questions and answers

general system information

Can this system be used in Fairbanks, Alaska where such systems as Trombe walls soak up more heat than they return?

Yes, the concepts involved in Ekose'a Homes are applicable in any climate. Again, quantities of mass, orientation of the structure, types of glazing, types of insulation, and other related factors are all referenced to climate considerations.

This system should not be compared to a Trombe wall in any sense. The Trombe wall soaks up all the solar radiation available on the south surface, and in the process heats up to a very high temperature, thus radiating a significant amount of heat back out through the glass. Most importantly, the Trombe wall does almost nothing to minimize the heat loss from the structure itself, and it is this process that is the heart of the Ekose'a Homes system.

How does this design work in rainy / foggy climates?

The considerations in special climates such as in rainy / foggy areas are different from those in a high elevation / high solar intensity climate such as Lake Tahoe, California. These differences in solar insolation and outside temperatures and direction of solar heat energy from the sky all have to be taken into account.

The Tahoe houses would not be suitable for Seattle, although if built in Seattle, such a house would reduce the heating requirements by 80% to 85%. However, a different design utilizing these same principles could be made to function at 100% efficiency in the Seattle climate, or in any other climate. Please note that the design does not depend so much on the sun or the earth as much as on the type of measures taken to conserve energy in the inner portions of the structure.

How is the temperature regulated?

The temperature of the air is regulated by the gravity convection of air, which insures a constant and thorough circulation of all air in the envelope space. The mass of the house that is part of the envelope space and the earth mass below the house serve as a heat absorbing, radiating element to regulate the temperature in the envelope spaces. The air circulation pattern is regulated by demand, whereby the more extreme the climate forces are, the faster the air will move in the system.

Why is there not a serious heat loss to the outer surfaces of the air passages?

Because the outer surfaces of the envelope are well insulated or double-glazed and the air temperature in the passage is significantly lower than the temperature in the house, resulting in less heat transfer and loss.

Would building into a slope help?

Building into a slope is not required thermally to enable the house to function properly, but building into a slope can provide additional thermal mass that can be used to justify additional glass on other elevations where it is desired.

Is there a relationship that must be kept between the size of the greenhouse and the air passages?

The relationships must be measured and understood so that the thermal performance of the structure can be maintained; but knowing this, the air spaces can be enlarged at will. Technically speaking, the greenhouse is not required for the thermal system to work. All that is needed is a double envelope, which is carefully designed with shadow casting and percentage of solar contact carefully studied.

The air spaces can be enlarged to accommodate storage and other uses which do not demand the temperature heating requirements of interior living spaces. Spaces such as storage areas, workshops, photographic laboratories, and other specialized uses that would not require the normal house heating could be designed into the structure.

What calculations and formulas are used to design the system?

The system is designed with a thorough understanding of solar theory, thermodynamics, and a practical understanding of air drafts and body comfort levels and their relationship to solar orientation and climate conditions.

Computerized thermal evaluations are performed as needed by building authorities or financial institutions to predict probable interior thermal performance during critical climate sequences. However, there is currently an insufficient database of monitored performance of Ekoseā€™a Homes, which is needed to adapt thermal performance modeling software in order for it to be used as a reliable design tool.

What is the power source for dampers - are they manually or thermostatically opened and shut?

Dampers in most of our designs are simply doors that are manually operated, directly or with a cable and pulley system. They can be controlled by thermostats and mechanically operated. But it is important to note that the system works in such a way that it is not necessary to operate the dampers except once every few weeks at most. They are not used to regulate the system temperature, as the system is self-regulating. Seasonal changes require different damper positions in some cases, and that is the point when they may be operated manually.

Is a basement compatible with this system?

Yes, in all cases. In fact, in more extreme climates a basement is necessary to increase the thermal mass that will be acting on the total system. The basement thus acts to dampen any extreme temperature fluctuations in the system.

Do you advise against north windows?

No. North windows do not contribute to the heat loss any more than south windows. South windows, on the other hand, do contribute to the heat gain. As long as there is a balance achieved whereby the heat gain is sufficient to compensate (for any heat losses, there is no limit on the number of north windows.)

Is the garage heated, or a part of the heating / cooling or insulation design?

The garage can act as a buffer zone on the east and west elevations. It is normally not heated, but it could be included in the design so as to be heated.

