PV Panels

The PV panels are located between the house and tower some ten meters from the tower. They are wired to produce 24VDC at 480W peak. The wires run from the PV panels down into the ground and through safety tubing to the house. The wind generator and PV panel wiring was buried together in the same 70 cm deep ditch. The PV panels are grounded. The PV panels are relatively low to the ground and have a small number of trees behind them both of which help to protect against damage from high winds. The panels are mounted on a passive solar tracker, which means it uses no electricity or electrical components to follow the sun. This tracker uses dual long thin black canisters of pressurized gas that are located at the left and right of the PV panels and are interconnected at their bottoms with a thin metal tube. The differential heating of the panels through solar radiation causes one side canister's gas to get hotter than the other and the gas expands in this one. As it expands some of this gas is pushed into the other canister, causing one to get lighter as gas leaves and the other to get heavier as the gas enters. When the panels face directly into the sun, there is even heating of both canisters and therefore both canisters remain at the same weight and remain in balance. This passive tracker has wind shock absorbers to stabilize the panels under high wind conditions. The concrete foundation was made in the same way as the wind generator foundation.

Wind Generator

The wind generator is located about 30 meters to the southwest of the house. The tower is a galvanized steel electrical tower with a large, thick two meter long steel tube welded to the top. The wind generator is bolted to the top interior of this tube. Total tower height is about 14 meters. Electrical wiring runs from the wind generator down into the ground and through safety tubing 70 cm underground to the house. A large hole was dug for the foundation of the tower. The hole was dug excessively large by the machine. I filled old biodegradeable shopping bags that I had stored with dirt and lined the sides of the hole with them to steady the dirt walls and reduce the size of the concrete foundation. I collected many large rocks from the surrounding area which I used for the foundation. As I slowly filled the hole with concrete I threw in these large rocks. I also threw in old concrete and brick construction waste pieces left over from the house construction. For the concrete I used old stored glass jars which I broke into small piece. These I used along with gravel as the aggregate for the concrete. The tower is earthed to a copper ground rod. The wind generator produces 24VDC electricity. High wind speed protection is accomplished through the wind generator's unique, reliable and automatic autofurl design.

Renewable Electrical System Overview

The diagram above is a schematic representation of my renewable energy electrical system. The two main sources of electrical energy production are a wind generator rated at 1000 watts of electrical energy production at a wind speed of 28 mph mounted on a 14 meter freestanding tower and four 120 watt photovoltaic panels mounted on a passive solar tracker. A set of eight large renewable energy lead-acid batteries store excess energy production for use in times of excess consumption. A power center regulates the flow of energy into the batteries and dump load from the wind generator and PV panels. Appropriate safety disconnects are placed between the batteries and the inverter and converter; these are located within a DC source center which is simply a box connecting up the power center, batteries, inverter and converter. A converter transforms the 24VDC electrical energy into 12VDC, and an inverter transforms DC electricity into AC. AC and DC safety distribution panels transfer the electricity to the house wiring. A small gasoline generator provides backup energy in case of extended low wind and solar energy production periods.

Future Sunroom

I have already posted this article once before. I am reposting it because it will be one of the key house heating systems in future and want this information to also be within the context of my description of the home's complete space heating system.

I plan to build a sunroom that will cover the entire south wall surface of the house. This sunroom will have a number of important functions. The primary ones being solar heat capture and added insulaiton. The sunroom will act as a greenhouse that traps solar radiation thereby heating the interior air of the sunroom during sunny days to relatively high temperatures. On such days the doors and windows can be opened to allow this hot air into the home. The hot air flowing into the room will cause negative pressure in the sunroom that will suck in cooler floor-level air from inside the house. This creates a circular thermosiphon effect where hot air goes into the home through the top half of the open doors and cold air from the house goes into the sunroom through the bottom half. Considering the size of the glass space and the relatively limited enclosed volume of the sunroom (which will only be two meters wide), on a sunny day this sunroom can provide the house with a substantial amount of extra solar heat. To ensure maximum solar radiation penetration, the sunroom will be single-paned and will use normal glass. The wood structure will be as thin as possible to block as little solar radiation as possible. And the inclined glass roof will be as steep as practical to ensure the least radiation reflection in winter. The floors will be made of white concrete; this will help absorb excess air temperatures to ensure against overheating while the white color keeps most of the solar radiation heating the air rather than the concrete. This stored heat will then be released during the night, helping to moderate nighttime sunroom temperatures.

The sunroom will act as insulation in several ways. The relatively dead air space created by the air-tight sunroom's enclosed volume provides increased conductive heat resistance to the south wall and windows of the house. I am considering lining the interior of the sunroom's glass with low-e film to reduce radiative heat losses (any comments as to the practicality and wisdom of doing this would be highly appreciated). The thermal mass within the sunroom helps moderate the sunroom's nighttime temperature, thereby helping further reduce conductive heat losses. And the sunroom will act as air-lock entry for my two entrances. This ensures less heat and cool is lost whenever I enter or exit these entrances.

This sunroom will also help cool the interior of the house. The very top of the sunroom will not be made of glass but rather of wood and PV panels. This will create a 'roof overhang' that will block summer solar radiation from entering through the south house windows. Also I plan to incorporate special exterior roll-down shadecloth curtains to help further block solar radiation heating any of the south wall's surface. I am also planning on adding cool tubes to the house for summer cooling. I plan to combine this with a solar chimney, and the sunroom would act as the solar chimney. Placing vent windows at the very top corners of the sunroom and leaving them open in summer would cause hot air to rise up and out of the sunroom. This air would be replaced by air from within the house through open doors and windows on the south wall. The negative pressure created within the house would help to suck air through the cool tubes into the home, thereby providing cool fresh replacement air during the hottest times of the day. Whether I implement this cool tubes-solar chimney combination will depend on the hottest summer interior temperatures reached once the house is completely finished.

The sunroon will also act as an outdoor living room. It will provide a convenient place for solar cooking. It will be an ideal location for storing a large quantity of split firewood (all the way at the east side). It will also be ideal for our house dog (better he shed fur in the sunroom than in the house). We will also use it for some solar drying activitites and possibly for some small gardening tasks like sprouting seeds and growing some herbs. And no doubt as time passes I will find many more uses for it and think of possible modifications to help reduce resource use of one form or other.

