The HRV will have two fans.  One will draw in fresh air from outside and the other will push out stale inside air.  The fans push the air through a chamber made of series of air passages in which the direction of airflow alternates.  These air passages are separated by a conductive membrane, aluminum in the better units, that allow the heat from the warm air to transfer the colder air. In a house with forced air heating, the warm air is drawn from the return air duct and fresh air supplied a few feet downstream.  A better system draws the stale air from the kitchen and bathrooms, which are the main source of pollutants and humidity, using a separate duct system.  In a house with hot water heat, a full ducting system is used with the warm air  drawn from the bathrooms and kitchen and the fresh air is returned in the bedrooms and other living areas.  In the winter, since the fresh air is dryer, it will drop the humidity in the house down so there is little or no condensation on the windows

When looking at an HRV there are two main factors to consider in terms of efficiency.  The first is the sensible efficiency, which is the amount of heat moved from the warm air to the cold air and can vary from less than 40% to more than 80%.  A higher number is better.  The other factor is the amount of electricity the unit uses.  The units can vary from under 40 watts to more than 200 watts for similar sized units.  This is mostly due to the type of motors used in the units.  You want the unit that uses the lowest watts.  A listing of most HRVs is available from www.hvi.org

The HRVs are sized according to the size of the house, with a larger house needing a unit that can move more air (higher Cubic Feet per Minute orCFM ).  This can be determined by taking the square footage of the house and multiplying it by the ceiling height, giving the volume of the house.  This is then multiplied by the desired air changes per hour (usually 0.3 -0.5) and then dividing by 60 to get CFM.

The first winter we were living in our house, we had not yet installed the HRV and had condensation problems so bad that we had to have towels at the bottom of all the windows.  Since we have installed the HRV, we have had next to no problems with condensation, except for the coldest days, and even then it is minor.  I selected the Lifebreath HRV as I found they had the lowest power usage and one of the best sensible efficiencies.

One way is to plant deciduous trees and shrubs on the south, east and west side of the building.  During the summer the trees will shade the building and block the heat from hitting the house.  It also can have a cooling affect around the building due to the transpiration from the plants.  In the fall and winter, the trees will loose their leaves and will let the sun shine in, heating the house.  The advantage to using trees is that they closely track the temperature changes during the seasons, with the leaves budding in the spring once it has warmed up and falling off in the fall once the temperature has dropped.  The disadvantage to using trees and shrubs is that the woody mass of the tree will always shade the building, reducing the amount of sun in the winter.  The trees also take some time to grow to the point where they will be an effective shade.  They can also be a problem if solar panels are installed on the roof and are shaded by the trees.  This last problem can possibly be avoided by having the solar panels ground mounted beyond the shade of the trees.

A second way to shade the house is to use overhangs. You can calculate the depth of the overhang by finding the angle of the sun at the summer solstice – June 21 (90° – latitude + 23.5° = ss) and winter solstice – December 21 (90° – latitude -23.5° = ws).  Then take the distance from the bottom of the window to the bottom of the overhang (wh) and the distance from the bottom of the overhang to the top of the window (oh).  Then use the formula wh/tan(ss) to get the best overhang for the summer solstice and the formula oh/tan(ws) to get the optimum overhang for the winter solstice.  You want the overhang to be less than the winter solstice calculation and more than the summer solstice calculation.  For an example, I will use a house at 44°N latitude. The bottom of the window is 78″ from the bottom of the overhang and the top of the window is 18″ below the bottom of the overhang.

The angle at the summer solstice = 90° – 44° + 23.5° = 69.5°
The angle at the winter solstice = 90° – 44° – 23.5° = 22.5°

Summer overhang = 78″/tan(69.5°) = 78″/2.67 = 29.2″
Winter overhang = 18″/tan(22.5°) = 18″/.414 = 43.5″

So the overhang should be between 29.5″ and 43.5″.  Since you want shading for some time on either side of the summer solstice add about 6″ to the overhang.  In this case I would use a 36″ overhang, which would give complete about 6 weeks on either side of the summer solstice.  The disadvantage of a set overhang is that the temperatures are not the same the months before and after the summer solstice, which means there is more shading than you want before the solstice and not enough after the solstice.  The advantage is that you have the shading immediately after the house is built, and the shading is predictable.

