The elements of a dream house are shared by many: year-round, all-hours comfort, healthy indoor air quality, minimized mechanical operating systems and reduced energy use intensity, and perhaps most importantly, a durable, resilient, low-maintenance, aesthetically beautiful home.
Embracing the five pillars of the International Passive House principles for design and construction ensures these outcomes. Fortunately, there is also a symbiotic relationship at play - reducing the energy use intensity of a home brings with it all of the aforementioned benefits, and striving for these benefits will in turn reduce the overall energy use intensity of the home (or even large commercial buildings). The Passive House pillars work for all buildings! Win-win!
Air Tightness: We recommend, first and foremost, detailed attention to air tightness to minimize energy losses. This will be the foundation supporting the ensuing goals of comfort, durability, resiliency, and reduced mechanical operating systems.
The quality of air sealing should be measured by a HERS rater with a blower door test at specific phases of the construction. Even if not pursuing the Passive House standard of .6ACH50, we recommend aiming for a minimum of 3ACH50, as measured by a blower door test.
Mitigation of energy loss
Throughout California, no matter the climate zone, reducing a home’s conditioning losses through envelope leakage is paramount for ensuring comfort. This air sealing is achieved through careful detailing at specific areas of the assembly, thoughtful sequencing of installations, and the intentional use of already familiar membranes, tapes, sealants, and gaskets at the floor, wall, door and window, and roof junctions. This chart illustrates the potential percentage of energy losses that can be mitigated at these areas.
Reduce Thermal Bridging and Better Insulation: We also strongly recommend undertaking measures to reduce conditioning losses (or, conversely, unintended thermal gains) through thermal bridging. Focus on the home’s structural building materials (foundation, wall, and roof framing members) with the use of continuous exterior insulation, now integral to compliance via the performance method in the 2019 CA building code. The reduction of thermal bridging and the inclusion of greater amounts of insulation are two of the five Passive House pillars. However, in our area of California, there isn’t as much of a need for greater amounts of insulation as in other areas of the country, but rather greater installations of current levels of insulation.
Strategic Window Selection: The type of glazing and doors in a home will play a central role in comfort, resiliency, and energy use. Low U-factor glass, thermally broken frames, appropriate placement of windows, and proper shading elements should all be part of this conversation. Intentional placement of glazing with higher solar heat gain coefficients to gain winter warmth should also be looked at, depending on the climate.
Heat Pumps and Balanced HRV: Creating a more comfortable home via these practices allows one to then reduce the size of the needed conditioning equipment, thereby reducing equipment purchasing costs as well as the operational costs and associated maintenance costs of said equipment. Heat pumps supply both heating and cooling in one system. A balanced fresh-air exchange system with incorporated heat recovery can be used to supply healthy, fresh, filtered conditioned air to living spaces, while exhausting stale air from bedrooms, bathrooms, and kitchen areas, all the while maintaining ambient indoor temperatures.
Utilizing heat-pump heating and cooling accompanied by a balanced ventilation system with heat recovery requires lower amounts of energy than three separate systems - e.g. heating equipment plus cooling equipment plus a whole-house, exhaust-only ventilation fan which is dependent upon air being pulled through a building’s inefficiently constructed and leaky envelope.
A comfortable home at all hours through the entire year operating at a low energy use intensity can then be powered by a small renewable energy photovoltaic system and supported by a battery backup system for periods of sustained power outages as a result of wind, fire, or storms. Additionally, with an improved envelope that reduces conditioning losses, the home will maintain comfortable living temperatures should equipment not be able to operate for any significant amount of time.
The International Passive House standard requires attention to these five simple pillars: reduced air leakage, reduced thermal bridging, better insulation, good window selection and placement, and a balanced HRV system. Begin the pillars with detailed energy modeling before you dig in the ground, and finish them off with a small photovoltaic system atop the roof.