The structure of the sunroom will be made of wood and glass with concrete tile and brick floors. As mentioned the concrete tiles and bricks will be white for the reasons already mentioned but also to reflect more radiation onto the south walls (which in future will have mounted solar thermal water heating panels for an active solar space heating system) and into the south wall windows for extra solar radiation and daylighting. The glass will be single-paned with possibly a low-e film. The supporting structure will be made of wood treated with white protective paint. I do not like the use of wood for reasons mentioned in previous posts. It requires a lot of maintenance to last a reasonable amount of time. But I feel it is the only practical choice I have. Since I plan to build the sunroom myself, and I know how to work and design with wood, it is what I am left with. I don't want to make a massive masonry structure that would block a lot of light and have unnecessarily high embodied energy. And I don't want to use metal since it is such a powerful heat conductor; plus the fact that I do not know how to weld at this scale and would require a lot of energy to do so. As for PVC, it would be ideal, but, as mentioned earlier, I am trying to now avoid this product where possible on the recommendations of Greenpeace - not to mention that I would need to learn how to build with it (but this is a minor consideration). So for now I plan to use wood unless some better alternative suggests itself before its construction.

Future Active Solar Space Heating System

In future, sometime after having finished the sunroom, I intend to install an active solar thermal space heating system. This system will be composed of solar thermal water heating panels, specially designed and made radiant baseboard heaters filled with PCM thermal mass, distribution piping, and a direct PV/DC pump setup. This system will be installed to enable me to eliminate my current use during a number of weeks of the winter of my paraffin heaters and its petroleum-distilled paraffin liquid fuel.

I will make special solar thermal water heating panels to cover much of the south wall exterior surface. These panels will basically be coils of copper (or aluminum) piping with aluminum fins, both painted black, which will better absorb and conduct this heat to the antifreeze liquid in the piping. This piping with attached fins will be enclosed in thin insulated box panels. These box panels will probably be made of wood for its exterior with special interior rigid foam board insulation with interior-facing surface radiant foils. The top of the panel will be glass to allow solar radiation to penetrate and strike the piping. The box will be properly sealed to make it fairly air-tight.

The solar thermal panels will transfer their heat to a water-propylene glycol mixture that acts as the heat transfer medium. The propylene glycol is added to the water to drop the water's freezing point and thereby making it very difficult for it to freeze. This heated water is pumped to the heaters in the bedrooms and bathrooms through insulated copper piping. The water will be pumped using a small hot-water DC pump that will be powered directly from a small PV panel. There will be no thermal differencial on-off switch and sensors. When there is enough sun to power the slow-pumping DC pump with the small PV panel, there will be enough sun to heat the solar thermal panels to add energy to the PCM contained within the baseboard heaters. The piping system will have a one-way valve to stop any unwanted reverse flow of heat to the outside at night or during cloudy days.

I will design and make special baseboard radiant heaters filled with PCM thermal mass (unless a similar, affordable product is commercialized before then). These baseboard heaters will just off the floor attached to the walls. They will run the lengths of the walls and be from 10 to 20 cm wide and a few centimeters thick. These baseboard heaters will be metal enclosures filled with special PCM thermal mass in the center of which will run the copper piping with special heat-radiating fins. These fins will transfer the heat of the water in the copper piping to the PCM for storage. The PCM will absorb as much heat as given by the solar panels and then release this heat through conduction to the metal enclosure, which in turn radiates the heat to the room, when room air temperatures begin dropping. In summer, these PCM thermal mass baseboards can work in reverse to absorb heat from the hot interior air during the day and then have the heat pumped to the exterior during the cold night for night-time flushing - to make this work more efficiently, the water should not run to the solar thermal panels but rather be diverted to another set of panels or tubes specially designed for quickly releasing heat to the exterior air or ground or cold body of water.

Backup Paraffin Heaters

The second backup heating system for the bedrooms is small portable paraffin heaters. These heaters use paraffin liquid fuel, also commonly known as kerosene, which is distilled from petroleum. I do not like using these and try to keep my use of them to a minimum. Besides the fact that they use a highly finite, unsustainable, non-local resource, their combustion, while relatively clean due to the paraffin heaters' burning technology, still ends up worsening interior air quality. My hope is that future house improvements, such as the addition of a sunroom, increased insulation levels, the incorporation of an active solar space heating sytem, and other smaller odds and ends, will reduce my need for these paraffin heaters to the point that they become nonessential. If these improvements fail to achieve this, then I will modify the active solar heating system and make it into a hybrid solar-biomass heating system.

For the time being, since I have to use these heaters for five to six weeks throughout the winter, I try to use them as responsibly as I can think of. This means using them efficiently and seldom. In practice this means several things. First, I have two types of paraffin heaters. One is manual and must be turned on by hand when one gets cold. The other is electric and turns itself on based on programmed parameters. The electric one is more efficient since it turns itself on and off at preset temperatures and times. This automatically ensures a certain temperature within a room without someone needing to constantly check the temperatures which would lead to inefficiencies since the heater would not be turned off as often as it should be; furthermore, it's time feature allows the heater to turn itself off after one has fallen asleep in a warm bed, allowing the temperature to drop, and then turn itself back on just before one wakes, to bring the room temperature back up. I use this electrical heater in the master bedroom-bathroom since this room is used every day and therefore leads to greater convenience and energy savings. The manual one is used in the far guest bedroom and is turned on only when in use. Another thing I do to keep paraffin consumption down is to keep the room temperatures at around 18 degrees Celcius when the rooms are occupied. And I turn the master bedroom-bathroom heater off when I am out of the house or asleep.

The paraffin liquid itself comes in 20 liter plastic bottles. Luckily, since petroleum prices have been increasing so have prices of these bottles. While this makes it more expensive for me to purchase them, it also gives me an incentive to use less and to make the improvements to my house sooner. However, since I use only five or six bottles a winter, the recent price increases of a few euros per bottle mean a total price increase of less than 25 euros, which is not a very powerful incentive. I suspect that EU governments have taken measures to ensure that fossil-fuel price increases are not fully reflected in heating fuel prices, either by putting price limits or by decreasing fuel taxes. I disagree with both of these. While I understand the need for everyone to have affordable heating, distorting prices in such a way simply encourages individuals to do the wrong thing - to continue blindly using fossil-fuels without trying to break this detrimental addiction.

Masonry Stove

The wood-burning masonry stove is the main source of backup heating. It is a small 700 kg high-efficiency, ultra-clean Finnish-soapstone masonry stove designed for heating approximately 50 m2 (in my central Spain climate and for a high level of insulation). It is used to heat the main living room-kitchen-dining room area; however, when the sun is able to provide most of the necessary heating needs for all of the home, the masonry stove's additional heat is able to bring up the air temperature throughout the house the necessary degrees. Nevertheless, there are five to six weeks in the winter when my small masonry stove is not enough to cover the heating gap between the energy provided by the sun (which in cloudly periods is next to nil), dump load and waste heat, and that needed to heat the whole house.

