My initial research into low-E glass has provided some interesting knowledge. So far I have learned that there are two main types of low-E coating used on glass: soft coat and hard coat. I don't fully understand the difference between the two types but, apparently, most buildings use soft coat.

Low-E coatings reflect heat from the sun back out, while simultaneously retaining the heat that is already within the building. This helps to keep buildings warm in winter and cool in summer.

However, with my building, I actually want the sun's heat to come in, and then retain it within the building. Consequently, it appears that the hard coat low-E might work better because of its slightly different performance characteristics.

The alternative is to use triple-glazed windows made of clear (uncoated) glass. On paper it looks as thought this system might actually perform slightly better for what I want to do because the clear glass lets in the ultraviolet, visual and infrared frequencies more easily. These rays are absorbed by surfaces within the room and then reflected back at lower light and heat frequencies which are better blocked by the triple glazing.

The degree to which heat from the sun is absorb and radiated by the building is determined by its thermal mass. Certain materials, such as earth and water, have good thermal mass and can absorb large amounts of energy which they store and then release slowly back into the room.

However the ratio of thermal mass to solar heat gain (the amount of energy coming in the window) needs to be balanced quite carefully. Too little thermal mass and the material will heat up quickly and then heat the room quickly. While this is good in the short term, the material will lose its stored heat faster and the building will then cool too fast.

Conversely, too much thermal mass will absorb large amounts of solar energy without releasing it. The room will heat very slowly but will maintain its temperature for longer.

Logically therefore a balance must be found between these two states so that the room can heat up at a reasonable rate but the thermal mass can store enough energy to keep the space warm when the sun is no longer providing heat.

In addition to passive solar design a number of alternative heat sources are being researched. these include a hydronic floor system utilising solar collectors on the roof, possibly in combination with massive underground heat storage. As a final back-up, a very small and efficient wood-burning stove might be installed for days when the sun refuses to cooperate!

Although triple glazing is probably more expensive, it may be the better choice, as the low-E coatings contain numerous metals and proprietory ingredients that may not be good for the environment.

Light...
The windows will, obviously, provide the primary illumination for the building. However, areas that do not get enough light will be supplemented by a series of solar tubes in the roof.

The current generation of suntubes can, depending on their length and straightness, let close to 95% of the available sunlight into the room. Additionally, these will be fitted with internal, highly-efficient, light fixtures that can be used when daylight is unavailable.

Depending upon availability and logistics, I am hoping the building may be used to showcase a brand new lighting technology - called Electron Stimulated Luminescence (ESL) - being developed by Vu1 (Vu1.com). in Seattle. These very energy-efficient new lights produces very natural colour similar to incandescent bulbs, but without the heat of LEDs or the toxic mercury used in CFLs.

Click here to watch a short video about this exciting technology.

I also am hoping to work with the Camosun College, here in Victoria, to develop innovative low-voltage lighting and control systems for the building.