excellent information here Dale and thanks for sharing. I picked up
one other new bit of thought. and that was setting the furnace fan
to run more often or steady. that came up in a conversatin as I am
considering in the future of replacing our near 21 year old Hot air
Ng furnace. one of the choices was a 2 stage fan system. either way
this is good information. thankws.Lee
On Wed, Jan 30, 2008 at
10:15:06PM -0500, Dale Leavens wrote:
> Setback Thermostats | CMHCThis is some information I found at Canadian
> Mortgage and Housing.
>
> Hope it is helpful.
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> Consumers > Maintaining a Home > Energy Efficiency and Cost Savings >
> Setback Thermostats
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> The following fact sheet is part of the About Your House
> ??? General Series
>
>
>
>
> Setback Thermostats
> What is a Setback Thermostat?
> Thermostats control heating and cooling appliances in
> houses. A setback thermostat gives the user the option of changing the
> temperature setting automatically during the nights and during the work day
> when the occupants have left the house. A setback thermostat can help reduce
> overall household energy consumption.
>
> A conventional thermostat simply regulates house heating at
> one temperature. For instance, in the winter, if you set the thermostat to
> 20°C (68°F), it will activate the heating system when the house temperature
> drops below 20°C and will shut the system off when the house air warms up
> past 20°C.
>
> A setback thermostat contains an electronic clock. It can
> automatically turn down the temperature setting at night, when you are
> asleep, or midday, when you are at work. It can also return the temperature
> to a more comfortable level before you wake up or arrive home from work. That
> way you can have the energy savings of a lowered thermostat setting without
> the discomfort of having to wait for the house to heat up again.
>
> The setback thermostat can also be used as a set-forward
> thermostat for an air conditioning system. It can allow the house to heat up
> when it is unoccupied and return it to comfortable temperatures before you
> return from daytime activities.
>
> Although this About Your House deals with setback
> thermostats and forced-air heating systems generally, you can apply some of
> the advice to electric baseboards or to summer usage.
>
> You can use a standard thermostat to set your house
> temperatures lower during times when the house is unoccupied. This will lead
> to similar energy savings as with a setback thermostat but not the
> convenience.
>
> What is a Normal House Temperature?
> CMHC has randomly surveyed Canadian houses. Thermostat
> settings in winter tend to be quite closely grouped around 20°C ??? 21°C
> (68°F ??? 70°F). Summer temperatures range much more widely, depending upon
> whether the house has air conditioning.
>
> To What Temperature Should I Set Back the Thermostat?
> The more you reduce the thermostat setting, the greater the
> possibility for savings. Generally, a drop of two degrees will lead to some
> savings and little risk. Some householders reduce temperatures four to six
> degrees. However, temperature differences this large create potential comfort
> and moisture problems that are discussed below.
>
> Does Setting Back the Temperature Save Energy?
> Yes. Research from the Canadian Centre for Housing
> Technology, shows that winter setbacks for the houses tested would result in
> heating costs savings of five to fifteen per cent. The highest savings came
> with a setback of six degrees.
>
> Savings for summer were about the same, although simply
> raising the thermostat set point in summer from 22°C (71°F) to 24°C (75°F)
> led to more significant savings than the set-forward strategy and offers
> better indoor humidity control.
>
> Note that these savings are for two airtight,
> well-insulated, unoccupied houses. The savings in your home may vary, but are
> likely to be in the same range.
>
> What Can Go Wrong?
> There are several potential problems.
>
> The first one is comfort. A cool house can be uncomfortable
> in the winter. If you wake up at night before the time the thermostat resets
> to 20°C or 22°C, the rooms will be cooler. The same applies if you have a
> setback daily when you leave for work, but you return home earlier.
>
> A setback schedule works best for people with predictable
> work and sleep periods. If your schedule is completely irregular, you might
> as well simply turn down a conventional thermostat when you sleep or leave
> the house, rather than trying to anticipate it with a setback thermostat.
>
> A second problem is the possibility of high humidity in the
> winter.