These Finnish masonry stoves burn extremely efficiently and cleanly. A very small percentage of the wood's energy is lost up the chimney, and the gases that exit out the top of the chimney are very clean. Both of these factors are due to the design of the masonry stove. The masonry stove is designed to burn the wood at extremely hot temperatures. Ultra high burning temperatures enable the wood to be burned completely and for the gases released during burning to also be burned; these ultra-high temperatures, therefore, manage to thoroughly extract the energy stored in the wood and burn the dirty gases away - efficient, clean burning. In order to achieve these ultra-high temperatures, the wood needs to be burned quickly - the faster the wood's energy is released, the hotter the fire gets. Fires in these type of masonry stoves usually last less than an hour. The trick to getting the wood to burn fast is to feed the fire lots of oxygen because fire is a chemical reaction between carbon and oxygen, a reaction that results in heat energy being released. The more oxygen, the faster the reaction can occur and the faster the wood burns away. Furthermore, it is best to spread these large quantities of oxygen over the entire exposed surfaces of the wood - the more carbon-to-oxygen surface contact, the faster the wood burns. The masonry stove has a small door that opens to extract the ashes from the bottom of the masonry stove; on this door is a small vent slide that allows for control of oxygen levels into the burning fire. Fully opened this vent allows large quantities of air into the stove. As the air enters from below the wood (which sits on a thick steel grate through which ashes fall into a metal box below) and travels up through it, the oxygen is forced to spread uniformly throughout all the surface areas of the wood. By splitting the wood into relatively thin slices, this creates more surface area for carbon-to-oxygen reaction to take place and allows for faster, hotter burns. Moreover, hot air moving over the wood helps it to burn even faster. Since the air travels a little within the interior of the hot masonry stove before reaching up into the wood, it gets heated and therefore facilitates fast burns. The fires in these stoves are very powerful, not like the slow, tame fires in old-fashioned chimneys - they are extremely hot, large, fast-moving flames. For this reason one has to be careful when opening the steel-and-glass door and adding extra wood to the fire.

The problem with extremely hot fast burns is that the huge amounts of heat released in a short period of time would make a room get extremely hot for an hour and then be cold for the rest of the day. This is where the soapstone thermal mass comes in. Soapstone is a unique kind of stone with exceptional heat absorption and retention qualities. Soapstone is able to absorb very large quantities of heat in a very short period of time and then release that heat slowly over many hours. The soapstone therefore absorbs the vast majority of the heat put out by the fire. This heat is released over many hours (in my model it is over 12 hours, other bigger models allow for heat to be released over a 24 hour period so that only one burning a day is necessary) predominantly in the form of radiant heat but also through direct conduction to air in contact with the surface of the soapstone. In a traditional chimney, the fire is made directly under the chimney exhaust and the hot air rises straight up and out, heating very little of anything except for the air over the roof of the house. These Finnish masonry stoves avoid wasting heat like this and ensure that heat gets absorbed by the soapstone by creating up-down air channels within the mass of the soapstone. As hot air rises, and refuses to fall, the hot air gets 'trapped' and 'concentrated' in these up-down exhaust air passageways; the heat of this superhot air gets absorbed by the soapstone, raising the temperatures of the stones to very hot levels. Because these stones get so hot, the thermal mass of the soapstone is divided into two parts with a thin layer dividing them; in essence, two structures are built one within the other separated by a layer of fireproof insulation. This ensures that the exterior soapstone does not get so hot as to burn at the touch. Furthermore, the insulation helps in releasing the stored heat into the room slowly over the day. The soapstone, unfortunately, is not capable of absorbing unlimited quantities of heat energy; at some point, the increasingly hot temperatures will cause the atoms of the stones to move fast enough to create expansion, at which point the stone block cracks. This is not good for the masonry stove and needs to be avoided. For this reason there is a maximum amount of wood (based on weight) that can be burned over a 24 hour period; for my masonry stove, I am limited to about 9 kg per day - I burn six in the morning and three in the evening. If I were to burn this maximum amount every day of the heating season (which I don't), I would end up burning about 1000kg of wood.

There are a number of advantages of using masonry stoves for heating. In comparison to most other types of biomass-burning (and fossil-fuel burning) space heating devices, the wood (other types of biomass could be burned as well) is burned extremely efficiently thereby thoroughly releasing all of the wood's stored energy. This results in less wood needed. Since the released gases are also thoroughly burned, and their stored energy also released, the exhaust emissions are extremely clean and almost completely limited to CO2 - with biomass-generated CO2 not being a net contributor to global-warming IF the biomass is sustainably harvested. Because the fire lasts such a short time (from 20 minutes to 1 hour in mine, depending on quantity of wood burned - from 3 to 7kg), the amount of cold exterior air coming into the house throughout the day to replace the air consumed by the fire and up the chimney exhaust is relatively small in comparison with most other continuously burning space heaters; this results in energy-savings (less wood needed) by reducing these large infiltrations of cold air. And, as mentioned above, most traditional biomass-burning devices simply exhaust most of the heat generated straight up and out of the house in the form of hot air; most masonry stoves greately limit this loss of heat up the chimney exhaust, thereby saving more wood. Another benefit is that the complete burning of the wood generates much less ashes than most other biomass-burning devices, reducing cleanup work; I only have to empty my ash box about once a week. And the thorough burning of the gases virtually eliminates creosote buildup, which practically eliminates this cleanup maintenance task common in most other biomass-buring devices. Another benefit in relation to forced-air and air heating systems is that the heat from the soapstone is released into the room primarily in the form of radiant heat, just like that of the sun, heating objects directly as opposed to first heating the air through conduction and then the air heating the objects in the room, including humans, through further conduction. This results in greater energy-efficiency as the masonry stove can keep a person warm without needing to maintain high indoor air temperatures. Radiant heating is also said to be more comfortable than forced-air heating.