Are your techniques amenable to an office building using essentially residential construction techniques?


heat storage - backup heating

Have you considered using loose gravel beneath the house?

Yes, we've considered using almost everything. However, the dirt that is found on any site is equal or superior to any other material that could be used, including rocks. The heat transfer characteristics of a rock bed are not suitable for this design, although they would work. Rocks tend to give up their heat too quickly.

Is the crawl space insulated?

Yes, the perimeter of the crawl space should be insulated to the outside of the foundation walls to a level below grade, thus insuring that the mass underneath the building is protected from the immediate effect of ground temperatures outside of the building. The thermal mass below the crawl space, below the earth bed in the crawl space, should not be insulated.

Shouldn't the storage mass have direct sunlight?

No. Letting the sunshine directly on the storage mass would not be consistent with the design concepts and assumptions. The design assumes that the sunlight entering the structure converts quickly to hot air as opposed to stored heat, and that the hot air will flow through the envelope space and become stored evenly throughout the entire structure.

Direct sunlight would heat up the storage mass to a fairly high temperature and re-radiate that heat to that space too quickly, since its own temperature would be considerably higher than the temperature in the air space. If this same amount of heat energy were used to heat the mass of the entire structure, the structure mass would only heat up a fraction of the amount that a concentrated mass placed in direct sunlight would.

Since the temperature difference between the storage mass and the air in the envelope space determines the amount of heat that is transferred back and forth, it is desirable to make small changes in temperature in large amounts of mass near the operating temperatures of the system. This is favorable to making large changes in the temperature of the storage mass, which vary considerably from the operating temperature of the system, thus making the system less stable.

How would a fireplace / wood burning stove interfere or integrate with this system?

There is no problem integrating one or the other into an Ekose'a Home. It should be in the interior portion of the house, and therefore will not directly contact or interfere with the air in the envelope or affect the gravity convection loop performance.

You do have to supply air from the outside envelope to the inner space for combustion air, and you also have to supply some outside air to the envelope space to make up for the combustion air. The reason for this is that the house is so tight that there would be no air to fuel the combustion and carry the exhaust gasses off up the chimney unless a way to introduce outside air was provided. This outside air should be ducted to the point of the fire so that cold drafts are not blown across the room in order to supply air to the fireplace or stove. That being said, wood burning is highly toxic and polluting; and therefore fireplaces and wood stoves are generally discouraged except in remote rural areas.

cooling cycle

How is the house kept cool in the summer?

Basically, the interior living spaces are kept cool in the summer by being an inner house that does not receive direct sunlight, except through east and west elevations. The south wall, roof and north wall of the house are all isolated from direct solar insolation in the summer. This reduces the cooling task tremendously.

In addition, the diurnal temperatures exposed to the total mass of the system bring the temperatures of the system near the diurnal average.

In hot climates, outside air is introduced into the crawl space and cooled by the earth mass, which then ventilates the build up of hot air from the attic by the gravity-chimney effect. Cooling tubes buried in the ground are also used to pre-condition the air before entering the crawl space. The Chimney effect for exhausting hot air in the envelope can also be utilized and controlled to affect cross ventilation of the earth-cooled air through the living spaces through opposing openings to the air envelope; inducing air movement and evaporative cooling of the body.

Are overhangs necessary to shade from the summer sun?

Absolutely. Sun control and heat control are necessary to maintain comfort levels in the interior spaces during summer.

greenhouse consderations

Can the upper greenhouse area be used for living space in some way?

Yes, as deck space off any room or rooms on the second level or higher if there are more levels.

Would a concrete slab floor in the greenhouse help?


What about stale air and household odors?

In the interior living spaces, odors are easily discharged through a window opening or sliding door to the envelope or greenhouse. This is more desirable than in a conventional house since the air in the greenhouse is not the freezing cold air or extremely hot air of the outside climate. This means that you can, and will ventilate more often.

The envelope space is large enough and absorbent enough and has sufficient infiltration so that odors transferred to the envelope space are dissipated and reduced naturally.

In addition to this, the presence of plants in the greenhouse / solarium area tremendously increases the capacity of the envelope area to re-oxygenate, filter and re-fragrance the air to its natural outdoor level.

glass - windows

I am worried about the south glass wall and windstorms, need I be?