Another option would be to build a trellis overhang, which would be a hybrid of the two above systems.  The trellis which would be built the same depth as an overhang would give some shading by itself, but if it is covered with a deciduous vine, such as grape, the leaves would give additional shading during the summer and in the fall the leaves would drop and give you more light before the winter solstice through the holes in the trellis.  You would have the added bonus of grapes to harvest.

The nature of the electrical load on a construction site is quite sporadic.  A saw is only run when a board needs cutting, a compressor only runs once in a while to recharge.  In the meantime, the generator is running all day, since the workers don’t want to be bothered turning it off and on as it is needed, so it is wasting fuel for no useful work for most of the day.   Using a battery bank and inverter, there is only a very small amount of standby loss, and the inverter only turns on when power is needed.  Since most tools are less than 15amps, a 2000 watt inverter would produce a sufficient amount of power.  If more tools are used at once, a larger inverter, or multiple inverters could be required.  The cost for this type of setup would not be a lot more than the cost of a good quality generator.

After the construction is finished, the batteries and inverter could be attached to a generator panel in the house to act as a backup power source in the event of a blackout.  A generator panel is an electrical sub-panel that feeds the critical loads in the house, such as the freezer, refrigerator, and well pump.  It includes a main breaker that can switch the power source from the electrical grid to a generator input in the event of a power failure.

If you are planning to add solar panels to the house, in either an off-grid or grid-tied setup, it would be worth considering purchasing the panels and inverter early in the building of the house in order to use them to power the construction site.  The solar panels could be mounted on a temporary mount out of harms way and the batteries and inverter put in a box to keep them out of the weather.

The tankless hot water heaters also use less fuel to heat the water.  A conventional gas fired hot water heater will have an efficiency of about 60%, meaning that 60% of the heat from burning the gas will be used to heat the water, the rest of the heat is lost up the chimney.  For a tankless hot water heater the efficiency is usually about 80-85%, meaning at least 20% more of the heat generated goes into the water and is not lost up the chimney.

On the downside, since the tankless hot water heater has no stored hot water, when you turn on the tap, it will take about 10 seconds longer for the system to kick in and get up to temperature than a conventional hot water heater.  This can result in more water use as you wait for the water to heat up.  If you are on a marginal well this should be a consideration.  On the other hand the water that is used while waiting for it to heat up can be captured in a bucket and used for other things such as watering the garden.  The other disadvantage is that if you have hard water, there is more maintenance involved.  The tankless hot water heater works by having a the water flow through a series of small pipes that go back and forth over a burner.  In a hard water area these small pipes will build up scale and if left untreated will eventually plug up the heater.  To avoid this you have to flush the system with a weak acid solution to dissolve the scale.  There are kits available that have a pump and an acid solution and when installed, you need to put in some extra valves and connectors to allow you to connect to the unit.  I flush my unit twice a year, once in the spring and once in the fall.

Another advantage of the tankless hot water heaters is the size.  The unit I have (Takagi TKD20) is only about 20.5″x14″x8.5″ and hangs on the wall out of the way.  In my house the same unit is used for both domestic hot water and for generating hot water for theinfloor heating.  This saves a lot of room in the utility room, as there is not tank and no furnace.  The unit I have can generate about 7 gallons of hot water per minute, so with low flow fixtures, you could have two people using hot water at the same time and still not run out.