I cut my own wood. Most of my three hectares of land is forested. The land all around mine is forested. Much of the land to the north half of my property is public and unwisely unkempt and uncared-for, and the lands to the south half are abandoned private lots even more unkempt and uncared for. There are numerous dead or diseased trees on and around my property - due to fires, drought, disease, and infestations (particularly processionary moth infestations) - that need to be taken away. Many other trees need to be pruned - to cut away dead branches, to make them more capable of withstanding wild brushfires, to better withstand infestations, to grow healthier and taller, etc. There is no shortage of either dead wood or live wood that should be cut away. Actually, there is way too much. There is simply too much for me to clean up. Even though by law private land owners have a legal (and moral) responsibility to keep their properties clean of dead material, this obligation goes ignored, unfulfilled and unenforced. Public authorities also have an obligation to keep public lands clean, but they too quit this responsibility. I asked the local forest rangers last year when they planned to take away the dead trees on public land that had been burned by the forest fire of three years ago, and their response was that they would never do it because the local municipality was broke and didn't have any money for such a low priority. They told me that if I was worried about this dead, burnt wood making another fire more likely and more dangerous, then I was free to cut it away. Easier said than done. Whenever a dead pine tree falls, I try to cut most of it away, but this requires time, sweat, and patience - and I have to work with a small electric chainsaw. Anyway, I have firewood piling up all around my house. Why do I go to the trouble to mention all this? For two reasons. One, to highlight that there is a difference between responsible, sustainable harvesting of biomass that helps the environment and irresponsible, unsustainable harvesting of renewable biomass like wood. Cutting away dead and diseased trees to help the remaining trees to grow stronger and healthier and to lessen the impacts of the frequent forest fires is responsible and sustainable; cutting away perfectly good trees without this having a net positive impact on the health of the surrounding trees and forest for reasons such as illegal housing developments or golf courses - or for inappropriate firewood use - is irresponsible and unsustainable. And second, to highlight that there is an abundance of biomass out there that can be harvested in a responsible and sustainable way.

Dump Load and Waste Heat

Another primary source of heating for the home is the renewable electrical system's air resistance dump load. This is not a very significant source of heating, and it is intermittent and unpredictable. The wind generator-PV panel hybrid system produces variable quantities of electrical energy throughout the day and year. I sized each - the wind generator and PV panels - so that each could provide individually on an average day practically all of the home's electrical energy needs on a low energy usage day. Because the majority of days are 'average' days for both the wind generator and PV panels, my electrical system is almost always producing significantly more electrical energy than I consume. The power center, the electrical control box that monitors the electrical energy coming from the wind generator and PVs and the battery state of charge and turns the wind generator and PVs on and off as required to prevent battery overcharging, has the option of connecting a dump load where excess energy can be diverted to and used. If this option is not used, the power center simply turns off the PVs and/or the wind generator, and that excess electricity goes completely unused. The dump load not only helps regulate excess electrical nergy flows, but it also allows that energy to be put to good use. My 24VDC 1000W resistance air heater dump load is not yet connected. I will do this soon. It will be located in the central bedroom next to its entrance door. Unfortunately, I will only be able to use this dump load for about five months out of the year; using it from mid-spring to mid-fall would cause chronic daily overheating of the interior and simply be an annoying, uncomfortable waste of electrical and heat energy.

Another small primary source of heating is waste heat. A number of things within the house produce waste heat that gets transferred to the home's interior air. There are electrical sources. These sources include the refridgerator, which pumps heat from its interior and expels it into the kitchen air. The small electrical grill oven, which leaks some heat into the kitchen during cooking. The same holds true for electric toasters, water kettles, etc. Home entertainment equipment also give off some waste heat when on. This includes televisions, DVD players, laptops, stereos, etc. The small transformer cubes that usually come with electronics are usually quite inefficient and the electrical energy losses are converted into waste heat. The electrical wiring and electrical socket connections also produce some amount of waste heat. Light bulbs do as well, including CFLs (but much less than incandescents). Another source of waste heat is from the butane gas system. Whenever the gas stove burners are lit and cooking, some of that heat goes to heating the air. The same happens when the gas demand water heater is lit. Another source is from hot water. Whenever hot water is used, for dishwashing, showers, baths, shaving, etc., part of the heat of the hot water flows to the colder surrounding room air. Another source of waste heat is living being. My wife and I put off waste heat constantly, as does my house dog. Furthermore, my wife and I frequently like to have some candles on at night, and virtually all of the energy consumed is converted directly into heat.

Direct Passive Solar Space Heating

The house is designed according to passive solar design principles in order to maximize the contribution of solar radiation in meeting the home's heating energy needs. Some of the main passive solar space heating design principles (for my property's specific site variables) are establishing an air-tight, high-insulation house envelope, incorporating adequate quantities of thermal mass, elongating the house on an east-west axis and facing the long south wall directly south and then incorporating adequate glass surface area in this wall, minimizing glass area on the remaining three walls, using appropriate colors schemes, and designing a small and open house.

The first, and most important, priority (and this applies to any house that requires significant heating and/or cooling at any time of the year) is to establish an air-tight, high insulation envelope to minimize losses of heating and cooling energy. It is pointless to attempt to heat a home that is not fairly air-tight as the home's hot air simply escapes through all the cracks and crevices in the home's envelope. And it is equally pointless to try to heat a home that has no insulation, as the hot air will simply transfer its heat to the uninsulated walls and those walls will immediately transfer that gain heat energy to the outside air. The more insulation, the better. The entire envelope needs to be well-insulated - walls, floors, ceinlings, doors, windows, utility entrances, etc. As I mentioned before, my house envelope is made completely of AAC, thereby establishing a relatively high insulation level throughout. The homogenous nature of the envelope construction helps eliminate thermal bridges where heat energy could 'leak'. The windows are double-paned low-e windows with good levels of insulation. The bedroom windows have built-in roll-down insulated exterior curtains that provide increased insulation when closed. The bathroom windows are kept extra small to reduce heat losses. I specially designed and built my own insulation curtains to cover the south wall windows at night and thereby markedly increase their insulation levels. The doors are also relatively high insulation. The doors and windows were joined to the walls by means of polyurethane foam in order to insure that the joints are air-tight, well-insulated and water-proof. Holes made to the envelope for wiring, plumbing and vents are also filled with expanding polyurethane foam. The floor of the house is further insulated by the relatively dead air spaces formed by the under-house crawl spaces. And the ceiling is further insulated by use of 'Arlita' for the roof incline formation. The sunroom that I will build to the south wall will further insulate the wall, windows and doors, as well as provide an air-lock for the entrances. And I plan to eventually apply a layer of thermal radiant insulation paint to all of the house envelope's interior surfaces, except for the tiled floors. This paint should significantly improve the envelopes insulation levels.

