Design Science

Design as a science? That is a difficult proposition for any artist, designer or architect yet there are elements of a dwelling's design that science can certainly be applied to. Science studies the laws of nature and few forces in nature are as powerful as the Sun. In a dwelling's design, the same holds true.

Passive solar design is an ancient practice that we are rediscovering as the end of cheap energy draws near. It is a travesty that most new and rebuilt structures continue to ignore the most powerful source of energy on the planet.

Let's first take a quick look at the three forms of solar energy being used in our buildings today. List is in order of affordability.

1. Passive Solar Design. The most affordable is also the most simple. By stretching a buildings shape from East to West and putting an appropriate amount of windows on the South, the sun shines into the windows during the Winter, but is shaded out during the Summer.

2. Solar Hot Water SHW (solar thermal). Most solar panels you see are for heating water. They are very affordable and can provide 60-90% of the heat needed for the second biggest energy user in most homes, the water heater. In Israel and Hawaii, all new construction is required to include it. We should too.

3. Photovoltaics (PV). When you see a massive bank of solar panels, they are probably PV panels which create electricity from light. These are the least affordable and most complicated. Panel prices are steadily falling. The level of complication and cost are reduced significantly with "Grid tied" systems. PV panels are necessary for homes that want to produce as much energy as they consume. These systems can be made much more affordable with a high performance building envelope.

The main difference between Passive Solar Design and Solar Water/PV panels is that Passive Solar Design requires no mechanical systems to operate.

Passive solar design is one of the most promising appropriate technologies to be included in any building design or redesign. The sun will provide free, clean heating (even through power outages), healthy-natural lighting, and a better connection to our outdoor environment. Its tough to beat its affordability. Depending on structural engineering and thermal mass, the only extra costs are windows and trim.

Passive solar designs behave very differently from home to home throughout the season as there are many variables that contribute to performance. Unfortunately, most green builders, designers and architects are not well educated in proper, passive solar design. The result is homes and buildings that are mostly under or overheated.

A passive solar home that is not air-tight and continuously-insulated will lose its heat soon after the sun goes down so the most important thing for a good design is a great building envelope.

Top 4 passive solar design criteria:

1. Type and amount of South facing glass per square foot of floor area. 7% or less is considered "Sun Tempered" while a strong design has 9% - 12%. Glass should be High solar heat gain, Low E.

2. Shape & Orientation. Stretched longer from East to West with minimal interference on the Southern elevation which should be facing within 15 degrees of True South.

3. Overhang design. Southern glass on all stories should be fully shaded on June 21 and have full sunlight on December 21.

4. Thermal Mass. Un-carpeted, concrete slabs on grade are usually the most affordable and effective way of achieving good mass. Other options include interior masonry walls, double layers of drywall, lightweight concrete on upper levels, tile, and thicker stone or concrete countertops.

If one can get the right combination of these within a great envelope, its possible to reduce heating costs 90% and have a dwelling that would never drop below 50 degrees during a winter power outage.

Finding the right passive solar home plan.

Architect or Stock Plans?

When designing or redesigning, it is tough to beat the assistance of an architect. The right services from the right architect can be invaluable. If you know how to use an architect's services, they can save you more than they will cost you.

Many people are willing to sacrifice some service to save money. This can make more sense with small, affordable homes on simple lots. Finding a stock plan or existing plan is the next option. Often a good compromise is to have an architect or design professional alter an existing plan to suit one's needs.

For those enlightened individuals seeking a passive solar design, architects and stock plan choices are limited. Things are changing rapidly, but most architects are not well educated in good, passive solar design. It is very difficult to find existing passive solar plans that are well designed and aesthetically pleasing. It is tough to take existing plans and modify them to be passive solar, although it is possible.

The best selection of passive solar plans is on a website started by architect Debra Rucker Coleman.

www.sunplans.com

If you are in the market for existing passive solar plans, this is a great place to find them. Like many internet plans, these were originally custom designed for a particular client and then put up for sale to everyone. From our experience with the Midnite Sun, the plans are richly detailed and customer service is excellent.

The Springtime Cottage 3br 2ba 1410sqft.

Small, Affordable Passive Solar

One of the most efficient and functional 3 Bedroom 2 Bath plans ever created.

We are selling plans for a very affordable 50 cents a sqft.

Small and affordable passive solar plans are hard to find.

