Category Archives: building design

Net zero in New England seems easy now…

Net zero in new england seems easy to me now… and here’s a little about why…

First some qualifications:
- I am talking about new construction since that is what I am familiar with.
- By easy I mean “not that expensive” by which I mean, it is doable for the same (net cash flow) as a typical new house.

The reason it seems easy is because we seem pretty close to on target to be net zero for the year, and we don’t even have:
- solar hot water heating
- and more importantly… solar air heating
- the house isn’t all that small. I mean, it’s smaller than a typical new house with 4 people living in it, but in retrospect, I think a different design might have been more efficient. I will talk more about that in the future.*

Solar Air Heating
What I realize now, more than ever, is that it is not difficult or expensive to design an inexpensive solar air heater for a house that gives 100% of your heating on a sunny day, even if it is 0F outside. That’s because you don’t need all that much (even in New England) if you have insulated enough. The method that I am most interested in at the moment is Aluminum Downspout Hot Air Solar Collector–which is quite unobtrusive… (youtube) Read more here at

You want in?
1. calculate how large a collector one would need, you need to first estimate your house’s “heat load” using PHPP (if you are building a new Passive House) or get a pretty good estimate using this form or the excel file here as an example.
2. build it! With your kids!

Here’s what I would do if I were to do it again:
- double stud walls 12″ with dense packed cellulose by an installer who knows what they are doing and has the right equipment
- air barrier at the exterior — taped Zip system walls perhaps. Meaning… applied eaves. Search on Marc Rosenbaum applied eaves, etc.
- ventilated/cold roof with insulation on attic floor, no ceiling cans on 2nd floor, etc. and a hatch on exterior of the house to access this space if need be.
- Don’t worry about the roof angle being 45 degrees (near your latitude) or being exactly solar south. Maybe even a shed roof so there is even MORE roof for solar panels.
- heat with a wood stove or pellet stove, looking to Rachel Wagner for any advice on best practices for heating with wood in a tight house
- Use an HRV
- I like having a basement to put mechanicals in, but if I were to do it again, I would probably build only 2 bigger above ground floors and keep the attic level outside the envelope. For a number of reasons. I will write more on this in the future.

Basically, I would follow the rules of building a superinsulated house, even Passive House, but not go too crazy with expensive closed-cell** spray foam insulation or very expensive windows. Pretty much what we did, but I would try to spend even less, and if anything, spend the difference on solar heating!

What’s my point?
The point is… even in a superinsulated house, heating is a big part of the overall energy use (if looking at heating, cooling, hot-water heating, cooking, lighting and appliance use in a household that is reasonably considerate of their usage.) So if you can cut this, even by 25% due to solar, you are going to be in much better shape. Some will argue that is better to spend solar dollars on PVs that can be used year-round, but in cold climates with very efficient solar-thermal heating done on the cheap with the help of and “simplysolar” and “solarheat” yahoo group participants, the cost per KWh of energy saved is going to be much lower.

*A neat book on small houses is Little House on a Small Planet: Simple Homes, Cozy Retreats, and Energy Efficient Possibilities

**Some closed-cell foam is still going to be useful in certain spots — like the rim joists. Just be sure to use a brand with water as the blowing agent so you aren’t adding to the greenhouse effect due to HFC-134a. (article discussing foam insulation and GWP)

Leave a comment

Filed under building design, building science, energy, erik-green, futuresafe, heating with wood, passive house, solar, superinsulation, zero energy home