Practically the entire envelope and interior structure of the house is some form of masonry thermal mass. The AAC envelope provides moderate levels of heat absorption and release. The concrete slab-ceramic tile floors provide the greatest store of thermal mass. Also important are the interior brick partition walls. Most of the surfaces of the interior walls are either covered with a one centimeter layer of cement stucco or covered with ceramic or marble tiles. The masonry stove's soapstone themal mass is also very significant. Some other minor thermal mass components are the marble countertops of the bathrooms, the ceramic toilets and shower plate, the ceramic sinks in the bathrooms and kitchen and all of the kitchenware made of ceramics and glass. I plan to eventually substitute the fake marble countertops in my kitchen will real marble. And I am considering designing and building special sofa end tables made of wood or metal and glass filled with special PCM thermal mass.

The house is elongated from east to west with the south wall facing true solar south. This resulted in a long 17 by 7 meter rectangular house. The house was located in a spot within the property where the sun's winter sun would not be blocked from entering into the home's south, west and east windows by trees and bushes. The south wall incorporates most of the home's windows and allows for large (but not excessive, which could result in frequent overheating) amounts of solar radiation to enter the envelope. The east and west walls are limited to a single window; these windows are neither too small to be useless for solar radiation harnessing nor too large to threaten chronic summer overheating and unnecessary heat losses during cold winter nights. North wall windows are kept at a minimum - just enough to provide for adequate daylighting, ventilation and views.

Keeping the house small makes it easier to keep warm as there is less to heat. My interior open floor space is slightly more than 100m2; it is also important to attempt to keep the ceiling relatively low. My floor to ceiling height is 2.4 meters. More than this is unnecessary and wasteful of energy, less would be better. Of these 100m2, I try to keep the south half of the house, the master bedroom and bathroom, and the guest bathroom warm. I allow the master bedroom and bathroom temperatures to fluctuate more and be slightly lower than the south half of the house because this is a sleeping area that is basically only used at night when my wife and I are snuggly under a thick layer of blankets. The guest bedrooms only really need to be heated when they are in use, so they are often left somewhat colder than the rest of the house. An open floor plan also enables the heated air - heated by the sun, masonry stove, dump load, waste heat, etc. - to move freely to other colder areas; this way the solar heated air from the south half of the house can spread evenly throughout the south half open area and then flow into the bedrooms and bathrooms.

The future sunroom will provide an extra means of solar radiation harnessing, albeit an indirect passive solar means. The sunroom's large glass surfaces and relatively small enclosed volume will permit large quantities of solar radiation capture and relatively high air heating. This relatively hot air will flow into the house through the south wall's open doors and windows through their top half, causing a negative pressure in the sunroom that will result in colder floor-level house air to be sucked into the sunroom to replace the hot air that has moved to the house. The establishment of this thermosiphon cycle will make the sunroom a large solar thermal air heater that continuously heats the home's air throughout a cold but sunny winter day. I am also considering building special 'storm' doors that will go in front of the main entrance doors; these doors will be specially designed to meet several functions. The doors will be made of a wooden frame that permits two glass panels to be attached and detached from the door frame. When the door has the glass panels attached (in winter), the main doors can be left open to allow more sunlight straight into the home's interior to heat its thermal mass directly. At night, when the main doors are closed, the dead air spaces created by the 'storm' doors improve the insulation levels of the entrance doors. Furthermore, the main wooden frames of these storm doors will have special vent openings incorporated at their top and bottom edges to allow increased control of the air flows created by the sunroom's thermosiphon effect. Lastly, in summer the glass panels will be replaced by mosquito net panels that allow the main entrance doors to remain open during the night to allow increased night flushing of the thermal masses' accumulated daily solar heat energy and to allow the doors to remain open to better channel cooling air breezes in the evenings.

General Space Heating Systems Description

In this post I will give a general description of my space heating system. In the following posts I will discuss in more detail the individual system components. The primary source of heating for my house, which provides the vast majority of my yearly heating energy requirements, is the sun. The passive solar design of the house allows the house to be heated directly by the sun. Plenty of south-facing windows allow solar radiation to enter the house and heat up the interior. A large amount of thermal mass absorbs most of this solar radiation so that the internal temperatures do not quickly rise too high. The excess energy absorbed by the thermal mass is released during the cold night, thereby keeping the interior temperature warmer than the outside. An air-tight and well-insulated house envelope ensures that any heat energy leaches to the exterior very slowly.

Another primary, but very small, source of heat for the house is my renewable energy system's resistance air heater dump load. A dump load is an electrical load that uses up any excess energy produced by the wind-PV electrical system during the course of the day; the amount of heat energy produced is highly variable and depends on the combination of sun, wind, and energy consumption at any moment in time. This dump load is located in the central bedroom of the house. Another source of primary heat, but an even smaller one than the dump load, is waste heat from a number of sources. Electrical appliances but off waste heat for a variety of reasons. The refridgerator expels heat from within the fridge into the kitchen. The gas stove burners put off waste heat during cooking, as does the grill oven and other food cooking devices. Lights, televisions, laptops, radios, and other smaller electrical devices also put off waste heat. My wife and I put off waste heat, as does our house dog. Whenever I wash the dishes with warm water, take a warm shower or bath, or fill the bathroom sink with warm water to shave, waste heat is emitted into the rooms.

For periods of either extremely cold and/or cloudy weather, when the sun's radiant energy, combined with the smaller sources of waste heat and dump load heat, is not enough, a wood-burning masonry stove situated in the center of the south half of the house provides backup heating to supplement the sun's radiant energy. This soapstone masonry stove is only sized to provide heating for a more-or-less 50 m2 area (in this type of climate and with a high insulation envelope), so it is not capable of providing backup heat for the whole house. This wood-burner can be fired twice a day with a maximum total of 9 kg of wood burned daily.

Since the masonry stove is incapable of providing backup heating for the entire house, I sometimes have to resort to using a paraffin heater to keep the corner end bedrooms warm. The master bedroom gets heated more often than the guest bedroom because we use the bedroom on a daily basis whereas the guest bedroom is used only occasionally during winter and can therefore be left colder. We have two heaters, one manual and the other electric. The electric model turns the heater on and off automatically; it has built-in electronics that monitor the temperature, time and consumption and can be programmed to turn on at a set degree and off at a different set degree, to turn on at a certain hour and off at another, and to turn off when the paraffin level is low. These automatic features significantly help reduce paraffin consumption in comparison to a manual one.