>
> Cool air can hold less moisture than warm air, so the
> relative humidity (RH) rises as the air cools. For instance, house air at a
> reasonable 35 per cent RH at 22°C will see an increase to 50 per cent RH when
> the same air is allowed to cool to 16°C
> (6°F). This can lead to condensation on windows and walls
> (for instance, in closets or behind furniture).
>
> Basically, you are creating a more humid environment, all
> things considered, when you allow the house temperature to drop
> significantly. This may not be a problem in a dry house or one where you can
> modify the humidity, for instance by turning off a humidifier. The house
> humidity should be monitored, especially in winter. For more information on
> how to measure humidity in houses, go to Measuring Humidity in Your Home.
>
> Window condensation will be the first place that you notice
> excessive house humidity. Blinds and curtains usually increase the occurrence
> of condensation. If condensation is taking place, make sure that you wipe it
> up diligently or raise the temperature setback (eg. from 16°C to 17°C) until
> you have lowered house humidity levels and condensation is no longer a
> problem.
>
> A third potential problem is a sustained lack of air
> circulation as the house cools down.
>
> If you set back your thermostat in the evening from 20°C to
> 16°C, the house may not cool to 16°C until 5 a.m. During that time, there
> will be no furnace circulation fan operation, unless you set the fan to run
> it continuously. For houses where bedroom doors are kept closed, this could
> lead to stuffiness in those rooms and a lack of fresh air.
>
> There are ventilation devices and furnace fan cycling
> controls that can compensate for this, if you find bedrooms and other rooms
> underventilated during setback periods. Setting back to a higher temperature,
> such as 18°C (64°F), will reduce the period of furnace inactivity (and your
> consequent savings). Setting the furnace fan to run continuously will help
> but this will increase electricity consumption.
>
> The final potential problem with setback thermostats is the
> time required to regain temperature, or to heat the house up once more.
>
> An oversized furnace will return the house to the higher
> temperature quickly, but a properly sized furnace can take a long time ??? as
> much as one hour ??? to bring the house back to a comfortable temperature.
> You have to experiment with this as it will depend on the type and relative
> size of your heating equipment and your home???s energy efficiency and other
> factors.
>
> If it takes an unacceptably long time for your house to
> heat up again, consider a smaller setback or start the high temperature
> setting earlier so that it is comfortable for you when you get out of bed or
> return from work.
>
> Related to this problem is the length of time required for
> the room enclosure and furnishings to heat up. If your bathroom has cooled to
> 16°C overnight and the furnace has kicked in at 6 a.m. to bring up the heat,
> your bathroom walls will still be cool when you start a shower at 7 a.m.
> Testing in the research house at the Canadian Centre for Housing Technology
> house showed that it takes up to several hours for wall temperatures to
> return to their highest temperature. Cool wall surface temperatures can lead
> to comfort and condensation problems.
>
> What Houses Have the Greatest Risk for Problems?
> Many houses will not see significant problems with the use
> of setback thermostats, but there will be some houses more at risk.
>
> If you have a house with moisture problems in winter (mold,
> condensation on windows, and so on), get those problems fixed before you
> consider installing a setback thermostat or set back your conventional
> thermostat.
>
> If you have a forced-air furnace and closed bedroom doors,
> you will need to ensure adequate ventilation of bedrooms at night, one way or
> another. If you already keep your house at an unusually low temperature (such
> as 18°C), then a temperature setback is more apt to get you into the high
> humidity danger zone. If you are the sort of person who has difficulty
> operating a VCR or DVD player, you will find many electronic thermostats
> confusing, especially when compared to the simplicity of an older dial
> thermostat.
>
> So, How Do You Set These Things Anyhow?
> Check your manual or ask a teenager to do it. We can???t
> help you with this. Each system is different.
>
> All These Problems ??? Is It Worth the Trouble?
> Yes, it can be worth the trouble. If your house is in good
> condition, if you do not have excessive moisture problems, if you have a
> fairly regular schedule, then by all means use a setback thermostat. It will
> save energy. Just be aware that all energy-saving activities can have
> unexpected results, such as those outlined in this article and be sure to
> take steps to avoid these problems.
>
>
>
> Related Links
>
> a.. Measuring Humidity in Your Home
> b.. Replacing Your Furnace
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