Improving Affordable Housing, Part 3
I was intrigued by Tim McDonald’s presentation at the Greenbuild International Conference and Expo on Wednesday. He discussed net-zero energy capable residential projects built by his company, Onion Flats. He reported that over the past few years the firm has worked towards the creation of high performance residences by utilizing the Passive House standard. Passive House relies on three basic design philosophies:
- Reduce annual energy used for heating and cooling a home to near zero.
- Design the building envelope (roof + walls + slab) to be super tight to eliminate all possible sources of air leaks.
- Achieve the goal of a net-zero total annual building energy usage.
The Passive House standard is derived from the German PassivHaus concept. To meet Passive House standards, homes must be designed so such great energy efficiency that they require little or no furnace capacity. This goal is met by utilizing super airtight walls with very high R-values, typically in excess of R50. Passive House also has a healthy homes aspect to it, requiring 100% fresh air so that no used air is returned into the home. Typically a home’s forced air system only supplies about 10% fresh air as per code, so Passive House is truly a jump forward. Successful Passive House designs use the saved cost from providing a very small HVAC system to offset the increase in cost for the building envelope.
Tim asks, “Why are we putting a premium on sustainability?” By rethinking home design and reallocating funds, the efficiency of a home can be significantly raised without added cost. Innovative concepts include:
- Exploring sunlight penetration for both light and heat when needed and shading the windows when direct sunlight is not needed.
- Considering cross ventilation and using convective cooling strategies, both of which work well for modern, open, airy homes.
- Assessing how we use energy for daily needs, such as home electronics, appliances, and conveniences.
Designing healthy, energy-efficient buildings requires a lot of thought and skill. Finding occupants willing to adjust their living patterns to fully take advantage of all the possibilities for a net-zero energy lifestyle is a bigger challenge to tackle.