Solar orientation
In Northern United States, the Ideal orientation of a home is to have the side with the most window area exposed in a south-south west direction. This ideal assumes that the area is adequately protected from winds out of the west, whether by trees or the lands topography. If the home is not protected from westerly winds, then south facing homes are the ideal. There are three main considerations for passive solar heating, when building a home, they are orientation, solar security and surface finish.
Orientating a home with a south-south-west exposure, you can expect solar gains during the winter of up to 550 Btu per quadrilateral foot of area from your southward facing windows during the peak sunlight hours (about 1:00pm to 3:00pm). However, you still need to protect yourself from this hot sun during the summer months when heat gains of over 1500 Btu per hour are possible.
Designers tend to use one, or both of the following solar security methods. First, by planting deciduous shade trees within about 20' of the south wall of the home, which will fill in with leaves during the summer and block the sun, while shedding the leaves in the winter permitting sunlight to enter into south facing windows. The second method is to utilize a roof overhang or eave. This overhang, as a rule of thumb, should be about 2.5 times less, in width, than the total height of the window, together with the header (beam over the window opening), for which it is overhanging. This will give abundance of shade security during the summer months when the sun arcs higher in the sky, than in the winter, when the arc of the sun is much closer to the horizon.
The surface close will also have an impact on the quality of the building to discharge or withhold heat. Although minimal, you should try to stick with a rough surfaced siding or brick, which is of a darker color. This will allow your surface walls to soak up as much of the suns radiation instead of reflecting it, raising its climatic characteristic enough to help slow the rate of heat replacement through the walls. Interior finishes should be flat and lightly colored, to reflect radiant heat back into the room as much as possible. Avoid flat paints if possible. This is also true for the roof assembly with the use of darker shingles and light colored, flat interior ceilings.
And if you want to take solar gain to an extreme, you could also think shaping the profile of the land on the south side of your home, into a cup shaped reflector, so that the reflected solar rays, bouncing of the winter snows surface, integrate into the southern exposed windows.
Air and Vapor Barriers
We utilize two types of membrane barriers in contemporary construction, the air wall and the Vapor barrier.
The air wall is located on the surface side of all wall assemblies that are constructed of wood. Attics, as of yet, do not need the use of one. This includes the outer side of strapped basement walls and the underside of floor joists in homes built on piers. It has two main functions. Primarily it acts to forestall the tube of free water from the surface side of the insulated cavity into the wall or floor assembly, which would cause structural wood, rot, and saturate the insulation. But at the same time, the wall allows water, in the form of vapor, which would otherwise remain trapped in the wall cavity, to escape to the outside, thereby reducing moisture attention within the wall components. A secondary purpose of the air wall is to forestall the tube of air, through wind or differential pressure, which would disperse the heat trapped in the air pockets of batt insulation much more rapidly. The air wall also helps to add to the thermal resistance of the building, by as much as R-2.
The vapor wall is installed on the interior side of insulation, and is used to slow the tube of water, in the form of vapor, entering into insulated spaces. This vapor, in turn condenses in the insulation or on structural members, saturating the insulation and rotting wood components. The vapor wall is applied to the interior side of the building and is almost always installed as a polyethylene sheet (clear plastic sheets), which come in rolls 9' wide and stapled in place. The joints between sheets are treated with acoustical sealant or 2 stud overlaps to ensure a continuous seal. The tighter the vapor wall is sealed the better, so it's a good idea to pay special attention to all joints, and any penetrations or holes.
One thing you may want to think is the application of non-porous paints (oil based) to the interior finishes, as these accomplish much in the same way as vapor barriers, and add to their effectiveness. Caulking and sealing the finishes at the joints, such as floors and ceilings, prior to application of the interior trimwork, also adds to the uncut effectiveness of the painted barrier. On a final note, I would not recommend the use of surface sheathing materials such as plywood's or aspenite. These materials effectively act as a vapor wall on the outer wall surface, and traps moisture passing through the interior vapor barrier, within the wall cavity, where it condenses and rots structural components.
There are three main materials used as air barriers, they contain saturated building papers, extruded foamboard, and a new goods made of spun glass paper.