I plan to build a sunroom to further exploit the sun for providing the home's heating energy requirements. The sunroom is an integral part of the original house design but is a feature that can be added on whenever. When I have the time and resources to build it, I will. This sunroom is an indirect passive solar heating system. The sun will heat the air within the sunroom to relatively high temperatures. This heated air will flow into the house, creating a negative pressure in the sunroom and a positive pressure in the house, both of which cause cold air at floor level within the house to flow into the sunroom, thereby creating a circular thermosiphon effect.

I also plan to build an active solar heating system for the house. This system will be composed of solar thermal water heating panels attached to the bottom half of the south wall within the sunroom. These panels will be attached by plumbing to special PCM-filled baseboard radiant heaters within the bedrooms and bathrooms. The PCM thermal mass will store excess solar energy for night time heating. The hot water will be pumped to the radiant heaters using a small pump connected directly to a small PV panel - when the sun shines enough it heats the water and runs the pump at the same time. No sun, no pumping of cold water.

Reuse and Recycling of Wastes

The construction of the house has generated some left over construction material and some construction wastes. The amount of construction wastes are not excessive, so I should be able to put them to use on my property in one way or another some time in future. And if over time I see that some of that waste will not end up getting used, I will try to find an appropriate recycling center.

There were left over construction materials ( AAC blocks, bricks, gravel, sand, lots of wood palets, etc.) which I can use in future projects. In particular, I still need to build a sunroom to my house, and I plan to build a large greenhouse for food production. These two projects will probably absorb most or all of this excess construction material. I also plan to build several dog houses with these left over materials. As for the wood, I also plan to build numerous bat and bird houses, a moveable chicken coop, as well as some house furniture, and other odds and ends. Some of the construction material waste, which is primarily chunks of broken AAC, brick and concrete, have already been used in the foundations of the wind generator, PV solar tracker mount, and one dog house. l plan to use the rest for the foundations of the sunroom and greenhouse, as well as for the other dog houses that will be built. There were also several garbage bag fulls of polyurethane foam cuttings of waste. I plan to use these cuttings by triturating them into fluff and using this fluff as insulation, either to make insulated cement blocks or by filling wall cavities with.

Whatever other construction waste I can not find a use for, I will take to an appropriate recycling center. However, I do not expect that I will have to do this as I am confident of finding uses for all construction waste. Luckily, if I do not, whatever is to be recycled will be so little that I can put that small quantity into the trunk of my Yaris and drive where needed.

Small Open House

Small size is a key aspect of a 'green' home. Building a small home is crucial for minimizing resource use. A small house minimizes use of energy resources and construction materials in its making, and it uses less energy and materials in maintenance and renovation works compared to a large house. A small house also minimizes resources needed for furniture since there is less to furnish. It minimizes use of energy resources since there is less space to heat and cool, to keep lighted and electrified. Also, other resources are minimized, such as water and detergents, since less cleaning is necessary. Furthermore, an open floor plan house reduces material resources even more by eliminating extra walls, doors and system components. Instead of needing three radiators for three rooms, you can get by with one or two bigger ones.

The trick is to make a small house that meets one's needs and is comfortable. Good house design is required to accomplish this. I applied a large number of 'small house' design principles. One of the most important principles is to create multifunctional rooms, rooms capable of satisfying several needs. I did this in my house in a number of ways. First, hallways tend to be an inefficient use of space since their only function is to provide a passage way from one room to another. Good design can situate rooms such that hallways are either eliminated or greatly reduced; furthermore, the passage way function can be fulfilled by other rooms. In my house, hallway space is next to nil. The rooms have been located so as to minimize passage way needs. And the main kitchen-dining-living room open area fulfills most of the passage way needs. The living room also acts as a place for reading, study, conversation, watching movies and listening to music; it's north wall has a large built-in library; it houses the electrical cabinet that contains all of the home's safety switches, system meters, power center, inverter, etc.; and it contains the masonry stove, the main backup heating system. The kitchen is for food and kitchen appliance storage, cooking, cleaning, and clothes washing; it contains the recycling center; and the kitchen island acts as a handy place to eat a quick snack. The dining room has a large table for eating, but it is also used for studying/research, for sewing work, for fixing small objects, and for other handcrafts; it contains an old Singer wood and steel foot-powered sewing machine and will also in future have a corner china cabinet. The bathrooms, besides acting simply as such, act as storage rooms for all type of bathroom supplies and other odds and ends. The master bedroom has a small library in one corner of the room and a built-in closet. And the other bedrooms also have multiple functions. The roof acts as a terrace with several important functions, and the crawl spaces act as waste storage and house important system components. The sunroom will act as an outdoor living space, will be for solar cooking, will house some plants and one of my dogs, and will store some firewood, as well as performing its primary functions of harnessing solar heat and acting as an air-lock for the house entrances.

One has to use furniture that makes best use of the limited space. Corners of rooms are usually inadequately used because of inappropriate furniture, so this room space goes underutilized. Corner furniture is very appropriate. In my home I have special corner shelves next to both house entrances. In my bedroom I have wooden corner shelving that acts as a library. I plan to build a special corner china cabinet for the dining room and other wooden corner furniture. Beds also need to use space efficiently. Either a normal bed with special sliding boxes underneath (which I currently use) or a special bed with built-in drawers/cabinets (which I plan to build) can be used to take advantage of the ususally wasted space underneath. In guest bedrooms and the living room, sofa-beds allow the room to be primarily used for a specific purpose, such as a movie room, and then quickly made into a bedroom - both of my guest bedrooms have sofa-beds. Raised beds that have a table underneath also make very good use of space. Built-in cabinets/shelves/closets usually make better use of space because they are specifically built to fit that unique space, take advantage of existing structural elements, and usually reach from the floor all the way to the ceiling. I use floor-to-ceiling built-in shelves and closets in the entrance, living room, bedroom, and bathroom. There are a wide variety of furniture designs that make efficient, multifunctional use of space.

