Entries from June 2008
Author’s note: the following article on home heating is the sixth in an eight-part series.
Metal woodstoves are a significant improvement over open fireplaces from the standpoint of producing more usable heat. They limit incoming air, thus avoiding heating air not needed for combustion. Another improvement: they use a lengthened heat exchange pathway to improve heat transfer from the heated combustion gases before they exit the chimney.
Unfortunately, metal woodstoves must operate at low, inefficient, and polluting combustion temperatures. Why? Because wood combustion requires high temperatures to be clean and efficient. Wood burns starts to burn cleanly at around 1200 degrees Fahrenheit, with continuous improvement up to about 2000 degrees. Cast iron begins to glow red and fail at about 1200 degrees. See the problem?
[Read more →]
Author’s note: the following article on home heating is the fifth in an eight-part series.
Open fireplaces have a reputation for polluting air. Actually, a fireplace, when burned hot and fast, creates very little pollution. The trouble is, a hot fire in a fireplace sometimes yields less heat than a smoldering fire. Where does the heat go?
The optimal amount of combustion air contains just enough oxygen to burn all combustible gases liberated by the heat. Any additional air grabs heat and sends it up the chimney. Under some circumstances, fireplaces can so far exceed this air-to-fuel ratio that they suck more heat out of a house than they radiate back into it. The fire actually makes the house colder!
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Author’s note: the following article on home heating is the fourth in an eight-part series.
The previous article discussed the disadvantages of using forced air to heat your house. Another approach is, literally, to heat your house –- not the air cycling through it. Why would you want to do this?
Well, for one, when you heat the building itself, you can open all the doors and windows, let all the warm air escape, close everything back up, and, instantly, be warm again – without having to add more heat.
The Empty Fridge
Warm masses heat you like the sun does: by sending you radiant heat. As I explained in Heating Your Home: Heat 101, heating and cooling differ only in perspective. If you can get your head around that, then the Empty Refrigerator Effect explains why heating air is an inefficient way to heat a home.
Like it says in the fine print, refrigerators achieve their rated efficiencies only when they’re full. Every time you open the door, warm air enters. If the fridge is empty, the inside temperature may go up five or ten degrees. [Read more →]
Author’s note: the following article on home heating is the third in an eight-part series. This article addresses climate conditions found in the San Francisco Bay Area, but may have applicability elsewhere.
Forced air systems are the most common heating systems in California and are used in most new construction elsewhere. They have two big advantages: they are cheap to install, and they provide heat at a moment’s notice. Having “instant-on” heat is vital for intermittent use spaces like ski cabins. Otherwise, forced air is the least energy efficient and least comfortable way of heating a typical home. Why?
Ventilation and Heat Loss
For the health and well-being of its occupants, a home must exhaust stale air and refresh it with new air drawn from outdoors. Forced air systems heat and blow this air, via ducts, throughout your house. Since new air is continually entering and leaving, you are heating the outdoors. [Read more →]
Author’s note: the following article on home heating is the first in an eight-part series. The series specifically targets climate found in the San Francisco Bay Area, but has applicability elsewhere.
According to the U.S. Department of Energy, heating and cooling amounts to 46% of all energy consumed by our homes. Water heating uses another 14%. In coastal California, where extreme heat is rare and winters are mild, a properly sited, well designed passive solar home can generate its own heat and hot water, and do without air conditioning.
Historically, few homes are so well sited or built. Since our area has more heating days than cooling days, most homeowners need a heating system. What few know is that many indoor air quality problems can be by-products of forced air heating, ventilation and air-conditioning (HVAC) systems installed in their homes. [Read more →]
