How to ventilate upper floors (no attic)?

10 years ago

Hi, I hope someone can help me here. I live in Europe in a concrete construction 2 story townhouse (attached on both sides to adjoining townhouses, so we only have windows on N/S exposures). There is no attic, rather a flat rooftop deck above the second floor. The second floor gets extremely hot as the day goes on and all the heat rises and gets trapped. I keep all the windows open at night when there is a gorgeous cool breeze, but the cool air barely gets in and only by morning has the heat finally dissipated. I have tried asking local contractors about some type of ventilation/exhaust fan for the second floor, but either due to a language barrier, or different methods of construction here, no one has any idea what I am talking about. Growing up in the US I remember having an attic fan that sucked up all the heat and ventilated it outside, but is there such a solution for a home without an attic and with concrete walls?

Comments (5)

mike_home
10 years ago
I grew up on the second floor of a brick house under a flat roof. I know how hot it can get.

Put a fan in the window and have it exhaust to the outside. It will help draw cool air from the other open windows. Any type of box fan will work as long as it doesn't fall out the window.
ionized_gw
10 years ago
Are you in a very dry, sunny zone or cloudy and wet? Either way, you seem to be getting lots of re-radiation of heat from your concrete ceiling. What color is your roof coating, dark or light and reflective? You might want to make some changes when it comes time to revise the roofing material. Reflective roofs absorb less heat, but they also give it up slower.

Ventilation by drawing air out alone might suck relatively warm air up from the lower level. This enhances the natural stack effect with open windows on the upper and lower floors. This is an efficient way to cool from an energy use standpoint, but will delay cooling of the upper floor. To get the quickest cooling upstairs when the outdoor temp is good, you should probably have a blower for intake and one for exhaust. This is unless you can effectively close off the upper level from the lower.

The only way to install these other than in windows will be to knock holes in your walls or roof.
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energy_rater_la
10 years ago
as a child we had a big fan that my Dad would
install on a centrally located window. he would
install it to exhaust out. we would sleep with
the windows open & the fan would cause the
outdoor air to be drawn inside.
it was wonderful..esp with wisteria outside
my bedroom window.

now I know that this big fan was originally
an attic fan adapted to fit on outside of window.
because the fan was so large it really
moved some air, much more so than a
regular box fan.

would something like this work for your
second story??

best of luck.
fooglie1
Original Author
10 years ago
Thanks for the replies. Yes, we live in a dry, hot, sunny location. I've looked for window fans but haven't found any in local stores. Part of the problem is that the windows in my house are not double hung windows, they are slider windows, so even with the window open I don't have a wide space to set up a window fan (although maybe I could put them in vertically?)
I am willing to invest into installing something permanent on the rooftop but don't know what to look for. Are turbine vents/whirlybirds going to help me? Can they be installed on a flat concrete roof?
ionized_gw
10 years ago
What is the upstairs layout? Is there a central hallway? If so, would you be able and willing to leave the doors open to the bedroom(s) so air can be drawn into all the room upstairs via their windows?

A pedestal fan next to the windows might help, but it will be the least efficient of all your options.

A modern version of your old whole-house fan would work, but you would have to build a new roof over it. Is the climate mild enough that you don't need much heat and you don't cool? If so, you don't need much air sealing. These fans are designed to seal up well when not in use.

Use care to prevent back-drafting of combustion appliances when using whole-house vent fans.

Here is a link that might be useful: whole house fans and other vent devices