So I was looking over my previous power bills and noticed that heating is more power consuming than cooling months. Although August comes close. I live in Southeast Virginia and winter averages are low to mid 40's and summers average mid to upper 70s. I'm not sure of my approach for passive design. Summers are obviously brighter and less cloudy. Thus I see passive heating not working very well. I believe I could passive cool easier, except for those stagnant high humidity windless days. But since heating consumes more electricity I'm not sure how to design. For example do I need a dark roof to absorb more solar? I just don't see that working for me in the winter especially if I insulate as I plan to. I just don't see how passive can work for me...... Any ideas? I think a whole house fan could work for me on some days, but passively not sure. Please help I'm trying to design a home. It can get below freezing here and over 100 too... Anyone know where to get good house plans?? Thanks again Jay

surfh20,

We were involved with a house that a Physicist built for himself in Charlottesville, VA that was ICF and passive solar with a house fan that takes air from the attic to the lower level rooms in the winter, and from the basement up in the summer. The house does not have an hvac in it and was around 6000 sqft. I'm somewhat nearby you and do know some architects that could really help you with design if you are interested. The Physicist did much of the work himself, but he was really really smart, as most Physicists are.

Please let me know if I can help you. If you can give me an idea of how far away you are that would be nice. Let me know.

renangle

I built a Green Home in Alabama which can be 20 or 100 degrees. After looking at many ways to heat and cool it we went with Geo Thermal and solar panels. ( very small solar system) It is an ICF house and we used soy based open cell spray foam in the attic. It has worked great and the geo unit hardley ever runs do to how tight the house is. 5000 sq ft. Last months power bill was 47.84  thats including water and garbage.    

The homeowner was interested in what you were talking about but my issue was like you are saying is I could see how you could cool with it but heat with it I just do not see how it could work in regions like ours. My big question is why would you want to let your attic heat up. In the winters I just do not believe it would heat up enough to heat with and in the summers well that would just be working against you.  Maybe you could put a fan in the basement to cool with and maybe do some kind of solar blanket / heat absorber product on your roof for the winter months that is retractable. 

Shannon  

Shannon, the house is finished and the owner is very happy. The house does not have a HVAC, but it does have propane heat as back up. The fan that they put in works just as he amagined. That being said, how he imagined and how someone else may imagine can be very different.

Thanks. I just don't see how the attic could get that warm in the winter especially building a house as tight and insulated as I'm reading. The cooling makes sense to me from the basement. I live in Chesapeake and I would love help, but I'm limited by funds. Right now I'm researching my home design and trying to figure out how much home I can afford to build. I would basically be the general contractor and sub most of the work out to myself, friends and family that are in the trades. I want to go green in every aspect as I can afford, but I just pulled up a solar calculator for my current home of 1200sq ft. and it says it will cost me over $20k to offset 50%. That's a lot and I'm hoping my new home can be between 2200-2500. I do realize if I can downgrade on HVAC and other items I could save a little bit. If you can help me out at a reasonable cost I may be up for it. Thanks for your reply.

Easy renangle nobody said it would not work. That is just my opinion but in the post describing the home you left it to assume that there was no heating or cooling backups. So my thinking was that it would not be effiecient in the winter. As I thought you would have to have a backup as he has in  propane heat. 

  

ICFARXX,

After my initial post, I called to ask specifically what is in the house, as last I knew it was not complete. I was told that the house is now complete and the owner is very happy and that it has propane back up, so I wanted to amend my initail post.

With regards to surfh2o, since you are in the Chesapeake, you should be able to find qualified ICF installlers and if not I can probably help. With regard to the cost of your build, its hard to say, with you being the GC and Sub-ing to family members in the applicable trades. From what I'm seeing I can get a 6" ICF wall installed for around $11 a sqft turnkey (probably a little less) depending on location. You can downsize the HVAC and for that size of house your enegy costs will be very low. If you are the GC, you can apply for the energy efficient house tax deduction of $2000.00, you should go for the tax benefits available for windows, etc., to maximize your dollar (and become more energy efficient).

The website for energy efficient tax credits is: http://www.energystar.gov/index.cfm?c=tax_credits.tx_index

To me it is a no brainer to build with ICF. I think you will get more bang for your buck there. Building Green is going to cost you more up front but will pay off down the line. I like the way you are thinking. As far as savings for the construction of your home start with the minor details and work to the major details. You will be surprised what you can cut out with the little stuff especially DIY. I will be glad to help you as much as i can.

