The technology behind passive houses can be confusing, so weâ€™re cutting straight to the good stuff: The biggest benefits of this energy-efficient construction method.
1. Low monthly energy use and big savings
The most obvious upside to a home thatÂ heats and cools itselfÂ without an air conditioner or a furnace is the monthly energy costs: Theyâ€™re typically close to zero. â€œThere is no downside to a building that uses less energy than its code-compliant equivalent,â€ San Francisco builderÂ Ewen Utting. And Utting notes that passive construction doesnâ€™t take much more in terms of effort, energy, or materials to create a building that performs at its full efficiency potential.
2. High indoor air quality
â€œConventional buildings donâ€™t give you much control over the ventilation because theyâ€™re not airtight,â€ Utting says. As a result, the toxins and particulates from windy days, pollution-spewing trucks driving by, and every piece of off-gassing furniture you own tend to collect and recirculate in your home. â€œIn a passive house, the air is completely and methodically exchanged for fresh, filtered air 24 hours a day,â€ Utting says. The result: Without any effort on your part, potential toxins are given the boot before they reach unhealthy levels.
3. Less sneezing and less cleaning
Since a passive home has a killer ventilation system, it filters out pollen quicklyâ€”a major bonus for anyone with allergies. The airtight building also lets far less dust in (and filters out what ends up in the air), meaning less time spent cleaning.
4. A totally quiet house
Another benefit of airtightness is sound quality. When the doors and windows are shut, the house is almost completely silent. Even ambient noise is reduced since there isnâ€™t central air turning off and on.
5. Flexibility in building materials
Are you super into reclaimed wood? Or obsessed with recycled denim insulation? Or just really into using as many local materials as possible? Great. With a passive home, youâ€™re not restricted to a certain set of certified materials. â€œThe passive house is a performance-based standard,â€ Utting explains. â€œHow you meet the performance criteria is entirely up to you.â€ Local and sustainable materials are encouraged, but you (and your builder) have full flexibility to make the materials choices that make sense for your location and budget.
6. A future-proofed home
While no one can predict exactly where residential building codes will go in the next few decades, the trend is clear: The code will require more energy efficiency and better resource management. By building passive now, your home will more than likely still be compliant in 30, or even 50 years, Utting says.
How to design an ultra-energy-efficient home
No furnace or AC?Â No problem. This â€œpassive houseâ€ in San FranciscoÂ is so energy efficient, it heats and cools itself
A few years ago,Â Yatin Chawathe and Thomas Zambito hadnâ€™t even heard the term â€œpassive house.â€ But when they saw plans for one under construction in the Castro neighborhood, it met their wish listâ€”great views, modern architecture, energy efficiency, and room to raise a familyâ€”so they did what any modern couple would do before deciding to buy: They Googled it.
Their search turned up a lot of information on passive homes, but the most useful result led them to a Seattle man who owned one. He assured them it was the most comfortable home heâ€™d ever lived in.
Chawathe and Zambito didnâ€™t need much convincing. â€œWe really liked the idea of a low-energy house,â€ Chawathe says, â€œand this went so far beyond that.â€ Other than cautioning anyone doing exterior work on the house to not puncture the homeâ€™s insulation seal, the only difference the couple notices with previous houses theyâ€™ve owned is their rock-bottom energy bill.
Back exterior.Â The four-story residence was the first passive house sold in San Francisco. Builder Ewen Utting took on the project in part to prove to colleagues that a market exists for ultra-efficient homes. The home is also built to LEED Platinum standards.
Bathroom.Â The glass shower enclosure, large-format tile in black, and chrome fixtures give the master bath the modern sensibility Chawathe and Zambito wanted.
Master bedroom.Â â€œThe sheer urban nature of the city was a big draw for us,â€ Chawathe says of the view from the master bedroom. â€œI wanted to wake up every morning and be reminded that I live in a dense urban environment.â€ Despite being in the thick of it, Zambito says, the house is completely silentâ€”no sirens, no hum of central coolingâ€”when the windows are shut, thanks to the thick insulation and triple-paned windows.
Kitchen.Â To maintain the homeâ€™s airtight seal, the kitchenâ€™s range hood doesnâ€™t vent outside, which initially gave the couple pause. â€œWe cook a lot of high-heat Indian food,â€ Chawathe says. â€œWe worried the kitchen would turn into a cesspool of spicy, humid air every time we cooked.â€ But their worries were unfounded: The ventilation system quickly clears the air.
Builder:Â ENU Construction, San Francisco;Â enuconstruction.com.Â Architecture:Â Hood Thomas Architects,Â San Francisco;Â hoodthomas.com. Design:Â Rice and De Tienne Designs, San Francisco;Â riceanddetienne.com.
HOW A PASSIVE HOUSE WORKS
A home that is completely energy independent sounds unbelievable. Builder Ewen Utting explains whatâ€™s needed to make it work.
Well-calibrated insulation.Â Proper insulation is crucial in achieving the near-perfect efficiency of a passive home, Utting says. The level of insulation (and the thickness of the walls required to hold it) is decided using an algorithm that takes into account factors such as the homeâ€™s square footage and the localÂ climate. The colder it isâ€”say, in Alaska, where at least one passive home has been builtâ€”the thicker the walls.
A tight seal.Â Although the construction techniques used for a passive house are essentially the same as for a typical home, builders have to be at the top of their game, sealing every hole and seam to make the house airtight. â€œThatâ€™s the passive house approach: Give nothing away,â€ Utting says.
Few thermal bridges.Â In a typical home, heat and energy escape 24/7 through the walls, windows, and doors in places called thermal bridgesâ€”and you wonâ€™t find many in a passive home, Utting says. Triple-paned windows and extra-thick doors (with impeccable seals, of course) prevent air and energy leakage. Want to open a window? Do it: A single open window wonâ€™t affect the house much because thereâ€™s nowhere else for air to leak to or from.
Solar integration.Â The next feature is common sense: Passive homes are sited to make the most of solar power. In this house, Utting designed an awning above the south-facing windows on the top floor. â€œThe windows are shaded in the summer when the sun is high to prevent the house from getting overheated,â€ he says. â€œIn the winter, the sun is lower, so it enters the house under the awning and heats it.â€
A cooling andÂ heatingÂ system.Â All of the above can reduce by about 90 percent the energy needed to heat the space. What makes up that last 10 percent? Believe it or not, you do. Body heat, plus the heat given off by appliances, TVs, andÂ even lightbulbs, isÂ all captured by intake vents. These vents are positioned in the warmest roomsâ€”the laundry room, kitchen, and bathroomsâ€”to capture tiny amounts of heat emitted into the air and send themÂ to a Heat Recovery Ventilator. This device uses a heat exchanger to heat or cool incoming fresh air, depending on the season, before pushing it out into the living spaces.