A passive solar house stays home and ‘works’ for you! Here’s how:
During a sunny winter day, the low angle of sunlight is allowed to shine through the glass of all windows on the south wall. The radiant energy emitted inside is captured, absorbed and heats the surround air.
This ‘free’ energy from the sun, is passive gain, requiring no mechanical assistance , and can contribute noticeably to the overall heating of your home. Each sunny day during heating season you will find your home warm and comfortable, at no direct cost to you, simply because you decided to live in a solar home.
During a hot sunny summer day, the high angle of sunlight is prevented from entering the south facing glass, due to proper shading-thus allowing for no heat gain, helping to keep the interior cool.
Passive Solar Mechanics
1. South Wall
Glass windows and doors face south and are arranged by glass area to adjoining space(s) providing proper glass to floor area ratio. The objective being for natural light, viewing needs, and ventilation to balance out heat gain / loss, esthetics, and fenestration costs. Typically triple pane glass assemblies are used for their energy efficiency, but only with a high solar heat gain coefficient (shgc), which allows a high percentage of sunlight to pass through the glass assembly.
Shading is required in order to prevent the hot summer sunlight from hitting and passing through South-facing glass. Integrated shading is provided on the outside of the building, typically by roof eave overhang, electric visor, or seasonal awnings.
3. Thermal Mass
Any material inside a passive solar home will and does absorb the heat gained from direct and indirect sunlight. The general concept behind thermal mass used inside a solar building, particularly direct passive gain, is to create a means to absorb and store the sun’s free heat energy within a building’s insulated envelope. Typically thermal mass is divided into two camps: low mass and high mass. In our opinion, a low thermal mass design is all that is required in conjunction with a very well-insulated building envelope. This diagram shows a insulated slab on grade foundation which does act as a thermal mass, but is by no means a requirement for a passive solar home. Depending on the circumstances a insulated slab on grade foundation can be cost effective.
4. Window Quilts
Window quilts are insulated (R-4) fabric window shades mounted inside above a given window unit. Depending on a homeowner’s budget and energy saving desires, a closed window quilt can contribute noticeably to heat loss at night, adding another layer of efficiency. During the winter, window quilts can also be pulled down on North, West, and East windows during sunny days to prevent further heat loss. Window quilts can also provide extreme privacy at any time of year.
Solar electric – the photovoltaic panel, a modern miracle, can convert sunlight into electricity. A collection of panels together creates a solar array. Depending on the size of the array, enough electrical energy can be produced to operate all your household needs and possibly more, like charging your electric car, lawn mower, power tools etc.. Often panels are mounted on the roof (high point) of the building they will supply, but other solutions can be utilized depending on circumstances, including ground fixed mount and movable tracker arrays.
There are 3 solar electric systems options- the most common is interfaced or grid-tied where your home is connected to the local power grid. During the day electricity being produced by your solar array will feed your home first, but anytime excess electricity will ‘interface’ or feed into the grid. If your array produces more electricity then your home consumes over the course of a year, you have created a net-zero home.
The 2nd option is off-grid where your home is not connected to the local grid and your solar array is operating independently, supplying all of your electrical needs. This choice requires the use of a battery bank in order to store electricity for 24-hour use.
A 3rd option is a grid-tied hybrid, where your home is connected to local grid, but you also want a ‘backup’ if you have power outage using a small compact battery system instead of the larger and more expensive ‘off-grid’ battery bank.
Solar hot water, or solar thermal is an active system designed to absorb the radiant energy from the sun to heat the ‘hot’ water we use at home. Typically residential systems come in two forms. The more common flat-plate collector or the evacuated tube collector. Both units are usually roof-mounted and consist of a closed-loop exchange to a super-insulated hot water storage tank. When the sunlight hits the panel, a sensor engages a small pump to circulate the transfer fluid within the closed loop to the heat exchanger inside the storage tank, thus beginning the process of heating the surrounding water to a desired temperature.
Solar House Orientation
House Orientation – South wall should face due south if possible for optimum exposure and shading control.
Winter Exposure – South wall should receive a minimum of 5-6 hours of sun direct sun per sunny day during the heating season (November through March).
Solar Site Analysis – A site visit will be made to assess seasonal solar exposure.