The rubble trench foundation have been used for thousands of years by was popularized early in the 20th century by Frank Lloyd Wright, who used it in a number of his buildings.  Today rubble trench foundations are commonly used in straw bale buildings due to their low environmental impact.  A major advantage of the rubble trench foundation is that it is not susceptible to frost heaving. Since the foundation is made of materials that rapidly drain, there is no water to freeze, and so no frost heaving.  The disadvantage of a rubble trench foundation is that it needs to be in well drained soil where the water table is below the bottom of the rubble trench.  It also works best on a sloped site where the drainage from the bottom of the trench can go to open air.  If the water table is low enough and the soil well enough drained, drainage can be accomplished on a flat site with a dry-well.  A dry-well is a hole that is below the drainage point that is filled with loose gravel or rubble and will accept the drain-water and slowly disperse it into the ground.  The dry-well has to be above the water table in order to work properly.

When building using a rubble trench foundation, you will probably need to get an engineer’s drawing made for it, as it is not included in the building code in most places.  The soil may have to be tested to see if it support the rubble trench and the building above it.  The basic procedure to create the rubble trench foundation is to first dig the trench, usually about 16 inches wide, with straight sides to a few inches below the frost line (4 feet in Southern Ontario).  This is most easily done with a backhoe, but can be done by hand.  The trench must be dug so that there is a slope of at least 1/8 inch per foot of slope for drainage.  Once the trench has been dug, place landscape fabric on the bottom of the trench and cover it with a few inches of gravel.  Then place a 4 inch perforated pipe on the gravel and have it follow the drainage slope either to open air or to a dry-well.  The sides of the trench should then be lined with the landscape fabric in order to stop silt from migrating into the rubble and plugging up the drainage.  After the landscape fabric has been laid the trench should be filled with washed 1 1/2″ stone or crushed concrete about a foot at a time and then tamped to reduce settling.  After the trench has been filled to grade, forms must be laid in a layout according to the engineered drawings  and the re-bar installed.  The concrete grade beam can then be poured.  Once the concrete has cured, the forms can be removed and the building can begin.

To understand how a ground source heat pump works, first a little bit of basic physics.  For a molecule of liquid to speed up enough to become a gas (vaporization) it has to absorb a lot of heat  This is called the latent heat of vaporization.  The same amount of heat is lost when a gas condenses to become a liquid.  To heat up 1 gram of water from 0C to 100C takes 100 calories, but to turn that same gram of water from a liquid at 100C to one gram of vapour at 100C takes 540 calories.  You can see that it takes a lot more heat to cause a phase change (liquid to vapour) than to heat a liquid to boiling.  When a gas is compressed, it heats up.  Image a gas in a cylinder with a piston.  When the piston raised into the cylinder, the molecules of gas start bouncing into the walls of the cylinder more rapidly since the molecules are travelling at the same speed, but in a smaller space.  This more rapid collisions translates into an increase in temperature.  One last bit of science.  As the pressure in a gas increases the temperature at which it condenses into a liquid also increases because the molecules of the gas are closer together at a higher pressure and so more easily gain the order required to condense into a liquid.

We will start the process where the refrigerant is a liquid.  The liquid refrigerant pumped into a device known as a heat exchanger and is brought into close proximity with the ground temperature water which has been pumped in from the underground loop.  The liquid refrigerant then boils to become a low temperature gas and absorbing a large amount of heat in the process (latent heat of vapourisation).  This low temperature gas is then sent to the compressor.  The compressor increases the pressure in the gas and in the process increases the temperature of the gas.  This high temperature gas is then passed into a condenser where cool air or water from the heating system is passed in close proximity to the gas in another heat exchanger and the heat from the gas is transferred to the air or water, causing the refrigerant to condense back into a liquid, and losing the heat of vapourisation.  The cooled liquid is then passed through an expansion valve lowering the pressure and therefore the boiling temperature of the liquid.  The liquid is once again passed by the ground water and since the pressure has been dropped the liquid can boil at a lower temperature and so absorbs the heat from the groundwater and the process begins again.  In the process of transferring heat to the refrigerant, the groundwater is cooled below the ground temperature, and it is then recycled to the ground loop where it heats up again.  During the cooling season, the process is reversed and instead of removing heat from the groundwater, heat is added to the groundwater.

