it unwarranted legitimacy –  cost is just too narrow a perspective to view ecological housing. But if I do meet it head on, as is, I would say that it sets its sights much too low. I hope to build a house where the combined capitalized costs are much lower then those of a new average home (whatever that is). I also hope to build a house who’s qualitative effects (both for us and others) far outway it’s economic effects.

Maybe Passivhaus is, for the time being, a high-end building experiment? Maybe in time it will spawn accessible, affordable and feasible techniques, solutions, technologies, practices … that can become a defacto standard that simply makes sense to follow? For now, it is out of touch with us and our needs.

Humidity

Having said all that exploring Passivhaus has brought to my attention a factor I had not taken into consideration in all of my energy research: Indoor Air Quality. I have been following a very basic intuition: “generate heat” in trying to solve a problem we’ve been having for many winters: “being cold”. Most of my attention has been on how to preserve and generate heat (space and water) effectively.

I had not given any thought to one of the central themes of Passivhaus: quality of air. Quality of air (assuming there is good ventilation) is strongly effected by humidity … and humidity effects the overal experience of temperature … cold is much colder when humidity is too low and heat is much hotter when humidity is too high. I have experienced the effects of humidity in warm and cold temperatures in Israel and I have seen it (as accumulated moisture and mildew) in almost all Romanian homes I have visited.

I don’t know yet enough about ventillation and humidity.

Hemp

One of the much praised qualities of hemp masonry is it’s breathability. It seems to have a natural tendency to absorb and expel unneeded moisture. I don’t yet have enough information on the overall effects of hemp on moisture, ventilation or quality of air indoors – but I do have a good feeling about the effects of hemp!

Resources

Following are some of the resources I came across and consumed in trying to understand Passivhaus: