Passive Solar Design

Wildridge Firehouse

Is passive solar still viable in 2019? Well maybe, for the right site and building program passive solar is a low cost and environmentally friendly way to optimize energy conservation. Passive solar noiselessly releases radiant warmth without reliance on battery storage or visually unappealing  photovoltaics panels. Passive cooling is also an option that aligns with passive heating. There are multiple passive solar (and passive cooling) strategies. 

It is all about building orientation and where you locate your windows. Not all sites can maximize passive solar strategies but most can incorporate some aspects. 

When selecting a site (in the northern hemisphere) look for one that has a long southern exposure if possible. A sloping site offers the opportunity to bury a portion of your building and using the stability of sub-grade stable temperatures to minimize your heating bills. 

Passive solar systems are used to “collect, store and distribute thermal energy by natural radiation, conduction and convection through sophisticated design and wise selection of building materials”. Passive solar strategies have been around for millennia in one form or another. 

Solar exposure and building orientation is key to success. Can passive  compete with active solar strategies that store utilize battery storage if designed and managed properly. In todays world the  most common passive solar design uses the greenhouse effect to collect heat. A combination of insulated windows and masonry walls or floor to collect heat and slowly release it through out the day and night. 

Before the term the “Greenhouse Effect” was used to describe an aspect of climate change it referred to the phenomena of the trapping of radiant heat in a structure with glazing. 

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The greenhouse effect is the key principle for this strategy. Radiant heat builds up inside the building and the concrete floors and walls act as a heat sink. It is not a perfect system and lag time between the build of heat and release of it can cause uncomfortable temperatures. This can be countered with ventilation and insulating shades to keep the heat in at night. A super insulated envelope is a key component of a successful Passive Solar in Residential Design.

No one wants to live in a concrete bunker or a glass greenhouse with unlivable swings in temperature just to optimize the collection of radiant heat. Views and access to outdoor space are important to residential living. This home captures natural light and garden views while moderating glare and summer heat gain with  a long overhang. A hallway is located next to the two storey glass wall which is subject to overheating. 

Locating active spaces that are not sensitive to thermal comfort standards next to the glazing is a design strategy. Too much heat build up in liveable spaces such as bedrooms or living rooms is undesirable. Occupants end up releasing heat by opening windows or turning on the cooling and undermining the use. Overhangs are important as well to offset glare and reduce heat build up during the summer. The building pictured here maximizes glazing on the southern wall and stores heat in the slab on grade floor. Ventilation moves the warmed air near the glass to optimize the use of radiant warmth.