In the process of moving the heat from the groundwater to air in the house, electricity is used to run the compressor and the water pumps.  The amount of electricity used, however, is less than if the electricity was used in a resistance heater.  This is called the Co-efficient Of Performance (COP).  A resistance heater is considered to have a COP of 1 and a ground source heat pump will have a COP between 2.8 and 5.2 depending on the type of loop and efficiencies of the pumps and compressors.  This means a ground source heat pump will deliver between 2.8 times and 5.2 times as much heat per kilowatt-hour of electricity as a resistance heater.

In my discussions with a heat pump installer, the vertical loops are recommended in Canada due to the more consistent and higher heat available deeper underground since the frost can reach up to 4 feet deep in the more populated areas of the country and even deeper further north.

Rammed earth construction has been in use since the neolithic ages and there are archeological sites in China from 5000 BCE where rammed earth was used for walls and foundations.  In the past binders such as blood or lime were used.

Rammed earth construction is particularly good in passive solar design, as it has a large amount of thermal mass, which will even out the temperature fluctuation during the day.  It also has the advantages of being almost soundproof and fireproof.  In some sites, other materials, such as glass or shells are added to the mixture to give it additional texture.  It can also be coloured by adding pigments to the mixture.  Variations can be created by using different mixture in the various layers.  Since the rammed earth is used as the finshed wall, it is very non-toxic, as the materials are soil and cement, so it is a good construction method for those with environmental allergies.

The technique for construction is quite simple.  Forms are put in place in the shape of the desired wall and then a damp mixture of sand, clay, gravel and portland cement is placed in the forms four to ten inches deep.  The mixture is tamped down with either a mechanical pogo stick tamper, a pneumatic tamper or by hand with a plate tamper until it has been compressed to about half it’s original thickness.  Another layer is then put in and the process is repeated until the top of the form is reached.  The form is then removed and move up so the process can continue until the desired wall height is reached.

An interesting variation on rammed earth was developed in British Columbia, called SIREwall, which stands for Stabalized, Insulated Rammed Earth wall.  In their process, a piece of foam insulation of the desired thickness is placed vertically in the center of the form and the rammed earth is placed on either side around reinforcing rebar and then tamped down using custom selected mechanical tampers.  This creates a wall that has an insulated core, but has the thermal mass exposed on the interior and a durable rammed earth exterior protecting the insulation.  This results in a wall between 14 and 21 inches thick.  The SIREwall process has a protocol that controls the soil consistency, the method of mixing and curing to produce a wall with predictable, cost-effective results.

Properly done, a rammed earth construction will create a building that is weather resistant, soundproof, insect and rodent proof, inexpensive to heat and cool, very comfortable to live in and will probably last for centuries.

SIPs usually made of two layers of Oriented Strand Board (OSB) separated by a layer of foam insulation.  The foam can be Expanded Polystyrene (EPS), which is a foam made of small beads fused together, Extruded Polystyrene (XPS), commonly a blue or pink solid foam board, or Polyurethane foam, a solid white or beige foam.  The SIPs are made to order in a factory and then shipped to the building site.  The sections can be anywhere from 4 feet to 24 feet in width.   While the wider sections provide a better insulate wall (since there are no joints), they require the use of a crane and a larger building crew for installation.  The SIP sections are joined together during installation using a spline, often made of lumber and then sealed with low expanding foam, specialized mastic and/or SIP tape.  SIPs can be used to build not only the walls of a building, but can also be used to build the roof of the building, however, extreme care must be taken to make sure the joints are completely sealed, since if air can pass through them, it will carry moisture that can condense and produce an environment conducive to the growth of mould.  This has been the cause of structural failures in the past, particularly in very cold climates.

A Do It Yourselfer can build with SIPs, but you would have to make sure to get smaller panels that can be handled by one or two people.  The cost will be higher than building with standard framing, but will result in a better sealed home.  If you are contracting the work out, or doing your own general contracting, SIPs would be a good way to go since the labour costs would be less than for framing and insulating.

