Passive Solar Heating, and Solarium Esthetics.
In geographical locations with a significant Winter heating requirement (most of the continental U.S. except Southern Florida), we use passive solar heating – vertical South-to-Southeast-facing glass for the lowest-cost direct solar gain, ONLY in the winter.
The amount of South-facing solar heating glass is determined by the local solar gain potential, and the degree-day heating requirement in the Winter. It is even needed in the Northern half of tropical Florida, where the Winter temperature sometimes drops below freezing when the frigid Canadian jet stream swings South.
In the past, passive solar designers have often used too much glass and been surprised at the need to exhaust excess heat on very cold clear Winter days. In a warm humid climate like Florida, passive solar techniques have to be used very carefully to avoid excess solar heat gain in the Spring and Fall.
We have observed that Winter solar gain increases due to reflection from the low angle of the sun through vertical South-facing glass, when snow is on the ground. This is a desirable Winter heating characteristic of passive solar design that architects need to understand when sizing solar glass in snowy climates.
Two simple inexpensive 1980’s ZED homes with integrated solariums
The passive solar South-facing glass is often isolated from the interior living quarters of a Zero Energy Home, with an esthetically-creative solarium (greenhouse / sunroom / conservatory), which may contain tropical plants, fresh fruit/vegetables/flowers, a hot tub, swim spa, pool, fish pond, waterfall, or sporting / exercise area for ping pong, racquetball, basketball, gymnasium, exercise equipment, etc. Sunrooms can be very inexpensive, with a dirt floor for planting, or as formal and elegant as you like.
I enjoy natural wood interiors, but the walls can be anything you prefer. The solarium is a great place for sunny meals and starlight entertaining at night. Music and a dance floor are romantic and usable when outside temperatures are too hot or too cold. The fact that that your solar greenhouse helps reduce heating AND cooling energy requirements for the entire home is an incidental side benefit to some prospective homebuyers. (But, it is of primary importance to ZED.)
Many tropical and flowering plants (which grow well in the solar greenhouse) release pure oxygen and pleasant fragrance into the air. Both are healthy and pleasant environmental factors, in harmony with nature viewed through the Southern glass wall.
Many potential homebuyers, who do not have a clue about the energy issues in our lovely brilliant Zero Energy Homes, but they love the great beauty, sunshine, and unique esthetic creativity that only ZED can cost effectively provide at a surprising low cost.
The greenhouse solarium acts as a year round thermal buffer zone between the house interior and the outside temperature - with two small delta T’s (temperature differentials across the inner and outer glass walls), instead of one large delta T (across a single exterior wall). This thermal buffer greatly lowers interior / exterior heat transfer along the longest (South) side of the house.
A movable floor can cover a well-designed solar-heated swimming pool, swim spa or hot tub, to nearly eliminate undesirable humidity and evaporative heat loss, AND add entertainment and usability flexibility to the solarium, providing additional floor space when not using the pool. The movable floor can optionally align with the rest of the sunroom floor, making the pool disappear altogether when not in use.
The passive solar glass South wall is normally the least expensive wall in the house – often using low-cost high-volume 34” x 76” tempered single pane patio door glass (with low lead content in the glass). Our inexpensive off-the-shelf insulated weatherproof glass mounting system minimizes installation labor, materials, and total wall construction time-and-cost.
Optional “window quilts” can greatly reduce single pane sunroom glass heat loss on cold Winter nights, and heat gain on hot Summer days, to minimize solarium heating and cooling energy requirements. The window quilts lay flat against the window frame to reduce convective heat loss. They can include a radiant barrier (similar to that used in the International Space Station exterior and in astronaut space walk suits). The simplest form of window quilts are operated manually with a pull cord.
As an option, automated solar-powered motors can control window insulation throughout your custom ZED home. Inexpensive micro-computer-controlled motor switches can then operate window treatments in an unattended mode, based on programmable states like: available sunlight, storage battery power levels, time of day, internal / external temperature, cloud cover, day of week, etc. This maximizes the benefit of window insulation versus solar gain, without requiring the home to be occupied.
Our first 1979 Zero Energy Home required the owner to do things like opening and closing drapes to maximize its performance. We quickly learned that automating such things simplifies the ZED abundant energy lifestyle, without asking the occupants to even be home, or understand when and why to do simple things.
For example, If want to sleep late on a clear cold Winter Sunday, let your ZED system automatically open your solarium drapes when the sun warms your South window wall, but leave your bedroom drapes closed until you want to wake up. However you would like it to work, ZED can make it happen, and show you how to set it up and change it yourself.
On a Winter weekday, you may have to go to work before the sun comes up. Let your ZED system open your drapes at the appropriate time, when the sun is shining brightly, and close them if there is a heavy overcast in the late afternoon. The intelligent sensor controls will maximize the performance of your passive solar system, and have your home just the right comfort level when you arrive home. You can even “talk to your house” over the Internet or a phone and tell it anything you want to monitor or change. Webcams are also an obvious option to help you monitor what happens in and around your home.
During the Summer, you may want the drapes closed whenever no one is home, and only open to allow cheery sunlight to lift everyone’s spirit during the day. Your automated window treatments can even act as a spectacular alarm clock to help you be alert when it is time to get up and begin another happy day. You can specify individual drapes to open, to minimize early morning direct sun in your face.
The investment in things like automated window treatment controls can be justified by improved overall system thermal performance, simplified energy-abundant lifestyle, and the high-tech esthetics.
NEVER USE ROOF ANGLED GLASS ! ! !
This is a primary no-compromise NEVER-VIOLATE ZED MANDATE. It may look like a good solar energy thing to do (to a person who is clueless about ZED and does not understand the seasonal path of the sun, or how to design an energy-efficient solarium) but,
- Roof-angled glass is a huge heat loser on Winter nights, when warm air rises to touch the low-thermal-resistance highly-conductive glass. Even if it is triple-pane glass, it is like a thermal hole in your ceiling and roof, allowing enormous, expensive heat flow.
- Roof-angled glass is also a huge heat gainer on hot sunny Summer days, when the scorching sun is nearly straight overhead for hours each day.
Why are these things not intuitively obvious to EVERYONE? This is the plain and simple absolute scientific truth, often overlooked by those who should know better.
Roof Angled Glass On A Northern, and A Southern Home
VERY BAD DESIGN SUMMER AND WINTER !
These two stupid houses were costly failed experiments - By others
who blindly thought they were improving on our ZED expertise.
These arrogant non-learning architects thought they were solar
energy heroes, BUT, they turned out to be intellectual zeroes.
They used MORE expensive energy than conventional houses, AND
they were still very uncomfortable on Winter nights and Summer days.
It was very expensive to remove the glass from the roof and then insulate.
In the Summer, huge exhaust fans with fresh air intakes cannot possibly make a sunroom with roof-angled glass cooler than the outside air temperature that they draw in. However, in a ZED solarium with only vertical South facing glass, the peak interior air temperature is LOWER than the peak outside air temperature, by using intelligent design and NO ROOF-ANGLED GLASS EVER! This is an essential part of the ZED thermal buffer zone (TBZ) concept of two small Delta T’s to superinsulate and greatly reduce undesirable heat flow.