Shannon  

I am in the process of planning my new build. Found a architect that does passive solar designs.

http://www.sunplans.com/html/home_page.php3


I put in the specs for the house in a free heating / cooling load calculator and it said that I would be getting ~60% of heat requirement from solar.
And that's a house built in Canada. I still have to get the inputs to the estimator checked as the program is pretty complex and I might have missed something.

There a number approaches to passive solar, including greenhouse additions, trombe walls, and plain ole window glass facing south. Go to www.builditsolar.com for any number of how-tos and how-I-did-its. Windows are the most workable IMHO because you can design roof overhangs that shade them through the summer.

UCLA has two software tools that will tell you faily quickly how well passive solar will work for you:

http://www.aud.ucla.edu/energy-design-tools

Climate Consultant 4 gives you a 365-day look at your weather norm as recorded at the nearest NOAA weather station to you, typically within 50 miles. HEED lets you build a simple 3-d model of your house in its proper orientation and window placement, and runs it through 365 days of the same data that Climate Consultant uses.

EnergyPlus is a govt simulation tool that is more sophisticated than HEED but more difficult to use.

Go here for a complete list of energy design tools: http://apps1.eere.energy.gov/buildings/tools_directory/subjects_sub.cfm

I suspect you will have plenty of solar energy in the winter in southeast Va. I'm guessing that high thermal mass will take care of cooling requirements much of the time. Putting lots of mass, typically concrete, inside the insulated envelope turns it into a thermal flywheel, splitting the difference between daytime heat and nighttime cool. I should note here that the mass must be exposed to the interior, which rules out traditional ICF construction. Climate Consultant produces a psychrometric chart that will show you how many hours in a year that specific energy strategies will result in comfortable conditions, considering temperature and humidity. Passive solar high mass should work for you.

Finally, for house plans, why not borrow (steal?) from the best? Frank Lloyd Wright designed about 100 ordinary sized homes, dubbed Usonian houses, in a quest to bring architecture to the masses. Most of them were passive solar, high mass designs. My house is based loosely on this Wright creation: http://www.peterbeers.net/interests/flw_rt/Ohio/Penfield/Penfield.htm

Passive solar design is something I have been doing for 30 years and building with for 25 years. Many of the steps to make passive solar design work are fairly simple and well know. Like: proper orientation, exposure, latitude, climate, heating and cooling loads for regional design, shading/overhangs, insulation, thermal mass, ratio of window to sq/ft, and the most important elements are the windows. Windows are the things that make passive solar design work and typical windows won't do, especially energy star rated windows. What you want is a window that has a high solar heat gain, shown at the SHGC on the window rating sticker. Then you need to adeqately shade this to stop overheating during the cooling months. Proper amounts of thermal mass to store the solar energy. I have been working with an inventor that has developed a window that contains thermal mass in the window, along with an integral shading system. While I have had the opportunity to use his two previous versions of his designs, his latest design will be featured on the BAC/Tufts solar decathlon entry. http://www.solardecathlon.org/ http://www.livecurio.us/
He is still refining it and is still a year or so from production. I personally like the look of the previous system which I used in a home here in MA. I did a whole series of videos about this window system including the latest one showing the solar shades being added. all of these are posted on my you tube page, http://www.youtube.com/user/eebuilder These windows maintained this unheated house through most of this last winter. The average indoor temperature was around 50-55degrees for most of the winter with outside temps dipping into the 20's and highs in the 30-40 degree range. This made the heating system for the house that much smaller and for a different climate made produce more of a percentage of the heating costs.

Shading is something that can also be done through proper placement of trees and plants that shade the home during the summer months but lose their leaves and allow for solar access during the winter months.
The use of a solar chimney can be used to help cool the house during the summer months without much need for mechanical ventilation. I believe that to be a truly passive solar home you also need to employ efficiency into the envelope system that far exceeds the normal levels required by code. At some point super insulating become less cost effective but a minumun level of R-30 for the walls and R-50 for the ceiling should be used. Some would suggest that higher levels are better but the cost benefit is reduced above these levels. Yes there are several methods of energy modeling that attempt to predict the energy usage, it is like any other computer program, (garbage in garbage out). While I do use several different modeling programs to help predict energy usage, I then compare it to the acctual energy costs. Here in MA I can reduce your heating costs by as much as 60-70% through the use of passive solar design, windows, thermal mass, and orientation. Do you know what your heating degree days are? How is you home oriented? Do you know what your solar declination is at you location? probably around 10 degrees west.

The simple answer is yes solar heating can be done in almost any climate that has sun during the winter however limited it may be.

Tom Pittsley
[email protected]
www.eebt.org