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Heating and Cooling Systems
#1 PASSIVE SOLAR HEATING AND COOLING
You can dramatically reduce energy use by taking advantage of the following free techniques to use sun, shade, and natural heating and cooling to your advantage for home comfort.
- During the winter, close drapes and blinds during dark, cold periods to act as insulation. During direct sunlight in cold weather open the drapes but not the windows to enhance solar heat gain. This will hold warmth in your house, making your furnace or boiler not have to work as hard.
- During the summer, open your windows and shades at night to allow cool night air in. You could add a fan blowing into the house in front of the open window to increase the flow of cool air. During a summer day, close the windows and keep the shades down to prevent hot daytime air and sunlight from entering your home and building up excess heat. If it is still too hot, the next strategy is to keep the shades down during the day but open the windows and situate a fan so that it is blowing air out of the house. Because of its energy intensity, reserve use of air conditioning for very hot weather when these other methods do not work. If you do turn on air conditioning keep the windows closed but use the shades as described above.
- Trees and shrubs that provide shade to your home and windows that can be a major cost savings for energy systems and air conditioning units (probably a rare and long-term investment). Deciduous trees that lose their leaves in the winter are best to place on the south an east sides so you can still get sunlight to warm your home in the winter.
- Conifer trees (that have leaves all year round) are best placed on the north and west side of homes to block cold winds during the winter which helps to insulate the home and save energy. (again, if you have a chance to add them).
- Black roofs absorb a disproportionate amount of sunlight, causing homes to heat up, resulting in unnecessary stress on air conditioning system. White roofs (involving either plastic liners or painted coverings) or green roofs (involving soil and small plants) reduce building temperature in the summer and help save energy and increase comfort. It is important for you to have assessments done on the structure and needs of your home before taking either of these two roofing steps. Solar power will also serve the same energy saving function by converting this sunlight into useful energy instead of heat.
#2 HEATING EFFICIENTLY
If you have control of your own heating system, there are many simple and low-cost things you can do to save energy by operating your furnace or boiler efficiently:
- Setting your thermostat just a few degrees lower will save a disproportionate amount of energy relative to what would be expected. In fact the greatest degree of energy is spent warming your house the last few marginal degrees. A good rule of thumb for your home is that every degree you turn your heat down while above 60 degrees will save about 3% on your heating costs. That equals to 6% for just 2 degrees and 15% for 5 degrees.
- Change your filter on a regular basis if applicable to your type of furnace. If your filter is clogged with dirt then your furnace will have to work harder than it needs to. This will use more energy, wearing the system down, and also risk overheating. Standard filters should be changed monthly during the heating season. There are more advanced furnace filters can be changed only once for each new heating season. There are also other types of advanced furnace filters that need only periodic cleaning, but not actual replacement.
- Install and program a programmable thermostat that allows you to set what
temperature you want your home to be at what time. Set the thermostat for lower
temperatures at night time and when you will be out of the house while reserving
more comfortable temperatures when you will be awake and present around the
house. The Community Energy Services program will install a programmable
thermostat if you do not already have one and can help you program it if you do. - If you have hot water radiators, place reflective panels behind them to radiate heat into the room instead of heating the wall. Make sure to bleed the extra air and steam out of your radiators so that they heat more efficiently.
If your existing furnace or boiler is at the end of its life, or you are looking to replace it, there are highly energy efficient models (90-95% efficient as opposed to a standard model that is around 75%). Though it may cost a bit more upfront, the major savings it will create over time makes the purchase worthwhile. Gas condensing models with variable fans are a characteristic that is superior to a standard model.
Traditionally, installers oversize heating systems to ensure that they can meet the desired amount of heating on even the very coldest days – this means they are running inefficiently most of the time. Consider if you are okay with having an occasional slightly chilly day when the outdoors is particularly frigid in return for lower energy costs year-round – if so, get a slightly smaller unit after talking with your installer. You should also consider switching to renewable heating and cooling sources to almost entirely reduce your need for fossil fuel heat.
#3 AIR CONDITIONING
Before you turn on the AC, make sure you have maxed out the strategies for passive
heating and cooling defined above. Keep your AC off whenever you can – in moderately
warm weather, at night or when you’re not at home – it is much more expensive to cool
with AC than fans and natural air flow.
Here are the basic principles for using air conditioning efficiently are similar but inverse to those as for heating:
- Lowering the temperature the last few marginal degrees on the temperature controls cost proportionately a great amount. Turn the temperature up a few degrees – cooling to 78 is significantly less costly than cooling to 75, which is much less costly than cooling to 70.
- Keep your AC grills and filters clear of dust that would otherwise make the AC unit have to work much harder than it needs to. For many central AC units, the filter for the AC and the furnace is the same.
- Use your programmable thermostat the same way – have the AC scheduled to turn off when no one is home and set it for a comfortable temperature when people return.
If your air conditioner is at the end of its life, or you are looking to replace it, get a highly energy efficient model as indicated by its Seasonal Energy Efficiency Ratio (SEER). The current minimum legally allowed SEER rating for newly installed AC’s is 13 but they go as high as 23. While models with the higher ratings may cost a bit more upfront, the major energy savings it allows over time will make the purchase worthwhile.
Traditionally, installers tend to oversize air conditioning systems to ensure that they can meet the desired amount of cooling on even the very hottest days. In this case it means they are running inefficiently most of the time. Consider if you are okay with having an occasional slightly too warm day in return for lower energy costs in the long term. If so, it is good to get a slightly smaller unit after consulting with your installer. You should also consider switching to renewable heating and cooling sources to almost entirely displacing your need for fossil fuel powered heating and cooling.
#4 HUMIDITY LEVEL ADJUSTMENT
Humidity levels have a strong influence on both home comfort and overall energy use. A humidifier connected to your furnace/boiler and a central AC uses slightly more electricity but saves substantially on heating and cooling by allowing your home to be more comfortable at either lower winter air temperatures or higher summer air temperatures. The overall rule of thumb is to humidify in the winter dehumidify in the summer.
Here is a chart from the website of a builder Tim Carter:
Outside temp Relative humidity
20 35%
10 30%
0 25%
-10 20%
-25 15%
Exhaust fans in bathrooms also reduce humidity, so it is more important to use them in the summer than in the winter.
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