Some disadvantages of SIPs are that you have to be quite exact in your measurements when building the foundation, as the SIPs are cut to fit the plan, and field modifications require the use of specialized equipment.  The other issue is that SIPs don’t have a lot of thermal mass, but this can be offset by designing extra mass into the interior of the house.

From an environmental standpoint, dimensional lumber should not even be considered, as it requires the cutting down of the largest old growth trees to get lumber large enough.  The other problems with dimensional lumber is that you are limited to just over 15 feet of span for 2×12, which is the largest commonly available lumber.

The second choice is I-joists, which are made by having two pieces of wood, typically 2×3, connected by a piece of plywood or Oriented Strand Board (OSB) creating a beam shaped like the letter I when viewed from the end.  There are some I-joists where the top and bottom members are also made of laminated lumber.  This results in 60% less timber being used vs and equivalent piece of dimensional lumber.  The I-joists are commonly available with up to 16″ depth, and are manufactured with different widths of lumber for the top and bottom pieces.  With the heaviest I-joists spaced at 12″ centers, the longest span is about 32 feet.  An advantage of I-joists is that they can be cut to length on-site and many have pre-punched holes for running electrical and plumbing lines.  Holes can be cut for ductwork, but you must follow the guidelines  from the manufacturer for placement of the holes.

I my opinion the best choice for floor framing is the open web trusses which consist of a top and bottom plate which is joined by web that forms a series of triangles.  The top and bottom boards are usually 2×3 or 2×4 lumber that is finger jointed together to form the long spans and the web can be either wood or steel.  The trusses can be manufactured with depths up to 24″ for spans up to 40 feet.  The biggest advantage of the open web trusses is that there is an open space in order to run all electrical, plumbing and ductwork with ease.  The disadvantage of the open web trusses is that they are much more limited in the ability to be trimmed on site with typically only about 2-3 inches on each end being trimable, so the measurements must be fairly exact when they are ordered.

Both the I-joists and the open web trusses, being engineered products will result in a quieter floor, as you don’t have the warping and twisting found in dimensional lumber.

In my home I used the open web trusses and found them very easy to work with.  They are much lighter than dimensional lumber and having all the open webs made it much easier to route wires and pipes without having to worry about drilling holes.  Care must be taken when installing them as they have a top and a bottom and so must be oriented in the correct manner.  All the trusses also have to be aligned in the same direction, or the webs will not be in alignment and can cause problems when installing ductwork.  By using the open web trusses, I was able to avoid installing any bulkheads.  These normally would have been needed with dimensional lumber or I-joists for the installation of ductwork.  Without any bulkheads I was able to avoid any drops in the ceiling height.

The most common types of metal roofing are corrugated steel sheets, standing seam and roofing tiles.  The least expensive is corrugated steel roofing.  It comes in sheets that run vertically from the peak of the roof to the fascia and are overlapped and screwed down.  Standing seam roofing also runs vertically from the peak of the roof, but the sheets of metal clip together to form a tight seal and the metal is held down with concealed clips.  Standing seam can be made of different metals including steel, aluminum or copper.  Metal tiles, which can be formed to appear more like a shingle, tile or shake roof, are made of smaller sheets of metal that are made with interlocking connectors.  The metal tiles are the most expensive of the metal roofing materials as they are often made of aluminum.

The sheet steel roofing can be protected with a galvanized coating covered with a coloured polymer, or with a zinc/aluminum coating, also often covered with a coloured polymer.  The two types of coatings are not compatible and should not be used in contact, as it may result in premature corrosion of the metal.  There are also some metal roofing materials that are coated with a special coating that reflects most of the heat from the sun.

If you are interested in installing the roofing yourself, the choice is between corrugated sheets or some metal tiles.  Standing Seam roofing requires specialized equipment and is only recommended to be installed by trained contractor.  You can install metal roofing yourself but you must take more precautions than with asphalt shingles, as the metal roofing materials are usually much more slick and present a slipping hazard.  Falling off a roof is not a fun experience.  The corrugated steel sheets can be quite large and can be difficult to handle, this is not a project for one person.