Sunday, April 29, 2007

how to heat your house without heating your planet

The Insufferable Carbon Snob went green on domestic heating decades ago...way back when Jimmy Carter and OPEC in their very different ways, stressed the importance of using less oil.
Greensmile has given you an earful of the financial and moral dimensions to heedless consumption of fossil fuels...plenty of fodder for future posts. But ICS wants you to think about the money today. Abandoning fuelish ways by switching to housing that is better insulated and uses carbon neutral heat sources is only expensive in the short term. Here is one family's response to global warming and peak oil.

If you can't afford to do the right things about energy use, you are in the wrong place.
So quit making excuses 'cause YOUR world is broken and you CAN fix it. To put this haughty bit of moralizing in the economic framework some of you might respond to: If you can't afford to do the right things about energy use now, what makes you think it is going to get easier to afford to shift to greener ways later on? You are adrift and headed for the falls. Unless the energy companies that sponsor the present US administration can be convinced that it is in their interest to do something beside move armies and earth to bring you yet more oil and coal to burn, it will be entirely up to us fat-assed consumers to make the changes.

You may find moralizing on sustainability issues tedious. Too obvious, too self-righteous, so much easier to say than to do...etc. Stow it. I have not yet begun to preach. I may slip into a hortatory tone out of habit now and then but pay it no mind. Today, just keep an eye on your checkbook. Here is one way to keep heating costs down and net carbon emissions low as well.

It took us 17 years to pay off all the mortgages. It would have been longer if the "conventional" heat sources had been used.

Building inspectors are conservative in my experience but the really dangerous discouragement comes from the lenders. They demand a conventional heat source to insure the sale of your house should you fail to make payments. If you take out a construction loan for the building phase, lenders dole the money out according to a fixed sequence of completion steps that may not match the increments of expenditure for a solar heated make up the difference.

About 25 years ago we were ready for a bigger house and could not find a contemporary we liked. We decided to build. The plans began with the idea that we should be able to get most of our heat from the sun. The first thing you do then is site the house with most of its glass facing south and with the greatest thermal mass you can accommodate. Water is superior for this purpose, having a higher specific heat than any common building material. All the better if you can swim in your heat sink once in a while:Facing due west, a view of the glass wall and 50,000 gallons of thermal mass.

To make any design work, you must do a heat budget. Being handy with software, I wrote a program that could estimate the heat lost by various designs and various choices of construction materials. It is essentially a software model of a house based on the blueprints. This allows you to know how big a heat source you will need. My numbers were in the range of 30000 BTU/hr in worst winter conditions. That means a 50000 BTU/hr wood stove will suffice.

Most tables that give a way to compare your heating options only apply to conventional construction so you will have to find one that accounts for the amount of insulation you want to put into your house. The table linked is from a Canadian source and would be appropriate for conventional housing stock, not applicable to super insulated nor to solar heating. Many of the books on designing solar heated houses that I bought were written right after the "oil shock" of 1973. Since then we went back to driving trucks to get our lattes and many of those books never saw a second edition. There are a few attractive new books reviewed at this site but the one with the best table of contents is unknown to Amazon. This book claims to have the software for figuring out if your design will work for solar heating your house but I have not read it. To name one book that I like [it has worked examples for our part of the country]: The Solar Home Book by Bruce Anderson, of which no revisions were made since 1976. The core piece of the design task is to add up the contribution to heat loading for each square foot of your house's surface based on the R-value of the walls, windows, roof etc. and figure out how much sun will come through the windows. Vertical glazing is the simplest and works better than sloped because you don't swelter in the summer. The design we have works at its best when the weather is at its coldest with snow on the deck reflecting additional heat into the house:

The romance goes out of wood heat pretty quickly. Its dirty and it always snows when you need to go out to the woodpile for another load. Its far more work and far better exercise than turning up a thermostat. So I never bought a membership at a gym. It is only when there have been two cloudy days back to back that there is any need for the stove. Here in grinding detail are formulas to compute heating costs for wood and comparisons to oil and electric heat. But the important thing is not how you heat but how much heat you keep. Before you do any other thing to reduce oil consumption, insulate your house well. With R-30 walls and an R-40 roof, just the sun alone warms the air over the pool strongly. We simply open windows between the solarium and the living quarters to let a convection current do what blowers, furnaces and duct work do in our neighbors houses. The picture below shows a pink postit suspended by a thread from the yellow thumbtack wafting in the warm current of air. That crude tell-tale is all the technology we use to control when to open or close "for solar". It is of course an utterly silent means of heating.
The bottom line for us is about $500/yr in delivered cord wood heats our 4000sq ft house where our neighbors are paying about 2000 to $2400 per season for oil depending on how big their house is. The performance of course depends on the sun but it is generally quite gratifying. Our coldest weather is dry and windy and often sunny. Winter days when it is below freezing outside and we wake to a 65 degree house, light no fire and go to bed in a 75 degree house feel like a perpetual bonus.

The carbon we put back in the air came out of the air. In that sense, wood burning is carbon neutral if you don't truck the wood from far away. I get it when building lots are being cleared in my neighborhood and split it by hand so fuel burnt to fetch fuel is at an absolute minimum. We recycle the ashes as a fertilizer ingredient in our compost and as ice-melt on the driveway.

If you own, getting insulation is money well spent. If you can remodel to put larger well insulated windows on the sunny side of your house, it can pay you back nicely. If you are smart or lucky enough to be building now that the deflating housing market has made good carpenters available, you should just say "screw resale value" and build yourself a house you will actually enjoy and feel good about.

If you just talk about global warming and blame everything on Detroit, Exxon and Bush, STFU. Demand better choices and make better choices.

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