Saturated building papers are basically paper, which is impregnated or saturated with tar, or a similar substance, development it water-resistant. It generally comes in three or four foot wide rolls, which is stapled with a horizontal 6"-12" overlap. Of the three types, this is the cheapest and probably the oldest means of applying surface air barriers.
Extruded foamboard is an ideal material as it can be applied as both insulation as well as acting as an air barrier. Care must be taken in this approach, for all the joints need to be sealed with vapor tape, which is quite expensive, although easy to apply.
Spun glass fiber sheets are a relatively new building material (often referred to as "sheathing paper"). It is primarily manufactured from glass that is spun, combined with other materials, then pressed to form a paper like continuous sheet. This type of wall generally comes in a roll 9' wide and is quite verily applied.
Insulation
Insulation works by trapping air in pockets, which slows the rate of heat replacement through the allowance of conducted and convected losses. The use of reflective materials such as foils or smooth, light colored surfaces also slow radiant heat losses. It is leading to remember that we can only slow the rate of loss, not eliminate it all together. Manufactures generally measures the quality of materials to slow heat loss by referring to the "R-value" or resistance value of materials. There are practical limits to insulating, and a good make takes into list the payback time that balances the cost of building with total power savings. A good guideline to supervene is to collate the uncut cost of adding the insulation, which would contain the higher cost of wider structural components (for example 2x8 wall building instead of 2x6) against the length of time you expect to be living in the home. As well you should think the projected rise in cost of the fuel used by your heating sources.
There are three main types of insulation available on the market today. They are spun glass fibers, rock wool, polystyrene and ureaformaldehyde.
Spun glass fibers are most generally produced in whether batt or crushed fiber type for installing in homes. Batt insulation is glass that is spun into threads and woven into a thick mat of fibers of varying thickness with an approximate R-value of 3.2 per inch of thickness. Crushed fiber insulation is basically the same as batt insulation, but it is crushed at the plant and separated for insulating in horizontal locations such as ceiling or floor assemblies. It can be located whether by blowing the crushed fibers through piping using mechanical equipment, or pouring it out of bags, then spreading with a pitchfork or similar tool. Blown glass fiber insulation provides an median R-value of about 2.6, while pouring and spreading is a slightly higher thermal resistance of R-3.1.
Rock wool is similar to glass fibrous insulation, except it is manufactured from rock, instead of glass. It comes in both batt-type and crushed fibers, with batt insulation contribution higher R-values than glass of 3.6, blown values of R-2.9 and poured placement totaling R-3.2.
Expanded polystyrene is one of the best insulation's available, but also one of the more expensive. It comes in three main types; Extruded polystyrene, wide polystyrene and polyurethane or ureaformaldehyde foam. These types of insulation are ideal for areas where they will be exposed to wet conditions such as basement foundations, for they declare insulative values even when immersed in water. As well, wide polystyrene can be used effectively for an surface air barrier, required by codes in Canada, so long as the joints are sealed with thorough vapor tape.
Extruded polystyrene (often referred to as "foamboard" or by the tradename "Styrofoam") is generally blue or pink in color. It is manufactured by pushing freshly wide foam through a mold, in supervene extruding it through a template, or by injecting the polystyrene into personel molds. generally the edges are designed to interlock to ensure a continuous thermal break, and help to seal the joints between the panels. They are manufactured mostly in 2'x8' sheets and offer very high Resistance values of about R-4.7 per inch of thickness.
Expanded polystyrene (sometimes referred to as "beadboard" or "cut cell polystyrene), is economy than extruded foamboard and is generally white in color. It is manufactured from billets or chunks of wide foam, which is then cut into slabs of varying thickness, most often without the interlocking joints like the extruded polystyrene. This type of wide foamboard is most often manufactured in 4'x8' sheets of varying thickness'. Unfortunately, beadboard lacks the high resistance values of extruded polystyrene, with an median R-value of only 3.6.
The most expensive of the foam insulation's is the ureaformaldehyde or polyurethane foams which are located by injecting or spraying chemically addition foam into cavities or over surfaces. This type of foam has seen a lot of controversy over both its off gassing of chemicals into the buildings, ands its lack of consistency in placement. It does, any way offer the highest R-value available for foamed insulation, which is only slightly higher than extruded polystyrene with a resistance of R-4.8.
Insulation And Designing To sacrifice Heat Loss
