Windows and zero energy challenge

I am learning a lot about windows, not the computer kind, but the house kind.  The one feature that I have to pay attention to for the south side windows is the solar heat gain coefficient (shgc).  The shgc rating ranges from 1.0 down.  A rating of one means clear glass and 100% of solar heat going through.  The lower the number, the less solar heat.  Unfortunately, the higher the number, generally the more heat leaks out also.  So most windows today have a low shgc.  Ones that I specced out had a .29-.35 shgc.  This mean only 29 to 35 percent of the solar energy is getting through.  This is much too low.  So far, and quite frankly I haven't started to seriously look, the highest shgc stock window I have found is .45,  still to low.  I am looking for .60 and above.

With these high shgc windows come two complications.  The first is the heat loss factor.  It is pointless to try to heat the house passively if much of my heat is going to leave through the windows.  Therefore I need to have insulated shades that I can pull down at night to minimize heat loss, or get those windows that have them internally installed. 

The second issue, which segues into the second topic in this post, is the zero energy challenge.  I have decided (from advice given to me from Peter Harding our energy consultant), to enter the house in the Connecticut zero energy challenge.  This is a contest for new constructions, with a grand prize of 10,000 dollars to the most energy efficient house.  A link with all the details is here:   http://www.ctzeroenergychallenge.com/about.htm

As far as I can tell from the existing contestants, I am the only contestant who is doing his own general contracting.  Every other contestant is a building company.

Excavation -silt fence construction to start Monday!
Wish me luck, and

Thanks for reading.

Sam

Passive solar design

So, what is a passive solar designed house?  There are several ways of building the passive solar part.

The picture on the left shows the basics-

• There needs to be an aperture, or the way the sun gets in. (The windows). Designers need to be careful in regards to the amount and placement of the windows.  Too many windows and the house warms up to much cools down to quickly.
• The absorber- this is the material that absorbs the sunlight and stores it as heat.  This is normally masonary, concrete, sometimes even water.
• The thermal mass.  The material that is behind the absorber and stores and helps distribute the heat.  The thermal mass is often the same as the absorber except that it is mass that holds the majority of the heat.  To little mass and the house heats up too quickly, and cools too rapidly, creating uncomfortable temperature spikes  More is better in this case and helps an even flow of the-
• distribution.  How the heat is distributed is an important aspect of the passive solar home.  Most use conduction, convection, and radiation to distribute the heat which is totally natural, requiring no equipment.  Sometimes, however, fans and ducts are used to distribute the heat.
• Control of the amount of intake and escape.  There certainly can be too much of a good thing and the designer needs to keep in mind the summer sun as well as the winter.  In the picture you can see that the designer extended the eaves out, partially blocking the sun in the summer months. Also, the amount of windows are a two edged sword, as mentioned above.  Not only can too many windows let in too much sunlight, at night too many windows tend to allow the heat to escape too easily.  A careful balance needs to be maintained.

So, during the day the sun enters through the aperture, hits the absorber and heats up the thermal mass.  When the sun goes down, the house begins to cool, the thermal mass starts to release it's heat and helps keep a constant temperature through out the house.
There are several different ways to approach designing a passive solar home, some of which I will detail later. To be honest, Teri and I started with the idea of passive solar as the main idea around the philosophy of our house, but are moving closer to the geothermal portion- due mostly to our New England setting.  I still hope, however, that the passive solar portion is a significant part of our supplementary heating.

I noticed over one hundred hits on this blog already-  Thanks for reading!

some explanation

Several people have asked me about the site plan that I posted. Specifically, why we were orienting the house the way we are.  First, nothing is written in stone, the tentative placement is just that, but there are several reasons for that particular placement. 

1. The western part of the property is very swampy, in fact wetlands.  We are waiting on the wetlands part of the survey as I write.  This will tell us where exactly we can and can not build.  
2. We want a large "back" yard.  If we place the house more centrally, we won't have any one particular big yard.
3.  We want to use geothermal energy for our heating and AC.  This will require that we dig two, possibly more wells in preparation.  While I'm not sure yet how much room that will take, I think that western portion will be enough.
4. Lastly, we are supplementing our heat with a passive solar design.  This requires that the house faces within 30 degrees of true north.  The way the house is oriented in the site plans is very close to north.

We are still talking about the orientation of the house, for privacy, view, and praticality.  I will continue to update on that front.