A number of things can help a small house appear much larger than it actually is, making it more pleasant to live in. Coloring schemes are important. Light-colored rooms, especially white, visually appear larger than darker colored rooms. A white ceiling appears much higher than a dark colored ceiling. Most of the walls, ceilings and floors in my house are some tone of white. Light-colored furniture helps to make the room appear uncluttered, and therefore larger. All of my bathroom and kitchen furniture is white with light grey countertops. My living room sofa pieces are a light blue and white. And the guest bedroom sofa-beds are light-colored. Living room curtains are also very light in color. Mirrors are especially good at making a room appear visually larger than it is, and I exploit this fact by using extra large mirrors in my bathrooms. I also plan to put large mirrors next to the two entrances, one on the west and the other on the east wall directly facing each other, which will create the unique visual effect of a long never-ending room. Shiny light-colored glazed ceramic tiling mixes the effects of light colors and mirrors. My bathrooms use a lot of shiny glazed white wall tiles and floor tiles. Very thin furniture and furniture with glass also help to make furniture pieces look small and thereby make the room look larger. The corner shelves next to the entrance doors are made of thin black metal legs and glass shelves, which makes them both stand out and yet be inconspicuous. The living room coffee table is also made of thin black steel and glass, making the center of the room seem much larger. I currently have a medium-sized dining room table with a varnished pine wood top and white-painted wooden legs; the relative thinness of the top and legs and their light color make the room seem quite large. However, I plan to build a much bigger dining room table out of pine wood which I will paint a darker color, but I will make the top and legs relatively thin and most of the top surface will be glass. This should give the same effect as the black steel and glass corner shelves - to stand out without looking massive. I also plan to build a corner china cabinet for the dining room made of wood and glass.

An open floor plan makes the interior seem larger than it is. A large open space that incorporates a number of 'rooms', just as my entrance-living room-kitchen-dining room-hallways space does, makes each individual 'room' seem much larger than it is because the boundaries of each room are nebulous. The more and the farther the eye can see, the bigger the space one is in feels. From where I am writing this, on my living room sofa, I can see all of the entrance, the two tiny hallways, most of the dining room, much of the kitchen, and, with the doors open, a little of one bedroom and much of the guest bathroom. My eye can take in over half of the house, and I feel like my living room is huge. Another thing that enables the eye to see more and farther is lots of big windows. Big windows that allow one to look out and see the landscape give one the impression that the room they are in and the landscape they are looking at are connected. This makes the room feel larger than it is. The south half of my house, with the main living areas, has seven large windows that create a clear impression that this living space is an interface between the outside and the inside.

Lastly, a small house should take advantage of the exterior. Exterior spaces can be conditioned in one way or another to be usable in appropriate weather. This increases the number of 'rooms' of the house, making it bigger without making it bigger. In my house, the roof terrace will be a large living space for reading, napping, studying, listening to music or watching movies, playing games, etc. And this living space is the size of the house! The future sunroom, while not exactly being the exterior will not quite be the interior either, will act as another small living room and kitchen. Some fifteen meters from the house in the center of a clump of trees I have an arrangement of wood and steel garden furniture, a small coffee table with two small chairs and one small bench, next to a hammock and a outdoor garden recliner; this set up acts as a pleasant outdoor living room that my wife and I take advantage of frequently, especially when we have guests and the weather is nice (which is most of the year here in central Spain). There are many ways to use the outside just like the inside.

Future Sunroom

I plan to build a sunroom that will cover the entire south wall surface of the house. This sunroom will have a number of important functions. The primary ones being solar heat capture and added insulaiton. The sunroom will act as a greenhouse that traps solar radiation thereby heating the interior air of the sunroom during sunny days to relatively high temperatures. On such days the doors and windows can be opened to allow this hot air into the home. The hot air flowing into the room will cause negative pressure in the sunroom that will suck in cooler floor-level air from inside the house. This creates a circular thermosiphon effect where hot air goes into the home through the top half of the open doors and cold air from the house goes into the sunroom through the bottom half. Considering the size of the glass space and the relatively limited enclosed volume of the sunroom (which will only be two meters wide), on a sunny day this sunroom can provide the house with a substantial amount of extra solar heat. To ensure maximum solar radiation penetration, the sunroom will be single-paned and will use normal glass. The wood structure will be as thin as possible to block as little solar radiation as possible. And the inclined glass roof will be as steep as practical to ensure the least radiation reflection in winter. The floors will be made of white concrete; this will help absorb excess air temperatures to ensure against overheating while the white color keeps most of the solar radiation heating the air rather than the concrete. This stored heat will then be released during the night, helping to moderate nighttime sunroom temperatures.

The sunroom will act as insulation in several ways. The relatively dead air space created by the air-tight sunroom's enclosed volume provides increased conductive heat resistance to the south wall and windows of the house. I am considering lining the interior of the sunroom's glass with low-e film to reduce radiative heat losses (any comments as to the practicality and wisdom of doing this would be highly appreciated). The thermal mass within the sunroom helps moderate the sunroom's nighttime temperature, thereby helping further reduce conductive heat losses. And the sunroom will act as air-lock entry for my two entrances. This ensures less heat and cool is lost whenever I enter or exit these entrances.

This sunroom will also help cool the interior of the house. The very top of the sunroom will not be made of glass but rather of wood and PV panels. This will create a 'roof overhang' that will block summer solar radiation from entering through the south house windows. Also I plan to incorporate special exterior roll-down shadecloth curtains to help further block solar radiation heating any of the south wall's surface. I am also planning on adding cool tubes to the house for summer cooling. I plan to combine this with a solar chimney, and the sunroom would act as the solar chimney. Placing vent windows at the very top corners of the sunroom and leaving them open in summer would cause hot air to rise up and out of the sunroom. This air would be replaced by air from within the house through open doors and windows on the south wall. The negative pressure created within the house would help to suck air through the cool tubes into the home, thereby providing cool fresh replacement air during the hottest times of the day. Whether I implement this cool tubes-solar chimney combination will depend on the hottest summer interior temperatures reached once the house is completely finished.

The sunroon will also act as an outdoor living room. It will provide a convenient place for solar cooking. It will be an ideal location for storing a large quantity of split firewood (all the way at the east side). It will also be ideal for our house dog (better he shed fur in the sunroom than in the house). We will also use it for some solar drying activitites and possibly for some small gardening tasks like sprouting seeds and growing some herbs. And no doubt as time passes I will find many more uses for it and think of possible modifications to help reduce resource use of one form or other.

The structure of the sunroom will be made of wood and glass with concrete tile and brick floors. As mentioned the concrete tiles and bricks will be white for the reasons already mentioned but also to reflect more radiation onto the south walls (which in future will have mounted solar thermal water heating panels for an active solar space heating system) and into the south wall windows for extra solar radiation and daylighting. The glass will be single-paned with possibly a low-e film. The supporting structure will be made of wood treated with white protective paint. I do not like the use of wood for reasons mentioned in previous posts. It requires a lot of maintenance to last a reasonable amount of time. But I feel it is the only practical choice I have. Since I plan to build the sunroom myself, and I know how to work and design with wood, it is what I am left with. I don't want to make a massive masonry structure that would block a lot of light and have unnecessarily high embodied energy. And I don't want to use metal since it is such a powerful heat conductor; plus the fact that I do not know how to weld at this scale and would require a lot of energy to do so. As for PVC, it would be ideal, but, as mentioned earlier, I am trying to now avoid this product where possible on the recommendations of Greenpeace - not to mention that I would need to learn how to build with it (but this is a minor consideration). So for now I plan to use wood unless some better alternative suggests itself before its construction.