This is what inspired us to create the Springtime Cottage. This plan is a masterpiece in small and affordable, passive solar design.

The biggest challenge facing existing passive solar designs is they are usually site specific. They must be oriented to the South and there are four, main directions to approach the entrance from. One of Springtime Cottage's greatest strengths is its ability to be easily adapted to entrances from other directions.

This plan may be one of the most efficient 3 bedroom 2 bath designs created for the modern American family. The main reason is its shape and design. Surface area is minimized by a small footprint with only four corners. There are two stories, but the second level wall area is a fraction of most two story homes. With the giant windows and vaulted ceilings upstairs, the bedrooms feel much bigger.

The simple shape combined with our connection details and panelized construction, makes a structure that is simple to build airtight and thermal-bridge-free. This plan should get fantastic blower door test results and HERs ratings which are the most revealing numbers behind a home's energy performance.

The first Springtime Cottage has broken the record for Blower Door Tests in our region!

Take away the passive solar aspect of this design and you still have a great plan.

The master is on the main level with a generous walk in closet.
The entire first floor is universally designed for handicap accessibility.
The hardworking kitchen has a pantry and bar countertop.
The Mudroom/Entry has enough room for a computer station or small office and the built-in bench is far more useful than a coat closet.

Not So Big and Feng Shui principles are strong and almost every room entrance has a sight line to the outside. Most small plans can't compete functionally, let alone keep things handicap accessible.

The Original Springtime Cottage 1433sqft

Main 816sqft Upper: 617sqft

Springtime Cottage 38: 1600 sqft

Main: 912 sqft Upper:706sqft

An extra 4' to the length with an added powder room could also be reconfigured to create a mudroom/laundry room.

Shrinkable, Expandable, and easy to fit one's site and needs. Re-design is simple and affordable. Wrap-around porches, decks, basements or any other modification can be done by us or the design profesional of your choice.

Its the highly, passive solar design that makes this home a true performer. With a great envelope (preferably SIPS) this home will practically heat itself. The large South windows limit the window, trim, and maintenance costs, but more importantly they reduce air infiltration. The lack of dividers and spaces between windows lets in more light, reduces thermal bridging, and is less obtrusive to the views outside.

Overhangs are often one of the bigger challenges in passive solar design. For this home, they couldnt be easier or more affordable, especially when using SIPS. The overhangs are simply extensions of the roof and do not require additional framing and labor (or opportunities to under or oversize them). The overhangs are sized for Asheville NC which has a latitude of 35 degrees. The overhangs still work great for latitudes South of 35 and North to 41.

There are a number of hidden efficiencies within this home plan. All the plumbing is close together. This saves water and the energy needed to heat the water. It has been designed with two possibile locations for solar water storage. The location upstairs is intended for a thermosiphoning solar hot water system. Thermosiphoning requires the storage tank to be above the solar collector, but in return it eliminates all pumps, moving parts, controllers, and electricity for the solar hot water system.

Another great detail for both energy efficiency and aesthetics is our ability to eliminate the "floor band" and move the main level South windows to the top of the ceiling. This eliminates air infiltration and the interruption of insulation at typical floor framing. Having the windows at the top of the ceiling provides a dramatically open effect, letting light further into the home and saving money on windows by getting them far enough off the ground to not require tempered glass. Our section drawings show this detail and the overhang sizing.

South walls of passive solar designs have so much glass that they sometimes require extra engineering and strength to compensate for the lack of solid wall area. We have designed with this in mind, matching the windowless part of the Southern elevations with the interior floor plan. This eliminates the extra expenses of engineering, materials, labor and energy costs of needing structrual members where your insulation should be.

The most important energy independent feature of this home is that the walls and roof are intended to be built with SIPS, ICFs or Pre-cast concrete panels. We have yet to find better products that can easily and affordably create a great building envelope.

As pictured, the Springtime Cottage works best for East and West entry situations. The plan is shown with a West main entrance, but can be easily mirror reversed for an East entrance. It is also well suited to a North entrance with no additional changes, but would be nicer with a covered porch or possibly another dormer on the North roof. A South entrance would need more, but not unmanageable changes, by adding a small covered porch over a door and possibly moving the stairs.

No other plan combines strong passive solar design with such an affordable and flexible nature.

NC Healthybuilt Homes Program or Greater Asheville