A Concrete Modern Passive Solar Home

Why Concrete and Passive Solar Rock

In contrast, a traditionally stick frame built house that does not have thermal mass or windows facing the south, often relies on a heating system that heats the air within the house, while the house constantly looses heat.

This passive solar home works because the structure has a great amount of thermal mass, it therefore takes a longer amount of time to loose the heat that it has stored within the floor and walls as it radiates throughout the house.

Concrete as a building material has many cost effective advantages while being purposefully efficient.

Concrete is also a finished surface, thus it can have economical advantages and potentially can eliminate steps in the building process.

Because concrete can be sealed and stained, it can eliminate the need to hang drywall within the house.

Similarly, because it can be finished and sealed, there is no need to stucco or hang siding on the outside of the house, though if the owner desires it, it can be done.

This project, which measures approximately 1,100 sq. feet, approximately $20,000 dollars were saved due to the elimination of these steps. About $350 dollars were spent on the stain, which simultaneously seals the wall.

The concrete walls are 10 feet tall, with a structure insulated panel system (SIPS) roof system laid on top. The roof has 3.5 inches of pitch from the north to south, within a span of 16 feet.

 

 

The SIPS Roof

The SIPS used are foam core panels, constructed out of polysterene (similar to the white insulation used in styrofoam cups) which is surrounded by Oriented Strand Board (OSB) a wood laminate material on both sides.

SIPS have numerous advantages when building. They are structurally very strong while they are also lightweight.

SIPS provide very good insulation, and depending on its thickness, can have an R-value up to R-50. Because they are pre-assembled, there is a minimal amount of work in installation.

The SIPS that were used in this project were created and transported to the build site as 9 pieces that made the installation of the roof as simple as lifting the pieces onto the structure and nailing them together.

Because the SIPS are are a flat surface and act as the roof, unlike traditional attic spaces, extra air space does not exist and there is no need to add any extra insulation, as the roof itself is the insulation. Ceiling drywall is also not needed and another step is saved and another potential cost is eliminated.

Covering the roof on the top outer surface is a piece of large EPDM (ethylene propylene diene Monomer) membrane. It comes with a 20 year guarantee and is the same waterproof roofing material used on large commercial projects. Potentially a rooftop garden can be utilized to help keep the house cool in the summer.
 

The Interior of the Building

The interior utilizes recycled materials and green finishes.

The building utilizes color to emphasize warmth and lighting within the rooms.  For example, while most of the dwelling’s windows are to the south, the northern most room, the one that gets the least amount of light, feels sunny and warm.  It can be seen a picture shown previously in the article, showing the pitch in the roof.

The trim used throughout the house is former barn wood, while the doors and other materials were purchased from a local construction recycling company.

In order to create a sense of unity within the home’s design, the locks, doorhandles and knobs are all similar and were purchased directly from the manufacturer.  Since continuity in theme is important, the similar accessories were the most expensive aspect of the home.  It has created a sense of unity and a modern feel to the home.

Efficient design elements are found throughout the home.

Pocket doors, also known as sliding doors, are used in the house because they don’t take up any extra space as a swinging door does.

The laundry room is hidden behind a pocket door.  The sliding doors can quickly hide the stacking washer and dryer and a domestic chore from unannounced visitors.

There are strong fans installed in the bathrooms.  They are efficient, quiet, and an integral part of the summer cooling system. In the evening, when the windows are opened to the cooler night air, they draw heat from throughout the house and send it outside, while cooler air is drawn in.

 

Radiant Heat – Hot Water System

While the home has been designed as a passive solar home, the heating and cooling systems have been integrated with active solar elements.

The home has in-floor radiant heat pipes throughout the concrete floors.

In the utility room, a large 9.5 foot water heater (picture shown in the gallery above) is actually comprised of two internal tanks with two different glycol systems: one for hot domestic water use, and one for heating the house.

A water glycol blend from the tank is sent through solar thermal panels on the roof. They collect heat from the sun throughout the day as the glycol system circulates through the large storage tank, transfering its heat to the water through a water coil.  The glycol in the tubes never mixes with the water.  Both the glycol and the water are in separate closed loop systems.

In case there are a few cloudy days, there is also a flash water heater that is used for backup.

With its thick, tall, dense wall, the home feels safe and secure.  The use of concrete on the outside and inside of the home works within the four season, yet mild and sunny climate of Colorado.

 

Designer / Builder – Sven Krebs

Time to Build – 2.5 years

Square Footage – 1100 feet

Cost – 100 per square foot on materials, doing own work