Iron out the details before you pick solar

Posted Oct. 08, 2010, at 7:13 p.m.
Last modified Jan. 29, 2011, at 12:47 p.m.

Someone called me from outside of Maine today. They are building a house in northern Vermont, are going to be off the grid and want to heat the house with solar energy. No utility bills! A good idea.

They called me because they wanted to know how big a storage tank they needed to buy and asked if I would supply the pumps and heat exchangers as well as the tank. Although it was hard for me to not interrupt, I let them ask their questions. Then it was my turn.

The house is going to have radiant floors in the basement, the living space and the garage. It is going to be 3,600 square feet.

I explained that before thinking about all the specific things they asked me about, we need to get the heat load as low as possible, because it is the best way to control the cost of the heating system and make their plan workable.

I tried to explain that the first step is not to be talking about tanks and pumps, but rather to see the plans and analyze the heat loss and then work out at an integrated heating scheme.

They never heard of the concept of super-insulation. They were going to stuff some fiberglass in the walls and call it good. We sorted that out.

They were not sure what kind of radiant floor was going to be installed in the living space. There are radiant slabs in the garage and basement. The living space radiant floor was to be installed as a staple-up system. A staple-up radiant heating system has tubing stapled underneath the wood subfloor. This is insulated underneath the floor, so the heat goes through the wood subfloor into the room above. A more practical heat distribution system for them is a thin radiant slab of concrete or gypsum cement on the room side of the floor. A thin masonry floor will allow use of low grade (cooler) solar heat to keep the living space heated — if the building is well insulated.

Since they are thinking about a solar heating system, there would be a storage tank with hot water in it. If that storage hardware is in place, they also have half of a high-efficiency wood gasifier system in place. Since northern Vermont is sometimes snowy and cloudy, it makes sense to consider using wood for backup heat, especially since they do not want to use fossil fuels.

They then mentioned that this is a weekend vacation home. Since they will only be there on the weekend, the heating system can be turned down to a maintenance level, say 45 degrees, during the week, which would keep the house from freezing and will optimize the solar contribution.

The good news is that these folks are still early enough in the building stage that they can make the proper changes in the house and heating system design.

The bad news is that they only had part of a clue. Apparently there was little conversation with anyone who does heating or insulation before this point. This point being that the building is framed up and waiting for windows.

That is almost to the point of making expensive mistakes.

I have this conversation regularly with people from all over the country.

It is interesting to hear their plans and concerns. I am officially the heat storage system vendor. My de facto role winds up being that of design consultant since many of these customers are first time do-it-yourselfers or first time solar installation contractors.

It is an interesting and exciting time. Even with the slow economy, these projects continue. I suspect that a lot of what is being called the “green economy” will be conventional builders and heating contractors. As they realize this is a wonderful business opportunity, they will be part of it, and these projects will not just be specialties for the well to do.

Questions for Tom Gocze should be mailed to The Home Page, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329.

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