Passive Solar Ventilation Air Pre-heater Circulate solar heated air and outwardly-conducted heat back inside to create a higher effective R-value  In cold climates, well-insulated, tight exterior envelopes are used to achieve energy efficiency. In such cases, bringing in make-up air to meet ventilation requirements can be problematic, as it should be preheated to avoid uncomfortable drafts or excessive heat loss. The passive solar ventilation air pre-heater has exterior corrugated steel cladding perforated with tiny holes that allow fresh air to penetrate. An air space (between the cladding and the exterior wall finish) under negative pressure draws air in through the holes, and is collected in a canopy plenum (which has a by-pass damper for summer). A fan and distribution ducting direct the air through the house.
The system effectively creates a thicker wall that circulates not only solar heated air but also outwardly-conducted heat back inside, creating a higher effective R-value (the manufacturer claims R-55). The fan helps to destratify warm air at the ceiling. Shading the south wall with the cladding reduces cooling load. Indoor air quality and occupant comfort are improved. Ventilation actually increases on colder days. The manufacturer also makes a similar wall system with integrated photovoltaics. 
 | By reducing the cooling and heating loads on the home, less energy is used to effectively keep the home at a comfortable temperature. |  | In addition to helping save on energy consumption, indoor air wuality is improved through the ventilation and fresh air supply. |
There is a six- to eight-week delivery time. The manufacturer is looking for representatives and dealers across the US. In order to be more efficient, the system requires a large unglazed south-facing wall area, a cool climate, and/or a relatively high ventilation load. Additional mechanical heating may be required for the make-up air on cloudy or very cold or windy days.
Typically the cost is $10 to $15 per sq. ft. of wall area, including labor and materials.
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The layer adds to the exterior size of a building and may encroach on required yards and setbacks.
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The system can be retrofitted onto existing south-facing walls (provided there is little or no glazing), but is more economical in new construction. An opening at the top of the wall, as well as an electrical connection, are required for the damper/fan assembly.
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The steel cladding is durable and can protect the original siding. The manufacturer claims that for new construction, investment is paid back in two to four years in energy savings, depending on fuel type and cost. For retrofits, a six- to seven-year pay-back is claimed. In order to be more efficient, the system requires a large unglazed south-facing wall area, a cool climate, and/or a relatively high ventilation load. Additional mechanical heating may be required for the make-up air on cloudy or very cold or windy days. | 
