Absurdity of Natural Ventilation

I’ve been meaning to post something about the absurdity of the almost religious devotion some people have to “natural” ventilation in a building. How is a double-hung window “natural”, by the way? That’s why I prefer the term manual ventilation.

Fortunately, the Passive House Academy of New Zealand beat me to it with a great Google+ post.

Would you throw your laundry into a river and hope to pick the clothes up cleaned somewhere downstream? Are you doing all your laundry by hand? Do you get fresh air in your car only by opening the windows? Probably not.
Yet, there is this absurd insistence on natural ventilation when it comes to houses – despite research demonstrating poorer outcomes for indoor air quality, comfort and energy efficiency. In many aspects of our daily routines, we accept that a machine can do a better job. What’s different with ventilation of houses? In a mechanically ventilated home, the windows can be opened and closed at will. Freedom of choice! In a manually ventilated home however, the windows cannot be closed without risking the build-up of air contaminants and moisture indoors. The effectiveness of this form of ventilation furthermore depends mainly on the direction and force of wind. In other words: it is relying on the weather. With mechanical ventilation, there is no reliance on power – as in a power outage, occupants can still fall back to manual ventilation. For most of the heating season however, they enjoy great indoor air quality, while saving massively on heating costs, and not having to worry about opening and closing of windows.
Note: ventilation in a Passive House is – deviating from the experience that most of us have with cars or offices – silent, non-draughty, the air is typically not conditioned at all, and sourced filtered directly from the outdoors. Fresh as!

In the past ten years, the efficiency of mechanical ventilation with heat recovery has improved so much that manual ventilation is rarely the most appropriate strategy.

UPDATE: An analysis out of Ireland showed a savings of 643 euros per year for a Passive House with heat recovery ventilation versus natural ventilation.

Book: The Greenest Home: Superinsulated and Passive House Design

The Greenest Home: Superinsulated and Passive House Design

Julie Torres Moskovitz’s book showcases eighteen recent Passive House projects from around the world, including the first certified Passive House retrofit in Connecticut. Duncan Architect was the Passive House consultant for this project.

If I ran the world—or at least the planning departments of the world—every house would be a Passive House (not to mention every school, hospital, office building). Each house in this inspiring book is beautiful on the outside and brilliant within. Each merges bold aesthetics with common principles: they’re well insulated, high performing, and ridiculously efficient in their resource usage. The real mystery is why Passive House principles aren’t standard best practice yet. They will be. They must.

—Allison Arieff, Contributing Columnist, New York Times


Passive House Books

Westport Bauhaus Passive House Retrofit in Treehugger

Before and after shots of the Passive House retrofit project in Westport, Connecticut, an hour or so northeast of New York City. Duncan Architect was the Certified Passive House Designer working with architect Ken Levenson to create a comfortable, healthy, energy-efficient building. Treehugger recently profiled our project and the owner/builder Doug Mcdonald.

Commercial Retrofit in Brooklyn, New York

Increasing the occupants’ comfort and ability to do their job by reducing noise and drafts while also reducing utility bills.

A preliminary blower door test revealed major air leaks in the existing masonry. These gaps were not obvious from a visual inspection and would have created huge problems with water leaks, uncomfortable drafts, noise transfer, and a high risk of condensation and mold growth. Fortunately we discovered them before the drywall went up so that the contractors could patch them.

After the test, the contractor installed regular fans in the windows to create a pressure differential to reveal where the air leaks were. Sophisticated equipment is required to measure the rate of air leakage but not to simply find the leaks.

The next step after installing the mineral wool installation is to put up a vapor retarder—on the warm side—that also acts as the primary air barrier. Intello, available from 475 High Performance Building Supply in Brooklyn, is a “smart” vapor retarder that prevents moisture transfer into the wall assembly while allowing it to dry out if it becomes accidentally saturated. After the air barrier is complete, but before the drywall is up, we will conduct another blower door test to make sure that the building’s airtightness is below the Passive House retrofit standard of 1 ACH50. Finally we will install a service cavity of 1-5/8″ furring to protect the airtight membrane.

Below is a view of the building from the F train platfrom with the old plumbing supply sign painted on the brick and One World Trade Center in the background.

For more information please email greg@duncanarchitectpllc.com

and check out video of a successful blower door test from our friends at Dwell Development in Seattle.

Brooklyn Passive House Video

Brooklyn Independent Television features the energy-efficient retrofit condo, 96 St. Marks Avenue, that I consulted on for architect Ken Levenson. See the Passive House Buildings Project Data Sheet for technical information and haus96.com for the marketing website. Located in a historic district in Prospect Heights, this townhouse renovation combines historic preservation and modern technology for a beautiful, comfortable living space with extremely low heating costs. Comfort is assured by the quality of the building fabric and by giving the owner of each unit control over their own heating, air conditioning, and fresh-air ventilation. This type of retrofit serves as a model for future real estate development in New York City and beyond.

Please contact Gregory Duncan Architect for more information.