The 5 Tenets of Passive House Design -

by Peter VanderPoel

The need to reduce carbon based energy is well known. Producing nearly 40% of carbon emissions, the building industry is a prime target for carbon reduction. Turning to increasingly sophisticated, additive solutions has been the go-to for industrialized nations for more than a century. Reducing reliance on fossil fuels, however, would seem to suggest a different path- a simplified solution rather than more complex, high-tech responses.  Passive House offers an approach that uses well known techniques and materials to lower the need for energy to make both residential and commercial spaces more comfortable, quiet and energy efficient, with the added benefit of reducing costs. There are 5 principles that are the basis of the Passive House design method. These, coupled with more exacting construction and rigorous testing can help meet both energy reduction goals and improve the built environment at home and in the office. This series of essays will explain the 5 principles of the system.

But first: some trivia

Q1- What 3D geometric form provides a maximal volume for a minimal surface area?

A1- The sphere

Q2 - What building type uses that fact for that specific reason?

A2- The igloo

In an igloo, the maximal volume is the living space, the reason the form is created. The surface area is where heat is lost; less surface area means less heat loss. Snow is used because it is the only material readily available and the ratio of air trapped within the matrix of the snow particles makes a reasonably good insulator.

Igloo - Inuit

Other examples:

New England ‘Salt Box’. A staple of  17th and 18th century communities, the form developed to respond to prevailing the cold climate of the Northeast.

Saltbox - New England

The starting point was the English home but the main material shifts from English stone, a durable but labor intensive material found in England to the plentiful wood found in New England. Fireplaces, typically at the end of the home in Europe, were moved to the center to keep as much of the precious heat in the house during the cold New England winters. The south face of the house was 2 stories, with windows packed  there to harvest the southern sun to warm the interior spaces. On the north side, the facade was minimized by limiting the exterior wall to one-story and providing a large, sloping, roof to turn its shoulder into the north, winter winds and shunt them over the house. In that low, 1 story space to the north, was the storage room for farm equipment; this enclosed, uninhabited space provided additional insulation for the cold side of the house. The proportions of the house, like the igloo, was compact to maximize the living space while minimizing the perimeter. Alternately, housing types developed in the south were more elongated and oriented to encourage the passive cooling provided by breezes flowing thorugh open windows.

The prototypical Swiss Chalet was similarly considered. Farm animals were kept in lowest level for ease of access but also to utilize the rising heat from cattle to help warm the family that lived on the middle level which, in turn, was insulated by hay stored in the attic level.

Chalet - Switzerland

Ancient Persians created wind catchers that funneled breezes down and into their homes, often times passing this breeze across water in a basement to further lower its temperature through evaporative cooling, making structures more comfortable in a predominantly hot, dry climate.

Wind Catcher - Persian

All these buidling types have been designed to take advantage of the circumstances of climate to make the living spaces more comfortable while minimizing the use of added energy to temper the space.

The focus of the Passive House model is to reduce energy costs mainly at the perimeter relying on a high-quality exterior envelope to dramatically reduce energy loss across that barrier with some additional help from traditional methods: sun for heat gain in cold climates and natural breezes to cool in warmer ones.

Passive House is a design/construction approach that can reduce energy use by up to 80% compared to a ‘code designed’ house. The dramatic reduction in energy provides cost savings to the Owner, but also better positions the house to be net-zero. If energy use is reduced, then expensive, heroic energy production and storage is unecessary; modest power generation will suffice.

What passive house brings to the sustainability discussion is not centered on high-tech, cutting edge materials, or complex mechanical systems developed in in laboratories, but rather the application of well-known principles comprehensively applied and rigorously tested.

This series of essays is intended to explain the fundamental principles of Passive House design.

Next time: Tenet 1 - Grandmother’s crocheted blanket...