jeudi 1 septembre 2016

Project Summary



The goal of the Perlita Project is to show a new path for low energy consumption buildings in Los Angeles and in Southern California through a realistic, affordable and reproducible solutions which will become the standard in the near future with the new rules which will apply, but also because this is the proper way to build.


First, what is a Passive House: a Passive House is a very low energy consumption building achieving precise goals defined by the Passive House Institute (1), a worldwide concept which was developed in the 90’s, optimizing the Passive Solar and superinsulation mix.

Since then, about 30,000 buildings of all kinds (single family houses, multifamily residences, office buildings, schools, shops…) have been certified all around the world and in the US (2). Passive House buildings use up to 90% less energy than regular constructions.

The Passive House standard sets very low energy consumption goals (3), but leave the architect and the building designers free to create the buildings they want within those required goals. However, the following construction principles, which should be part of any construction project, need to be respected to meet the requirements:
  1. -        High insulation on walls, roof and floor
  2. -        Very airtight building envelop
  3. -        Thermal bridge free design
  4. -        Proper ventilation system
  5. -        High-efficiency windows

The Passive House is now recognized as the 21st century reference in terms of building standard for new construction but also for retrofit (EnerPHit concept). More and more cities and administrative districts around the world, including in the US, already stipulated the Passive House standard in their building regulations (4).

The Passive House Planning Package (PHPP) is the energy modeling tool used to design Passive Buildings. The 20+ years of experience and hundreds of measured results have proven the very high accuracy of PHPP results. The PHPP software is one of the most powerful design tools available for designing low energy buildings.


There are many reasons to build a Passive House, first is the level of comfort with no cold drafts, no temperature variation from room to room, barrier to outside noise, very high air quality… As a consequence you have very low energy consumption with almost no heating or cooling bills; it also contributes significantly to reduce the CO2 emissions responsible for global warming, which 40% comes from the buildings’ consumption (5).  Also, the mentioned construction principles will ensure quality and durability of constructions. Last, but not least, based on several economic analyses on impact of energy efficient homes on the sales price of houses, it increases significantly the property values (6).

This trend will increase in the near future for 2 main reasons: The price of energy which will continue to increase and the Net Zero Energy rule will apply.

In California, new residential constructions will have to be Net Zero Energy starting in 2020 (7); it means the residential buildings will have to produce as much energy, thru renewable sources, as they consume.

The main source of renewable energy available in California being solar, houses will need to reduce their energy consumption to the Passive House level to be able to fit the required quantity of solar panels on their roof. Today, almost all single family houses, existing or being built, use way too much energy to be able to fit the solar panels they need to reach that goal.  


The Passive House standard is the most documented and reliable way to design, build and renovate houses to low energy consumption buildings which will be able to reach the Net Zero Energy level.


The Perlita House is located in Atwater Village, a north-east neighborhood of Los Angeles. The area is part of the California Climate Zone 9, the same as Burbank and Pasadena.  The house is 1,000 sqft, one level single family construction from 1906. The project is a one-story addition with the same footprint. 

The design of the Perlita Passive House was done to adapt the Passive House design to the Los Angeles’ climate in order to make the project cost effective and reproducible. The 2 main sources of savings for the Perlita House compared to Passive Houses in cooler climates are double-pane windows instead of triple-pane and a continuous filtered ventilation system without an HRV unit.

The high insulation (8), the airtightness of the building envelop, the shade on the windows, the choice of outside wall colors and all the other Passive House principles will allow a single 1-ton Heat-Pump unit to keep the entire house comfortable (9) all year round.

The hot water, highest energy consumption part, since the cooling and heating needs were reduced drastically, will be provided through a Heat-Pump Water Heater.

LED lighting and Energy Star appliances will keep the electrical consumption as low as possible. The cooking top will be induction, the oven and the clothes dryer will be electric allowing a fossil energy-free house.

10 solar panels installed on the south facing roof will produce more energy than the house will consume in a year, making the house Net Zero Energy. With the Title-24 standard California code design, the energy consumption would have been 80% higher, making the roof way too small to allow the house to be NZE.

Also, since water conservation is a major issue in California, the house will dissociate drains from the black water (toilets and kitchen sink) and the gray water (showers, bathroom sinks and washing machine) to be reused for garden watering. Rain water will also be harvested for the same purpose.

The work will start in October. The construction progress will be available on the project blog (10); after construction the energy monitoring will also be available online.   

The house design was presented in June 2016 at the North American Passive House Conference (11).

XG - Certified Passive House Consultant


(1)      The Passive House Institute: www.passivehouse.com

(2)      Passive House database: www.passivhausprojekte.de/index.php?lang=en

(3)      Passive House goals:

a.       Maximum Heating Demand: 4.75 kBtu/sqft.year

b.       Maximum Cooling Demand: 4.75 kBtu/sqft.year

c.        Final Energy Demand or EUI *: 14.65 kBtu/sqft.year

d.       Building Airtightness - ACH50: 0.6 V/h **

* EUI: Energy Use Intensity, building annual energy use in kBtu per square feet

** ACH50: Air Change per Hour measuring the building air leakage though a blower door test at 50 Pascals   

(4)      Places in the world stipulating the Passive House standard in their building regulations: www.passivehouse-international.org/index.php?page_id=176

(5)      40% of US CO² emissions from buildings, out-consume industrial & transportation sector: www.usgbc.org/articles/green-building-facts

(6)      Energy efficient labelled homes sell for an average of 9% higher: http://energy.gov/eere/better-buildings-neighborhood-program/california-homebuyers-find-more-value-energy-efficient

(7)      The California Energy Commission adopted the goal to achieve zero net energy building standards by 2020 for homes and 2030 for commercial buildings: www.californiaznehomes.com 

(8)      Perlita Passive House R values: Exterior Walls R20, Floor R19, Roof R40

(9)      The AC unit is more than 3 times smaller than the rule of thumb of 1-ton/600sqft too often applied; For the Perlita House the AC unit is 1 ton, which is ½-ton/1000 sqft @77°F (68°F in winter)

(10)   The construction progress will be available at http://PerlitaHouse.blogspot.com

(11)   North American Passive House Network Conference: www.naphnconference.com