Windstorm considerations are no different for this design than for any other type of house. The support spacing / size of glass panels can be reduced, and the type of windows can be modified to meet wind load design standards. Otherwise, the important considerations are total window area as a ratio of mass and total heat loss.

What about insulated coverings for windows?

We can usually avoid having the owner manually operate insulated coverings for windows in order to maintain thermal comfort. In a situation where there was no other way to reduce the heat transfer to the outside at night, such as in an existing building or in an extremely cold climate with no possibility for basement mass, it would be possible to compensate for the heat loss through insulated coverings for window areas.

Is it necessary for interior glass to be thermo-pane?

Not in all climates. In milder climates single glazing is adequate. In more severe climates, it is necessary to use double and sometimes even triple glazing for both heating and cooling thermal performance.

How is the sloping roof glass of the greenhouse sealed from leakage?

The standard detail for sealing glass to sloping roof surfaces is to first attach a sheet metal cover to the wood structure and then seal the glass in place using a silicon caulking compound such as GE silicon sealant.

With all the glass on the south side, isn't some privacy lost?

All the glass is not required if that is the preference of the owner. A completely conventional plan could be designed to function in the same way. There are also methods of creating some privacy, such as curtains on the interior windows.

moisture - condensation

What are the problems of moisture and condensation in the air spaces and passages?

Condensation occurs less in Ekose'a Homes than in conventional houses. Condensation occurs chiefly where there are extreme differences in temperatures. The thermal envelope space enables an intermediate temperature to be established between the interior living environment and the outside climate, thus reducing the dangers of moisture and condensation.

By stabilizing the moisture content of the structural building materials, the envelope system actually prolongs the life of the system. The double wall approach allows for the free circulation of air in and around all structural members and thereby minimizes the potential for rot, mildew, mold, decay or any other type of degenerative process for wood.

Is condensation on south-facing glass a problem?

Condensation will occur on the south glass and occasionally on the north glass of the outer envelope in extremely cold weather early in the morning, but normally evaporates during the day. However, particular attention should be given to the detailing and construction of sills at glass openings. Condensation will never occur on the inner glass wall of the living space itself.

How do you keep the crawl space dry?

The moisture content of the air in the crawl space is maintained at around 45% to 55% during a twenty-four hour period due to constant air circulation, which is maintained year-round. The interior environment is essentially prevented from receiving direct outside moisture from the air, and from any precipitation that falls on the building, so that the moisture content in the crawl space remains at this optimal level.

In hot humid climates, where outside air is drawn through the cooling tubes into the crawl space, humidity can be substantially higher.

Is water a problem in the foundation?

Less so with this design than with conventional basement designs. This design requires that the space be- low the house be treated as a conditioned space and as such, enables consideration of slope, drainage and constant circulation of air to minimize moisture problems in the foundation. It may also be necessary in extreme climate situations to provide perimeter footing drains and even sump pumps, as would be required in conventional construction given the same circumstances.

Should the soil in the crawl space be treated for termites?

Absolutely not, some other practice such as termite shields at the top of foundation work should be considered. Also periodic visual inspection to spot tunneling and sounding wood sills, floor beams, and joist headers with a hammer are your safest alternatives. Termite activity when detected can then be treated locally as required.

construction - building codes

Can your design accommodate the requirements of being built on pilings and be able to withstand high humidity?


Is post and beam construction feasible for this system?

Yes. This system involves a concept of envelope spaces and openings combined with insulating values and quantities of thermal mass; and as such, it does not dictate any type of structural system or any architectural style.

Are there critical dimensions in the roof and north wall plenums for the free area?

Yes, the minimum cross section restriction here should be about eight inches, and twelve inches is better.

Is a vapor barrier necessary under the crawl space?

This depends upon the moisture conditions of the site, but normally they are not necessary.

What about vents from the outside to the crawl space?

Except where underground cooling tubes are required for summer cooling, no vents are required to the crawl space. Since the crawl space is connected to the air envelope and a relatively large area of exterior building skin, there is sufficient air movement due to gravity convection and outside air infiltration to satisfy any concerns or building code requirements for crawl space ventilation.

What sort of insulation is used?

The type of insulation is not important. What is important is that you understand the limitations, the cost and the effectiveness of the various different insulations in doing their basic job.

We normally recommend conventional fiber batt insulation and rigid polystyrene board in certain applications.