PERS vs HERS
“But we live in a climate where the temperature drops at least 30 degrees every summer night and this home is designed with mass and well placed operable windows for cross-ventilation! Doesn’t that count for anything?” I whine.
“The use of operable windows is a strategy dependant on occupant behavior. It is subjective and therefore can’t be rated. HERS will however credit a mechanical ventilation system set on a timer so that it automatically brings in cool night air.” My HERS rater replies patiently.
HERS stands for Home Energy Rating System. In order to qualify for a New Mexico Sustainable Building Tax Credit a home must have a HERS index of 60 or less.
While I applaud a system for evaluating the energy performance of new homes, I object to the exclusivity of what gets rewarded. This scoring is geared to conventionally built, technologically “smart” homes. To use my opening example, a home with efficient mechanical air conditioning (cooling) scores the coveted HERS points, while no points are awarded to a climatically responsive home that can be comfortably cooled if the occupant opens the windows at night. In other words efficient technology is rewarded while empowering the occupant to control comfort for the life of the building through passive means is not valued because it requires human interaction.
If you have followed my column you will know that we work with a design philosophy called “Building Biology” which views our homes as a third skin…an organism that interacts with its occupants and the surrounding environment. Building Biology strives to build in climatic resilience through passive and interactive strategies such as thermal storage capacity, natural air flow control, shading devices, glazing and building orientation. The goal here is to reduce the necessity for mechanical intervention because mechanical equipment is high in embodied energy in manufacture and transport, uses energy to run, is often noisy, has frequent health implications and has a very brief track record.
How would things be different if we rated and rewarded human performance rather than computer modeled building performance? What if we had a PERS rating system or Personal Energy Rating System and scored personal consumption of non renewable resources? If utility and fuel bills are less than 50% of the average that person would qualify for a tax break. If they were in the lowest 25% they would get a tax break, medal and a media interview to tell others how they do it.
It wouldn’t matter how one got there and it could include any strategy…wearing long johns in the winter, acclimatizing, living in smaller space, planting deciduous trees or wind screens, doubling home insulation, using a solar oven, not using a clothes dryer, adding mass to the interior of the home, buying or building a well designed home, turning off lights and adding solar technology and high efficiency appliances. In this way we would be freed from the prejudices that narrowly define and reward only that which can be certified in laboratories on behalf of those interests who can afford to pay for testing and certifications. We would reward wise occupants, not smart buildings.
Designers and builders who created energy efficient and healthy homes that empowered owners to live sustainably, would be well rewarded through demand for their product.
The human being would no longer be viewed as an annoying unpredictability factor in computer generated energy efficiency models based on mechanical technologies and conventional construction methods. We would reward LEADers. What a thought!
Paula Baker-Laporte FAIA is an architect and a certified building biology practitioner. She is the principle of Baker-Laporte and Associates and EcoNest Design. She is primary author of “Prescriptions for a Healthy House” and co-author with husband Robert Laporte of “Econest-Creating Sustainable Sanctuaries of Clay, Straw and Timber.” Paula can be reached at firstname.lastname@example.org