We have recently installed a whole house fan in our NJ home. We have
central air as well, but the second floor of the house stays pretty hot
and uncomfortable after using the AC all day.
We're wondering what's the best strategy to have the second floor cool
down to a point where it is comfortable to sleep at night (Maybe 76
degrees or so).
Please keep in mind that the assumption is that the central air was on
all day, and downstairs is comfortable (73-75) and upstairs is
uncomfortable (83 or hight). Attic temp is 115 or higher.
Here are some ideas we're trying to entertain:
- Early evening, open up the windows on the second floor, run the whole
house fan while central air is on. After an hour or so, close the
windows, and let the ac do the rest.
- Early evening, open up a few windows next to the thermostat downstairs,
run the fan while ac is on. Cool air would go to the second floor and into
the attic. Warm air would replace the cool air next to the thermostat and
force it to keep the AC on which would then cool the upstairs and keep the
downstairs not too cold but comfortable.
- Any other ideas would be apreciated.
I'm not an expert here but do you have registers to "pipe" the central
air to the second floor?
The whole house fan will just move the cool air from your downstairs
right out of your house. This would be throwing money out the window.
The best method is to get the AC working properly. Be sure you have plenty
of insulation in the attic and that it is well ventilated to start with.
The sun will really heat it up as you have seen.
Be sure filters are clean and not restricting air flow, blower is operating
at the proper speed. No leaks in duct connections, return vents are working
properly and open.
Running a whole house fan with AC is going to cost a bundle. You dehumidify
the air with the AC and the fan is just going to suck in warm moist air
You don't want that.
Be sure all the vents on the second floor are open all the way in rooms you
are using, closed partially in any room of the house not being used. Close
down the first floor vents just a little and see if it forces more air
upstairs. Allow some time between adjustments to see what affect it is
Most people keep the vent registers wide open in every room. There is a
reason they are made to be adjustable, that is to balance the heating and
cooling through the house.
What is the temperature outside? If it is hotter than the inside,
which it could be until 9 or 10PM or later, you'll just make it hotter
inside to run a whole house fan.
Plus adding all that humidity, which is uncomfortable in itself and
makes it harder to cool the air.
There are not one answer fits all for your questions. However here are
a few notes:
A properly designed and installed A/C system will cool all areas of a
home properly. Yours appears it was not properly designed to start with.
Additional ducts and returns may be needed. You may need additional cooling
capacity or not.
A whole house fan can be a plus or minus. If you live where humidity
is low and the nights are cool, then using the fan as the evening cools off
can save you money and might solve your problem as well. If you live in a
humid area, like I do, it would certainly greatly increase your cooling cost
and might even reduce your overall comfort, as well as damaging fine
furniture with rapid changes in humidity.
Is it possible you don't really have a whole house fan, but rather have
a attic power vent to move the hot air out of the attic. If so it may or may
not help. Sometimes they can cause circulation problems an actually make
matters worse. Usually good static venting of the attic along with proper
insulation between the attic and the living area is best.
A HVAC professional can take measurements and do the math (Manual
calculations) to determine what you should have and compare that to what you
have. They then can make some recommendations based on those numbers and
their experience in the area.
Another possible issue is a "helper" A/C. Maybe a small window unit to
assist your central unit in those areas that need a little help. I have one
in my exercise room due to the temporary extreme loads it gets. I am
considering something similar for my bed room as a temporary fix until my
current HVAC dies and I fix the problem properly. It is getting about that
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