What Is Passive Solar Cooling And How Does It Work?

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Green is a hot topic these days, but you don’t have to spend tens of thousands of dollars on solar panels. As the summer months approach, and energy costs creep increasingly higher, a passive solar implementation could be a great middle ground.

Passive Solar is using sunlight for energy without any active mechanical systems. A solarium or sun room on the equator side of a home would be a common example of passive solar use.

Passive cooling is a subset of passive solar use and as you might guess involves cooling a building through natural means. The primary focus of passive cooling is:

1. Slow heat transfer into the house.

2. Remove unwanted heat from the building.

You should avoid any large glass areas directly in/around living space. Large glass areas would allow unwanted heat transfer into these living areas.

The window and door openings can play a large role in overall heat transfer rate and therefore in your cooling requirements. A solid wood door with no windows conducts heat about twelve times faster than a foam-filled Energy Star door. Poor quality doors and windows can allow outside air infiltration, and radiate heat transfer through the exterior envelope of a house. This can lead to higher cooling costs.

West facing rooms are prone to overheating because low afternoon sun can penetrate deeply into these rooms during the hottest part of the day. Some methods of shading low west and east sun are:

1. Vertical Shutters or Blinds

2. Deciduous Planting

3.West facing windows should be minimized or eliminated entirely

Insulation also is a key component of heat transfer. A sign of poor thermal design is an attic that gets hotter during the day than the high outside air temperature. This can be reduced by properly insulating the area and by using a cool or green roof. This alone can reduce the roof surface temperature by 70 Degress F. You should have a radiant barrier and an air gap below the roof.

In mild climates with cool dry nights, two types of natural ventilation can be achieved through careful design: cross and passive-stack ventilation.

Cross Ventilation utilizes openings on two opposing sides of a room.

Passive-stack ventilation utilizes a vertical space to create a vacuum as it rises by natural convection. An inlet for cool air at the bottom creates an upward-moving current.

Fresh air ventilation should be filtered through a MERV 8+ air filter. Avoid the use of window screens for direct unfiltered ventilation as dust mites and other unwanted organic material may be brought in.

In hot humid climates with uncomfortable nights, fresh air ventilation should be controlled, filtered, dehumidified, and cooled. (Possibly via the use of a zero energy heat pipe air exchanger.) A solar air conditioner can be used to cool and dehumidify hot humid air. ASHRAE requires a minimum 0.35 air changes / hour and 15 CFM of fresh air for each person in a room year round, regardless of conditions. Carbon dioxide monitors can help to increase fresh air intake in high-occupancy rooms.

In a climate that is warm during the day and cool at night, thermal mass can be placed and insulated to slow heating during the hottest parts of the day. Specially designed phase change can be used to extract heat during the day, and release it at night.

Find great house plans online by Nelson Design Group.

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Source by Craig Mccoy