Crawl Spaces

Under the AAC house envelope there is a low crawl space. This crawl space was necessary in order to put several important system components. It also provides an extra measure of insulation by establishing a relatively dead airspace under the house. The house envelope rests upon thick brick walls which provide it a level surface to sit on. These brick walls divide the crawl space into two completely separate long, low and narrow areas. The ground surfaces were left bare. The walls were painted white - in order to make visibility easier with limited light. Each crawl space has a small 80 cm square metal door entrance at the east wall. The interior ground to ceiling height at these entrance doors is about 1.40 meters and gradually decreases moving toward the west wall, where the height is about 30 cm.

The south half shelters the renewable energy system's house batteries. It also has an 80 cm by 60 cm brick pillar that sits directly under the 700 kg masonry stove location in the house and provides the AAC floor panels with the necessary extra load-bearing support. The batteries were placed directly under the location of the power center, inverter and converter within the house - they need to remain close to minimize electrical resistance within the connecting wiring. Due to the low 90 cm height of the ceiling at this point, a 60 cm deep hole was dug into the ground in which to build the concrete and AAC battery box. This box was built between the central brick wall of the crawl spaces and the masonry stove support pillar. Within this box are eight high capacity house batteries wired at 24 V DC. A ventilation tube runs from this box to the exterior and has a vent fan incorporated within it near the box. In order to ensure adequate replacement air for this ventilation fan, a number of holes were drilled into the metal entrance door.

The north half shelters the composting toilet's batch composter unit. This rotating four-chamber batch composter is situated directly below the two toilets of the bathrooms; each toilet dumps straight down into a separate chamber. This composter decomposes the wastes over several months into a highly beneficial, fertilizing humus. When the chamber under the master bathroom toilet becomes full, the chamber with the oldest humus is emptied and then the unit is rotated clockwise to place this empty chamber under the guest bathroom toilet. The humus is then used to fertilze my fruit trees. I had also originally planned to place several other system components within this crawl space but at the time of construction decided against it because of the inconvenience of regularly going in and out of these crawl spaces. While the composter only needs to be emptied several times a year and the batteries only need to be maintained several times a year, these other system components require tasks that need to be done much more regularly.

I made a small AAC closet addition to the exterior side of the crawl space brick wall so that the necessary, regular tasks would be easier and more convenient to accomplish. In this back wall enclosure is the urine bucket; my ceramic toilets are specially designed to separate the urine and the feces with the feces dropping into the composter and the urine flowing into a collection bucket. This collection bucket needs to be emptied about every ten days; I use this urea to fertilize the trees on my property. The back wall enclosure also has a wastewater overflow chamber to handle situations where excessively large quantities of water are drained through the waste plumbing at once. Within this chamber I will put screen nets to filter out large substances from the wastewater, filters which will require emptying several times a month; these substances will then be put into my garden compost bins. Within this insulated enclosure I will also have a pressure pump and pressure tank to pressurize the house water. I have located them here because I have placed the home plumbing's main shut-off valve in this enclosure, and it was more practical to locate the pressure pump and tank in the same place.

Since there is a lot of space left within these crawl spaces, I try to take advantage of it. I use this extra space to store wastes, such as paper, glass and metal jars, construction foam cuttings, etc., to either be reused or recycled later on. I always keep an eye out for opportunities to put these wastes to good use. I also store excess firewood in these crawl spaces to keep it out of the weather. And I also store other odds and ends that do not require frequent trips.

Roof Terrace

The entire top outer surface of my house is a roof terrace. I have yet to finish it. This terrace has several functions. Besides the obvious function of acting as an outdoor living area where there are frequent pleasant breezes, it has several other more vital charges.

The terrace floor is at a 2.5% incline; this incline was formed using 'Arlita', which is a construction material made of finely porous clay (similar to the AAC) in the shape of small gravel-sized beads. Arlita is a material that can be used to substitute gravel aggregate in concrete mixtures and is done so for a number of applications because the Arlita greatly reduces the weight of the resulting 'concrete' and also insulates it. The Arlita ensured that the 'concrete' weight of my roof terrace incline was minimal, and it provides an extra layer of insulation for my roof, especially over the south half of the house where the inclination thickness is greater. Furthermore, since it is made of clay, and is thereby a decent thermal mass material, it provides extra thermal lag for my roof which further helps in maintaining comfortable interior temperatures. The surface of the roof terrace acts as a cool roof because it is painted a shiny white; this color enables the terrace surface to reflective away most of the sun's intense summer solar radiation, thereby helping keep the interior cool. I plan in future to repaint this surface with a ceramic-based radiant insulation paint which has the ability to reflect away close to 100% of the sun's radiant heat; this will have a significant impact in keeping interior temperatures low in summer.

The roof terrace accommodates the solar water heating system (which is not yet finished). In a small well-insulated 1.25 m long by .9 m wide by 1.5 m tall shed made of AAC, that sits directly above the bathroom-kitchen partition wall, is sheltered a special 300 liter hot water storage tank along with all of its corresponding plumbing and safety devices. This small rectangular structure is oriented so that its long sides face north and south. The north wall contains the double doors while the south wall supports on its exterior surface the evacuated solar thermal water heating tubes that maintain the water within the storage tank hot. The southwest corner of this little structure contains the exhaust channel from the backup gas demand water heater, which is located directly below this channel. The roof terrace also accommodates a two meter tall chimney exhaust column that lies directly above the masonry stove's exhaust piping, and there is another two meter tall exhaust column with a ventilation windball attached at its top that belongs to the compost toilet vent system.

Last, but by no means least, is the rainwater collection function of this terrace. The entire surface of the terrace floor slopes downward toward the back of the house where there is a raingutter that runs the entire length of the north wall. This gutter collects this falling rain water and channels it to two downspouts located at each extreme. These downspouts flow down into two large rainwater collection storage deposits. I have yet to purchase and connect these two rainwater deposits but intend to do so relatively soon.