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Are there cooling benefits for installing an exhaust fan in a false ceiling?

Hello,

I so wanted an energy efficient home. I specified that when we began the remodel. All of the new windows are energy efficient, as are all of the appliances, and I am thankful for that.

But to my disgust, the insulation that I requested for my remodel was not installed and the walls are up. My home is a penthouse in a 1970s brick building in Barcelona. It is on the 9th floor, and has no common walls. 3 sides (north, east and south) are fully exposed. The west wall is partially exposed and has minimal protection because about 75% of it faces an light well.

They will be installing a false ceiling, about 6-8 inches below the existing ceiling. They've already installed a lot of tubing for the radiators (it does get cold in the winter) electricity, etc, on the old ceiling so I don't think we can install insulation up there.

My question is this: Is there any cooling benefit (or any other benefit) for installing 1, 2 or 3 slim exhaust fans to extract hot air from the space between the false ceiling and the old ceiling on hot days? The room below this false ceiling is about 17 feet by 35 feet, and it has the east-facing wall. It gets steady sun from about 11am until sundown. What made me think about this is the attic fans from my childhood.

I should add that the exhaust fans would have to be lateral - we cannot punch through the roof. So I was thinking slim fans - a few of them.

Anyway, I am grateful for any advice. Thanks in advance!

Gary

Asked by Gary Oliver
Posted Sun, 07/20/2014 - 15:40
Edited Sun, 07/20/2014 - 16:37

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2 Answers

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Gary,
It sounds as if you have just remodeled a penthouse apartment in Barcelona, Spain, and that the contractors forgot to install insulation. That's a sad story. Does that mean that the exterior walls and the ceiling of your apartment have no insulation at all?

According to Wikipedia, "In the coldest month – January – typically the temperature [in Barcelona] ranges from 46 to 63°F during the day and 36 to 50°F at night. In the warmest month – August – the typically temperature ranges from 77 to 88°F during the day and about 68°F at night. Large fluctuations in temperature are rare."

So the climate is fairly mild. Still, it would have been better if your contractors had installed some insulation -- especially if they installed hydronic heating and cooling tubes in your ceiling. Because of your contractors' error, your heating and cooling bills will be higher than they should have been.

There is no advantage to installing exhaust fans between your dropped ceiling and the ceiling above the dropped ceiling. If you want to install a few ceiling fans, however (Casablanca-style ceiling fans that blow air downward from the ceiling to cool your skin), you might be able to feel comfortable in your apartment without running your air conditioner. If you manage to keep your air conditioner turned off, you can save money on your energy bill.

For more information on these issues, see:

Fans in the Attic: Do They Help or Do They Hurt?

Using Ceiling Fans To Keep Cool Without AC

Answered by Martin Holladay, GBA Advisor
Posted Mon, 07/21/2014 - 07:30
Edited Mon, 07/21/2014 - 07:32.

2.
Helpful? 0

Thank you Martin for the information and link.

I may have been mistaken about the insulation. I didn't realize that some drywall has an 'insulation layer'. What I saw was drywall directly affixed to the old plaster walls that directly cover the brick, which is the exterior wall. So there may be some insulation - I have to get a piece of the drywall to verify. It may not be the best but I suppose that it is better than nothing. It seems that there should be some space between the old plaster and new drywall, but I will have to study some to know for sure. Things certainly have changed a lot since I was last involved with insulation, about 20 years ago.

That drywall combined with the false ceiling is/will be the insulation. Given that it is a somewhat mild climate, it should be fine. My objective was to minimize energy use - not so much because of the cost, but because for me, it is a personal 'moral issue.'

I've spent a few months in the place in summer and a few months in winter before the remodel. Even without the insulation it is pretty comfortable given that we have 50+ year old windows and doors that leak air and water. The place is easy (but a bit expensive) to heat in the winter. So the drywall insulation, combined with new windows and doors, all thermal efficient, we should see some improvements. We have two ceiling fans going in. The place has never been air conditioned, but we added two units (one for each zone - living/sleeping) as we will have visitors who are elderly and can't tolerate heat and humidity.

Anyway, thanks again. Cheers! Gary

Answered by Gary Oliver
Posted Mon, 07/21/2014 - 10:50

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